Earth LASER defence!

Astronomers have proposed to shield Earth with a barrier of powerful lasers to make it invisible to aliens and keep it safe from a hostile invasions.

A new paper published by Columbia University researchers in the Monthly Notices of the Royal Astronomical Society turns the table on our obsession with looking for aliens, and advocates defending as well as hiding our planet from the eyes of potentially belligerent space-dwellers.

In order to make this a reality, the paper suggests the use of a planet-spotting technique called a "transit method" — keeping track of a star's dips in light, which are caused by planets passing between the star and our vantage point.

This method has been used to discover over 80 percent of new exoplanets over the last 10 years, and the authors of the study think alien civilizations are probably using it to look for us, too.

In order to avoid being detected, they propose cladding Earth in the same amount of light it blocks when passing in front of the Sun. 

While there are many different ways to achieve this, such as installing sprawling mirrors, the cheapest and most effective solution is to create a shield of powerful laser lights.

The system would be composed of three different structures. One, called a "broadband cloak" which is comprised of a single 30-megawatt laser that would only be activated when Earth is in its transit phase — for about 10 hours a year.

While the first cloak would conceal us in visible light, that is not enough. We would also need a second, laser-based array employing several, smaller sources emitting high-speed light. This 250 megawatts barrier, which the astronomers nicknamed "chromatic cloak" would make sure our planet is not visible for systems employing infrared or ultraviolet detectors.

A third system, called "biocloak" would hide any sign of life on the planet (like oxygen, nitrogen, etc.) by using a polarised 160-kilowatt laser power.

Source: sputnik