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I've recently watched one conversation (I won't post a link since the conversation is not in english) involving a physicist (at least he claims so), who spoke about probabilistic estimates of the Solar System formation and the birth of life. Which are:

  1. There are approx. 2000 planetary systems discovered, and all of them, except the Solar System, have angular momentum mostly in a star, which agrees to Kant-Laplace theory (probably it's the Nebular hypothesis). But the Solar System is the only one amongst them with angular momentum mostly in planets. This was sort of explained by the Schmidt's hypothesis (it's about the Accretion as I understand), that the Sun was flying through some debris and "picked" some. But the probability of such an event is very low, given the speeds of participating celestial bodies, read quantity of moving stars with requisite speed (why those stars have that speed is also unknown), and also there should have been supernova explosion at the same time. So the Solar System formation explanation is based on the chain of unlikely events.

  2. Earth is the only planet in the Solar System that has continental crust and oceanic crust (I guess it is important for the water cycle and life formation on Earth in general). The only explanation of that fact also relies on the chain of low probable events:

    • once Earth had an Lagrangian satellite (near Earth), comparable to Mars in size, which is itself unlikely, since Lagrangian satellites are typically much smaller;
    • each of them were each other's Lagrangian satellites, which is also unlikely, nothing like that was discovered up to date;
    • then some unknown power brought out that satellite from Lagrangian point. Such power could have resulted from an event of some wandering star or another massive object moving through the plane of the Solar System, which is nearly impossible since even at the event of galaxies collision, the probability of collision of stars is vanishingly small;
    • as a result, that satellite "rubbed" Earth in an event of collision, tore off some amount of crust, that was how place for oceans was formed, also the Moon was formed from the resulting debris.
  3. Without the chain of events above the birth of life as ours is impossible, and since the aforementioned planetary systems have some consequences of formation according to Kant-Laplace theory, there is no intelligent life possible there.

Are those statements true?

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    $\begingroup$ You're asking a lot of questions. Certainly the angular momentum in the central star vs in the planets should be a separate question than the Earth continental and oceanic crust and the questions about the Lagrange planetoids should be a separate question as well, though that one might work as an umbrella on the couple questions you asked. $\endgroup$ – userLTK Feb 21 at 10:12
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    $\begingroup$ As the previous comment states, those are a lot of questions, and most of them are still a field of active research. You might look up a lecture on "planet formation", sort your thoughts, and ask more pointed questions? Kant-Laplace are often quoted as the originators of the nebular hypothesis, but our thinking and knowledge since those times has developed by quite a bit. $\endgroup$ – AtmosphericPrisonEscape Feb 21 at 12:25
  • $\begingroup$ Welcome on the Astronomy SE! My suggestion: Simple cut out from your this question everything, except the first question. After you've got the answer to it, use what to learn from it, and formulate your second question. If you do this, I will help you with my votes. $\endgroup$ – peterh - Reinstate Monica Feb 21 at 16:48
  • $\begingroup$ @peterh-ReinstateMonica Done that, but userLTK already gave decent answer. $\endgroup$ – yellowcat Feb 21 at 17:35
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    $\begingroup$ Point 1 is definitely false. See Berget & Durrance (2010) which notes that all the 28 systems studied (hot Jupiters and hot Neptunes, which would have lower angular momentum than planets further out) have over 50% of the angular momentum in the planet rather than the star. $\endgroup$ – antispinwards Feb 22 at 13:24
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I'll touch on a few of these because I disagree with some of those ideas.

There are approx. 2000 planetary systems discovered, and all of them, except the Solar System, have angular momentum mostly in a star

There's a few problems with that argument because planets close to their star are easier to identify. We don't have a complete picture of the solar systems around other stars, so we don't know the full answer to this.

Earth is the only planet in the Solar System that has continental crust and oceanic crust

Again, we don't know. I think it's interesting that Earth has entire continents of mostly granite and Mars/Venus have almost no granite and maybe that is a byproduct of oceans and water mixing in the crust, or, maybe something else, like the giant impact . . . but we don't know enough about exoplanets to say how common continents of granite might be. As for plate tectonics, there's some models about that which suggest the size of the rocky planet is a factor. I think plate tectonics might be fairly common, at least based on models.

Earth had an Lagrangian satellite (near Earth), comparable to Mars in size, which is itself unlikely, since Lagrangian satellites are typically much smaller

I have a big problem with this statement because during planetary formation there were perhaps a few dozen planetesimals. That a planet might have a lagrange point minor planet when planet formation is very young doesn't seem that strange to me, and we also don't actually know if Theia was in a Lagrange orbit, it's often speculated that it was, but nobody really knows. If Theia was in a Lagrange point, it was only there for about 1/50th of the age of our solar system. Not all together that strange.

then some unknown power brought out that satellite from Lagrangian point

Orbital perterbations could have done it. No need for anything so exotic as a wandering or, as I like to call it "just passing through" star.

There are reasons to think that life friendly Earth-like planets might be rare. Earth's relatively stable orbit, though Earth did spend significant periods frozen, it's still mostly been in the right distance from the Sun for a few billion years. That requires a very stable orbit and the right size star - too big, the star would age too fast. Too small, red dwarfs get colder over time, not warmer. I think a star that grows larger and more luminous works well with a photosynthesis planet which removes CO2 over time.

The perfect combination of events to allow life to grow (it took a billion years just to make the first nucleus), might be rare, but I think events like the giant impact would still happen from time to time.

The James Webb space telescope might provide more information on this subject. I think for now, it's more speculative and the information that can be observed is very limited.

I disagree with some of the arguments but I agree with the overall premise that planets with Earth's combination of seemingly just right circumstances - oceans of water but not covered by water, continents of granite that basically float over the basalt, an atmosphere that's thick enough to protect the planet but thin enough that it can be changed by life on the planet over time, making a partially Oxygen atmosphere possible. A magnetic field, plate tectonics and pretty impressive long term orbital and axial tilt stability and relatively few globally catastrophic meteor impacts. Earth got a lot right and that combination of stuff that went right might be pretty rare. But conclusions based on assumptions are limited. We need better telescopes to get real answers and some bigger and better telescopes are on the way.

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  • $\begingroup$ Thanks for the detailed answer. I've expected that some, if not all, statements are questionable. All that was said so peremptorily, that I've decided to check it. $\endgroup$ – yellowcat Feb 21 at 17:45

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