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Comment by NKosmatos | Hacker News Reader

The density mentioned (0.059 grams per cubic centimeter) is the overall density of the planet. Most probably it has a much much denser core, solid or thick super hot fluid, like all gas giants. It doesn’t mean that the whole planet has the same cotton candy density (0.05 grams per cubic centimeter) from the top layers down to the core ;-)

On the funny side of this, what would happen if we kept adding cotton candies at an empty/isolated place in space? After some critical mass, the cotton candies would collapse under their own weight/mass and a new asteroid would be created. If we kept adding even more candies a further collapse would create a new planet :-)

Imagine stacking/accumulating different materials. A planet made just of bananas, a planet made of only water, a planet from rice…

/note to self - check if there is such a planet simulator available

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What fascinates me is that if you had enough cotton candy, it would be a black hole. I don't mean it would collapse into a black hole, I mean even at a uniform density of 0.05 grams per cubic centimeter, it would already be a black hole.

We're so used to surface area scaling at r^2 and volume scaling at r^3 and the weird effects that can have (never scale up an exothermic reaction), but the maximum amount of matter that can exist in a volume without creating a black hole scales by r^1. Even with cotton candy, that r^3 is going to out-scale r^1 at some point.

It's an interesting thought experiment for algorithm complexity as well. Can you actually retrieve an element from an array in constant time regardless of the size of the array? In the extreme case, the drive containing the array must have r proportional to the size of the array to avoid becoming a black hole. Assuming the query and element travel along the drive at the speed of light, retrieving the element still takes time proportional to the size of the array.

I have struggled to find an established name for this value. I thought it would be something called the "Schwarzschild density", but no luck. Famously, the [someone's name??]-density of the observable universe just happens to be very close to the density that would tip the universe over into being a very large black hole

But given that the universe is expanding, if we're close to this density doesn't that mean that the density used to be higher than the threshold at some point?

This is why when talking about the big bang physicists talk about the inflation field at the start of it. The primitives in the pre microsecond universe have to be different from a black hole otherwise there's no way to un black hole yourself.

Wouldn't it just be the inverse of the Schwarzschild radius? https://en.wikipedia.org/wiki/Schwarzschild_radius

Worth noting that even setting aside weird black hole physics, in the real world the amount of storage available given some information density and some maximum constant access latency is bound in r^3 by the speed of light, and therefore array access is not really constant time but O(∛n). This isn't some abstract ivory tower thing but the way computers actually work - due to cache hierarchies you will find that working with a 100 byte array is much faster than working with a 100 megabyte array, which is much faster than working with a 100 terabyte array. Every time the data gets larger, it gets further away...

The TLB also adds some log factors to array access, which dominate for arrays that fit within a few dozen centimeters of your CPU.

As you added more and more cotton candy you would begin to compress the centre under the pressure, and you would get some heating from this. I think there's a good change you would melt and cotton candy and eventually it would re-solidify into an enormous boiled sweet core, with a diffuse envelope of cotton candy around it.

Would love to see a simulation of that haha

A project for future odd ball people/groups

They outer layer would be an excellent insulator.

Sounds like you should visit Magrathea for a designer planet!

"Carl Sagan's Cosmos: 'The Meat Planet'"

https://www.youtube.com/watch?v=ZP7K9SycELA

This sounds like a task for one of the Culture's GSVs.

What's the minimum material density necessary for a collapse such as this? Is it possible to have a planet with a core of solid oxygen, for example?

I mean, when we talk about the Jovian planet we believe it has a core of solid metal hydrogen, the only real problem getting an oxygen planet is there is much more hydrogen/helium in the universe so that's what it's going to be made out of.

Or a planet made of a mole of moles... https://what-if.xkcd.com/4/

> You might notice that we’re ignoring the pockets of space between the moles. In a moment, you’ll see why.

Lol!

the Katamari game series plays on this idea of creating themed planets by rolling up everyday objects on Earth

You might enjoy a mole of moles - https://what-if.xkcd.com/4/

I’m sensing a new XKCD—how much cotton candy would it take until it becomes an asteroid and what would the core be after.

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