h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Ok people I'm new to this site so please be gentle with me. My query is this: I would like to know where photons go> Now I know that energy cannot be destroyed, only transmuted, but if I were in a sealed room and I turned off a light the room becomes dark. Where have the photons gone? If they cahnge wavelenght they are still photons right? Please enlighten as this one is mashing my head.

Tactitus

Welcome, Tactitus.

Now, there is a question for those in the know, of whom I am none. If all else fails, couldn't we just say that the photons just drop to the floor and shatter to pieces there, so they don't shine anymore?

Y.

Photons are the "force carriers" for electromagnetism, and interact with the electrons that form yhe outer shell of all atoms.

Not being a scientist I'm not up the details, but basically the energy in the photons will be absorbed by said atoms, which will become ever so slightly warmer. The energy is conserved but changes form.

Noggin

You also forget that the photons are traveling at the speed of light, so they don't stop when they hit the wall. Instead they go through it.

Or so I'm told.

Who by?

If that was true you'd be able to see through waalls.

Noggin

Horizon said it. They said that when an object travels at the speed of light it loses it's mass and can pass through anything. They then went on to explain that Neutrenos travel at just under the speed of light and they travel through things too, and that caused them to rewrite some physics books, or somesuch.

But the speed of light-no mass thing is a generally accepted physical law.

Ummm, I thought the closer the speed of light you got the more mass you gained. At least according to one of the Relativity's. Until later...
BCNU - Crescent

Photons ( light packets) have zero mass at rest, this is why they can travel at the speed of light. When travelling they have a mass due to their energy. When photons hit an object they can interact with the electrons in the atoms of the object. If the electrons have an energy level that matches the photon, the photon can be absorbed. The photon can also be absorbed by transferring its energy to the vibrational energy of the atoms of the object( heat energy). The photon is said to have been absorbed as a phonon (sound packet). If the object has no correctly sized electron energy gaps or phonons to match the photon, it passes through the object eg. a window.

Photons may collide with an atom and be absorbed (increasing the atom's energy state), or bounce off, or miss entirely. Some photons will miss all the atoms and pass right through the wall. Photons with higher energy (or wavelength) will tend to bounce rather than be absorbed, sort of like faster/heavier bullets would, so may pass straight through walls (like X-rays). Photons with the wavelength of visible light tend not to. Therefore you can't see through walls.

If memory serves neutrinos are chargeless and thus tend not to interact with anything, allowing them to pass through most matter without affecting it. I think. Anyway, don't believe everything you hear on Horizon, it's written by journalists after all .

Yes, of course. Not after that "Real Eve" thing they did.