Sun's energy and earth's rotation

[ramanan]

On earth the rate of energy obtained from the sun is c.170000 mega joules.

Now, does earth consume any of these energy for its rotation ?

Or is it rotating due to sun's gravity and rotational speed?

[swansont]

ramanan said in post #1 :

On earth the rate of energy obtained from the sun is c.170000 mega joules.

Now, does earth consume any of these energy for its rotation ?

Or is it rotating due to sun's gravity and rotational speed?

 

The earth rotates because it has angular momentum, and that's a conserved quantity in the absence of an external torque. We are transferring some angular momentum (and energy) to the moon through tides, so I imagine the same is happening with the sun at a smaller scale. (The moon is currently receding at ~ 4 cm/year). It doesn't take any energy to rotate - the energy is already there. It would take energy (and a torque) to increase the rotation, and energy would have to go somewhere if the rotation rate decreased.

[ramanan]

So shall we infer this way Swansont,that any object in the universe has got its own potential energy?

[aman]

If the Earth has a darker face in any direction, there should be a difference in absorbtion and reflection and an actual positive push in one direction over another.

Just aman

[swansont]

ramanan said in post #3 :

So shall we infer this way Swansont,that any object in the universe has got its own potential energy?

 

Technically potential energy is shared between the objects in the system, but when the masses are so different we usually "assign" the energy to the smaller. But yes, all objects affected by gravity have some amount of gravitational potential energy.

[swansont]

aman said in post #4 :

If the Earth has a darker face in any direction, there should be a difference in absorbtion and reflection and an actual positive push in one direction over another.

Just aman

 

But to any extent this happens, it does so radially WRT the sun, and thus it doesn't exert a torque.