NARRATION

It's a question that keeps some awake at night. Are there advanced civilisations out there? Civilisations light years ahead of us?

Dr Graham Phillips

Think about it. The earth is a newcomer on the galactic scene. We've only been around for 4.5 billion years. The galaxy is more like 10 billion years old. There could be civilisations out there billions of years more advanced than we are.

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And considering our progress over just a few decades a billion years of advancement is a mind-boggling prospect. Some astronomers try to imagine just what such ETs might have achieved.

Professor Geoff Marcy

The advanced civilisations out there have vast telescopes, almost certainly.

Dr Jason Wright

Their astronomers have already catalogued the sun. They've already noticed that the sun is orbited by many planets. They have probably discovered that one of them is like the Earth.

Professor Geoff Marcy

They have mechanisms by which they can listen to our electromagnetic communication. They're listening to this interview right now. Ah, why not? They can store it all away. Maybe they're taking pictures as well.

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It all sounds like crazy talk. But what's inspired these astronomers to hunt for ET is the recent discovery of just how many potential Earths could exist.

Dr Graham Phillips

Back when I was a young astrophysicist, we didn't know of any other planets outside the solar system, let alone other Earths. Indeed, there were scientists back then that argued there's probably very few Earths anywhere in the galaxy. Well, that view has changed - radically.

Professor Geoff Marcy

The galaxy that we live in, with its 200 billion stars, is packed with Earth-sized planets that are lukewarm. Almost certainly, many of them have water. Some of those worlds would have some continents in which primitive life can spring forth and Darwinian evolution would lead presumably to technological, dexterous, vocal life as we Homo sapiens are.

NARRATION

So looking for ET may not be so crazy after all.

Dr Graham Phillips

There's nothing new about searching for evidence of aliens. Astronomers have been pointing their radio telescopes at the skies for decades hoping to find one of ET's signals. So far, without success, I should say. But now there's a new way of searching for ET.

Professor Geoff Marcy

We have a marvellous new technique for hunting advanced civilisations.

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It involves laser beams. These consist of pure colours. A single frequency of light. A natural process is unlikely to produce them. So find these in the galaxy and you have evidence for ET. Not alien dance parties, but alien laser communications.

Professor Geoff Marcy

The advanced civilisations would have colonies, they would have spacecraft, maybe they've colonised other planets. And they would be communicating with their brethren.

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While we communicate with our spacecraft using radio waves and tracking stations, like the one here at Tidbinbilla, even NASA might soon switch to laser communications.

Glen Nagle

Yeah, certainly they would like to particularly use it when we eventually, one day, send humans off to somewhere like Mars. So rather than just getting a radio signal and hearing those voices from that planet or seeing just individual still pictures, we could get video streaming directly from the Red Planet.

Professor Geoff Marcy

The great thing about lasers is that they can be very high frequency. Blue light, ultraviolet light. And so you can send a very high bandwidth of information. Something like 1 with 12 zeros after it worth of bits per second.

NARRATION

So Jeff is using the Keck telescope in Hawaii to look for evidence of alien lasers. We'll catch up with his search shortly. But meanwhile, Jason Wright is looking for a different kind of alien technology - Dyson spheres.

Dr Jason Wright

So Freeman Dyson, the brilliant physicist and polymath, hypothesised that very advanced civilisations would need a lot of energy and so they would build lots of solar collectors around their stars to gather all of this energy.

Associate Professor Charley Lineweaver

We are putting solar cells everywhere, more and more and more. Pretty soon we'll cover the whole Earth with them. Well, why not just put a whole sphere around the sun and collect all the energy from there? That's a Dyson sphere.

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If these exist around stars, the laws of physics dictate we could detect them, because whenever energy's used, heat must be produced.

Dr Jason Wright

When your computer uses energy out of the wall, after doing lots of interesting work with it, your computer warms up and it gets rid of that energy by giving it away as heat. So in the same way, advanced civilisations that might be collecting huge amounts of power from their stars, will have to give that energy away as heat when they're done using it.

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To find a Dyson sphere, we need a telescope that sees heat rather than light - infrared radiation.

Dr Jason Wright

The problem is that this sort of radiation doesn't penetrate the Earth's atmosphere very well and the Earth's atmosphere itself gives a lot of it off. So you have to go to space.

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In 2009, the infrared detecting WISE telescope was launched. It's looked at everything from nearby asteroids to distant galaxies. But it could also spot Dyson spheres. They'd be stars emitting a lot of heat, although finding them is not as easy as it sounds.

Dr Alan Duffy

It's actually very hard to definitively say it's a Dyson sphere, simply because we don't really know what that would look like in practice. Our best guess is it will look like a very red, glowing region. But that's actually kind of what a brown dwarf - a failed star - looks like as well - it tends to glow in

infrared.

Associate Professor Charley Lineweaver

Well, a lot of stars have dust around them. And dust are emitting in the infrared, so is it a Dyson sphere or is it a dust-enshrouded star? How are we going tell the difference?

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It'll require extremely careful observations.

Dr Jason Wright

We're looking for anomalously high levels of heat, so a star that doesn't seem to have any dust, doesn't have any obvious sources of this mid infrared radiation, but that nonetheless is glowing very brightly.

NARRATION

Jason's hunt for Dyson spheres in our galaxy is just beginning, but he's already completed perhaps an even more interesting search. To understand it, you need to know about the Kardashev scale. It's a way of measuring just how much more developed than us ET could be.

Dr Alan Duffy

The Kardashev scale was invented by Nikolai Kardashev, a Russian astronomer.

Professor Geoff Marcy

There is an imaginary set of stages that advanced civilisations will aspire to.

Dr Alan Duffy

It's basically a way to categorise civilisations by their energy use.

Dr Graham Phillips

A Type I civilisation is one that's still confined to its own planet, but using pretty much all the energy resources there. We puny Earthlings might reach that stage in a couple of centuries.

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Type II is using all the energy of their star, with, say, a Dyson sphere.

Dr Graham Phillips

A Type III civilisation has gone one step further and moved out into its galaxy and commands the energy resources of many, many stars.

Professor Geoff Marcy

The final level would be to build a sphere to collect all of the energy from its entire galaxy - all 200 billion stars or a large fraction of them.

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They might even be extracting the energy from the giant black hole at the centre of their galaxy.

Dr Jason Wright

It doesn't matter what they do with the energy - they might be building giant computers or death stars or lasers or rocket ships or whatever it is. If they're using the energy, they have to get rid of it as heat when they're done with the energy and that's all we're looking for. So we hope that this makes us less dependent on guesswork about what an advanced civilisation would be like.

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Jason combed through the WISE telescope data, looking at many thousands of nearby galaxies and came up with a clear result.

Dr Jason Wright

We can show that there aren't any galaxies, out of the 100,000 that we studied in the sky, that are filled with civilisations using most of the starlight. So we can, for the first time, rule that hypothetical class of civilisation out.

NARRATION

But not all's lost. The other classes of civilisation could still be out there. Meanwhile, Geoff's laser hunt in Hawaii is well underway. Catalyst ventured here a couple of years ago to visit the high-altitude Keck telescope.

Dr Graham Phillips

OK, we're at the top. 14,000 feet - that's more than 4 kilometres up. I must say, I feel very woozy. It's like I've had a couple of wines.

NARRATION

The Keck is an optical telescope, so it can look for alien laser light. And it's massive.

Dr Graham Phillips

That mirror is ten metres from side to side. Incredible.

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Geoff points the Keck at a star, collects all its light, then looks at the colours present in it.

Professor Geoff Marcy

We're watching to see if there's any bright beams of light at just one colour. That would be the lasers from any advanced civilisations that live there.

NARRATION

To maximise the chance of success, another space telescope, the Kepler, lends a hand. Kepler's already identified many stars that have planets and these are ideal candidates for Geoff to point the Keck towards. The first part of the search is to take a kind of crude quick look and that's already been completed.

Professor Geoff Marcy

And to tell you the bottom line, and frankly, we haven't announced this publicly, but I'm happy to do so, we didn't find any. We looked really hard - 2,000 stars. We didn't see a single laser beam.

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It was a disappointing result. But it's part two of the project - a detailed search for lasers - that will be most interesting. And that's only just beginning. Now it's still early days, but what if we find nothing? Well, advanced aliens could still be out there.

Dr Alan Duffy

Maybe they are and we just don't recognise it as such. They're so far beyond us, as we are to, say, ants. We wouldn't even think of talking to an ant, so why would these civilisations think of talking to us?

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Or maybe there are no aliens, and in the enormous vastness of space, we could be all alone.