Questions about molten rock in space.

[too-open-minded]

So i'm wondering, if the earth had formed without the presence of the sun. Would it have already cooled down by now or would it still be mostly molten rock like it is now?

Found this - http://phys.org/news62952904.html

 

So the sun has little role to play in the earths temperature, is this mostly because of the radioactivity heat or just the time it will take for the amount of molten material to cool down? or something else?

[EdEarl]

Without fission radioactivity in the Earth's core, there would be no volcanos and no earthquakes. However, the surface of Earth is warmed a little by the Sun but would not be as cold as Mars surface.

 

A few feet under the surface of the Earth, the temperature is about 70F, regardless of surface temperature. However, as one goes deeper, the temperature increases. A few thousand feet down the temperature can kill.

Edited May 15, 2013 by EdEarl

[swansont]

There is negligible fission in the earth's core. The energy comes from radioactive decay.

[EdEarl]

There is negligible fission in the earth's core. The energy comes from radioactive decay.

 

ty. I learned something. Fission and radioactive decay are similar but different, and fission releases much more energy.

[Enthalpy]

Our Sun makes the difference between 288K at Earth's surface and very cold. The rest, from 288K to 3000K at the center (value still debated), results from internal heat. So the 288K make little difference, despite Sunlight is much stronger.

 

What is the internal heat? Not completely known yet. 2/3 radioactivity and 1/3 accretion heat (the gravitation/kinetic energy of materials that made the planet)? More recently they said 1/3 and 2/3 instead. Meanwhile the innermost core is said to be iron+nickel that solidify due to the pressure, and this slow process releases some heat.

 

We may know more some day through neutrino telescopes that would "map" (very roughly) the position of radioactive materials in our planet.

 

Have other planets the same source(s) of heat? Unclear at Jupiter for instance. It radiates more heat than it receives Sunlight, which needs more efficient internal heat than Earth. Current interpretations involve the condensation and solidification of gases.

[EdEarl]

"A thermometer on the sunny side (of the International Space Station) would reach something like 250 degrees F (121 C), while a thermometer on the dark side would plunge to something ike minus 250 degrees F (-157 C)." From: http://wiki.answers.com/Q/What_is_the_temperature_outside_the_international_space_station

[Iggy]

So i'm wondering, if the earth had formed without the presence of the sun. Would it have already cooled down by now or would it still be mostly molten rock like it is now?

 

It would not have cooled down,

 

Regardless of whatever causes heat in earth's core, the amount of heat escaping through its surface is only 75 erg / cm^2 / s (or, 0.078 W/m^2). You can find that here. Or, verify it in Allen's Astrophysical Sciences.

 

So, earth is losing next to none of its internal heat. It's losing it very slowly.

 

That said, very little of Earth's internal heat came from the sun. It comes mostly from conservation of energy. When particles collapse from high gravitational potential to low, their potential energy is converted to kinetic. The kinetic energy of particles confined to a small volume is converted to heat. So, when earth formed there was a tremendous amount of heat created through no effort of the sun. It is still bleeding that off... very slowly.

Edited May 15, 2013 by Iggy