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Where are they? The aliens, I mean.

The Fermi Paradox

I've always been fascinated by the Fermi paradox.

One day in the 1940's Dr. Enrico Fermi asked his fellow physicists, "Where the hell are all the aliens?"

Sounds kind of weird doesn't it?

But, at that point in time we had just invented rockets, computers, and shown that you could make self-replicating systems.  So it's pretty obvious what we are going to do.

We are going to keep sending these robots out into space and as soon as they can do repairs, we're going to let them replicate and fill up the galaxy. (Yes, we're an exploitative bunch.)  And we will follow along shortly.

So why hasn't this happened?  Why don't we see other civilizations?  The galaxy has been around almost 15 billion years, the earth has been around only about 5 billion years.  Obviously if life can arise anywhere else but the earth, it should be already out there.  And why should we be special?  Of course life is out there.  If it's out there it's been around a long time.  If it's been around a long time it's got robots and/or colonies everywhere it wants to. So why don't we see them?

There are lots of solutions.  In fact, I've collected a bunch of speculations on this issue.  From "If the Universe Is Teeming with Aliens ... WHERE IS EVERYBODY?: Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life" to SETI (Search for Extraterrestrial Intelligence) papers to Princeton astrophysicists J. R. Gott III's fascinating paper that let's you predict the time frames of anything (with little or no data.)

Some people think we're the first intelligent life in this galaxy.  Hogwash. I give that a zero percent chance.  Or that intelligent species go through a winnowing out at certain points of technology discovery (nuclear weapons, biological weapons, grey goo...) Hogwash again.  However, it's certainly possible that many civilizations are decimated by meteors if they don't invent rockets and telescopes. (Decimated like the dinosaurs were -- if you don't want to be like the dinosaurs then donate to b612 who have pledged to stop this.) This could have easily been our fate if we weren't lucky.  Maybe having Saturn out there sweeping space clean of asteroids has helped us a bit.  But surely there are other solar systems like ours that are billions of years older.  So what gives?

The solution to the Fermi Paradox

What gives is that the galaxy is really, really, really, really big. And I just don't mean big, I mean R-E-A-L-L-Y   B-I-G.  How big is it?  It's more than 100,000 light years across.  Sounds big.  But how big is a light year really?  Really, really big.  Light travels really, really fast.  Faster than anything else in the universe (as far as we know.)  That's the law.  A physical law based on Einstein's theory of special and general relativity which said that the speed of electromagnetic waves (light) is a constant (we physicists designate the speed of light by 'c' because that it is the initial letter of celeritas, the Latin word meaning speed...)  The speed of light is 300,000 kilometers per second or 180,000 miles per second.  So light gets to the moon in about two seconds. The fastest rocket (New Horizons that just went past pluto, by the way) took 3 hours (about 10,000 seconds) or so to get to the moon from the earth.  So light is 5000 times faster than the fastest rocket we've ever made.  That's really fast. The coolest way to remember the speed of light is to remember that it travels a foot in a nano-second (one billionth of a second.)  That makes it physical.

So how many feet are in a years worth of nano-seconds?  Light travels a billion feet in a second and there are about 31 million seconds in a year.  So a light year is 31 million billion feet. That's about 6,000 billion miles. The nearest star, Proxima Centauri, is 4.24 light years away.  Or 26,00 billion miles. The fastest rocket we've ever made takes over 20 centuries to get there.  More than 2,000 years.  Is it any wonder the aliens aren't here yet?

Now of course, those aliens probably have faster ships than us.  But how much faster?  It takes a lot of energy to get going faster, and it takes just as much energy to slow down.  Energy that can be used to do a lot of useful things.  It turns out that the fastest way to settle the galaxy is going to be to send out robots, then send out the genetic code of humans (or aliens) and grow them there.  That way you can bypass all that weary travel that will be so boring to everyone.  And pretty much the only way these settlements are going to be able to talk to each other is by radio or laser.  The actual physical travel between the stars just isn't that useful.  What would you trade between solar systems? Everything is way, way, way cheaper locally. The only thing you would trade would be information, which would travel at the speed of light.  Think about it. We want to put some things on Mars (like people), but nobody wants to pay to bring them back.  This goes double (uh, 26,000 billion over 300 million or 8000) times as much for the nearest star.  It would be stupid to move anything between the stars that you didn't have to. And I'm pretty sure aliens are anything but stupid.

In fact, there is no reason to travel to another star... except to annihilate any life living around that star.  In other words to have a war, or as scientists like to say: evolution in action. And you wouldn't bother to send living things, killer robots can take care of it.  Even Stephen Hawkings know this to be true. Although he's kind of late to the game since we've already broadcasted our presence to every alien out there... well, not quite.  We've only been broadcasting electromagnetic signals for 60 years or so.  This has consequences, which I'll talk about in a minute.  But first...

There is no paradox, we've just been lucky... so far

If you think about this, it's obvious why we don't see any aliens out there.  Some other alien race saw them first and took care of them, either slavery, assimilation, reservationed or annihilated.  And the alien race that was first is very careful to keep very quiet and watch everywhere so that it doesn't risk having the same thing done to it.  (Thank GOD the galaxies are even further apart, that means we don't really have to worry about intergalactic war any time soon.)  But why haven't the aliens already been here and taken care of us?

Like I said, it's a really, really big universe.  They just aren't here yet.  It's obvious that they've got robots watching us, that'd be relatively cheap, but they wouldn't want to create a possible rival race, so these robots aren't going to do anything on their own (like turn on their masters.)  So, the alien robots are waiting, probably out by the Oort cloud. They've sent signals home and are waiting for orders.  So the orders from the aliens would only be here if they were closer than 30 light years.

There are only 133 stars that are within 50 light years of the earth.  There's probably a very small chance that one of these is settled by the master alien race that can decide to annihilate the earth; and then again, why would the aliens bother?  We aren't going to be a threat to an alien planet for a long, long time. There's no hurry.  Do you think aliens are afraid of our puny nuclear bombs?  How does a nuclear bomb compare to the sun?  The sun puts out the equivalent of a trillion nuclear bombs every second. I don't think a race that has been sentient for millions (if not billions) of years is very concerned that we might harm it somehow.  It's also obvious it could hide as well as it wants to (look at how far our primitive cloaking technology has already come.)

However, this progenitor alien race does need to act at some time to protect itself.  Now when would that most likely be?  It's going to be at least as fast as light can travel back and forth across the galaxy, which we know is <200,000 years, just because no matter where they are hiding, the signal that says 'humans are now a threat' is going to reach them by then and they can respond.

In fact, we can write an equation that, given the density (number) of alien settlements in the galaxy, will predict how soon the aliens will be able to respond to us.

First we assume that the number of settlements the aliens have in this galaxy is N.  How many stars have they bothered to settle?  It turns out to be a very lonely thing to settle stars (as discussed above.) My guess is that N turns out to be a small number.  They'll pick the safest, most stable stars to settle around.  No point in having your civilization annihilated in a supernovae, so they will spread out, but no reason to go every where when you can build your own planets where ever you want.  Let's calculate the minimum N would have to be if the aliens were going to tell their robots to talk to us tomorrow.

There would have to be at least one settled star within 30-50 light years of us.  As mentioned before, this is about 133 stars.  So if one of these stars was settled that would be ~1% of the stars would be settled.  That means that N would be 1% of all the stars in the galaxy and since there are about 100 billion stars in the galaxy, N, the number of settled stars, would be 1 billion stars.  Now that seems pretty wasteful.  In fact, they've probably settled just enough stars to be close enough to everywhere in the galaxy to 'take care' of new intelligent races and protect themselves.  How close do they need to be?  How long can they risk us developing technology before we become a risk to them?

Those dang Killer Robots

What's the worse scenario?  Killer robots, of course.  That's always the worst scenario.  There's a chance we might be stupid enough to make killer robots that can reproduce and continue to evolve their technology and killing abilities.  (Okay, that's sort of what we are, but we're not quite repairable enough to matter, but... it's probably about the same amount of time to make our lifetimes be long enough to be a threat, so we can do the calculation twice to see if we get comparable answers.)

How long would it take to make killer robots that can reproduce themselves?  Well, Ray Kurzweil thinks it's going to happen in about 25 years.  Paul Allen thinks we will still be waiting for the singularity 85 years from now.  Over 80% of the things Ray predicted have come true, on time. Nothing that Paul Allen has said will come true has ever come true. (I can give some very personal examples if you want me to.)

And let's remember what we are trying to estimate here: How long from the invention of radio will a species be able to invent killer robots?  Remember, this is an existential threat to aliens, they don't want to get it wrong.  "Rats, was that a killer robot that just passed me? Dang, if I had just annihilated the human race a year earlier we wouldn't all have to die.  Sorry about that, honey.  I'll try harder next time."  So they are going to be very, very conservative.  Cripes! I'm starting to scare myself.

Let's just assume, for sanity's sake, that Ray is crazy optimistic.  So radios to killer robots takes at least 150 years. Shoot. The aliens would want to put small settlements within 75 light years of everywhere. Rats. I guess they do need to have 25 billion stars settled.  Or at least that many outposts, maybe not that many settled stars.  Get ready to kiss your ass goodbye.


So this makes a few predictions that we can test.  We could look for alien robots watching the solar system.  How can we do that?  That's another blog post, but the easiest thing would be to set up a huge radio telescope looking back towards the sun from far away.  That way we could detect anything the robots were sending out.  Sounds like a great project for the first killer robots we make. And it's not even out of bounds for current technology, just expensive.  And we could use the telescope to look at everything else in the galaxy with very fine detail.  A worthwhile project all around.

Second, this line of reasoning predicts that we will be contacted by aliens before the singularity. Since that's going to be around 2045... they should be here any minute.  There's a few other lines of reasoning that say the same thing, but that's another blog post (how can you predict the lifetime of something you find at random? Or why are you alive now and not in the future?)

So, sorry to be such a downer, but despite Stephen Hawking's best intentions, it's already too late to change this.  The aliens will be here and it will most likely be within your lifetime.  I'm not sure how to get ready for THAT, except that it's another blog post...

First Killer Robots

Here's a picture of the first killer robot: automated radar guided gatling gun to shoot down jets. Installed on the Missouri battleship during Reagan's presidency.  Looks frighteningly like a dalek, doesn't it?

Thanks for reading!
 -Dr. Mike


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