An event horizon is not analogous. A black hole is warping space. The ou is due to space itself expanding.
That is, the stuff within which it makes sense to even talk about energy is expanding.
If it expands far enough it could conceivably tear even a black hole apart.
An event horizon does produce Hawking radiation if it's from the expansion of space - at sufficiently large distances and sufficiently high momentums, virtual particle-antiparticle pairs can form where the subsequent expansion of space during their lifetime would cause them to have to become real and energy/entropy robbed from somewhere to drive it.
The main distinction at the moment is that under the current inflationary drivers, the event horizon of expanding space is further from us then our causal light-cone.
Sure, and space expanding causes red shift and eventually will tear fundamental particles apart. It has an effect.
The point remains though that a black hole doesn't form due to inflation. It forms due to the localised force of gravity. They're still not analogous, because their causal mechanisms are so different.
I'm not disagreeing, but the distinction doesn't seem to obvious to me: inside a black hole the roles of time and space flip. So from within a black hole a particle would not perceive that it is moving towards the singularity - the singularity lies in the future, the location now acting as the new time vector. This is one of the origins of GR breaking down in black holes - what happens when you get to the singularity is ill-defined, because technically the rules also say that you can't - you have to be always approaching it, but never reaching it.
Basically physicists smarter then me agree that the universe is not clearly the inside of a black hole, but the distinction we're drawing here feels inadequate. A point in it's favor though is I can't find any analysis of whether you can model the inside of a black hole in an analogous way to the expansion of space or not - i.e. behind an event horizon, would you be unaware of gravity pulling you in? (and even if you were, for a sufficiently large black hole, is it noticeable until you get close enough that the curvature / differential becomes apparent? And what does that even mean if a spatial direction has unified with a time one?)
Wouldn't that also mean that time has become a space like dimension? Could this be a rotation of the coordinate plane of four dimensional space, and everything still works once it cools down enough to form normal matter again?
"I will write your name in the ruin of them. I will paint you across history in the color of their blood."
In regards to a black hole event horizon vs the visible universe (cosmologic) event horizon see “Cosmologic event Horizons, Thermodynamics, and Particle Creation”, Gibbons and Hawking 1977. I am not going to direct link because I am not sure as to the copyrights, but full text is available by google.
Tldr the cosmologic event horizon absolutely does behave similarly to a black hole event horizon from the point of view of an observer.
The abstract for that paper actually tells you where that energy comes from. It comes from outside the OU. Cos that still exists. It just gets transferred, not created or destroyed.
I can only access the abstract. This is the relevant line.
It is shown that this similarity is more than an analogy: An observer with a particle detector will indeed observe a background of thermal radiation coming apparently from the cosmological event horizon. If the observer absorbs some of this radiation, he will gain energy and entropy at the expense of the region beyond his ken and the event horizon will shrink.
So it answers your question.
Right, and if you absorb hawking radiation from a black hole you gain energy at the expense of the material that has previously fallen into the black hole. The processes are essentially identical from the point of view of the observer gaining energy.
The entropy of the cosmological horizon is related to its area. When the horizon radiates energy and it is absorbed by an observer, entropy (or surface gravity) of the horizon decreases and its area decreases. The entropy and energy/mass of the observer also increases. But as the area decreases, the temperature of the radiation decreases, unlike in the black hole case, and so the cosmological horizon is stable. That is, the horizon cannot suddenly collapse inward from the observer absorbing too much radiation. Whereas a black hole will evaporate from radiating too much energy.
Entropy of the horizon can be interpreted as lack of information about the outside universe, so to answer one of your previous questions, no, you can't use it to learn information about what exists outside the horizon.
I guess I keep thinking, if there were a center of the universe that everything was expanding out from, the visible motion/redshift of various bodies would be altered, although likely very slightly, by the difference in relative motion. If we assume that the bodies are all moving out from a center, the and our observable light cone doesn't go past the center of the universe, we would still be able to detect a difference between the redshift with something right next to the edge of our light cone vs something travelling ahead of us or behind us, or much closer to us. All of them would still have the same general motion, but the red line would (if I understand correctly) represent the redshift, since thats the vector component aligned with the path of light between us and the object.
I think part of my confusion is that, this assumes that the objects were all already moving from a central point, which the expansion of space is exaggerating. It sounds like this is pretty clearly not the case, which gets back to space itself expanding, but ?only? in the empty bits, and nothing is actually moving(accelerating? obviously stuff is moving in general) in that case, it just takes longer for light to get from one point to another.
I realize that this is a 2d image, but its really fucking hard to do this in autocad in 3D, so thats what I had. This assumes that there are an equal number of bodies arrayed in a sphere, and this is just a section of that sphere.
If your picture were the case (and some of the confusion may be that it's incomplete wrt reshifts), yes, you would expect to see a bias in the redshift such that you could identify a direction towards the center. For example a slightly higher redshift to your right and a slightly lower redshift to your left would indicate a flow from left to right indicating the center was to your left. We do not observe such biased directional redshift in the observable universe. This is another piece of evidence that the universe has no center.
I feel like this is where some confusion started. I agree that this is a very good sign that the universe is center less, and was trying to ask my questions from the idea that I'm not sure how it could have a finite, objective center, without observable redshift variations.
"I will write your name in the ruin of them. I will paint you across history in the color of their blood."
“There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.
There is another theory which states that this has already happened.”
― Douglas Adams, The Restaurant at the End of the Universe
I enjoy reading cosmology but I am not sure I grasp it at a much deeper level than I can appreciate the muppets on.
I mean this whole conversation has renewed my overall hope that planet 9, so far unobserved, might actually be a captured black hole. Although in that case, how we would ever observe it is up in the air. But a nearby black hole would be super-useful.
I mean this whole conversation has renewed my overall hope that planet 9, so far unobserved, might actually be a captured black hole. Although in that case, how we would ever observe it is up in the air. But a nearby black hole would be super-useful.
I've always heard it takes too much energy to fire someone into the sun, I assume a local black hole would be super-useful because it would overcome this issue while also being a worse punishment than be fired into the sun?
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BrodyThe WatchThe First ShoreRegistered Userregular
If our universe is in a black hole, and there are black holes in our universe, what if they represent a sort of mobious strip sort of never ending spacetime fabric, but we can't see over the edge because the edge represents the space/time flip?
"I will write your name in the ruin of them. I will paint you across history in the color of their blood."
I mean this whole conversation has renewed my overall hope that planet 9, so far unobserved, might actually be a captured black hole. Although in that case, how we would ever observe it is up in the air. But a nearby black hole would be super-useful.
I've always heard it takes too much energy to fire someone into the sun, I assume a local black hole would be super-useful because it would overcome this issue while also being a worse punishment than be fired into the sun?
I was thinking like, we could build a really far out space station and learn physics from it and stuff, but your idea works too.
Although the cool part is that if it's only about Earth-mass, then the gravity of it is similar and it would be tiny, so you could fly right up to it, shimmy down on a rope and feel spacetime get all screwy if you put your hand near it.
I mean this whole conversation has renewed my overall hope that planet 9, so far unobserved, might actually be a captured black hole. Although in that case, how we would ever observe it is up in the air. But a nearby black hole would be super-useful.
I've always heard it takes too much energy to fire someone into the sun, I assume a local black hole would be super-useful because it would overcome this issue while also being a worse punishment than be fired into the sun?
If planet 9 were a black hole, it would have a very small event horizon given because it would be a planet mass black hole. Such a thing shouldn’t exist unless it is a primordial black hole (PBH). That means dark matter (DM) would likely consist of PBHs, which would solve the whole DM composition issue.
It would be a monumental discovery.
Steam - Synthetic Violence | XBOX Live - Cannonfuse | PSN - CastleBravo | Twitch - SoggybiscuitPA
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MorninglordI'm tired of being Batman,so today I'll be Owl.Registered Userregular
An event horizon is not analogous. A black hole is warping space. The ou is due to space itself expanding.
That is, the stuff within which it makes sense to even talk about energy is expanding.
If it expands far enough it could conceivably tear even a black hole apart.
An event horizon does produce Hawking radiation if it's from the expansion of space - at sufficiently large distances and sufficiently high momentums, virtual particle-antiparticle pairs can form where the subsequent expansion of space during their lifetime would cause them to have to become real and energy/entropy robbed from somewhere to drive it.
The main distinction at the moment is that under the current inflationary drivers, the event horizon of expanding space is further from us then our causal light-cone.
Sure, and space expanding causes red shift and eventually will tear fundamental particles apart. It has an effect.
The point remains though that a black hole doesn't form due to inflation. It forms due to the localised force of gravity. They're still not analogous, because their causal mechanisms are so different.
I'm not disagreeing, but the distinction doesn't seem to obvious to me: inside a black hole the roles of time and space flip. So from within a black hole a particle would not perceive that it is moving towards the singularity - the singularity lies in the future, the location now acting as the new time vector. This is one of the origins of GR breaking down in black holes - what happens when you get to the singularity is ill-defined, because technically the rules also say that you can't - you have to be always approaching it, but never reaching it.
Basically physicists smarter then me agree that the universe is not clearly the inside of a black hole, but the distinction we're drawing here feels inadequate. A point in it's favor though is I can't find any analysis of whether you can model the inside of a black hole in an analogous way to the expansion of space or not - i.e. behind an event horizon, would you be unaware of gravity pulling you in? (and even if you were, for a sufficiently large black hole, is it noticeable until you get close enough that the curvature / differential becomes apparent? And what does that even mean if a spatial direction has unified with a time one?)
I agree it seems similar on the surface, its just that you and I might have different observable universes, but most of it overlaps since we are so close to each other. So if you take black hole = observable universe then you and I are two black holes right next to each other whose event horizons heavily overlap and that's...
...that starts getting weird.
Not weird as in impossible.
Weird as in "how is this useful as a way to think about inflation?"
The thought experiment works if you only ever take a single observer and match them to a black hole's singularity. That's not really how this works tho, since every single point in space has it's own "event horizon" observable universe, all right next to each other.
So like, everypoint in space is the singularity of its own black hole. If that's the case how come I'm able to walk down the street?
I dunno I think it just gets more confusing instead of less. I think the point of analogies should be to enhance understanding, not...confuse the fuck out of you, if you get what I mean.
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MorninglordI'm tired of being Batman,so today I'll be Owl.Registered Userregular
I mean planet 9 if it exists is so far out there that for all intents and purposes it might as well be invisible, and that's a simpler explanation than it might be a black hole. It'd be cool but, like, "giant dark rock that is incredibly hard to see cos space is just that big" is a zillion times more likely.
(PSN: Morninglord) (Steam: Morninglord) (WiiU: Morninglord22) I like to record and toss up a lot of random gaming videos here.
In regards to a black hole event horizon vs the visible universe (cosmologic) event horizon see “Cosmologic event Horizons, Thermodynamics, and Particle Creation”, Gibbons and Hawking 1977. I am not going to direct link because I am not sure as to the copyrights, but full text is available by google.
Tldr the cosmologic event horizon absolutely does behave similarly to a black hole event horizon from the point of view of an observer.
The abstract for that paper actually tells you where that energy comes from. It comes from outside the OU. Cos that still exists. It just gets transferred, not created or destroyed.
I can only access the abstract. This is the relevant line.
It is shown that this similarity is more than an analogy: An observer with a particle detector will indeed observe a background of thermal radiation coming apparently from the cosmological event horizon. If the observer absorbs some of this radiation, he will gain energy and entropy at the expense of the region beyond his ken and the event horizon will shrink.
So it answers your question.
Right, and if you absorb hawking radiation from a black hole you gain energy at the expense of the material that has previously fallen into the black hole. The processes are essentially identical from the point of view of the observer gaining energy.
The entropy of the cosmological horizon is related to its area. When the horizon radiates energy and it is absorbed by an observer, entropy (or surface gravity) of the horizon decreases and its area decreases. The entropy and energy/mass of the observer also increases. But as the area decreases, the temperature of the radiation decreases, unlike in the black hole case, and so the cosmological horizon is stable. That is, the horizon cannot suddenly collapse inward from the observer absorbing too much radiation. Whereas a black hole will evaporate from radiating too much energy.
Entropy of the horizon can be interpreted as lack of information about the outside universe, so to answer one of your previous questions, no, you can't use it to learn information about what exists outside the horizon.
I guess I keep thinking, if there were a center of the universe that everything was expanding out from, the visible motion/redshift of various bodies would be altered, although likely very slightly, by the difference in relative motion. If we assume that the bodies are all moving out from a center, the and our observable light cone doesn't go past the center of the universe, we would still be able to detect a difference between the redshift with something right next to the edge of our light cone vs something travelling ahead of us or behind us, or much closer to us. All of them would still have the same general motion, but the red line would (if I understand correctly) represent the redshift, since thats the vector component aligned with the path of light between us and the object.
I think part of my confusion is that, this assumes that the objects were all already moving from a central point, which the expansion of space is exaggerating. It sounds like this is pretty clearly not the case, which gets back to space itself expanding, but ?only? in the empty bits, and nothing is actually moving(accelerating? obviously stuff is moving in general) in that case, it just takes longer for light to get from one point to another.
I realize that this is a 2d image, but its really fucking hard to do this in autocad in 3D, so thats what I had. This assumes that there are an equal number of bodies arrayed in a sphere, and this is just a section of that sphere.
If your picture were the case (and some of the confusion may be that it's incomplete wrt reshifts), yes, you would expect to see a bias in the redshift such that you could identify a direction towards the center. For example a slightly higher redshift to your right and a slightly lower redshift to your left would indicate a flow from left to right indicating the center was to your left. We do not observe such biased directional redshift in the observable universe. This is another piece of evidence that the universe has no center.
So if I understand correctly, if you imagine what a white hole would look like from the inside you end up with something that looks a lot like the visible universe - inside the white hole you would see matter disappear at the edges and an event horizon that would radiate hawking radiation back into the system. The observable universe both does not have a center and from any vantage point looks like a white hole with the observer at the center? I feel like that is significant somehow.
Also I guess based on movement of galaxies no matter where you are in the universe it would appear that the big bang happened in the past right where you are observing from?
I mean this whole conversation has renewed my overall hope that planet 9, so far unobserved, might actually be a captured black hole. Although in that case, how we would ever observe it is up in the air. But a nearby black hole would be super-useful.
I've always heard it takes too much energy to fire someone into the sun, I assume a local black hole would be super-useful because it would overcome this issue while also being a worse punishment than be fired into the sun?
If planet 9 were a black hole, it would have a very small event horizon given because it would be a planet mass black hole. Such a thing shouldn’t exist unless it is a primordial black hole (PBH). That means dark matter (DM) would likely consist of PBHs, which would solve the whole DM composition issue.
It would be a monumental discovery.
Wouldn't tiny black holes be detectable though from emissions and gravitational lensing?
I mean this whole conversation has renewed my overall hope that planet 9, so far unobserved, might actually be a captured black hole. Although in that case, how we would ever observe it is up in the air. But a nearby black hole would be super-useful.
I've always heard it takes too much energy to fire someone into the sun, I assume a local black hole would be super-useful because it would overcome this issue while also being a worse punishment than be fired into the sun?
If planet 9 were a black hole, it would have a very small event horizon given because it would be a planet mass black hole. Such a thing shouldn’t exist unless it is a primordial black hole (PBH). That means dark matter (DM) would likely consist of PBHs, which would solve the whole DM composition issue.
It would be a monumental discovery.
Wouldn't tiny black holes be detectable though from emissions and gravitational lensing?
With an accretion disk, it should be detectable by it's emissions, and so if it existed likely would have been seen by now. If there's no accretion disk, then no, it wouldn't be giving off any detectable emissions. And it's small mass would only bend light very slightly, below the angular resolution of our best telescopes, so it wouldn't be detectable by gravitational lensing. Though you might get lucky and detect it via occlusion of distant stars.
Just remember that half the people you meet are below average intelligence.
I find it harder to believe there’s a non-black hole object that could be considered a planet that we haven’t observed yet, tbh
There are definitely large yet-to-be-observed objects in our system (some brewing in my gut at the moment even), but a planet?
if it's not reflecting light or passing in front of a nearby source of light, it's really hard to see it, even if it's planet sized
we don't really have any evidence it's there other than other things in the region moving slightly differently than we'd expect otherwise
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MorninglordI'm tired of being Batman,so today I'll be Owl.Registered Userregular
edited May 2022
Space is very big, planets surprisingly arent, and that's so far out there's no light to see it and probably no heat to make it glow if it doesn't have any internal convection.
We could easily miss a planet. Potentially for centuries more.
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We had to pull out a lot of cheat codes to start finding more KBOs. We wouldn't have found Pluto for decades if Lowell wasn't convinced there was a fifth giant planet and just happened to calculate it would be passing along the same point in the sky. Lowell kept getting images of Pluto and dismissing it because it clearly wasn't the 10 earth mass monster he was after but some random smudge of cosmic nothing. If planet 10 exists* it's much farther than any of them, and at most a couple times Earth's diameter.
*-The evidence for planet 10 is that the apohelions of many Kuiper belt dwarf planets are on a similar vector, which can happen with eccentric orbits in close resonance with a larger object in a more circular orbit.
However because of the way we found them and the limited number of facilities involved, we found a disproportionate number in a small area of sky. So there is a bias in our data set that's simply impossible to correct for at this time.
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AbsoluteZeroThe new film by Quentin KoopantinoRegistered Userregular
You know what blows my mind? A proton weighs more than the 3 quarks it's made of, due to the strong nuclear force interactions binding the 3 quarks together.
You know what blows my mind? A proton weighs more than the 3 quarks it's made of, due to the strong nuclear force interactions binding the 3 quarks together.
E=mc^2. C is constant so if you add E it makes m go up.
Extreme example: a kugelblitz. Pump enough energy - be it heat or light or just a lot of kinetic energy on a very small object - into a small enough space and you have a black hole made of nothing.
Probably the sheer alienness of the concept. A regular black hole makes a lot of sense, just a lot of stuff in the same place with a lot of gravity. It's a scary thing but it's a fairly simple concept at the basic level.
But a kugelblitz involves fundamentally breaking the universe - channeling thousands of stars worth of energy into a space a few millimeters across to create temperatures so high that temperature starts to have gravity. The end product isn't even particularly dangerous but the process of creating it is Fall of Adam level shit, like God might just renege on the deal after this one.
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MorninglordI'm tired of being Batman,so today I'll be Owl.Registered Userregular
I just think its cool.
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ChanusHarbinger of the Spicy Rooster ApocalypseThe Flames of a Thousand Collapsed StarsRegistered Userregular
it feels disingenuous to say it's a black hole made of nothing and breaking the universe
mass is energy
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MorninglordI'm tired of being Batman,so today I'll be Owl.Registered Userregular
Equations aren't one way.
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BrodyThe WatchThe First ShoreRegistered Userregular
I mean, at that point, I still somewhat struggle with the idea that a massless particle can hit another particle and impart energy.
"I will write your name in the ruin of them. I will paint you across history in the color of their blood."
I mean, at that point, I still somewhat struggle with the idea that a massless particle can hit another particle and impart energy.
Perhaps another way to reword your question if you think of a photon as a packet of energy is "how can energy hit a particle and impart energy?" to realize you were asking the wrong question. The real question is "how does a massless particle have momentum?"
And that is because E=mc^2 is actually a simplification. For an object in motion you need to add a momentum term such that E^2 = (mc^2)^2 + (pc)^2. For an object with no mass, this simplifies to show momentum p=E/c.
A photon, while not having rest mass, because it has energy it will still have momentum. Since it has momentum it can hit another particle and impart that momentum energy on it to move it.
Just remember that half the people you meet are below average intelligence.
They are if entropy is involved. And entropy is involved.
Actually if I remember my PChem was right this isn’t true.
Most physical process if occurring commonly enough on a large enough scale to be statistically analyzed en masse should be expressible in broadly the same way as a chemical reaction.
In a chemical reaction there is always an equillibrium. In a given reaction mixture you will have a proportion of the products and a proportion of the reactants as determined by the entropy of the reactants, the entropy of the products, and the entropy of the energy released or absorbed in the process.
The important thing is that in any system normally the product and reactants will be present in some proportion. There is always a proportion of the reactions running “backward” The interesting thing is that if you perform work on a system you can “push” the equillibrium one way or another.
For example, consider the formation of water from elemental oxygen and hydrogen. In a normal reaction mixture water is VASTLY favored. So consider a glass bubble full of heated steam. Very little of that steam will spontaneously convert to H2 and O2, any any that does will almost immediately react back to H2O. The fraction is actually 2.4E47 to 1 water to elemental H2 and O2. So when you say even under high temperatures very little H2O will dissociate to h2 and o2, it really is very little.
However, instead of steam under high temperature lets have liquid water with a high current running through it. Water is still vastly favored in this situation but importantly when any elemental hydrogen and oxygen forms it bubbles out of the sysytem. This seperates the oxygen and hydrogen from the reaction mixture which affects the equilibrium (the reaction is mow essentially determined by several different equilibriums, the equilibrium in the water itself and the equilibrium of hydrogen and oxygen gas disolving in the water to make it available to react (actually that is a simplification because the elecrodes also cause H3O+ and OH- ions to concentrate within solution which also affects things).
Anyway, by modifiying the physical situation and source of the energy we have now shifted an equilibrium very unfavorable to H2 and O2 to one more favorable to them. There will now be a fairly significant amount of H2 and O2 present in the system (note that you have to put energy into the system for this to work by running a current through the water). By doing this we have indirectly changed the equilibrium of the system by doing work on the system.
But wait, there is also something else we can do!
You can get a pump and pump out the oxygen and hydrogen gas from the system. This will drive the equilibrium even further towards the elemental gases, because when you remove them a new equilibrium forms between the lesser amount of elemental gasses and the water.
So the point is that by doing work on the system and presumably incurring entroy somewhere else you can drive a process that would normally be vastly thermodynamicslly favorable in one direction to other direction.
I would assume in a situation involving the intraconversion of matter to energy these same rules involving equilibrium and reversibility would apply (although depending on situation it will probably be vastly favorable to one side of the reaction).
Edit: as an example regarding the intraconversion of energy and mass consider matter-antimatter annihilation. You could set this up similarly as an equilibrium ratio. In most cases this is vastly favorable to energy, for the most part any significant amount of matter and antimatter will spontaneously annihilate to produce energy, and very very rarely will energy spontaneously form matter and antimatter, which when it does happen they will immediately annihilate.
But then consider if we have a way to separate the pairs prior to annihilation, like the event horizon of a black hole. At that point a particle antiparticle pair will form with mass but not be able to immediately annihilate and energy will be spent in the formation, ie Hawking radiation. Eventually in this matter a huge amount of energy (which ultimately comes from the mass of the black hole itself)will be backconverted into particles with mass. The E=mc^2 equation will run backwards.
The kugelblitz also runs the equation backwards but in a different way, ultimately black hole formation is dependent on energy density, it doesn’t give a shit what form the energy is in, but in most conditions mass under extreme gravity is the only situation that would naturally occur where energy density would be that high. But the no hair principle says that a black hole can only have 3 properties: mass, charge, and angular momentum. So any energy consumed in its formation must be converted to mass.
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MorninglordI'm tired of being Batman,so today I'll be Owl.Registered Userregular
They are if entropy is involved. And entropy is involved.
I don't see how this applies to a kugelblitz.
The actual answer is that we do not know how or if equations are one way. Like for real don’t know
So you are saying a kugelblitz is not possible. Or we do not know if this is possible.
Either statement, I think, requires a fair amount of backup.
I understand that I overdramatically said a generalised statement, for which I apologise. I really just meant in this specific case. Let us walk that statement back to this specific case, and proceed from there in all future discussion.
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They are if entropy is involved. And entropy is involved.
I don't see how this applies to a kugelblitz.
The actual answer is that we do not know how or if equations are one way. Like for real don’t know
So you are saying a kugelblitz is not possible. Or we do not know if this is possible.
Either statement, I think, requires a fair amount of backup.
I understand that I overdramatically said a generalised statement, for which I apologise. I really just meant in this specific case. Let us walk that statement back to this specific case, and proceed from there in all future discussion.
We don't really know. On the one hand, we *do* know that in our laws of physics you can gather enough energy to create a black hole. On the other hand, the *amount* of energy involved is so high that we aren't actually sure our laws of physics will still apply or what will take their place.
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MorninglordI'm tired of being Batman,so today I'll be Owl.Registered Userregular
They are if entropy is involved. And entropy is involved.
I don't see how this applies to a kugelblitz.
The actual answer is that we do not know how or if equations are one way. Like for real don’t know
So you are saying a kugelblitz is not possible. Or we do not know if this is possible.
Either statement, I think, requires a fair amount of backup.
I understand that I overdramatically said a generalised statement, for which I apologise. I really just meant in this specific case. Let us walk that statement back to this specific case, and proceed from there in all future discussion.
We don't really know. On the one hand, we *do* know that in our laws of physics you can gather enough energy to create a black hole. On the other hand, the *amount* of energy involved is so high that we aren't actually sure our laws of physics will still apply or what will take their place.
Fair enough. I still don't see how entropy is relevant in this case? Now you are talking about the potential for crazy whack unknown physics, whereas that was a more conventional point.
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ChanusHarbinger of the Spicy Rooster ApocalypseThe Flames of a Thousand Collapsed StarsRegistered Userregular
i think there's a misapplication of entropy at play here
entropy is why the heat death of the universe will likely happen before a dropped coffee mug unsmashes itself but the process itself is 100% reversible
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MorninglordI'm tired of being Batman,so today I'll be Owl.Registered Userregular
edited May 2022
Yeah I take reversible in the case of entropy being "what if you could literally rewind the universe like a movie would it go back to what it was before" and if you claim that can't happen you are saying something really quite strange.
Entropy must be reversible. It's just that once it has happened, while the movie plays, we can't do it. That's different from "it would be impossible to reverse the process if time itself was going backwards".
Although I guess it gets finicky cos I think the second law of thermodynamics is kind of used like a "proof" - as close as you can get to such a thing - that time is a one way street but you get the idea.
My problem here is mainly why entropy was brought up re the process of jamming tons of light into a very small space? I don't really see how that applies.
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They are if entropy is involved. And entropy is involved.
I don't see how this applies to a kugelblitz.
The actual answer is that we do not know how or if equations are one way. Like for real don’t know
So you are saying a kugelblitz is not possible. Or we do not know if this is possible.
Either statement, I think, requires a fair amount of backup.
I understand that I overdramatically said a generalised statement, for which I apologise. I really just meant in this specific case. Let us walk that statement back to this specific case, and proceed from there in all future discussion.
We do not actually know. There are a fair bit of things suggested by the math that are kind of ridiculous. On the other hand we have observed a fair few things predicted by the math that we thought were ridiculous.
But fundamentally the math is something we wrote down in order to describe the world. It’s correctness and reversibility only holds insomuch as the math accurately reflects the real world. And nothing in any equations, until verified, is true. Because the math is derived from the real world and not the other way around. We have only ever observed time flow in one direction. That equations which involve it will accept any input for time does not mean time can flow backwards.
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MorninglordI'm tired of being Batman,so today I'll be Owl.Registered Userregular
edited May 2022
Then why are they using equations to describe it?
This seems like an inappropriate mathematization of a concept if they have no basis for it following the basic rules of mathematics.
Also, the equation in this case that we are talking about is E=mc^2 and correct me if I am wrong but time is not a part of that, right? So that doesn't really matter here?
The thought experiment involved here does not rely on reversing time in order to create the black hole out of light. It's super simple: add lots of energy to a small space. That is technically but perhaps not practically possible, without asking for time to change in anyway, other than to continue on working like it always has.
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ChanusHarbinger of the Spicy Rooster ApocalypseThe Flames of a Thousand Collapsed StarsRegistered Userregular
time reversibility is something we "don't know" in a purely academic sense where, sure, it underpins our entire understanding of everything, and is related to countless observations we've made over more than a century, but yes, we can't empirically state it is true
a kugelblitz is an absurdity that is fully possible according to the math, and we have absolutely no chance of discovering whether or not it actually is possible any time conceivably soon, but it's a fun and interesting thing to think about
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Wouldn't that also mean that time has become a space like dimension? Could this be a rotation of the coordinate plane of four dimensional space, and everything still works once it cools down enough to form normal matter again?
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I feel like this is where some confusion started. I agree that this is a very good sign that the universe is center less, and was trying to ask my questions from the idea that I'm not sure how it could have a finite, objective center, without observable redshift variations.
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There is another theory which states that this has already happened.”
― Douglas Adams, The Restaurant at the End of the Universe
I enjoy reading cosmology but I am not sure I grasp it at a much deeper level than I can appreciate the muppets on.
I've always heard it takes too much energy to fire someone into the sun, I assume a local black hole would be super-useful because it would overcome this issue while also being a worse punishment than be fired into the sun?
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Steam: Korvalain
I was thinking like, we could build a really far out space station and learn physics from it and stuff, but your idea works too.
Although the cool part is that if it's only about Earth-mass, then the gravity of it is similar and it would be tiny, so you could fly right up to it, shimmy down on a rope and feel spacetime get all screwy if you put your hand near it.
If planet 9 were a black hole, it would have a very small event horizon given because it would be a planet mass black hole. Such a thing shouldn’t exist unless it is a primordial black hole (PBH). That means dark matter (DM) would likely consist of PBHs, which would solve the whole DM composition issue.
It would be a monumental discovery.
I agree it seems similar on the surface, its just that you and I might have different observable universes, but most of it overlaps since we are so close to each other. So if you take black hole = observable universe then you and I are two black holes right next to each other whose event horizons heavily overlap and that's...
...that starts getting weird.
Not weird as in impossible.
Weird as in "how is this useful as a way to think about inflation?"
The thought experiment works if you only ever take a single observer and match them to a black hole's singularity. That's not really how this works tho, since every single point in space has it's own "event horizon" observable universe, all right next to each other.
So like, everypoint in space is the singularity of its own black hole. If that's the case how come I'm able to walk down the street?
I dunno I think it just gets more confusing instead of less. I think the point of analogies should be to enhance understanding, not...confuse the fuck out of you, if you get what I mean.
So if I understand correctly, if you imagine what a white hole would look like from the inside you end up with something that looks a lot like the visible universe - inside the white hole you would see matter disappear at the edges and an event horizon that would radiate hawking radiation back into the system. The observable universe both does not have a center and from any vantage point looks like a white hole with the observer at the center? I feel like that is significant somehow.
Also I guess based on movement of galaxies no matter where you are in the universe it would appear that the big bang happened in the past right where you are observing from?
Wouldn't tiny black holes be detectable though from emissions and gravitational lensing?
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With an accretion disk, it should be detectable by it's emissions, and so if it existed likely would have been seen by now. If there's no accretion disk, then no, it wouldn't be giving off any detectable emissions. And it's small mass would only bend light very slightly, below the angular resolution of our best telescopes, so it wouldn't be detectable by gravitational lensing. Though you might get lucky and detect it via occlusion of distant stars.
There are definitely large yet-to-be-observed objects in our system (some brewing in my gut at the moment even), but a planet?
if it's not reflecting light or passing in front of a nearby source of light, it's really hard to see it, even if it's planet sized
we don't really have any evidence it's there other than other things in the region moving slightly differently than we'd expect otherwise
We could easily miss a planet. Potentially for centuries more.
*-The evidence for planet 10 is that the apohelions of many Kuiper belt dwarf planets are on a similar vector, which can happen with eccentric orbits in close resonance with a larger object in a more circular orbit.
However because of the way we found them and the limited number of facilities involved, we found a disproportionate number in a small area of sky. So there is a bias in our data set that's simply impossible to correct for at this time.
E=mc^2. C is constant so if you add E it makes m go up.
Extreme example: a kugelblitz. Pump enough energy - be it heat or light or just a lot of kinetic energy on a very small object - into a small enough space and you have a black hole made of nothing.
Science, answering the questions nobody asked for the past few thousand years.
But a kugelblitz involves fundamentally breaking the universe - channeling thousands of stars worth of energy into a space a few millimeters across to create temperatures so high that temperature starts to have gravity. The end product isn't even particularly dangerous but the process of creating it is Fall of Adam level shit, like God might just renege on the deal after this one.
mass is energy
The Monster Baru Cormorant - Seth Dickinson
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ummm... when you wack two massive things together, isn't the energy is imparted by massless particles?
electon shells repell each other, emf is transmitted by photons?
Perhaps another way to reword your question if you think of a photon as a packet of energy is "how can energy hit a particle and impart energy?" to realize you were asking the wrong question. The real question is "how does a massless particle have momentum?"
And that is because E=mc^2 is actually a simplification. For an object in motion you need to add a momentum term such that E^2 = (mc^2)^2 + (pc)^2. For an object with no mass, this simplifies to show momentum p=E/c.
A photon, while not having rest mass, because it has energy it will still have momentum. Since it has momentum it can hit another particle and impart that momentum energy on it to move it.
They are if entropy is involved. And entropy is involved.
I don't see how this applies to a kugelblitz.
The actual answer is that we do not know how or if equations are one way. Like for real don’t know
Your point is basically mass energy is basically just one thing for the purpose of general relativity?
This seems to be generating more controversy than it deserves.
Actually if I remember my PChem was right this isn’t true.
Most physical process if occurring commonly enough on a large enough scale to be statistically analyzed en masse should be expressible in broadly the same way as a chemical reaction.
In a chemical reaction there is always an equillibrium. In a given reaction mixture you will have a proportion of the products and a proportion of the reactants as determined by the entropy of the reactants, the entropy of the products, and the entropy of the energy released or absorbed in the process.
The important thing is that in any system normally the product and reactants will be present in some proportion. There is always a proportion of the reactions running “backward” The interesting thing is that if you perform work on a system you can “push” the equillibrium one way or another.
For example, consider the formation of water from elemental oxygen and hydrogen. In a normal reaction mixture water is VASTLY favored. So consider a glass bubble full of heated steam. Very little of that steam will spontaneously convert to H2 and O2, any any that does will almost immediately react back to H2O. The fraction is actually 2.4E47 to 1 water to elemental H2 and O2. So when you say even under high temperatures very little H2O will dissociate to h2 and o2, it really is very little.
However, instead of steam under high temperature lets have liquid water with a high current running through it. Water is still vastly favored in this situation but importantly when any elemental hydrogen and oxygen forms it bubbles out of the sysytem. This seperates the oxygen and hydrogen from the reaction mixture which affects the equilibrium (the reaction is mow essentially determined by several different equilibriums, the equilibrium in the water itself and the equilibrium of hydrogen and oxygen gas disolving in the water to make it available to react (actually that is a simplification because the elecrodes also cause H3O+ and OH- ions to concentrate within solution which also affects things).
Anyway, by modifiying the physical situation and source of the energy we have now shifted an equilibrium very unfavorable to H2 and O2 to one more favorable to them. There will now be a fairly significant amount of H2 and O2 present in the system (note that you have to put energy into the system for this to work by running a current through the water). By doing this we have indirectly changed the equilibrium of the system by doing work on the system.
But wait, there is also something else we can do!
You can get a pump and pump out the oxygen and hydrogen gas from the system. This will drive the equilibrium even further towards the elemental gases, because when you remove them a new equilibrium forms between the lesser amount of elemental gasses and the water.
So the point is that by doing work on the system and presumably incurring entroy somewhere else you can drive a process that would normally be vastly thermodynamicslly favorable in one direction to other direction.
I would assume in a situation involving the intraconversion of matter to energy these same rules involving equilibrium and reversibility would apply (although depending on situation it will probably be vastly favorable to one side of the reaction).
Edit: as an example regarding the intraconversion of energy and mass consider matter-antimatter annihilation. You could set this up similarly as an equilibrium ratio. In most cases this is vastly favorable to energy, for the most part any significant amount of matter and antimatter will spontaneously annihilate to produce energy, and very very rarely will energy spontaneously form matter and antimatter, which when it does happen they will immediately annihilate.
But then consider if we have a way to separate the pairs prior to annihilation, like the event horizon of a black hole. At that point a particle antiparticle pair will form with mass but not be able to immediately annihilate and energy will be spent in the formation, ie Hawking radiation. Eventually in this matter a huge amount of energy (which ultimately comes from the mass of the black hole itself)will be backconverted into particles with mass. The E=mc^2 equation will run backwards.
The kugelblitz also runs the equation backwards but in a different way, ultimately black hole formation is dependent on energy density, it doesn’t give a shit what form the energy is in, but in most conditions mass under extreme gravity is the only situation that would naturally occur where energy density would be that high. But the no hair principle says that a black hole can only have 3 properties: mass, charge, and angular momentum. So any energy consumed in its formation must be converted to mass.
So you are saying a kugelblitz is not possible. Or we do not know if this is possible.
Either statement, I think, requires a fair amount of backup.
I understand that I overdramatically said a generalised statement, for which I apologise. I really just meant in this specific case. Let us walk that statement back to this specific case, and proceed from there in all future discussion.
We don't really know. On the one hand, we *do* know that in our laws of physics you can gather enough energy to create a black hole. On the other hand, the *amount* of energy involved is so high that we aren't actually sure our laws of physics will still apply or what will take their place.
Fair enough. I still don't see how entropy is relevant in this case? Now you are talking about the potential for crazy whack unknown physics, whereas that was a more conventional point.
entropy is why the heat death of the universe will likely happen before a dropped coffee mug unsmashes itself but the process itself is 100% reversible
Entropy must be reversible. It's just that once it has happened, while the movie plays, we can't do it. That's different from "it would be impossible to reverse the process if time itself was going backwards".
Although I guess it gets finicky cos I think the second law of thermodynamics is kind of used like a "proof" - as close as you can get to such a thing - that time is a one way street but you get the idea.
My problem here is mainly why entropy was brought up re the process of jamming tons of light into a very small space? I don't really see how that applies.
We do not actually know. There are a fair bit of things suggested by the math that are kind of ridiculous. On the other hand we have observed a fair few things predicted by the math that we thought were ridiculous.
But fundamentally the math is something we wrote down in order to describe the world. It’s correctness and reversibility only holds insomuch as the math accurately reflects the real world. And nothing in any equations, until verified, is true. Because the math is derived from the real world and not the other way around. We have only ever observed time flow in one direction. That equations which involve it will accept any input for time does not mean time can flow backwards.
This seems like an inappropriate mathematization of a concept if they have no basis for it following the basic rules of mathematics.
Also, the equation in this case that we are talking about is E=mc^2 and correct me if I am wrong but time is not a part of that, right? So that doesn't really matter here?
The thought experiment involved here does not rely on reversing time in order to create the black hole out of light. It's super simple: add lots of energy to a small space. That is technically but perhaps not practically possible, without asking for time to change in anyway, other than to continue on working like it always has.
a kugelblitz is an absurdity that is fully possible according to the math, and we have absolutely no chance of discovering whether or not it actually is possible any time conceivably soon, but it's a fun and interesting thing to think about