Here's why:
* Momentum: Momentum is a measure of an object's mass in motion. It is calculated as the product of mass and velocity.
* Rest Mass: Rest mass is the mass of an object when it is at rest.
* Photons: Photons are particles of light, which are massless (have zero rest mass). However, they have momentum because they travel at the speed of light.
The key point: The equation for momentum is more general than just mass times velocity. It includes the relativistic momentum, which accounts for the energy and momentum of massless particles like photons:
p = E/c
Where:
* p is momentum
* E is energy
* c is the speed of light
Therefore, even massless particles like photons have momentum, thanks to their energy.
