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Who’s Out There?

The Advertiser | 16 April 2010

The SETI Institute's Allen Telescope Array in California

Fancy a close encounter of the third kind – finding other life in our galaxy? Don’t hold your breath, Clare Peddie finds.

WHAT'S THE CHANCE of finding intelligent life in our galaxy, the Milky Way? Pretty slim, according to Wilson da Silva, editor of COSMOS Magazine. He has updated the famous Drake Equation, used in the search for extra-terrestrial intelligence (SETI), to reveal aliens are even harder to find than we thought just 50 years ago. That was when the search began in earnest, led by radio astronomer Dr Frank Drake.

He hoped to find ET by scanning the sky for radio signals. The mission continues to this day, as Dr Drake is now chairman of the SETI Institute, but the silence is deafening. Writing in the latest issue of COSMOS, Dr Drake says the silence is not eerie, it’s predictable.

“If you take the most plausible guess for the number of detectable civilisations in our galaxy, the answer you get is about 10,000. That’s a big number.”

“If you take the most plausible guess for the number of detectable civilisations in our galaxy, the answer you get is about 10,000. That’s a big number,” he says. “And it requires civilisations to stay detectable for 10,000 years or so.

“Nevertheless, that means in our galaxy, with its 100 billion or so stars, only 1 in 10 million stars will have a detectable civilisation. Which suggests SETI will not succeed until we have searched some 10 million stars. And, of course, we don’t know what frequency to search at!”

Our planet has been buzzing with radio waves for decades, but we’re about to go quiet with the switch to digital television. Military radar has toned down the volume and mobile phones require less power to achieve the same result.

“Very soon, the Earth will become undetectable,” Dr Drake writes. “If we are typical of what a civilisation goes through, it means the search will be much more difficult than we ever imagined.”

With changing technology, he says, optical signals may be a better bet. But then who’s to say these aliens are following our path of technological development. They may be doing something far more sophisticated. They may even be masking their signals to avoid being detected.

COSMOS's Wilson da Silva (send from the left) speaking to students after his lecture at RiAus

At the moment, Mr da Silva says, we’re only likely to trip over those civilisations that have set up a beacon to highlight their existence. “Only a very powerful beacon – intended to be found by new civilisations – could be detected by us,” he says. “But just sending such a signal would be extremely difficult, and expensive. And why would you do it?”

To celebrate the SETI anniversary, Mr da Silva plugged the latest science into the Drake Equation. Dr Drake listed all the questions science would need to answer in order to predict the number of detectable civilisations in the galaxy, then realised answers to all of the questions could be multiplied to find the ultimate answer to the ultimate question.

Dr Drake agrees the equation still works. “The only thing that’s changed is the numbers we put into it,” he says. “When I first invented the equation we had to guess some of the factors. A lot of those have now been established through observation.”

Working through the Drake Equation is a good exercise for students, who learn a lot about science along the way.

But the answer Mr da Silva has come up with is a much smaller number than Dr Drake found 50 years ago – a low 0.00127. What does it mean? “It means that during any 100,000 period in our galaxy’s history, around 127 detectable civilisations will crop up,” Mr da Silva says.

“It may not sound too bad but it actually makes the odds of us tracking and finding one of them really, really hard, especially within a few hundred years of looking. The chances are actually minimal at best.”

He says working through the calculation is a good exercise for students, who learn a lot about science along the way.

South Australian science teachers puzzled over the problem at their annual conference yesterday. SA Science Teachers Association president Bronwyn Mart says the conference brings together teachers, laboratory officers, tertiary students and educators all striving to improve their ability to infect students with a love of science.

Mr da Silva gave the keynote presentation at the South Australian Science Teachers Association conference

Mr da Silva gave the keynote presentation and the program features a swag of scientists, including climate change Professor Barry Brook from the University of Adelaide, and the director of the Flinders Artificial Intelligence and Language Technology Laboratories, Professor David Powers.

Today’s children will decide the fate of our civilisation and Mr da Silva hopes the light of humanity will continue to burn brightly. “If we are alone in the cosmos, then we have an obligation to ensure that our spark of intelligence is not lost, that we protect life on our planet,” he says.

“I would argue we also have an obligation to ensure the survival of humanity by expanding beyond the planet. You can be sure that one day a massive calamity will befall our world – asteroid, comet impact, solar burst, nuclear war – and we could disappear or our civilisation could fall.”


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