>The simple answer is that
>energy is not lost in motion,
>it can only be transfered
>from one place to another.
>So light can travel
>indefinitely unless it comes
>into contact with which it can
>interact and to which it
>can transfer energy.
It may very well be inertia. But there are some questions regarding
For one, why doesn't light lose energy when interference occurs between
the light and the slit in Young's Double Slit Interference experiment?
In this case, the inertia would have been disturbed and some of the
energy would be lost.
Secondly, according to en.wikipedia.org, "When light passes through a
transparent substance, such as air, water or glass, its speed is
reduced, and it undergoes refraction." Thus when it travels in
non-vacuum media, there is interaction between the light and the media
yet it maintains the energy throughout.
Lastly, the inertia theory of light does not take into account the
electric and magnetic components that oscillate at right angles to
enable the light to travel forward. These continuous oscillations would
have greatly discurbed the inertia and consume energy.
So there could be other explanations than the principle of inertia.