Is Light Matter or Energy?

[Dixon Carter Lee]

I was asked that last night, and damn me if I didn't have a good explanation. I know light has weight, therefore it's matter. But since it doesn't conform to any of the definitions of a solid, liquid or gas, it also has some properties of energy.

I think Light's been defined as a "wave", whatever that is. I'm too tired to surf the net. Anyone have a good ONE SENTENCE definition of the light's scientific assignation?

 

[Weevil]

Science....hurt....Hulk's....head.

 

[riff]

Matter and energy are two sides of the same coin.

simple as it gets

 

[NoRegrets]

Only her hair dresser knows for sure

It's the answer to: who killed schrodinger's cat.

It depends!!!

 

[seXieleXie]

I was asked that last night, and damn me if I didn't have a good explanation. I know light has weight, therefore it's matter. But since it doesn't conform to any of the definitions of a solid, liquid or gas, it also has some properties of energy.

I think Light's been defined as a "wave", whatever that is. I'm too tired to surf the net. Anyone have a good ONE SENTENCE definition of the light's scientific assignation?

light is energy. light is radient energy released when excited electrons fall back to their ground state. light is not matter. light does not have mass.

 

[Dixon Carter Lee]

See, here's the problem: I'm pretty sure light does have mass. I know for sure that it has weight.

Matter and Energy are two sides of coin -- that's a given. But light doesn't fit either category well. It's more of an "event" than matter or energy.

 

[seXieleXie]

See, here's the problem: I'm pretty sure light does have mass. I know for sure that it has weight.

Matter and Energy are two sides of coin -- that's a given. But light doesn't fit either category well. It's more of an "event" than matter or energy.

http://math.ucr.edu/home/baez/physics/Relativity/SR/light_mass.html

Does light have mass?
The short answer is "no", but it is a qualified "no" because there are odd ways of interpreting the question which could justify the answer "yes".

Light is composed of photons so we could ask if the photon has mass. The answer is then definitely "no": The photon is a massless particle. According to theory it has energy and momentum but no mass and this is confirmed by experiment to within strict limits. Even before it was known that light is composed of photons it was known that light carries momentum and will exert a pressure on a surface. This is not evidence that it has mass since momentum can exist without mass

 

[riff]

See, here's the problem: I'm pretty sure light does have mass. I know for sure that it has weight.

Matter and Energy are two sides of coin -- that's a given. But light doesn't fit either category well. It's more of an "event" than matter or energy.

Definitions are important, aren't they?

What is an event? I got too much incoherence.

lexie's definition is quite literal. I was mistaking light for energy. Yes, I think event is a good way to describe it.

 

[P. B. Walker]

This is the last place I'd expect to see a question like this. LOL. It's a sexy topic though. My geeky side just got all perked up... I think he has a boner... shhhhh.

- PBW

 

[Guest]

Light is composed of electromagnetic radiation wavelengths. And radiation is the emission of energy. So, I'll deduce that light is catergorized as energy.


Or maybe not? Heh.
I need to go back to school.

 

[seXieleXie]

P.B. -

DCL - I don't want to sound bitchy or like i'm tooting my own horn, so please don't take what i'm about to say like that. i'm a science major at a respectable college. i've complete intro level bio, chemistry and physics. i know that light is a form of energy released by excited electrons returning to their ground state. light is energy, and though energy does not have a very exactly definition because it is not completely understood, energy does not have matter.

 

[Dixon Carter Lee]

Bitch.

LOL Well, as long as we're touting our resumes, I'm a member of MENSA.

I was struck by the "light exerts a force upon a surface" thing. I think this is crucial. Does that count as "weight"?

I think I'm leaning towards the "energy" definition, but in a qualified sense, since light has properties other energy does not.

An "event" is just a cozy way of describing phenomenon that can't really be modeled because it often involves other dimensions or a description of the properties of space-time (like the Big Bang, a Black Hole, or Dick Clark).

 

[lavender]

 

[Dixon Carter Lee]

Sure it does. You think having an I.Q. in the top 2% of the country is something to sneeze at, Missy? LOL

And in the three years I've been here I think I've mentioned it once before. What are you doing, taking notes?

 

[seXieleXie]

blah. i was just trying to establish my background in the subject.

weight is the gravitational pull of the earth. a body doesn't need mass to have weight.

 

[Dixon Carter Lee]

Yes I know. But I'm trying to establish the properties of energy, not matter. Does energy have "weight"?

 

[riff]

light is process?

not the fire, the burning?

 

[lavender]

 

[Dixon Carter Lee]

Well, sorta. Light comes from a source (the "fire"), but we perceive it as a carrier of that source's information (the "burn").

Actually, that brings up an interesting question. If the Big Bang created light, as it probably did, was that light (energy) converted into matter to form a part of the Universe? Are we the stuff of photons, as well as stardust?

 

[Dixon Carter Lee]

Lavender, honey, you're being silly. You're treating banter as debate. Let it go.

 

[seXieleXie]

a little light physics and some relativity:

weight, aka the earth's gravity, acts upon the total energy of a physical system. basically all the different kinds of energy (potential, kinetic, etc) taken together contribute to the total gravitational force that a body feels (read: it's weight). normally the mass of the body is the biggest component of it's weight. light doesn't have any mass though. it is 100% pure electromagnetic energy. gravity then acts upon this electgromagnetic energy, which is defined by the equation E = h*c/wavelength where c = speed of light and h = plancks constant.

if you want you can give light "effective" or "equivalent" mass using the famous E = m c^2 . that's probably what you were thinking of when you made this post. that concept of mass is relativistic mass. the mass you learn about in newtonian physics is not the same kind of mass.

 

[freescorfr]

I have no bone to pick with you. This is my normal reaction to anyone who throws that around

And Here's mine

Our intelligence takes many different forms, and each person has a different balance between the various abilities. These forms, in the view of Howard Gardner, include linguistic, logical, spatial, kinaesthetic (movement), musical, interpersonal and intrapersonal (self-knowledge). Many other viewpoints on this issue also exist, one of the most interesting linking emotions into the equation (see Daniel Goleman's book 'Emotional Intelligence'), but we can also add 'Sensual Intelligence', awareness of our wider sensual world, to the list along with all our subconscious and unconscious functions. Suffice it to say that in any complex system, such as the mind, multiple different abilities will coexist, all equally valuable in the right circumstances or context.

 

[Dixon Carter Lee]

Thanks, Lexie, that's all clear. You're right, I'm often compelled to the e=mc2 equation when I think of light's properties, because it involves motion. Motion (or speed) adds to a body's mass, so I often think of light (the fastest thing on two legs) as having an "infinite mass", which should be right, even if it's not. So many things with light "should" be right (like the idea that light can pick up speed if it's on a moving train) when they're not. Funny little thing, light.

What else is classified as electromagnetic energy? (The earth's magnetic field?) I still feel light is in a category of its own. It's bent by gravity and can be slowed down, like other forms of energy, but what differences do you see between it's properties and others?

 

[seXieleXie]

electromagnetic energy (also called electromagnetic radiation):

http://www.princeton.edu/~ehs/laserguide/spectrum.jpg

 

[christo]

I always thought that light was defined as behaving as both a wave and a particle. That was the whole quantum mechanics thing. Personally, I think all the physicists got together and said, "Let's face it, we don't know WHAT the fuck it is," and banded together to say, hey, it's both! Probably when you get your applied physics degree they pull you aside and say, "Now you're part of the secret society. Don't go blabbing about light, or you'll never see it again. In wave or particle form".