The momentum of mass can create variations in spacetime and alter the stress-energy tensor, according to general relativity. Anything with mass, including momentum, warps spacetime, which is the fabric of space and time. This warping of spacetime is what we experience as gravity. The stress-energy tensor, which combines mass-energy, momentum, pressure, and stress, is the source of gravitational fields in general relativity. p = mv, where p represents momentum, m represents mass, and v represents velocity (Δ time vector).