Rotating Black Holes May Serve as Gentle Portals for Hyperspace Travel(theconversation.com)
theconversation.com
Rotating Black Holes May Serve as Gentle Portals for Hyperspace Travel
https://theconversation.com/rotating-black-holes-may-serve-as-gentle-portals-for-hyperspace-travel-107062
172 comments
I'm in a more conservative camp than speed limits: the practicality one.
Even if we ignore the ponies and rainbows of wormhole travel, if you want to travel to a plain black hole to use the magic teleporter, the nearest two are V616 Mon at 11 solar masses and 3000 LY away, and Cyg X1 at 15 SM and 6000 LY. If you buy into the article's assertion that you won't get burned or spaghettified on your way to becoming a nucleon paste, and you want a heavier BH, the nearest is Sag A* at 4.1e6 SM and 25000 LY away.
Anyway, to travel between the teleporter and Earth, we're talking most of the resources of a planet to accelerate a mass to substantial fractions of c. Then you've got thousands of years of collisions, radiation, and maybe (assumption?) cultural and biological challenges of living in space for aeons, plus needing another planet's worth of resources to slow down at the destination. All this makes it hard enough even to get a dozen LY to our nearest start system.
My opinion is we're in something of a Well World universe, where everyone is pretty well travel-isolated from their neighbors.
Even if we ignore the ponies and rainbows of wormhole travel, if you want to travel to a plain black hole to use the magic teleporter, the nearest two are V616 Mon at 11 solar masses and 3000 LY away, and Cyg X1 at 15 SM and 6000 LY. If you buy into the article's assertion that you won't get burned or spaghettified on your way to becoming a nucleon paste, and you want a heavier BH, the nearest is Sag A* at 4.1e6 SM and 25000 LY away.
Anyway, to travel between the teleporter and Earth, we're talking most of the resources of a planet to accelerate a mass to substantial fractions of c. Then you've got thousands of years of collisions, radiation, and maybe (assumption?) cultural and biological challenges of living in space for aeons, plus needing another planet's worth of resources to slow down at the destination. All this makes it hard enough even to get a dozen LY to our nearest start system.
My opinion is we're in something of a Well World universe, where everyone is pretty well travel-isolated from their neighbors.
I hear you, but I think colonizing the galaxy might still be feasible. If we can get to the point where we have the technology to colonize Mars, which will hopefully happen this century, then I would imagine it probably won't be long after that until we manage to have permanent space habitats that harvest materials from asteroids.
If we have fusion power, durable permanent space habitats, and the technology to harvest materials from asteroids, then traveling to the next star system doesn't seem so far-fetched anymore. If we could just reach 0.1c, we could make it to Alpha Centauri in less than 50 years. Once we make it there, if we're already comfortable living in space, we don't even need to worry about terraforming or anything lengthy and complicated like that, we can just harvest asteroids and build more space stations and ships.
Not a physicist, but I see Project Orion could have reached 0.33% of the speed of light. Would it be realistic to extend that design to accelerate to 0.1c?
If we have fusion power, durable permanent space habitats, and the technology to harvest materials from asteroids, then traveling to the next star system doesn't seem so far-fetched anymore. If we could just reach 0.1c, we could make it to Alpha Centauri in less than 50 years. Once we make it there, if we're already comfortable living in space, we don't even need to worry about terraforming or anything lengthy and complicated like that, we can just harvest asteroids and build more space stations and ships.
Not a physicist, but I see Project Orion could have reached 0.33% of the speed of light. Would it be realistic to extend that design to accelerate to 0.1c?
>If we can get to the point where we have the technology to colonize Mars, which will hopefully happen this century, then I would imagine it probably won't be long after that until we manage to have permanent space habitats that harvest materials from asteroids.
Bear in mind that we were certain colonizing Mars was just around the corner after landing on the Moon... about 60 years ago. In the interim, we lost the capability to land anything but probes beyond low earth orbit and are basically starting from scratch with private enterprise.
Not only is technological progress not always consistent, but it takes more time and effort to recover from regressions the further along the curve of advancement you happen to be. By which time, goals and priorities may have changed significantly to alter the trajectory of that progress.
So I would be wary of extrapolations that make it seem as if progress into space is like climbing a ladder. It seems more like building a Jenga tower as you climb it.
Bear in mind that we were certain colonizing Mars was just around the corner after landing on the Moon... about 60 years ago. In the interim, we lost the capability to land anything but probes beyond low earth orbit and are basically starting from scratch with private enterprise.
Not only is technological progress not always consistent, but it takes more time and effort to recover from regressions the further along the curve of advancement you happen to be. By which time, goals and priorities may have changed significantly to alter the trajectory of that progress.
So I would be wary of extrapolations that make it seem as if progress into space is like climbing a ladder. It seems more like building a Jenga tower as you climb it.
A few hundred years is nothing compared to the time the universe had habitable planets.
Civilizations don't operate on the scale of the universe, but on the scale of whatever constitutes the productive fraction of a single lifetime, and the influential span of a generation. Politics is more important to the rate of progress in this regard than physics.
If one civilization has existed over millions or billions of years it does.
Using hydrogen bombs you can get something like Project Orion to about 10% the speed of light, but not much faster. Project Daedalus is a more advanced design with the goal of accelerating an unmanned probe to 12% the speed of light [1]. The only somewhat practical ideas that seem to go beyond that involve antimatter fuel: not quite as easy to handle and well understood as nuclear bombs but certainly more attainable than giant black holes. There are a few designs that should allow travel at 60-80% the speed of light
1: https://en.wikipedia.org/wiki/Project_Daedalus
1: https://en.wikipedia.org/wiki/Project_Daedalus
Isn't fusion power a promising technology to provide the energy needed to accelerate (and decelerate) for a long time?
Not my area but I think the fuel is the problem, not the power source. Even a fusion-powered drive needs to spit something out the back to accelerate (e.g. ions), so you need to carry many kg of ionizable fuel.
It's possible, yes, but even getting to the next system will take an enormous amount of time and resources; I want to believe colonizing the galaxy is possible, but it'll become a very long, slow and expensive process. I mean we're talking tens of thousands of years; by the time humanity has covered a decent portion of our local cluster, its evolution - both physical and cultural - will become really divergent. I'm sure a science fiction writer has thought about this.
It's interesting to consider that maybe life on earth is in fact a colonization effort from long ago. Sending probes with the base ingredients for life across the universe millions of years ago might've been a survival strategy. It feels meaningless without information to go along with it, but it's likely that information has either been lost, forgotten, or attributed to early humans instead of something Out There.
It's interesting to consider that maybe life on earth is in fact a colonization effort from long ago. Sending probes with the base ingredients for life across the universe millions of years ago might've been a survival strategy. It feels meaningless without information to go along with it, but it's likely that information has either been lost, forgotten, or attributed to early humans instead of something Out There.
Accelerating to a fraction of c is no small feat. As per Tsiolkovsky rocket equation, growth in delta-v requires an exponenetial growth in fuel.
Not to mention all the fuel you'd need to decelerate so you can actually stop at your destination.
Not to mention all the fuel you'd need to decelerate so you can actually stop at your destination.
>>If we can get to the point where we have the technology to colonize Mars, which will hopefully happen this century, then I would imagine it probably won't be long after that until we manage to have permanent space habitats that harvest materials from asteroids.
We are already capable of that now. The issues are politics and economics and not science/engineering.
If I'm not wrong the USA spent like $1T on building a fighter plane, and something like double digits trillion dollars and ongoing on wars since the past 20 years alone.
You can mine asteroids for a part of that kind of budget already.
Going down gravity wells of planets makes no sense, space colonies are the way forward, and there is no shortage of resources in space for that.
We are already capable of that now. The issues are politics and economics and not science/engineering.
If I'm not wrong the USA spent like $1T on building a fighter plane, and something like double digits trillion dollars and ongoing on wars since the past 20 years alone.
You can mine asteroids for a part of that kind of budget already.
Going down gravity wells of planets makes no sense, space colonies are the way forward, and there is no shortage of resources in space for that.
> the nearest two are V616 Mon at 11 solar masses and 3000 LY away, and Cyg X1 at 15 SM and 6000 LY.
The nearest known ones, that is. They were detected due to their gravitational effect on binary companions we could more easily detect. By that token, it is quite possible there are nearer ones - it's just that detecting them directly if they don't have a binary companion is tough.
The nearest known ones, that is. They were detected due to their gravitational effect on binary companions we could more easily detect. By that token, it is quite possible there are nearer ones - it's just that detecting them directly if they don't have a binary companion is tough.
Could be one on a collision course with us right now.
Very interesting, but this assumes life evolves to Type II civ.
I mean, looking at our own planet, it seems this might be extremely unlikely.
To the best of my knowledge, another Planet Earth could possibly be within a few hundred ly of us(0.000000001 of known universe), and we'd have no idea(1)..?
1-https://www.centauri-dreams.org/2012/05/31/is-our-civilizati...
I mean, looking at our own planet, it seems this might be extremely unlikely.
To the best of my knowledge, another Planet Earth could possibly be within a few hundred ly of us(0.000000001 of known universe), and we'd have no idea(1)..?
1-https://www.centauri-dreams.org/2012/05/31/is-our-civilizati...
Artificially creating microscopic black holes is not extremely difficult [1], and after that you can "just" feed them a few stars. Probably you can harvest them while travelling less than 25000 LY.
[1] Section V of this paper https://arxiv.org/abs/0908.1803
[1] Section V of this paper https://arxiv.org/abs/0908.1803
You can feed 1 star into 1 BH.
>> My opinion is we're in something of a Well World universe, where everyone is pretty well travel-isolated from their neighbors.
Let us hope so.
Let us hope so.
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The author didn't mention using black holes to get around. Hyperspace might be just moving into wherever the events in the movie Event Horizon took place.
Isn't Event Horizon basically just a horror movie, except the haunted house is a spaceship?
If you're going to pick a fictional hyperspace "framework," there are many to choose from, all of which are equally nonsensical.
If you're going to pick a fictional hyperspace "framework," there are many to choose from, all of which are equally nonsensical.
>He contends that there likely isn't a sentient civilization within about a billion light years of us because the signature of Dyson spheres would be unmistabkable and unmissable.
How do we know an advanced technology would absolutely use Dyson spheres?
I'm not asking to challenge but in serious inquiry. Off the top of my head it just seems a highly advanced civilization might be able to come up with something completely different to meet their energy needs.
How do we know an advanced technology would absolutely use Dyson spheres?
I'm not asking to challenge but in serious inquiry. Off the top of my head it just seems a highly advanced civilization might be able to come up with something completely different to meet their energy needs.
> How do we know an advanced technology would absolutely use Dyson spheres?
This depends on what question you're trying to answer.
The Fermi Paradox is a good one because you don't need to ask "would a civilization always use Dyson spheres?" It takes just one to use them within a billion years to be a sufficient counterexample. Would they be universally used? Who knows?
Dyson spheres are such an attractive idea because there's no new physics required here (like negative mass for wormholes and warp drives). It's largely just an engineering problem. Now it does require a fairly economical method of getting off-world but all of this seems relatively likely within the next 100-200 years.
So it's (relatively) low tech and attractive in terms of providing living area for unit mass (many, many orders of magnitudes better than living on planets).
It's worth noting that you don't even need nuclear fusion to make this all work (although that makes it much easier) and it's not a given that we'll have practical nuclear fusion.
If you don't have nuclear fusion, what is your energy source? The alternatives other than harnessing solar output are much, much higher technologies like using black holes (which is also theorized about as a starship drive).
This depends on what question you're trying to answer.
The Fermi Paradox is a good one because you don't need to ask "would a civilization always use Dyson spheres?" It takes just one to use them within a billion years to be a sufficient counterexample. Would they be universally used? Who knows?
Dyson spheres are such an attractive idea because there's no new physics required here (like negative mass for wormholes and warp drives). It's largely just an engineering problem. Now it does require a fairly economical method of getting off-world but all of this seems relatively likely within the next 100-200 years.
So it's (relatively) low tech and attractive in terms of providing living area for unit mass (many, many orders of magnitudes better than living on planets).
It's worth noting that you don't even need nuclear fusion to make this all work (although that makes it much easier) and it's not a given that we'll have practical nuclear fusion.
If you don't have nuclear fusion, what is your energy source? The alternatives other than harnessing solar output are much, much higher technologies like using black holes (which is also theorized about as a starship drive).
If the goal is living area and capturing solar energy, wouldn't most civilisations start out with a dyson ring instead of a full sphere? Making a ring seems easier structurally (everything is in a very similar orbit, so less forces on the structure) and requires vastly less material, so it's much easier to get started. And once the ring is a few thousand kilometers wide the civilisation might not need more space (either because population and energy needs level off or because other solar systems are more enticing for expansion, or simply because the civilisation collapes eventually).
To me it seems that if you take an infinite number of civilisations, you should find a lot of rings and barely any full spheres. But a ring is a lot harder to detect: if it blocks the star from our point of view it's as obvious as a dyson sphere, but in most orientations it would be seen as a very thin band that radiates much less energy than the parent star, making it basically impossible to detect with current technology (none of our methods of finding exoplanets seems applicable, and emissions would be too low to be seen directly)
To me it seems that if you take an infinite number of civilisations, you should find a lot of rings and barely any full spheres. But a ring is a lot harder to detect: if it blocks the star from our point of view it's as obvious as a dyson sphere, but in most orientations it would be seen as a very thin band that radiates much less energy than the parent star, making it basically impossible to detect with current technology (none of our methods of finding exoplanets seems applicable, and emissions would be too low to be seen directly)
As I replied in another thread, a Dyson sphere in its original intent was a swarm of habitats, not a rigid shell. No known material is strong enough to support that.
What you're talking about I think is a ringworld, popularized by Larry Niven's "Ringworld" series. They have the same problem a Dyson shell does: the centrifugal force would tear the ring apart and there's no known material that could handle that.
A Dyson swarm has basically all the advantages of living area a shell or ring does with none of the material problems. It can also be built incrementally, one habitat at a time. And that too is important.
This is why a Dyson swarm is seen by many futurists as near inevitable:
- Can be built out of modern materials like stainless steel
- Can be built incrementally, one habitat at a time
- Is orders of magnitude more efficient in terms of living area per unit mass than planets
- It avoids large gravity wells, which are a problem for getting off planets
- It can take advantage of the full energy output of a star
What you're talking about I think is a ringworld, popularized by Larry Niven's "Ringworld" series. They have the same problem a Dyson shell does: the centrifugal force would tear the ring apart and there's no known material that could handle that.
A Dyson swarm has basically all the advantages of living area a shell or ring does with none of the material problems. It can also be built incrementally, one habitat at a time. And that too is important.
This is why a Dyson swarm is seen by many futurists as near inevitable:
- Can be built out of modern materials like stainless steel
- Can be built incrementally, one habitat at a time
- Is orders of magnitude more efficient in terms of living area per unit mass than planets
- It avoids large gravity wells, which are a problem for getting off planets
- It can take advantage of the full energy output of a star
At any fixed distance from the sun there's only one speed where you have a stable spherical orbit. Since actual spheres have poles that don't move much at all, any dyson swarm that approaches a sphere has to consist of parts in a number of different orbits. That's inconvinient for a whole host of reasons (sun often occluded as segments move below you, movement between segments is difficult etc.). In comparison a swarm that looks like a narrow ring has no such problem: everything is approximately at the same speed while traveling in the same direction. For that reason alone rings are the superior choice regardless if your structure is solid or a swarm of independend objects.
Maybe multiple rings would form for political reasons, but that just makes the individual rings proportionally thinner.
Maybe multiple rings would form for political reasons, but that just makes the individual rings proportionally thinner.
I was under the impression that Dyson sphere participants would be mainly heliostats, whose station would be kept by balancing their inward gravitational attraction against the outward pressure from reflected or decelerated solar wind.
Whenever an object would intersect the sphere, the nearest heliostats alter the angle of their mirrors/sails to drift away and make a hole. Then they drift back to close it after it passes.
There's nothing to say that they can't also have an orbital velocity component, as it takes quite a lot of delta-v to decelerate from a near-circular solar orbit, and orbital velocity can make up for lack of sail area.
Whenever an object would intersect the sphere, the nearest heliostats alter the angle of their mirrors/sails to drift away and make a hole. Then they drift back to close it after it passes.
There's nothing to say that they can't also have an orbital velocity component, as it takes quite a lot of delta-v to decelerate from a near-circular solar orbit, and orbital velocity can make up for lack of sail area.
Dyson Spheres are not solid objects; they're swarms. https://www.youtube.com/watch?v=pP44EPBMb8A&t=331s
> Now it does require a fairly economical method of getting off-world but all of this seems relatively likely within the next 100-200 years.
Not if our brightest minds are trying to make people click more ads.
I think I finally know the answer to the Fermi Paradox.
Not if our brightest minds are trying to make people click more ads.
I think I finally know the answer to the Fermi Paradox.
...no new physics required...
Is this true? The mass required would generate forces that would rip apart any materials we've encountered. A Dyson belt could just be in some unstable sort of orbit, but a Dyson sphere has to be strong enough to hold itself in shape.
Is this true? The mass required would generate forces that would rip apart any materials we've encountered. A Dyson belt could just be in some unstable sort of orbit, but a Dyson sphere has to be strong enough to hold itself in shape.
"Dyson sphere" is a misnomer in that at some point this was conflated to mean a shell than physically encompasses a star. That was never the original meaning or intent, which is why some people (including Isaac Arthur) prefer the term "Dyson swarm" as being true to the original idea and clear in intent.
A Dyson sphere/swarm is simple a sufficient cloud of habitats orbiting the star as to essentially block out the vast majority of its light, kind of like how droplets of water block light in a fog.
A Dyson sphere/swarm is simple a sufficient cloud of habitats orbiting the star as to essentially block out the vast majority of its light, kind of like how droplets of water block light in a fog.
This feels like it would violate the hairy ball theorem, no?
https://en.wikipedia.org/wiki/Hairy_ball_theorem
https://en.wikipedia.org/wiki/Hairy_ball_theorem
No, for one you can only orbit in an ellipse around the center of mass. You can only "comb" in a direction that takes you around the middle of the ball. The major difference though, is that you can have overlapping orbits. There is no way to cover the entire surface without overlapping because of this, but you can still cover everything if you're willing to pay a price in efficiency by having portions of the constellation shade one another.
Hmm, but it feels like a good tradeoff in marginal increase in total energy caught versus marginal decrease in efficiency would get you pretty far from 100% coverage.
The satellites of the swarm don't have be at the same distance from the star and the orbits can overlap.
Flying cars were in our imagination but never materialized (and probably never will).
Why would an advanced alien civilization be bound to the limits 21st century human engineering and physics?
They wouldn't be. We limit ourselves to current or near current technology for these analysis or you can easily get into the realms of hypotheticals very easily. If you say that the laws of thermodynamics don't apply to aliens because they have more advanced physics then the sky becomes the limit. So you have to stick by your own rule book when you imagine, so it'd be more appropriate to say that there is unlikely to be Dyson swarms near us that were built by aliens with a similar understanding of physics. For all we know the popular way that they gather energy is harvesting photons from within the star itself, stick a giant straw into a star and just drink away the photons.
I'm not suggesting that we speculate into high fantasy. What I'm getting at is that we can't come to a conclusion about whether advance civilizations exist or what they might look like to us. So quite the opposite of realms of hypotheticals really.
That's very clear. Thank you for your response.
If a civilization has portable nuclear fusion (plug your spaceship into a suitcase for power), then there's no reason to hang out near a star. People living inland never think about how to obtain salt anymore.
Nuclear fusion is not magic infinite energy; the amount produced is limited by the amount of fuel being used. I mean how much power is generated from fusion anyway? Especially at the scale (suitcase) you mentioned?
I dunno where your remark about salt comes from either; a lot of salt intended for consumption is dug up from the ground (salt mines).
I dunno where your remark about salt comes from either; a lot of salt intended for consumption is dug up from the ground (salt mines).
If you want to use vastly more energy than a portable fusion reactor can provide, the nearest star is probably the best place to get it.
They’d have to collect fuel from somewhere…
From space for example:
https://en.wikipedia.org/wiki/Bussard_ramjet
https://en.wikipedia.org/wiki/Bussard_ramjet
It would have to violate the laws of thermodynamics to not be visible. I’m not saying “no” (my brother has wondered if dark energy could be waste output of such civilisations, for example), but we have zero reason to treat the idea as anything more than the softest of science fiction.
Of course if we’re talking about an FTL-capable civilization then our understanding of physics is out of the window to begin with. I don’t think it’s reasonable to expect a civilization with FTL to make Dyson spheres or swarms, and it may be thst even if FTL is impossible it could be I desirable to build them. If the need to hide distinct technosignatures for some reason (Dark Forest perhaps) then any civilization would avoid Dyson structures.
FTL makes it worse. The only tech we need for us to Dyson up (95%?) of our entire visible light cone is self-replicating factories that work in a vacuum on (for example) Mercury: http://ukspace2015.co.uk/presentations/36
FTL makes that 100%, from beyond out cosmic horizons, even if it turns out that FTL isn’t automatically also a time machine like we currently think it is.
Pocket universes might help? I don’t know though, I’m saying that only because I’ve not seen them ruled out.
FTL makes that 100%, from beyond out cosmic horizons, even if it turns out that FTL isn’t automatically also a time machine like we currently think it is.
Pocket universes might help? I don’t know though, I’m saying that only because I’ve not seen them ruled out.
The GP didn't ask how you would make a Dyson sphere that was invisible, but why it was certain the Dyson sphere would be built at all.
Ok, but the effect of the energy output of any civilisation is basically the same, and for the same reasons. It doesn’t matter if it’s a star or TARDIS whose inside is eternally expanding and you’re grabbing energy from its internal dark energy field, if you use that energy, you get hot, and that heat is visible.
Unless you can violate the laws of thermodynamics.
Unless you can violate the laws of thermodynamics.
I wonder if advanced civilizations would use a lot of energy?
We always imagine they have very advanced physics and engineering, to do things like take apart planets to build mega-structures and things like that, but usually don't think about their other sciences.
My guess is that by the time they have gotten that far in physics, they have also gotten way ahead of us in biology. They'll have wiped out disease and illness, stopped aging, and only die by choice or accident. They'll have figured out geology and ecology and climatology and psychology.
I suspect that the final steady state for most civilizations that don't end up wiping themselves out by doing something stupid is a relatively small (by our standards) population of essentially immortal beings, living on a world they have restored to a largely pre-civilization state, using less energy by far that we are using but using it way more efficiently.
We always imagine they have very advanced physics and engineering, to do things like take apart planets to build mega-structures and things like that, but usually don't think about their other sciences.
My guess is that by the time they have gotten that far in physics, they have also gotten way ahead of us in biology. They'll have wiped out disease and illness, stopped aging, and only die by choice or accident. They'll have figured out geology and ecology and climatology and psychology.
I suspect that the final steady state for most civilizations that don't end up wiping themselves out by doing something stupid is a relatively small (by our standards) population of essentially immortal beings, living on a world they have restored to a largely pre-civilization state, using less energy by far that we are using but using it way more efficiently.
Maybe collect the heat and release it as a laser towards very sparsely populated parts of the sky? Perhaps that helps stabilize the sphere in the orbit of its star?
A Dyson Sphere is not a solid object. Instead, it's many small objects each of which is in a stable orbit. https://www.youtube.com/watch?v=pP44EPBMb8A&t=331s
Also, a huge laser can certainly direct energy in a direction that nobody will notice. Unfortunately, creating the laser beam also creates waste heat, and that waste heat can be seen. Even collecting waste heat generates waste heat that you cannot collect.
On the other hand, if you want a huge laser for some other purpose (such as vaporizing distant planets), then a Dyson Sphere is the ideal way to create one.
https://groups.google.com/forum/#!msg/sci.space.tech/uh5iB9X...
Also, a huge laser can certainly direct energy in a direction that nobody will notice. Unfortunately, creating the laser beam also creates waste heat, and that waste heat can be seen. Even collecting waste heat generates waste heat that you cannot collect.
On the other hand, if you want a huge laser for some other purpose (such as vaporizing distant planets), then a Dyson Sphere is the ideal way to create one.
https://groups.google.com/forum/#!msg/sci.space.tech/uh5iB9X...
> A Dyson Sphere is not a solid object. Instead, it's many small objects each of which is in a stable orbit.
Actually, we've never seen one so we have no idea how one might be engineered! It could for example be a "fog" of worlds that extends out past several local AU and to us would look nothing more like a dust cloud obscuring their local star. There wouldn't be a telltale signal of a Dyson Sphere, just another star with a big dust cloud.
Imagine a civilization like this, those closer to the star get more power literally, and those on the outskirts and in the shadows of the other worlds become dependent on the more inner worlds to re-radiate their absorbed energy, or to condense and lase the energy outwards to the shadow worlds...at some cost that limitless free energy can't pay for.
Beyond some distance the worlds become so cold that the inhabitants freeze to death and exile of your entire world at the whims of the inners becomes a real punishment. Dead worlds are recycled for mass for the growing population of the inners, or repurposed for other things.
There are billions of such worlds. Perhaps they are customarily shaped as small ringworlds and rotate in a complex manner to produce gravity and a daynight cycle. Dead or frozen worlds may have a reflective sail hoisted along the inner opening and expeditionary generation ships are sent out to nearby stars powered by lasers collected from hundreds of inner worlds.
Successful colonies may start to immediate transform the mass of nearby planetary systems into new "dust" clouds rather than settle on the planetary surfaces. Many adjacent Dyson spheres may look to us like just interstellar gases between several stars containing an unusual amount of organic molecules but could be the exchange of trillions of generation ships moving mass and energy back and forth between stars.
Such a civilization could eventually become nomadic in a way, moving from star to star as they burn out, leaving behind frozen husks of trillions of dead ringworlds.
Actually, we've never seen one so we have no idea how one might be engineered! It could for example be a "fog" of worlds that extends out past several local AU and to us would look nothing more like a dust cloud obscuring their local star. There wouldn't be a telltale signal of a Dyson Sphere, just another star with a big dust cloud.
Imagine a civilization like this, those closer to the star get more power literally, and those on the outskirts and in the shadows of the other worlds become dependent on the more inner worlds to re-radiate their absorbed energy, or to condense and lase the energy outwards to the shadow worlds...at some cost that limitless free energy can't pay for.
Beyond some distance the worlds become so cold that the inhabitants freeze to death and exile of your entire world at the whims of the inners becomes a real punishment. Dead worlds are recycled for mass for the growing population of the inners, or repurposed for other things.
There are billions of such worlds. Perhaps they are customarily shaped as small ringworlds and rotate in a complex manner to produce gravity and a daynight cycle. Dead or frozen worlds may have a reflective sail hoisted along the inner opening and expeditionary generation ships are sent out to nearby stars powered by lasers collected from hundreds of inner worlds.
Successful colonies may start to immediate transform the mass of nearby planetary systems into new "dust" clouds rather than settle on the planetary surfaces. Many adjacent Dyson spheres may look to us like just interstellar gases between several stars containing an unusual amount of organic molecules but could be the exchange of trillions of generation ships moving mass and energy back and forth between stars.
Such a civilization could eventually become nomadic in a way, moving from star to star as they burn out, leaving behind frozen husks of trillions of dead ringworlds.
It doesn't really matter how it's built; all the waste heat will be visible and the short-wavelength light won't be.
There is Larry Niven's Ringworld [0], which proposes a ring instead of a sphere.
0.https://en.wikipedia.org/wiki/Ringworld
0.https://en.wikipedia.org/wiki/Ringworld
It also sounds logical: why would you waste energy by radiating it if you can retain it?
It's also a waste of energy to work to capture energy you don't intend to use. Using less energy more efficiently is also logical.
The rotation matters because the singularity of a rotating black hole is ring-shaped, not a point: https://en.wikipedia.org/wiki/Ring_singularity
> I'm not sure why the author is talking about gravity ripping you apart in a black hole. It Is Known [tm] that larger black holes have pretty gentle event horizons.
But the article isn't about what happens at the event horizon. It's about what happens at the singularity, well inside of the event horizon for astrophysical black holes.
But the article isn't about what happens at the event horizon. It's about what happens at the singularity, well inside of the event horizon for astrophysical black holes.
> He contends that there likely isn't a sentient civilization within about a billion light years of us because the signature of Dyson spheres would be unmistabkable and unmissable.
Or that making a dyson sphere is harder than FTL, or it isn't economically viable to build one. There's no reason to assume a Dyson sphere would be a logical step after achieving FTL
Or that making a dyson sphere is harder than FTL, or it isn't economically viable to build one. There's no reason to assume a Dyson sphere would be a logical step after achieving FTL
>>Put me firmly in the camp that believes the speed of light is a hard limit on the universe and I'll use Isaac Arthur dismissal of FTL travel as to why.
I would modify your sentence to say that the speed of light is a hard limit through space. Space on the other hand does not seem to have that limitation [1]
[1] https://en.wikipedia.org/wiki/Alcubierre_drive
I would modify your sentence to say that the speed of light is a hard limit through space. Space on the other hand does not seem to have that limitation [1]
[1] https://en.wikipedia.org/wiki/Alcubierre_drive
The Alcubierre drive is a fantasy. It's the equivalent of saying "I can start a business selling unicorn rides if I have a unicorn." The unicorn in this case being "negative mass", there being no way to synthesize such a thing nor even a plausible path by which it might be possible.
We know for a fact that it is possible for space to expand because we have observed that space is expanding. Who knows why or how, or if it should be called “negative mass” or “dark energy,” but observing a phenomenon has always been the starting point for exploiting it. Radiation started out as a small unexplained observation too and look what we’ve done with that.
I’m not claiming that the warp drive is around the corner, I’m just saying: we do not yet know enough to rule it out.
I’m not claiming that the warp drive is around the corner, I’m just saying: we do not yet know enough to rule it out.
This is an interesting perspective! The frontier around dark energy / space accelerating in its expansion etc is interesting to me.
A bit unrelated, my pet theory is that a dwindling of some quantity creates the things we're measuring as acceleration. My naive intuition is that celestial bodies aren't flying away from each other accelerated by some unseen energy so much as getting smaller. If two things shrink in place, the distance between them grows.
Maybe there's some obvious reason why that couldn't be the case, i'd be interested to know!
A bit unrelated, my pet theory is that a dwindling of some quantity creates the things we're measuring as acceleration. My naive intuition is that celestial bodies aren't flying away from each other accelerated by some unseen energy so much as getting smaller. If two things shrink in place, the distance between them grows.
Maybe there's some obvious reason why that couldn't be the case, i'd be interested to know!
That wouldn't explain the redshift, would it?
If we’re shrinking too, I think that we’d perceive a given photon getting longer and hence redder.
(This leads to another problem: why don’t the photons shrink too?)
(This leads to another problem: why don’t the photons shrink too?)
The amount of space for us to shrink into is absolutely miniscule compared to the space available to expand between us and distant galaxies.
The metric expansion of space appears to be an extremely weak, small effect. It just adds up to something measurable in the vast gulfs between galaxies.
Furthermore the amount of acceleration away from us is proportional to the distance from us (farther things are accelerating away faster). The shrinking hypothesis only makes sense of that data if it posits that we are the center of the universe.
The metric expansion of space appears to be an extremely weak, small effect. It just adds up to something measurable in the vast gulfs between galaxies.
Furthermore the amount of acceleration away from us is proportional to the distance from us (farther things are accelerating away faster). The shrinking hypothesis only makes sense of that data if it posits that we are the center of the universe.
Atoms can’t shrink because they’re already (ish) in their quantum mechanically minimal state. I think that minimum state depends on the value of the Plank constant. Humour me for the sake of the thought experiment: what would we observe if it wasn’t constant, and changed in a way which allowed atoms to shrink very slowly?
(I’m really tired right now, forgive me if this is a dumb question)
(I’m really tired right now, forgive me if this is a dumb question)
I don't know. And this has nothing to do with the metric expansion of space, since we don't observe it between atoms or even between stars in a galaxy. It's only between galaxies that we observe expansion.
And before anyone mentions Casimir cavities, I did a blog post in the style of a paper about that: https://kitsunesoftware.wordpress.com/2017/04/20/can-a-casim...
AFAIK the Casimir force is due to the van der Waals force between the plates, so doesn't that spoil the negative energy party from the get-go?
https://arxiv.org/abs/1605.04143
https://arxiv.org/abs/hep-th/0503158
https://arxiv.org/abs/1605.04143
https://arxiv.org/abs/hep-th/0503158
I'm not an expert, but this paper makes a convincing argument that that's not a problem. https://arxiv.org/abs/1702.03291
Ah, thanks, hadn't seen that follow-up paper.
Isaac Arthur did and episode on this topic specifically [1]. It's one of his early ones. There are a whole lot of "ifs" here, just one of which is negative mass.
[1]: https://www.youtube.com/watch?v=yCCsmxGjEV0
[1]: https://www.youtube.com/watch?v=yCCsmxGjEV0
> He contends that there likely isn't a sentient civilization within about a billion light years of us because the signature of Dyson spheres would be unmistabkable and unmissable.
If a civilization has the intelligence and foresight to build a Dyson sphere, how much more intelligence and foresight does it need to hide one?
If a civilization has the intelligence and foresight to build a Dyson sphere, how much more intelligence and foresight does it need to hide one?
See [1] and [2] where the idea of hiding a Dyson sphere is covered in depth. It essentially means breaking the laws of thermodynamics, specifically entropy. Hit and object with light from a star and it heats up. It radiates away that heat in a predictable way.
[1] https://www.youtube.com/watch?v=QfuK8la0y6s
[2] https://www.youtube.com/watch?v=HlmKejRSVd8
[1] https://www.youtube.com/watch?v=QfuK8la0y6s
[2] https://www.youtube.com/watch?v=HlmKejRSVd8
Waste heat must be radiated away, though thermodynamics would be quite content if that radiation is anisotropic.
For example, consider a perfectly insulating black box with small hole. Observers on the opposite side from the hole will not observe any radiation from the interior of the box.
I don't think there's any physical limit on collimating the outgoing radiation to hide from everyone outside a narrow beam. It's "just an engineering problem".
For example, consider a perfectly insulating black box with small hole. Observers on the opposite side from the hole will not observe any radiation from the interior of the box.
I don't think there's any physical limit on collimating the outgoing radiation to hide from everyone outside a narrow beam. It's "just an engineering problem".
Actually, I believe the law of Etendue[1] covers that. Basically, any focusing of the area of light must be balanced by a widening of the angle of that light.
1: https://en.wikipedia.org/wiki/Etendue
1: https://en.wikipedia.org/wiki/Etendue
In terms of hiding an emitter, the relevant quantity is the beam solid angle in the far field. This is wavelength dependent which implies temperature dependence if we're talking thermal radiation.
The lower the temperature, the longer the wavelength and the wider the beam (given fixed emitter geometry). So there's a tradeoff between hiding your Dyson sphere vs extracting the most energy from the source.
The lower the temperature, the longer the wavelength and the wider the beam (given fixed emitter geometry). So there's a tradeoff between hiding your Dyson sphere vs extracting the most energy from the source.
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> It radiates away that heat in a predictable way.
Unless that heat energy itself is also caught and used.
Unless that heat energy itself is also caught and used.
That is exactly what is meant by "It essentially means breaking the laws of thermodynamics".
Have there been any studies about whether Dyson swarms harvesting under 0.1% of the star's output are detectable, especially if the designers want to minimize the chance of detection?
I suspect that civilisations that make it to the Dyson swarm stage are on average a little biased towards environmentalism in order to survive past their terrestrial industrial stage.
Doesn't make sense to put a giant target on yourself until you can discount the dark forest hypothesis either, especially not when you've just beaten incredible odds to become a near-immortal truly space-faring civilisation.
I suspect that civilisations that make it to the Dyson swarm stage are on average a little biased towards environmentalism in order to survive past their terrestrial industrial stage.
Doesn't make sense to put a giant target on yourself until you can discount the dark forest hypothesis either, especially not when you've just beaten incredible odds to become a near-immortal truly space-faring civilisation.
Once it is established there is a safe way to roam around and do construction logistics the dark forest hypothesis doesn't make much sense. A real advanced civilisation would have detectable honeypot decoy dyson spheres all over the place just as an intelligence gathering tool to see if anybody will actually come after them and with what.
Its an interesting question; if you're an aggressor and see a 'low tech' civilisation recklessly build an obvious Dyson sphere what probability do you put that its a honeypot from a real threat... and so on.
I personally find the dark forest interesting not because I think it is likely but because even giving it a very small probability of being true would be enough for near immortal high tech civilisations to move very cautiously.
I personally find the dark forest interesting not because I think it is likely but because even giving it a very small probability of being true would be enough for near immortal high tech civilisations to move very cautiously.
> I'll use Isaac Arthur dismissal of FTL travel as to why
what credentials does he have?
> Put me firmly in the camp that believes the speed of light is a hard limit on the universe
the speed of light isn't a limit in the sense that nothing can be greater than it. it is a crossover point that can't be crossed over for things above or below it to the other side.
> I'm not sure why it matters that a black hole would be spinning.
black holes that spin are much different than non-spinning holes and have more complicated dynamics. if they are spinning, they are dragging space-time along with them. see this paper that shows some actual visuals of what a spinning black hole might look like and what it does to the light around it.
https://arxiv.org/abs/1502.03808
what credentials does he have?
> Put me firmly in the camp that believes the speed of light is a hard limit on the universe
the speed of light isn't a limit in the sense that nothing can be greater than it. it is a crossover point that can't be crossed over for things above or below it to the other side.
> I'm not sure why it matters that a black hole would be spinning.
black holes that spin are much different than non-spinning holes and have more complicated dynamics. if they are spinning, they are dragging space-time along with them. see this paper that shows some actual visuals of what a spinning black hole might look like and what it does to the light around it.
https://arxiv.org/abs/1502.03808
The implications that any advanced civilization would have Dyson Spheres, that these are in any way detectable and overall that the civilization would be unwilling or incapable of hiding themselves; are entirely based on speculation as well.
I feel like whether or not there are Dyson spheres is distinct from whether or not there are sapient civilizations beyond Earth. Unless the argument is that we don't count as sapient because we don't have Dyson spheres yet?
Hell, we're assuming that Dyson spheres are even possible with such a conjecture. I'm not convinced they are (not without materials that border if not cross outright into magic). It's also not certain if they're necessary to build to sustain any size of spacefaring civilization (artificial nuclear fusion would kinda defeat the point).
Hell, we're assuming that Dyson spheres are even possible with such a conjecture. I'm not convinced they are (not without materials that border if not cross outright into magic). It's also not certain if they're necessary to build to sustain any size of spacefaring civilization (artificial nuclear fusion would kinda defeat the point).
Dyson spheres at some point were conflated to a structure that is a rigid shell around a star, something for which no known material would be able to support. The original idea of a Dyson sphere is now more often called a Dyson swarm to avoid this confusion.
A Dyson swarm (the original Dyson sphere) is a cloud of independently orbiting habitats/bodies/structures.
A Dyson swarm (the original Dyson sphere) is a cloud of independently orbiting habitats/bodies/structures.
That seems like it'd be even less efficient. A "swarm" like that would be inherently reliant on maintaining orbits around the target star. In order to capture even a significant fraction of a star's energy you'll need a lot of stations orbiting that star, and they'll need to overlap (i.e shadow out stations further behind them / get shadowed out by stations further in front of them).
Even if a civilization's capable of building that many stations to surround a star in a deliberate sort of Kessler syndrome, it ain't clear that a civilization would ever need to do so.
Even if a civilization's capable of building that many stations to surround a star in a deliberate sort of Kessler syndrome, it ain't clear that a civilization would ever need to do so.
>He contends that there likely isn't a sentient civilization within about a billion light years of us because the signature of Dyson spheres would be unmistabkable and unmissable.
I guess the human civilization doesn't count as "sentient" because we don't have a Dyson sphere yet...
Also how "unmissable" is a dyson sphere? Do we have the means to survey every single star within one billion light year radius? Hell, we know neutron stars are real, same for blackholes, but does that mean we observed every single one of them and didn't miss a single one?
I guess the human civilization doesn't count as "sentient" because we don't have a Dyson sphere yet...
Also how "unmissable" is a dyson sphere? Do we have the means to survey every single star within one billion light year radius? Hell, we know neutron stars are real, same for blackholes, but does that mean we observed every single one of them and didn't miss a single one?
Dyson spoke of "swarms", not spheres. The sphere came earlier in scifi. The dyson swarm was a network of solar collectors orbiting a star, a far more practicable structure than the hollow sphere concept. We are babystepping towards this. We have probes out there blocking, harvesting, a tiny fraction of our star's energy already.
I really feel that no civilization would build dyson spheres. Why would anyone want to signal others, here i am?
A topic also covered in depth:
- Secret Aliens [1]
- Hidden Aliens [2]
Basically you can't hide from a K2 civilization in your same galaxy so there's really no point in trying.
[1] https://www.youtube.com/watch?v=IpF25knrGtg&t=1657s
[2] https://www.youtube.com/watch?v=tEBn8bc0k-I
- Secret Aliens [1]
- Hidden Aliens [2]
Basically you can't hide from a K2 civilization in your same galaxy so there's really no point in trying.
[1] https://www.youtube.com/watch?v=IpF25knrGtg&t=1657s
[2] https://www.youtube.com/watch?v=tEBn8bc0k-I
This reads vastly like "You can't protect from a determined nation-state actor, so why would you protect yourself at all". To me it seems obviously there is a point, namely that you will hide yourself from every non-K2 civilization.
I think the assumption is that the difficulty of long-range space travel is such that only the "nation-state actors" in this analogy are likely to attack you in the first place. Just by existing in a universe with the laws of physics ours has, you're effectively secure against attack from low-tech civilizations.
Does gravity propagate at the speed of light? Like, if I were to plop down a planet somewhere in the solar system, would the gravitational effects be immediate or would it take effect at the speed of light? Because if it's immediate, then we should be able to transmit information through gravity waves if we could build a device to detect subtle enough changes.
Yes, gravity operates at c. There is nothing that we know of (or have a theory of) that can even in principle travel faster than c.
It might interest you that a couple of years ago was the first observation of gravitational waves. Here is a BBC article https://www.bbc.com/news/science-environment-35524440
> I'm not sure why it matters that a black hole would be spinning.
Because of frame dragging.
https://en.wikipedia.org/wiki/Frame-dragging
Because of frame dragging.
https://en.wikipedia.org/wiki/Frame-dragging
isn't a sentient civilization within about a billion light years of us because the signature of Dyson spheres would be unmistabkable and unmissable.
It is entirely possible that advanced sentient civilizations have realized that there is such a thing as 'enough technology', learned enough to permanently liberate themselves from basic needs, and found other kinds of fulfillment and amusement.
It is entirely possible that advanced sentient civilizations have realized that there is such a thing as 'enough technology', learned enough to permanently liberate themselves from basic needs, and found other kinds of fulfillment and amusement.
I think it's likely even. Look at the digital worlds we are creating in games. I find it far more likely we build a simulation more enticing than reality and find ways to leave the confines of our current reality behind. Not too different from what happens with the AI in the movie "Her".
The assumption that anyone who can build a Dyson sphere would want to has always seemed a bit off to me. Energy use in highly developed countries is stagnating or even falling, and the rate of population growth looks set to decline. What do the hypothetical Dyson sphere builders actually want with all the energy?
Also, perhaps that the idea of a Dyson sphere is crude and irrelevant to more advanced civilizations. If we look at our ideas from 1000 years ago they have virtually no predictive power for future technology.
This is really the beauty of the Fermi Paradox because the issue isn't "would everyone do this?". If there are starfaring civilizations (or just civilizations with the necessary technology) within detectable range, it just takes one to go this route.
Since we've been unable to detect the telltale signatures of such a megastructure, it either means that none of the civilizations within range have gone this route or there are none. Given what we know about the benefits of a Dyson swarm and how relatively low-tech it is, the idea that no one has gone that route becomes increasingly unlikely with the more civilizations there are.
Since we've been unable to detect the telltale signatures of such a megastructure, it either means that none of the civilizations within range have gone this route or there are none. Given what we know about the benefits of a Dyson swarm and how relatively low-tech it is, the idea that no one has gone that route becomes increasingly unlikely with the more civilizations there are.
> Given what we know about the benefits of a Dyson swarm
I think there's a real question of whether anyone would actually want one. The sun's total power output per person on earth is 5.5e+16W. That's 3000 times total human energy usage, _per person_. Even if you assume a system population in the trillions, that's still a pointlessly large amount of energy per capita (and again, current population trends don't support that, and we may reasonably assume that most Dyson sphere builders will figure out birth control).
Most possible hypothetical uses for them seem to be things like converting all the mass in a solar system into a computer or similar, but again there's a real question of whether there's any market for that.
I'm also not convinced we could necessarily detect one. A super-high-tech magic one would capture most of the available energy, leaving a largely invisible thing with mass, which sounds quite a lot like a neutron star. And if you had a lower-tech one that leaked most of the energy, well, that might look distinctive, but if you're throwing most of the energy away you probably don't need a complete Dyson sphere.
And in any case, organised searches for Dyson spheres are pretty new, and are small efforts. We might have the data to support them right now, it's just that no-one's noticed yet...
I think there's a real question of whether anyone would actually want one. The sun's total power output per person on earth is 5.5e+16W. That's 3000 times total human energy usage, _per person_. Even if you assume a system population in the trillions, that's still a pointlessly large amount of energy per capita (and again, current population trends don't support that, and we may reasonably assume that most Dyson sphere builders will figure out birth control).
Most possible hypothetical uses for them seem to be things like converting all the mass in a solar system into a computer or similar, but again there's a real question of whether there's any market for that.
I'm also not convinced we could necessarily detect one. A super-high-tech magic one would capture most of the available energy, leaving a largely invisible thing with mass, which sounds quite a lot like a neutron star. And if you had a lower-tech one that leaked most of the energy, well, that might look distinctive, but if you're throwing most of the energy away you probably don't need a complete Dyson sphere.
And in any case, organised searches for Dyson spheres are pretty new, and are small efforts. We might have the data to support them right now, it's just that no-one's noticed yet...
There's an old fairy tale about a table that covers itself with food whenever you say some magic words. It's a relic from a time when starvation was a real problem for much of the population, and feasting was a real boon.
In 2019, we've solved the food problem, at least in the developed world, mostly. If you need food in a hurry you don't need a magic table - you need a diner, or a restaurant, or a fast food place, or some wrapped sandwiches.
Dyson Spheres are a Steampunk version of the fairy tale, a relic of an energy-poor and slightly overcrowded culture. OMG all that energy! All that space! You could use it for computing! Or... something else!
In reality by the time we got to the point where building a Dyson Swarm was a realistic possibility, we'd most likely have moved far beyond needing one, or having any interest in needing one.
In 2019, we've solved the food problem, at least in the developed world, mostly. If you need food in a hurry you don't need a magic table - you need a diner, or a restaurant, or a fast food place, or some wrapped sandwiches.
Dyson Spheres are a Steampunk version of the fairy tale, a relic of an energy-poor and slightly overcrowded culture. OMG all that energy! All that space! You could use it for computing! Or... something else!
In reality by the time we got to the point where building a Dyson Swarm was a realistic possibility, we'd most likely have moved far beyond needing one, or having any interest in needing one.
It’s also reasonable to speculate that a sufficiently advanced species might identify the solution to the problem of energy useage as being population control rather than mega-engineering. Instead of trillions, maybe a hallmark of sufficiently advanced species is orders of magnitude fewer of them. Especially if something like immortality is a goal, then reproduction has to be controlled.
It’s certainly easier than capturing a star’s total output!
It’s certainly easier than capturing a star’s total output!
How can you be so sure that a Dyson swarm is a sensible route at all given more advanced technology? We can't even figure out the sensible route for tech 5 years out.
They only need to not want to waste a star's worth of power, or a galaxy's. That's what happens while you do nothing. "You need to take care of your star, or it gets all dark and icky" within a few billion years.
Perhaps these Dyson-sphere-building civilizations only live around red dwarves (because that's where they originated). Red dwarves are dim and hard to detect, especially when they are far away. A red dwarf with a dyson sphere around it would be even harder to detect.
I'm more skeptical of the need for Dyson spheres than practicality of ftl travel
The space can be bent. I am firmly in the camp that everything is possible. Reason we aren’t in contact with other intelligent life forms is that we are too primitive. But things change a lot with every next leap
Not everything is possible. There are things which are provably impossible. It is, for example, impossible to find an algebraic solution for general polynomials of degree five or higher. The things we know to be impossible tend to be mathematical, or a "real world" system exactly modeled by math, simply because math tends to be the way we conclusively prove something.
Mathematical/Geometrical fact: Parallel lines can never intersect. But will they not intersect if I bend the space?
When you say on algebraic solution exists, that doesn’t mean no solution exists?
When you say on algebraic solution exists, that doesn’t mean no solution exists?
How is it possible to detect a dyson sphere?
How easy are they to miss?
How easy are they to miss?
I'm not quite sure how do we start with a "probability to survive trip to the event horizon" and end up with a possibility to travel faster than light? What is that hyperspace the article talks about? How falling down the black hole would transport the object anywhere spatially?
The only thing such a trip could be used for is to see the end of the universe. As every object getting near the event horizon experiences the time slowing down compared with the outside a person on board a ship could probably see stars going out etc as billions of years passed. The time slows down so much one could never "pass through" a black hole as reaching the singularity would require the time to stop. So as the ship approaches the singularity the black hole would get smaller and smaller as it evaporated during those billions of years until it eventually disappeared. However, a ship wouldn't survive the disappearance as when the black hole is getting smaller the tidal forces increase eventually ripping the ship to shreds.
The only thing such a trip could be used for is to see the end of the universe. As every object getting near the event horizon experiences the time slowing down compared with the outside a person on board a ship could probably see stars going out etc as billions of years passed. The time slows down so much one could never "pass through" a black hole as reaching the singularity would require the time to stop. So as the ship approaches the singularity the black hole would get smaller and smaller as it evaporated during those billions of years until it eventually disappeared. However, a ship wouldn't survive the disappearance as when the black hole is getting smaller the tidal forces increase eventually ripping the ship to shreds.
Yes, TFA says nothing about what happens after surviving the fall. But from Burko and Khanna (2019) I get this:
> The fate of an astronaut who falls into a black hole depends not just on the latter’s properties (such as the intrinsic parameters, i.e., the mass and spin angular momentum, and the external perturbation fields) but also on the former’s worldline. ... However, astronauts with positive energy and low angular momentum (including counterrotating ones) arrive at the outgoing leg of the black hole’s inner horizon ("outgoing inner horizon", henceforth, OIH).
> The properties of spacetime at the OIH have been proposed to be those of an effective shock wave singularity. Specifically, it was proposed in [2] that daughters of a family of free-falling astronauts whose geodesics intersect with the OIH, and who are separated only by time translations (and labeled by the advanced time values at which they cross the event horizon (EH) [symbols]) experience a change of order unity in typical metric perturbations, and that these changes occur over a lapse of proper time that drops like [symbols] with increasing [symbols], where [symbols] is the surface gravity of the OIH. Sufficiently late-falling daughters therefore experience an effective shock wave singularity, the Marolf-Ori singularity ("outflying singularity").
I have no clue what that means. Anyone?
0) Burko and Khanna (2019) The Marolf-Ori singularity inside fast spinning black holes, https://arxiv.org/pdf/1901.03413.pdf
> The fate of an astronaut who falls into a black hole depends not just on the latter’s properties (such as the intrinsic parameters, i.e., the mass and spin angular momentum, and the external perturbation fields) but also on the former’s worldline. ... However, astronauts with positive energy and low angular momentum (including counterrotating ones) arrive at the outgoing leg of the black hole’s inner horizon ("outgoing inner horizon", henceforth, OIH).
> The properties of spacetime at the OIH have been proposed to be those of an effective shock wave singularity. Specifically, it was proposed in [2] that daughters of a family of free-falling astronauts whose geodesics intersect with the OIH, and who are separated only by time translations (and labeled by the advanced time values at which they cross the event horizon (EH) [symbols]) experience a change of order unity in typical metric perturbations, and that these changes occur over a lapse of proper time that drops like [symbols] with increasing [symbols], where [symbols] is the surface gravity of the OIH. Sufficiently late-falling daughters therefore experience an effective shock wave singularity, the Marolf-Ori singularity ("outflying singularity").
I have no clue what that means. Anyone?
0) Burko and Khanna (2019) The Marolf-Ori singularity inside fast spinning black holes, https://arxiv.org/pdf/1901.03413.pdf
So, there's a lot of work that has been done on this. Generally there is a difference between large and small black holes. With the smaller ones, tidal forces rip you apart down to quarks and you die. With larger ones, tidal forces aren't as crazy (they are still totally crazy though) and you sail right into the event horizon. It may be survivable.
As for the time distortion: Yes, you see the end of the universe regardless of the black hole size. Yet, your clock continues to tick along just fine and you still fall in. Per our current understanding of physics, you get to see everything in the universe blue shift to infinity. In smaller black holes, since the Lorenz transform is so curved, all of space gets warped to directly in front of you, all the incoming radiation gets blue shifted to infinity. Essentially, every quark and electron gets blasted by pure radiation of infinitely small frequency. Think standing in front of a train in a dark tunnel with a bright light on the front. For larger black holes the Lorenz transform is less curved, so the cosmic Train Collision happens closer to the event horizon; but you still get blasted. (Note: I don't actually know if this is due to the Lorenz transform, but the best way to get a right answer on the internet is to give out the wrong answer :) )
If you are thinking that none of this makes sense and are saying "yes, but what about..." then you are thinking correctly. Black holes are very poorly understood and we're just at the beginning of trying to figure them out.
One very important ratio to remember is: 5 : 20 : 75 .
In the universe, everything that you are made of, all the matter, is only 5% of our known universe and most of that matter is locked up in stars. We're actually only a very small fraction of the universe.
Dark matter is ~20% of the stuff in the universe. About all we currently know about dark matter is that it falls down. Does it have a temperature? No clue. Does it interact with matter? More data is needed. Does it interact with itself? We haven't any idea, would you like more tea? Dark matter is ~4x the amount of stuff we are, and we haven't a clue what it does.
That said, Dark Energy is ~75% of the stuff in the universe and it ... falls up? Honestly, we're completely lost. We have no idea how it works, we just know the universe is flying away from itself and it's gas pedal is firmly glued to the floor. We haven't any remotely serious idea how to probe it outside of looking at galaxies and hoping we get lucky and see something funny.
So, before we get all high and mighty and try to think we have any idea what is going on in a black hole, we've got to figure out what the other 95% of the universe is doing, as it's very likely to have really important things going on. Hyperspace? I mean, sure, why not? It's just about as strange a thing as Dark Energy is.
So, I think the consensus is that: More research funding is needed.
As for the time distortion: Yes, you see the end of the universe regardless of the black hole size. Yet, your clock continues to tick along just fine and you still fall in. Per our current understanding of physics, you get to see everything in the universe blue shift to infinity. In smaller black holes, since the Lorenz transform is so curved, all of space gets warped to directly in front of you, all the incoming radiation gets blue shifted to infinity. Essentially, every quark and electron gets blasted by pure radiation of infinitely small frequency. Think standing in front of a train in a dark tunnel with a bright light on the front. For larger black holes the Lorenz transform is less curved, so the cosmic Train Collision happens closer to the event horizon; but you still get blasted. (Note: I don't actually know if this is due to the Lorenz transform, but the best way to get a right answer on the internet is to give out the wrong answer :) )
If you are thinking that none of this makes sense and are saying "yes, but what about..." then you are thinking correctly. Black holes are very poorly understood and we're just at the beginning of trying to figure them out.
One very important ratio to remember is: 5 : 20 : 75 .
In the universe, everything that you are made of, all the matter, is only 5% of our known universe and most of that matter is locked up in stars. We're actually only a very small fraction of the universe.
Dark matter is ~20% of the stuff in the universe. About all we currently know about dark matter is that it falls down. Does it have a temperature? No clue. Does it interact with matter? More data is needed. Does it interact with itself? We haven't any idea, would you like more tea? Dark matter is ~4x the amount of stuff we are, and we haven't a clue what it does.
That said, Dark Energy is ~75% of the stuff in the universe and it ... falls up? Honestly, we're completely lost. We have no idea how it works, we just know the universe is flying away from itself and it's gas pedal is firmly glued to the floor. We haven't any remotely serious idea how to probe it outside of looking at galaxies and hoping we get lucky and see something funny.
So, before we get all high and mighty and try to think we have any idea what is going on in a black hole, we've got to figure out what the other 95% of the universe is doing, as it's very likely to have really important things going on. Hyperspace? I mean, sure, why not? It's just about as strange a thing as Dark Energy is.
So, I think the consensus is that: More research funding is needed.
Yes, they might. And then again they might not. Probably not. In fact, there’s not a snowflakes chance in hell they will. This is the scientific equivalent of wondering how many angels can dance on the head of a pin. Oh, except now they have a computer model. Plus ça change, plus c'est la même chose
I'm just confused, I thought a black hole was where gravity was so strong light could not escape it just starts looping back on itself like a coin in a large funnel, then how could we escape? We would just spiral down the drain? Why would there be a portal?
If your drain analogy holds beyond the point of you losing the sightof probe, the matter that goes into drain does not cease to exists, even if for all your practical purposes it does. On the contrary, you can be sure it does reappear somewhere.
Also, it's pretty much certain that wherever there appears infinity in physical model you can be sure it's a limitation of the model, not actual physics of the object. We do not observe infiities, even though pretty much every of our models has some.
Those would be two basic hunches against stuffing matter into infinity without consequences. Some kind of exit seems natural, the question is how destructive it would be.
Also, it's pretty much certain that wherever there appears infinity in physical model you can be sure it's a limitation of the model, not actual physics of the object. We do not observe infiities, even though pretty much every of our models has some.
Those would be two basic hunches against stuffing matter into infinity without consequences. Some kind of exit seems natural, the question is how destructive it would be.
If there were an exit to a blackhole, they would stop gaining mass. If that was true they would all be the same size.
Predicting portals is still far from that though. Like I would be ejected to the other side? And gravity would stop pulling me in? I could see a burst of energy somehow.
Is it just me, or does the article not attempt to explain what this has to do with "hyperspace travel"? The only thing new here is that you can plunge into oblivion without getting torn apart in the process.
Nope, your not missing anything. The whole hyperspace stuff sounds like clickbait. You need exotic matter stuff with negative mass/energy stop stop a wormhole from collapsing, otherwise it would destabilise as soon as a photon enters it. This article is showing that in theory if you could keep the bridge open somehow, you could send a ship through. That's a big if
My sci-fi plot theory: our universe is what is inside a black hole. The big bang was the formation of a black hole on another universe pulling matter to ours.
Nice! Thinking again, it is a good that there is some science behind this. Good place to start
I believe that's a current theory in the Physics community. Also, it reminds me a bit of the miniature galaxy from the original Men in Black film - https://www.youtube.com/watch?v=P7ojSW5pODk
Isn't that just a mainstream physics theory?
Stanford physicist Leonard Susskind gave a great talk on it. https://www.youtube.com/watch?v=2DIl3Hfh9tY
Is it? Gotta change my plot now then :)
This looks a lot like what was proposed back in the 70s by Adrian Berry in his book "The Iron Sun: Crossing the Universe through black holes": https://www.goodreads.com/book/show/1091779.The_Iron_Sun
I recall reading somewhere the density at the event horizon of the super massive black hole at the center of our galaxy is about the same as water. The singularity is supposedly infinite, but the event horizon depends on the size of the black hole.
This isn't quite right. If you take the mass of Sgr A* (the black hole in the center of the galaxy) and divide it by the volume of a sphere (let's ignore rotation for simplicity) with the radius of the event horizon, you do get a density value near that of water. But almost all of the mass is concentrated in or near the singularity. If you ignore the small amount of stuff falling into Sgr A* at any given moment, the density at the event horizon is 0.
A halo drive sends light, instead of people, slingshotting around binary black holes and harvests the energy (via solar sales) in the blue-shifted life. Much safer!
I do wonder though if you travel at the speed of light wouldn't your ship break apart even if you accidentally hit a tiny rock in space? Maybe even dust?
[deleted]
John Titor is that you?
Original source: https://theconversation.com/rotating-black-holes-may-serve-a...
Ok, changed to that from https://daily.jstor.org/rotating-black-holes-may-serve-as-ge.... Thanks!
As much as I love science fiction. In reality, even making it the nearest star is an impossible feat. Even traveling at the speed of light (which we are not even sure the human body can handle) it would take 100 years to reach our nearest star; let alone the nearest black hole. Even whether black holes exist, and what they really are is hotly debated. I think the idea of interstellar travel is futile, and we should focus on improving our quality of life here (free energy i.e. Telsa tech, transporting goods with electrogravitic vehicles, curing diseases, more scientific agricultural practices, easing access to education/job skills, etc).
>Even traveling at the speed of light (which we are not even sure the human body can handle) it would take 100 years to reach our nearest star
Er, no. Travelling at c, it would take 4.5 years to get to our nearest star. The nearest (known) black hole is V616, 3,000 years of travel away if travelling @ c.
Er, no. Travelling at c, it would take 4.5 years to get to our nearest star. The nearest (known) black hole is V616, 3,000 years of travel away if travelling @ c.
Even better, traveling at c, it would take exactly zero shipboard time. Space contracts infinitely for the sufficiently fast. Only outside viewers would see it take 4.5 years.
A bit pedantic but considering an acceleration and then deceleration of 1g, i can see the 100 year number being valid
It would take just under a year to accelerate to the speed of light at 1g. This doesn’t significantly change the four year number.
>Even traveling at the speed of light...it would take 100 years to reach our nearest star
The nearest star is a little over 4 light years away, not 100.
The nearest star is a little over 4 light years away, not 100.
Let's compute travel time assuming constant acceleration to halfway point, and then constant deceleration to the destination. 'a' is acceleration and 'd' is distance to the star.
v(t) = at (velocity at time t)
∫v(t)dt = 0.5 a t^2 (distance traveled at time t)
0.5 a t^2 = 0.5 d ==> t = sqrt(d/a) (time to halfway point)
Plugging in d=4.5ly and a=9.81m/s yields 2.07 years to the halfway point, so that's just over 4 years total travel time at 1G.
v(t) = at (velocity at time t)
∫v(t)dt = 0.5 a t^2 (distance traveled at time t)
0.5 a t^2 = 0.5 d ==> t = sqrt(d/a) (time to halfway point)
Plugging in d=4.5ly and a=9.81m/s yields 2.07 years to the halfway point, so that's just over 4 years total travel time at 1G.
If you take relativity into account (which you should, it's how the universe works after all), traveling 4.37 light years at 1G acceleration/deceleration will take 3.58 years from the perspective of the people on the ship or 6 years from the perspective of those still on Earth[0].
You'd reach 95% of the speed of light, which would take 4 gigatons of TNT[1] (and 4 more to decelerate) if it's just you and your ship and energy source weight nothing. That's definitely science fiction. 100 years is optimistic.
[0] http://convertalot.com/relativistic_star_ship_calculator.htm...
[1] https://www.omnicalculator.com/physics/relativistic-ke?v=v:....
You'd reach 95% of the speed of light, which would take 4 gigatons of TNT[1] (and 4 more to decelerate) if it's just you and your ship and energy source weight nothing. That's definitely science fiction. 100 years is optimistic.
[0] http://convertalot.com/relativistic_star_ship_calculator.htm...
[1] https://www.omnicalculator.com/physics/relativistic-ke?v=v:....
The fun part is figuring out how far you go for each additional year. As experienced on board there's huge gains in distance for each extra year.
But looks like you forgot about relativity and that starts having a pretty big impact.
But looks like you forgot about relativity and that starts having a pretty big impact.
If we could travel at (just below) the speed of light, then getting to the next star would take somewhat under four years from the point of view of the travelers assuming an acceleration of 1g (or no noticeable time at all assuming serious magic, with close to infinite acceleration). Of course, the energy to make the acceleration is the big problem...
I think you're being down-voted because you are sort of wrong about the distances. We could probably get some people to another star. Why we would do that, or what we would tell them (with a five year communication delay) after they got there, is unclear.
For the record, I think your questioning of "what black holes really are" is prudent. The OP article is not prudent, firstly because any of its implications won't be realized for at least 3,000 years. Secondly because our challenge as a society is very much not speculating about this thing Hawking wrote about, and very much is trying to make any of these scenarios useful to us.
Which leads to my fringe opinion that we should try really hard to build a black hole, even if we're worried about it ending us.
"Fuckin' magnets. HOW DO THEY WORK?"
For the record, I think your questioning of "what black holes really are" is prudent. The OP article is not prudent, firstly because any of its implications won't be realized for at least 3,000 years. Secondly because our challenge as a society is very much not speculating about this thing Hawking wrote about, and very much is trying to make any of these scenarios useful to us.
Which leads to my fringe opinion that we should try really hard to build a black hole, even if we're worried about it ending us.
"Fuckin' magnets. HOW DO THEY WORK?"
> "I think you're being down-voted because you are sort of wrong about the distances."
Or maybe it's because he proposed we dedicate our resources to violating the laws of thermodynamics ("free energy"...)
Or maybe it's because he proposed we dedicate our resources to violating the laws of thermodynamics ("free energy"...)
For clarification and in Tesla's defense: If I've correctly read some of the descriptions of his idea, it didn't involve "energy from nothing" and hence no obvious violation of thermodynamics. Rather, it involved (roughly) building huge antennas/lightning rods to tap into the natural electric potential (against ground) of the ionosphere.
As I understand it, the idea is simply impractical. But there's a huge Tesla fan base among the intersection of conspiracy theorists and amateur (pseudo)scientists who believe that Tesla's idea was scuttled and suppressed by Big Electric to protect their monopoly on generating electricity in harder ways.
As I understand it, the idea is simply impractical. But there's a huge Tesla fan base among the intersection of conspiracy theorists and amateur (pseudo)scientists who believe that Tesla's idea was scuttled and suppressed by Big Electric to protect their monopoly on generating electricity in harder ways.
I can't fathom why anybody in their right mind would choose to call their scheme "free energy", e.g. choose to associate themselves with perpetual motion nuts. We can get electrical energy from sunlight, which is pretty damn neat, and nobody calls that "free energy."
Any black hole we could conceivably create would completely evaporate in nanoseconds. There's even conjecture that the LHC may have created some already (although it's not probable, it's not entirely outside the realm of possibility). It's not like they stick around eating more once you make them.
We might be able to create our own spinning black hole gate :-P
What could possibly go wrong with that idea?
What could possibly go wrong with that idea?
He contends that there likely isn't a sentient civilization within about a billion light years of us because the signature of Dyson spheres would be unmistabkable and unmissable. Now this isn't to say there isn't one that's say, 600 million light years away that built their first Dyson sphere 500 million years ago although, in practice, this doesn't really change the probabilities that much.
If there's FTL then that billion light year practical limit really goes out the window as you can effectively get anywhere in the universe, making the volume of absence be many, many times the size of the observable universe.
I'm not sure why the author is talking about gravity ripping you apart in a black hole. It Is Known [tm] that larger black holes have pretty gentle event horizons.
I'm not sure why it matters that a black hole would be spinning. You can pretty much assume every significant mass in the universe is spinning to some degree (a state of zero spin being highly unlikely over even small amounts of time).
The author talks about the inner event horizon and I guess that's the point. But all of that is highly theoretical. Nothing is known about the inner workings of a black hole. It's all highly theoretical and beyond the ability of general relativity to describe. No other theory has been able to adequately explain or describe gravity let alone extreme gravity so your view on what's within the event horizon probably depends on which unproven theory (eg string theory) you subscribe to.
So this is speculation based on speculation.