Earlier quoted context omitted.
In an Arthur C Clarke story (I forget which one) the core of jupiter is a planet sized diamond.
Space Odyssey one of the sequels.
2061. Not his best work, alas.
Jupiter was formerly twice its current size, had a much stronger magnetic field
51–60 of 78 posts
Re: Jupiter was formerly twice its current size, had a much stronger magnetic field
#52Earlier quoted context omitted.
It's a matter of definitions, so we skip them and just choose something that makes sense to humans.
The most important thing about definitions is that we apply them consistently. A different definition might give different answers, but it's fine as long as it does so uniformly.
> most important thing about definitions is that we apply them consistently
The most important consideration for a definition is its practical consequence.
In this case, whether the line is drawn at 1 bar or an order of magnitude more or less doesn’t materially change that, on the same measure, Jupiter was 2x larger in the past. (Less than 1% in both cases.)
In a different context, that difference may be meaningful and should thus be noted and tested for robustness.
Re: Jupiter was formerly twice its current size, had a much stronger magnetic field
#53I've always wondered about the core of these gas giants. I assume it is some liquid form of light elements. What is puzzling is the presence of the gas giants in the middle of solar system's planetary line up: why are they in the middle and the ones closer or further away from the central star are not like them? Is it the temperature gradient?
> Data from the Juno mission showed that Jupiter has a diffuse core that mixes into its mantle, extending for 30–50% of the planet's radius, and comprising heavy elements with a combined mass 7–25 times the Earth.
https://en.wikipedia.org/wiki/Jupiter#Internal_structure
> This has resulted in the theory that Jupiter does not have a solid core as previously thought, but a "fuzzy" core made of pieces of rock and metallic hydrogen.
https://en.wikipedia.org/wiki/Juno_(spacecraft)#Scientific_r...
Re: Jupiter was formerly twice its current size, had a much stronger magnetic field
#54[dead]
Re: Jupiter was formerly twice its current size, had a much stronger magnetic field
#55Earlier quoted context omitted.
As others note, the definition of Jupiter’s radius is set by where the pressure is 1 bar. This is somewhat arbitrary, but the arbitrariness doesn’t matter much: the pressure drops to 1 micro bar just 320 km higher, which is <0.5% of Jupiter’s ~70,000 km radius.
Venus would get a slight radius buff, too, if we applied that metric.
But Venus has a solid surface.
Re: Jupiter was formerly twice its current size, had a much stronger magnetic field
#56Earlier quoted context omitted.
It's a matter of definitions, so we skip them and just choose something that makes sense to humans.
The most important thing about definitions is that we apply them consistently. A different definition might give different answers, but it's fine as long as it does so uniformly.
The point is that there will be multiple definitions, so which one do you choose? From there your conclusion can be that we just use a loose definition that humans can easily grasp.
Re: Jupiter was formerly twice its current size, had a much stronger magnetic field
#57Earlier quoted context omitted.
This is because of Newtonian gravity being inversely proportional to the square of the radius, right?
Gravity changes little over that distance - it's more because of the compounding effect of atmospheric pressure (the deeper you go, the more air you have above you which raises the pressure, raising the density and meaning that pressure increases exponentially faster).
What makes that curve exponential?
Re: Jupiter was formerly twice its current size, had a much stronger magnetic field
#58Re: Jupiter was formerly twice its current size, had a much stronger magnetic field
#59Earlier quoted context omitted.
> I assume it is some liquid form of light elements. Why would you assume that? The heavier elements such as iron are likelier to move to the center of gravity.
I'd assume these elements would be created in the sun and keep close to the sun, because of their higher mass.
Until several billion years in the future, our sun will create no element heavier then helium.
IIR, our sun's mass is far too low to ever create any element heavier than carbon.
Re: Jupiter was formerly twice its current size, had a much stronger magnetic field
#60How is the size defined for a gas planet? The gas density just keeps dropping, where do you draw the line (isosurface, rather)? Earth's radius is always the one without earth's atmosphere.
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