Final answer:
Conservation of momentum is valid in special relativity when momentum is defined with the Lorentz factor; this fundamentally supports modern physics and the study of subatomic particles.
Step-by-step explanation:
The law of conservation of momentum indeed holds true in the realm of special relativity, but the definition of momentum is altered from the classical one. Specifically, in special relativity, the relativistic momentum of a particle is defined by incorporating the Lorentz factor, represented by γ (gamma), which accounts for the increase in momentum as the object's velocity approaches the speed of light. The formula becomes p = γmv, where γ = 1/√(1 - (v/c)²) and v is the velocity of the particle. The momentum conservation principle is a cornerstone of modern physics and plays a crucial role in the analysis of subatomic particle interactions, such as those observed in particle accelerators.