TEDtalks SETI Part 2 The speaker also mentioned the possibility, if not the probability of the existence of Extra Terrestrial Intelligence. Our sun is one of 400 billion stars in our galaxy, and there are more than 100 billion galaxies in the universe. It is quite common for a star to have planets. And some of these planets are not neither too small nor too big, not neither too close nor too far from their stars, which make them as inhabitable as our planet namely the Earth is. There could be more inhabitable planets in the universe than all the sands on the earth sum up. So I could say there is quite a great chance (maybe 99.99%?) that there are or were civilizations out there, in the deep space. Maybe some of them are also looking up at the night sky, at the same stars, from the opposite side, asking and answering similar questions as we do. Another interesting thing is that they are actually examining the past of those stars. Stars are so far away from us, the nearest star is 4.2 light years away, the nearest galaxy is 2.5 million light years away. The signal they get is just a snapshot about what they were a long time ago, maybe millions of years ago. Ultimately what determines the success or failure of SETI is the longevity of technologies. If technologies don’t last and persist, like a shooting star, it would be very hard to detect them. SETI tells us about some other stars’ past, but a detection of positive sign tells us it’s possible that a civilization could last for a very long time. After all, comparing to the age of the universe, we, the human beings are just like a new-born infant merely on his first breath in the world. We are not sure about the nature of ourselves and whether our infinite stupidity would lead to our own extinction. So the profound influence SETI could deliver us is to reveal a little bit about our future. This is why SETI is bizarrely called “the archaeology of the future”.