Steven Hawking Warns-Don't Talk To Aliens

From The Sunday Times
April 25, 2010
Don’t talk to aliens, warns Stephen Hawking

Hawking has depicted what kinds of alien could be out there
Jonathan Leake
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THE aliens are out there and Earth had better watch out, at least according to Stephen Hawking. He has suggested that extraterrestrials are almost certain to exist — but that instead of seeking them out, humanity should be doing all it that can to avoid any contact.

The suggestions come in a new documentary series in which Hawking, one of the world’s leading scientists, will set out his latest thinking on some of the universe’s greatest mysteries.

Alien life, he will suggest, is almost certain to exist in many other parts of the universe: not just in planets, but perhaps in the centre of stars or even floating in interplanetary space.

Hawking’s logic on aliens is, for him, unusually simple. The universe, he points out, has 100 billion galaxies, each containing hundreds of millions of stars. In such a big place, Earth is unlikely to be the only planet where life has evolved.

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“To my mathematical brain, the numbers alone make thinking about aliens perfectly rational,” he said. “The real challenge is to work out what aliens might actually be like.”

The answer, he suggests, is that most of it will be the equivalent of microbes or simple animals — the sort of life that has dominated Earth for most of its history.

One scene in his documentary for the Discovery Channel shows herds of two-legged herbivores browsing on an alien cliff-face where they are picked off by flying, yellow lizard-like predators. Another shows glowing fluorescent aquatic animals forming vast shoals in the oceans thought to underlie the thick ice coating Europa, one of the moons of Jupiter.

Such scenes are speculative, but Hawking uses them to lead on to a serious point: that a few life forms could be intelligent and pose a threat. Hawking believes that contact with such a species could be devastating for humanity.

He suggests that aliens might simply raid Earth for its resources and then move on: “We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet. I imagine they might exist in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonise whatever planets they can reach.”

He concludes that trying to make contact with alien races is “a little too risky”. He said: “If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn’t turn out very well for the Native Americans.”

The completion of the documentary marks a triumph for Hawking, now 68, who is paralysed by motor neurone disease and has very limited powers of communication. The project took him and his producers three years, during which he insisted on rewriting large chunks of the script and checking the filming.

John Smithson, executive producer for Discovery, said: “He wanted to make a programme that was entertaining for a general audience as well as scientific and that’s a tough job, given the complexity of the ideas involved.”

Hawking has suggested the possibility of alien life before but his views have been clarified by a series of scientific breakthroughs, such as the discovery, since 1995, of more than 450 planets orbiting distant stars, showing that planets are a common phenomenon.

So far, all the new planets found have been far larger than Earth, but only because the telescopes used to detect them are not sensitive enough to detect Earth-sized bodies at such distances.

Another breakthrough is the discovery that life on Earth has proven able to colonise its most extreme environments. If life can survive and evolve there, scientists reason, then perhaps nowhere is out of bounds.

Hawking’s belief in aliens places him in good scientific company. In his recent Wonders of the Solar System BBC series, Professor Brian Cox backed the idea, too, suggesting Mars, Europa and Titan, a moon of Saturn, as likely places to look.

Similarly, Lord Rees, the astronomer royal, warned in a lecture earlier this year that aliens might prove to be beyond human understanding.

“I suspect there could be life and intelligence out there in forms we can’t conceive,” he said. “Just as a chimpanzee can’t understand quantum theory, it could be there are aspects of reality that are beyond the capacity of our brains.”

Stephen Hawking's Universe begins on the Discovery Channel on Sunday May 9 at 9pm

Finding Extra Terrestial Life

Hunting ET: Astrobiology and the quest for extraterrestrial life

The discovery of life elsewhere in the Solar System would 'profoundly change our understanding of where we came from and our place in the cosmos', astrobiologist Lewis Dartnell told Sam Wong ahead of his public lecture on the subject this week

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Methane, a possible signature of life, has been detected in the atmosphere of Mars. Photograph: Nasa Planetary Photojournal/PA

Is there anybody out there? That's the big question scientists are asking in the emerging field of astrobiology. Its practitioners bring together expertise from a variety of disciplines in their quest to determine whether there is life beyond our green and pleasant home planet.

"The question of whether we are alone in the universe or not is something that every single one of us has wondered about at one point," says Lewis Dartnell, an astrobiology researcher at University College London and author of Life In The Universe: A Beginner's Guide. "Whatever the answer, I think it would profoundly change our understanding of where we came from and our place in the cosmos."

At first glance the prospects of finding life elsewhere in our own solar system don't look good, since every planetary body other than our own is either scorching hot or ferociously cold. Then again, we know that on Earth life can flourish in the unlikeliest locations, from polar ice caps to hydrothermal vents reaching 113C.

The first place to look has naturally been our neighbouring planet, Mars. When Nasa dispatched two Viking spacecraft to land on the Red Planet in the 1970s, they sent equipment designed to carry out experiments to test whether there might be microorganisms in the Martian soil.

The instruments detected no trace of any organic chemicals. However, one experiment, called "labelled release", did produce a positive result. When a dilute solution of nutrients containing radioactive carbon atoms was added to a soil sample, carbon dioxide gas was given off that contained the same labelled carbon atoms.

This was taken by some to indicate that the nutrients must have been metabolised by a life form. But most scientists believe that the experiment was flawed, since the chemical reactions that it detected could occur without any biological assistance.

In 2003, the European Space Agency's Mars Express spacecraft detected traces of methane in Mars's atmosphere. More recently, vast plumes of the gas have been detected by Earth-based telescopes. Since the gas is highly unstable, this suggests that there must be some ongoing process that is producing methane on Mars. Although geological processes could account for it, the absence of any known volcanic activity on the planet raises hopes that subterranean microbes could be the source.

"Provided it was protected from the harsh radiation and chemical environment right on the surface of Mars, life there could remain safely dormant for long periods of time," says Dartnell. "Subterranean life, miles deep in the warmer Martian crust, may even be active still today, feeding off minerals in the rock like the hardy organisms on Earth."

Nasa is due to launch its most ambitious probe to date in 2011. The Mars Science Laboratory, christened Curiosity, aims to determine whether life has ever existed on the planet next door. Esa is also hoping to send a lander to Mars in 2018 to look for signs of life. In the more distant future, space scientists want to bring back a sample of Martian rock to Earth so that it can be investigated more thoroughly.

Further afield, the satellites of the gas giants are the locations that arouse most interest in astrobiologists. The icy surface of Jupiter's sixth moon, Europa, is covered with cracks just like polar ice on Earth, suggesting that it is continually breaking up and reforming. This could only be explained by the presence of liquid water underneath. The subsurface ocean could be kept warm by tidal forces resulting from Jupiter's gravitational pull.

"In the dark depths of our own oceans we find hardy microbial life forms surviving off nothing more than the inorganic chemicals spewing out of the Earth's crust," says Dartnell. "Just the same kind of life might be lurking beneath the icy crust of Europa."

The surface of Titan, the largest satellite of Saturn, is strikingly Earth-like. Photographs taken by the Cassini orbiter in 2004 revealed mountain ranges, dunes and even lakes – not lakes of water, admittedly, but astrobiologists think that the liquid methane on Titan's surface could support some sort of life form quite different from anything that exists on Earth.

"Any life on the surface of Titan would need to operate on an exotic biochemistry, based on liquid methane rather than water," says Dartnell.

Another of Saturn's moons, Enceladus, attracted the attention of astrobiologists when Cassini discovered plumes of water vapour and hydrocarbons spewing from beneath its icy surface, raising hopes that there might be underground water.

Last month Nasa reported that the plumes contain ammonia, which can allow water to remain liquid down to a temperature of minus 97 degrees Celsius.

The plumes also contain sodium – an exciting finding for astrobiologists like Dartnell. "It implies the plumes are coming from underground caverns of salty water, exactly the sort of environment that could provide the conditions for life."

Nasa and Esa have plans in the pipeline to send probes to both Jupiter and Saturn. Earlier this year they announced that the Europa Jupiter System Mission would be given priority over the Titan Saturn System Mission, with the former due to begin its six-year voyage in 2020.

Lewis Dartnell was our guest on this week's Science Weekly podcast, "What would an alien look like?". He will give a public lecture about astrobiology on Sunday at 5pm as part of the Your Universe event at University College London, a series of talks and activities starting on Thursday to celebrate the International Year of Astronomy 2009