h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Surely this shouldn't run as a percentage - surely it should be average number of planets (and possibly significant moons?) round each star?

And then have fraction of planets (and moons) capable of supporting habitable life

As our satillites continue hunting we are running into the case that any system with planets will in fact have more than one

I would also think that a planet with intelligent life (though I do agree that defining that is hard) would have a higher percentage of communicating

Then Drake should also have added in one for how effectively they communicate - something like how many stars will be reached with an effective communication - even if you can't pass on that much information it must be recognisable as not caused by nature
- and how many stars our outpouring of energy will reach as a significant note is hard to know

I think the timing that the communicating species is around seems reasonable