# How far can a beam of light travel if there is no obstruction in its path?

Jan 20, 2018

In theory infinitely far.

#### Explanation:

The beam will reduce in intensity as it spreads out ($\propto \frac{1}{r} ^ 2$) but if there is no obstruction, in principle there is no limit.

Jan 20, 2018

As far as
$s = c \cdot t$
where $c$ is the speed of light and $t$ is as much time as you want to give it.