The Milky Way alone has about 2.5 × 10^11 stars. The Andromeda Galaxy has around 10^12. Let's take 0.5 × 10^12 stars on average per galaxy.
There are about 2.5 × 10^11 galaxies in the observable universe.
This gives us around 10^23 stars in the universe to fiddle with. Assume every star has an average of 2 planets; some have more, some have none.
This is a pretty large number to trim down.
I'd argue the Drake equation is excessively conservative. Note that when microbial life first emerged on Earth 4.1 billion years ago, the Earth's atmosphere was rather reducing, and the Sun was around 30% less luminous than it is today. There was free water, but no free oxygen, and an extremely high-pressure CO2 atmosphere.
The universe is arguably extremely young; the longest-lasting stars will only burn out around 10^13 years from now, and the universe is barely 10^10 years old. It's fair to say that many sun-like stars haven't even formed yet.
There are about 2.5 × 10^11 galaxies in the observable universe.
This gives us around 10^23 stars in the universe to fiddle with. Assume every star has an average of 2 planets; some have more, some have none.
This is a pretty large number to trim down.
I'd argue the Drake equation is excessively conservative. Note that when microbial life first emerged on Earth 4.1 billion years ago, the Earth's atmosphere was rather reducing, and the Sun was around 30% less luminous than it is today. There was free water, but no free oxygen, and an extremely high-pressure CO2 atmosphere.
The universe is arguably extremely young; the longest-lasting stars will only burn out around 10^13 years from now, and the universe is barely 10^10 years old. It's fair to say that many sun-like stars haven't even formed yet.