00:00Will we one day find intelligent life beyond our planet?
00:06Although we've been searching for decades,
00:09we've never found convincing evidence of extraterrestrial neighbors in our galaxy, the Milky Way.
00:15No signals clearly made by other advanced civilizations.
00:20But there's a famous formula for calculating how many might be out there.
00:25Drake's equation is named after the researcher who came up with it in 1961.
00:33Theoretically, it could give us the number of civilizations in the Milky Way advanced enough to broadcast signals we can
00:41detect.
00:41In it, seven variables play roles. Let's take a look.
00:48First, we need the rate at which stars develop.
00:51We can estimate that. On average, fewer than ten new stars form every year in our Milky Way.
01:00Second, we need the fraction of those stars that end up having planetary systems, like ours does.
01:06New observations indicate lots of them do.
01:11And then we need the number of planets with the right environment in those systems.
01:16planets in the stars' habitable zone.
01:19According to estimates, only about 20% have at least one planet temperate enough for liquid water,
01:26an important ingredient for supporting life as we know it.
01:31Then things get trickier.
01:33There's no data on the next variables. We just have to guess.
01:38Of those potentially habitable planets, we need the fraction where life actually appears.
01:46And then the fraction where these life forms would evolve intelligence.
01:50And it doesn't stop there.
01:52Next, we would need the fraction of those intelligent life forms that communicate using signals that we can actually detect.
02:02Finally, there's the time factor.
02:04How long a theoretical civilization broadcasts such signals.
02:09They can only move at the speed of light, and the Milky Way is really big.
02:14So the timing would also have to be just right for us to detect them.
02:20Because the Drake equation includes so many variables where we just have to guess,
02:24it's more of a thought experiment than a real tool for calculation.
02:31Depending on how positive you feel about the chances of intelligent aliens when plugging in the numbers,
02:38it can predict thousands of civilizations, or just the one we know about, here on Earth.
02:44the boiling source.
02:45theazioni on planetaria
02:47and the臓
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