If we're not alone, where are the aliens?

Space is infinitely large and infinitely expanding. There are billions of other solar systems similar to that of our own just within the Milky Way, with some being billions of years older then ours as well. There is no way that life doesn't exist elsewhere, but where is the evidence? This concept is known as the Fermi Paradox. It is essentially saying that there must be intelligent life out in space but there is no concrete evidence to prove it. No space probes, no left over artifacts, no signs of existence.

However, space is so incredibly large and ancient that there is a significant chance that we may be too late to contact aliens. Since there are so many star systems older than our own, intelligent life could have existed on another planet millions of years ago. If these civilizations did look for other life in our solar system, humans weren't around to receive the message. With this being said, it could be the opposite for us as well. Maybe we are too early and in a few million years there will be other intelligent life wondering where everyone else is in the universe.

One other point that the article makes, is that human image of aliens may not be accurate (green skin, big-headed humanoid). Therefore, if we do possibly find ourselves sitting with an alien, chances are that communication will be too difficult to where there is no point in trying to communicate at all.

All in all, where ever these possible other life forms are, there's no guarantee that we ever interact with them or even see concrete proof that they exist.