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If the universe has only a single particle, is time even possible? I think a universe with one particle is the same as one with none. As soon as you have two p

If the universe has only a single particle, is time even possible? I think a universe with one particle is the same as one with none. As soon as you have two particles they can move toward each other, and spin can be observed.

akira2501 2y ago
> If the universe has only a single particle, is time even possible? space is constantly expanding. particles have energy. energy decays. eventually into photos. colors shift red due to increasing wavelength and decreasing energy.
- datavirtue 2y ago
  We don't know if space is expanding. The models and observations appear to support expansion. This was just a thought experiment with a theoretical single partical in a universe of unknown size to demonstrate that the universe changes in non-obvious ways as you add energy/matter.
dingaling 2y ago
I'd say yes to time with one particle, as its position within the universe, or the universe's size in relation to the particle, can change.
- ndsipa_pomu 2y ago
  If a universe only contains a single particle, then there can be no "position" within the universe as how could you possibly measure it? Similarly, how would you be able to determine if it was static or moving without comparing it to something else?
slightwinder 2y ago
Wouldn't a single particle still change, move, experience time? There is just no way to measure time.
- datavirtue 2y ago
  There is no way to tell if it is moving.
  - fatata123 2y ago
    [dead]
  - slightwinder 2y ago
    Yes, but that is irrelevant. Change happens, even if you can't recognize it. Recognizing change is a shortterm-problem. But longterm it can be relevant, if the particle some day will break down, disappear, burn out, or whatever happens to them.
excalibur 2y ago
I think that's gonna depend heavily on your definition of particle. It seems most likely that our current universe is a singularity, a single point that contains the entirety of space and time, such as they are. Viewed through a certain lens this could be considered a particle, but I'm not sure that it checks all the boxes for properties you associate with one.

akira2501 2y ago

> If the universe has only a single particle, is time even possible? space is constantly expanding. particles have energy. energy decays. eventually into photos. colors shift red due to increasing wavelength and decreasing energy.

datavirtue 2y ago
We don't know if space is expanding. The models and observations appear to support expansion. This was just a thought experiment with a theoretical single partical in a universe of unknown size to demonstrate that the universe changes in non-obvious ways as you add energy/matter.

dingaling 2y ago

I'd say yes to time with one particle, as its position within the universe, or the universe's size in relation to the particle, can change.

ndsipa_pomu 2y ago
If a universe only contains a single particle, then there can be no "position" within the universe as how could you possibly measure it? Similarly, how would you be able to determine if it was static or moving without comparing it to something else?

slightwinder 2y ago

Wouldn't a single particle still change, move, experience time? There is just no way to measure time.

datavirtue 2y ago
There is no way to tell if it is moving.
- fatata123 2y ago
  [dead]
- slightwinder 2y ago
  Yes, but that is irrelevant. Change happens, even if you can't recognize it. Recognizing change is a shortterm-problem. But longterm it can be relevant, if the particle some day will break down, disappear, burn out, or whatever happens to them.

excalibur 2y ago

I think that's gonna depend heavily on your definition of particle. It seems most likely that our current universe is a singularity, a single point that contains the entirety of space and time, such as they are. Viewed through a certain lens this could be considered a particle, but I'm not sure that it checks all the boxes for properties you associate with one.