Is that last sentence true? Thats not what they believe when I went to school. Designs for solar sails were all made from reflective materials.

I find Warren Davis' statements to be a bit irresponsible - this is often done throughout our educational process. We oversimplify and give misleading characterizations of things to help people to understand, according to the level at which they are studying. He should be qualifying his use of the word 'mass'.

Do remember that light is not an object. But it does have the property of 'momentum', and that momentum can be transferred. As far as the notion that this happens during absorption and not reflection - well thats news to me. I thought it was during both.

yeah you're right

I don't remember what I was saying this morning. I had to run away for a dr appt and was writing as fast as I could

the inertial momentum of incident photons is transferred to the medium (usually as heat) and the reflected photons rebound with the same magnitude of momentum, but oppositely directed, conservation of momentum demands that the momentum transferred to the struck object is twice the (magnitude of the) momentum of the incoming photon.

________Regarding the topig________

Recently, I watched a broadcast of the European TV program about one of Einstein's colleagues, Gilbert (sorry, didn't catch his name). Anyways, they stated that some of the Einsten's formulas for "General Theory of Relativity" have been plagiarized from Gilbert!!! * * *

CAN YOU BELIEVE IT? ? ?

well it was more like didn't give credit "to" lol

All I asked was about reflection and if it influences the medium it hits.

Light being or not being an object is not what I'm trying to get here, you are saying that something is passing momentum, and if something is passing momentum that something must consist of mass no? How can something consisting of nothing apply momentum which is a force. I'm not convinced by your poorly stated statements.

Nice metalwing, you just quoted my last 3 or so statments, how clever of you.

With all due respect, your questions are poorly stated, not the answers.

Light has duality. In some ways it acts like a wave and in some it acts like a particle. That is just the unique nature of light. Energy and matter are different versions of the same thing, hence the equation E=MC2.

Light has measurable momentum and not only can power a solar sail, can be used to power spacecraft in a more direct manner. One design has powerful lasers pointing at the rear of a spacecraft to push it along.

The momentum property of light deals directly with it's wavelength just like an ocean wave. This property causes the light wave to conserve energy by slowing down if the wavelength is changed by passing through a medium such as glass. The conservation of energy requires that the wave have the same energy but if the wavelength changes, something has to give, so the light wave slows to compensate. This fact is way the standard speed of light is usually followed by the condition "in a vacuum".

Actually I just accidentally hit the enter button drinking coffee.

Hehe. None of the women have came in this thread, I guess women do not like science.

Jane is in this thread and she likes science.

Nice.

Female. Blonde. Reads Science Threads.
Fabulous!

I've just been reading a book discussing this very issue and it's relationship to the potential for disguising things via invisibility. The problem is that waves must adjust in order to pass through various materials due to their molecular structure. The reason light bends in water, for example, is that it must slow down as it enters the medium.

In the past few years plasmonics technology has created metamaterial that has a negative index for the most difficult of the visible spectrum - the blue/greens. That requires "squeezing" the light to manipulate it at the nano level. That also means, in theory, that we are able to make light travel at a speed that is faster than the known speed of light, which I know sounds bizarre.

Bottom line is that light can be manipulated in ways that defies most people's imaginations and certainly exceed the limits of most people's knowledge of light science.

(Girls like science...go figure!)

speaking of light traveling faster than the speed of light

I was just reading a paper someone had written on trying to develop transporters (like star trek)

they were shootong photons into it and trying to transport them across the room. the interesting thing was that they had the photons coming out of the other end picoseconds before they were inserted into the front end

I'll have to find that paper again it was pretty interesting. heavy in incomprehensible math but still readable

I'd like to see that, although the thought of the "incomprehensible math" sends shivers up and down my spine. (Girls who like science can't always do the math!)

You have a lot of knowledge about light science...I seem to recall that you worked in light engineering. Did you work on things like the interferometers my eye doctors have used?


PS...I begged my son to go into the development of transporters as a college mission, but alas, he's more interested in biology!