Energy expelled in orbit

[Opara]

Hi, this is just a general wondering on a slow day, i'm hoping this is what the forum is used for.

This was actually triggered by a post on perpetual motion the other day.What energy is used for the earth to orbit the sun.I'm sure it's gravitational but what stops the earth the earth being pulled directly towards the sun? The only thing I can think of is the gravitational pull from the moon combined with the pull from the sun gives a resultant force which produces the orbit pattern.

As a second point what keeps it moving, is it the law of inertia? If we were to tie a rope to the moon connected to a turbine, as this rotates the earth every 28 days this would turn a turbine creating energy, where would this energy be from and would it affect the moons orbit? Also is energy expelled during an orbit or does the lack of an atmosphere in space mean that there would be no resistance?

Thanks

[Opara]

So where did this initial velocity come from, presumably if the earth was stopped then it would be pulled towards the sun rather than an orbit restarting?

What effect would it have if the moon was destroyed?

Thanks

[Opara]

Cheers lads