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Ok. I’m a novice in this. But isn’t time relative, and also affected by gravity and velocities? When we talk about the age of the universe, from which perspecti
by surfsvammel 3y ago
Ok. I’m a novice in this. But isn’t time relative, and also affected by gravity and velocities? When we talk about the age of the universe, from which perspective are we considering it?
- flumpcakes 3y agoFrom my poor understanding of a Physics degree: the "age" is just counted from when everything existed in the same space, before it's rapid expansion. Although, can you say it expanded? It didn't expand into anything because space does not exist outside of the universe. Or do we say it 'expanded' because the distance between the constituent parts inside of the universe grew? It's not good to think about really.
- lgas 3y agoIt's the second one. The individual parts moved away from each other. And there's nothing "not good" about thinking about it.
- superposeur 3y agoIndeed time is relative. But, the observed distribution of matter in the universe turns out to single out one particular frame of reference (= large scale spacetime coordinate system). Namely the one in which the CMB radiation is isotropic (same in all directions, neither red shifted nor blue shifted). It is with respect to this particular reference frame that the “age of the universe” is defined.