# Does gravitational energy convert to heat?

Asked by GeorgeGee (4914) August 1st, 2010

Would a cold meteor entering the gravitational field of a planet that does NOT have an atmosphere lose some of its potential energy through the gravitational pull? If not, and the meteor ends up circling the planet, where did the energy go?

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Take this with a grain of salt, but wouldn’t the meteor not lose it’s gravitational potential energy until it’s converted to kinetic energy?

Parrappa (2420)

Without an atmosphere no energy is lost until impact, at which point a huge amount of heat is created, along with deformation, sound etc. If the meteor ends up circling the planet, no energy is lost because all its energy is used to perpetuate its orbit at a particular velocity and orbital radius.

The potential energy is converted to kinetic energy as the speed increases. If the angle of entry is too steep, it will crash into the planet. If it is too shallow, it will speed up as it approaches the plant and slow down as it “skips” off and away. If the angle is just right the meteor will end up in orbit around the plant.

LuckyGuy (34243)

@worriedguy Yes, just so (GA). The gravitational potential of an object due to Earth’s mass is maximum when the object is “at infinity”. As it’s drawn toward Earth it loses potential energy and gains kinetic energy. If it doesn’t impact or go into orbit, then the reverse process occurs after the encounter.

gasman (11261)

Ok so I was wrong, but I was at least I was using the right terms and kind of had the idea.

Good thing I threw in that thing about the salt, heh

Parrappa (2420)

In a word, yes.

HoneyBee (347)

If we split gravitational hairs, then some energy is generated in the meteor as it has a close encounter with, or goes into permanent orbit around an object of large mass. In the case of a planet such as earth, if we were to pick up an orbiting meteor well beyond the outer reaches of our exosphere, the effect would be quite small. Earth is not such a large mass that it would generate much heat.

But gas giants such as Saturn and Jupiter do influence satellites in orbit around them. Jupiter’s moon, Io shows significant gravitational tidal heating, enough in fact to power active volcanic activity on the Io’s surface even though the moon is far too small to have residual heat from the formation of the solar system or an nuclear reaction like earth in its core.

ETpro (34394)

mattbrowne (31542)

Thanks @ETpro, that’s kind of what I was looking for. I imagined that must be the case but had never heard of any astrophysical examples to confirm the theory. Gravitational tidal heating makes sense since gravity is causing forces within the affected mass.

GeorgeGee (4914)

@GeorgeGee Yes, the moon also causes a tiny bit of gravitational heating on earth. Nothing anywhere close to what little Io experiences from the massive gravitation of Jupiter, of course.

ETpro (34394)

Strong gravity can cause tidal forces, which can cause some heating.

RocketGuy (8792)

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