What about those small propels that "mysteriously" spin when they are put
close to a source of light. Is not the momentum of the photons that make
them spin?

4B


"Bjoern Feuerbacher" wrote in message
...
wrote:

if photons in motion have mass and energy why don't they knock stuff
over
like little things like blades of grass or ants out of a tree

Do the math. Visible light has a wavelength of 5 * 10^(-9) m. Momentum
of a photon is p = h/lambda. Thus p is approx. 1 * 10^(-25) kg m/s. Even
for gamma rays, whose wavelengths are about 10^(-6) smaller, the
momentum of a photon is only about 1 * 10^(-19) kg m/s. I don't think
that could knock even an ant or a blade of grass over - do you?


Bye,
Bjoern