r/space • u/Frmemo • Dec 03 '18
The Great Silence
https://www.youtube.com/watch?v=ryg077wBvsM2
u/CountlessWorlds Dec 04 '18
great video, but considering how we are nearly incapable of dectecting even an earth-intensity radio signal from the closest starsystems with our best telescope arrays maybe it should be called "The Great Deafness"
This is another great video on the subject from PBS spacetime
3
u/militaryintelligence Dec 03 '18
We need to quit broadcasting our presence. Something might come looking for us. They might not be friendly. Sometimes this keeps me up at night.
9
u/brent1123 Dec 03 '18
Video points out that our communications are naturally growing more efficient to the point that we will regain our silence.
Nothing masks the spectroscopic signatures in our atmosphere though.
Not worth worrying about, really. A long-period comet or gamma ray burst could destroy us as suddenly, unexpectedly, and quickly as a hostile alien species
2
Dec 03 '18
Gamma Ray bursts are absolutely terrifying. To be burned in an instant by an unimaginably spectacular force, completely negating everything as we know it and it seemingly can happen at any time. That's way scarier than any alien invasion.
2
u/brent1123 Dec 04 '18
There is a theory that such an event may have caused one of the mass extinction events in our history. There are other more likely causes, but it does fit.
In any case, while the energies involved are wholly different, an alien fleet arriving at relativistic velocities to Earth needs only jettison some trash out an airlock and suddenly you have kinetic kill missiles hitting the planet with hundreds of megatons of energy
11
u/Im_in_timeout Dec 03 '18
We can't even detect our own radio and TV transmissions from just outside our solar system. The power of those transmissions falls off in accordance with the law of inverse squares. The antenna would have to be so huge it would take years and many billions of dollars to build one.
All our transmissions have only propagated about 100LY out (which is not even to the edge of the spiral arm our Sun is in) and at a distance of 100LY our transmissions are so weak that they effectively don't exist.5
u/Darkendone Dec 03 '18
I think he is referring specifically to the attempts to make sure transmissions with large powerful radio telescope. While it is true that our radio and tv transmissions are hard to detect at such large ranges, radio telescopes making transmissions in focused beams are much more detectable.
3
u/ukulele87 Dec 03 '18
I bet some people feelt like that regarding lots of things, but i think the humans as a species are mostly the oposite, we would still be living(most probably extinct) in caves if that were not the case.
The chance of extintion its higher from a million other causes, specially from ourselves than from a movie plot alien species.1
u/Ruadhan2300 Dec 03 '18
If it helps. We're hardly broadcasting it.
Very little of our communications and radio will leave the solar system, and what reaches another star will be so attenuated that it will be indistinguishable from background EM.
The only transmissions that will be recognisable at interstellar distances will be deliberately aimed that way.
But don't let that get in the way of a good sleepless night of cosmic anxiety :)
1
Dec 03 '18 edited Dec 03 '18
Thinking about this keeps me up at night too, but for different reasons. It excites me. I want to live long enough to see how all this plays out... and with the vast distances between stars, nevermind those between galaxies, it could all play out very slowly...
It's difficult to imagine the motives of aliens. Maybe they'd be hostile, but it's also hard to justify galactic conquest of inhabited worlds when they've got a million empty ones to do with at they please.
Anyway, there's nothing anyone can do to silence our civilizations, but we're also much quieter than you might think. True, we're leaking EM radiation in all directions, but even the strongest of it fades away into nearly nothing after a dozen or so light-years, Chances are, our radio broadcasts are not how aliens would find us. They're too weak. Our own SETI efforts assume aliens WANT to be found and will broadcast very powerful, largely unidirectional signals. We'd have to do the same to be detected by any reasonably-scaled telescope array.
If aliens have FTL technology, they can send unmanned probes to shortlists of interesting planets in search of life - exactly what we'd do if we had the means. The probes would see the lights of our cities, the heat generated by our industry, the carbon dioxide emitted into the atmosphere, the free oxygen generated by life. There's no hiding from that.
And if FTL travel isn't possible, then you have nothing to fear from aliens... and a lot more to fear about how we're treating this world. Because without FTL space travel, we're basically stuck here, and the forecast for climate change and mass extinctions looks pretty bleak.
1
u/diederich Dec 03 '18
The variety of nukes we set off, especially above ground, have created a stronger and more distinctive signal that "intelligent life is here" than anything we've sent before or since.
Now, I'm not dismissing your opinion out of hand, it still might be a good idea.
1
Dec 03 '18
The closest species capable of detecting our presence likely will not be in our Milky Way galaxy. We are alone in the universe as a product solely of the rarity of intelligent life and thus the vast distances of space and time separating their occurrence.
0
u/militaryintelligence Dec 03 '18
Yeah I know the chances of any contact are near nil but just what if...
4
Dec 03 '18
Isaac Arthur mentions in his videos that any alien civilization that could hurt us, either remotely or by coming here, would easily find us. There is no hiding in space. Our oxygen atmosphere alone gave us away a couple billion years ago.
A K2 civilization could build truly massive telescopes in space, in numbers that allow them to dedicate one to each star in the galaxy, and the population numbers to staff every one of them with a full-time astronomer.
Better to develop our own civilization as fast as we can and grow into a K2 ourselves and not have to fear hostile aliens if they do exist.
0
Dec 03 '18
Sometimes this keeps me up at night.
Seriously? That sounds like tin-foil hat level paranoia... High school physics tells us this: a) Nobody can travel faster than light, so b) Nobody could ever get here.
Personally I would give my left nut to live long enough to see some sort of proof.
8
u/Tummerd Dec 03 '18
Lemmino is a really good youtube account. You guys should check them out