this post was submitted on 15 Mar 2026
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That impact is insane. It's like they are balls of liquid.
Imagine if there had been life, or if that happened now. Everything and anything just gone. In an instant. Not even fossil records or anything left over.
Planets are balls of liquid really, they might have a thin shell that's solid but they behave as a liquid under pretty much any interaction. For gentle interactions they stay as near perfect spheres as a liquid under self gravity does. For more violent interactions they behave like the simulation shown.
That makes sense. I've always understood that the core is molten and seismic plates move about on a semi liquid. But I hadn't thought about it as a whole.
We are standing on a very thin crust of a ball of very hot liquid.
Does that make the planets eggs? Hard outer, but thin, shell with a liquid core?
They even have a different density for the "yolk".
They should rename the movie "The Core" to "The Yolk".
Only certain planets (like ours) actually have a liquid core with a solid outer crust. Most rocky planets are like Mars, completely solid all the way through.
I believe what the other commenter was getting at is that, on large scales, the solids that make up planets behave like liquids do at smaller scales. Since if you zoom out, there's not much different between a bunch of rocks loosely held together with gravity and a water droplet weakly held together by surface tension.
Could this object that drive-by slammed into Earth be the source of the iron for that molten iron core we have or did the Earth already have it?
Even if they are "solid" at a human sized scale they are effectively liquid on a planetary scale. Gravity is just so much stronger than the internal stiffness at that scale that they behave as if they are a liquid with effectively no interal stiffness. That's why as you get smaller down to moons and asteroids you start to se shapes that arent spheres, the materials strength has sufficient strength to be able to resist gravity at those scales and the material is acting more like a solid.
Gravity is so weak, that the electromagnetic force (the one that determines solid/liquid/gas) can resist its influence until you get to planetary scales.
Mountains can only exist because of the utter feebleness, of gravity.
To overcome the coulomb barrier; to achieve nuclear fusion; you need a stars mass of material forcing the nucleons together.
As you said, "at that scale", which is totally correct. I'm just trying to ensure that anyone reading this doesn't get the impression that gravity is strong compared to the other fundamental forces.
Whoa.