[enkid]

There are multiple areas of the Drake equation that we have either no or only one data point on:

- Number of planets that can support life that will develop life - Number of planets that have developed life that will develop intelligent life - Fraction of intelligent life that will develop the technology to transmit signals of their existence - The length of time that those signals will be sent

We only know anything about any of these processes on one planet. That means we are guessing when we put numbers to these factors. We don't know if these numbers are 1 in 100 or 1 in a trillion. That's what I mean by having intuition but not really having evidence.

[pfraze]

Sure, my counter is just that the Drake equation uses conservative probabilities on those questions. Even pessimistic answers to those questions turn into optimistic projections given the scale of the universe.

We’re obviously discussing a bunch of unknowns, but my intuition was actually more pessimistic until I saw what the Drake equation observed

[ladberg]

The problem is that we don't know if the "conservative probabilities" are actually conservative. There is only a single planet in the Goldilocks zone that we for sure contains or doesn't contain life.

Imagine if someone showed you a rock in the forest with some lichen in weird pattern and asked you for a "conservative estimate" for how many other rocks on Earth had that same pattern. Maybe pattern is common, but maybe it's something incredibly unique that no other rock has. Because you can't ever look at a different rock, there is no reasonable answer.

[SanderNL]

If you ask a layperson, yes sure. Ask a geologist/biologist/whatever. There is order in the chaos. Some things can be said with certain levels of confidence without (direct) evidence. There are patterns you know.

[enkid]

This is actually one of those things experts are very bad at. Experts make good predictions when they have feedback about those predictions. There is no feedback about this kind of prediction, so experts would be very bad.

[cobbzilla]

> Even pessimistic answers to those questions turn into optimistic projections given the scale of the universe.

I used to believe this too, but the universe is not actually that big -- taking some not-so-conservative estimates, let's say there are a trillion galaxies, each with a trillion stars.

If a couple of the terms in the Drake equation turn out to be 1-in-a-trillion, the odds of finding intelligent life no longer look so good.