Light

[Trigshot]

Well it looks like you guys pretty much handled most of it, light is made up of small packets of energy called photons, and these photons behave similar to an electron. Because of E=MC^2, obviously has no mass, it is composed entirely of energy. I believe the photons have a spin, which is what causes their wavelike behaviors. Electromagnetic waves do not need a medium in which to travel, but sound waves do. Radio waves, not to be confused with sound waves, are electromagnetic waves.

Light is affected by gravity because of the curvature of space apparent in the presence of gravity.

 

[JacobEvans]

First off... JB you are banished from posting on my topics!

If photons had mass, they would be unable to travel at the speed of light; otherwise they would require infinite energy to accelerate them to that speed.

Well I believe it has mas in that it has a quantifiable amount of energy, so With e=mc^2 we could calculate a mass.

but I don't believe it's in the 'form' of a regular particle with mass, it's just that all energy has a quantifiable mass.

Am I wrong anyone?

 

[diagoras54]

Well I believe it has mas in that it has a quantifiable amount of energy, so With e=mc^2 we could calculate a mass.

but I don't believe it's in the 'form' of a regular particle with mass, it's just that all energy has a quantifiable mass.

Am I wrong anyone?

Energy and mass are interchangeable, but having energy does not necessarily equate to having mass. One can be converted into the other, but they aren't exactly different shades of the same thing. e=mc^2 actually indicates that for a mass to travel at the speed of light would require an infinite amount of energy; the closer to c an object travels, the more energy is required to accelerate it. We can accelerate fundamental perticles to 99.99% the speed of light, but only massless particles to the speed of light.

 

[Aught3]

Doesn't e=mc^2 just tell you how much energy you can get if you converted all of an object's mass, and vice versa? (nvm diagoras answered)

I have to compliment diagoras for the excellent replies, you are explaining something very complicated quite well, imo.

I think I am following most of it, the only thing left is the idea of light 'being in two places at once' is that what actually happens, or is that the photon becomes more diffuse and partially goes through one hole and partially goes through the other?

I believe the photons have a spin, which is what causes their wavelike behaviors.

If I remember correctly, spin is that funny concept that I don't remember correctly. Would you mind elaborating on it for me?

 

[JacobEvans]

^ I never could understand spin either.

 

[diagoras54]

Doesn't e=mc^2 just tell you how much energy you can get if you converted all of an object's mass, and vice versa? (nvm diagoras answered)

I have to compliment diagoras for the excellent replies, you are explaining something very complicated quite well, imo.

I think I am following most of it, the only thing left is the idea of light 'being in two places at once' is that what actually happens, or is that the photon becomes more diffuse and partially goes through one hole and partially goes through the other?

If I remember correctly, spin is that funny concept that I don't remember correctly. Would you mind elaborating on it for me?

Thanks. Physics is my forte; I've been pwned on math on here, but conceptual physics gives me orgasms.
It's not that the particles are in two places at once, it's that the peaks and troughs of the wave function cancel each other out, creating blank patches, but where the peaks meet and the troughs meet we find a strip of particle indictations. Basically, there's a higher probability of finding the particle at the peaks and troughs, and no probability of find it where the waves cancel each other.
Spin is actually a property of particles; it's extremely complicated, like that the value can be half an integer, but the value of the spin determines what type of particle it is, or what the behaviour of the particle is.

 

[Trigshot]

If I remember correctly, spin is that funny concept that I don't remember correctly. Would you mind elaborating on it for me?

Certainly. I'm unsure if it applies to light, but "spin" is the idea that a particle as small as an electron (which is highly energetic anyway, similar to light), has a spin designated to it, so that as it moves through space, it creates a wavelike motion, unless acted upon by another force, usually the force of the nucleus holding it in place. Spin is designated in terms of numbers. Spin 1 would be an item like your head. Spin it 360, and it looks the same. However, Spin 2, would be an item such as a playing card, with only 180 degrees it would appear the same. Electrons and many other elementary particles are supposed to have a spin of 1/2, which means they must be spun twice before returning to their original appearance.

http://www.youtube.com/watch?v=ojBqvvTowa4

 

[diagoras54]

Certainly. I'm unsure if it applies to light, but "spin" is the idea that a particle as small as an electron (which is highly energetic anyway, similar to light), has a spin designated to it, so that as it moves through space, it creates a wavelike motion, unless acted upon by another force, usually the force of the nucleus holding it in place. Spin is designated in terms of numbers. Spin 1 would be an item like your head. Spin it 360, and it looks the same. However, Spin 2, would be an item such as a playing card, with only 180 degrees it would appear the same. Electrons and many other elementary particles are supposed to have a spin of 1/2, which means they must be spun twice before returning to their original appearance.

http://www.youtube.com/watch?v=ojBqvvTowa4

That's a good explanation. It applies to all fundamental particles, light included.

 

[Trigshot]

I wasn't quite sure on that... Agreed, though, Physics is where I'm at home, just not on a massive scale. I prefer the theoretical physics, string theory, relativity, etc.

 

[JacobEvans]

Damn it I said layman's terms!! :lol: :lol: :lol: :lol:

 

[Trigshot]

Damn it I said layman's terms!! :lol: :lol: :lol: :lol:

What don't you understand? I can simplify it for you...

 

[diagoras54]

Damn it I said layman's terms!! :lol: :lol: :lol: :lol:

That's about as layman as it gets in this field. Brian Greene's The Fabric of the Cosmos provides excellent explanations for all of these concepts.

 

[Sparky]

Physics? Where was I when this thread was started?

*Sigh*

String theory adds another level to the matter/energy debacle doesn't it? In that all matter is basically composed of "strings" that have a certain wavelength or something. It also says there are 13 dimensions or so and this explains gravity's weakness in the 4 dimensions we experience. Or is that another theory - Supersymmetry maybe? No, wait that is about all particles having a supersymmetric partner with opposite spin or something. I can't recall - it all gets messed up in my head.

Maybe someone could have a go at explaining some of these theories to me more fully if they know much about them or have the time or maybe they could at least match up the random bits of information I spouted.....

I'm just a university engineering student who is pretending to know about physics..... I guess given that I want to do nanotech I should really have a better idea of quantum mechanics but...well.... :roll:

I am much safer sticking to my maths which I am actually good at

 

[Trigshot]

/sigh

There are supposed to be 10 dimensions of spacetime.
1. A Line. X

2. A branching line, flat surface. X, Y

3. Three dimensional space with no time. X, Y, Z.

4. Time as a line. X, Y, Z, T

5. Time with branching alternate timelines. X, Y, Z, T, T2

6. Time with a line that may jump to other lines. (time travel) X, Y, Z, T, T2, T3

7. Every possible timeline of our given universe from the same beginning to the same ending, expressed as a line of universe timelines. X, Y, Z, T, T2, T3, U1

8. The branch from a set of universe timelines, where each copy of our universe may not be ours, for example, universes that do not begin with a big bang. X, Y, Z, T, T2, T3, U1, U2

9. The jump from one universe with a given set of timelines and beginnings to another. X, Y, Z, T, T2, T3, U1, U2, U3

10. Every possible universe with every possible timeline with every possible beginning with every possible set of governing laws, all compressed into a single point.


Supersymmetry is the theory that every particle at the elementary level has a twin particle that is its partner in spin. Theoretically a particle with spin 1/2, should have a twin particle with spin -1/2. Unfortunately, there is still little to no evidence that supersymmetry exists.
http://en.wikipedia.org/wiki/Supersymmetry

 

[diagoras54]

If we're going into string theory, this is going to get messy. It's probably the least understood theory in modern science, although the term theory is used loosely; there's no experimental evidence for it yet, and because of that the number of possible hypotheses is enormous. Your ideas about it are right, but until we have some definitive observations we can't confirm whether superstrings, basonic strings, or M-theory, among others, are correct. They are by no means in agreement, and I'm definitely in no condition to explain each individually. I also doubt whether the strings which create particles would have any effect on the wave behaviour of the particle, as the same types of particles can have different wavelengths.

 

[Sparky]

/sigh

Sorry :?

There are supposed to be 10 dimensions of spacetime.
1. A Line. X

2. A branching line, flat surface. X, Y

3. Three dimensional space with no time. X, Y, Z.

4. Time as a line. X, Y, Z, T

5. Time with branching alternate timelines. X, Y, Z, T, T2

6. Time with a line that may jump to other lines. (time travel) X, Y, Z, T, T2, T3

7. Every possible timeline of our given universe from the same beginning to the same ending, expressed as a line of universe timelines. X, Y, Z, T, T2, T3, U1

8. The branch from a set of universe timelines, where each copy of our universe may not be ours, for example, universes that do not begin with a big bang. X, Y, Z, T, T2, T3, U1, U2

9. The jump from one universe with a given set of timelines and beginnings to another. X, Y, Z, T, T2, T3, U1, U2, U3

10. Every possible universe with every possible timeline with every possible beginning with every possible set of governing laws, all compressed into a single point.

My bad. Don't know where I got 13 from....

Supersymmetry is the theory that every particle at the elementary level has a twin particle that is its partner in spin. Theoretically a particle with spin 1/2, should have a twin particle with spin -1/2. Unfortunately, there is still little to no evidence that supersymmetry exists.
http://en.wikipedia.org/wiki/Supersymmetry

Ah. I read that if you ask any scientist what they want the LHC to find is evidence for Supersymmetry. Would you agree with this? It would be pretty sweet! ^^

 

[Sparky]

If we're going into string theory, this is going to get messy. It's probably the least understood theory in modern science, although the term theory is used loosely; there's no experimental evidence for it yet, and because of that the number of possible hypotheses is enormous. Your ideas about it are right, but until we have some definitive observations we can't confirm whether superstrings, basonic strings, or M-theory, among others, are correct. They are by no means in agreement, and I'm definitely in no condition to explain each individually. I also doubt whether the strings which create particles would have any effect on the wave behaviour of the particle, as the same types of particles can have different wavelengths.

Glad I was right about something
Hmmm... Yes we need a bit more evidence about the rest of the Universe to make progress now don't we? A lot of theories - little evidence.....

 

[Pulsar]

Light has particle-like properties because it has momentum. There are several phenomena that can only be explained if you describe photons as particles: the photoelectric effect, Compton scattering, the Planck curve of a blackbody,...

Also, photons don't have rest-mass, but they do have energy. So you can attribute some sort of relativistic mass m = E/c^2 to photons. Also, because light has energy, radiation generates a gravitational field, like ordinary matter.

 

[JacobEvans]

The layman's term thing was a joke.

But, I still don't understand how spin makes things appear as a wave.

 

[Chirios]

Is space not a vacuum? Can radio waves not be transmitted through space? Are radio waves therefore particles?

No and yes. All things can behave as a wave or a particle depending on the situation that they're in. For example, if a human was moving at the correct speed and went through a slit the right size (tee hee) they would diffract.