= 27d567bc2d48d9f40e9ccc20ea370b15)
CCC comments on Causal Reference - Less Wrong
You are viewing a comment permalink. View the original post to see all comments and the full post content.
= 783df68a0f980790206b9ea87794c5b6)
Loading…= b715d02e85f7b3b4ae65ca3d3e450868)
Subscribe to RSS Feed
Powered by Reddit
= f037147d6e6c911a85753b9abdedda8d)
You are viewing a comment permalink. View the original post to see all comments and the full post content.
Comments (242)
This is where it all gets complicated. If I'm trying to talk about one instantaneous event maintaining an existence for longer than an instant - well, language just isn't structured right for that. An event can partake of many frames of reference, many of which can include me at different times by my watch (particularly if the event in question takes place in the Andromeda Galaxy). So, if there is one reference frame where an Event occurs at the same time as my watch shows 20:00, and another reference frame shows the same (distant) event happening while my watch says 21:00, then does that Event remain in existence for an entire hour?
That's basically the question I'm asking; while I suspect that the answer is 'no', I also don't see what experiment can be used to prove either a positive or a negative answer to that question (and either way, the same experiment seems likely to also prove something else interesting).
I meant it as "are now".
Because if it is now in existence, then I imagine that there is now some way to affect it; which in this case would imply time travel (and therefore at least some form of FTL travel)
First of all, Thou Shalt Not use several frames of reference at once unless you know what you're doing or you risk being badly confused. (Take a look at the Special Relativity section of the Usenet Physics FAQ, especially the discussion of the Twin Paradox.) Possibly, get familiar with spacetime diagrams (also explained in that FAQ).
According to special relativity, the duration of the set of instants B in your life such as there exists an inertial frame of reference such that B is simultaneous with a fixed event A happening in Andromeda is 2L/c, where L is the distance from you to Andromeda. (Now you do need experiments to tell whether special relativity applies to the real world, but any deviation from it --except due to gravitation-- must be very small or only apply to certain circumstances, or we would have seen it by now.)
I'd say that the concept of “now” needs a frame of reference to be specified (or implicit from the context) to make sense.
I think you are trying to apply to Minkowski spacetime an intuition that only applies to Galilean spacetime (and even then, it's not an intuition that everyone shares; IIRC, there have been people thinking that instant action at a distance is counterintuitive and a reason to suspect that Newtonian physics is not the whole story for centuries, even before Einstein came along).
I think that this is important; I have come to suspect that I am somewhat confused.
This is more than likely correct. I would also note that I have been applying, over very long (intergalactic) distances, the assumption that there is no expansion, which is clearly wrong. I suspect that I should probably look more into General Relativity before continuing along this train of thought.
Andromeda is nowhere near so far away that the expansion of the universe is important. (In fact, according to Wikipedia it's being blueshifted, meaning that its gravitational attraction to us is winning over the expansion of space.)