Earth, a surprisingly difficult planet to live on

Earth may be our very life sustaining home, but when looked at from an outsider’s point-of-view it can be a very inhospitable planet.

This is especially so when you begin to assess the chances of survival of a humanoid clone – (referred to here as a “meat probe”) from elsewhere in the universe – being plonked somewhere on Earth, and given the task of staying alive for 24 hours.

So here’s the upshot: of the 4.6 Gy [Gy or gigayears, being 1,000,000,000 years] of Earth’s known history, there’s only been enough oxygen in the atmosphere for us to survive for about 0.5 Gy. For roughly 90% of the Earth’s history we couldn’t even breathe the air. And about 10-25% of the time, there have been ice ages so savagely fierce that the glaciers reached the tropics: odds are good that any meat probe landing on solid ground during these periods would rapidly die of exposure. So historically, Earth has only been inhabitable about 8% of the time – assuming you are lucky enough to find some solid ground. Once you factor in the random surface distribution, we’re down to about 2% survivability.