The electron is so round that it’s ruling out potential new particles(quantamagazine.org)
quantamagazine.org
The electron is so round that it’s ruling out potential new particles
https://www.quantamagazine.org/the-electron-is-so-round-that-its-ruling-out-new-particles-20230410/
152 comments
Average Earth diameter = 2·6371 km ([1]). Size of glucose molecule ≈ 9 Å ([2]). Ratio = 7.06·10¹⁷.
[1] https://en.wikipedia.org/wiki/Earth_radius
[2] https://sphweb.bumc.bu.edu/otlt/mph-modules/ph/ph709_basicce...
[1] https://en.wikipedia.org/wiki/Earth_radius
[2] https://sphweb.bumc.bu.edu/otlt/mph-modules/ph/ph709_basicce...
electron size: 10^-14
planck length: 10^-35
10^-14 * 10^17 = 10^-31
(in case somebody wondered just as I did)
planck length: 10^-35
10^-14 * 10^17 = 10^-31
(in case somebody wondered just as I did)
Not even close. The diameter of the electron is under 10^-18 meters -- that's a sort of experimental upper bound derived from collision experiments -- but it may well be much smaller than that. Some estimates for the diameter of the electron approach the Planck length -- and some, which are no less credible, are well under the Planck length, e.g. at 10^-80m.
In physics, the electron is usually described as a point with no size at all. Thus, for practical intents and purposes, it exists but is infinitely small. (Which sort of reflects the notion that human physics is an idealization of the natural world.)
The Planck length isn't a hard physical limit for size. It's where direct measurement starts running into insurmountable barriers.
In physics, the electron is usually described as a point with no size at all. Thus, for practical intents and purposes, it exists but is infinitely small. (Which sort of reflects the notion that human physics is an idealization of the natural world.)
The Planck length isn't a hard physical limit for size. It's where direct measurement starts running into insurmountable barriers.
Well, 1E-18 / 1E17 is 1E-35, interestingly enough.
> 10^-14 * 10^17 = 10^-31
It’s actually 10^3
Typo: you forgot the "-" before the 17 in 10^17
10^-14 / 10^17.
Or 10^-14 * 10^-17.
Minor nit to an interesting parent.
Or 10^-14 * 10^-17.
Minor nit to an interesting parent.
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But they said they could detect a bump on the *North Pole* the size of a sugar molecule, so the diameter at the poles is relevant. Also, maybe "sugar molecule" means sucrose, not glucose.
It reminds me of Aristotelian physics’ perfect ætherial heavenly bodies. Ironinic they were on the terrestrial sphere in the end.
Yeah how do they manage to get that kind of accuracy. Mind boggling.
Statistics, right? It is not "one" measurement?
That's precision, not accuracy.
hang on - what?
Yes it is precise ... to 17 decimal places or whatever. But it is also I believe accurate? I mean are they wrong and the electron is as bumpy as my chin on a weekend?
Yes it is precise ... to 17 decimal places or whatever. But it is also I believe accurate? I mean are they wrong and the electron is as bumpy as my chin on a weekend?
It's not that the experiment is not accurate, "accuracy" is simply not the aspect of the measurement being discussed. The sentence "That's precision, not accuracy." should be read to mean "we are discussing precision, we are not discussing accuracy" rather than "it's precise, but inaccurate".
But the thing being concluded is that it's not very bumpy, and for that conclusion to hold water the data needs to be both accurate and precise within some very small bound. Spitting out precise measures of electron bumpiness isn't very hard without that accuracy. Right this second I used the "gut feeling" measurement device to conclude that the electron is round within 1024 bits of precision, and yet the authors have a publication and I don't. Is their conclusion over-blown?
Say I devised a test of the smoothness of steel ball bearings. Maybe it'd be something like rolling the bearing around on a soft substrate and then checking the substrate for scratches. That test would be precise (I'd know the maximum bound on the size of imperfections in the bearing) but not accurate (it wouldn't tell me anything about the absolute radius of the bearing or the location of the imperfections).
The point is, with the information given, we haven't been told anything about the accuracy of the test. Maybe it is. Maybe it isn't. That's just blank information. We've only been told the precision.
The point is, with the information given, we haven't been told anything about the accuracy of the test. Maybe it is. Maybe it isn't. That's just blank information. We've only been told the precision.
I don't think so. They're not measuring the radius to precision 10^-31 cm. They're measuring the differences in radius against zero, and they know the value of zero to infinite precision.
Sure, but it's precisely that difference which they claim to be measuring. Why does it matter that they don't also know some other value (the radius) to high accuracy? It's kind of like how a balance can measure the difference in force to high accuracy (and precision), but that doesn't mean we know anywhere near that much about the masses on the balance, and...it doesn't have to; you can just state that you know some delta accurately and not have to explain why that means some auxiliary measurement is probably precise.
When they say "they could detect a bump on the North Pole the height of a single sugar molecule" is not about the accuracy of the measurement?
If my measurement device always measures 42 it may by hyper-precise - but it won't helping me to detect a bump on the North Pole the height of a single sugar molecule nor anything else.
If my measurement device always measures 42 it may by hyper-precise - but it won't helping me to detect a bump on the North Pole the height of a single sugar molecule nor anything else.
But I feel like in this context, we're discussing both.
I can say Pi = 3 and be accurate but not precise.
I can say Pi = 3.0000004 and be precise but not accurate.
But that's not where the confusion comes from. It comes from measuring equipment.
Example, if I have a scale that is sensitive enough to give several decimals of precision, it is very difficult to calibrate it so it is accurate.
Anyone who owns a gram scale knows you basically have to recalibrate it after every measurement. It will gladly give you many decimals of precision that is just wrong.
I can say Pi = 3.0000004 and be precise but not accurate.
But that's not where the confusion comes from. It comes from measuring equipment.
Example, if I have a scale that is sensitive enough to give several decimals of precision, it is very difficult to calibrate it so it is accurate.
Anyone who owns a gram scale knows you basically have to recalibrate it after every measurement. It will gladly give you many decimals of precision that is just wrong.
On the subject of scales calibration and really small wights:
Veritasium - How To Measure The Tiniest Forces In The Universe https://youtu.be/pXoZQsZP2PY (it gets into measuring piconewtons and femtonetwons)
Veritasium - How To Measure The Tiniest Forces In The Universe https://youtu.be/pXoZQsZP2PY (it gets into measuring piconewtons and femtonetwons)
And for today's rant, you can also say Pi = 3 and be precise. Significant figures are a common shorthand for in-band signaling of error, but they're not the only tool and are really only useful insofar as they're pretty easy to do mental math with and relatively well known.
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Precision and accuracy are slightly different mathematical concepts, as demonstrated by this image [0]:
[0]: https://wp.stolaf.edu/it/files/2017/06/precsionvsaccuracy_cr...
[0]: https://wp.stolaf.edu/it/files/2017/06/precsionvsaccuracy_cr...
To be honest accuracy Vs precision has always kind of makes sense to be but also not.
If something is extremely accurate, it will also be extremely precise by necessity, it seems like? The difference between low precision but high & low accuracies is that points are closer to center. If you keep getting closer to center, more accurate, don't you necessarily get more precise too?
Precise has always felt like a shitty alternate of accuracy. It's accuracy but with drift, accuracy to not the right place. But if you're accurate, you're both.
Am I missing something? And, here specifically, if this is a case of very high precision but lower accuracy, can someone explain what the drift from center is about? Isn't a radius a radius? Where is the drift off center in these measures?
If something is extremely accurate, it will also be extremely precise by necessity, it seems like? The difference between low precision but high & low accuracies is that points are closer to center. If you keep getting closer to center, more accurate, don't you necessarily get more precise too?
Precise has always felt like a shitty alternate of accuracy. It's accuracy but with drift, accuracy to not the right place. But if you're accurate, you're both.
Am I missing something? And, here specifically, if this is a case of very high precision but lower accuracy, can someone explain what the drift from center is about? Isn't a radius a radius? Where is the drift off center in these measures?
I don't like the lower left quadrant of that diagram, because it's not clear that it's not centered on the target. It would have been more clear if the cluster was smaller so it could be moved to not be centered on the target.
Accurate but imprecise means we can throw more and more shells down range and eventually hit the target. Inaccurate and imprecise means we may never hit the target. Inaccurate but precise also means we may never hit the target, but if we could introduce a second, different measurement that was accurate, we could compensate.
Accurate but imprecise means we can throw more and more shells down range and eventually hit the target. Inaccurate and imprecise means we may never hit the target. Inaccurate but precise also means we may never hit the target, but if we could introduce a second, different measurement that was accurate, we could compensate.
Something is accurate in this sense if the "true" value (ignoring any philosophical implications thereof) is contained in the error bounds of the measurement. What you're noting is that a high accuracy measurement will, upon application of statistics, allow you to derive a new measure which is both high-accuracy and high-precision, regardless of the low precision of any inputs. Not all things being described with accuracy and precision are the result of processing large amounts of data though.
I wrote about precision here if you are interested. You first need precision before you can start even talking about accuracy (otherwise there is no "center").
https://alexpetralia.com/2023/01/31/what-does-it-mean-for-da...
https://alexpetralia.com/2023/01/31/what-does-it-mean-for-da...
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I saw a Greek food stall in town a couple of years back with the statement "Food delivered with mathematical accuracy" which just bugged the hell out of me lol.
No. Precision and Accuracy have very specific definitions in the world of science and engineering.
https://en.m.wikipedia.org/wiki/Accuracy_and_precision
So, when one uses statistics to rule out deviations below 1E-17 radians (or whatever), you're all saying that's not accuracy, it's precision.
I'm also surprised, since IIRC precision is a measure of variance from a set of measurements, and accuracy is a measure of deviation of a value from true.
The statistical aggregation to get an estimate should (I think?) increase both the accuracy of that estimate (it will converge to the true value) and it's precision (the spread of subsequent estimates with more measurements converges to zero or some noise floor).
Here we're measuring something like eccentricity, which has a value and error bars. And the claim is we have eccentricity zero with precision high enough to rule out deviations below 1E-17 radians. So yeah, precision seems to be the better of the two, but accuracy matters.
Either way, this is insanely pedantic.
I'm also surprised, since IIRC precision is a measure of variance from a set of measurements, and accuracy is a measure of deviation of a value from true.
The statistical aggregation to get an estimate should (I think?) increase both the accuracy of that estimate (it will converge to the true value) and it's precision (the spread of subsequent estimates with more measurements converges to zero or some noise floor).
Here we're measuring something like eccentricity, which has a value and error bars. And the claim is we have eccentricity zero with precision high enough to rule out deviations below 1E-17 radians. So yeah, precision seems to be the better of the two, but accuracy matters.
Either way, this is insanely pedantic.
Consider the case where there’s a configuration error — say, a cable not properly seated.
You can have results that are highly precise, but due to cable issue, not baselined correctly and therefore systemically inaccurate. Eg, faster than light neutrinos.
https://en.m.wikipedia.org/wiki/Faster-than-light_neutrino_a...
I think people get confused because they forget that systemic bias can impact precise measurements: if your system is wrong, you’ll precisely come to the wrong conclusion.
You can have results that are highly precise, but due to cable issue, not baselined correctly and therefore systemically inaccurate. Eg, faster than light neutrinos.
https://en.m.wikipedia.org/wiki/Faster-than-light_neutrino_a...
I think people get confused because they forget that systemic bias can impact precise measurements: if your system is wrong, you’ll precisely come to the wrong conclusion.
You're talking about a specific measurement, not a derived measurement from statistical analysis, though, right? Is there an instrument? If not, we're not talking about precision or accuracy, we're talking about variance about the mean, and the mean is assumed to move towards true.
In that case, the assumption is zero mean error b/c systemic errors average out, so the accuracy is the mean minus true, and the precision is established by the Cramer rao lower bound, and estimated my the posterior variance about the mean. My point is that calling it anything but a statistical certainty (e.g. confidence interval) is just jargon.
In that case, the assumption is zero mean error b/c systemic errors average out, so the accuracy is the mean minus true, and the precision is established by the Cramer rao lower bound, and estimated my the posterior variance about the mean. My point is that calling it anything but a statistical certainty (e.g. confidence interval) is just jargon.
You can’t derive the correct value if all your measurements are (eg) +1ns due to inaccurate path length in your model.
Your collection of measurements will converge, just as if you had built the device you intended to — but they’ll converge to the wrong value, because you’re measuring the time incorrectly every measurement, and so averaging that out doesn’t do anything.
Your test is precise but inaccurate.
The whole context of this is about a specific instrument measuring electron properties — or in my example, timing neutrino flights. So… yes, we’re talking about precision and accuracy.
Your collection of measurements will converge, just as if you had built the device you intended to — but they’ll converge to the wrong value, because you’re measuring the time incorrectly every measurement, and so averaging that out doesn’t do anything.
Your test is precise but inaccurate.
The whole context of this is about a specific instrument measuring electron properties — or in my example, timing neutrino flights. So… yes, we’re talking about precision and accuracy.
You're explaining accuracy vs precision, which I get.
The answer actually was: Yes, there's only one instrument. So yes, you can't average out systemic biases. So yes, I guess you can say something about
"We measure eccentricity zero with 1 part in 1E+17, which is really precise, but you'll just have to trust us it's also accurate."
Anyway, we know what everyone meant.
The answer actually was: Yes, there's only one instrument. So yes, you can't average out systemic biases. So yes, I guess you can say something about
"We measure eccentricity zero with 1 part in 1E+17, which is really precise, but you'll just have to trust us it's also accurate."
Anyway, we know what everyone meant.
What's the point in measuring it with high precision if it's not accurate?
Precision is about how tightly clustered your measurements are.
Accuracy is about how well those measurements reflect reality.
If you are just trying to see how smooth a ball is by measuring the diameter many times at different points, then a high precision can tell you that, even if the actual diameter is different to your measurement.
You don't care about the actual diameter, you care about the variation in it.
Accuracy is about how well those measurements reflect reality.
If you are just trying to see how smooth a ball is by measuring the diameter many times at different points, then a high precision can tell you that, even if the actual diameter is different to your measurement.
You don't care about the actual diameter, you care about the variation in it.
Sometimes you're interested in delta of change, not absolute value itself. So absolute accuracy might be "wrong" but as long as it is consistently wrong (within duration of measurements you need to make) it doesn't matter all that much.
My understanding is that a highly spherical electron implies the electron has no sub component parts. Knowing the exact radius of the electron doesn't change that, it's knowing there is no variance in the radius that is important.
And again, I was only commenting on what was being commented on here. I don't know if the experiment was also highly accurate. But people here were commenting on the precision and calling it accuracy.
And again, I was only commenting on what was being commented on here. I don't know if the experiment was also highly accurate. But people here were commenting on the precision and calling it accuracy.
My (mis-?) understanding of the Central Limit Theorem is that the average of >30 measurements increases the accuracy. https://en.wikipedia.org/wiki/Central_limit_theorem
No, that's increasing the precision, not accuracy. Many imprecise measurements can be averaged to a more precise measurement.
Say we had a perfect ruler to measure the length of something. It's absolutely precise and accurate. All measurements from it return the exact, same value, and preternaturally we know it's the "correct" value.
Now say some bandit comes in while we're not looking and adds a small chunck of diamond to the end of the ruler without telling us. Our ruler is still precise, but no longer accurate. If we take many measurements with it, they always come back with the same value. Averaging those values does not improve the accuracy at all.
Alternatively, say the bandit starts randomly changing the temperature of the room we are in. Thermal expansion is constantly changing the length of the ruler. The average length of the ruler is still the same, so it's still accurate, but it's no longer precise. We could average the measurements we take with it and get a more precise measurement.
What the central limit theorem says is that the averages of our measurements will be normally distributed, even if the change in temperature is not.
Say we had a perfect ruler to measure the length of something. It's absolutely precise and accurate. All measurements from it return the exact, same value, and preternaturally we know it's the "correct" value.
Now say some bandit comes in while we're not looking and adds a small chunck of diamond to the end of the ruler without telling us. Our ruler is still precise, but no longer accurate. If we take many measurements with it, they always come back with the same value. Averaging those values does not improve the accuracy at all.
Alternatively, say the bandit starts randomly changing the temperature of the room we are in. Thermal expansion is constantly changing the length of the ruler. The average length of the ruler is still the same, so it's still accurate, but it's no longer precise. We could average the measurements we take with it and get a more precise measurement.
What the central limit theorem says is that the averages of our measurements will be normally distributed, even if the change in temperature is not.
This really doesn't make much sense in the context of the measurement which is bounding the value(0) with 90% confidence[1].
1. https://arxiv.org/pdf/2212.11841.pdf
1. https://arxiv.org/pdf/2212.11841.pdf
I think op is talking about bias vs variance. In some cases we have a bias variance trade off.
Yep, and I'm talking about hypothesis testing which is what's being done in the paper.
Hypothesis testing cannot rule out systemic bias errors present in both control and treatment populations.
Are you pontificating about systemic bias or is this a specific critique of the techniques used to simultaneously detect the upper and lower doublets in a single shot of the experiment?
I am trying to explain to you what moron4hire is talking about. Hypothesis testing doesn't magically fix the issue he is discussing, as hypothesis testing works by collecting many imprecise measurements to average it out to a more precise level.
That's all true. I am biased because I am responsible for keeping hundreds of devices calibrated, and keeping a lab within 2C of 23C. The CLT implies that the sample mean is more likely to be close to the true population mean as the sample size increases. Not the same as more accurate. Shame on me!
The number of people in this thread not understanding the difference between bias and variance errors is too much.
http://scott.fortmann-roe.com/docs/BiasVariance.html
http://scott.fortmann-roe.com/docs/BiasVariance.html
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I struggle with understanding that size comparison, given that the size of the electron is unknown: we only have a maximum size that's based on the accuracy of the measurements, no lower bound.
I think it's supposed to relate the variation of the shape of electric field around electron not the size of the electron which is a pointlike particle.
I can’t even fathom how such a thing can possibly exist
The next sentence after the first part you quoted: "The latest results are in: The electron is rounder than that."
Which would be great if the Earth was actually perfectly round, but we've known for over three centuries that it's not. I'm sure the science the article is reporting on is fine, but it definitely sounds like the author of the article is out of their depth.
Which would be great if the Earth was actually perfectly round, but we've known for over three centuries that it's not. I'm sure the science the article is reporting on is fine, but it definitely sounds like the author of the article is out of their depth.
I know you're getting at the whole "oblate spheroid" shape thing, but I'm pretty sure people have known it wasn't perfectly round for way longer than that. You only need to look out a window to see hills and mountains after all (unless you live in the Netherlands ofc).
Fun fact: the actual shape of the Earth is neither a sphere nor an ellipsoid but a "geoid", literally something "shaped like the earth".
Fun fact: the actual shape of the Earth is neither a sphere nor an ellipsoid but a "geoid", literally something "shaped like the earth".
It's trying to put a size comparison so that our human minds can picture the scale. Earth is just a placeholder in this example. The author is inviting you to picture the the size of the planet. They could've just written the sizes in terms of 10^x , however that is not as human-friendly to envison.
There is no need to be unkind towards the author here, maybe your point is that they could have done a better job at presenting the scale for the reader? How would you write it?
There is no need to be unkind towards the author here, maybe your point is that they could have done a better job at presenting the scale for the reader? How would you write it?
That’s not what it’s saying. It’s saying, if you blew up the electron to the size of the earth, and sprinkled a sugar grain on it, then the electron is rounder than that.
Not a sugar grain, a sugar molecule.
Definitely should have used spherical cows.
I do not understand this.
May someone help me with an ELI16?
An electron is a cloud that is contained with a perfectly round sphere. Does cloud mean a thing that contains a particle that travels very fast in a perfect sphere?
What does cloud entail in this instance? If we have determined that an electronic cannot be made up of other particles then there should only be one particle in the cloud? Or is the particle a gas / cloud?
I thought that the general consensus was that the precise location of an electron was impossible (?) to fully predict? If you can't predict where an electron is with a high degree of certainty How can you measure it ?
This might be outdated, or just my brain pulling tricks on me again.
An electron is a cloud that is contained with a perfectly round sphere. Does cloud mean a thing that contains a particle that travels very fast in a perfect sphere?
What does cloud entail in this instance? If we have determined that an electronic cannot be made up of other particles then there should only be one particle in the cloud? Or is the particle a gas / cloud?
I thought that the general consensus was that the precise location of an electron was impossible (?) to fully predict? If you can't predict where an electron is with a high degree of certainty How can you measure it ?
This might be outdated, or just my brain pulling tricks on me again.
The old "is" strikes again. An electron is definitely not a cloud, nor a particle nor a wave, we don't know what the hell it is and stopped trying to describe it in those terms many years ago. Instead, we limit ourselves to trying to come up with models that accurately predict how they behave, and call the models useful when they predict the right answers to experiments. "All models are wrong but some are useful", as the saying goes.
Like all subatomic particles, electrons don't seem to have a discrete location; when we try to measure their location, we get different results each time, as you said. However, these apparently-random results follow a predictable pattern, so we describe it using an equation predicting where it is most likely to be found (the Schrodinger wave equation). For electrons in some stable states, that area is roughly spherical, meaning that there is some point where it is most likely to be found, a fuzzy area near that point where it is fairly likely to be found, and a distance from that point past which it is very unlikely to be found. We can therefore model the electron as being a tiny discrete thing that whizzes around in a roughly spherical area, which is the "cloud" in this article.
All that "can be modeled as" stuff is unwieldy, so people say the electron "is" a spherical cloud when they mean that modeling it as a spherical cloud is useful for understanding the matter at hand. What this article is describing is an attempt to measure whether that spherical region is perfectly spherical. If it weren't - meaning, if the electron was slightly more likely to be found on one side of the sphere than the other, then it would have an electrical dipole moment, which is what they were trying to find.
Like all subatomic particles, electrons don't seem to have a discrete location; when we try to measure their location, we get different results each time, as you said. However, these apparently-random results follow a predictable pattern, so we describe it using an equation predicting where it is most likely to be found (the Schrodinger wave equation). For electrons in some stable states, that area is roughly spherical, meaning that there is some point where it is most likely to be found, a fuzzy area near that point where it is fairly likely to be found, and a distance from that point past which it is very unlikely to be found. We can therefore model the electron as being a tiny discrete thing that whizzes around in a roughly spherical area, which is the "cloud" in this article.
All that "can be modeled as" stuff is unwieldy, so people say the electron "is" a spherical cloud when they mean that modeling it as a spherical cloud is useful for understanding the matter at hand. What this article is describing is an attempt to measure whether that spherical region is perfectly spherical. If it weren't - meaning, if the electron was slightly more likely to be found on one side of the sphere than the other, then it would have an electrical dipole moment, which is what they were trying to find.
Fake edit: this is why it's helpful when discussing quantum mechanics to banish "is" from your vocabulary. For example, the debate over whether an electron "is" a particle or "is" a wave is much more tractable when you switch to debating whether it behaves like a particle or a wave in some situation. In college, I found this very similar to how it is useful when learning relativity to avoid the word "simultaneously".
In another thread I said an electron is an excitation of a quantum field. Is that a mistake as well?
I don’t think quantum stuff will ever make sense to me…
I don’t think quantum stuff will ever make sense to me…
It's only a mistake if you take it too literally and forget it's a model, e.g. "I measured the electron to have a mass, but I can't see how an excitation in a field would have mass so I guess I must've measured wrong."
> it’s a model
Maybe it is and maybe it isn’t. We don’t know what is actually happening. Max Tegmark makes a pretty good case for it actually being mathematics.
Maybe it is and maybe it isn’t. We don’t know what is actually happening. Max Tegmark makes a pretty good case for it actually being mathematics.
Yes, if you view Time, Space, Intelligence and Consciousness as emergent, things make a lot more sense.
This upsets people because it implies that the most fundamental parts of their existence are not "real", but to your point it is very helpful to approach them as if they are not "real" regardless of what is actually fundamental to reality.
This upsets people because it implies that the most fundamental parts of their existence are not "real", but to your point it is very helpful to approach them as if they are not "real" regardless of what is actually fundamental to reality.
This makes absolutely zero sense. I also have no idea why you replied to the GP who was making interesting points and spending a lot of brain cycles to do so. Maybe it upsets people because it is - apologies - interesting sounding bullshit?
It's certainly understandable that the concepts presented here may seem perplexing or even nonsensical. However, it's important to consider that modern physics, as we know it, is riddled with conundrums and enigmatic phenomena that continue to challenge our understanding of the universe. From the pursuit of a unified theory to grappling with the implications of quantum gravity and entanglement, it's clear that our perception of reality is not as straightforward as we might initially assume.
In fact, it could be argued that this inherent complexity is precisely what makes these ideas so fascinating. Just as an entrepreneur might embrace uncertainty and forge new paths in uncharted territory, the scientists delving into these perplexing aspects of reality are pushing the boundaries of our collective knowledge. And in doing so, they may uncover new insights that will fundamentally reshape our understanding of the universe and our place within it.
So while it's natural to feel skeptical or even incredulous when confronted with such seemingly "outlandish" ideas, I encourage you to remain open-minded and curious. After all, the history of scientific progress is replete with instances where established ideas were overturned by new discoveries, often spurred by those willing to entertain the seemingly impossible.
In fact, it could be argued that this inherent complexity is precisely what makes these ideas so fascinating. Just as an entrepreneur might embrace uncertainty and forge new paths in uncharted territory, the scientists delving into these perplexing aspects of reality are pushing the boundaries of our collective knowledge. And in doing so, they may uncover new insights that will fundamentally reshape our understanding of the universe and our place within it.
So while it's natural to feel skeptical or even incredulous when confronted with such seemingly "outlandish" ideas, I encourage you to remain open-minded and curious. After all, the history of scientific progress is replete with instances where established ideas were overturned by new discoveries, often spurred by those willing to entertain the seemingly impossible.
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For what is worth, I agree all those things are emergent (how else would they come to be?), but also felt it was non sequitur and was put off by the assertion it was "too hot to handle."
I think GP was objecting less to the substance of what you said than that it's non sequitur-ness, if I had to guess they viewed it at disrespectful because the original commenter had put a lot of effort into creating a thread on a certain topic and they perceived you were hijacking it to talk about something tangential. The connection between these topics may be clearer to you than it is to us.
While I do know of some people who refuse to accept any form of fundamental relativism or uncertainty, I honestly think they're pretty rare, and it's unnecessarily confrontational to start a conversation asserting your views are "too hot to handle". It's sort of like asserting that some people are too dumb to agree with you - it's getting off on the wrong foot, and more likely to incite an argument than a discussion.
I think GP was objecting less to the substance of what you said than that it's non sequitur-ness, if I had to guess they viewed it at disrespectful because the original commenter had put a lot of effort into creating a thread on a certain topic and they perceived you were hijacking it to talk about something tangential. The connection between these topics may be clearer to you than it is to us.
While I do know of some people who refuse to accept any form of fundamental relativism or uncertainty, I honestly think they're pretty rare, and it's unnecessarily confrontational to start a conversation asserting your views are "too hot to handle". It's sort of like asserting that some people are too dumb to agree with you - it's getting off on the wrong foot, and more likely to incite an argument than a discussion.
I'm not sure what you're talking about, but it's not very related to my point about "is", which was that describing things in "[noun] is [adjective]" terms carries the implicit assumption that the universe is made up of things have objective qualities, which is a useful model most all the time but still a model, and hence ultimately wrong.
For what it's worth, I think the connection is, once you surrender "is", you accept a world that is stranger and fuzzier than may be comfortable - a world where the question, "what is an electron?" may actually not have an answer.
Yeah, I am not used to seeing the term “cloud” for a single electron.
Is that a common term in physics for a single electron? I am very much used to seeing that phrase as the probability space for electrons in orbitals in an atom.
https://en.wikipedia.org/wiki/Atomic_orbital
In this article I take it to mean “any point particle has a non-zero physical radius, but because quantum mechanics shows everything has a measure of uncertainty, the possibility of the charge within that non-zero space is an amorphous cloud”. But still a weird lexical overlap with the high school physics electron cloud meaning of things.
Is that a common term in physics for a single electron? I am very much used to seeing that phrase as the probability space for electrons in orbitals in an atom.
https://en.wikipedia.org/wiki/Atomic_orbital
In this article I take it to mean “any point particle has a non-zero physical radius, but because quantum mechanics shows everything has a measure of uncertainty, the possibility of the charge within that non-zero space is an amorphous cloud”. But still a weird lexical overlap with the high school physics electron cloud meaning of things.
Consider the case where the atom in question is hydrogen, with just one electron orbiting it.
I would still think the word "cloud" would be used?
I would still think the word "cloud" would be used?
You are not to blame for not understanding this, it's just that the analogy for the electric dipole moment coming from a non-spherical 'shape' of the electron is extremely bad. Moreover it's missing the most important reason why we search for EDMs, because the existence of one in an elementary particle would indicate the violation of the time-reversal symmetry (T), which assuming CPT conservation [1] leads to CP violation (Charge conjugation and parity symmetries). CP violation [2] is needed to explain the matter-antimatter asymmetry of the Universe.
A more proper way, in my opinion, to reason about an electric dipole moment is to think in terms of Feynman diagrams. An EDM (or any dipole moment for that matter) is an interaction of the electron with an electromagnetic field, so interaction between an electron and a photon. The most simple such interaction you can imagine is an electron flying in, at one point it absorbs a photon and flies out - that would be the magnetic dipole moment. You can go more complex though - electron flying in, at one point it emits a photon, then the electron interacts with the EM field (absorbing a photon) and then it reabsorbs the photon it has emitted previously. (Note that these analogies are again not perfect as for elementary particles time and space are not the same as in the macro world). Now, it can get even more complicated: If you have an electron it's not really a 100% pure electron. There is always some chance that it transforms for a short time into a quark or neutrino or whatever you can imagine.
When you analyze all such scenarios (electron going into something else, interacting with the EM field and then going back to an electron) some violate CP symmetry, and those contribute to the electric dipole moment. We use that name (dipole moment) as the final result is as if the electron was a ball with some separation between the negative and positive charges and placed into an electric field it experiences some torque. The analogy misses the most important part though, as if it was such a polarized 'ball' it would not violate CP symmetry.
Within the Standard Model the only source of CP violating interactions come from the weak interaction (CKM matrix). These have a very small contribution as the weak interaction is, as the name suggests, very weak. That's why the Standard Model predicts very tiny electric dipole moments. When we are searching for EDMs we are in fact searching for such rare transformations through some new undiscovered particle that violate CP symmetry. If we detect some non-zero EDM that would mean that there is some interaction that is not included in the standard model that violates CP, not that the electron is not a round sphere or a sphere with a bump.
[1] - https://en.wikipedia.org/wiki/CPT_symmetry [2] - https://en.wikipedia.org/wiki/CP_violation
A more proper way, in my opinion, to reason about an electric dipole moment is to think in terms of Feynman diagrams. An EDM (or any dipole moment for that matter) is an interaction of the electron with an electromagnetic field, so interaction between an electron and a photon. The most simple such interaction you can imagine is an electron flying in, at one point it absorbs a photon and flies out - that would be the magnetic dipole moment. You can go more complex though - electron flying in, at one point it emits a photon, then the electron interacts with the EM field (absorbing a photon) and then it reabsorbs the photon it has emitted previously. (Note that these analogies are again not perfect as for elementary particles time and space are not the same as in the macro world). Now, it can get even more complicated: If you have an electron it's not really a 100% pure electron. There is always some chance that it transforms for a short time into a quark or neutrino or whatever you can imagine.
When you analyze all such scenarios (electron going into something else, interacting with the EM field and then going back to an electron) some violate CP symmetry, and those contribute to the electric dipole moment. We use that name (dipole moment) as the final result is as if the electron was a ball with some separation between the negative and positive charges and placed into an electric field it experiences some torque. The analogy misses the most important part though, as if it was such a polarized 'ball' it would not violate CP symmetry.
Within the Standard Model the only source of CP violating interactions come from the weak interaction (CKM matrix). These have a very small contribution as the weak interaction is, as the name suggests, very weak. That's why the Standard Model predicts very tiny electric dipole moments. When we are searching for EDMs we are in fact searching for such rare transformations through some new undiscovered particle that violate CP symmetry. If we detect some non-zero EDM that would mean that there is some interaction that is not included in the standard model that violates CP, not that the electron is not a round sphere or a sphere with a bump.
[1] - https://en.wikipedia.org/wiki/CPT_symmetry [2] - https://en.wikipedia.org/wiki/CP_violation
I think the measurements don't say anything about the size or how the electron is distributed in the probability distribution other than that it's spherically symmetric to a very small tolerance. It's interesting that there is another model of the electron orbit in atoms that is a spinning fluid shell of charge with an exact radius. See https://brilliantlightpower.com/theory-overview/
> I think the measurements don't say anything about the size or how the electron is distributed in the probability distribution
I fully admit i dont understand most of what I hear about particle physics anymore A lot seems non intuitive with the (dumb) model I have in my head. (That doesn't say much about tis accuracy)
If you are to make such extremely detailed measurements of anything you need to be able to observe it over time? (Though how much time varies a lot)
Presumably, a constantly moving electron whose location cannot established is a difficult thing measure?
I fully admit i dont understand most of what I hear about particle physics anymore A lot seems non intuitive with the (dumb) model I have in my head. (That doesn't say much about tis accuracy)
If you are to make such extremely detailed measurements of anything you need to be able to observe it over time? (Though how much time varies a lot)
Presumably, a constantly moving electron whose location cannot established is a difficult thing measure?
Well it depends how it is moving. Think of a spinning axle that is featureless - does it appear to move? How about a featureless disc bike wheel that is spinning? And the Mills model of the electron "orbitsphere" is a spherical fluid shell of charge that is spinning along all great circle routes. The charge distribution is not changing but the charge is spinning.
The electron has no known internal structure. As far as we know its a fundamental particle and isn't made up of other things, the way protons or neutrons are made up of quarks held together by gluons.
An electron's location is subject to all sorts of rules. The Heisenberg uncertainty principle says that the more we know about a particles momentum (mass*velocity), the less we know about its position, and vice versa. This is not a matter of the observer effect (measurement upsetting one of these values), as some people state, but something fundamental due to the wavefunction nature of matter. The location of a subatomic particle is determined by its wavefunction (Squared) - where the wavefunction is big you have a high probability of finding a particle, and where it is small you have a small probability to find a particle. the wavefunction is a probability density function - the probability of finding a given particle at a given place in a given time.
The next important idea is that subatomic particles can be considered both particles and waves, and thus have a wavelength. High momentum particles (high energy) have a short wavelength, low momentum (low energy) particles have long wavelengths. Waves are disturbances spread out in space, and we can identify the distance between two peaks (the wavelength), but then we wouldn't know anything about its position - it could be in lots of places.
To localize a wave you add together lots of waves (into a localized wavepacket) until the resulting wave gives you areas where you are likely to find a particle where those added waves overlap in crests, and areas where you are unlikely to find the particle where those added waves overlap in troughs. This is a tradeoff, though - you are still subject to the heisenberg uncertainty principle so the more you know about the location, the less you know about the momentum. Thus the electrons, which move very quickly, and are interchangeable with one another being identical to each other, appear to exist as a cloud of probabilistic locations. They aren't themselves a cloud, rather their position is always uncertain until directly measured to a high degree of certainty.
Now you may say "but we know electrons live in orbitals around atoms - how can we know that if we can't know their precise positions". This is because electrons obey the pauli exclusion principle, which states that two or more particles with half integer spin (fermions of which the electron is one, which have antisymmetric wave functions) cannot have the same set of four quantum numbers -
n (the shell number or general region for value of energy of the electron),
l (orbital angular momentum/the shape of the orbital),
m sub l (the magnetic orientation of the orbital), and
m sub s (quantum spin, which for fermions can be +/- 1/2). (the minus is what makes fermions antisymmetric)
This principle is why electrons are more likely to be found in some places around an atom described as shells, and thus why electrons exist in discrete locations around an atom and why atoms and chemistry exist. The reason for the pauli exclusion principle is also wave related - I'll link a video below:
https://www.youtube.com/watch?v=Zlp2GQ3OLeE
This was a pretty surface level explanation - we didn't even get into the dirac equation (which is where the existence of antimatter was first derived) or spinor theory! but I think its good enough to have some understanding of why the fundamental wave nature of subatomic particles leads to uncertainty in their location, which means they appear to live in a cloud around atoms.
An electron's location is subject to all sorts of rules. The Heisenberg uncertainty principle says that the more we know about a particles momentum (mass*velocity), the less we know about its position, and vice versa. This is not a matter of the observer effect (measurement upsetting one of these values), as some people state, but something fundamental due to the wavefunction nature of matter. The location of a subatomic particle is determined by its wavefunction (Squared) - where the wavefunction is big you have a high probability of finding a particle, and where it is small you have a small probability to find a particle. the wavefunction is a probability density function - the probability of finding a given particle at a given place in a given time.
The next important idea is that subatomic particles can be considered both particles and waves, and thus have a wavelength. High momentum particles (high energy) have a short wavelength, low momentum (low energy) particles have long wavelengths. Waves are disturbances spread out in space, and we can identify the distance between two peaks (the wavelength), but then we wouldn't know anything about its position - it could be in lots of places.
To localize a wave you add together lots of waves (into a localized wavepacket) until the resulting wave gives you areas where you are likely to find a particle where those added waves overlap in crests, and areas where you are unlikely to find the particle where those added waves overlap in troughs. This is a tradeoff, though - you are still subject to the heisenberg uncertainty principle so the more you know about the location, the less you know about the momentum. Thus the electrons, which move very quickly, and are interchangeable with one another being identical to each other, appear to exist as a cloud of probabilistic locations. They aren't themselves a cloud, rather their position is always uncertain until directly measured to a high degree of certainty.
Now you may say "but we know electrons live in orbitals around atoms - how can we know that if we can't know their precise positions". This is because electrons obey the pauli exclusion principle, which states that two or more particles with half integer spin (fermions of which the electron is one, which have antisymmetric wave functions) cannot have the same set of four quantum numbers -
n (the shell number or general region for value of energy of the electron),
l (orbital angular momentum/the shape of the orbital),
m sub l (the magnetic orientation of the orbital), and
m sub s (quantum spin, which for fermions can be +/- 1/2). (the minus is what makes fermions antisymmetric)
This principle is why electrons are more likely to be found in some places around an atom described as shells, and thus why electrons exist in discrete locations around an atom and why atoms and chemistry exist. The reason for the pauli exclusion principle is also wave related - I'll link a video below:
https://www.youtube.com/watch?v=Zlp2GQ3OLeE
This was a pretty surface level explanation - we didn't even get into the dirac equation (which is where the existence of antimatter was first derived) or spinor theory! but I think its good enough to have some understanding of why the fundamental wave nature of subatomic particles leads to uncertainty in their location, which means they appear to live in a cloud around atoms.
This leads me to the logical question about EDM of protons and neutrons. The electron and neutron are mentioned, but nothing for proton EDM. What's up with that?
Also apparently the EDM for the neutron has yet to be detected, despite it being a composite particle. Our sensitivity is about five orders of magnitude away from the predicted value.
https://en.m.wikipedia.org/wiki/Electron_electric_dipole_mom...
https://en.m.wikipedia.org/wiki/Neutron_electric_dipole_mome...
Also of note, here's a pEDM experiment with a 50m radius (the eEDM experiment is lab scale).
https://aip.scitation.org/doi/10.1063/1.4967465
Also apparently the EDM for the neutron has yet to be detected, despite it being a composite particle. Our sensitivity is about five orders of magnitude away from the predicted value.
https://en.m.wikipedia.org/wiki/Electron_electric_dipole_mom...
https://en.m.wikipedia.org/wiki/Neutron_electric_dipole_mome...
Also of note, here's a pEDM experiment with a 50m radius (the eEDM experiment is lab scale).
https://aip.scitation.org/doi/10.1063/1.4967465
I'm working on the search for the EDM of the muon.
Essentially it's much harder to search for the proton EDM than the neutron EDM. All EDM searches rely on a strong electric field applied to the particles. Because neutrons are neutral they are easily stored in some volume for a long time. You cannot so easily store protons because the moment you apply some E-field you start accelerating them. That's why you need to build a large storage ring with magnetic/electric focusing and so on. This brings numerous challenges that you don't have for the neutron. This, combined with the fact that we don't expect much different novel physics for the proton that won't be seen in the neutron has led to the focus on the neutron EDM, while the proton was left behind.
The usual quote is that for the proton we can reach sensitivities up to 10^-29 (around three orders of magnitude lower than the current nEDM limit), but thats only the statistical sensitivity. The systematic effects that would spoil that come much earlier and this limit is close to science fiction at this point. For example, if you have a magnetic field in the order of attotesla in the region of the storage ring it will dominate the measurement.
Would be happy to answer more edm questions :)
The usual quote is that for the proton we can reach sensitivities up to 10^-29 (around three orders of magnitude lower than the current nEDM limit), but thats only the statistical sensitivity. The systematic effects that would spoil that come much earlier and this limit is close to science fiction at this point. For example, if you have a magnetic field in the order of attotesla in the region of the storage ring it will dominate the measurement.
Would be happy to answer more edm questions :)
Thank you, this is why I love HN!
Ah, that makes sense! I thought neutrons were hard to store because they were neutral and go right through things, but I guess cold neutrons can be stored (at least until they decay into protons).
Is it expected that pEDM ~= nEDM, since they are uud and udd?
Ah, that makes sense! I thought neutrons were hard to store because they were neutral and go right through things, but I guess cold neutrons can be stored (at least until they decay into protons).
Is it expected that pEDM ~= nEDM, since they are uud and udd?
I cannot find the citation right now, but the p and n EDMs are expected to be close to each other ~1e-32 e.cm. One part is that they are uud and udd and the other thing to consider is that the quarks make up only ~2% of the proton/neutron mass. Most is binding energy and a soup of virtual quarks and gluons and in that regard they are even more similar I think. I am not very familiar how theoreticians calculate the EDM of such complex particles though.
On a side note, 'ultra cold neutrons' are a super interesting type of matter. Their energy is so low that they can be stored in bottles and are transported through tubes using turbines and mechanical valves.
On a side note, 'ultra cold neutrons' are a super interesting type of matter. Their energy is so low that they can be stored in bottles and are transported through tubes using turbines and mechanical valves.
EDM experiments are sensitive to electric field strength and observation time.
For electrons, you can get much higher fields inside a molecule.
For neutrons, you either need a very cleverly designed crystal or a bottle with ultracold neutrons. The crystal lets you get huge fields and huge particle counts, but relatively short observation times. Ultracold neutrons let you have long observation times (100-300 seconds) but lower fields and much lower particle counts.
Protons are probably the hardest of the lot. They need external fields, but they're charged so you can't just bottle them. You're stuck with a holding ring, and needing to make all those v x E corrections.
For electrons, you can get much higher fields inside a molecule.
For neutrons, you either need a very cleverly designed crystal or a bottle with ultracold neutrons. The crystal lets you get huge fields and huge particle counts, but relatively short observation times. Ultracold neutrons let you have long observation times (100-300 seconds) but lower fields and much lower particle counts.
Protons are probably the hardest of the lot. They need external fields, but they're charged so you can't just bottle them. You're stuck with a holding ring, and needing to make all those v x E corrections.
Can someone explain what an electron is? I remember from my high school physics that electrons are "point-like" particles, which are "elementary" (not built out of any smaller particles). And electron clouds are like all possible or probable trajectories of how electrons move around an atom's nucleus. Or something like that, it was many years ago. Then what is a "cloud of negative charge"?
Disclaimer: I have a theoretical degree in armchair physics, not a real one.
So that's where the fun of Quantum Mechanics and uncertainty comes in. Electrons are not just point-like particles, they're sort of both particles and waves. If you nail down exactly where the electron "particle" is, then you end up with it's momentum being less defined, meaning that you're not going to be able to say anything at all about where it came from, where it's going, or how fast. Similarly if you can nail down it's momentum perfectly it won't have a definition of where it is anymore. This isn't the Observer effect, where you making the measurements changes the system, but in fact that the other related property actually ceases to have a valid definition anymore (I'm not well versed enough to say it stops existing with any confidence but that's my understanding). This leads to a situation where you end up measuring a probability density of the property of the electron, so you get a density of it being "around this point +/- some amount" and with a "momentum +/- this amount, and sort of in this direction". This means that you now have a probability density of the electron where you'll see it's effects of the negative charge and kinetic energy and those are the things that describe that "cloud of negative charge". The main effect of this that affects things is that you end up with this cloud of all the electrons around an atom and you don't ever observe the individual electrons, just the shells/clouds around the atom and how they change as energy is inserted into the system.
My layman's understanding is that essentially as you make a measurement/system/whatever where it's designed to see the position more than the momentum you'll see more point-like particle behavior, but never only just that (you can't ever nail it down to an infinite precision, if you did it'd have a momentum that could send it off at the speed of light as if it had no mass) and in the other case if you could measure infinite precision on the momentum you'd end up measuring the electron as if it was "everywhere" in the universe all at once, which is just as nonsensical of a result as the first one.
So that's where the fun of Quantum Mechanics and uncertainty comes in. Electrons are not just point-like particles, they're sort of both particles and waves. If you nail down exactly where the electron "particle" is, then you end up with it's momentum being less defined, meaning that you're not going to be able to say anything at all about where it came from, where it's going, or how fast. Similarly if you can nail down it's momentum perfectly it won't have a definition of where it is anymore. This isn't the Observer effect, where you making the measurements changes the system, but in fact that the other related property actually ceases to have a valid definition anymore (I'm not well versed enough to say it stops existing with any confidence but that's my understanding). This leads to a situation where you end up measuring a probability density of the property of the electron, so you get a density of it being "around this point +/- some amount" and with a "momentum +/- this amount, and sort of in this direction". This means that you now have a probability density of the electron where you'll see it's effects of the negative charge and kinetic energy and those are the things that describe that "cloud of negative charge". The main effect of this that affects things is that you end up with this cloud of all the electrons around an atom and you don't ever observe the individual electrons, just the shells/clouds around the atom and how they change as energy is inserted into the system.
My layman's understanding is that essentially as you make a measurement/system/whatever where it's designed to see the position more than the momentum you'll see more point-like particle behavior, but never only just that (you can't ever nail it down to an infinite precision, if you did it'd have a momentum that could send it off at the speed of light as if it had no mass) and in the other case if you could measure infinite precision on the momentum you'd end up measuring the electron as if it was "everywhere" in the universe all at once, which is just as nonsensical of a result as the first one.
Not bad for an armchair physicist. Disclaimer, my undergraduate degree was in physics but I'm not a quantum expert by any measure and my graduate work took me closer to statistical mechanics.
So for the simplest explanation for you and the parent is that as you said electrons are both particles and waves, there are experiments that we can demonstrate for that. But if you're thinking of the electron cloud then that exists partially because you aren't measuring the electron. Basically this particle(s)/wave(s) orbiting the atom can exist in a lot of different configurations at once determined by it's energy (which is influenced by its/they position and how fast it is/they are moving). For educational purposes we often treat them more exclusively as a particle (early electrodynamics) or a wave (early quantum) depending on what field we are talking about.
Of course there is greater definition I can give to what it is if we want to start talking about what protons and neutrons are made of and most of that is what occurs at the LHC. (But I'm heavily out of my depth in high energy particle physics).
The measurement uncertainty applies to some other properties as well basically your uncertainty in the electron's position (sigma_x) and uncertainty in the electron's momentum (sigma_p) are bound by sigma_p * sigma_x >= hbar/2
hbar is the reduced planck constant and sigma are statistical variance, but that condition must always hold so as sigma_x goes to 0 (you are more certain about the potential) sigma_p must get larger to compensate so you are less certain about the momentum. This measurement collapses the waveform and until enough time passes for the system to "normalize" the momentum will continue to be uncertain, after that you can measure the momentum but the position could be different too.
So for the simplest explanation for you and the parent is that as you said electrons are both particles and waves, there are experiments that we can demonstrate for that. But if you're thinking of the electron cloud then that exists partially because you aren't measuring the electron. Basically this particle(s)/wave(s) orbiting the atom can exist in a lot of different configurations at once determined by it's energy (which is influenced by its/they position and how fast it is/they are moving). For educational purposes we often treat them more exclusively as a particle (early electrodynamics) or a wave (early quantum) depending on what field we are talking about.
Of course there is greater definition I can give to what it is if we want to start talking about what protons and neutrons are made of and most of that is what occurs at the LHC. (But I'm heavily out of my depth in high energy particle physics).
The measurement uncertainty applies to some other properties as well basically your uncertainty in the electron's position (sigma_x) and uncertainty in the electron's momentum (sigma_p) are bound by sigma_p * sigma_x >= hbar/2
hbar is the reduced planck constant and sigma are statistical variance, but that condition must always hold so as sigma_x goes to 0 (you are more certain about the potential) sigma_p must get larger to compensate so you are less certain about the momentum. This measurement collapses the waveform and until enough time passes for the system to "normalize" the momentum will continue to be uncertain, after that you can measure the momentum but the position could be different too.
> I'm not well versed enough to say it stops existing
That's a small detail, but no, it's not that the particle "stops existing". It's that we can't describe the momentum and position of something with indefinite detail with mathematics that is still coherent. The data type we have for describing things can not go there (on the QM language, of course).
And the surprising thing is that QM predicts our experiments with as much detail as we can experiment with. So, we have this language that can't describe something with known position and speed, and as far as anybody is concerned, it's perfectly correct.
That's a small detail, but no, it's not that the particle "stops existing". It's that we can't describe the momentum and position of something with indefinite detail with mathematics that is still coherent. The data type we have for describing things can not go there (on the QM language, of course).
And the surprising thing is that QM predicts our experiments with as much detail as we can experiment with. So, we have this language that can't describe something with known position and speed, and as far as anybody is concerned, it's perfectly correct.
What does it mean though to say an electron is a particle? Isn’t a particle an excitation of a quantum field? What does it mean to talk about the shape of a field?
Yes an electron is a “quantized vibration” of a quantum field (the electron field). The vibration is quantized in the sense that you can only turn on the amplitude of vibration in discrete clicks, not in a continuous way. Two clicks would be two electrons.
Such a quantized vibration has all the properties of a particle: it has a certain mass, it has a certain momentum, it has a certain angular momentum, and when you look at it in another frame of reference, all these quantities transform just as would a particle’s. And, when you “perform a position measurement” it shows up as a single dot. If you don’t do a position measurement it spends most of its time quantum superposition of states of definite position; hence the “cloud” aspect.
Such a quantized vibration has all the properties of a particle: it has a certain mass, it has a certain momentum, it has a certain angular momentum, and when you look at it in another frame of reference, all these quantities transform just as would a particle’s. And, when you “perform a position measurement” it shows up as a single dot. If you don’t do a position measurement it spends most of its time quantum superposition of states of definite position; hence the “cloud” aspect.
Is it the superposition volume (volume of non-zero probabilities?) that is a perfect sphere?
No, the language of “perfect sphere” versus “bumpy sphere” used by the article is just an analogy with a classical object that would interact with an external electric field in a similar way. Even when it is in a single position eigenstate, an electron has another degree of freedom, its spin orientation, that has nothing to do with its position. This is “like” a spinning pool ball in the sense that it possesses angular momentum in a certain direction and reacts to torques like a spinning thing, but beyond this the analogy breaks down. For one thing, its spin can never be increased nor slowed; for another it has this intrinsic spin even when its position is localized to a dot.
Similarly, a non vanishing Electric Dipole Moment would be some preferred direction to its electric interactions in relation to its spin. Its electric field would be slightly oblong even when position is localized to a dot.
So to clarify, there are multiple senses of “electron cloud” at play — the superpositions of positions is what is usually meant by the term, as in electron cloud around nucleus of atom. The article’s use of the term is a tad sloppy since it invites confusion with this — it means something that generates an oblong electric field and reacts to an external electric field through a term in the energy of the form p.E (with p the EDM and E the external electric field).
Similarly, a non vanishing Electric Dipole Moment would be some preferred direction to its electric interactions in relation to its spin. Its electric field would be slightly oblong even when position is localized to a dot.
So to clarify, there are multiple senses of “electron cloud” at play — the superpositions of positions is what is usually meant by the term, as in electron cloud around nucleus of atom. The article’s use of the term is a tad sloppy since it invites confusion with this — it means something that generates an oblong electric field and reacts to an external electric field through a term in the energy of the form p.E (with p the EDM and E the external electric field).
There is an "electron field" everywhere. Electron is a persistent, energetic disturbance of this field that can travel and interact through electroweak force. It's most convenient mathematical description is as if it was a "cloud" of probability of all of it's charge and mass being concentrated at a single point in space.
If we forcefully interact with electron we can reshape this "cloud" to be as small as we need to at the cost of imparting on it random monentum through uncertainty principle.
I think what they measure is that when you interact with electron then its electric field seems to be very spherical to the point that we can rule out a lot of ideas about electron having any internal substructure that might cause the field to be a little bumpy.
If we forcefully interact with electron we can reshape this "cloud" to be as small as we need to at the cost of imparting on it random monentum through uncertainty principle.
I think what they measure is that when you interact with electron then its electric field seems to be very spherical to the point that we can rule out a lot of ideas about electron having any internal substructure that might cause the field to be a little bumpy.
This cloud of probability you're talking about - is it different from the cloud of probabilities of electron's position relative to the atomic nucleus?
It's the same thing for electron that freely propagates as for the one bound, for example inside atom or a molecule. It's just that the shape is different.
I think it's worth mentioning it's not exactly a probability understood as a theoretical chance of something being somewhere. This wave function is what actually is the physical reality. But we can't measure this reality without interacting with it and when we do interact multiple times and interpret those interactions as if they were caused by pointlike particle being in particular spot then we see that results of those interactions have distribution matching this "probability" "cloud" (square of a wave function).
I think it's worth mentioning it's not exactly a probability understood as a theoretical chance of something being somewhere. This wave function is what actually is the physical reality. But we can't measure this reality without interacting with it and when we do interact multiple times and interpret those interactions as if they were caused by pointlike particle being in particular spot then we see that results of those interactions have distribution matching this "probability" "cloud" (square of a wave function).
I'm curious what would it look like if we could expand the size of an atom by a billion times, preserving all its quantum properties.
If you want to see how electron (wave function) can look when it's stuck to a nucleus check out orbital shapes: https://www.google.com/search?q=orbital+shapes
As more and more electrons get stuck to nucleus it gets crowded around it so further electrons form more and more bizarre shapes of larger and larger sizes as only two electrons can stably fit in a single specific shape of a specific size (Pauli exclusion principle). They do it by taking opposite spins.
As more and more electrons get stuck to nucleus it gets crowded around it so further electrons form more and more bizarre shapes of larger and larger sizes as only two electrons can stably fit in a single specific shape of a specific size (Pauli exclusion principle). They do it by taking opposite spins.
Although things are not that easy and ordered....
You can look at simulated orbitals here: https://falstad.com/qmatom/
s-orbitals are spherically symmetrical. You might convince yourself that p-orbitals are also fine, because 3 of them in 3 dimensions do have reasonable rotational symmetry.
You'll notice that when you move to d-orbitals things start to get really weird. 4 of them are fairly equivalent but it turns out that you can cram 10 electrons of this energy around the nucleus in this fashion. So there are 5 d orbitals. And we can't really fit the fifth in similar manner as other 4.
https://profound-advice.com/what-is-the-difference-between-t... Check the video.
So while we technically have 5 d orbitals, one of them is weird. Its weirdness is an artifact of math. To get the orbitals we are solving Schrodinger equation in spherical coordinates, where one axis is chosen as special. This gives us this weird solution. https://chemistry.stackexchange.com/questions/117243/why-is-...
Physical reality can't depend on our choice of coordinate system so this tells us that orbitals as we draw them don't really directly express the physical reality. In actual physical reality all five of d orbitals have the same shape (somewhere in between the nice d and weird d), but since we can't tell the difference between electron on one d orbital from the electron on another then as long as all 5 orbitals sum up to physical reality our math still works, even if we choose to decompose the solution into 5 non-rotationally-symmetrical parts to make math easier on ourselves.
You can look at simulated orbitals here: https://falstad.com/qmatom/
s-orbitals are spherically symmetrical. You might convince yourself that p-orbitals are also fine, because 3 of them in 3 dimensions do have reasonable rotational symmetry.
You'll notice that when you move to d-orbitals things start to get really weird. 4 of them are fairly equivalent but it turns out that you can cram 10 electrons of this energy around the nucleus in this fashion. So there are 5 d orbitals. And we can't really fit the fifth in similar manner as other 4.
https://profound-advice.com/what-is-the-difference-between-t... Check the video.
So while we technically have 5 d orbitals, one of them is weird. Its weirdness is an artifact of math. To get the orbitals we are solving Schrodinger equation in spherical coordinates, where one axis is chosen as special. This gives us this weird solution. https://chemistry.stackexchange.com/questions/117243/why-is-...
Physical reality can't depend on our choice of coordinate system so this tells us that orbitals as we draw them don't really directly express the physical reality. In actual physical reality all five of d orbitals have the same shape (somewhere in between the nice d and weird d), but since we can't tell the difference between electron on one d orbital from the electron on another then as long as all 5 orbitals sum up to physical reality our math still works, even if we choose to decompose the solution into 5 non-rotationally-symmetrical parts to make math easier on ourselves.
The cloud of probable location is the magnitude of the electron's wavefunction, as I understand it. So they're the same thing, but there's extra information in there too beyond simply position (wavefunctions are complex-valued, not real-valued). Source: Dimly remembered undergrad physics.
My model for understanding phenomena where quantum effects matter is this: if you think of the universe like a big sheet of something stretchy, an electron/proton/particle is just a knot tied in the sheet. Outside of some small region local to the knot the sheet looks flat.
It looks flat but the tension isn't flat. That's why that analogy is so beautiful because it suggests the existence of another force that works at any distance and weakens the further away you get from the point of the knot (gravity).
The Standard Model predicts a vanishingly tiny EDM for the electron — nearly a million times smaller than what current techniques can probe.
This is a big achievement, but a lot more work in this direction remains.
This is a big achievement, but a lot more work in this direction remains.
> If an electron were the size of Earth, the experiment could detect a bump the size of a sugar molecule.
Makes sense, as the electrostatic force is about 10^36 times stronger than the gravitational force.
Makes sense, as the electrostatic force is about 10^36 times stronger than the gravitational force.
So the TLDR is that the electric dipole moment of electron seem to match the one predicted by the Standard Model at least as far as our current measurement capability goes and as we get more and more accurate measurements the wiggle room shrinks so the likelihood that the EDM predicted by the SM is correct increases which lowers the likelihood of post SM physics?
Yes and no. First off, "the sm is correct" isn't how to think about this. Newtonian mechanics is "correct" for airplane flight, or even to calculate rocket trajectories. It's a low order approximant of relatavistic mechanics, though. It's incomplete, and you need to add higher order effects to correctly describe the orbit of Mercury, for example.
The SM is incomplete. Among many other things, it dramatically misses the amount of matter generated during the big bang (by about 10^7). To read about the generation of matter over antimatter, check out the Sakharov criteria. (Sakharov was also an interesting dude, but that's for another day.) Matter/antimatter asymmetry is coupled to symmetry violating processes, which also inevitably generate nonzero EDMs.
The SM includes a bit of this asymmetry, which is why it predicts an eEDM at all. The SM's prediction is so small that any detection has to come from beyond SM sources.
The SM is incomplete. Among many other things, it dramatically misses the amount of matter generated during the big bang (by about 10^7). To read about the generation of matter over antimatter, check out the Sakharov criteria. (Sakharov was also an interesting dude, but that's for another day.) Matter/antimatter asymmetry is coupled to symmetry violating processes, which also inevitably generate nonzero EDMs.
The SM includes a bit of this asymmetry, which is why it predicts an eEDM at all. The SM's prediction is so small that any detection has to come from beyond SM sources.
That was what I wanted to raise, SM doesn’t have an allowance for Dark Matter, and also doesn’t not have an explanation for the matter anti matter asymmetry so the article was quite confusing.
The SM does have a bit of matter/antimatter asymmetry, as this asymmetry was first observed in the 60's by Cronin and Fitch (1980 Nobel).
It's just not a big enough asymmetry to account for all this matter we see.
It's just not a big enough asymmetry to account for all this matter we see.
By now, there is a concessions among the particle physics community that SM is incomplete. The same way that we all agree that Newtonian mechanics is incomplete and doesn't describe anything on atomic/quantum level so we don't use it or talk about Newton mechanics when we are in this scale. The same thing happens here, people mostly talk about SM for what it predict and have an answer for not what it lacks (again because it is obviously incomplete).
Hence my confusion with the title and the article at large. We know we need new particles if for nothing else than to explain dark matter (unless we will come with a non-MOND non-matter theory that fits current observations and hopefully is compatible with other well tested theories too).
We also have “known” for a while that the standard model is incomplete but so far actual physics beyond it has been eluding us.
That was to me missing in this article.
We also have “known” for a while that the standard model is incomplete but so far actual physics beyond it has been eluding us.
That was to me missing in this article.
I think more accurate to say:
“Lowers the probability of particular models”
We still have open questions the standard model doesn’t answer — like what’s up with gravity? …why didn’t we have equal parts antimatter? …does braiding have wider implications than anyons? Etc.
We still have open questions the standard model doesn’t answer — like what’s up with gravity? …why didn’t we have equal parts antimatter? …does braiding have wider implications than anyons? Etc.
It's interesting to consider the parallels between the electron's roundness and the cosmic microwave background (CMB) radiation's uniformity. Both seem to defy our expectations of asymmetry, with the electron's shape ruling out new particles and the CMB's uniformity challenging our understanding of the early universe. As we explore these seemingly unrelated phenomena, perhaps there lies a deep, underlying connection that could unite our understanding of the microcosm and the macrocosm, offering a fresh perspective on the laws governing our universe.
For the CMB we predict (or rather invent) "inflation" - a rapid expansion of the space-time to preserve uniformity of early Universe [1]. Inflation lasted for 0.00000000000000000000000000000001s but the size of the Universe increased by 10^30 times.
1. https://www.esa.int/Science_Exploration/Space_Science/Planck...
Edit: I wanted to come up with an analogy of increasing some object to the size of Earth (as it is the biggest object we can experience in real life). Though 10^30 times is so mindbogglingly large that we don't really have any sense of that small sizes at all. The object would have to be smaller than an electron by a trillion times (10^12).
1. https://www.esa.int/Science_Exploration/Space_Science/Planck...
Edit: I wanted to come up with an analogy of increasing some object to the size of Earth (as it is the biggest object we can experience in real life). Though 10^30 times is so mindbogglingly large that we don't really have any sense of that small sizes at all. The object would have to be smaller than an electron by a trillion times (10^12).
Can someone tell me what version of "shape" we're talking about here? I thought electrons were point charges.
I think it's the usual meaning of shape, it's just perhaps that we don't typically think about what that really means. [I was an author of the Imperial study mentioned in the article, and I had some long arguments with my collaborators about whether it was right to describe our measurement as the "shape of the electron", so I feel compelled to defend the point!]
If I pick something up on my desk and feel what shape it is, what I'm really doing is mapping out the interaction between the density of electrons in the object under test and those in my fingers. I might infer that the electrons of the object are distributed in a spherically symmetric way (it's round), or perhaps something more complex (all the other less symmetric shapes).
So shape in the context of the electron shape measurements means how it interacts electromagnetically. If it interacted perfectly spherically symmetrically, I think it would be reasonable to say it was round. If it interacted in a more complex way (as in, you could grab it and rotate it, because it has some non-spherically symmetric interactions) then it's not round. Interestingly, the electromagnetic interactions of an electron are extremely tightly constrained by it having only 1/2 unit of spin. You can expand any field around a point in terms of spherical harmonics, and you can show the with spin 1/2, the electron can only interact in the manner of the first two spherical harmonics - monopole and dipole. So it can be round (monopole), or round + a more negative and less negative end (dipole). Nothing more complicated than that. (Assuming you believe quantum mechanics. The Wigner-Eckart theorem is the thing to look up if you're interested.)
These measurements, then are measuring the dipolar component of the electron's electromagnetic interaction. The only way in which it could be not round.
As to the point charge thing: well, that's like your opinion man :-) Which is to say, the electron is what the electron is, and it cares not how humans decide to describe it! These experiments are fine examples of a long tradition of measuring and observing to make sure our theoretical descriptions are actually faithful to reality.
You might be tempted so say that if one of these measurements discovered that the electron was not round, then maybe that would be evidence for the electron being not a point particle. It's complicated though ... and you'd find many physicists would start arguing with you if you did say that, because the current description of the electron - while being a point particle in a certain sense - is already pretty complicated (basically, because of interactions between all of the different quantum fields) and many people would say it's already not point-like. Many wouldn't though. Maybe the point here it's quite tricky to be precise about these things without just doing it properly with maths!
If I pick something up on my desk and feel what shape it is, what I'm really doing is mapping out the interaction between the density of electrons in the object under test and those in my fingers. I might infer that the electrons of the object are distributed in a spherically symmetric way (it's round), or perhaps something more complex (all the other less symmetric shapes).
So shape in the context of the electron shape measurements means how it interacts electromagnetically. If it interacted perfectly spherically symmetrically, I think it would be reasonable to say it was round. If it interacted in a more complex way (as in, you could grab it and rotate it, because it has some non-spherically symmetric interactions) then it's not round. Interestingly, the electromagnetic interactions of an electron are extremely tightly constrained by it having only 1/2 unit of spin. You can expand any field around a point in terms of spherical harmonics, and you can show the with spin 1/2, the electron can only interact in the manner of the first two spherical harmonics - monopole and dipole. So it can be round (monopole), or round + a more negative and less negative end (dipole). Nothing more complicated than that. (Assuming you believe quantum mechanics. The Wigner-Eckart theorem is the thing to look up if you're interested.)
These measurements, then are measuring the dipolar component of the electron's electromagnetic interaction. The only way in which it could be not round.
As to the point charge thing: well, that's like your opinion man :-) Which is to say, the electron is what the electron is, and it cares not how humans decide to describe it! These experiments are fine examples of a long tradition of measuring and observing to make sure our theoretical descriptions are actually faithful to reality.
You might be tempted so say that if one of these measurements discovered that the electron was not round, then maybe that would be evidence for the electron being not a point particle. It's complicated though ... and you'd find many physicists would start arguing with you if you did say that, because the current description of the electron - while being a point particle in a certain sense - is already pretty complicated (basically, because of interactions between all of the different quantum fields) and many people would say it's already not point-like. Many wouldn't though. Maybe the point here it's quite tricky to be precise about these things without just doing it properly with maths!
Thanks for the clarification! The story I was taught (up to and including a graduate course on relativistic quantum chemistry!) is "delocalized point particle", i.e. it's a point but of course for quantum mechanical reasons it's effectively in many places at once, at least until you collapse the wave function.
Are you talking about the quantum delocalization? And if yes, presumably an isolated electron (since in an atom the shape of the quantum distribution will depend on orbitals?
Sorry if I'm completely off base here -- I'm a mathematical who took some chemistry, but without any particle physics background.
Are you talking about the quantum delocalization? And if yes, presumably an isolated electron (since in an atom the shape of the quantum distribution will depend on orbitals?
Sorry if I'm completely off base here -- I'm a mathematical who took some chemistry, but without any particle physics background.
I'll just paste a comment I had on a different thread because it answers your question as well.
You are not to blame for not understanding this, it's just that the analogy for the electric dipole moment coming from a non-spherical 'shape' of the electron is extremely bad. Moreover it's missing the most important reason why we search for EDMs, because the existence of one in an elementary particle would indicate the violation of the time-reversal symmetry (T), which assuming CPT conservation [1] leads to CP violation (Charge conjugation and parity symmetries). CP violation [2] is needed to explain the matter-antimatter asymmetry of the Universe.
A more proper way, in my opinion, to reason about an electric dipole moment is to think in terms of Feynman diagrams. An EDM (or any dipole moment for that matter) is an interaction of the electron with an electromagnetic field, so interaction between an electron and a photon. The most simple such interaction you can imagine is an electron flying in, at one point it absorbs a photon and flies out - that would be the magnetic dipole moment. You can go more complex though - electron flying in, at one point it emits a photon, then the electron interacts with the EM field (absorbing a photon) and then it reabsorbs the photon it has emitted previously. (Note that these analogies are again not perfect as for elementary particles time and space are not the same as in the macro world). Now, it can get even more complicated: If you have an electron it's not really a 100% pure electron. There is always some chance that it transforms for a short time into a quark or neutrino or whatever you can imagine.
When you analyze all such scenarios (electron going into something else, interacting with the EM field and then going back to an electron) some violate CP symmetry, and those contribute to the electric dipole moment. We use that name (dipole moment) as the final result is as if the electron was a ball with some separation between the negative and positive charges and placed into an electric field it experiences some torque. The analogy misses the most important part though, as if it was such a polarized 'ball' it would not violate CP symmetry.
Within the Standard Model the only source of CP violating interactions come from the weak interaction (CKM matrix). These have a very small contribution as the weak interaction is, as the name suggests, very weak. That's why the Standard Model predicts very tiny electric dipole moments. When we are searching for EDMs we are in fact searching for such rare transformations through some new undiscovered particle that violate CP symmetry. If we detect some non-zero EDM that would mean that there is some interaction that is not included in the standard model that violates CP, not that the electron is not a round sphere or a sphere with a bump.
[1] - https://en.wikipedia.org/wiki/CPT_symmetry [2] - https://en.wikipedia.org/wiki/CP_violation
You are not to blame for not understanding this, it's just that the analogy for the electric dipole moment coming from a non-spherical 'shape' of the electron is extremely bad. Moreover it's missing the most important reason why we search for EDMs, because the existence of one in an elementary particle would indicate the violation of the time-reversal symmetry (T), which assuming CPT conservation [1] leads to CP violation (Charge conjugation and parity symmetries). CP violation [2] is needed to explain the matter-antimatter asymmetry of the Universe.
A more proper way, in my opinion, to reason about an electric dipole moment is to think in terms of Feynman diagrams. An EDM (or any dipole moment for that matter) is an interaction of the electron with an electromagnetic field, so interaction between an electron and a photon. The most simple such interaction you can imagine is an electron flying in, at one point it absorbs a photon and flies out - that would be the magnetic dipole moment. You can go more complex though - electron flying in, at one point it emits a photon, then the electron interacts with the EM field (absorbing a photon) and then it reabsorbs the photon it has emitted previously. (Note that these analogies are again not perfect as for elementary particles time and space are not the same as in the macro world). Now, it can get even more complicated: If you have an electron it's not really a 100% pure electron. There is always some chance that it transforms for a short time into a quark or neutrino or whatever you can imagine.
When you analyze all such scenarios (electron going into something else, interacting with the EM field and then going back to an electron) some violate CP symmetry, and those contribute to the electric dipole moment. We use that name (dipole moment) as the final result is as if the electron was a ball with some separation between the negative and positive charges and placed into an electric field it experiences some torque. The analogy misses the most important part though, as if it was such a polarized 'ball' it would not violate CP symmetry.
Within the Standard Model the only source of CP violating interactions come from the weak interaction (CKM matrix). These have a very small contribution as the weak interaction is, as the name suggests, very weak. That's why the Standard Model predicts very tiny electric dipole moments. When we are searching for EDMs we are in fact searching for such rare transformations through some new undiscovered particle that violate CP symmetry. If we detect some non-zero EDM that would mean that there is some interaction that is not included in the standard model that violates CP, not that the electron is not a round sphere or a sphere with a bump.
[1] - https://en.wikipedia.org/wiki/CPT_symmetry [2] - https://en.wikipedia.org/wiki/CP_violation
If an electron were the size of Earth... did its mass increase or did its density decrease?
Would it be a black hole with a planet-sized event horizon?
What would happen to a sugar molecule on the north pole of a planet-sized electron with infinitesimal density?
Would it be a black hole with a planet-sized event horizon?
What would happen to a sugar molecule on the north pole of a planet-sized electron with infinitesimal density?
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I find this result satisfying. Of course an electron is as a Platonic solid, that's very sensible. God does not play dice -- God plays with marbles.
Explain like I’m five follow up question: is this electron able to exist in infinite places in space or only in predetermined slots?
I.e. does space consists of pixels?
I.e. does space consists of pixels?
Space is not quantized, so yes, the electron has infinite possible locations. There are, however, places the electron cannot be, depending on its energy. See, the electron's energy is quantized, meaning it can only have a predetermined set of values (see atoms' electron shells). The energy determines the wave function and the wave function squared is the probability distribution for the electron's location. This wave function has roots, indicating where the electron cannot be.
preprint is here: https://arxiv.org/abs/2212.11841
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"Imagine an electron as a spherical cloud of negative charge" sorry man, you lost me on the very first sentence
Imagine a spherical cow, then make it really, really tiny
Fine. Oblate spheroidal cloud with a Lakitu in it*
There’s many abstractions. None of them are right. They’re useful for different things. You cannot reject the simpler ones because you have adopted a still wrong but more complex one.
There’s many abstractions. None of them are right. They’re useful for different things. You cannot reject the simpler ones because you have adopted a still wrong but more complex one.
All models are wrong, but some are useful.
Some argue that metaphor is more fundamental to science than math.
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It’s tangential, but I don’t know how physicists understand the “why is there something rather than nothing?” question. At best, it’s quantification without a predicate. At worst, it’s metaphysical gobbledygook of the same variety that physicists constantly deride philosphers for.
But the answer to "why" is always gobbledygook. We try to answer how there is something instead of nothing. I do not think anyone can answer why it is flooding in Florida now. Many can answer the how, multiple levels deep.
'Why" is trying to assign a higher order causality and that is religion.
But, if you are using "why" as a way to probe into inner workings, here is one possible hypothesis - https://www.youtube.com/watch?v=3SxowRIc20M&t=761s
'Why" is trying to assign a higher order causality and that is religion.
But, if you are using "why" as a way to probe into inner workings, here is one possible hypothesis - https://www.youtube.com/watch?v=3SxowRIc20M&t=761s
The same point applies to the phrase "something rather than "nothing." It's not a general concern about "why" questions but a concern about applying quantification to non-specific things.
Quantification in the abstract typically falls under mathematics. This is what we have numbers for. But people make sense of "something rather than nothing" as if it's more than abstraction. People think they understand what they're talking about, but they really don't (literally, not figuratively).
Quantification in the abstract typically falls under mathematics. This is what we have numbers for. But people make sense of "something rather than nothing" as if it's more than abstraction. People think they understand what they're talking about, but they really don't (literally, not figuratively).
This was beautiful thank you.
It’s simple. Antimatter goes the other direction in time.
Just as you can go forwards and backwards in the X dimension. Matter can only go in one direction through time, antimatter the other.
So at the point of the Big Bang matter went on its direction through time saying buh-bye to antimatter that went in the opposite direction.
Note: I didn’t say forward and backwards because from their perspective we are the ones who went in the opposite direction.
This accounts for the lack of antimatter, the “missing mass” of the universe and why time travel (other than into the future for us) is impossible as the only way you could go in the opposite direction (the past) would be to convert yourself to antimatter which would be very very bad.
This also doesn’t mean there is an antimatter earth somewhere out there (in the other time direction so we’d never know anyway) because at the point of the Big Bang an entire series of events / interactions would have occurred. There’s no interacting link between the two times (t+1 vs t-1)
Figure out the maths for yourself…
Just as you can go forwards and backwards in the X dimension. Matter can only go in one direction through time, antimatter the other.
So at the point of the Big Bang matter went on its direction through time saying buh-bye to antimatter that went in the opposite direction.
Note: I didn’t say forward and backwards because from their perspective we are the ones who went in the opposite direction.
This accounts for the lack of antimatter, the “missing mass” of the universe and why time travel (other than into the future for us) is impossible as the only way you could go in the opposite direction (the past) would be to convert yourself to antimatter which would be very very bad.
This also doesn’t mean there is an antimatter earth somewhere out there (in the other time direction so we’d never know anyway) because at the point of the Big Bang an entire series of events / interactions would have occurred. There’s no interacting link between the two times (t+1 vs t-1)
Figure out the maths for yourself…
Physicists are able to produce small quantities of matter and antimatter, which then annihilate each other, releasing energy. It was a big deal when they were able to trap the antimatter so that it didn't do this.
If the two particles travelled different directions in time, how would they meet?
If the two particles travelled different directions in time, how would they meet?
> Physicists are able to produce small quantities of matter and antimatter, which then annihilate each other, releasing energy. […] If the two particles travelled different directions in time, how would they meet?
The anti-matter would travel backwards in time from the event we see as the “mutual annihilation” to the event we see as the “creation of paired particles”, while the matter would travel the other direction. Simple.
When they don’t meet is a little trickier to explain, but its still the anti-particle coming back from somewhere in the future (possibly where it coincided with a different matter particule coming forward in time) and coinciding with the particle at the point we consider the “creation” point, and the same vice versa with the matter particle.
I’m not saying it’s right, I’m saying that’s how you explain them “meeting” in the “anti-matter goes back in time” framework.
The anti-matter would travel backwards in time from the event we see as the “mutual annihilation” to the event we see as the “creation of paired particles”, while the matter would travel the other direction. Simple.
When they don’t meet is a little trickier to explain, but its still the anti-particle coming back from somewhere in the future (possibly where it coincided with a different matter particule coming forward in time) and coinciding with the particle at the point we consider the “creation” point, and the same vice versa with the matter particle.
I’m not saying it’s right, I’m saying that’s how you explain them “meeting” in the “anti-matter goes back in time” framework.
(I give absolutely no credence to the root of this comment tree...)
There was an idea posed a bit ago known as the "one electron universe" ( https://en.wikipedia.org/wiki/One-electron_universe )
> The one-electron universe postulate, proposed by theoretical physicist John Wheeler in a telephone call to Richard Feynman in the spring of 1940, is the hypothesis that all electrons and positrons are actually manifestations of a single entity moving backwards and forwards in time. According to Feynman:
> > I received a telephone call one day at the graduate college at Princeton from Professor Wheeler, in which he said, "Feynman, I know why all electrons have the same charge and the same mass" "Why?" "Because, they are all the same electron!"
> ...
> Feynman was struck by Wheeler's insight that antiparticles could be represented by reversed world lines, and credits this to Wheeler, saying in his Nobel speech:
> > I did not take the idea that all the electrons were the same one from [Wheeler] as seriously as I took the observation that positrons could simply be represented as electrons going from the future to the past in a back section of their world lines. That, I stole!
> Feynman later proposed this interpretation of the positron as an electron moving backward in time in his 1949 paper "The Theory of Positrons". ...
---
PBS Space Time : The One-Electron Universe https://youtu.be/9dqtW9MslFk (highly recommended)
The idea has mathematical utility, but not any practical.
There was an idea posed a bit ago known as the "one electron universe" ( https://en.wikipedia.org/wiki/One-electron_universe )
> The one-electron universe postulate, proposed by theoretical physicist John Wheeler in a telephone call to Richard Feynman in the spring of 1940, is the hypothesis that all electrons and positrons are actually manifestations of a single entity moving backwards and forwards in time. According to Feynman:
> > I received a telephone call one day at the graduate college at Princeton from Professor Wheeler, in which he said, "Feynman, I know why all electrons have the same charge and the same mass" "Why?" "Because, they are all the same electron!"
> ...
> Feynman was struck by Wheeler's insight that antiparticles could be represented by reversed world lines, and credits this to Wheeler, saying in his Nobel speech:
> > I did not take the idea that all the electrons were the same one from [Wheeler] as seriously as I took the observation that positrons could simply be represented as electrons going from the future to the past in a back section of their world lines. That, I stole!
> Feynman later proposed this interpretation of the positron as an electron moving backward in time in his 1949 paper "The Theory of Positrons". ...
---
PBS Space Time : The One-Electron Universe https://youtu.be/9dqtW9MslFk (highly recommended)
The idea has mathematical utility, but not any practical.
My only difference to that is that the positrons and electrons went in opposite directions on the time axis from the initial big bang event. I love the idea of a single electron being the scan line of the universe (to make an analogy to CRTs)
Assume you take the normal x,y,z we “know” from reality and separate them out into 3 distinct 1 dimensional lines.
Add another 1d line for time.
We can see you can’t simultaneously move both “forwards” and “backwards” on any of these lines.
Postulate: for time, matter (from our point of view) can only move in a singular direction from t=0 onwards (we’ll call this positive), antimatter can only move in the opposite from t=0 (negative).
And, unless there is momentum in any of the spatial dimensions the particles travel on the t axis at C. I.e v=C on the t axis for matter And v=-C for antimatter.
Second Postulate: the cumulative velocity of all particles must equal the speed of light
Any momentum in the spatial (x,y,z) dimensions subtracts from t: explains time dilation (as an adjunct)
v(t) = C-(v(x)+v(y)+v(z)) (very very simplified for this)
Finally matter / antimatter annihilation is the equivalent vv, as is the case for any direct impact of two masses of equal mass and velocity. Giving us e=m(cc), in a general sense without all the pesky gravitational warping of space and time.
Btw: I’m not a particle physicist (can you tell) but I did have this thought while developing code for a physics engine in a simulation game I was briefly involved in, so far I’ve not invested heavily in all the mathematics, but since I’ve just retired I might actually do so.
Assume you take the normal x,y,z we “know” from reality and separate them out into 3 distinct 1 dimensional lines.
Add another 1d line for time.
We can see you can’t simultaneously move both “forwards” and “backwards” on any of these lines.
Postulate: for time, matter (from our point of view) can only move in a singular direction from t=0 onwards (we’ll call this positive), antimatter can only move in the opposite from t=0 (negative).
And, unless there is momentum in any of the spatial dimensions the particles travel on the t axis at C. I.e v=C on the t axis for matter And v=-C for antimatter.
Second Postulate: the cumulative velocity of all particles must equal the speed of light
Any momentum in the spatial (x,y,z) dimensions subtracts from t: explains time dilation (as an adjunct)
v(t) = C-(v(x)+v(y)+v(z)) (very very simplified for this)
Finally matter / antimatter annihilation is the equivalent vv, as is the case for any direct impact of two masses of equal mass and velocity. Giving us e=m(cc), in a general sense without all the pesky gravitational warping of space and time.
Btw: I’m not a particle physicist (can you tell) but I did have this thought while developing code for a physics engine in a simulation game I was briefly involved in, so far I’ve not invested heavily in all the mathematics, but since I’ve just retired I might actually do so.
Electrons don't need to move backwards in time to become positrons. Rather, I think, that one uber-electron peacefully exists on its natural multidimensional manifold, and it's us, who declare one axis to be "time", create the dihotomy of that electron sometimes aligning with the timeline and sometimes against it. If we chose 2 coordinates as time, the same uber-electron would create a whole host of ekectron-like particles, depending on how it's aligning with the two timelike directions.
The matter particle already existed we annihilated it with an antiparticle, that released m(cc) energy from which 50% of it was released as energy (the matter part) and 50% created the anti-particle that came into existence when we created it.
From out point of view it all makes sense:
Create anti-particle
Smash it into equivalent particle
Energy released
???
Profit
From the anti-patter point of view:
Profit
???
Energy coalesced into antiparticle
Particle unsmashes
Particle stops existing.
I’m mr meseeks look at me!
From out point of view it all makes sense:
Create anti-particle
Smash it into equivalent particle
Energy released
???
Profit
From the anti-patter point of view:
Profit
???
Energy coalesced into antiparticle
Particle unsmashes
Particle stops existing.
I’m mr meseeks look at me!
This new bound is sensitive to energies above roughly 10^13 electron-volts — more than an order of magnitude beyond what the LHC can currently test.
Wow.