Astrophysicist Believes Technologically-Advanced Species Extinguish Themselves (sciencedaily.com)

Why haven't we heard from intelligent life elsewhere in the universe? wisebabo writes: In the Science Daily article "Where is everybody? The Implications of Cosmic Silence," the retired astrophysicist Daniel Whitmire explains that using the principle of mediocracy (a statistical notion that says, in the absence of more data, that your one data point is likely to be "average"), that not only are we the first intelligent life on earth but that we will likely be the only (and thus the last) intelligent life on this planet... Unfortunately that isn't the worst of it.

Coupled with the "Great Silence", it implies that the reason we haven't heard from anyone is that intelligent life, when it happens anywhere else in the universe, doesn't last and when it does it flames out quickly and takes the biosphere with it (preventing any other intelligent life from reappearing. Sorry dolphins!). While this is depressing in a very deep sense both cosmically (no Star Trek/Wars/Valerian universes filled with alien civilizations) and locally (we're going to wipe ourselves out, and soon) it is perhaps understandable given our current progress towards reproducing the conditions of the greatest extinction event in earth's history.
That last link (reprinting a New York Times opinion piece) cites the "Great Dying" of 90% of all land-based life in 252 million B.C., which is believed to have been triggered by "gigantic emissions of carbon dioxide from volcanoes that erupted across a vast swath of Siberia." But if we're not headed to the same inexorable doom, that raises an inevitable follow-up question.

If intelligence-driven extinction doesn't explain this great cosmic silence, then what does? Why hasn't our species heard from other intelligent civilizations elsewhere in the universe?

Comments

time and distance scaling

[cats-paw]

As has already been demonstrated by the permian extinction event, the biosphere can take a hell of a hit, and life will go on.

I think that you really have to understand timescales here. A 100 million years is a long time, just like space is big, really big. So that's a long damn time, and life will go on. intelligent life, maybe not so much.

as for why we haven't heard from anyone, why isn't the simple answer not the best ?
Remember how space is really big ?

if there's no FTL travel, and it's likely there is not, then HOW would we hear from someone ?

It would be an exceedingly difficult thing for the intelligent civilization in the Andromeda galaxy to talk us, and us to them.

First of all, there's the 2,000,000 year latency, and then the amount of power you would need to transmit that signal, etc...

I'm not worried. There's intelligent life elsewhere in the verse. I'm pretty sure we're not going to hear from them any time soon, if ever.

Re:time and distance scaling

[JoshuaZ]

The problem though isn't deliberate communication, but rather twofold:

First, a complete lack of evidence on a large scale of anything we'd expect to see. We have some pretty concrete ideas about construction of megastructures, such as Dyson spheres, the more plausible Dyson swarms, stellar engines (where the Class A version https://en.wikipedia.org/wiki/Stellar_engine#Class_A_.28Shkadov_thruster.29 is essentially doable if one has enough material and doesn't require any exotically strong materials or the like), and many more. But we don't see any signs of any of those. And most of those will *last* for very long times once constructed. And we have searched for them both here http://home.fnal.gov/~carrigan/infrared_astronomy/Fermilab_search.htm and in other galaxies. In a similar context, we've looked for signs of K3 civilizations in about 100,000 galaxies and found essentially no signs of them https://arxiv.org/abs/1504.03418.

The second problem is that if a species does survive even a relatively small amount of time, it should be able to spread throughout a galaxy. Yes, galaxies are really big, but the space is not as big as the time available. For example the Milky Way is about 100,000 light years across. That means that if a species starts on one end and travels spreading throughout planets at around 1% of light speed (which certainly looks doable) then it takes around a 10 million years for them to spread throughout. That's a tiny amount of time. But we don't see any signs of anything like that.

So there really does seem to be some sort of Great Filter or series of Filters, and the question is whether it is early (e.g. life is hard to arise or intelligence arises rarely) or late (civilizations wipe themselves out). And if it is the second, then we need to figure out what is going on since we don't get a do-over.

Re:time and distance scaling

[Tablizer]

Not necessarily. It's a matter of economics. Sometimes it's cheaper to waste energy than spend resources on efficiency. If fuel is relatively cheap, then efficiency may not be worth the added cost.

Re:time and distance scaling

[slack_justyb]

if there's no FTL travel, and it's likely there is not, then HOW would we hear from someone ?

You say that, but that totally invalidates what you said prior to that.

A 100 million years is a long time

The Andromeda galaxy is only 780 kpc from us. At 99% the speed of light, that's only 2.5 million years. On a scale of 100 million years, that's totally doable multiple times over. That's the huge mystery of the Fermi paradox. Given medium time scales like G-type main sequence stars lifetimes, alien life has had enough time to hop between the big three galaxies in our local group and do a fly-by of the main stars in all three as well.

if there's no FTL travel, and it's likely there is not

Yeah, it's insanely likely that FTL is just sci-fi forever. I personally think anything higher than 90% c is just non-doable. So look back at the last paragraph in my comment. Say we slow everyone down to just 10% c. At 10% c, you can hop from one side of the Milky Way to the other in just a million years. Get to Andromeda in just 25 million years. That's still really short time spans. You could fly to Andromeda, send a message back and the sun still wouldn't have entered it's next phase, one billion years from now compared to 27 million years for what I just described.

First of all, there's the 2,000,000 year latency, and then the amount of power you would need to transmit that signal, etc...

All of those are insanely small scale issues, they're big things to us because we lack the ability to even fly to another planet, but if you're the type of society that can fly at 10% c, those are pretty simple tasks that might take 10k years to build a generator, 15k years to build the transmitter, etc. They just seems like big deals because we're nowhere near that kind of specie.

So millions of years is not a huge amount of time. But more importantly, becoming a traveler of the stars means you don't hold on to where you came from. You travel to Andromeda, that's who you are now. You don't have strong ties to Earth anymore, you're a seed of life, not an explorer. Humanity still clings to this notion that once we start, if we start, traveling the stars that we'll for some reason still treat Earth as this special place that we need to come back to or at the very least report back to. We might send a message, but after that, those humans are now their own thing. The idea of sending people to other planets isn't to save Earth, it isn't even to save our species because more than likely after a few thousand years on a different planet your DNA is going to change vastly. It's to save intellect, to keep the thinking/feeling part of the Universe going. As far as we know we're the first/only part of the universe that's got the thinking attribute and maybe just like how supernovae spread heavier elements, we need to get our butts in gear to start spreading this attribute across the galaxies (just the local group, the idea that we'll ever make it out of the local group is not even real with any kind of advancement). But that's just my take.

Do you still use AOL Instant Messenger?

[BLToday]

We're using AIM and we assume if people have internet connection then they must also use AIM. If we see no one on AIM then there must be no one else with an internet connection.

I'm with the theory that we're just at the beginning of life in this part of the universe. 13.7 billion years from the Big Bang. Multiple generations of star formation and death before getting to our Sun. Then another 4 billion years before complex life. Sounds like it takes awhile for intelligent life to get started.