Actually, they probably don’t either. Or, more accurately, if they do know they probably can’t get to us.
Ever since humankind has figured out what the heavens are, there have been those who have looked up at the sky and wondered if we are alone. The truth is, not too long ago the idea that our Solar System was inhabited not only by life, but by intelligent civilizations. was not ridiculous fantasy, but the object of speculation. This idea was perpetuated by science fiction, most notably H.G. Wells and his famous book turned radio play War of the Worlds. Through little advertising and a convincing, news cast approach to the story, H.G. Wells was able to, accidentally, convince thousands of people that the earth was under attack from a hyper-intelligent martians, leading to a considerable amount of panic. Since the 1970’s however, specifically the Viking missions, we have known that Mars is actually quite lifeless and barren. This of course, did not quench our thirst for knowledge, did it damage the egos of those who continued to look for life.
According the Kepler Space telescope, the premier planet telescope, 1 in 5 stars in the universe are orbited by a potentially habitable, earth size planet. What does this mean for chances of life outside our precious solar system. It means that it’s not only very likely, but would be almost impossible to have not occurred already. It is estimated that amount of stars in the universe are on the order of 10^24, which is a 1 with 24 zeros following. If 1 and 5 of these has a potentially habitable planet, the idea that we are the only planet similar to ours that could harbor self replicating matter is not only ridiculous, but frankly insulting to someones intelligence. We cannot say with certain, of course, what the probability of life existing around a habitable planet is, because we have never found it, but most would agree that this fact is a limitation of current technology, and does not speak to the abundance of life in the universe.
The first exoplanet was discovered in 1994, which means that I am older than the simple fact that planets exist outside of our solar system. Since then, many milestones in exoplanet research have been achieved. Initially, we could only detect planets much larger Jupiter, which is over 300 more times as massive then the earth. It wasn’t until 2010 that we were able to directly image an exoplanet, and these are still the kind of planets that make Jupiter look like a shrimp. Couple this with the fact that the Kepler Space Telescope looks at only a tiny portion of the sky and you realize how incredibly hard it is to detect life.
Finally, we can only look up at the observable universe. This may seem initially quite obvious, but think of this: We see only the light from stars, planets and gas that are close enough to us that light has reached us since the beginning of the universe. The further we look away, the further back in time we peer, and the less like the current universe that part of the universe appears. The truth is, there is another universe out there, unobservable or much more evolved than we see it, each galaxy containing billions of stars, approximately 1/5 of which has a planet similar to ours. Chances are, there are millions, if not billions of alien civilizations looking up at their own sky, with their unique constellations and their owns moons and suns, wondering where we are. But the truth is, they are quite far away, and even if they could find us, they probably won’t be able to get to us.
Does this mean that we should stop looking? Absolutely not. The thing about human curiosity is that it has no bounds. And the search for earth-like planets, like many other searches, yields results other than its primary objective. From combing the data of Kepler we know have thousands of confirmed planets, and even more planet candidates. Each of these has it’s own data regarding its mass, orbit, potential composition and its stars mass. All of this data means we are now able to say things about planets that we were never to be able to say before, and ultimately that’s what its all about. The whole point of this thing called life, wherever it resides in the universe, is the pursuit of the knowledge. So the next time someone asks you what we are spending all this money on, tell them knowledge, and walk away.
Links: http://www.space.com/8680-direct-photo-alien-planet-finally-confirmed.html
http://planetquest.jpl.nasa.gov/page/history
http://home.web.cern.ch/about/updates/2014/04/cern-switch-comic-sans
