# mass pressure density & the size of planets (question)

Discussion in 'Physics & Math' started by RainbowSingularity, Jan 8, 2022.

1. ### RainbowSingularityValued Senior Member

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when listening to science documentary's say how many times the earth can fit into Saturn or Jupiter,
does that account for the increased gravitational density ?

it seems that as you get more earths & squish them together to make a Saturn
you increase gravity & so increase density ?

im a bit confused by the concept

when someone uses earth sizes to match other planet sizes, does gravity make a difference so you get to a point where adding another earth is not equal to another earth at a lower density & gravity ?
(i hope my question makes sense im very tired)

3. ### Michael 345New year. PRESENT is 72 years oldlValued Senior Member

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Think phrase used only for SIZE comparison

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5. ### exchemistValued Senior Member

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As Michael 354 says it's only a size comparison. But since you raise the subject, the Earth, being made of rocky minerals and solid and liquid metal, is not very compressible. Even the gravitational pressure of Saturn would not reduce its volume by a large amount.

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7. ### RainbowSingularityValued Senior Member

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thanks

so it depends on what the earth is made of

i guess there is some type of formula to gravity that provides its own compression of various material.
if it was a super earth size would it make much different ?
or the size of Saturn ?
would gravity super compress the material so you could fit it into it without it makine any real discernible difference and the earth being added would end up increases mass but not over all size ?
is there a theoretical model size where it would compress any earth to a tiny ball amount ?

not a particularly serious question but it occurred to me there might be some type of ratio law something something thingey .

8. ### exchemistValued Senior Member

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There are formulae for working out the atmospheric pressure at various depths of a gas giant like Saturn. I can't understand the rest of your post, as it is too muddled. So I'll have to guess at what kind of answer may be what you are asking for.

As you compress minerals, one of the things that can happen is phase changes. These occur inside the earth at great depths. Different mineral structures, with somewhat higher densities, become stable under high pressures, compared to those we see at the surface. So working out what would happen if the earth were placed deep inside the atmosphere of Saturn is not straight forward. But any reduction in size would only be a few %.

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