Send Radio Signals to Other Stars: Accounting for Arrival

[kindaroomy]

If I wanted to send a radio signal to another star, shouldn’t I have to account for where the star will be when the message arrives?

 

[russ_watters]

If I wanted to send a radio signal to another star, shouldn’t I have to account for where the star will be when the message arrives?

If you send it with a parabolic dish, yes, but if you send it in a way that is not as directional (just an antenna, for example) no.

 

[FawkesCa]

just a quck folow up question russ, wouldn't the parabolic dish still not make much of a difference? i mean, the radio waves should still spead out enough thoughout space right? unless one was trying to reach Mars. but Alpha-Centari should just be "There it is. Point and shoot!" right"

 

[russ_watters]

Yes, the stars we can see with the naked eye don't move much and it is difficult to get a very tight beam of radio waves. Heck, Mars doesn't even move much in the few minutes it takes for a signal to reach it.

 

[kindaroomy]

I was reading up on the first organized message sent into space, the Arecibo Message. It was sent to Messier 13 some 26,000 ly away. I am guessing under this scenario you'd have to account for movement, as the stars can orbit around the galaxy quite a bit in 26,000 years. Or would this message still be broad enough to cover it?

 

[sbrothy]

"... the stars of M13 that the message was aimed at will no longer be in that location when the message arrives."

---- http://en.wikipedia.org/wiki/Arecibo_message