For this question we have to assume that 100 light years away there is a planet much like earth, lets call it
Planet X, inhabited by humanoid's much the same as us, and at a similar technical advancement as us. Lets assume that they have developed the same technology as us in the form of Telescopes and Green Lasers.
Okay, Let me set the scene:
Here on Earth, Astronomers have just discoved Planet X and let the world know of the new discovery. Amatuer Astronomers all over the globe decide to have a look at Planet X and train their Telescopes with Green Laser Pointes onto it. Others use their pointers to show people where planet X is.
Fast Forward 100 Years
On Planet X, Vortag and his son Targ decide to get their Telescope out and look at Planet Alpha47 (Earth) that their Planets Astronomers have recently discovered.
Right, Now the Question! Would Vortag and Targ see flashes of green light coming from the surface of Alpha47?
I could probably have asked that in a much less longwinded fashion..
So if the Answer is yes, well that makes it dead easy, All we need to do, to find out if there is extra terrestrial life out there, is look for little green flashes!
