Talk:Stephen Hawking: aliens 'almost certain to exist,' could invade Earth

Drake Equation
The bit about the Drake equation is under dispute by some astronomers who study extra-solar planets. Nearly all the planets discovered around other stars are known as "hot Jupiter's" : massive, Jupiter and larger size planets that orbit well within the orbit of Mercury in our solar system. Since the orbits of some of these hot Jupiter's are retrograde to their host star, it is quite likely that these planets formed further out in their solar systems and then migrated in, most likely destroying any small, rocky worlds which could lie within the "Goldielocks Zone" (the zone where liquid water is possible). Basically, imagine if Jupiter migrated in close to the sun over tens or hundreds of thousands of years - it would destroy Mars, Earth, Venus and Mercury.

This discovery, however, is of a limited sample size since current technology cannot resolve planets much smaller than hot Jupiter's and of those, not all have a retrograde orbit, however, it is becoming more common to see this in more and more star systems and could place serious doubt on the validity of the data used to calculate the Drake equation.

I don't think this is a deal breaker for this article, but it does not give a calculation over 100%.

EDIT : It's since been changed to "high probability" which does seem more appropriate.

Turtlestack (talk) 22:57, 25 April 2010 (UTC)
 * Heh. I didn't notice that. Thank you and Wikidsoup. --Diego Grez let's talk 22:58, 25 April 2010 (UTC)