Extraterrestrial

Can we mask the Earth from hostile aliens ?

By T.K. Randall
April 2, 2016

Image: Laser Meets Lightning
Credit: ESO/M. Kornmesser / CC BY-SA 3.0 (adapted) The hunt for extrasolar planets has been going from strength to strength in recent years with astronomers having so far identified more than 2,000 of them in orbit around distant stars.

We are able to detect the presence of these far-off worlds by looking out for the tell-tale dimming that occurs when a planet passes in front of its star, a technique that should in theory enable an extraterrestrial civilization to detect our planet as well if they happen to be looking in our direction.

But what if, for some reason, we didn't actually want to be found ?In a recent study, Professor David Kipping and graduate student Alex Teachey from Columbia University determined that it would be possible to mask the Earth from being detected while it is passing in front of the sun by firing lasers out in to space.

The pair calculated that it would be necessary to shine a 30 MW laser for 10 hours straight, once a year to hide all the visible light from the Earth and a 250 MW laser to hide all wavelengths.

"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. "To another civilization, this should make the Earth appear as if life never took hold."

Source: Washington Post

Tags: Extraterrestrial, Planet