Speed of light again :-)

[kermit911]

At the speed in wich light is traveling, shouldn't we feel it or knock us on are butts when it hits us?

[QmunkE]

No.

Photons are massless, and so do not possess "momentum" in that sense, i.e. they cannot transfer their kinetic energy to you in any meaningful way. Solar sails operate by the pressure of photons hitting them I understand.

I do recall from my A-Level physics that they do possess some sort of momentum, something to do with e=hf?

[Space]

From what I remember, photons do have momentum although they don't have mass.
Light does push you, but it's too weak for you to feel it.
If you build a massive solar sail, then you could feel it push the sail...
Look for "solar sails" on howstuffworks.com

[jake-the-peg]

Aw Space I was waiting for somebody to say that light had no momentum so that I could jump in and you beat me to it.

I was looking for a link to radiometers or "light mills" to demonstrate this effect - those little toys that look like light bulbs with sails inside 1 side silver and one black that turn due to light pressure. It seems that they don't work like this at all - they turn the wrong way for that.

It's a sad day you dont learn something!

http://math.ucr.edu/home/baez/physics/General/LightMill/light-mill.html