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xkcd #3063: Planet Definitions (xkcd.com)

submitted 4 days ago by [email protected] to c/xkcd

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Under the 'has cleared its orbital neighborhood' and 'fuses hydrogen into helium' definitions, thanks to human activities Earth technically no longer qualifies as a planet but DOES count as a star.

https://explainxkcd.com/3063/

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[–] CosmicCleric 0 points 4 days ago (2 children)

So if you put earth into the Oort Cloud it would still be a planet, because we know that earth has the potential to clean it’s neighborhood.

Would it be a non-planet for the millions of years it would take to clear its orbit?

Does Earth's body/features magically change somehow for the duration of the clearing process, so that it doesn't resemble a planet?

The point is that using external criteria to identify what an internal thing is is not logical, or scientific.

The theoretical object in the Oort Cloud would relative fast clear the space around himself if it had the size to have a stable and long living internal heat source.

You don't know that, especially with the size of the Oort Cloud, and the size of the orbit to clear. And the rules for how much clearance has to be done is very arbitrary.

Also bodies can be small and have a decaying heat source that'll last many millions of years, or renewing heat source via tidal interactions. It's not necessarily a size thing.

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[–] AnyOldName3 1 points 3 days ago

Would it be a non-planet for the millions of years it would take to clear its orbit?

Does Earth’s body/features magically change somehow for the duration of the clearing process, so that it doesn’t resemble a planet?

Clearing the orbit of other material, and in the process, accumulating it and incorporating it into a protoplanet is the process that turns a protoplanet into a planet. While that's happening, it's getting bigger and rounder and is constantly surrounded by impact debris that's in the process of forming moons and rings or is in a decaying orbit. All of these are processes local to the protoplanet that don't happen anymore once it's become a planet.

[–] [email protected] 1 points 4 days ago* (last edited 3 days ago)

Many million years is nothing in geological or astronomical timescales. Any (small) body with a heat source that short is dead cold by know. The solar system is 4.6 billion years old and the formation of planets or larger bodys has ended about 4 billion years ago.

And tidal forces mean that a way larger body is close by, like a gas giant, as far as I remember are all known body's with tidal heating moons not planets.