Why Aren't The Aliens Here Already?

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Mork from Ork
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Why Aren't The Aliens Here Already?

Postby Mork from Ork » Wed May 27, 2015 8:50 pm

Interesting article from NPR about if the galaxy is teaming with intelligent life then why are they not here yet, or everywhere. Learned the name of a paradox: Fermi's paradox. Just love paradoxes. :D

Why Aren't The Aliens Here Already?

The story begins like this: In 1950, a group of high-powered physicists were lunching together near the Los Alamos National Laboratory.

Among those in attendance were Edward Teller (father of the nuclear bomb) and the Nobel Prize-winning Enrico Fermi. The discussion turned to a spate of recent UFO sightings and, then, on to the possibility of seeing an object (made by aliens) move faster than light. The conversation eventually turned to other topics when, out the blue, Fermi suddenly asked: "Where is everybody?"

While he'd startled his colleagues, they all quickly understood what he was referring to: Where are all the aliens?

What Fermi realized in his burst of insight was simple: If the universe was teeming with intelligent technological civilizations, why hadn't they already made it to Earth? Indeed, why hadn't they made it everywhere?

This question, known as "Fermi's paradox," is now a staple of astrobiological/SETI thinking. And while it might seem pretty abstract and inconsequential to our day-to-day existence, within Fermi's paradox there lies a terrible possibility that haunts the fate of humanity.

Enough issues are packed into Fermi's paradox for more than one post and — since Caleb Scharf and I are just starting a research project related to the question — I am sure to return to it. Today, however, I just want to unpack the basics of Fermi's paradox and its consequences.

The most important thing to understand about Fermi's paradox is that you don't need faster-than-light travel, a warp drive or other exotic technology to take it seriously. Even if a technological civilization built ships that reached only a fraction of the speed of light, we might still expect all the stars (and the planets) to be "colonized."

For example, let's imagine that just one high-tech alien species emerges and starts sending ships out at one-hundredth of the speed of light. With that technology, they'd cross the typical distance between stars in "just" a few centuries to a millennium. If, once they got to a new solar system, they began using its resources to build more ships, then we can imagine how a wave of colonization begins propagating across the galaxy.

But how long does it take this colonization wave to spread?

Remarkably, it would only take a fraction of our galaxy's lifetime before all the stars are inhabited. Depending on what you assume, the propagating wave of colonization could make it from one end of our Milky Way to the other in just 10 million years. While that might seem very long to you, it's really just a blink of the eye to the 10-billion-year-old Milky Way (in other words, the colonization wave crosses in 0.001 times the age of the galaxy). That means if an alien civilization began at some random moment in the Milky Way's history, odds are it has had time to colonize the entire galaxy.

You can choose your favorite sci-fi trope for what's going on with these alien "slow ships." Maybe they use cryogenic suspension. Maybe they're using generation ships — mobile worlds whose inhabitants live out entire lives during the millennia-long crossing. Maybe the aliens don't go themselves but send fully autonomous machines. Whatever scenario you choose, simple calculations, like the one above, tend to imply the aliens should be here already.

Of course, you can also come up with lots of resolutions to Fermi's paradox. Maybe the aliens don't want to colonize other worlds. Maybe none of the technologies for the ships described above really work. Maybe, maybe, maybe. We can take up some of those solutions in later 13.7 posts.

For today, however, let's just consider the one answer that really matters for us, the existential one that is very, very freaky indeed: The aliens aren't here because they don't exist. We are the only sentient, technological species that exists in the entire galaxy.

It's hard to overstate how profound this conclusion would be.

The consequences cut both ways. On the one hand, it's possible that no other species has ever reached our state of development. Our galaxy with its 300 billion stars — meaning 300 billion chances for self-consciousness — has never awakened anywhere else. We would be the only ones looking into the night sky and asking questions. How impossibly lonely that would be.

On the other hand, it's also possible that other species have made it to where we stand today. But no one has made it much farther. Say that like a "great filter," something like war or environmental collapse keeps anyone, anywhere, from reaching beyond our stage of technological development. If that's true then we, like all who have come before us, are doomed.

So what is it? What is the answer? What is it that Fermi's paradox is trying to tell us? After all is said and done, where is everyone?

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Re: Why Aren't The Aliens Here Already?

Postby Teleros » Mon Jun 01, 2015 10:33 pm

Mork from Ork wrote:So what is it? What is the answer? What is it that Fermi's paradox is trying to tell us? After all is said and done, where is everyone?

Here are a few thoughts:

First, we don't really know how often human-level (let alone superior) intelligence crops up in evolution. As far as we know, intelligent life in the entire solar system has appeared precisely once: in humans, on one of nine planets, in a solar system that's around 5-6 billion years old. Given how many other species have existed in Earth's history, high intelligence is probably a very rare trait to emerge in general.

Second, we know that even then, we had a bumpy ride to get to where we are now. Biologists reckon that a few tens of thousands / hundreds of thousands of years ago the entire human race was nearly wiped out due to a disease. And let's not forget the Black Death, the germs that Europeans brought to the Americas, et cetera.

Third, you then have to consider the environments suitable for intelligent life, at least in terms of solar systems, planets and such. Granted, I'm sure that life can exist on non-Earth-like worlds, but for now let's just consider them. You need your alien homeworld to be orbiting in the "Goldilocks Zone" of its star (ie neither too hot nor too cold), to be reasonably well protected from asteroids and the like (thanks Jupiter & Luna!), and probably to have certain other environmental conditions as well (not too much oxygen, gravity within a certain range - especially for building rockets to get into space with), etc. We can probably discount random natural disasters like supernovae though - they happen, but you'd have to be very unlucky to be hit by one :) .

Fourth, you have culture to consider. The UN reckons that more books are translated into Spanish each year than have been translated into Arabic in the last thousand years. Whilst Europeans were harnessing the power of steam and electricity... nobody else was, to put it nicely. Heck, Australian Aborigines were still living with Stone Age technology when Britain was shipping its convicts out there. In other words, it's quite possible to consider intelligent species simply not pursuing technological advancement at the same rate that humanity has. On a related topic, how will alien species choose to expand? There's enough resources in the solar system for quadrillions of humans to live off happily, and if an alien species prefers to stay at home than to explore the great unknown, they are likely to be a very small space-faring civilisation in terms of volume (in 4X terms, think "tall" rather than "wide" empire-building).

Fifth, space is big. Like, seriously big. Unless you're pointing a giant radio transmitter at another solar system, your broadcasts really won't get very far in galactic terms at all, because the signal will weaken as it spreads out, until it's lost amongst all the background noise. Of course, building a monster-sized radio transmitter to say "hi" is expensive, potentially risky, and probably quite limited in that you won't be able to broadcast to the entire galaxy at once (to say nothing about how long you'd need to broadcast for, if it takes light 100,000+ years to cross the galaxy).
Clear ether!

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Re: Why Aren't The Aliens Here Already?

Postby SilasOfBorg » Mon Jun 08, 2015 5:57 pm

I have to admit I'm an advocate of the more depressing explanation; that is, as the technological advancement of any given species approaches the technological level necessary for interstellar travel and colonization, the probability that said technology will in fact be used to destroy itself approaches 100%.

Examples abound. Computers and AI are powerful tools, but it remains to be seen if the singularity will end us. Atomic power gave us atomic bombs, of which there are still enough in the world to end us many times over. Industrialization gave us greenhouse gases, which if left unchecked may not end us but could very conceivably kick us back into the stone age, and we'll have to start all over again. Nanotechnology can in theory be weaponized into nanoplagues. Plastics gave us fertility-reducing xenoestrogens and PCBs. Etc etc ad infinitum.

In any case, Drake's equation has a lot of factors that, due to anthropic bias and lack of samples, means we can "reasonably" have various f-values anywhere from near-zero to one, making the result more a personal / religious / idealistic choice than one with any scientific backing.

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Re: Why Aren't The Aliens Here Already?

Postby BrainShock » Sun Aug 02, 2015 3:24 am

Who is to say that Earth isn't being visited right now?

To me this is not the question I want answered. Much bigger questions. IMHO.

I never hear much about evolution forward. Like when do we stop being human and become something else?

Telepathic powers emergence. I seen a few SCI-Fi were a few get it and others hunt them down and kill em. I never seen a SCI-FI were everyone gets it at once and therefore the species moves on. I guess that's unworkable. Under evolution theory it would be a mutant gene that gives some telepathic powers and they kill the rest or have a huge advantage being able to spread there tele-seed. Which would take a extreme long time to spread.
If we evolved from monkeys? Then when do we stop being human and become something else?

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Re: Why Aren't The Aliens Here Already?

Postby amyburgess » Mon Aug 28, 2017 12:08 pm

I read your post in one go very fond of science fiction. And I wonder if there are reasonable races besides us
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