A clever “perpetual motion” device [video](youtube.com)
youtube.com
A clever “perpetual motion” device [video]
https://www.youtube.com/watch?v=r_LG8FDt51U
129 comments
This circuit is awfully complex.... it's possible to do the same with a far simpler circuit if you use the same coil for sensing and accelerating the ball.
A small microcontroller could do both - perhaps even with low enough power that the whole circuit could stay turned on for years on a charge (when not flinging the ball).
Looking at the total energy you need to impart on the ball, you should be able to do that with a far smaller coil and many fewer capacitors as long as you have a suitably shaped steel core to keep the flux path low. I suspect you might be able to do it with no capacitors at all, since modern lithium cells are perfectly happy to deliver 100 amps for a few milliseconds.
A small microcontroller could do both - perhaps even with low enough power that the whole circuit could stay turned on for years on a charge (when not flinging the ball).
Looking at the total energy you need to impart on the ball, you should be able to do that with a far smaller coil and many fewer capacitors as long as you have a suitably shaped steel core to keep the flux path low. I suspect you might be able to do it with no capacitors at all, since modern lithium cells are perfectly happy to deliver 100 amps for a few milliseconds.
> This circuit is awfully complex ... A small microcontroller could do both
Adding a microcontroller might reduce the number of components used, but it's a bit disingenuous to claim the result is "simpler".
Adding a microcontroller might reduce the number of components used, but it's a bit disingenuous to claim the result is "simpler".
I think you could drop coil sensing of the ball entirely and simply switch the electromagnet using the metal ball contacting the two metal rails. A dialectic gap in the rails near the bottom of the track could turn the electromagnet off at the right moment.
[deleted]
You say that the circuit is complex, but it's the other way around.
Its simplicity is the cause of the high component count.
Its simplicity is the cause of the high component count.
An entire microcontroller to run an approx 3-line program?
Using a single coil, the microcontroller program is pretty complicated. It needs to pulse the coil very briefly on a regular basis and measure the resonant frequency.
If you do the capacitor-less design, you might want to have a steel core with sawtooth top, and then use software to measure the position of the ball relative to each tooth and turn the coil on while the ball is heading towards a tooth and off when the ball is heading away. That allows the energy to be extracted from the battery slower.
You might also choose to have your coil driven by an h-bridge. That means you can put the energy from the magnetic field that builds up in the steel core back into the battery between each 'tooth'. That should dramatically increase energy efficiency, allowing you to use a smaller (cheaper, lighter, more eco friendly) cell or have the battery last longer. To do that, you'll need current sensing too.
If you do the capacitor-less design, you might want to have a steel core with sawtooth top, and then use software to measure the position of the ball relative to each tooth and turn the coil on while the ball is heading towards a tooth and off when the ball is heading away. That allows the energy to be extracted from the battery slower.
You might also choose to have your coil driven by an h-bridge. That means you can put the energy from the magnetic field that builds up in the steel core back into the battery between each 'tooth'. That should dramatically increase energy efficiency, allowing you to use a smaller (cheaper, lighter, more eco friendly) cell or have the battery last longer. To do that, you'll need current sensing too.
Throw in a node.js implementation with 100 dependencies and we're cooking, simple as.
That's very common. Look at all the $0.03 microcontrollers on LCSC. They save time, money, and board space.
Cheaper than to have a microcontroller that results in a smaller PCB vs discrete components that make the PCB bigger.
I'd like to see the videos of your version!
Railgun instead.
Be aware that most of the cheap knockoffs just use a motorized wheel. For example, see the videos on https://www.amazon.com/dp/B09VTJ4LZ8/#ive-videos-for-this-pr...
They also use diagrams showing the ball traveling the wrong way. https://imgur.com/a/o3sHFhX
The art on most of Amazon's listings is just a thing of beauty, if you're into really bad photoshopping. Some of them are really eyebrow raising, while others are more WAT. I use it as a litmus test as clearly a knock off item, and move away from that listing.
The other day I came across the first use of stable diffusion in a listings product in use photos. To me it was obvious, knowing what to look for, but to the average user they'd never know, unless they really paid attention.
I can almost understand the bad photoshopping from a desire to put the product in situ but you have no budget/time/care to do a real shoot. To what level of generative art did they use for this product shot? Any chance you have a link?
Scroll down to the 2 product in use photos. It's painful to see.
https://www.amazon.com.au/Electric-Temperature-40%C2%B0C-120...
https://www.amazon.com.au/Electric-Temperature-40%C2%B0C-120...
thanks for following up. i've been very curious. there's definitely a lot going on with this listing. luckily, it's not available, so one layer of scam protection is working. however, someone should teach the "artist" about scale and the affect it has on how the viewer.
Maybe it's because you're not based in AU/NZ (where com.au delivers), but for me, sadly, it shows as very much in stock.
The seller "FANLIB" has "just launched" according to Amazon and has no feedback yet. https://www.amazon.com.au/sp?ie=UTF8&seller=A138IJ2CHQMEWS
https://i.imgur.com/ZZOfdz6.png
Makes me sad.
The seller "FANLIB" has "just launched" according to Amazon and has no feedback yet. https://www.amazon.com.au/sp?ie=UTF8&seller=A138IJ2CHQMEWS
https://i.imgur.com/ZZOfdz6.png
Makes me sad.
It makes a horrible sound in the videos, but it's not obvious to me what you mean by "motorized wheel".
None of the mechanism is visible at all, certainly no wheel, motorized or not. How does a motorized wheel accomplish this?
None of the mechanism is visible at all, certainly no wheel, motorized or not. How does a motorized wheel accomplish this?
> None of the mechanism is visible at all, certainly no wheel, motorized or not. How does a motorized wheel accomplish this?
Probably a simple spinning wheel inside of the ball collection area.
Spinning rubber wheel in the hole the ball drops through before getting on the track. Notice how the ball doesn't differ in speed at all after it's fallen, vs the original feels natural (gaining momentum) until it gets close to the bottom.
Edit: In one of the Amazon review images[0] you can see a black spot in the ball drop hole, maybe there.
[0]: https://i.imgur.com/xb65ljL.png
Probably a simple spinning wheel inside of the ball collection area.
Spinning rubber wheel in the hole the ball drops through before getting on the track. Notice how the ball doesn't differ in speed at all after it's fallen, vs the original feels natural (gaining momentum) until it gets close to the bottom.
Edit: In one of the Amazon review images[0] you can see a black spot in the ball drop hole, maybe there.
[0]: https://i.imgur.com/xb65ljL.png
Oh I see what you mean.
On the Amazon one (as opposed to the YouTube video) the balls come shooting down out of the upper collection area at high speed. And the upper collection area is much thicker. So it's hiding some kind of mechanism.
On the Amazon one (as opposed to the YouTube video) the balls come shooting down out of the upper collection area at high speed. And the upper collection area is much thicker. So it's hiding some kind of mechanism.
You can also accelerate it from the ball collection area using a coil gun mechanism. A motor adds too much cost and moving parts.
If you listen to the amazon review videos you can hear a motor, or at least something else spinning at high speed.
Just guessing, but maybe there's some magnets attached to the wheel and they accelerate the ball as it gets near the bottom.
Brings back childhood memories. Enjoyed reading about these and the accompanying illustrations as a kid from the excellent book Physics for Entertainment by Yakov Perelman. Nirantara Chalana Yantralu they were called in Telugu translation.
> Physics for Entertainment by Yakov Perelman
I read the same in Malayalam! That book was one of my earliest introductions to practical physics. He deconstructs pretty much all the early "perpetual machine" designs in the book.
I also particularly remember the chapter with the experiments with soap bubbles as being very interesting as a kid.
I read the same in Malayalam! That book was one of my earliest introductions to practical physics. He deconstructs pretty much all the early "perpetual machine" designs in the book.
I also particularly remember the chapter with the experiments with soap bubbles as being very interesting as a kid.
Thank you for the suggestion!
Yakov Perelman - Physics for Entertainment - https://archive.org/details/PhysicsForEntertainment-Eng-Yako...
I see that Astronomy for Entertainment, Algebra for Entertainment, Figures for Entertainment also exist.
Yakov Perelman - Physics for Entertainment - https://archive.org/details/PhysicsForEntertainment-Eng-Yako...
I see that Astronomy for Entertainment, Algebra for Entertainment, Figures for Entertainment also exist.
I had the Arabic translated edition of that book! same fond memories!
Was anyone else hoping it would detect the ball by simply completing a circuit (since the rails are metal and so is the ball)? Then it could give a magnetic tug after an appropriate time. Maybe this would be flaky because of the poor contact between rails and a rolling ball, but an inductive proximity sensor feels like overkill.
It probably wouldn't work nearly as well.
It looks like the rails are already a complete circuit - I think they're a single piece of wire that is bent at the end to make a loop, and there are a couple lateral braces soldered on to keep them properly spaced.
You'd have to split the rails into two pieces and replace the lateral braces with something nonconductive (plastic) which wouldn't look nearly as nice; and the device would be a lot more prone to going out of calibration if the spacing drifted.
Its probably possible but there's a lot of downsides to save $2 on a sensor, some of which will be eaten up elsewhere as it will add some additional parts.
Edit: It would also somewhat spoil the magic, as that's the first thing most of us would think of (I certainly did).
It looks like the rails are already a complete circuit - I think they're a single piece of wire that is bent at the end to make a loop, and there are a couple lateral braces soldered on to keep them properly spaced.
You'd have to split the rails into two pieces and replace the lateral braces with something nonconductive (plastic) which wouldn't look nearly as nice; and the device would be a lot more prone to going out of calibration if the spacing drifted.
Its probably possible but there's a lot of downsides to save $2 on a sensor, some of which will be eaten up elsewhere as it will add some additional parts.
Edit: It would also somewhat spoil the magic, as that's the first thing most of us would think of (I certainly did).
I was thinking a pair of tiny contacts could touch the ball and complete the circuit, but you're right, this isn't an engineering opportunity, but a performance issue. You shouldn't expose electricical components in a perpetual motion simulator.
Yes flaky, it's going to corrode and get dirty so the connections won't be reliable
Steve Mould is top-notch
This one is pretty good, but I usually steer clear of his videos. Topics are pretty on point for my interests, be he just seem... Too full of himself?
I don't want to be mean in any way, but if someone agrees maybe they can put a finger on what it is
What is your background? I know that many Americans perceive a British accent as snobbish/arrogant (this is often used in Hollywood movies as well). So maybe it's just that?
There are a few youtubers that come to mind who fit this description, but Steve Mould is not one of them.
I feel like your mind must have confused two people. Steve is very down to Earth.
Maybe his youtube-battle with ElectroBOOM turned you off? Where he was pretty convinced he was right about the chain fountain.
Maybe his youtube-battle with ElectroBOOM turned you off? Where he was pretty convinced he was right about the chain fountain.
Nah I always have the same impression, even though I’ve been watching for years (long before the chain thing), and I can see the janky setups trying to figure things out.
I think it’s mostly the voice / accent, to me it… sounds sneery?
I think it’s mostly the voice / accent, to me it… sounds sneery?
I find him very down to earth with a healthy dose of humour and self deprecation.
Maybe it could be a British thing? Perhaps there's some culture-specific signalling that can be read in a different way in a different culture?
Maybe it could be a British thing? Perhaps there's some culture-specific signalling that can be read in a different way in a different culture?
That is what I assume yes, but I don’t know where I picked it up.
I didn't get the impression he's too full of himself, but he was confident for sure. That's not being full of oneself though, that's making a video interesting, confidence, and not filling the space with caveats or self-deprecation.
His voice and presentation style do give me the same feeling. I don’t know why. Same with Mark Rober.
But the actual content is the opposite. It’s really quite strange.
But the actual content is the opposite. It’s really quite strange.
Yeah, I think I can see the link to Mark Rober. Although not at all to the same degree.
Maybe it's the way of "acting dumb" in order to progress the discovery process, but a face that they know full well (obviously) that he knows what's going on? Essentially talking down to the audience?
Not sure. My first attempt at phrasing it did not get my feeling across well.
Not sure. My first attempt at phrasing it did not get my feeling across well.
I like Steve Mould and dislike Mark Rober. hmmm. I feel a pretty good judge of character, Steve Mould is quite often humble and self effacing but he does mug and talk in a very intimate way - some people might dislike that from someone they don't really know.
I don't know him but I feel he is a bit tongue-in-cheek with humour. As far as I remember, he did comedy and was also good with education with kids. I don't imagine meeting him and him coming across as full of himself though. I feel I could approach him in a pub and he would have good banter.
some people just don't get there's a joke unless there's a laugh track
This one is pretty representative of what his videos are like. Could be that you got a skewed first impression? Once you watch a few of them, you can see he's pretty genuine.
Full of himself? He literally dresses in a tutu and spins in the mirror in this video.
Too full of himself? I'm not sure I understand, can you give an example?
Its cool, but it seems kind of obvious how it would work. Uou can tell the ball is speeding up at the wrong times. It'd be cooler if they could make the motion look more natural.
That would be definitely interesting. Myself, I could see the following developments:
1) More caps and work in it being powered by ambient light. 2) Taller, perhaps multi-stage. 3) Multiple paths that were somewhat random.
Really, I think I am inventing a cat toy. When I was small, I had a racetrack game with just enough randomness to keep my cat completely fascinated.
1) More caps and work in it being powered by ambient light. 2) Taller, perhaps multi-stage. 3) Multiple paths that were somewhat random.
Really, I think I am inventing a cat toy. When I was small, I had a racetrack game with just enough randomness to keep my cat completely fascinated.
Excellent presentation, no dumb graphics, witticism, silly voices or stupid faces pulled etc, just nice clean explanation.
Nice toy too. I'd get one but I'd turn it on 3 times then get bored and give it away.
Nice toy too. I'd get one but I'd turn it on 3 times then get bored and give it away.
I like the idea that the laws of physics allow us to draw conclusions with certainty, despite what our eyes observe: we are sure it's no perpetual device, since science says it's impossible.
Exactly with the Sun: our eyes observe that Sun goes around Earth, but science tells us otherwise.
Reminds me of the definition of Faith in the Holy Scriptures: "the evident demonstration of realities that are not seen." (Hebrews 11:1) Yes, there are realities that exist beyond what we can see, that we can deduce with reasoning.
Edit: typo
Exactly with the Sun: our eyes observe that Sun goes around Earth, but science tells us otherwise.
Reminds me of the definition of Faith in the Holy Scriptures: "the evident demonstration of realities that are not seen." (Hebrews 11:1) Yes, there are realities that exist beyond what we can see, that we can deduce with reasoning.
Edit: typo
> Exactly with the Sun: our eyes observe that Sun goes around Earth, but science tells us otherwise.
These are just two different reference frame. Both are equivalent.
These are just two different reference frame. Both are equivalent.
Tell that to the 16th century Catholic church...
That's the irony though, both them and the high school teacher telling you they were wrong is making the same category of error.
It's a debate over where to put the origin of the coordinate system, which is an arbitrary choice.
It's a debate over where to put the origin of the coordinate system, which is an arbitrary choice.
so you mean the train is not moving?
The whole reason science works is that we start by assuming what our eyes tell us is true, and then come up with models to explain that.
Edit: plato believed the nature of reality could be discerned with pure reason. He was wrong.
Science also works only because it always assumes that its models may be wrong.
Edit: plato believed the nature of reality could be discerned with pure reason. He was wrong.
Science also works only because it always assumes that its models may be wrong.
Huh, I'd always assumed the ball simply closed a circuit when it rode on the rails, and that's how it knew when to turn the magnet on and off, with suitable delays. It does seem to me you could still do it that way, but it'd probably be more difficult.
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I wonder if the creator of this device William Le [1] has managed to make this his full-time endeavor.
[1]: https://www.etsy.com/shop/backtonaturedecor
[1]: https://www.etsy.com/shop/backtonaturedecor
He is selling a lot of them today. Another one every minute or so right now.
Hmm I wonder if he has enough already made or if it becomes a long backorder situation. 152 sold recently and it they are hand made it could take a while!
This got me wondering if it could be made to be entirely mechanical. Like, the approaching ball triggers something to move in front of the magnet 'switching it off', then slides away again when the ball has passed, ready for the next run.
I think I just invented perpetual motion...
I think I just invented perpetual motion...
Any mechanism that could switch the magnet on and off would require energy. E.g. you could put a magnet next to it with opposite poles, which would mostly cancel out the magnetic field, but would require a lot of force to push them together, which is work, and thus requires energy.
No reason you couldn't do that as long as you just mean the actuation is purely mechanical. You'd still need an electromagnet and power source though, as it only works if you can turn the magnet on and off.
The easiest perpetual motion is just drop a tennis ball. It is just that the perpetually moving thing is no longer the ball :-)
What do you propose to use as an energy source?
Just build a second machine to power the first!
clockwork wind-up.
It would be bulky but maybe you could put a permanent magnet on a sled or wheel that would impart the necessary force on the metal ball as it approached but then and flipped repelled it. Would be difficult to make work smoothly or at all...
Could this work as a magnetic rail with earth magnets? Would that not require any batteries then?
How would you "switch off" the magnets as the train approaches so as to allow it to pass with its newly gotten energy?
I'm not sure if the GP is proposing a railgun. In any case, I propose a railgun version. https://en.wikipedia.org/wiki/Railgun
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What do you propose to use as an energy source?
Ooh, I'd love to find one of these on Ali, but their search is betraying me currently.
The circuit is awfully complex
Damn I kinda want to build little doohickeys and sell them on etsy instead of going to work every morning
I can tell you that this has two possible outcomes:
1. You don't sell enough to get by.
2. You sell enough for Chinese knock-offs to come in and offer a good-enough clone product for 1/3 your raw material cost.
Being a first world tiny shop in hardware is near impossible.
1. You don't sell enough to get by.
2. You sell enough for Chinese knock-offs to come in and offer a good-enough clone product for 1/3 your raw material cost.
Being a first world tiny shop in hardware is near impossible.
(3) you make good looking gizmos which are not really worth copying seems to be the niche of “William”. Apparently the slides were about 150, and they’re externally simple but good looking. They’re out of stock but the shop has neat kinetic sculpture for high hundreds.
Could you get plastic versions for a third the price? Absolutely. Would you? Hell nah. I could see kits of spare parts to print and build your own, maybe, but not ready made.
Could you get plastic versions for a third the price? Absolutely. Would you? Hell nah. I could see kits of spare parts to print and build your own, maybe, but not ready made.
If you search for "perpetual motion machine" you can find a ton of cheap knockoffs of this device. You can get a badly made wooden knockoff for $50 or quite a bit less?
There are a bunch of tiny hardware shops in the audio community that seem to be doing fine, for example https://neurochrome.com/
Of course, running a small business like this is not easy, but it's not impossible either.
Of course, running a small business like this is not easy, but it's not impossible either.
When it comes to pricing products at absolutely outrageous multiples of material cost, the "audio community" seems to be in its own league. I don't think the desktop toy market is quite there.
You are then no longer selling the toy, but the “My one is OG” status. And the certainty that it will work. Once you reach a certain age fucking about returning stuff to save a few bucks seems silly.
Not just OG status, quality. The Chinese knock-offs truly are worse. I've seen this gadget on Youtube before, compared to one of the knock-offs.
Executive desk toys are a classic premium market!
Executive desk toys are a classic premium market!
Yes certainly. This is what I meant when I said "certainty that it will work". A low bar for quality, but a bar knock offs can't reach usually.
Nothing stopping you! I have git and printables etc accounts full of stuff I've designed and shared, but some folks might just want the finished thing so awhile back I hung out my hat and started a small shop selling the widgets I design and share for free.
Turns out a lot of people just want the thing, I can give the plans away and still make some extra on the side by making a few to sell.
I'm incredibly far away from being able to quit my job over this, but it has turned a few of my hobbies into slightly net-profitable ventures instead of money holes and the result is a well appointed shop to spend my free time playing around with new ideas.
My advice: give it a shot. There's nearly zero up front cost and if nothing else, you'll probably learn a bit.
Turns out a lot of people just want the thing, I can give the plans away and still make some extra on the side by making a few to sell.
I'm incredibly far away from being able to quit my job over this, but it has turned a few of my hobbies into slightly net-profitable ventures instead of money holes and the result is a well appointed shop to spend my free time playing around with new ideas.
My advice: give it a shot. There's nearly zero up front cost and if nothing else, you'll probably learn a bit.
[deleted]
The video is worth just for his expression at 1:07. Highly recommended. Have no interest in the topic and watched the whole thing!
For those who don't know, it's a reference to Technology Connections[0], another incredible YouTube channel. Alec, the host, is very fond of that bit[1].
[0] https://youtube.com/@TechnologyConnections [1] https://www.youtube.com/watch?v=CZs-YcmxyUw
[0] https://youtube.com/@TechnologyConnections [1] https://www.youtube.com/watch?v=CZs-YcmxyUw
i have only seen a few of alec's videos, but i immediately recognized this as familiar, wondering "hey, that's a different guy"
Oh my gosh, the green screen
Hah yeah, for some reason that line never gets old for me.
It’s short, it’s snappy, and it’s only deployed appropriately (by Alec, and by Steve here), so it stays fresh and not overdone.
And other similarly nice recurring gag is Tasting History’s hardtack.
And other similarly nice recurring gag is Tasting History’s hardtack.
[deleted]
Lost it at the "through the magic of buying two of them" bit!
That, by the way, is a reference to another great channel - Technology Connections: https://youtube.com/@TechnologyConnections
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Steve makes an interesting statement when he says "we know that perpetual motion is not possible". Yet we have a modification to the general cosmological view with the theoretical entity "dark energy" which if you consider what is said about it properties, it provides a means of creating a "perpetual motion" environment.
So what can we say: Does perpetual motion exist or not?
So what can we say: Does perpetual motion exist or not?
Energy is not globally conserved in an expanding universe, dark energy existing or not.
https://www.preposterousuniverse.com/blog/2010/02/22/energy-...
https://physics.stackexchange.com/questions/259759/conservat...
https://twitter.com/WKCosmo/status/1303134701180325890?t=pv5...
Obviously the guy in the video was making the implicit assumption that we are talking about local experiments.
https://www.preposterousuniverse.com/blog/2010/02/22/energy-...
https://physics.stackexchange.com/questions/259759/conservat...
https://twitter.com/WKCosmo/status/1303134701180325890?t=pv5...
Obviously the guy in the video was making the implicit assumption that we are talking about local experiments.
The accepted solution in the second link claims your other two links are wrong:
> Some people claim incorrectly that energy is not conserved in an expanding universe because space-time is not static. The law of Energy conservation is derived from Noether's theorem when the dynamical equations are unchanged with time. These people confuse the invariance of the equations with the invariance of the solution. Space-time changes but the equations obeyed by the expanding universe do not change. Space-time cannot be treated as a background, its dynamics must be included when deriving the enrgy equations via Noether's theorem. This leads to the equations given above which show that energy is indeed conserved.
> Some people claim incorrectly that energy is not conserved in an expanding universe because space-time is not static. The law of Energy conservation is derived from Noether's theorem when the dynamical equations are unchanged with time. These people confuse the invariance of the equations with the invariance of the solution. Space-time changes but the equations obeyed by the expanding universe do not change. Space-time cannot be treated as a background, its dynamics must be included when deriving the enrgy equations via Noether's theorem. This leads to the equations given above which show that energy is indeed conserved.
[tl;dr momentum loss is a generic feature of a spacetime which has a metric expansion of space. Informally, every future direction is uphill, so everything has to roll uphill[*]. If the expansion is accelerated by a cosmological constant the hill steepens with the expansion. The author of the accepted answer at the phys SE link seems to want to argue that the slowdown while rolling uphill is what generates the hill. It's not.
The hill is generated by the initial impulse that kicks off the expansion and driver of the expansion-acceleration if any.]
So, uhhm, let's look at the
> accepted solution in the second link
which was authored by the hagiographic https://www.vixrapedia.org/wiki/Philip_Gibbs (in which there's a whole section "Energy Conservation in General Relativity": "... Gibbs is the leader of a small minority of commentators who dispute [that energy conservation only works in special cases]".
In the comments below the answer he links to a 2010 article in the "Prespacetime Journal" of which he is one of the editors and more prolific contributors. That article, written by Gibbs (which some editing pass managed to leave in a state where one finds both Einstein-Hilbert and Hilbert-Einstein and similar) [ETA: in 1997, see below] finds the right problem -- energy is very hard to define in a general curved spacetime <https://en.wikipedia.org/wiki/Mass_in_general_relativity#Def...>. It does not imho find the right solution. His is ultimately an attempt to define a quasilocal quantity and then extend it to some cosmologically large volume. His method requires a closed cosmology, and he had the decency to say so in the second paragraph. Consequently most people could simply stop reading at that point and spare themselves pp 906-907 where he admits that he's forced into considering coordinate-dependent quantities like everyone else (none of which he cited, more below), and misses the opportunity to back a quasilocal view with an ultralocal (if averaged) one. If he had done that he might have confronted the problem that in the far future of an accelerating expanding spacetime dark energy and horizon radiation are all that's left at a typical point in spacetime.
I agree with mr_mitm that dark energy doesn't make much qualitative difference with respect to energy losses from matter that just don't go anywhere (pace Gibbs). In an inertially expanding non-closed spacetime's far future you find no energy at all at a typical point, so vast vast regions appear to be flat vacuum. If the expansion is accelerated by dark energy, you get vacuum which isn't flat. It's best to consider this by comparing parallel trajectories, Raychaudhuri-style.
Consider two test (massless, non-interacting) particles having an initially-parallel trajectory at an adjacent pair of points in each version. We are setting up the parallel-ness at late times; as we just want to probe the late-time of an expanding universe their earlier configuration is unknown and not important here. These particles will stay parallel in the inertially expanding case, but will diverge in the accelerated expansion (cosmological constant) case.
Both of these cases conflict with Gibbs's stack exchange answer in the following way. Make our test particles massless, and apply the Blau-Frank-Weiss adaptation of Fermi coordinates to their worldlines; the affine parameter x+ along the null geodesics generates a pair of momenta k^\mu = \dot{x+}^\mu and orthogonal "transverse" accelerations a^mu = k^nu \nabla_nu k^mu = 0. The particles lose momentum in their direction of travel but feel no acceleration; they are simply in zero-force constant free fall. The cosmologies themselves pick out solutions of the geodesic equation, and the momentum-loss along null geodesics is because of the expansion of space. The test particles on their worldlines do not know whether the worldlines are parallel or divergent. Importantly, the geodesics are not "driven apart", they just are what they are in the spacetime.
Since we can solve the geodesic equations for the entire spacetime (as a "block universe") it is hard to imagine what one even means by an energy of the gravitational field, unless one slices up the spacetime into time-ordered spaces. But once you do that you have to guard against slicing-dependent quantities like those Gibbs contemplates. He starts, uncontroversially, with a slicing that contains the vast majority of actually-occupied timelike geodesics (the centres of masses of inertially drifting galaxy clusters, represented by the FLRW homogeneous fluids), but does not contemplate other slicings -- do the conclusions hold up for our pair of massless observers? No, his plan only works for for a family of timelike geodesics which were parallel at the termination of the inertial impulse or early in the the accelerated-expansion history. His conclusions also don't hold up in general for slicing along any accelerated massive observer's proper time either, and are super-awkward if we slice along a high-energy cosmic ray propagating from one galaxy cluster to another (e.g. if we wanted to think about its mean free path).
Gibbs's paper, dated 2010 [ETA: turns out to be written in 1997 but published 2010], cites work only up to the early 1990s, with 6/9 of his references dated before 1970. Any peer-review would demand he expand his list of references with the expectation he is or should be aware of work done in the fifteen year gap. I'll quote from the publication's editorial polcies page: "PSTJ employs a three-tier due diligence process in selecting submissions for publication. First, all submissions are screened by the Editor to determine whether the contents and/or forms are suitable for publication in PSTJ; and unsuitable submissions will be declined without reviews. Second, the remaining submissions will be reviewed by the Editor; and submissions passes Editor's review will be accepted for publications". Well, Gibbs is an Editor so maybe this paper didn't take the "Third, the still remaining articles ..." route. Who knows?
Honestly, I expected worse; he only fell into traps that were already in the academic literature and dealt with in grad-level GR textbooks. <https://en.wikipedia.org/wiki/ViXra> is well-known and "fringe" is polite". That said, this paper was fairly conventionally wrong.
[*] "Uphill" means against a gravitational potential. It is seductive in cosmology to think about gravitational potential and kinetic energy, especially if we drop dark energy. Early in the expanding universe masses like galaxy clusters are all relatively close and flying apart at high speed; at later times the masses are all relatively distant and flying apart at lower speed. The early kinetic energy has been converted into late gravitational potential. (Under time reversal, that gravitational potential energy crunches everything back together at high speed).
If we add dark energy then in the resulting accelerated expansion both the gravitational potential and kinetic energy increase with time. If the dark energy is the cosmological constant (CC), where is the extra kinetic energy coming from? The CC is constant at every place and every time. So there's an awfully big hint that energy isn't conserved, and digging into this one learns that the seductive idea doesn't work.
ETA: darn it, I didn't notice the "Note: this work was completed in January 1997" smooshed in after the author's correspondence address at the bottom of its first page. However, I would think the journal printing it thirteen years later would want to make its age more obvious and/or to publish a revision of the 1997 work. That said, two citations and a self-citation: <https://scholar.google.co.uk/scholar?cites=13647521487929411...>. If you want fringe, check out the mental causation paper there. With the exception in square brackets I added above, I don't think the 1997 vs 2010 date of authorship vs date of publication makes much difference to my comment.
So, uhhm, let's look at the
> accepted solution in the second link
which was authored by the hagiographic https://www.vixrapedia.org/wiki/Philip_Gibbs (in which there's a whole section "Energy Conservation in General Relativity": "... Gibbs is the leader of a small minority of commentators who dispute [that energy conservation only works in special cases]".
In the comments below the answer he links to a 2010 article in the "Prespacetime Journal" of which he is one of the editors and more prolific contributors. That article, written by Gibbs (which some editing pass managed to leave in a state where one finds both Einstein-Hilbert and Hilbert-Einstein and similar) [ETA: in 1997, see below] finds the right problem -- energy is very hard to define in a general curved spacetime <https://en.wikipedia.org/wiki/Mass_in_general_relativity#Def...>. It does not imho find the right solution. His is ultimately an attempt to define a quasilocal quantity and then extend it to some cosmologically large volume. His method requires a closed cosmology, and he had the decency to say so in the second paragraph. Consequently most people could simply stop reading at that point and spare themselves pp 906-907 where he admits that he's forced into considering coordinate-dependent quantities like everyone else (none of which he cited, more below), and misses the opportunity to back a quasilocal view with an ultralocal (if averaged) one. If he had done that he might have confronted the problem that in the far future of an accelerating expanding spacetime dark energy and horizon radiation are all that's left at a typical point in spacetime.
I agree with mr_mitm that dark energy doesn't make much qualitative difference with respect to energy losses from matter that just don't go anywhere (pace Gibbs). In an inertially expanding non-closed spacetime's far future you find no energy at all at a typical point, so vast vast regions appear to be flat vacuum. If the expansion is accelerated by dark energy, you get vacuum which isn't flat. It's best to consider this by comparing parallel trajectories, Raychaudhuri-style.
Consider two test (massless, non-interacting) particles having an initially-parallel trajectory at an adjacent pair of points in each version. We are setting up the parallel-ness at late times; as we just want to probe the late-time of an expanding universe their earlier configuration is unknown and not important here. These particles will stay parallel in the inertially expanding case, but will diverge in the accelerated expansion (cosmological constant) case.
Both of these cases conflict with Gibbs's stack exchange answer in the following way. Make our test particles massless, and apply the Blau-Frank-Weiss adaptation of Fermi coordinates to their worldlines; the affine parameter x+ along the null geodesics generates a pair of momenta k^\mu = \dot{x+}^\mu and orthogonal "transverse" accelerations a^mu = k^nu \nabla_nu k^mu = 0. The particles lose momentum in their direction of travel but feel no acceleration; they are simply in zero-force constant free fall. The cosmologies themselves pick out solutions of the geodesic equation, and the momentum-loss along null geodesics is because of the expansion of space. The test particles on their worldlines do not know whether the worldlines are parallel or divergent. Importantly, the geodesics are not "driven apart", they just are what they are in the spacetime.
Since we can solve the geodesic equations for the entire spacetime (as a "block universe") it is hard to imagine what one even means by an energy of the gravitational field, unless one slices up the spacetime into time-ordered spaces. But once you do that you have to guard against slicing-dependent quantities like those Gibbs contemplates. He starts, uncontroversially, with a slicing that contains the vast majority of actually-occupied timelike geodesics (the centres of masses of inertially drifting galaxy clusters, represented by the FLRW homogeneous fluids), but does not contemplate other slicings -- do the conclusions hold up for our pair of massless observers? No, his plan only works for for a family of timelike geodesics which were parallel at the termination of the inertial impulse or early in the the accelerated-expansion history. His conclusions also don't hold up in general for slicing along any accelerated massive observer's proper time either, and are super-awkward if we slice along a high-energy cosmic ray propagating from one galaxy cluster to another (e.g. if we wanted to think about its mean free path).
Gibbs's paper, dated 2010 [ETA: turns out to be written in 1997 but published 2010], cites work only up to the early 1990s, with 6/9 of his references dated before 1970. Any peer-review would demand he expand his list of references with the expectation he is or should be aware of work done in the fifteen year gap. I'll quote from the publication's editorial polcies page: "PSTJ employs a three-tier due diligence process in selecting submissions for publication. First, all submissions are screened by the Editor to determine whether the contents and/or forms are suitable for publication in PSTJ; and unsuitable submissions will be declined without reviews. Second, the remaining submissions will be reviewed by the Editor; and submissions passes Editor's review will be accepted for publications". Well, Gibbs is an Editor so maybe this paper didn't take the "Third, the still remaining articles ..." route. Who knows?
Honestly, I expected worse; he only fell into traps that were already in the academic literature and dealt with in grad-level GR textbooks. <https://en.wikipedia.org/wiki/ViXra> is well-known and "fringe" is polite". That said, this paper was fairly conventionally wrong.
[*] "Uphill" means against a gravitational potential. It is seductive in cosmology to think about gravitational potential and kinetic energy, especially if we drop dark energy. Early in the expanding universe masses like galaxy clusters are all relatively close and flying apart at high speed; at later times the masses are all relatively distant and flying apart at lower speed. The early kinetic energy has been converted into late gravitational potential. (Under time reversal, that gravitational potential energy crunches everything back together at high speed).
If we add dark energy then in the resulting accelerated expansion both the gravitational potential and kinetic energy increase with time. If the dark energy is the cosmological constant (CC), where is the extra kinetic energy coming from? The CC is constant at every place and every time. So there's an awfully big hint that energy isn't conserved, and digging into this one learns that the seductive idea doesn't work.
ETA: darn it, I didn't notice the "Note: this work was completed in January 1997" smooshed in after the author's correspondence address at the bottom of its first page. However, I would think the journal printing it thirteen years later would want to make its age more obvious and/or to publish a revision of the 1997 work. That said, two citations and a self-citation: <https://scholar.google.co.uk/scholar?cites=13647521487929411...>. If you want fringe, check out the mental causation paper there. With the exception in square brackets I added above, I don't think the 1997 vs 2010 date of authorship vs date of publication makes much difference to my comment.
You say
> Obviously the guy in the video was making the implicit assumption that we are talking about local experiments.
And yet this is not discussed by Steve. And that "obviousness" and "implicitness" is your particular take.
I like Steve. I think he has an approach that is both entertaining and educational. But like all educators, he can miss certain things. Unlike certain other science educators though, he does a far better job of providing explanation.
> Obviously the guy in the video was making the implicit assumption that we are talking about local experiments.
And yet this is not discussed by Steve. And that "obviousness" and "implicitness" is your particular take.
I like Steve. I think he has an approach that is both entertaining and educational. But like all educators, he can miss certain things. Unlike certain other science educators though, he does a far better job of providing explanation.
What makes you think dark energy is "a means of creating a perpetual motion envrionment" though? I've never heard that claim made.
I mean personally I think the theory of dark matter / energy is a patch for the perceptions not matching up with the theories, but that's besides the point.
I mean personally I think the theory of dark matter / energy is a patch for the perceptions not matching up with the theories, but that's besides the point.
If you listen to some of the experts (professional scientists) about the matter, their language gets very iffy very quickly. Especially when they says things like "dark energy driving the expansion of the universe at a faster rate". The implication is that "dark energy" is causing an increase in motion without generating waste energy.
What I find amusing though is the down vote. People don't seem to see the incongruity of the statements being made by these professional scientists and when something is sarcastically pointed out they just don't get it. In many ways, I think people have lost a sense of human about these matters and take themselves far too seriously.
As for dark energy/dark matter being a patch, I would wholeheartedly agree. I suspect that we will see more and more anomalies appear to cause either more additions or a fundamental change to occur in how we describe the universe as we see it.
It is fun to watch what is currently happening over very different fields of scientific investigation. I am thankful that I do not have to ascribe to any particular view as retirement, so to speak, allows me to read up and consider whatever fields take my interest at any point in time.
What I find amusing though is the down vote. People don't seem to see the incongruity of the statements being made by these professional scientists and when something is sarcastically pointed out they just don't get it. In many ways, I think people have lost a sense of human about these matters and take themselves far too seriously.
As for dark energy/dark matter being a patch, I would wholeheartedly agree. I suspect that we will see more and more anomalies appear to cause either more additions or a fundamental change to occur in how we describe the universe as we see it.
It is fun to watch what is currently happening over very different fields of scientific investigation. I am thankful that I do not have to ascribe to any particular view as retirement, so to speak, allows me to read up and consider whatever fields take my interest at any point in time.
You are being pedantic.
If you want to consider dark energy perpetual motion, sure, but then it's excluded from the "we know that perpetual motion is not possible" rule.
"we know that perpetual motion is not possible" is based on the fact that you can't break the laws of physics, which perpetual motion is doing, but if dark energy is part of physics, it can't break those laws by definition.
If you want to consider dark energy perpetual motion, sure, but then it's excluded from the "we know that perpetual motion is not possible" rule.
"we know that perpetual motion is not possible" is based on the fact that you can't break the laws of physics, which perpetual motion is doing, but if dark energy is part of physics, it can't break those laws by definition.
When you say
> If you want to consider dark energy perpetual motion, sure, but then it's excluded from the "we know that perpetual motion is not possible" rule.
That's the incongruity here. You can hedge it around in various ways, but it is still an incongruity, which was my point. I personally do not believe in any perpetual motion mechanism and I find the "dark energy" concept to be in that same set of mechanisms.
I somehow think that we will see soon enough a new set of theories and models that have a better explanatory power that what we see being expressed today in cosmology. How long? Don't know. But I suspect it won't be too far away. I think the same thing will happen in regards to the Standard Model.
What the fun will be is seeing what comes up. Hopefully people will be able to laugh at themselves when it arrives - though I don't think that this will happen. Too many people take themselves too seriously over these kinds of matters instead of dealing with the matters that really matter.
> If you want to consider dark energy perpetual motion, sure, but then it's excluded from the "we know that perpetual motion is not possible" rule.
That's the incongruity here. You can hedge it around in various ways, but it is still an incongruity, which was my point. I personally do not believe in any perpetual motion mechanism and I find the "dark energy" concept to be in that same set of mechanisms.
I somehow think that we will see soon enough a new set of theories and models that have a better explanatory power that what we see being expressed today in cosmology. How long? Don't know. But I suspect it won't be too far away. I think the same thing will happen in regards to the Standard Model.
What the fun will be is seeing what comes up. Hopefully people will be able to laugh at themselves when it arrives - though I don't think that this will happen. Too many people take themselves too seriously over these kinds of matters instead of dealing with the matters that really matter.
There are other forms of "perpetual motion" energy in physics:
https://en.wikipedia.org/wiki/Zero-point_energy
https://en.wikipedia.org/wiki/Zero-point_energy
You reference the Zero-point energy article on wikipedia. What is interesting is the following quote from the very first paragraph of that article
> if it is to be Lorentz invariant such that there is no contradiction with Einstein's theory of special relativity
Here we see that the article references Special Relativity which is actually at odds with General Relativity.
We can then say one of the following things:
1) Special Relativity and General Relativity are only approximations to reality and you have to be very careful when and where you apply each theory.
2) Special Relativity and General Relativity are both wrong
3) Special Relativity is correct and General Relativity is wrong
4) General Relativity is correct and Special Relativity is wrong
What you cannot do is say that both are correct theories as the fundamental basis of each in regards to space/time are quite different.
This leads to an incongruity if you think both are correct.
Now back to Zero-point energy. The problem here is that you have to be able to measure this effect and not just have it arise from theory in a manner that cannot be measured.
This comes back to the place of determining whether or not "dark energy" is or can be the basis of "perpetual motion machines". Since I don't believe that such an entity actually exists, I also don't think that we have any possibility of any sort of perpetual motion per se.
There are many incongruities in our modern suite of theories. It is just that many people (especially professional scientists) turn a blind eye to those incongruities. These incongruities are a sign that our theories are very much incomplete and possibly very wrong.
From the perspective of looking at the history of scientific investigation, I think we are back to a time similar to when the epicycle models were used to describe what was being seen (an example of Fourier series) and we are now ready for a new Copernican revolution. The dogma in science education is reminiscent of those times.
> if it is to be Lorentz invariant such that there is no contradiction with Einstein's theory of special relativity
Here we see that the article references Special Relativity which is actually at odds with General Relativity.
We can then say one of the following things:
1) Special Relativity and General Relativity are only approximations to reality and you have to be very careful when and where you apply each theory.
2) Special Relativity and General Relativity are both wrong
3) Special Relativity is correct and General Relativity is wrong
4) General Relativity is correct and Special Relativity is wrong
What you cannot do is say that both are correct theories as the fundamental basis of each in regards to space/time are quite different.
This leads to an incongruity if you think both are correct.
Now back to Zero-point energy. The problem here is that you have to be able to measure this effect and not just have it arise from theory in a manner that cannot be measured.
This comes back to the place of determining whether or not "dark energy" is or can be the basis of "perpetual motion machines". Since I don't believe that such an entity actually exists, I also don't think that we have any possibility of any sort of perpetual motion per se.
There are many incongruities in our modern suite of theories. It is just that many people (especially professional scientists) turn a blind eye to those incongruities. These incongruities are a sign that our theories are very much incomplete and possibly very wrong.
From the perspective of looking at the history of scientific investigation, I think we are back to a time similar to when the epicycle models were used to describe what was being seen (an example of Fourier series) and we are now ready for a new Copernican revolution. The dogma in science education is reminiscent of those times.
The universe is in perpetual motion. This is a process that has been being refined since the very beginning.
Our ability to harness it and use it for our own intentions, not so much.
We don't have an energy problem.
We have an energy management problem - we are harvesting only the coarsest of it all, when we could be harvesting the finest, most refined of it, that is all around us ..
Our ability to harness it and use it for our own intentions, not so much.
We don't have an energy problem.
We have an energy management problem - we are harvesting only the coarsest of it all, when we could be harvesting the finest, most refined of it, that is all around us ..
Loved his parody of the fixed grin of Technology Connections.