Not that long ago, we had no idea whether there were planets around other stars besides our own. Then in 2009, the
Kepler telescope was deployed to look at one patch of the galaxy (150,000+ stars) and search for planets around those stars.
We found some. 4,175 planet candidates and 1,018 confirmed planets, so far. That changes almost weekly. If you'd like to learn how they figured that out just using a telescope, the story of how they find planets can be read
here.
Believe it or not, we already predicted that there would be other planets because of the way we have theorized the manner with which our own solar system has evolved. But until this past decade, we had no proof. Now we have it.
OK, so we've established that there are other planets besides the ones we know about around our own sun. But what we really are interested in, are the planets in the 'Goldilocks zone'. In other words, planets, like our our earth, that are the right distance from their star, that water could be in a liquid state, and therefore make possible the conditions for life as we know it.
And, yes, we found those too. So far, we've found eight of them. This didn't come as a surprise either, but again, now we have proof. Based on that proof, combined with the Titius-Bode relationship formula, which predicted our own Uranus before we had proof it existed, we are now able to extrapolate that there are earth-like planets in 10-20% (minimum) of all the stars in the universe. That means hundreds of billions of earth-like planets in the Milky Way galaxy alone.
All of this of course leads to the big question - if there are a lot of other planets like Earth, are there other civilizations too?
Before we try to answer this question, we have to figure out how long it takes for a planet to form, create life, if life is possible, and evolve life to a form that can learn how to voyage into space.
The universe is calculated to be around 13.8 billion years old. Our sun came along 4.5 billion years ago - the universe was already 9.3 billion years old at the time. It took our own planet 4 billion years before major life forms started appearing and archaic homo sapiens only came around 400,000 years ago. This means that our presence on the earth only accounts for 1/1,000th of the time it was around.
Until just recently, we only expected that relatively new suns would have planets. We never expected that there would have been planets around stars that formed when the universe was young. But we just found evidence of five planets around an eleven billion year old star - a star that was born when the universe was only 2.8 billion years old. Remember, it's 13.8 billion now. When the Sun and Earth formed, these planets were already older than the Sun and Earth are now.
This changes everything. Until now, we weren't sure how old planets could be. We've never found Earth-sized planets this old. OK. Where are the aliens? Even with the vast distances between stars and limiting your ships to far less than the speed of light, you can colonize the entire galaxy in just a few million years. That's far less than the age of the galaxy.
Ancient alien civilization(s) could have planted their flags on every habitable planet in the Milky Way by now. Maybe every civilization advanced enough went through the cycle of advancement and died out already. Maybe they’re out there, but so advanced we don't even recognize them.
Food for thought. But with all of the new data, NASA is now officially saying that we cannot possibly be alone in the universe. With hundreds of billions of earth-like planets out there, just in our own galaxy, I'm inclined to agree. I just hope we get to meet one and with luck on our side, they don't want to conquer us.
