# Photons travel with speed #c# irrespective of frame. Explain?

##### 1 Answer

Photons have zero mass so they travel at the speed of light when observed by any observer no matter how fast they are travelling.

#### Explanation:

Photons have zero mass. This means that they always travel at the speed of light. It also means that photons don't experience the passage of time.

Special relativity explains this by the equation which describes relativistic velocities when an object is emitted at velocity

So consider a photon emitted at the speed of light

Newton would add the velocities to have the photon arrive at

So, the photon arrives at the observer at the speed of light no matter how fast the device which emitted it was travelling!