Linear momentum is mass times velocity. One (not always correct) definition of angular momentum is "rotational mass" times angular velocity. Rotational mass is usually called the moment of inertia.

The article explores how the Big Bang initiated the universe's continuous motion, affecting vast cosmic distances through ...

If the central body was the only gravitational body in the vicinity, then the spacecraft would follow an elliptical path around the central body with constant orbital energy and angular momentum.

This means that the angular momentum should stay at a constant value. But what happens if you change something—like bringing your arms closer to your body? This would decrease the moment of inertia.