I was actually referring to Voyager’s statement that
which, unless I’m reading this very wrong (and I may be), suggests that other places are more likely to generate life than here.
Right.
But that’s not evidence it did happen, it’s evidence it could have happened “There is some evidence it could have occured here”.
I think it far more likely life originated here but I am not a scientist. It just seems like the jump across space is more improbable.
Why couldn’t God create life by abiogeenesis?
If it happened according to physical law, why assume god did it? If it would have happened anyway, what did god do exactly?
Because there’s no reason to think that God is even possible, much less real. That’s like asking “Why couldn’t time travelling fairies have done it with magic ?” Because there’s no evidence of fairies, and no evidence that time travel much less magic is possible.
God’s not a rational explanation unless and until there’s evidence for him at least being possible. And even than he wouldn’t be a good explanation without evidence that he’s not only possible, but real.
Well, it’s kinda like the lotto. You could win $1 million dollars tomorrow. What are the odds of that?
But more importantly, what are the odds you’re the first one to win that lotto knowing they’ve been calling out winning lotto numbers for 15 billion years across 100’s of billions of star systems and who knows how many 100’s of billions if not trillions of planets and moons and you still think you’re the first to win that lotto.
I think it could be said that the chances of life arising on one individual planet is lower than life arising on any of millions or billions of planets. By that logic life is more likely to have occurred somewhere other than earth before it occurred on earth. The real question is the sum of the probabilities of life occurring on every planet other than Earth times the probabilities of life from those planets reaching earth greater than the probability of life arising on Earth. As far as I know we do not know any of the values. Many (perhaps most) planets may have a probability of zero for one or both factors. However, if it could be shown that the number of planets non zero values for both terms is infinite, then we can conclude that extraterrestrial life has arrived at earth at some point. We may not have noticed if it happened after life evolved here or if it could not survive the earths environment, but it made it.
Jonathan
Right, the problem with panspermia is twofold. If panspermia could occur, then life could potentially spread through the Solar System in a matter of years, given the right conditions. But we can take a look at the places in the Solar System, and most of them are a lot less hospitable than Earth, and probably were less hospitable billions of years ago, too, so if life originated in the Solar System, then it was probably here on Earth rather than elsewhere.
Now, that still leaves the possibility of planets in other solar systems. As hospitable as Earth is, it’s still possible to imagine some planet around a distant star which is even more hospitable. But now, we’re asking that our proto-life travel between the stars, which requires billions of years. So our hypothetical cradle of life now not only needs to be more hospitable than Earth, it needs to be more hospitable billions of years earlier, and that’s a tall order, too.
Unnecessary multiplication of entities.
Well, our solar system makes a galactic orbit in something like 220-250 million years, so if it turns out there are planets leaving a trail of microbes behind them, there’s plenty of time for a variety of planets and moons to get exposed to them on pretty much a constant basis, right?
Not quite. Say there is a .01% chance of abiogenesis on any given world. If there are millions of such worlds, then there is a high probability (which I’m too lazy to compute) that life arose somewhere. You should be able to compute the probability that m sources of life propagate it, and that it hits us. If this is higher than .01%, then you can say life more likely arose off the earth. The probability of it arising on any planet is the same.
I don’t know if the advocates of panspermia compute these numbers, and what they say about the anthropic principle. I’ve never been interested in it enough to read even Crick’s book.
You don’t want to compare the raw numbers to 0.01%, as though the probability that life arose on Earth is just the same as the a priori probability of life arising on any planet. You want to first condition on the all-important piece of knowledge we have: that life is currently on Earth.
That is, using a distribution which in which all planets are a priori treated symmetrically, P(life arose on planet X | life is currently on planet X) = P(life is currently on planet X | life arose on planet X) * P(life arose on planet X)/[sum of P(life arrived at planet X from planet Y | life arose on planet Y)*P(life arose on planet Y) over all planets Y] = P(life is currently on planet X | life arose on planet X)/[P(life stayed on planet X | life arose on planet X) + sum of P(life arrived at planet X from planet Y | life arose planet Y) over all planets Y other than X].
For this to be very low (i.e., for P(life arose off of Earth | life currently exists on Earth) to be very high), it needs to be the case that the ratio of the probability of life staying put to the probability of life migrating interplanetarily is much less than the number of planets within reach of any given one.
For me, intuitively, I would not think this to be the case. I would think that ratio to be very high instead; that it is vastly more probable for life to stay successfully put once it arises than for it to successfully migrate, to a degree dwarfing the number of planets within viable reach of seeding any given one. But that’s just my intuition.
I was trying to keep it simple! The misconception seemed to be that I was claiming P(life arose on planet X) > P(life arose on planet Earth). Since we don’t have any idea of what these numbers are, I was assuming they were equal.
I’d want to break down P(life arrived at planet X from planet Y | life arose on planet Y) a bit more. It would involve the probability that life got off planet Y (clearly given that it evolved there) and then the probability that it would reach here. To compute that, you’d have to make an assumption about the distribution of planets, the distribution of their distances from earth, the density of the seeds that were ejected, and then compute the probability any seed would intersect with earth given the density at the point of the wavefront that would get here. Then we’d have to figure out the probability that a seed hitting the Earth would actually take. Given all the uncertainty here (and for P(life arose on planet Earth) ) you can get any answer that you want! I’d say the level of variance here makes the Drake Equation look like an arithmetic problem.
That’s the one thing that is probable. The universe was about 10 billion years old when the Sun was formed, so there was plenty of time for life to have evolved a few billion years before the earth was ready for it. However, I would think there would almost have to be a dense cloud of seeds around the point of origin for any to get here.
I’m beginning to think that some ET leaving his trash on the primitive earth is a more likely explanation than panspermia. I’m betting on good old homegrown Terran abiogenesis myself.
Well, life presumably can’t evolve from hydrogen and helium alone (and neither can solid rocky/metallic planets), so 1st generations star systems probably wouldn’t support life. I’m not sure exactly when heavier elements came into existence and condensed into planets, but that needs to be taken into account. Maybe life gets more likely as time goes on?
Just keep in mind 1st generation stars didn’t last long, and gave way to many generations of stars and rocky planets long before the 10 billion year mark. Super massive giant whatever stars only last millions of years, not billions. They quickly explode and create the heavy elements needed for life.
From a scientific standpoint, this is an an interesting question. I’m not too optimistic about finding separate kinds of life on Mars or Europa, but if we did it would be revolutionary.
From a religious perspective, what’s the point? What’s the difference between abiogenesis and the last thousand arguments over what God supposedly did? For those just tuning in, the score is Scientific Evidence: 1000 & God: 0. Hell, we’ve still got millions of idiots convinced that the Earth is 6000 years old.
What changes when scientists inevitably prove that life arose naturally, reproduce it in the lab, and have a few beers afterwards? The box that we can squeeze God into gets a little bit smaller, but we’ll never make the box go away. Can’t theists just embrace the scrap of dignity that they’ve got left and say an omniscient God created all matter and energy to set off the big bang?
Isn’t it discouraging that the best piece of physical evidence of supernatural intervention in the universe happened 4 fucking billion years ago?
Then they’d be deists.