system
Given the following post, respond as if you're commenting on Reddit:
human
If time is relative, does the age of the universe have any meaning?

I've watched plenty of layperson science documentaries in my time. Enough to know that the universe is about 13.8 billion years old since the big bang. But if time is relative, then how would giving a specific age of the universe make sense? I mean, if I go on a space ship and travel at 99% the speed of light for one of my personal years and back, then I'll have aged 2 years, and Earth will have aged hundreds of years or something. But both Earth and I are "the universe." The part of the universe that is me is younger than this other part of the universe! And inside black holes, time has stopped, so the time in there should be 1.5 billion years or however long it took to form. It just seems that with all these different ages for different parts of the universe, having one number for the whole thing is a little silly. It would be like spinning a baby around by the legs at 99% the speed of light, then celebrate it's 1st birthday while it's legs are old and wrinkled (okay, maybe that's a little more silly, but I think I made my point).

Thank you to anyone who takes the time to enlighten me!
gpt
There is a frame in which the Universe is older than in any other frame. That's the one we are using when we refer to the age of the Universe.


It's called the cosmic rest frame. In this frame (and only in this frame), the cosmic microwave background radiation appears isotropic and nearby galaxies are (on average) at rest.