If we're going to have any chance of sending stuff to other star systems, we need to be laser-focused on becoming a multi-planet civilisation.
It now appears that essentially every star has a planetary system. In the very beginning, we thought at best half.
The bottom line is, like, one in five stars has at least one planet where life might spring up. That's a fantastically large percentage. That means in our galaxy, there's on the order of tens of billions of Earth-like worlds.
Estimates are that at least 70 per cent of all stars are accompanied by planets, and since the latter can occur in systems rather than as individuals (think of our own solar system), the number of planets in the Milky Way galaxy is of order one trillion.
This plucky NASA telescope is able to find planets en masse. If you compare planet hunting to prospecting for gold, then Kepler is equivalent to trading in your trusty pan for a diesel-powered sluice box.
It's hard for us to really understand the immensity so far of the conquest of space.
There's planets, life in the universe. You don't talk about that in high school - or maybe I skipped class that day.
For me, the distant future and far-off galaxies is where it's at. That's where my imagination can really come out to play.
It bears mentioning that the Milky Way is only one of 150 billion galaxies visible to our telescopes - and each of these will have its own complement of planets.
Let me mention that not all sun-like stars host planets - perhaps about 30% of them are planet-builders. It's not so easy to form a planet!
I am undecided whether or not the Milky Way is but one of countless others all of which form an entire system. Perhaps the light from these infinitely distant galaxies is so faint that we cannot see them.
According to recent studies, at least one star out of three is multiple.
As chief scientist, it's sort of my job to look at bridges between what we do and to see the connections. But when we try to understand how are planets around other stars habitable... to looking back at the Earth - how are the changes that are taking place, how are they going to affect humanity?
