Comment on Sea Level
exasperation@lemmy.dbzer0.com 1 week agoI’m not disagreeing with you on any of the physics of solar system formation, just disagreeing with your interpretation it means that habitable planets are high probability.
When clouds of dust and gas settle into spherical planets, what makes them rocky? What makes them have magnetic fields, atmospheres, water? What makes it so that the planet in the habitable zone hits those conditions.
The tendency of certain things to develop isn’t a lockstep correlation of 1 between these factors.
We can believe that stars are common. And so are planets. But what combination of factors is required for life, and does that combination start leveraging the math of combinatorics in a way that even billions of planets in each of trillions of galaxies wouldn’t be enough to make it likely that there are other planets that can give rise to life as we know it.
My point isn’t actually about cosmological physics. It’s a point I’m making about the math about probabilities being counterintuitive, in a way that “the vastness of the universe” doesn’t actually mean that life is inevitable. It might still be, but it doesn’t necessarily follow.
crapwittyname@feddit.uk 1 week ago
Well I didn’t specifically say habitable planets are high probability. But it just so happens that they are. Firstly consider the Copernican Principle. If we live on a habitable planet then it’s logical to make the assumption that habitable planets are common. There are strong counterpoints to this, but it’s all very hypothetical anyway so it’s better to just point to the empirical evidence: astronomers estimate that [one in five stars has an earth sized planet in the Goldilocks zone](One in Five Stars Has Earth-sized Planet in Habitable Zone – W. M. Keck Observatory share.google/J40L3PlVnAvee7C7B). In terms of the why, it’s a much more difficult question to answer, but the stages of planetary formation that are proposed include processes whereby heavier elements coagulate together, earlier, and those that end up massive enough then attract lighter elements and become gas giants. Rocky planets formed close to the sun because it was hotter there and water/ice couldn’t form and contaminate the denser elements, although it doesn’t seem to happen that way in other artist systems.
Everywhere we look we see rocky planets and we see water. It’s not unlikely that rocky planets therefore would have liquid water fairly often
exasperation@lemmy.dbzer0.com 1 week ago
That’s what I take issue with. I don’t think that follows.
If I have a random deck of cards, I can’t assume that the deck order is common. Or, if I flip a coin 20 times I can’t assume that the specific heads/tails order that results is commonly encountered, either. Just because it actually happened doesn’t mean that the a priori probability of it happening was likely.
The Copernican Principle is assuming that all decks of cards or all flipped coins follow the same rules. I’m not disagreeing with that premise, but I’m showing that no matter how many decks or coins you use, the probability of any specific result may be infinitesimal even with as many decks as there are planets in the universe.
Showing me good reason to believe that earth sized planets have a 20% chance of showing up in habitable zones still doesn’t answer the other questions I have about plate tectonics, elemental composition, magnetic fields, large moons, etc. Stacking dozens of variables with conditional probabilities can still produce numbers so small that even every star in the universe representing a “try” might not lead to a high probability result.
crapwittyname@feddit.uk 1 week ago
I think you need to let the deck of cards metaphor go! A deck of cards is specifically designed by intelligent minds to generate random outcomes, whereby natural processes follow predictable paths, and the outcomes are limited but natural laws. There is no intelligent mind altering the outcome of designing for our against randomness.
exasperation@lemmy.dbzer0.com 1 week ago
The math I’m talking about still works with weighted probabilities or conditional probabilities. The underlying factorial math expands the number of possibilities way faster than the number of “tries” can increase the likelihood of at least one hit.
The point is: the fact that something has already happened is not proof that it is a high probability event. The deck of cards hypothetical is merely an example of that phenomenon. Applying different weights (e.g., ignoring the suits of cards) doesn’t change that basic mathematical phenomenon, both only re-weights the probabilities to be bigger. But lining up a bunch of probabilities in a row still multiplies them in a way that results in a infinitesimal probability.
If there are only billions of earth-like planets in our galaxy, and only trillions of galaxies, that’s still only 10^21 chances at life. Yes, that’s an unfathomably large number for the human brain to process, but it’s also nowhere near the numbers that can be generated through factorial expansion, so if the probability of life arising is something like 10^30 on any of those planets, the expected number of life bearing planets would be pretty much zero.