Einstein said it was so,
And if anyone would, he'd know.
But what if the speed of light weren't constant?
Suppose it varied by an infinitesimal second?
Who could measure it?
Not even Michelson-Morley, I'd bet.
And who could tell what the effects would be?
Probably not even Albert if he were around yet.
Now here's a proposal,
though it's likely improbable,
That explains how light can act as a wave and a particle.
The speed of light isn't constant,
Nor is its emission instantaneous.
Now that fits with our everyday experiences.