5 ms·

We're kinda in the mid-game. We can still see a lot of galaxies and can still reach them. The universe will keep expanding forever and at some point, the co

by edem 8y ago

We're kinda in the mid-game. We can still see __a lot__ of galaxies and can still reach them. The universe will keep expanding forever and at some point, the cosmic event horizon will shrink to the size of our galaxy. There is still a wide variety of stars including supergiants which can seed the galaxy with heavy elements when they go supernova. There will be a time when only Red Dwarves will survive, and after trillions of years the universe will enter a dark age when there are no stars with visible light left.

01100011 8y ago
Do we really know that the expansive forces will continue forever? Is it possible we're living in milk spilled on the floor of some higher dimensional reality and at some point the "surface tension" will override the expansive forces?
- edem 8y ago
  This depends on the cosmological constant (dark energy). There are 3 scenarios: The big rip, the big crunch and equilibrium. In the big rip scenario, dark energy will overpower all other forces and at some point space itself will expand so fast that the cosmic event horizon will be smaller than the smallest particle which means that nothing will be able to reach anything (even particles). In the big crunch scenario expansion will stop at some point and it will reverse and in the end the whole universe will be concentrated in a point (just like before the big bang). Equilibrium means that the expansion stops but does not reverse. What do you mean by "surface tension"?
  - pram 8y ago
    He’s probably referring to supergravity theory.
    - 01100011 8y ago
      No, I am definitely not that informed on the subject :)
  - 01100011 8y ago
    > What do you mean by "surface tension"? I was making an analogy to the behavior of fluids in our reality. Really though, what I was getting at is, do we, or can we, really know the nature of the universe to such a degree that we can rule out behaviors which may change as the universe progresses through whatever sequence of events through which it is progressing? I think you answered my question, such as it was.
    - edem 8y ago
      We don't yet know. Right now the consensus is that the universe will probably expand forever and will ultimately reach heat death. If the acceleration is accelerating though that means a Big Rip scenario, but it is very unlikely.
- opwieurposiu 8y ago
  I am a fan of conformal cyclic cosmology. It sort of goes like this: Pick a spot, that's you. After the big rip, all other particles are beyond your hubble horizon, you can not affect them and they can not affect you. Its just you alone in the void, whiling away the aeons. This is a very low entropy state, just like the start of the big bang. So the very end is indistinguishable from the very beginning, and the cycle starts all over. https://en.wikipedia.org/wiki/Conformal_cyclic_cosmology https://en.wikipedia.org/wiki/Conformal_cyclic_cosmology
sixdimensional 8y ago
"after trillions of years the universe will enter a dark age when there are no stars with visible light left". Ok but, armchair amateur here, the scale of space is not known to humans, right? We cannot comprehend the actual limit of the universe, can we? How can we know that the universe entering a dark age is not a local effect in our known universe, and that other, incomprehensibly distant parts of the universe will keep doing just fine? For that matter, if the universe enters a dark age, what is it that caused the universe to be in a "light age" in the first place? There has be a force that causes the universe to exit a "dark age" otherwise it would always have been dark. These kinds of things perplex me.
- gbrown 8y ago
  Not a physicist, but at a guess: Occam's Razor, plus the existance of simpler theories which explain our current observations.
  - sixdimensional 8y ago
    I think this (Occam's Razor) clearly illustrates the limit of our perception/comprehension though. It is entirely possible that due to our comprehension of the complexity involved with dimensionality, we can be only vaguely aware (if at all) of a more complex system than the one we can perceive/comprehend. I'm reminded of the book Flatland[1]. It is fine to attempt to apply our rubrics, but I am not sure how to quantify the limits of our perception. Perhaps Occam's Razor and current simpler theories give a useful working tool for us to reason within our local known (or perceived/comprehended) universe. The best way I can think of to ask this is, how do we factor in the "unknown unknown"? It is maddening not to be able to. [1] https://en.wikipedia.org/wiki/Flatland https://en.wikipedia.org/wiki/Flatland
    - gbrown 8y ago
      I mean, that's why people do theoretical physics in higher dimensions and then search desperately for ways to test their theories. We can extrapolate with mathematics in infinite ways, but until we can find ways to test things it's hard to do better than "find the simplest explanation that accounts for what you can observe".
Zuider 8y ago
Roger Penrose has speculated that the ultimate heat-death of one universe, the stage where space, time, radiation and matter lose all meaning is identical with the singularity from which a new universe emerges.
- hawaiianbrah 8y ago
  Obligatory mention of Asimov’s The Last Question. Give it a read if you haven’t! Phenomenal short story.
  - arisAlexis 8y ago
    you post a small comment sometimes that opens a random person's horizon. thank you
    - hawaiianbrah 7y ago
      glad you liked it :)
- edem 8y ago
  Note that heat death happens when the universe reaches thermal equilibrium (maximum entropy). It is theorized that sudden drops in entropy are possible which could have caused the big bang.
philipov 8y ago
To be precise, the cosmic event horizon isn't shrinking: it will always remain at the Hubble Distance. However, everything that isn't gravitationally bound to us is receding from us at gradually increasing speed. The cosmic event horizon is the distance when that speed exceeds the speed of light, making it impossible for light to reach us. Just like an object entering a black hole, it will take forever for objects to actually cross the horizon, but they will smear out and redshift, becoming too faint to see, in some finite time.

We're kinda in the mid-game. We can still see __a lot__ of galaxies and can still reach them. The universe will keep expanding forever and at some point, the co

by edem 8y ago

01100011 8y ago

Do we really know that the expansive forces will continue forever? Is it possible we're living in milk spilled on the floor of some higher dimensional reality and at some point the "surface tension" will override the expansive forces?

edem 8y ago
This depends on the cosmological constant (dark energy). There are 3 scenarios: The big rip, the big crunch and equilibrium. In the big rip scenario, dark energy will overpower all other forces and at some point space itself will expand so fast that the cosmic event horizon will be smaller than the smallest particle which means that nothing will be able to reach anything (even particles). In the big crunch scenario expansion will stop at some point and it will reverse and in the end the whole universe will be concentrated in a point (just like before the big bang). Equilibrium means that the expansion stops but does not reverse. What do you mean by "surface tension"?
- pram 8y ago
  He’s probably referring to supergravity theory.
  - 01100011 8y ago
    No, I am definitely not that informed on the subject :)
- 01100011 8y ago
  > What do you mean by "surface tension"? I was making an analogy to the behavior of fluids in our reality. Really though, what I was getting at is, do we, or can we, really know the nature of the universe to such a degree that we can rule out behaviors which may change as the universe progresses through whatever sequence of events through which it is progressing? I think you answered my question, such as it was.
  - edem 8y ago
    We don't yet know. Right now the consensus is that the universe will probably expand forever and will ultimately reach heat death. If the acceleration is accelerating though that means a Big Rip scenario, but it is very unlikely.
opwieurposiu 8y ago
I am a fan of conformal cyclic cosmology. It sort of goes like this: Pick a spot, that's you. After the big rip, all other particles are beyond your hubble horizon, you can not affect them and they can not affect you. Its just you alone in the void, whiling away the aeons. This is a very low entropy state, just like the start of the big bang. So the very end is indistinguishable from the very beginning, and the cycle starts all over. https://en.wikipedia.org/wiki/Conformal_cyclic_cosmology https://en.wikipedia.org/wiki/Conformal_cyclic_cosmology

sixdimensional 8y ago

"after trillions of years the universe will enter a dark age when there are no stars with visible light left". Ok but, armchair amateur here, the scale of space is not known to humans, right? We cannot comprehend the actual limit of the universe, can we? How can we know that the universe entering a dark age is not a local effect in our known universe, and that other, incomprehensibly distant parts of the universe will keep doing just fine? For that matter, if the universe enters a dark age, what is it that caused the universe to be in a "light age" in the first place? There has be a force that causes the universe to exit a "dark age" otherwise it would always have been dark. These kinds of things perplex me.

gbrown 8y ago
Not a physicist, but at a guess: Occam's Razor, plus the existance of simpler theories which explain our current observations.
- sixdimensional 8y ago
  I think this (Occam's Razor) clearly illustrates the limit of our perception/comprehension though. It is entirely possible that due to our comprehension of the complexity involved with dimensionality, we can be only vaguely aware (if at all) of a more complex system than the one we can perceive/comprehend. I'm reminded of the book Flatland[1]. It is fine to attempt to apply our rubrics, but I am not sure how to quantify the limits of our perception. Perhaps Occam's Razor and current simpler theories give a useful working tool for us to reason within our local known (or perceived/comprehended) universe. The best way I can think of to ask this is, how do we factor in the "unknown unknown"? It is maddening not to be able to. [1] https://en.wikipedia.org/wiki/Flatland https://en.wikipedia.org/wiki/Flatland
  - gbrown 8y ago
    I mean, that's why people do theoretical physics in higher dimensions and then search desperately for ways to test their theories. We can extrapolate with mathematics in infinite ways, but until we can find ways to test things it's hard to do better than "find the simplest explanation that accounts for what you can observe".

Zuider 8y ago

Roger Penrose has speculated that the ultimate heat-death of one universe, the stage where space, time, radiation and matter lose all meaning is identical with the singularity from which a new universe emerges.

hawaiianbrah 8y ago
Obligatory mention of Asimov’s The Last Question. Give it a read if you haven’t! Phenomenal short story.
- arisAlexis 8y ago
  you post a small comment sometimes that opens a random person's horizon. thank you
  - hawaiianbrah 7y ago
    glad you liked it :)
edem 8y ago
Note that heat death happens when the universe reaches thermal equilibrium (maximum entropy). It is theorized that sudden drops in entropy are possible which could have caused the big bang.

philipov 8y ago

To be precise, the cosmic event horizon isn't shrinking: it will always remain at the Hubble Distance. However, everything that isn't gravitationally bound to us is receding from us at gradually increasing speed. The cosmic event horizon is the distance when that speed exceeds the speed of light, making it impossible for light to reach us. Just like an object entering a black hole, it will take forever for objects to actually cross the horizon, but they will smear out and redshift, becoming too faint to see, in some finite time.