NARRATION
Hawaii is a tourist magnet. People flock here to swim, sunbathe and play. But we're here for something much better than all that.

Dr Graham Phillips
We're gonna visit an island a few hundred kilometres that way, where they've got one of the biggest optical telescopes in the world. And, believe it or not, they're using it to hunt for aliens, with a method that's never been tried before.

NARRATION
The telescope's on the top of the Mauna Kea volcano. This is the view, just two-thirds of the way up - already higher than any Australian mountain. So, my minder and I rest, to acclimatise to the thin air. Then, it's a drive up to the really rarefied heights at the top, where the Keck telescopes are. But first, let's go to San Francisco, to see why we're visiting the Kecks. Across the bay, at the University of California, Berkeley, is astronomer Geoff Marcy.

Prof Geoff Marcy
The greatest human question we know of is whether there is life elsewhere in our universe.

NARRATION
Geoff has been interested in 'elsewhere in the universe' for decades. He's discovered more planets orbiting other suns than any other person. Indeed, he started looking for these exoplanets back when people said it just couldn't be done.

Prof Geoff Marcy
And at that time, everybody thought I was crazy. Then I thought, 'You know, I'm gonna take all my astronomy chips, and place a bet on finding exoplanets.'

NARRATION
It took eight lonely years of scouring the skies, but on December 30 1995, the cosmic bookies paid out on Geoff's bet.

Prof Geoff Marcy
It was, erm... spine-tingling. I can remember the hairs standing up on the back of my neck, and I looked at the computer screen and I thought, 'That's the signal I've been looking for, for all these years.' It was marvellous.

NARRATION
Today, almost 1,000 exoplanets have been confirmed, astonishing astronomers by just how weird they can be.

Prof Geoff Marcy
Some of the planets orbit their stars in elongated orbits, not nice circles like we have in our solar system. Some solar systems have their Jupiters orbiting so close to the host star that the Jupiters are blowtorched to thousands of degrees.

NARRATION
But the biggest surprise was just how many planets are out there.

Dr Seth Shostak
But essentially every star is now known to have planets - we know that. Most of the stars have planets. That means the number of planets, just in our galaxy, is on the order of a million-million - a trillion. That's a big number.

NARRATION
And a big number of potential home planets for ET.

Dr Seth Shostak
There's so much real estate out there that's suitable for life, that, you know, they've gotta be out there. If this is the only place in the cosmos where biology has begun, if this is the only place where anything interesting is happening, then this is a miracle. And I can tell you, after 500 years of being disillusioned about miracles, most astronomers are very leery of believing in miracles. So the non-miracle explanation is there's plenty of life out there.

NARRATION
The question is - are there any advanced civilisations? To find out, Geoff's going out on a limb again.

Prof Geoff Marcy
We search for laser beams from advanced civilisation - and I'm embarrassed to talk about it - by using some of the world's largest telescopes, like the Keck telescopes in Hawaii.

NARRATION
Which brings us back here. This is the top of Mauna Kea. There are a lot of telescopes here, because the clear skies make the viewing so good. The scenery's stunning, but the feeling of going from sea level to these heights is not so good.

Dr Graham Phillips
OK, we're at the top - 14,000ft. That's more than 4 kilometres up. And I must say, I feel very woozy - it's like I've had a couple of wines. So your oxygen levels here have to be constantly monitored.

Man
Yes, you're running 88% of oxygen in your blood, and your heart rate is at 68.

Dr Graham Phillips
88% is enough, is it?

Man
Yeah, that'll work just fine.

NARRATION
Inside is the impressive instrument.

Dr Graham Phillips
Now that is some telescope. I've seen quite a few in my time - I've never seen anything like that. That mirror is ten metres from side to side. Incredible.

NARRATION
The mirror could only be made this big by building it from 36 hexagonal segments. They must all act as one to form a near-perfect mirror. Geoff will use this telescope tonight. Multitasking - looking for exoplanets, and laser beams sent by alien astronomers. Why would they beam lasers into the galaxy? Because our astronomers routinely do.

Prof Geoff Marcy
They illuminate the upper atmosphere, trying to correct the distortions that the atmosphere introduces.

NARRATION
Information from the laser allows the distortion in the image, caused by air turbulence, to be removed. And here's the thing - telescopes, and therefore their lasers, are always pointed at the star system being observed. If that system happened to be ours, Geoff thinks we should be able to detect laser light beamed directly at us.

Prof Geoff Marcy
Point the Keck telescope at nearby stars, and we look for light coming at just one colour - because lasers emit their light at just one colour - and if we see a light beam at just one wavelength of light, we know we've got a laser and that would have to be an artificial machine that made that light. Voila - we have a good sign of intelligent life.

NARRATION
Tonight's observations have begun. Remarkably, Geoff can run the Kecks from his Berkeley office. And it seems anyone can do it.

Dr Graham Phillips
Could I do one?

Prof Geoff Marcy
Start the next exposure.

Dr Graham Phillips
So I click on 'expose' over here?

Prof Geoff Marcy
That's right - left button.

Dr Graham Phillips
That's it?

Prof Geoff Marcy
Excellent!

Dr Graham Phillips
I've just pushed the 'go' button on one of the biggest telescopes in the world.

Prof Geoff Marcy
And the photons are streaming in.

Dr Graham Phillips
This is fun!

Prof Geoff Marcy. 
It's astronomy research - it doesn't get better than this.

NARRATION
When the exposure's finished, a spectrum's produced.

Prof Geoff Marcy
Well, this is the spectrum of a star, just as we observe it at the Keck Observatory. And what you're seeing are all the colours of the rainbow - blue, green, yellow and red.

NARRATION
Now, this spectrum is normal. Among those colours, the black lines are missing frequencies, because that particular coloured light has been absorbed by the atoms in the star.

Prof Geoff Marcy
For example, these two absorption features in the spectrum are caused by sodium atoms in the star's atmosphere.

NARRATION
The tell-tale sign of a signal from ET is not missing light, but additional frequencies of laser light. Now, it's early days and none have been found yet, but if they are, the discovery would be momentous.

Dr Seth Shostak
The really important change will be the philosophical change, because you will know, from that day forward, forever, that we're not the only kid on the block, we're just another duck in the row.

NARRATION
Could we have a chat with the other kids on our galactic block? Well, sadly, maybe not. If they're able to contact us, they'll be way more advanced than us - we won't understand their communications.

Dr Seth Shostak
And it's sort of like, you know, giving books to Neanderthals - I mean they're probably not gonna get a whole lot out of it. Maybe they have an education project. Maybe the aliens, you know, got some money to educate the other intelligent species of the galaxy, so they send us picture books, or their rock'n'roll, or something we could understand. It's possible.

NARRATION
Let's hope there's some alien rock'n'roll coming to our airwaves soon.

STORY CONTACTS

Professor Geoff Marcy 
Professor of Astronomy, 
University of California, Berkeley

Dr Seth Shostak 
Senior Astronomer
SETI Institute, California