Re: FTL transmission?

From: Brian Atkins (
Date: Fri Jun 02 2000 - 10:03:01 MDT

John Clark wrote:
> Brian Atkins <> Wrote:
> > So what if someone sees me react to something that for them hasn't
> > even been transmitted yet?
> If you had a FTL modem you could also receive a message from yourself
> before you sent it, that's exactly why physicists get queasy when they talk
> about faster than light signaling. Example: You just knocked over your coffee
> cup by accident. Rather than clean it up you sent yourself an E Mail to the you
> of 60 seconds ago, you tell yourself that the cup is dangerously near your elbow
> and to be careful or you'll break it. You take the advice and put the cup in a
> safe place, it does not get knocked over. So who sent the message, and why did
> he sent it when there is nothing to warn about?

Right, I get that. What I still don't get is how being able to send
something FTL allows me to send info back in time. Intuitively for me,
it seems that sending something very fast (or instantly) could not allow
me to send info back in time. I definitely could send info to someone
else who hasn't seen the photons yet telling them to "hey look here and
watch my coffee spill", but that is not a paradox. But I don't see how
I can send myself a message in the past once the coffee has already spilled
and I've seen it.

All these paradoxes seem to be based on relativistic formulas (Einstein)...
but do these formulas make sense in FTL situations?

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