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.
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.
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.
space is constantly expanding. particles have energy. energy decays. eventually into photos. colors shift red due to increasing wavelength and decreasing energy.
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.