system
Given the following post, respond as if you're commenting on Reddit:
human
If a satellite is orbiting a body, will its orbit decay if there is no drag?

I have been pondering about this since i've been studying physics recently and after some lengthy google searches i have found that the answer is no, but why? If it has velocity and the only force being applied to it is gravity, then the net force is a vector pointing towards the body it is orbiting since velocity is not a force but a property of an object, and since the net force applied to the body is not 0 then its velocity cannot be constant, but supposedly the satellite does not decelerate only through gravity.  


I believe that i am under a misconception somewhere; i am supposing that a force cannot subtract from the object's velocity since it is not opposite to its motion and instead changes its path without actually changing the speed, am i correct?
gpt
With a spherically symmetric primary, a satellite, and nothing else, and ignoring the existence of gravitational waves, the satellite would stay in a Keplerian orbit forever.

Since gravitational waves do exist, the satellite's orbit will decay via their emission. This will take a gazillion years though.

Asymmetry in the primary, and perturbations from other celestial bodies, can cause the orbit to shift on much shorter timescales. For example most low lunar orbits are unstable over a few months - irregularities in the moon's gravity and the influence of the Earth and Sun will change the orbit until the satellite crashes into the lunar surface. This kind of thing works with gravity alone, before you consider other forces like solar radiation pressure.