Momentum or Earth?

Johnahh

Earlier I was thinking about circular motions and centripetal forces and the earth around the sun, If p=mv and the velocity of a object in circular motion is constantly changing does this mean Earth's momentum is constantly changing?
or is it that earth is travelling on a straight path through curved space-time and does not have centripetal force?

A.T.

Yes.
That is Einsteins model of gravity. In a local inertial frame frame the momentum of the Earth doesn't change. But you cannot extend the inertial rest frame of the Sun to include Earth. Inertial frames are only local in curved space-time.