The earliest evidence of life on Earth dates back more than four billion years, almost to the genesis of the planet. As far as the prospect of finding life on other planets, that's actually quite promising: It's probably happened more than once in our solar system.
But here's the thing: if there was life on Mars, it's not there now. If there was life on Venus, it's not there now. We're not just looking for extraterrestrial life: We're looking for sentient,intelligent extraterrestrial life.
We live on a perfect planet in a perfect orbit around a perfect sun. If our sun were a red dwarf star,like 85% of the stars in the galaxy, life would probably never have begun here, because red dwarves don't produce enough UV radiation to kick-start organic chemistry, and most of them are flare stars, prone to wild variations in luminosity and heat. If our sun suddenly got twice as hot and twice as bright and stayed that way for several hours, we'd be fucked. If it did that every couple of months, at completely random, unpredictable intervals, there would be no stable environment on any planet in the solar system.
If our sun were in a binary or trinary star system, like most of the stars in the galaxy are, then our orbit would be wobbly and uneven, which would also create an unstable climate and water cycle, and life would have trouble holding on. If the sun were a lot hotter and brighter than it is, an A-Type or B or O-Type star, then it would have gone nova along ago and we wouldn't be here.
If our solar system were closer to the center of the galaxy than it is, closer to a black hole or a gamma ray burster or a superluminous star, or even just in a denser stellar neighbourhood, then we probably wouldn't be here.
And then there's all the shit flying around. If we didn't have Jupiter in the outer solar system, with its huge gravity eating up all the rocks careening around that what to come crashing into us, we probably wouldn't be here. The likelihood of a planet the size of Jupiter forming around a star the size of our sun is about 1 in 26.
And yet, even here, on this perfect planet in its perfect orbit around a perfect star, in a relatively quiet corner of a relatively stable galaxy, it has still taken a third of the age of the universe for those first organisms to develop to the stage that we're at now, and there's no evidence that it happened earlier.
I'm not saying it's impossible for it to have happened anywhere else, but if it has, it's almost certainly so rare, and so far away, that we will never meet them. We are, for all practical purposes, alone. And we always will be.
Plus the sun is part of the first generation of stars formed with a protoplanetary disk metal-heavy enough for terrestrial worlds with sufficient heavy elements to support life to form. And if you take the "any interstellar alien life would eventually spread to all stars in the galaxy (and beyond)" as a given this puts a huge selection bias in place because any intelligent life to form must be among the firstborn because there will not be any latterborn because the firstborns will put a dyson sphere around their star before they can emerge.
The earliest evidence of life on Earth dates back more than four billion years, almost to the genesis of the planet. As far as the prospect of finding life on other planets, that's actually quite promising: It's probably happened more than once in our solar system.
But here's the thing: if there was life on Mars, it's not there now. If there was life on Venus, it's not there now. We're not just looking for extraterrestrial life: We're looking for sentient,intelligent extraterrestrial life.
We live on a perfect planet in a perfect orbit around a perfect sun. If our sun were a red dwarf star,like 85% of the stars in the galaxy, life would probably never have begun here, because red dwarves don't produce enough UV radiation to kick-start organic chemistry, and most of them are flare stars, prone to wild variations in luminosity and heat. If our sun suddenly got twice as hot and twice as bright and stayed that way for several hours, we'd be fucked. If it did that every couple of months, at completely random, unpredictable intervals, there would be no stable environment on any planet in the solar system.
If our sun were in a binary or trinary star system, like most of the stars in the galaxy are, then our orbit would be wobbly and uneven, which would also create an unstable climate and water cycle, and life would have trouble holding on. If the sun were a lot hotter and brighter than it is, an A-Type or B or O-Type star, then it would have gone nova along ago and we wouldn't be here.
If our solar system were closer to the center of the galaxy than it is, closer to a black hole or a gamma ray burster or a superluminous star, or even just in a denser stellar neighbourhood, then we probably wouldn't be here.
And then there's all the shit flying around. If we didn't have Jupiter in the outer solar system, with its huge gravity eating up all the rocks careening around that what to come crashing into us, we probably wouldn't be here. The likelihood of a planet the size of Jupiter forming around a star the size of our sun is about 1 in 26.
And yet, even here, on this perfect planet in its perfect orbit around a perfect star, in a relatively quiet corner of a relatively stable galaxy, it has still taken a third of the age of the universe for those first organisms to develop to the stage that we're at now, and there's no evidence that it happened earlier.
I'm not saying it's impossible for it to have happened anywhere else, but if it has, it's almost certainly so rare, and so far away, that we will never meet them. We are, for all practical purposes, alone. And we always will be.
I mean I’d be happy to find fossils on Mars. Unless we stumble across warp technology in my lifetime I’m gonna have to hope for that.
Plus the sun is part of the first generation of stars formed with a protoplanetary disk metal-heavy enough for terrestrial worlds with sufficient heavy elements to support life to form. And if you take the "any interstellar alien life would eventually spread to all stars in the galaxy (and beyond)" as a given this puts a huge selection bias in place because any intelligent life to form must be among the firstborn because there will not be any latterborn because the firstborns will put a dyson sphere around their star before they can emerge.
I don't buy the dyson sphere bullshit, btw. It's a giant pipe dream that fails on the simplest of observations.