Are intergalactic lolcats in our future? SETI Founder Frank Drake thinks it's possible. Recently Drake said that alien civilizations may have created an intergalactic internet using an aspect of general relativity called gravitational lensing. How would that work?
Gravitational lensing is the effect where massive objects (such as stars) can bend the light of a background object. Say for instance a distant planet full of intelligent life is sending electromagnetic signals of their presence. Now if on the way to Earth, these signals happen to come across a foreground star or other large object, it is possible for that signal to be bent around the star thanks to the star's gravitational field, thus magnifying the signal. This ‘brightening' of the signal is wholly dependent on the mass of the foreground ‘lens' star as well as the relative motion of the source.
The cause of gravitational lensing inevitably lies in Einstein's General Theory of Relativity. In his theory, Einstein says that massive objects can cause a ‘bending' of space time. Because light always follows the shortest path, it too must follow these bends in space time, hence causing light from distant background objects that wouldn't necessarily reach us being ‘focused' onto the Earth and causing us to observe a stronger signal than we would otherwise. In fact, it was gravitational lensing being observed by Sir Arthur Eddington in 1919 during a solar eclipse that was the first proof of General Relativity being true.
For astronomers, gravitational lensing has many uses, from mapping the Universe's dark matter to discovering extrasolar planets. Drake, however, hopes to use the Sun as a ‘giant magnifying glass' by positioning a satellite observatory about 500 AU (46.4 billion miles). As well as magnifying any signals sent from these planets, Drake says that it would be theoretically possible to even see the planet's continents and oceans!
Now this all may sound too good to be true, and to an extent it is. With current propulsion technologies it would take us hundreds of years to reach this distance and add our node to this galactic internet. But Drake proposes that intelligent civilizations could have been transmitting these signals for billions of years and are just "waiting for us to log on."
If you'd like to read more about this, Italian Astrophysicist Claudio Maccone has written a textbook on the topic published by Springer-Praxis Books.