Dissipation of light?

[GuidoHunter]

Hah. You rock, Chrissi.

--Guido

http://andy.mikee385.com

[Rediahs]

*grins*

[magister_negi_magi]

Okay, here's something else I'd like you to explain, just because I'm learning SO much: When you shine a flashlight, it spreads it out in a widening beam, right? Well, the farther the object you point the flashlight at, the dimmer the light, to the point you can't see it anymore. I'd like to know how this works, also.

[somerndmguy]

Re: Dissipation of light?

Doesnt that just diffuse because of the Earth's atmosphere? I mean, if stars can be seem for millions of light years away (strange usage of measurement for what we are discussing but you know what i mean), then that means something must be distorting it here on Earth... right?

[Lightknight924]

Re: Dissipation of light?

Not necissarily. The light capacity a star gives off and the light capacity a flashlight gives off are so diffrent it would be extremely hard to compare. As you can see, a flashlights light travels only so far with visible light. Example: If you shine a flashlight on a nearby tree it shines bright. If you shine the flashlight on a far away tree the light is dim. If you flash the light towards a tree very far away you cannot see the light. Same applies for stars. Except they give off way more light so the light travels farther in visibility. Earth, being the tree.

[evilbutterfly]

Re: Dissipation of light?

As for Verrucket's example about light splitting: if you have glasses, you've probably noticed that if you look out the edges of your glasses you'll see double of an object. One image is the object as seen with the light going straight to your eye, the other is where some of the light hits your glasses and gets curved into your eye. Think of a black hole as just a bit thing to mess with the light that goes through.

And uh, don't black holes have such huge gravity that light can't escape, hence them being "black"? That's what they tell me in school, but just from what Guido said (and from how the always dumb things down) I'm guessing there may be way more to it...

For the flashlight thing: you're thinking of the light from the flashlight or star as one "thing" of light. What you need to realize is that the beam coming out of a flashlight or anything is a bunch of light waves all coming out of the same point. Each individual lightwave goes on and on and on, but they spread out from each other. The light itself isn't dimming, but the various waves are getting farther apart. For example, a good laser (not some crappy cheap laser pointer, a REAL laser) can shoot a concentrated beam of light to one point far far away without it dissipating, because the light waves are all directed out the same way to make sure the light stays in one solid beam. That's why a laser's concentrated energy beam is so stronger whereas like, a microwave, which has energy flying around all over, is so weak.

[Grandiagod]

Re: Dissipation of light?

For the flashlight thing:

The light is spreading out because of bulb (light is given off in all directions the only thing that is funneling it is the reflective metal on the inside of the flashlight) And since it spreads out, there is not enough light in any one spot to see it.

But there are some lights that go along ways without dispersing. Lasers anyone?

[Lightknight924]

Re: Dissipation of light?

Yes, but the Light amount in stars is much greater than a flashlight. If you've ever noticed a pocket lasers light only shines so far. Or a snipers light on the scope. So why can't this apply to a star? For a flashlight or laser, a light beam only travels in the direction you point it. For a star, the light shines in every direction. So, I still stand by with what I said. Light is only visible for a certain distance depending on the amount of light that is given off. We can't see every star in the universe. Only ones close enough to the Earth.

So eb, your saying that the light waves are spreading apart which makes them less visible. That makes sense proving light doesn't dissolve. Except that still proves me right.

[Tokzic]

Re: Dissipation of light?

So why can't this apply to a star?

It does.

Look at the night sky and some stars will be dimmer than others. Also, if you stare at the stars of the night sky, you will not damage your eyes exactly like you will if you stare at our local one.

[GuidoHunter]

Re: Dissipation of light?

The fact that we can't see every star in the universe isn't because the light isn't strong enough or anything. Light might not reach a source because it might be absorbed by obstructions or its path changed by intense local gravitational fields.

Light, you say you stand by what you said, but what did you say?

And eb, if I'm understanding you correctly, light doesn't exactly work that way. You can consider a light source to be a continuous spectrum. That is, as light goes further out radially, you're not going to have gaps between photons.

It has a property like that of sound, in which every particle vibrated by the sound becomes a new source for the sound. If you have a friend stand in front of you, facing away, you can hear him talk because even though his voice projects the sound forward (more or less, I know there's some minor vibrations from his neck and whatnot), the air that's vibrated projects it out of his mouth, to the side, and then back to you. Light somehow does the same thing.

--Guido

http://andy.mikee385.com

[Lightknight924]

Re: Dissipation of light?

Guido, I said that light is only visible for a certain distance depending on the amount of light that is given off. We can't see every star in the universe. Only ones close enough to the Earth because they give off a certain amount of light. So ofcourse farther stars appear more dim in the sky during the night. Then, eb said that light doesn't dissapear, it spreads out. So the waves are too far apart to make a visible ray of light. Even though the light waves are still there. That makes sense.

Light and sound are both energy waves aren't they? So they should do the same thing. And can energys be pulled in by gravity? Even a small ray of light?

[chickendude]

Re: Dissipation of light?

LK,

they are both types of waves, but they aren't both in the same category.
It's all semantics, like Guido said.

Light is just pure energy, photons travelling. They don't need a medium.
Sound is just vibrations at certain frequencies that can be detected by the ear.
Sound's energy is transferred, through a medium, by neighboring atoms bumping into each other repeatedly, pushing kinetic energy into the next.

Light IS energy. Sound is just the vibration from energy being passed from particle to particle.

Mass is directly affected by gravity. Sound is only the vibration. The waves themselves aren't pulled in by gravity.

Photons of light ARE affected by gravity (not directly, but through the curvature of spacetime).

Also,
Light is usually emitted in every direction from a source (stars flashlights, etc)
What happens, is that it spreads out. Each individual ray doesn't become weaker, you just see less with your eye.

Light from stars travel continuously. Only the light from the star that pointed DIRECTLY in the direction of the earth is seen by us. This is a very small amount of light, which is why stars appear so small.
We can't see every star in the universe because either
a) It's been blocked by some kind of stellar matter (huge gas clouds, etc.)
b) It's farther than 14-20 billion light years away. The universe isn't that old. Light hasn't made it to earth yet.
NOT because the light dims as it goes too far. The individual rays don't dim. They just spread out over a larger area. The ones that are going for earth are STILL going for earth. You can still see those ones. Usually thats sufficient.

[Lightknight924]

Re: Dissipation of light?

Yes, but I said that the waves of light spreading out makes them appear more dim to people. Since they are far apart. I understand that they don't lessen.

[GuidoHunter]

Re: Dissipation of light?

And I said that they don't spread out. If they did, one would expect a pattern similar to a diffraction pattern, but with only a single, unobstructed source. That just doesn't happen.

--Guido

http://andy.mikee385.com

[Lightknight924]

Re: Dissipation of light?

So then what makes them less visible?