axeil posted:

As preposterous and geocentric as it sounds on its face, the evidence for "We're First" does appear quite good despite the overall age of the Universe.

To clarify, the "We're First" answer basically says that no, habitable planets and intelligent life are not that rare, however conditions only recently became such that intelligent life can form. Its a somewhat unsatisfying answer as it seems highly unlikely we're "special" but there is fairly decent evidence for it.

Here's an article going through the details of the Firstborn solution in a bit more depth: https://www.universetoday.com/147591/beyond-fermis-paradox-x-the-firstborn-hypothesis/


In no particular order the conditions you need for intelligent, biological life are:

1) Stellar formation in the right type (main sequence, sun-like stars, which are rarer than you think)
2) Sufficient quantity of higher numbered elements to form planets
3) Low number of cataclysmic, planet sterilizing effects (supernovae, gamma ray bursts, black holes, etc.)
4) Sufficient quantity of phosphorus. Until recently this wasn't seen as something that interesting but it does appear that phosphorus is much rarer in the universe at large than it is on our planet/in our solar system
5) Sufficient quantity of some kind of solvent for life (e.g. water)

This is a pretty long list and that's before we get to the habitable zone, tidal effects, etc.

I don't recall the exact figures but I believe they've determined that given these constrains the Earth was formed right at the start of the period in which all 5 of these criteria could generally be met.