If the earth was made entirely of water, (but still retained its atmosphere) what shape would it be? Liquids in space typically form spheres, but if you scaled it up to the size of the earth, would other factors come into play. For example, what sort of effect would the tidal forces exerted by the moon have? Presumably they would turn the planet into an ellipsoid, but would the effect be more noticeable than the variations we see in the oceans at the moment?
What about the centre of the earth? Would the pressure of all that gravity cause the centre to heat up? Would it be enough to boil the water, and if so, what would happen to the steam?
Also, the side that faces the sun would be significantly warmer than the side that faces space. What sort of convection current would this cause, considering the warm part and the cold part were on opposite sides of the centre of gravity?
For bonus points, what would happen if Jupiter was made entirely of water?
Has anybody ever estimated how much extraterrestrial matter crashes into the Earth during an average year? Surely, it wouldn’t take all that long for a water world to acquire a solid core.
Assuming solids do not hit the planet, would the core remain watery? I suspect that it might turn into somethig else, but I don’t know what that might be.
One consideration is that without an iron core or magnetic field much of the atmosphere would be stripped away. How fast that would play out on a water planet I don’t know.
Consider that as the pressure and temperature increases moving towards the core, water would change from vapour to liquid to a solid. http://www.lsbu.ac.uk/water/images/phase.gif
So I suppose you could have various layers of super hot water sandwiched between layers of “ice” all underneath an ocean.
The idea is that the Earth’s magnetic field (which is a product of the iron core) keeps the solar wind of charged particles from (mostly) hitting the atmosphere, and that the particles would otherwise slam into air molecules and knock them into space.
Though I think I saw something recently that disputed the hypothesis; unfortunately don’t have time to look now.
I’m not sure how compressing water will alter the temperature, but if we ignore this possible effect, it looks from your chart like the first ice layer will start at between 50 and 100 km depth, assuming its above 0 degrees C, pretty close to the thickness of the earth’s crust.
In view of the fact that the terminal velocity of a bowling ball in water near the surface of our earth is low (probably a few km/hr), and that the effect of gravity decreases toward zero as the ball gets closer to the center of the watery planet, it seems clear that the ball basically doesn’t oscillate.
This one’s easy: the tides due to the moon would be about 54 cm relative to a perfect sphere. This was first calculated by Newton — I couldn’t find a derivation online, but the classical mechanics textbooks by Thornton & Marion or by Taylor have derivations. The Sun would add or subtract another 25 cm to this, depending on the time of the month (spring vs. neap tides.) However, this assumes that the water at the surface stays liquid.
I’m honestly not sure. In theory this could be calculated if you knew the equation of state of water to a good enough precision. If I had to guess, though, I would think you’d end up with the water at the center in a supercritical fluid state rather than a gaseous state.
This one I’m really not sure about. However, note that convection currents largely arise because warm water is less dense than cold water, and so it “wants” to move upwards against gravity. However, on a water-droplet earth, the warmer water would need to move “sideways” relative to gravity. There’s no reason for it to do this, so if I had to hazard a guess, I’d say that the effects of Sun-driven convection would be minimal.
I would think the liquid water layer would probably only be tens of miles deep at most, the inner layers of the body would be various phases of ice, some of which might be electrically active enough to form a magnetic field. But, even failing that, the importance of the magnetic field is not altogether certain: Venus has an extremely dense atmosphere but a trivial magnetic field.
Water vapor is a major greenhouse gas, so the surface of the planet would be quite warm. In fact, it is not obvious that there would be a discernible surface, the water vapor would just transition to liquid gradually, as, they think, with the gas giants. If you could assure a high-purity planet-sized ball of water, I suspect there would be no clouds to speak of, because the atmosphere would be homogenous. If there were clouds, the surface temperature would probably be a little lower due to sunlight reflecting off.
