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> Current data suggest that the universe has a flat geometry (or very close to flat), and thus, will not collapse in on itself after a finite time, and the infi

> Current data suggest that the universe has a flat geometry (or very close to flat), and thus, will not collapse in on itself after a finite time, and the infinite future allows for the occurrence of a number of massively improbable events, such as the formation of Boltzmann brains. I always thought that the universe will just reach zero Kelvin and the party is over. That it will just continue to do improbable stuff was beyond my imagination. I don't really understand how it should be possible that effects like the emergence of virtual particles still work if all the energy is now in a form which can't be used for energy transformations anymore (entropy) - I know that annihilation of anti-particles of virtual particles (which causes them to exist - that was the amazing finding of Hawking with the Hawking radiation where the anti-particles of virtual particles get annihilated at the event horizon and his counterpart is happily living on because he got lucky that he wasn't too close) is a way to form new particles "out of nothing" (using quantum effects), but I still can't believe that this still works when nothing's moving because we're at absolute zero. Could someone explain why those quantum effects still continue to work (and sometimes even spawn particles and even brains if we get lucky) even if the universe is at absolute zero?

mockingbirdy 8y ago
Ok, thanks guys. Quantum uncertainty is the reason we can't reach zero Kelvin, so it's kind of nonsense to ask why quantum effects still work at absolute zero. > It's not physically impossible for order to increase, it's just ridiculously unlikely. Would love to see resources that explain this (I think it comes down to quantum uncertainty again). > the basic idea is that the probability for anything to happen is different than 0 Yeah, quantum uncertainty. Still can't wrap my head around it, but in conversations with physicists, they also weren't sure why the heck it works that way. Gonna read my quantum mechanics book, but the math is not easy-going and especially quantum logic with its 3 states (true, false and flying spaghetti monster superposition) is extremely difficult to grasp using intuition. It contains a lot of thinking from statistics which essentially is just extremely unintuitive as well. - - - Edit: I really wonder if something like a "gravitational quantum electrodynamics" (don't know if we achieve it with this specific theory) or string theory (I don't really like it due to its unscientific nature) - in essence a Theory of Everything - will really explain everything like it really is or just happens to be a fitting model without being any meaningful representation of reality (in the sense that it explains how the underlying reality really looks like). We won't be able to verify if our models are actually representing reality anyways (any theory that explains all observed events and which has some plausible and strong predictions can be treated as a possible reality), but would be nice to know. Guess it can't physically happen, unfortunately.
- duckerude 8y ago
  Imagine you have a box with red marbles and blue marbles. You start shaking it. The marbles get mixed up. Pretty soon, they're completely mixed up. That's maximum entropy. Now imagine you keep shaking the box for a few years or so. Just by sheer coincidence, they might end up neatly sorted for a few seconds every now and then. That's like a Boltzmann brain. I think that's all there is to it in principle, but I'm not very informed.
  - mockingbirdy 8y ago
    > you keep shaking the box for a few years or so That was the part I was unsure about: Does the universe keep on shaking? The answer seems to be: Due to quantum uncertainty - yes. Why? No one really knows because we don't have a god-damn clue about why the universe works the way it works (although we have a good understanding how the universe works in many points, but not a coherent theory or framework that gives a conflict-free explanation).
    - duckerude 8y ago
      Why wouldn't it keep on shaking? Energy doesn't go away. Things don't necessarily stop moving. Again - the universe doesn't cool down to absolute zero. It's called "heat death" for a different reason. You don't need anything quantum for this. Simple Newtonian mechanics seem enough.
      - mockingbirdy 8y ago
        I thought that an equilibrium in which the energy is distributed evenly is a state which the universe can reach. In that state, there wouldn't be something that shakes after a long while. But yeah, maybe energy conservation principles alone can explain that it keeps shaking. But it still feels so unintuitive that it doesn't slow down or cool down. I still have those other models in mind that the universe expands and then collapses or it keeps on expanding (which seems to be the case) or simply stop to expand but also doesn't collapse (and proceed to have maximum entropy level). Those were the three models I got taught. It seems that the universe is flat and will expand endlessly, so the model I thought is right (the universe just stops to expand) isn't true and my related assumptions (that maximum entropy levels get reached and absolute zero) are also not true (for some different reasons like quantum certainty and - it seems - even simple Newtonian mechanics). related SMBC: https://www.smbc-comics.com/comic/2014-06-02 https://www.smbc-comics.com/comic/2014-06-02
21 8y ago
Not a physicist, but the basic idea is that the probability for anything to happen is different than 0, even if extremely small. The quantum fields can't ever be zero, from my understanding. And thus stuff can still happen: > According to Fowler & Guggenheim (1939/1965), the third law of thermodynamics may be precisely enunciated as follows: It is impossible by any procedure, no matter how idealized, to reduce any assembly to the absolute zero in a finite number of operations.
duckerude 8y ago
My understanding of it is that it wouldn't reach zero Kelvin. The heat only becomes uniformly distributed. Everything becomes maximally disorderly. Things move, but all interesting information is gone. But order is probabilistic. It's not physically impossible for order to increase, it's just ridiculously unlikely. If you wait long enough (really long) it'll probably happen some time. I don't think quantum effects are especially related, except to the extent they relate to everything.
- Robotbeat 8y ago
  That’s the crazy thing about large numbers like these. Even Entropy’s Heat Death are swallowed up by them. Not only do such events become probable but they become inevitable an endless number of times over a long enough timescale. Infinity kills even Heat Death.
  - mockingbirdy 8y ago
    I will start to use this in rock-paper-scissors-infinity. But first I have to deeply realize that I'm just one out of all possible ones and that I exist infinitely times and also infinitely times where I finally have a beard.
sixdimensional 8y ago
The thing that confuses me is, if the universe were to reach any type of steady state over infinite time, my question would be, what caused it to be in any other state than steady to begin with? Almost feel like this is a causality question.
- mrep 8y ago
  Well, one of the last timeline events is "Around this vast timeframe, quantum tunnelling in any isolated patch of the vacuum could generate, via inflation, new Big Bangs giving birth to new universes.[108]" Thus, the cycle of new big bangs continue on forever. Granted, the timeline for that is 10^{10^{10^{56}}} which is beyond comprehension soooo.
  - Robotbeat 8y ago
    But these numbers are still tiny compared to numbers mathematicians have created, like Graham’s Number. Which is crazy. These numbers are still finite, still nothing compared to infinity, but they’re plenty big enough to kill Heat Death an almost innumerable number of times.
anonytrary 8y ago
If there is no variance in the position of a particle (it is in a position eigenstate), then there must be an infinite variance in the momentum, which means the particle necessarily has kinetic energy.

mockingbirdy 8y ago

Ok, thanks guys. Quantum uncertainty is the reason we can't reach zero Kelvin, so it's kind of nonsense to ask why quantum effects still work at absolute zero. > It's not physically impossible for order to increase, it's just ridiculously unlikely. Would love to see resources that explain this (I think it comes down to quantum uncertainty again). > the basic idea is that the probability for anything to happen is different than 0 Yeah, quantum uncertainty. Still can't wrap my head around it, but in conversations with physicists, they also weren't sure why the heck it works that way. Gonna read my quantum mechanics book, but the math is not easy-going and especially quantum logic with its 3 states (true, false and flying spaghetti monster superposition) is extremely difficult to grasp using intuition. It contains a lot of thinking from statistics which essentially is just extremely unintuitive as well. - - - Edit: I really wonder if something like a "gravitational quantum electrodynamics" (don't know if we achieve it with this specific theory) or string theory (I don't really like it due to its unscientific nature) - in essence a Theory of Everything - will really explain everything like it really is or just happens to be a fitting model without being any meaningful representation of reality (in the sense that it explains how the underlying reality really looks like). We won't be able to verify if our models are actually representing reality anyways (any theory that explains all observed events and which has some plausible and strong predictions can be treated as a possible reality), but would be nice to know. Guess it can't physically happen, unfortunately.

duckerude 8y ago
Imagine you have a box with red marbles and blue marbles. You start shaking it. The marbles get mixed up. Pretty soon, they're completely mixed up. That's maximum entropy. Now imagine you keep shaking the box for a few years or so. Just by sheer coincidence, they might end up neatly sorted for a few seconds every now and then. That's like a Boltzmann brain. I think that's all there is to it in principle, but I'm not very informed.
- mockingbirdy 8y ago
  > you keep shaking the box for a few years or so That was the part I was unsure about: Does the universe keep on shaking? The answer seems to be: Due to quantum uncertainty - yes. Why? No one really knows because we don't have a god-damn clue about why the universe works the way it works (although we have a good understanding how the universe works in many points, but not a coherent theory or framework that gives a conflict-free explanation).
  - duckerude 8y ago
    Why wouldn't it keep on shaking? Energy doesn't go away. Things don't necessarily stop moving. Again - the universe doesn't cool down to absolute zero. It's called "heat death" for a different reason. You don't need anything quantum for this. Simple Newtonian mechanics seem enough.
    - mockingbirdy 8y ago
      I thought that an equilibrium in which the energy is distributed evenly is a state which the universe can reach. In that state, there wouldn't be something that shakes after a long while. But yeah, maybe energy conservation principles alone can explain that it keeps shaking. But it still feels so unintuitive that it doesn't slow down or cool down. I still have those other models in mind that the universe expands and then collapses or it keeps on expanding (which seems to be the case) or simply stop to expand but also doesn't collapse (and proceed to have maximum entropy level). Those were the three models I got taught. It seems that the universe is flat and will expand endlessly, so the model I thought is right (the universe just stops to expand) isn't true and my related assumptions (that maximum entropy levels get reached and absolute zero) are also not true (for some different reasons like quantum certainty and - it seems - even simple Newtonian mechanics). related SMBC: https://www.smbc-comics.com/comic/2014-06-02 https://www.smbc-comics.com/comic/2014-06-02

21 8y ago

Not a physicist, but the basic idea is that the probability for anything to happen is different than 0, even if extremely small. The quantum fields can't ever be zero, from my understanding. And thus stuff can still happen: > According to Fowler & Guggenheim (1939/1965), the third law of thermodynamics may be precisely enunciated as follows: It is impossible by any procedure, no matter how idealized, to reduce any assembly to the absolute zero in a finite number of operations.

duckerude 8y ago

My understanding of it is that it wouldn't reach zero Kelvin. The heat only becomes uniformly distributed. Everything becomes maximally disorderly. Things move, but all interesting information is gone. But order is probabilistic. It's not physically impossible for order to increase, it's just ridiculously unlikely. If you wait long enough (really long) it'll probably happen some time. I don't think quantum effects are especially related, except to the extent they relate to everything.

Robotbeat 8y ago
That’s the crazy thing about large numbers like these. Even Entropy’s Heat Death are swallowed up by them. Not only do such events become probable but they become inevitable an endless number of times over a long enough timescale. Infinity kills even Heat Death.
- mockingbirdy 8y ago
  I will start to use this in rock-paper-scissors-infinity. But first I have to deeply realize that I'm just one out of all possible ones and that I exist infinitely times and also infinitely times where I finally have a beard.

sixdimensional 8y ago

The thing that confuses me is, if the universe were to reach any type of steady state over infinite time, my question would be, what caused it to be in any other state than steady to begin with? Almost feel like this is a causality question.

mrep 8y ago
Well, one of the last timeline events is "Around this vast timeframe, quantum tunnelling in any isolated patch of the vacuum could generate, via inflation, new Big Bangs giving birth to new universes.[108]" Thus, the cycle of new big bangs continue on forever. Granted, the timeline for that is 10^{10^{10^{56}}} which is beyond comprehension soooo.
- Robotbeat 8y ago
  But these numbers are still tiny compared to numbers mathematicians have created, like Graham’s Number. Which is crazy. These numbers are still finite, still nothing compared to infinity, but they’re plenty big enough to kill Heat Death an almost innumerable number of times.

anonytrary 8y ago

If there is no variance in the position of a particle (it is in a position eigenstate), then there must be an infinite variance in the momentum, which means the particle necessarily has kinetic energy.