Comment by lrem | Hacker News Reader

Comment by lrem | Hacker News Reader

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A regular star has a significantly lower density. The ongoing fusion causes a pressure that keeps it from collapsing. The atoms here move chaotically through a 3d space in quite a volume. So your ball sits on too large a surface of cellophane to go really deep. That can continue for increasing masses for quite a while. Google tells me the heaviest known star is about 200 solar masses.

Black holes and neutron stars are fundamentally different - there’s no space left between the matter of a neutron star. Now, the physics of that is a bit over my head, but a simplification I got from a PBS Spacetime episode is that the matter in a neutron star pretty much overlaps in 3d and stars filling up some quantum mechanics dimensions. When those cross a threshold, the last forces give way and everything collapses without a limit. So now we’re talking about a ball on your cellophane as small as physically possible for its mass (compact), pushing down significantly deeper… Until it gets replaced with pretty much a puncture, pushing it down to some abstract floor.

My understanding of it is somewhat similar, although I'd argue that's where our mental imagery breaks down: the "weight on fabric" metaphor works to a point then stops conveying what's really happening and becomes misleading.

I think of it like "magnets as rubber bands", and what I call "Feynman lies":

> I can't explain [magnetic] attraction in terms of anything else that's familiar to you. For example, if we’d said the magnets attract like as if they were connected by rubber bands, I would be cheating you. Because they're not connected by rubber bands, I shouldn’t be in trouble, you’d soon ask me about the nature of the bands… and secondly if you were curious enough, you'd ask me why rubber bands tend to pull back together again, and I would end up explaining that in terms of electrical forces, which are the very things that I'm trying to use the rubber bands to explain, so I have cheated very badly, you see.

> [...]

> But I really can't do a good job, any job, of explaining magnetic force in terms of something else that you're more familiar with, because I don’t understand them in terms of anything else that you are more familiar with.

direct link: https://www.youtube.com/watch?v=nYg6jzotiAc&t=1263s

but the whole chapter is worth a watch: https://www.youtube.com/watch?v=nYg6jzotiAc&t=894

That last sentence is a phenomenal explanation of why it can be harder for experts to teach a subject than non-experts.

https://en.m.wikipedia.org/wiki/Neutron_star#Structure

I think you're misremembering, we don't know what's at the center of a neutron star, or that there aren't other, more dense, types of stars.

I think you’re right. I misremembered at the very least that the whole star is the quark gluon plasma.

That’s what I get for treating modern physics as a kind of a vaudeville show ;)

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