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Comment Re: It *can* be right... (Score 1) 126

Darling, the fate of the astronaut in either case has nothing to do with it. The alpha centauri one is going to die before you get there, truly. But you cannot say he is "dead already" from your own reference frame. Well, you can on a /. thread obviously, but it's a philosophical point, not a scientific one.

You can make the trip to the doomed astronaut, and you can watch him die through your telescope before you get there (however the hell that might look when you're moving at relativistic speeds) but there is absolutely no way for you to *prove* that he has already expired before you left, because there is no mechanism to check the fact.

"Oh well, but doesn't it just make sense anyway? I mean, he only had food for 4 years, and it took more than that for his message to reach us." Yes, I get what you're trying to say, but it's a philosophical point only, which is another way of saying it's no bloody point at all.

Comment Re:It *can* be right... (Score 1) 126

Damn, you're dumb. I really lost it at "we can't say that they died X light-years ago". No, we certainly can't say that.

Damn, you're a nice guy and I like you. Yes, I knew I'd be caught on the "light-years ago" point. I thought the years/light-years phrasing I used later would be back-ported by yourself and the intention correctly inferred. Lesson learned. I'll be explicit next time. I also made a mistake at the start of the 3rd paragraph: Replace *say* with *hypothesise* to get the gist of my meaning.

Anyway, adding a radio into the mix is pure fluff, and so is the notion of precision. Neither say anything about when it is meaningful to say "Z happened" according to any particular reference frame.

Comment Re:It *can* be right... (Score 1) 126

There isn't nearly enough data to answer the question, and whatever data I can dream-up to fill the gaps doesn't solve the problem either.

We can sit here and watch the astronaut die from afar, but we can't say that they died X light-years ago because the information of the event is propagating at that speed too. To send a rescue craft to reach them just before they perish and then return at light-speed, such events would happen (from our frame-of-reference) over the same duration it would have taken to just watch and do nothing (well, slightly less of course, because they were rescued. :)

I grant that you can *say* that the event happened Y years/light-years ago. It's good fun, we have a few laughs, and no /. article with "light years" in it is complete without several of us doing so. But when it comes to actual spacetime, and the real job of looking at it, moving around it, and proving the whole damned conjecture in an empirical way from *any* frame of reference; well, we can't bloody do it, and as far as the best science can tell us so far, nobody else can either, which makes the statement utterly vacuous.

But fun, I guess, and it obviously never gets old.

Comment It *can* be right... (Score 1) 126

There's no provable or usable mechanism by which we can travel to any part of the Universe faster than the speed of light, so trying to make a distinction between the "light of an event reaching us" vs. "the event being observed as it happens" is semantically meaningless.

Information can't travel faster than light, and you can't currently get anywhere fast enough to prove otherwise.

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