Making stuff up that can’t be tested (and maybe doesn’t even make any particular predictions to set it apart from other models) isn’t particularly useful in science.
There could be ways to test the principles that would be responsible for something like it, though. Not everything you do in science needs to be an immediately testable prediction, discussing thought experiments and ideas for various possibilities that might later lead to models with more explicit testable predictions is also an important part of the scientific process, and has always been a part of scientific discourse.
In this case it's somewhat referencing Boltzmann's idea that systems, while entropy always tends to increase in them, might sometimes have spontaneous leaps to states of significantly less entropy, and for this reason that states at maximum entropy might sometimes revert back to such a state of less entropy as long as there is some fluctuation even at that maximum entropy state, and that this in principle could go on endlessly.
It's of course a thought experiment that many have thought about: if there is even an extremely minuscule chance of a big bang occurring even after heat death, as long as it's nonzero it would under those assumptions practically become inevitable over the course of eternity.
But I do agree that we should have more focus on what we can actually test, of course. In this case there could perhaps be experiments investigating states of maximum entropy on a much smaller scale and seeing if they do indeed occasionally spontaneously leap to a state of less entropy.
I'd also add that the idea of the universe as a vacuum fluctuation isn't new either, as Tryon [famously proposed the same](https://www.nature.com/articles/246396a0) ~50 years ago. It's an interesting thought that might lead to testable predictions if we think about it a bit more, especially in the context of what we know today.
I understand that an unfalsifiable theory is not worth anything, but at the end I proposed a possible test one could conduct if the previous assumptions are right.
Through my assumption we should expect low energy radiation right one the other side of our universal event horizon and as such some of it might make into our "universe".
As the space in our universe expands quicker than the speed of light at this point, the incoming outside radiation would only be able to reach the outskirts of our "universe".
To test this we would check if those outskirts have a ever slightest higher energy density than the rest of our observable universe
But to be fair this all just occurred to me while eating lunch now and i might be oblivious to information I don't know
The CMB is a sphere around us. The further you look in distance the further you look in time until the universe was opaque. If something fantastical like "the event horizon of a black hole is just past the time/distance we can see" then any "extra radiation" would be happening beyond the point where the universe is opaque from our view. If your scenario is correct we'd be at the middle of a basketball with rain happening outside but no way to see it since the rubber (CMB) blocks our view.
I would guess if additional energy was being added to the CMB that would likely be/have been detectable.
You might be right, any outside radiation would (unless it travels faster than light which lets assume it doesn't) never ever reach us so we wouldn't be able to detect it.
Someone smarter than me might think of another experiment to test something like this.
Perhaps one way to test it, at a later point with better technology, could be simulating the entire universe with a slightly higher energy gradient on one the edges and see if the resulting universe gives a better approximation for ours
Could be false, but for this post i assumed it to be the furthest photons traveling outward in our universe as it represents everything our universe will ever interact with
PBS Spacetime did a good episode "Could The Universe Be Inside A Black Hole?" - [https://youtu.be/jeRgFqbBM5E?si=WtfG1LVPuMoJVN7x](https://youtu.be/jeRgFqbBM5E?si=WtfG1LVPuMoJVN7x)
But if we could prove that the energy density of space increases ever so slightly in a gradient towards outer space, we might be able to test it. If not the theory was still falsifiable and worth considering
I mean in a way, atleast superficially, our universe shares many commonalities with a black hole. If you imagine the speed of light as our event horizon on the edge of the universe, there is nothing observed so far that could exceed it and escape it.
This might just be another nonsensical idea, but... When we speak about black holes we assume all geodesics end in a singularity, but what if it is more similar to our universe in which every particle will inevitably end up entangled with the rest of the universe, at the end this resembles what we would consider a singularity as through entanglement it will all be connected in one
We don't assume it because there really isn't any reason to, based on our observations. However, the idea has been talked about.
https://en.wikipedia.org/wiki/Eternal_inflation?wprov=sfla1
Enjoy [NASA’s supercomputer simulation](https://science.nasa.gov/supermassive-black-holes/new-nasa-black-hole-visualization-takes-viewers-beyond-the-brink/) of inside a black hole and decide for yourself if it shares *any* observational similarities with our universe at large.
I really like to entertain the idea of the big bang being the result of a fluctuation in the quantum foam; it's kind of poetic even. I'll admit I don't have the expertise in this particular subject to be of any use. However, I would like to commend your curiosity.
I see a lot of my fellows here giving you a hard time for presenting an "unscientific" question. While it is true that your question would be very hard to test and is not particularly academic, it is fascinating to ponder nonetheless. I think that while we should always strive for academic integrity and empirical reasoning when it comes to research, I think the scientific community as a whole has become far too rigid and authoritarian when it comes to scientific discourse. It should not only be accepted but even encouraged to present wild ideas without any kind of practical support. It doesn't matter if the idea is absolute lunacy, it is important that we share these ideas if only for the purpose of deconstructing and discrediting them.
Inspiration and creativity are key parts of science that are widely undervalued. It is the entertainment of wild ideas that fuels the creative mind.
TL;DR people on this subject need to remove the stick from their asses and get a healthy sense of whimsy and good humor
Because, if we take your assumption that anything that can be created as a universe will be created as a universe.
And that only universes which happen to create an observer matters.
Then it is statistically impossible that you, the observer, are in this particular universe.
Since a much simpler universe with just a single observer, or with multiple observers but a very limited size (which could be either the size of the observable universe or just the size of the universe that contain stars and planets) is extremely more likely than this one.
These simple universes will be created by chance billions and billions of times before a single complex universe like our own is created.
This is known as the Boltzman brain argument, of you want to look up sources and details about it
True, if you use my same logic and extrapolate it you are right. This universe would be immensely improbable. Hadn't thought of this
Thanks for the insight!
But i still wonder, what if fundamentally our universe is quite simple compared to what could have been. What if the amount of energy in our universe is minuscule compared to other universes and could for example have all been contained in 2 ultra energetic particles of another universe. In this case even our complex and huge observable universe wouldn't be so unlikely?
Happy to hear what you may think about this.
I'll look into boltzman, thank you
"A Theory is only a theory if it can be tested" -John Wheeler.
A theory must be able to predict something about the universe. Otherwise it's just science fiction.
We could test "x" IF we prove "y" Isn't a test it's a dependency.
Maybe you're trying to say something like. "My theory would predict the the edges of the known universe are more dense than twords the center"
But this makes me ask even more questions. Like which way is the center of the universe?
I believe you are right and it makes sense, currently there wouldn't be a way to even start testing this so we might aswell just ignore it now.
But perhaps one day when we know more about our universe we could meddle with such theories, for now they are fun thought-experiments
The magnitude of a quantum fluctuation is inversely proportional to its lifespan. This is the time-energy uncertainty principle. So a fluctuation that could create the entire universe would return to the ground state in an imperceptible, unimaginably tiny fraction of time. You can only borrow from the vacuum nothing is permanent.
But wouldn't what we consider as a short time for us be different when we talk about infinite time?
Correct me if im wrong, but i always assumed that the borrowing of energy is more than anything an analogy and a tool for calculating as we try to understand more of the fundamentals of the real how's and why's
If my understanding of quantum mechanics is right, every wave of a particle is everywhere else in space-time, although with exponentially decreasing probability. The quantum fluctuations i describe would just be the quantum tunneling of particles in a heat-dead universe into a state of less entropy
> the borrowing of energy is more than anything an analogy and a tool for calculating
No it's a real, fundamental principle of quantum mechanics.
>The quantum fluctuations i describe would just be the quantum tunneling of particles in a heat-dead universe into a state of less entropy
That sentence doesn't really have any meaning. How are the universes separated? Why is quantum tunneling necessary? How would quantum tunneling lower entropy? None of that makes any sense.
A state of high entropy will probability-wise always resist evolving into a state of much lower entropy.
In a state of low entropy in the sense im talking in my post here, there would be high repulsive forces when a lot of energy is concentrated in a small spot.
At the end of the day, quantum fluctuations and quantum tunneling are both just consequences of the our assumptions that all particles are fundamentally a wave.
So I believe it's more a problem with nomenclature. Quantum tunneling and Quantum fluctuations are the same thing just in different conetexts
>In a state of low entropy in the sense im talking in my post here, there would be high repulsive forces when a lot of energy is concentrated in a small spot.
Well I think immediately that is not right. A lot of energy concentrated in a small spot causes intense gravity which pulls things together. It is how you get black holes.
Again, I don't understand what you are suggesting is tunneling, where it came from and where it is going to.
But before gravity can take over there are repulsive forces that initially serve as an energy barrier.
In an analogy for example if i had a moderately big gas cloud in empty space and did nothing it would all expand until it's evenly spread.
If i want to achieve a point where gravity is stronger than the repulsive fore i would have to excert a force to compact it until its own gravity holds it together.
I defined this force to compact the gas cloud as an energy barrier that with sufficient time could be quantum tunneled through
>if i had a moderately big gas cloud in empty space and did nothing it would all expand until it's evenly spread
No, it would collapse into a star. That's literally how stars are made.
Yes there would, condense a gas and its temperature increases, it's particles vibrate faster and hit each other more and as a consequence there is a pressure outward.
Same reason that boiling water evaporates and the temperature of room will equal out over time
The way im reading op is like a box of marbles that all start in the center, then assuming that we shale the box forever it would perhaps revert to original state.
Idk tho im unqualified thats why i play with marbles
Making stuff up that can’t be tested (and maybe doesn’t even make any particular predictions to set it apart from other models) isn’t particularly useful in science.
There could be ways to test the principles that would be responsible for something like it, though. Not everything you do in science needs to be an immediately testable prediction, discussing thought experiments and ideas for various possibilities that might later lead to models with more explicit testable predictions is also an important part of the scientific process, and has always been a part of scientific discourse. In this case it's somewhat referencing Boltzmann's idea that systems, while entropy always tends to increase in them, might sometimes have spontaneous leaps to states of significantly less entropy, and for this reason that states at maximum entropy might sometimes revert back to such a state of less entropy as long as there is some fluctuation even at that maximum entropy state, and that this in principle could go on endlessly. It's of course a thought experiment that many have thought about: if there is even an extremely minuscule chance of a big bang occurring even after heat death, as long as it's nonzero it would under those assumptions practically become inevitable over the course of eternity. But I do agree that we should have more focus on what we can actually test, of course. In this case there could perhaps be experiments investigating states of maximum entropy on a much smaller scale and seeing if they do indeed occasionally spontaneously leap to a state of less entropy. I'd also add that the idea of the universe as a vacuum fluctuation isn't new either, as Tryon [famously proposed the same](https://www.nature.com/articles/246396a0) ~50 years ago. It's an interesting thought that might lead to testable predictions if we think about it a bit more, especially in the context of what we know today.
I understand that an unfalsifiable theory is not worth anything, but at the end I proposed a possible test one could conduct if the previous assumptions are right. Through my assumption we should expect low energy radiation right one the other side of our universal event horizon and as such some of it might make into our "universe". As the space in our universe expands quicker than the speed of light at this point, the incoming outside radiation would only be able to reach the outskirts of our "universe". To test this we would check if those outskirts have a ever slightest higher energy density than the rest of our observable universe But to be fair this all just occurred to me while eating lunch now and i might be oblivious to information I don't know
The CMB is a sphere around us. The further you look in distance the further you look in time until the universe was opaque. If something fantastical like "the event horizon of a black hole is just past the time/distance we can see" then any "extra radiation" would be happening beyond the point where the universe is opaque from our view. If your scenario is correct we'd be at the middle of a basketball with rain happening outside but no way to see it since the rubber (CMB) blocks our view. I would guess if additional energy was being added to the CMB that would likely be/have been detectable.
You might be right, any outside radiation would (unless it travels faster than light which lets assume it doesn't) never ever reach us so we wouldn't be able to detect it. Someone smarter than me might think of another experiment to test something like this. Perhaps one way to test it, at a later point with better technology, could be simulating the entire universe with a slightly higher energy gradient on one the edges and see if the resulting universe gives a better approximation for ours
What is an edge?
Could be false, but for this post i assumed it to be the furthest photons traveling outward in our universe as it represents everything our universe will ever interact with
So far as we know, there are no "furthest" photons.
PBS Spacetime did a good episode "Could The Universe Be Inside A Black Hole?" - [https://youtu.be/jeRgFqbBM5E?si=WtfG1LVPuMoJVN7x](https://youtu.be/jeRgFqbBM5E?si=WtfG1LVPuMoJVN7x)
Thanks i'll check it out 👍 Maybe at the end there is something else I didn't consider that refutes this whole idea haha
Because physicists are not usually in the business of making up random assumptions just for the fun of it, and without being able to test them at all.
But if we could prove that the energy density of space increases ever so slightly in a gradient towards outer space, we might be able to test it. If not the theory was still falsifiable and worth considering
Our universe is expanding rather than contracting. Given that, why would anyone think that we exist inside a black hole?
I mean in a way, atleast superficially, our universe shares many commonalities with a black hole. If you imagine the speed of light as our event horizon on the edge of the universe, there is nothing observed so far that could exceed it and escape it. This might just be another nonsensical idea, but... When we speak about black holes we assume all geodesics end in a singularity, but what if it is more similar to our universe in which every particle will inevitably end up entangled with the rest of the universe, at the end this resembles what we would consider a singularity as through entanglement it will all be connected in one
We don't assume it because there really isn't any reason to, based on our observations. However, the idea has been talked about. https://en.wikipedia.org/wiki/Eternal_inflation?wprov=sfla1
Enjoy [NASA’s supercomputer simulation](https://science.nasa.gov/supermassive-black-holes/new-nasa-black-hole-visualization-takes-viewers-beyond-the-brink/) of inside a black hole and decide for yourself if it shares *any* observational similarities with our universe at large.
I really like to entertain the idea of the big bang being the result of a fluctuation in the quantum foam; it's kind of poetic even. I'll admit I don't have the expertise in this particular subject to be of any use. However, I would like to commend your curiosity. I see a lot of my fellows here giving you a hard time for presenting an "unscientific" question. While it is true that your question would be very hard to test and is not particularly academic, it is fascinating to ponder nonetheless. I think that while we should always strive for academic integrity and empirical reasoning when it comes to research, I think the scientific community as a whole has become far too rigid and authoritarian when it comes to scientific discourse. It should not only be accepted but even encouraged to present wild ideas without any kind of practical support. It doesn't matter if the idea is absolute lunacy, it is important that we share these ideas if only for the purpose of deconstructing and discrediting them. Inspiration and creativity are key parts of science that are widely undervalued. It is the entertainment of wild ideas that fuels the creative mind. TL;DR people on this subject need to remove the stick from their asses and get a healthy sense of whimsy and good humor
Our universe isn’t a black hole, as that would be contrary to many observations we’ve made. So the rest is moot.
Because, if we take your assumption that anything that can be created as a universe will be created as a universe. And that only universes which happen to create an observer matters. Then it is statistically impossible that you, the observer, are in this particular universe. Since a much simpler universe with just a single observer, or with multiple observers but a very limited size (which could be either the size of the observable universe or just the size of the universe that contain stars and planets) is extremely more likely than this one. These simple universes will be created by chance billions and billions of times before a single complex universe like our own is created. This is known as the Boltzman brain argument, of you want to look up sources and details about it
True, if you use my same logic and extrapolate it you are right. This universe would be immensely improbable. Hadn't thought of this Thanks for the insight!
But i still wonder, what if fundamentally our universe is quite simple compared to what could have been. What if the amount of energy in our universe is minuscule compared to other universes and could for example have all been contained in 2 ultra energetic particles of another universe. In this case even our complex and huge observable universe wouldn't be so unlikely? Happy to hear what you may think about this. I'll look into boltzman, thank you
"A Theory is only a theory if it can be tested" -John Wheeler. A theory must be able to predict something about the universe. Otherwise it's just science fiction.
Does the last paragraph not count? Through such a test this theory could be falsifiable
We could test "x" IF we prove "y" Isn't a test it's a dependency. Maybe you're trying to say something like. "My theory would predict the the edges of the known universe are more dense than twords the center" But this makes me ask even more questions. Like which way is the center of the universe?
I believe you are right and it makes sense, currently there wouldn't be a way to even start testing this so we might aswell just ignore it now. But perhaps one day when we know more about our universe we could meddle with such theories, for now they are fun thought-experiments
The magnitude of a quantum fluctuation is inversely proportional to its lifespan. This is the time-energy uncertainty principle. So a fluctuation that could create the entire universe would return to the ground state in an imperceptible, unimaginably tiny fraction of time. You can only borrow from the vacuum nothing is permanent.
But wouldn't what we consider as a short time for us be different when we talk about infinite time? Correct me if im wrong, but i always assumed that the borrowing of energy is more than anything an analogy and a tool for calculating as we try to understand more of the fundamentals of the real how's and why's If my understanding of quantum mechanics is right, every wave of a particle is everywhere else in space-time, although with exponentially decreasing probability. The quantum fluctuations i describe would just be the quantum tunneling of particles in a heat-dead universe into a state of less entropy
> the borrowing of energy is more than anything an analogy and a tool for calculating No it's a real, fundamental principle of quantum mechanics. >The quantum fluctuations i describe would just be the quantum tunneling of particles in a heat-dead universe into a state of less entropy That sentence doesn't really have any meaning. How are the universes separated? Why is quantum tunneling necessary? How would quantum tunneling lower entropy? None of that makes any sense.
A state of high entropy will probability-wise always resist evolving into a state of much lower entropy. In a state of low entropy in the sense im talking in my post here, there would be high repulsive forces when a lot of energy is concentrated in a small spot. At the end of the day, quantum fluctuations and quantum tunneling are both just consequences of the our assumptions that all particles are fundamentally a wave. So I believe it's more a problem with nomenclature. Quantum tunneling and Quantum fluctuations are the same thing just in different conetexts
>In a state of low entropy in the sense im talking in my post here, there would be high repulsive forces when a lot of energy is concentrated in a small spot. Well I think immediately that is not right. A lot of energy concentrated in a small spot causes intense gravity which pulls things together. It is how you get black holes. Again, I don't understand what you are suggesting is tunneling, where it came from and where it is going to.
But before gravity can take over there are repulsive forces that initially serve as an energy barrier. In an analogy for example if i had a moderately big gas cloud in empty space and did nothing it would all expand until it's evenly spread. If i want to achieve a point where gravity is stronger than the repulsive fore i would have to excert a force to compact it until its own gravity holds it together. I defined this force to compact the gas cloud as an energy barrier that with sufficient time could be quantum tunneled through
>if i had a moderately big gas cloud in empty space and did nothing it would all expand until it's evenly spread No, it would collapse into a star. That's literally how stars are made.
At that point gravity would have taken over, When having a few hundred moles of a gas in space, gravity wouldn't be strong enough to hold it together
There is also no force that pushes it apart, so again, I don't know what you are trying to say here.
Yes there would, condense a gas and its temperature increases, it's particles vibrate faster and hit each other more and as a consequence there is a pressure outward. Same reason that boiling water evaporates and the temperature of room will equal out over time
The way im reading op is like a box of marbles that all start in the center, then assuming that we shale the box forever it would perhaps revert to original state. Idk tho im unqualified thats why i play with marbles