Are scientists looking for alien life?

Dan on Twitter wants to know if scientists are looking for alien life. Izzie Clarke was joined by physicist Ben McAllister from the University of Western Australia who tackled the topic...

Ben - I love this question. The answer is a resounding yes! We've been doing it for a very long time, at least as early as the 1900s, the very early 1900s, and probably much earlier than that - in terms of people just looking up into space and hoping that they see something. But in terms of concentrated efforts using good technology, we'll have started around the beginning of the 1900s, and really kicked into high gear in the late 70s, early 80s timeframe.

Broadly, searches for extraterrestrial intelligence, as they are known, fall under the umbrella term SETI, perhaps you've heard of it, and there's a few different institutions around the world that adopt that name to describe the things they do. There are two main types of SETI search. The probably more traditional one is to essentially get a big radio telescope - kind of like a satellite dish that you would have on the roof of your house - to try and point into space and pick up radio waves coming in that could be signals from alien civilisations. We humans are putting radio waves out all the time, so it's not a stretch to imagine that alien civilisations might be doing something similar.

Although there have been no detections just yet, there was at least one really interesting period in 1977 at the University of Ohio, I believe. They have this telescope called The Big Ear and it received what is widely considered to be the strongest candidate signal from space for an alien message. It's called the Wow! signal. It's basically just an extremely powerful radio signal that hit the telescope once. It lasted about 70 seconds or something like that, some short period of time, and has never been observed again. No one's been able to explain any source for it, so it's widely considered to be the closest thing to an alien communication we may have observed.

Izzie - So what are people actually looking for? Is it predominantly just signals or is there anything more to it than that?

Ben - Okay. The ones with radio telescopes and stuff typically are looking for radio waves from outer space. But there are other ways you could think about searching for extraterrestrial life and these typically revolve around looking for what are called alien megastructures. Yeah, this is getting a little bit more sci-fi, but it is extremely cool.

We theorise basically that any advanced civilisation will constantly be increasing its demands for energy, until you reach a point where you basically require all of the energy output by a given star. Our star that we orbit around - the Sun - we don't come close to harnessing even all the energy from it that hits the Earth, let alone all the energy puts out in all directions at all times. But a super advanced alien civilisation might want to do that, and if they were going to do that they would want to build something that we have called a Dyson sphere, which is named after this guy called Freeman Dyson. He was a physicist - he has nothing to do with the vacuums.

Izzie - That was my next question.

Ben - I thought that as well. I was like, “oh wow”, but definitely not. So the idea behind a Dyson sphere, you basically create some giant structure that encapsulates a star and sucks all the energy out of it, like an array of solar panels or something. Maybe instead of having one big rigid structure, you would have a whole bunch of little satellites that orbit the star in rings and stuff, and just absorb all the solar energy that way, and then you could have it for whatever purpose you want. And if that was the case, you might be able to see signatures of these things, like Dyson swarms they're called, these swarms of satellites moving around distant stars.

So pretty much every time we see a distant star with a weird dimming pattern or something, like there's something weird about the sunlight coming off it, some people get pretty excited about the fact that it might be a Dyson sphere, or a Dyson swarm, or something. But so far there have been no confirmed reports.