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0 pointsrobotomir15y ago0 comments

From the SETI FAQ: "Detection of broadband signals from Earth such as AM radio, FM radio, and television picture and sound would be extremely difficult even at a fraction of a light-year distant from the Sun. For example, a TV picture having 5 MHz of bandwidth and 5 MWatts of power could not be detected beyond the solar system even with a radio telescope with 100 times the sensitivity of the 305 meter diameter Arecibo telescope."

Now, the Arecibo message should carry over a couple of hundred light years easily, but it was transmitted for three minutes only, and if you miss it, you miss it.

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5 comments · 1 top-level

meric15y ago· 4 in thread

Not if you have faster-than-light travel!

If they don't, it would seem pointless to contact aliens, by the time they send their ambassador on a multi-generational ship to Earth we humans may have already been extinct.

btipling15y ago

FTL is probably not ever possible no matter how technologically advanced a society may be as it would allow for the violation of causality.

ceejayoz15y ago

You're assuming we already know everything there is to know about causality. It wasn't long ago that some people thought the sound barrier was insurmountable, or that trains would kill their occupants by going too fast.

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robryan15y ago

What about the bending of space for an instant travel time? That's more of an unknown in terms of possibility from what I have read.

jasamer15y ago

If I understand GR correctly, FTL travel is (in principle) not necessary to reach an alien race in reasonable time, no matter the distance - from the point of view of an astronaut. Due to length dilation, from the point of view of an astronaut, the whole universe gets pretty small when he travels with almost-lightspeed, so that he can travel, say, one lightyear in five minutes (assuming he can survive the acceleration). The problem is that the wait on earth would be pretty long...

I'm not actually 100% sure my interpretation of GR is correct, if anyone of the people who know more about it could elaborate, I'd greatly appreciated it (for example, I think acceleration has effects on time, too, which could crush my "long distance travel in no time"-theory).

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