Shoot Aggressive Aliens With Lasers to Defend Earth

The fate of humanity if aliens were to discover Earth with its balmy climate and bountiful resources, has long been a concern for scientists-many of whom fear the worst.

Physicist Stephen Hawking is among those to have warned that ET and his friends may be much more intelligent than us, and may view human beings as little more than troublesome bugs.

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Now a duo of astronomers from Columbia University in New York have proposed an innovative method to hide our planet from prying extraterrestrial eyes-using massive lasers.

And it's not a joke, they say.

Alien scientists, argued David Kipping and Alex Teachey, may be trying to find habitable planets using the same technique we do-searching for a slight dip in light when a planet "transits" between the star it orbits and the telescopes watching it.

Planets do not emit their own light and, if they were visible to the naked eye, would appear as dark dots tracking across their bright stars.

But these exoplanets are too far away to see, and all our telescopes can pick up is a small decrease in the starlight emitted during transit.

If aliens spot us using this technique, Earth would be a logical target for alien settlement.

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It orbits within the so-called "habitable zone"-not too close nor too far from the Sun-where the temperature is right for liquid water, the essence of life.

In a paper published Thursday in the Monthly Notices of the Royal Astronomical Society (RAS) in London, Kipping and Teachey said Earth's Sun transits could be masked by shining huge lasers to cover the dip in light.

Strange But True "Despite the timing, it's really not an April Fool's joke," RAS deputy executive director Robert Massey assured AFP on Friday.

"This is a serious piece of work."

Humanity's search for a planet capable of hosting life remains an academic pursuit-there is no solar system near enough to reach without time travel.

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Since its launch in 2009, NASA's Kepler exoplanet-hunting space telescope has found thousands of candidates.

Astronomers have verified the existence of nearly 2,000 faraway worlds, but most of those orbiting in habitable zones have been gas giants.

"The transit method is presently the most successful planet discovery and characterization tool at our disposal," wrote the duo.

"Other advanced civilizations would surely be aware of this technique..."

Within the wavelength spectrum of visible light, the transit signal could be masked with a monochromatic laser emitting about 30 million watts (MW) for 10 hours at a time, once a year.

One MW can power several hundred homes for an hour.

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A universal cloak effective at all wavelengths, would require a much larger array of lasers with a total output of 250 MW, said the team.

"There is an ongoing debate as to whether we should advertise ourselves or hide from advanced civilizations potentially living on planets elsewhere in the Galaxy," Kipping said in a statement.

"Our work offers humanity a choice, at least for transit events, and we should think about what we want to do."

This artist's impression shows the planned 39-meter European Extremely Large Telescope (E-ELT) using a sophisticated adaptive optics laser system to correct for atmospheric turbulence. A vastly more powerful laser system would be needed to hide the Earth from aliens, however.

Nov. 8, 2011 --

Despite the occasional report of an extraterrestrial sighting, be it through a microscope revealing curious shapes in a meteorite or a photo of wispy lights taken at the blurry end of a camera lens, aliens have yet to make contact with humans. Even the White House yesterday put out a statement declaring that the federal government "has no evidence that any life exists outside our planet, or that an extraterrestrial presence has contacted or engaged any member of the human race." Humans may not yet have encountered life outside of our planet, but many scientists see it as an inevitability. In 1960, astronomer Frank Drake came up with the now eponymous equation which provided an estimate of the number of civilizations in our galaxy. Although scientists continue to debate the application of his formula as well as alternatives, Drake's own solution to the equation is 10,000 civilizations, suggesting intelligent, technologically advanced life outside our planet is common. How these different civilizations, including our own, find each other is an important question for anyone here on Earth looking for extraterrestrials. Explore how aliens might stumble upon our planet -- and how we might actually spot them first.

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Before we can began to search the skies, we have to start by narrowing down our options. Sticking within our own galaxy is a good start, since we're more likely to spot a neighbor closer to us than one further away. Astronomers may also elect to focus their attention on stars closer to the center of the Milky Way, where 90 percent of its stars are clustered. Furthermore, the stars here are a billion times older than the sun, giving life more time to develop biologically and technologically. Many stars are unsuitable for nurturing life, and even stars that do have the appropriate "spectral type" may host exoplanets inhospitable to life due to their location relative to their parent star, size or composition. These criteria would not only help us find aliens, but also help them find us. After all, Earth would stand out as a hospitable planet, according to a paper published in 2007 in Astrophysical Journal.

If aliens are looking for us, they're scanning the same, vast, dark and mostly empty expanse of space that we are. It's a good thing then that we're leaving the lights on to make it easier to find us. According to Abraham Loeb, of Harvard University and Edwin Turner, from Princeton University, by scanning the skies for artificial illumination as opposed to naturally occurring light sources, both human and extraterrestrial astronomers might be able to find signs of life. Existing telescopes would be able to see a city the size of Tokyo as far as the edges of our solar system.

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For more than 25 years, the SETI Institute has been scouring the skies for signs of alien life. However, long before the institute was established, scientists have tried to catch a communication signal from another world. Scientists looking for alien signals use a combination of optical and radio telescopes, such as the one seen here. Dropping in on a signal without knowing the source of the communication is the tricky part, however, and researchers narrow down their search by targeting specific kinds of stars. With their citizen science program, SETI@home, the institute has enlisted three million additional observers analyzing data for traces of an alien signal.

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Have aliens already stopped by for a visit, even though we weren't at the door to meet them? If they have, shouldn't they have left something behind? An artificial object of alien origin could be lurking in our solar system without our knowledge. As Discovery News' Ray Villard explains: "In a paper published in the 1960s, Carl Sagan, using the Drake Equation, statistically estimated that Earth might be visited every few tens of thousands of years by an extraterrestrial civilization." Further out beyond our solar system, aliens may have left what essentially amount to interstellar billboards large enough to be seen by, say, a planet-hunting telescope like Kepler. These last two scenarios, of course, envision an extremely technologically advanced civilization well beyond the engineering capabilities of humankind. At the same time, humans have sent spacecraft beyond the solar system, including Pioneer 10 and 11 as well as Voyager 1 and 2. All of these spacecraft are equipped with what are essentially calling cards for the human race -- small plaques in the case of the Pioneer spacecraft and golden records for the Voyager spacecraft (seen here).

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Humans may rely primarily on fossil fuels as their primary means of energy, but that doesn't mean extraterrestrials in a far off civilization have the same power source. Solar power could be one option, though not quite with the same black panels we use on Earth. A super civilization could even tap into a black hole to meet its energy needs. If aliens are tapping to these cosmic bodies, that should make them all the more detectable from Earth. How would we know whether an alien race was relying on a black hole as a source of energy? As Discovery News' Ray Villard explains: "Tell-tale evidence would come from measurements that showed the black hole weighed less than 3.5 solar masses. That's the minimum mass for crushing matter into a black hole via a supernova core-collapse."

In one of the most unusual -- and highly unlikely -- first-contact scenarios, aliens would be able to recognize us by the level of greenhouse gas emissions we pump into our atmosphere. Not only that, according to a hypothesis put forward by researchers affiliated with NASA and Pennsylvania State University (though not directly tied with either institution), but aliens may use that as cause to wipe out the human race. In this bizarre set of circumstance, aliens view human advancement as a destructive force spiraling out of control. To avoid the threat of a future adversary, extraterrestrials clear out the competition.

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