Supplementary reading

Read the three given texts, underline the presented opinions of the scientists and express your personal point of view on the existence of Extraterrestrial Live, the consequences of possible visits of aliens.

Text A Is Stephen Hawking right about aliens?

Stephen Hawking thinks that making contact with aliens would be a very bad idea indeed. But with new, massive telescopes, we humans are stepping up the search. Have we really thought this through?

By ALOK JHA, the Guardian, April 30, 2010

In February 2008, Nasa sent the Beatles song,’ Across the Universe’, across the universe. Pointing the telescopes in its Deep Space Network towards the north star, Polaris, astronomers played out their short cosmic DJ set, hoping that it might be heard by intelligent aliens during its 430-year journey to the star.

The hunt for intelligent species outside Earth may be a staple of literature and film – but it is happening in real life, too. Nasa probes are on the lookout for planets outside our solar system, and astronomers are carefully listening for any messages being beamed through space. How awe-inspiring it would be to get confirmation that we are not alone in the universe, to finally speak to an alien race. Wouldn't it?

Well no, according to the eminent physicist Stephen Hawking. "If aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans," Hawking has said in a forthcoming documentary made for the Discovery Channel. He argues that, instead of trying to find and communicate with life in the cosmos, humans would be better off doing everything they can to avoid contact.

Hawking believes that, based on the sheer number of planets that scientists know must exist, we are not the only life-form in the universe. There are, after all, billions and billions of stars in our galaxy alone, with, it is reasonable to expect, an even greater number of planets orbiting them. And it is not unreasonable to expect some of that alien lifeto be intelligent, and capable of interstellar communication. So, when someone with Hawking's knowledgeof the universe advises against contact, it's worth listening, isn't it?

Seth Shostak, a senior astronomer at the Seti Institute in California, the world's leading organisation searching for telltale alien signals, is not so sure. "This is an unwarranted fear," Shostak says. "If their interest in our planet is for something valuable that our planet has to offer, there's no particular reason to worry about them now. If they're interested in resources, they have ways of finding rocky planets that don't depend on whether we broadcast or not. They could have found us a billion years ago."

If we were really worried about shouting in the stellar jungle, Shostak says, the first thing to do would be to shut down the BBC, NBC, CBS and the radars at all airports. Those broadcasts have been streaming into space for years – the oldest is already more than 80 light years from Earth – so it is already too late to stop passing aliens watching every episode of Big Brother or What Katie and Peter Did Next.

The biggest and most active hunt for life outside Earth started in 1960, when Frank Drake pointed the Green Bank radio telescope in West Virginia towards the star Tau Ceti. He was looking for anomalous radio signals that could have been sent by intelligent life. Eventually, his idea turned into Seti (standing for Search for Extra Terrestrial Intelligence), which used the downtime on radar telescopes around the world to scour the sky for any signals. For 50 years, however, the sky has been silent.

There are lots of practical problems involved in hunting for aliens, of course, chief among them being distance. If our nearest neighbours were life-forms on the (fictional) forest moon of Endor, 1,000 light years away, it would take a millennium for us to receive any message they might send. If the Endorians were watching us, the light reaching them from Earth at this very moment would show them our planet as it was 1,000 years ago; in Europe that means lots of fighting between knights around castles and, in north America, small bands of natives living on the great plains. It is not a timescale that allows for quick banter – and, anyway, they might not be communicating in our direction.

The lack of a signal from ET has not, however, prevented astronomers and biologists (not to mention film-makers) coming up with a whole range of ideas about what aliens might be like. In the early days of Seti, astronomers focused on the search for planets like ours – the idea being that, since the only biology we know about is our own, we might as well assume aliens are going to be something like us. But there's no reason why that should be true. You don't even need to step off the Earth to find life that is radically different from our common experience of it.

"Extremophiles" are species that can survive in places that would quickly kill humans and other "normal" life-forms. These single-celled creatures have been found in boiling hot vents of water thrusting through the ocean floor, or at temperatures well below the freezing point of water. The front ends of some creatures that live near deep-sea vents are 200C warmer than their back ends.

"In our naive and parochial way, we have named these things extremophiles, which shows prejudice – we're normal, everything else is extreme," says Ian Stewart, a mathematician at Warwick University and author of ‘What Does A Martian Look Like?’ "From the point of view of a creature that lives in boiling water, we're extreme because we live in much milder temperatures. We're at least as extreme compared to them as they are compared to us."

On Earth, life exists in water and on land but, on a giant gas planet, for example, it might exist high in the atmosphere, trapping nutrients from the air swirling around it. And given that aliens may be so out of our experience, guessing motives and intentions if they ever got in touch seems beyond the realm's even of Hawking's mind.

Paul Davies, an astrophysicist at Arizona State University and chair of Seti's post-detection taskforce, argues that alien brains, with their different architecture, would interpret information very differently from ours. What we think of as beautiful or friendly might come across as violent to them, or vice versa. "Lots of people think that because they would be so wise and knowledgeable, they would be peaceful," adds Stewart. "I don't think you can assume that. I don't think you can put human views on to them; that's a dangerous way of thinking. Aliens are alien. If they exist at all, we cannot assume they're like us."

Answers to some of these conundrums will begin to emerge in the next few decades. The researchers at the forefront of the work are astrobiologists, working in an area that has steadily marched in from the fringes of science thanks to the improvements in technology available to explore space.

Scientists discovered the first few extrasolar planets in the early 1990s and, ever since, the numbers have shot up. Today, scientists know of 443 planets orbiting around more than 350 stars. Most are gas giants in the mould of Jupiter, the smallest being Gliese 581, which has a mass of 1.9 Earths. In 2009, Nasa launched the Kepler satellite, a probe specifically designed to look for Earth-like planets.

Future generations of ground-based telescopes, such as the proposed European Extremely Large Telescope (with a 30m main mirror), could be operational by 2030, and would be powerful enough to image the atmospheres of faraway planets, looking for chemical signatures that could indicate life. The Seti Institute also, finally, has a serious piece of kit under construction: the Allen Array (funded by a $11.5m/£7.5m donation from Microsoft co-founder Paul Allen) has, at present, 42 radio antennae, each six metres in diameter, but there are plans, if the Seti Institute can raise another $35m, to have up to 300 radio dishes.

In all the years that Seti has been running, it has managed to look carefully at less than 1,000 star systems. With the full Allen Array, they could look at 1,000 star systems in a couple of years.

Shostak is confident that, as telescope technology keeps improving, Seti will find an ET signal within the next two decades. "We will have looked at another million star systems in two dozen years. If this is going to work, it will work soon."

And what happens if and when we detect a signal? "My strenuous advice will be that the coordinates of the transmitting entity should be kept confidential, until the world community has had a chance to evaluate what it's dealing with," Davies told the Guardian recently. "We don't want anybody just turning a radio telescope on the sky and sending their own messages to the source."

But his colleague, Shostak, says we should have no such concerns. "You'll have told the astronomical community – that's thousands of people. Are you going to ask them all not to tell anybody where you're pointing your antenna? There's no way you could do that.

"And anyway, why wouldn't you tell them where [the alien life form] is? Are you afraid people will broadcast their own message? They might do that but, remember, The Gong Show has already been broadcast for years." And, for that matter, the Beatles.

Text B Aliens may destroy humanity to protect other civilisations, say scientists

Rising greenhouse emissions could tip off aliens that we are a rapidly expanding threat, warns a report.

By IAN SAMPLE, science correspondent, the Guardian, August 18, 2011

It may not rank as the most compelling reason to curb greenhouse gases, but reducing our emissions might just save humanity from a pre-emptive alien attack, scientists claim.

Watching from afar, extraterrestrial beings might view changes in Earth's atmosphere as symptomatic of a civilisation growing out of control – and take drastic action to keep us from becoming a more serious threat, the researchers explain.

This highly speculative scenario is one of several described by a Nasa-affiliated scientist and colleagues at Pennsylvania State University that, while considered unlikely, they say could play out were humans and alien lifeto make contact at some point in the future.

Shawn Domagal-Goldmanof Nasa's Planetary Science Division and his colleagues compiled a list of plausible outcomes that could unfold in the aftermath of a close encounter, to help humanity "prepare for actual contact".

In their report, Would Contact with Extraterrestrials Benefit or Harm Humanity? A Scenario Analysis, the researchers divide alien contacts into three broad categories: beneficial, neutral or harmful.

Beneficial encounters ranged from the mere detection of extraterrestrial intelligence (ETI), for example through the interception of alien broadcasts, to contact with cooperative organisms that help us advance our knowledge and solve global problems such as hunger, poverty and disease.

Another beneficial outcome the authors entertain sees humanity triumph over a more powerful alien aggressor, or even being saved by a second group of ETs. "In these scenarios, humanity benefits not only from the major moral victory of having defeated a daunting rival, but also from the opportunity to reverse-engineer ETI technology," the authors write.

Other kinds of close encounter may be less rewarding and leave much of human society feeling indifferent towards alien life. The extraterrestrials may be too different from us to communicate with usefully. They might invite humanity to join the "Galactic Club" only for the entry requirements to be too bureaucratic and tedious for humans to bother with. They could even become a nuisance, like the stranded, prawn-like creatures that are kept in a refugee camp in the 2009 South African movie,’ District 9’, the report explains.

The most unappealing outcomes would arise if extraterrestrials caused harm to humanity, even if by accident. While aliens may arrive to eat, enslave or attack us, the report adds that people might also suffer from being physically crushed or by contracting diseases carried by the visitors. In especially unfortunate incidents, humanity could be wiped out when a more advanced civilisation accidentally unleashes an unfriendly artificial intelligence, or performs a catastrophic physics experiment that renders a portion of the galaxy uninhabitable.

To bolster humanity's chances of survival, the researchers call for caution in sending signals into space, and in particular warn against broadcasting information about our biological make-up, which could be used to manufacture weapons that target humans. Instead, any contact with ETs should be limited to mathematical discourse "until we have a better idea of the type of ETI we are dealing with."

The authors warn that extraterrestrials may be wary of civilisations that expand very rapidly, as these may be prone to destroy other life as they grow, just as humans have pushed species to extinction on Earth. In the most extreme scenario, aliens might choose to destroy humanity to protect other civilisations.

"A preemptive strike would be particularly likely in the early phases of our expansion because a civilisation may become increasingly difficult to destroy as it continues to expand. Humanity may just now be entering the period in which its rapid civilisational expansion could be detected by an ETI because our expansion is changing the composition of the Earth's atmosphere, via greenhouse gas emissions," the report states.

"Green" aliens might object to the environmental damage humans have caused on Earth and wipe us out to save the planet. "These scenarios give us reason to limit our growth and reduce our impact on global ecosystems. It would be particularly important for us to limit our emissions of greenhouse gases, since atmospheric composition can be observed from other planets," the authors write.

Even if we never make contact with extraterrestrials, the report argues that considering the potential scenarios may help to plot the future path of human civilisation, avoid collapse and achieve long-term survival.

Text C We need to talk about aliens

The more we consider the possible consequences of contact with an alien intelligence, the better prepared we will be.

By ALAN PENNY, the Guardian, August 22, 2011

“No one would have believed in the last years of the nineteenth century that this world was being watched keenly and closely by intelligences greater than man's."

So starts H.G Wells's 1898 novel The War of the Worlds, which continues with a military invasion by Martians. While contact with aliens may be a common theme in science fiction, could it also be a serious topic in science?

Indeed it could. Ever since 1960 with the first serious search for radio transmissions from other civilisations (known as SETI, the Search for Extraterrestrial Intelligence), scientists have been thinking about what would happen if evidence for ET were found. Examples of their efforts include the 2010 Royal Society conference on "The detection of extra-terrestrial life and the consequences for science and society".

Last week the Guardian reportedona recent paper led by Seth Baum of Pennsylvania State University on this topic, categorising some of the possible consequences – ranging from beneficial through neutral to harmful.

So what's the point? We have never seen these Little Green Men, so why expend effort thinking about what might happen?

Scientists have already had to face this problem in real life. An early occasion was in 1967 when astronomers at Cambridge University using a new radio telescope detected regular blips coming from deep space. They were puzzled because no known source should do that. One possible explanation was ET and the director of the group, Nobel prizewinner Sir Martin Ryle, suggested that they should keep quiet about their discovery and dismantle the telescope, because if it was ET then sooner or later someone on Earth would start signalling back, alerting a possibly evil-minded alien intelligence to our existence.

Fortunately, they soon concluded that it was a natural source – they had in fact discovered pulsars. But there is a continuing controversy in the SETI community about whether it is wise to try and contact ET by sending out messages. For example, the main SETI searchers have agreed a protocol for how to spread the news if and when they discover ET, but have not yet been able to agree a common position on the wisdom of sending out messages.

The main problem is the nature of ETs. What are they like? To be able to influence us, they must be more advanced than us, so will they be wise and benevolent, since otherwise they would have destroyed themselves by now? Or perhaps as a result of a Hobbesian all-against-all struggle the only ET now out there has become dominant by destroying any potential competitors. But even if they were evil would they be able to get at us given the vast distances between the stars?

And it goes wider. Is it wise even to use our radio telescopes to try and detect ET? In 1962 the famous astronomer Fred Hoyleand John Elliot dramatised the risk in a TV series "A for Andromeda" starring Julie Christie. A message from ET was detected which turned out to contain instructions for building a computer. After this was assembled it set about destroying the human race, before being thwarted by the scientist hero.

Considering dangers like that, and applying the precautionary principle, should we shut down all our SETI searches?

Can we tell anything about ET that would guide us, first of all in deciding whether to search at all, then in matching our searches to its nature, and finally in whether to send out signals? My own position, as I argued in a paper presented at the Royal Society Kavli Centre last year, is that our total ignorance about the nature of ET means that we cannot say whether listening or talking is good or bad.

For example, sending a message may cause an evil ET to come and destroy us. Alternatively it may preserve us from destruction by an ET that has become aware of us from seeing our cities and is worried by the aggressive nature of new civilisations, but would be reassured by the peaceful content of a message.

We cannot tell which of the many possible benefits and dangers are more likely, and so we SETI folk can go about our business without reproach. But the more thinking, such as the Baum paper, we do about possible outcomes, the better prepared we may be for the actual outcome after the day of discovery, if and when it ever comes.

It may be good to do this, but is it worth spending real money on? Well, in fact very little money is spent on SETI. There are probably about the equivalent of 20 full-time people worldwide working on SETI, most funded from private sources, together with a little money from individual universities, supplemented with a very small amount from governments. And like all high-tech work it has spinoffs, most noticeably the Berkeley BOINC distributed computing systemwhich started asSeti@home, but is now used widely from biotechnology to meteorology. SETI is used as part of university teaching in the sciences, and it provokes thinking in allied sciences from sociology to linguistics.

Regardless of the chances of success, SETI is of real value. But here in the UK, practically no private or government money goes into it. With around 0.5% of the government funds that now go into astronomy(the 1-in-200 effort, I call it) the UK could make a big splash in the Seti world.

Alan Penny is an honorary reader in the School of Physics and Astronomy at the University of St Andrews, using the Lofar telescope to search for low-frequency radio signals from ET