Light

[lobices]

As we know, what`s light?
Is light, matter or not?
If light is matter how can the light to pass through the glass, for exemple?
If light is not matter, what is it? And if it isn´t matter how can the light deflect or reflect?

Is the light that "make" the heat or is heat (a source of) that make the light?



If the light is not matter how can a thing that dont exist, travel in space 300.000 kms/sec.? If it is not matter there are nothing travel, aren`t it?

sorry by the silly questions but its true...what`s light?

regards

quim

[paperclip]

According to the standard model (afaik) light exists as a wave-particle duality. Sometimes it's a wave, sometimes it's a particle. To get light to travel through a vacuum and eliminate aether, the particle theory became widely accepted.

Light isn't matter, even as a particle (photon) because it carries energy and momentum, but has no mass.
Being able to pass through glass is *sorta* tricky, because not all light passes through glass. The visible spectrum does, yes, but ultraviolet light doesn't. Gamma rays are absorbed by mostly everything that exists. So even though something's transparent, that doesn't mean all light passes through it, just some. Like x-rays passing through flesh but not bone.
It's the source of the heat that makes the light.
For deflection or reflection, it is easier to think of light as a wave. Any wave passing though a medium under certain conditions will deflect or reflect.

I think that about does it.
For more information I would suggest www.howstuffworks.com and www.particleadventure.org (not completely sure if the second link is correct).

-paperclip

[Tormod]

Hi quim!

paperclip is right and his links are good. That light has a "dual" nature has been known for a long time, but it was not until the end of the 19th century that physicists began to suspect that their particle and wave "disagreement" in fact was just two sides of the same coin.

In 1905, Einstein showed that light can behave as a particle with energy, known as the photon. However, the way light travels is wave-like in nature, thus there exists a phenomenon which has been named the "wave-particle duality".

You can read more about it here.

Paperclip mentions the ether theory. How scientists came to understand that the ether did not exist is indeed an interesting piece of science history. You can read a brief notice on what it is and how it came into existence here. I think the note is not compete - the belief that space was not empty existed long before Faraday and Maxwell. Newton had an ether theory which was important for his work on optics. It was Isaac Newton who discovered that when light passes through a lens the light is broken down into its constituent colors (thus proving that white light is a mixture of many wavelengths).

Even today, there are still scientists who believe there is a form of ether permeating the Universe, but modern physics does not need it. The empty vacuum of space is not really empty, it contains enourmous amounts of potential energy and virtual particles pop in and out of existence all the time, borrowin energy from the vacuum. Here is an interesting slide show which describes it: Physics of Vacuum Energy: Gravitation of the Casimir Effect.

I also found this interesting page about early theories of light and how it moves - EARLY IDEAS OF LIGHT.

Tormod

[Kelddath]

Paperclip: How come can a particle have an energy and momentum and have no mass?

[Sharky]

This is how the light spectrum works people....

Light has a begining point where it is born into existance and has an ending point of non-existance. Think of black and white as both being the absence of color. If white and black are the absence of color then color is the reflection of the gama's off of the ultra violet. Lightning travels at three different speeds at one point in time. This is part of my theory called Warp Mechanics. When lightning strikes there is a pre-determined path which means that the departure point and the destination point are pre-existant. This type of motion is Warp speed or the speed of light cubed. Then the flow of electrons follow the pre-determined path to the destination point. This type of motion is the speed of light squared. The visible part of the lightning (what we can actually see) is traveling at the speed of it own existance, meaning if it's still in motion and has not been absorbed, intercepted or reflected then it would remain in motion until one of the said events occurs. This is how it has to work according to the mechanics behind the strucure of a sphere. A sphere is both existant and non-existant at the same point in time. This is because both the sphere and it's center are equal to 360 degrees cubed. Check out my posting in the general discussions forum. It is titled Warp Mechanics.

[anonymous]

actually light is energy thats always existant, it just converts into different forms,.. like when the photon hits the electron the electron absorbs the energy, will jump up to a higher energy level and then drop back down though when it drops back down it will releases a photon therefore the photon is "relayed" through the atom, or atoms, or glass or what not. some electrons absorb and release the energy while some don't, therefor making up the diffetent transparencies of different materials. when a photon is released from the electron it is released at a certain frequancy (wavelength) and according to that frequency (color) you could find out the type of material it was released from. anyway, I hope my 2 cents contributes.
_russ.

[Noah]

Thanks for that reply, Russ! That is what we want the anonymous posting for, not the spam that it has been used for quite a bit recently. Your input is appreciated.

Yes, according to the law of conservation of energy, which states that within a closed, isolated system, energy can change form, but the total amount of energy is constant Energy cannot be created nor destroy. This, of course is not completely true as energy is "created" from matter during a nuclear reaction, but is true in normal situations. Normally it just changes form. Like a car engine. Chemical energy (in the fuel) is converted into heat and kinetic energy, and some of that kinetic energy is converted into electrical energy via the alternator. Some of this in turn can be turned back into chemical energy if say you have a charger for your cell phone in the vehicle.

Noah

[AstroRuss]

Noah,
I'm not a proffesional mind in the matter yet so correct me if I'm wrong though are you sure the energy is created? ...Is it not that it occurs in the form of a quantum fluctuation? or some sort of "total sum of energy" fluctuation?
_Russ.

[Tormod]

AstroRUSS - welcome to our forums!

I think that when we talk about "creation" of energy in a quantum physics sense, we do indeed talk about fluctuations as you mention. But what actually happens is that energy is somehow "borrowed" from the vacuum, creating a tiny unbalance in the cosmic scale of things. This energy, which causes short-lived particles, quickly disappears again - which is why it is called a fluctuation.

<disclaimer>
Did this make any sense? My head is just so full of pollen these days...atchoo...
</disclaimer>

Tormod

[AstroRuss]

Why, Thank you. (:
_Russ.