Q: Why haven’t we discovered Earth-like planets yet?

http://www.askamathematician.com/2012/05/q-why-havent-we-discovered-earth-like-planets-yet/

Finding an Earth-like planet will require a lot of patience and more powerful telescopes and telescope arrays, but that’s just an engineering problem. It’s just a matter of time (and probably not even that much!). Once found, the next challenge will be to determine whether or not the newly found tiny-as-Earth planets are covered in plants and critters. Already there are some ideas being floated that involve analyzing the atmosphere of the exoplanet to find signs of life (specifically, water vapor and oxygen). As impossible as that sounds, considering that we can’t actually take pictures of exoplanets (and again, every time you look at a star you can’t do better than a point of light) we’ve actually managed to do it a few times! Unfortunately, the first atmospheres we’ve seen were only visible because they were forming huge “comet tails” by being blown off of the surface of “hot-Jupiters” orbiting practically within high-fiving distance of their host stars. So, not Earth-like, but it is a step in the right direction.

Chances are, we’ll find an Earth-sized planet inside of the goldilocks zone of another solar system, and be able to determine if there’s life on it or not, within the next few decades. Copernicus would crap himself with joy if he were alive today.