from Nathaniel Sharping at the blog of Discover Magazine:
A new study suggests that there are around 700 quintillion planets in the universe, but only one like Earth. It's a revelation that's both beautiful and terrifying at the same time.
Astrophysicist Erik Zackrisson from Uppsala University in Sweden arrived at this staggering figure-- a 7 followed by 20 zeros-- with the aid of a computer model that simulated the universe's evolution following the Big Bang. Zackrisson's model combined information about known exoplanets with our understanding of the early universe and the laws of physics to recreate the past 13.8 billion years.
Zackrisson found that Earth appears to have been dealt a fairly lucky hand. In a galaxy like the Milky Way, for example, most of the planets Zackrisson's model generated looked very different than Earth-- they were larger, older and very unlikely to support life. The study can be found on the preprint server arXiv, and has been submitted to The Astrophysical Journal.
The entire post can be read here.