Are we really alone in the universe? Since no one really knows for sure, a laser defense system can help conceal planet Earth from advancing alien civilizations, a new study proposed.

Many prominent scientists have long cautioned that intelligent life on other planets could be doing the same thing we are doing - looking for life outside our planet. One popular technique is by analyzing the light variations when a planet moves in front of a star it circles.

Using this technique, the Kepler mission already found more than 1,000 planets and many of them are similar to the Earth's size. The researchers theorized that alien civilizations could take a page from our books and locate our planet using the same technique.

Earth's location is right smack in the habitable zone of the sun, which renders it a promising new place for relocation. Several scientists are worried that the arrival of extraterrestrial life - if they do exist - could deplete the Earth of its resources.

Graduate student Alex Teachey and Professor David Kipping from Columbia University proposed of a laser defense system to conceal our planet from aliens. When the controlled laser is beamed directly at a potentially alien-populated star, it will make up for the dip in light.

The researchers said that a consistent emission of 30 MW laser for 10 hours once a year could mask the transit signal (dip in light) at least in visible light. The International Space Station gathers almost the same amount of energy every year. A chromatic cloak, which is effective in all wavelengths, requires a larger tunable laser array with 250 MW of total power.

"Alternatively, we could cloak only the atmospheric signatures associated with biological activity, such as oxygen, which is achievable with a peak laser power of just 160 kW per transit," said Teachey, who explained that it will make the Earth look lifeless to another civilization that might be searching for life in the vastness of space.

There is an ongoing debate as to whether it is wise for mankind to broadcast our existence to other potential forms of life in the galaxy. The proposal was detailed in the Monthly Notices of the Royal Astronomical Society journal on March 30.

Photo: Gilbert Parker | Flickr