In article ,
says...
i know such a thing is not possible of ever existing, but suppose...

with a snap of a finger, planet earth turned into a giant watermelon.

what would happen?

this is my prediction. tell me if you think i'm right.

gravity would immediately collapse the watermelon and the center would
turn very hot due to the sheer pressure of the damn thing.

Not due to the 'pressure' as such, but due to the work done in
compressing the central parts. (Note that the Earth's rocks are already
compressed, though water would compress more. The Earth-size watermelon
would shrink to be smaller than the Earth is now, even a bit smaller
than the Earth would shrink if it were somehow uncompressed and left to
settle.)

as the watermelon collapses, the liquid in the melon would burst out
of the cracked rinds and evaporate into gas. planet melon would keep
shrinking and shrinking until all the water boiled and evaporated and
only bits of burnt rinds would remain which would then drift off into
space like asteroids.

Wrong. Let's assume for the sake of argument that we start with a ball
of water. How much it shrinks will depend on the equation of state of
water at high pressures. As it shrinks it will heat up, indeed - to
find out how much you would have to integrate pressure x area /
distance, and the distance in turn depends on the pressure of H2O at a
given density. Probably the latter would have to be estimated as some
pressures involved would be greater than testable in a laboratory.

My guess is that the core of the Earth would convert into a form of Ice
that is stable at relatively high temperatures and pressures (there are
about nine known forms of ice, all but one denser than water and stable
only at pressure). This would be quite hot. Outside it would be a
layer of water at boiling point (some miles deep - 50-100 perhaps?),
surrounded by a dense atmosphere of steam. If there was enough steam,
some would escape into space due to the Solar Wind or the gravitational
pull of other bodies. I would guess this would be a very small part of
the total water.

The temperature of the boiling sea would depend on the atmospheric
pressure. Whether heat from the centre would transmit as convection or
huge eruptions of steam, I can't say.

Pure energy conservation should tell you that the planet could not *all*
boil into space!

This would be an interesting physics problem and given a few hours I
could probably make ballpark estimates. However, I'm pretty sure of the
general trend as described above.

- Gerry Quinn