What is light?... exactly?

Question

You know as in... in physics. Because according to a video of VSauce (I recommend him to you, pretty interesting videos) light is bent around a black hole, though I'll be leaving all of that apart because it's not so relevant. I'm going to go down right into it, if it is affected by its gravitational pull, then Light is matter, and if it is matter, then it is formed by atoms, and if light is atoms, then the sun and light-bulbs create (impossible) or attract and activate these particles, right? I have a huge mess in my head right now, and I would like if someone cleared it up.

Answer 1

Light follows the straightest possible path through space. It follows a path different than even the fastest material particle can follow through curved spacetime, by a factor.



Photons (individual, indivisible momentum packets of light) have no mass. We have checked. They are not made up of anything. If they individually contain enough energy, they can "rear end" a charge (like an electron) and produce a positron and an electron, or a proton and antiproton (with even more energy), but they themselves have no mass. Were you to fly away from the source of those energetic photons at very high speed, you could see those energetic photons as visible light, and no particle-antiparticle pairs would be created...



Light is an "impulse" (Newton) sent from one charge to another, a change in momentum.

Answer 2

Alright, gonna try this out. Not exactly my strong suit, but...



Einstein said that light has a sort of duality to it. It's got photons. Anyways, these can have a wavelength, but can also be particles at the same time. It's got mass too, which means it can be affected by gravity. Apparently you use E^2 = p^2 * c^2 + m^2 * c^4 or something. And for some reason, photons are not considered atoms, but particles.



I'm not sure if they told you in physics, but if you were to shine a straight line of light forwards, you'd notice that after a while, it wouldn't be at the same height, hence it's affected by gravity. It would be a very slight drop, but it's enough to prove that there's a downwards force at work.



Also, the sun's got a lot of elements, and these are constantly reacting with each other, producing radiation. Lots of waves come from the sun, like white light which hurts your eyes, and even UV rays, which is why they recommend you wear sunblock and all that. All part of the EM spectrum.



For lightbulbs, they all need a sort of electrical current. And lightbulbs usually have a metal which will conduct electricity (probably tungsten). They also have gases in them. My guess would be that there's a reaction in there somewhere involving electrons and this is probably what releases the lights.



Hope that helped!

Answer 3

Light, like everything else, is made up of wave packets...you are not going to understand this probably and that's OK--quantum mechanics is difficult to understand (especially without math).





Initially light was thought to be a wave because it had wave-like properties (i.e. Maxwell's equation as pointed out, diffraction, refraction, reflection, etc.). However it was then discovered, by Einstein, that sometimes light acts as a particle--coming in small packets which we call photons.



There is no wave-particle duality. Light (and all matter) is neither a particle nor a wave--it's something else. The Copenhagen interpretation of QM says that the wave packet (the photon) is actually a wavefunction--which if squared gives the probability that the light is at a certain spot in space. These wavefunctions obey the superposition principle (just like waves) so they sometimes produce wave-like phenomena (i.e. diffraction). On the other hand, light DOES come in packets (wave packets) which are photons. This means that even if you diffract light, it will STILL arrive, one at a time at the target, like a particle!



Edit:



Here is a video from Veritasium, which explains a little bit of why photons are neither waves nor particles: http://www.youtube.com/watch?v=GzbKb59my3U

Answer 4

Simply light is something that makes things visible or affords illumination. It’s actually electromagnetic radiation. Light is made up of little packets of energy called photons. Most of these photons are produced when the atoms in an object heat up. Light has both particle nature and wave nature. Photons, building blocks of light, sometimes act as particle but it has no mass. Light travels at 300,000,000 meters/second and it takes 8 minute to reach earth from sun.

Answer 5

Light is composed of particles called photons. Photons do not have mass, but they do have momentum. Black holes can bend light not because photons have mass (because they don't), but rather because black holes warp space according to General Relativity. Photons are fundamental particles. They are not atoms.



Just so that you don't see a contradiction between Andrew Smith's answer and mine:

Light has no rest mass, but it does have relativistic mass. It's a subtle distinction. Yes, for all intents and purposes, you can think of photons as having mass, but they cannot have rest mass, or else they would not be able to move at the speed of light.

Answer 6

If you are in high school physics, they will not cover light very much.



Originally, light was described by maxwell's equations which showed that light is made up of oscillating electric and magnetic fields that travel at the speed of light, c, hence the term "electromagnetic wave."

http://en.wikipedia.org/wiki/Electromagnetic_radiation

https://en.wikipedia.org/wiki/Maxwell%27s_equations



Then Einstein came along in 1905 with his famous photoelectric effect experiment which later won him the nobel prize. The photoelectric effect showed how light can behave like a particle and we now call the particles of light "photons". Photons are quanta of light, the smallest divisible amount of light possible. So this begs the question, is light a particle or a wave? It behaves like both depending on the situation, so you could call it both or neither.

http://en.wikipedia.org/wiki/Photoelectric_effect

http://en.wikipedia.org/wiki/Photon



So to answer your question, light is matter, but it is not made up by atoms. Atoms are made up of protons, neutrons, and electrons. Light is made up of photons. You can go further: protons and neutrons are made up of quarks. For a complete list, see the Standard Model.

http://en.wikipedia.org/wiki/Standard_Model

Answer 7

Your argument is way off in several points.



Light has mass. This doesn't mean that light is matter. And matter is not necessarily made of atoms.

ALL energy has mass. Light is a form of energy and hence has mass.

Als the sun creates light it loses mass.

No problem here.



But to answer the headline of the question Light is LIGHT!



Pure and simple. Everything else we use is a model of light which isn't necessarily a perfectly accurate description.