Interstellar communication: Possible?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Dinosaur, Jul 10, 2017.

1. DinosaurRational SkepticValued Senior Member

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I & others have Posted remarks similar to the following. It would be interesting to me & probably to others to get current opinions on feasibility.

Suppose there is a technological culture similar to ours on a planet orbiting Proxima Centauri, which is circa 4.3 light years from us.

Could we communicate with it? Could we detect their communications?

Our orbital speed is circa 30 Kilometers per second (or 18.5 miles per second). 108,000 km per hour (67,000 Miles per hour). A planet with technology orbiting Proxima Centauri is likely to have a similar orbital speed.

Note that over a distance of 4.3 light years, a signal like our radio or TV technology diminishes via an inverse square law. Such signals would not be detectable at that distance.

BTW: Our technology is tending toward FIOS or the current Comcast communications. There will likely be a time in the not too distant future when none of our ordinary broadcast signals could be picked up by equipment on Luna.

Ordinary broadcast signals from a technological culture orbiting a star light years distant are likely to become (or already be) similarly undetectable at the Earth to Luna distance. ​

It seems to me that directed signals (Google Aricebo) would have to be extremely precisely aimed to be detected by receivers circa 4.3 light years from the transmitters. Considering the orbital motions, this seems like a difficult task.

3. mathmanValued Senior Member

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There is a difference between highly unlikely and impossible.

5. DaveC426913Valued Senior Member

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True.

In which category do you put this?

7. spidergoatValued Senior Member

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Seems like an achievable engineering problem. The bad part would be the delay between sending and receiving a message.

8. originTrump is the best argument against a democracy.Valued Senior Member

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Sure, but we would use a focussed beam so the signal would not drop off at 1/x^2.

9. originTrump is the best argument against a democracy.Valued Senior Member

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It would be easy. We know the proper motion of alpha centauri and the signal would spread out quite a bit.

10. timojinValued Senior Member

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So would the signal be Meaningful ?

11. DaveC426913Valued Senior Member

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Certainly.
Even if it contained no decipherable content, it would certainly be very informative to anyone who received it. It would have the single most important message of all:

12. KittamaruNever cruel nor cowardly...Staff Member

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Ultimately, it might be better to have a "relatively" stationary satellite somewhere towards the edge of either galaxy solar system act as an amplifier of sorts. Point an extremely narrow-band signal at the satellite, and have it re-broadcast a wider band out towards the planet in question - would mitigate dropoff over extreme distance, and maximize the chances of the signal reaching the receiving end..

EDIT - corrected item of scale (galaxy to solar system) - I need more bloody sleep!

Last edited: Jul 11, 2017
13. timojinValued Senior Member

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If it have taken years for a satellite to reach the outer part os our solar system , how long would it take to reach the edge of our galaxy ?

14. KittamaruNever cruel nor cowardly...Staff Member

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I would think it is obvious that the supposition requires far greater technology than we currently have available?

15. gmilamValued Senior Member

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I think Kitt meant solar system.

While interstellar communication may be possible - even if not practical, I think intergalactic communication would be totally unfeasible.

16. KittamaruNever cruel nor cowardly...Staff Member

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Ah, my apologies - good catch gmilam - I am on the totally wrong scale! This is what having 6 hours of sleep over 3 days does to me 0o;

17. James RJust this guy, you know?Staff Member

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Voyager 1 is currently about 20.8 billion kilometres from the Sun. It was launched in 1977, so it has been travelling for about 40 years, which puts its speed at about 17 kilometres per second.

The Milky Way has a diametre of about 100,000 light years, or about $9.5\times 10^{17}$ km.

So, if Voyager 1 travelled at its current speed, on average, it would take about 1.8 billion years to cross the galaxy.

Last edited: Jul 14, 2017
18. The GodValued Senior Member

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Our solar system is around 26000 light years away from centre, and assuming that Voyager 1 is moving away towards the edge of the Galaxy, then it needs to cover 24000 light years only to cross the edge, thus the time required would be only around 450 billion years (roughly 1800/4).

19. timojinValued Senior Member

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Those are fantastic number . I get to appreciate mother earth more and more , and the space does not become to realistic.

20. James RJust this guy, you know?Staff Member

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Correction: I made a slight error there and was out by a factor of 1000 (I used metres where I should have used kilometers). The trip across the galaxy for Voyager 1 would only (!) take 1.8 billion years, not 1.8 trillion years.

(I have edited my original post above.)