# Light from a star travels to Earth in a straight line at a constant speed of almost 300,000 km/s. What is the acceleration of the light?

##### 1 Answer

The answer is 0

#### Explanation:

To understand what this question is asking, its important to understand what velocity and acceleration are and how the two are related.

**Velocity** is the rate of change of an object's position as a function of time. (i.e. how far is an object moving over a given amount of time).

This can be written mathematically as:

**Acceleration** is the rate of change of an object's velocity as a function of time. (i.e. is the object moving faster or slower as time goes on)

This is written mathematically as:

or,

If velocity is constant (as is stated in the problem), its derivative (**acceleration**) must be 0.

A more intuitive, less mathematical way to think about it is to say if the velocity isn't changing, then it's rate of change must be 0.