"...press 1 to be taken to our leader, press 2 to strip-mine Earth for its natural resources..."
We’ve seen it all in the movies enough times: finally we get proof that we’re not alone. But how would it really go down?
Fortunately head alien-botherer from SETI Seth Shostak has given us some the inside skinny in his excellent book “Confessions of an Alien Hunter“, which I highly recommend if you’re a fan (and even moreso if you’re a critic) of SETI
The government would cover it up, right?
Nope. The first thing that would happen if an astronomer discovered an candidate signal is get another astronomer on the other side of the world to check it. This eliminates the possibility that the signal is anything boringly local like air traffic control, the military or a satellite. The parallax view offered by a remote observer would confirm that the signal really does come from a far off point. The bottom line is that by the time the signal had been confirmed as alien, no one government could silence it. The genie would be out of the bottle.
And even if they did try and cover it up, somebody would just put it on Wikileaks and the press would snap it up. There’s no way you could cover up a discovery of this magnitude.
Ok, so we’d immediately start to decode the signal?
Er, no. Despite the enduring image of Jodie Foster in Contact sitting by a dish wearing headphones, the reality is that SETI processing is all done automatically, by computers. An unfortunate side effect of the mathematical transformation they do while scouring the background noise to find blips is that it averages everything. Obviously averaging everything destroys the actual information, although it will alert you to the fact that you’ve got a signal in the first place. That’s a bit of a pain, but it’s the best we can do.
Right, so we’d just point our dishes in the same place, and get the signal again?
Um, no again. Unless the signal came from our immediate neighbourhood, or was stupendously powerful, we’re unlikely to be able to extract any information from it, even if we detected it.
You can detect radio signals at much weaker strengths than you can extract information from them. You can see this when you scan for wifi signals with your laptop. You can detect lots of hotspots, but the signal isn’t necessarily strong enough to let you form a reliable connection. The wifi base station can pump out as much data as it wants, but your little antenna just isn’t up to the job. It’s likely to be ditto with signals from little green men.
So how would we decode it?
We’d build a bigger antenna. A MUCH bigger one. More likely, we’d actually build a behemoth made up of massive numbers of smaller dishes all working together. How big? A 1971 NASA study estimated a thousand 100m dishes, which is big boys’ engineering. Once we’d built all that, we would have enough receiving power to grab a good signal.
So what happens if the signal stops before we’ve built this mega-receiver?
We’re screwed. This is entirely possible if the signal wasn’t meant for us, for example if the original signal was Earth being inadvertently swept by the beam of some long range communication between a moving object and another point. Whoever coughed up the cash for building the receiver would probably be pretty pissed off.
Ok, so let’s say we’ve got the message. What would ET want to say?
We really don’t know. We know the kind of things we’d put in a message: some basic maths and chemistry, a map, some cultural tidbits, and a nice cheery hello. But we really shouldn’t try to second-guess the contents of a message. It would be logical for the initial message to be simple and easily understood, and based only on knowledge that a civilisation would require to receive it in the first place (ie: roughly the technological level of the early 20th century). Building radio receivers requires a certain understanding of maths and physics, and since the laws of physics are the same everywhere there should be at least some common knowledge between any two civilisations that can control radio waves. Using that body of knowledge as a kind of crib sheet for constructing a language to communicate in would seem the best strategy. Or not, maybe ET would rather beam their soap operas at us.
When will the signal arrive?
Well, if you’re a pessimist you’d say: never. We’ve been looking up for decades now and we’ve heard almost nothing of interest. Coupled to the fact that nobody from out there has ever been proved to have shown up here, despite having many billions of years to have evolved enough to do so, it’s entirely possible that there’s just nobody out there. Or at least that life is so laughably rare that finding another civilisation is almost impossible.
If however you’re of a more cheery, optimistic inclination you’d say: soon. The massive rise in computer power in recent years has enormously enhanced the ability of SETI scientists to scour the heavens. Their surveys are going from sporadic peeks at a select few stars to massive sweeping sky surveys. It’s not unreasonable to say that within a few years we’ll have checked all the good candidates, and that within a few decades we’ll have comprehensively searched the entire sky for all the viable frequencies. If ET is phoning Earth at all, we’ll see them.