3 ms·
Related question: At universe-scale, does it makes sense to talk about a general "now"? I thought that, when large enough distances are involved, "now" becomes
by maest 6y ago
Related question:
At universe-scale, does it makes sense to talk about a general "now"? I thought that, when large enough distances are involved, "now" becomes a local concept.
- contravariant 6y agoIt gets more complicated but it still makes sense. The concept is called a Cauchy surface. The tricky bit is that it isn't uniquely defined, but even for an expanding universe it can be defined globally (I think).