There has been recent speculations and assumptions by more than a few scientists on the possibility of Earth-type planets being quite common in the universe. While this is most definitely enticing information it is not a revelation. It is, however, still just speculation.
With the deployment of the Keplar planet hound spacecraft last year we have taken a confident step down the right path to obtaining hard evidence to confirm these speculations. It will take time but already we're seeing the fruits of humanities labours. As time goes by we will collect more and more information and as technology improves so to will our ability to confirm or disprove said speculations.
Scientists suggest that one out of every four sun-like stars may have a planet similar in size to Earth in close orbit. These scientists focused on 33 known alien planets which orbit around 22 different stars and detected (but not confirmed) the presence of another 12 similar planets. Further to this 166 stars were then analyzed, resulting in estimates that 1.6% had Jupiter-sized planets in orbit and 12% had "super-Earths" (planets roughly 3-10 times the size of our own).
What does this mean? Essentially out of about 100 typical sun-like stars, one or two will have a planet the size of Jupiter, six will have a planet the size of Neptune, and up to twelve will have a super-Earth. It can then be extrapolated that about 23 out of every 100 will likely have an Earth sized planet. The Earth-sized planets can only be guessed at due to the fact we cannot yet detect planets of this size, they're just too small for our current technology.
If any of the numbers above are remotely accurate it bodes well for the human race to someday explore new worlds and possibly relieve some of the strain on our own planet due to over-population.
It is fairly ignorant to even consider the fact that we as a human race on the planet Earth are the only intelligent beings in existence. With this number of planets estimated to be in existence it is highly likely we're not alone. At the present time, however, we can only be satisfied with estimations and speculations. I for one am positive that the truth will come to the forefront before long and we'll soon have neighbours in this universe. Whether or not we'll be able to make contact remains to be seen.