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| Particle and Theoretical Physics [message #156370] |
Wed, 25 May 2005 11:06  |
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Javaxcx
Messages: 1943
Registered: February 2003
Location: Canada, eh?
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General (1 Star) |
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I'd like to open the ball park to those of us which are scientificially inclined. Myself and Doitle often discuss particle theories trying to come up with aspects of a unified theory that works liberally with String Theory as a basis.
We have as of late been discussing the nature of photons and how they can possibly exist at all. According to relativity, such things like solar cells shouldn't even work because photons are acclaimed to have a 0 mass.
E=mc^2 concludes that because of this, they have no energy, thus cannot give energy to the cell. But this is not experimentally true. We can quite easily turn on a light with a solar cell. This therefore entails that light, photons, carry some kind of apparant mass. Whatever that is, we don't need to really specify, because the mere fact that it is there is what it is important.
At any rate, the topic is open to discussion in the crowd, so share your thoughts.
Sniper Extraordinaire
Read the FUD Rules before you come in and make an ass of yourself.
All your base are belong to us.
You have no chance to survive make your time.
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| Particle and Theoretical Physics [message #156565] |
Thu, 26 May 2005 05:32  |
Jzinsky
Messages: 339
Registered: June 2004
Location: Warrington
Karma: 0
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| DaveGMM |
I didn't think that there was a test that proved it was both.
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Well you can't stop light, I figure at that speed it either bounces off (reflection) or gets absorbed into whatever it hit (causing colour) thus you cannot stop light, but I guess the theory is ifyou could, it would be a particle with a mass on a micro mathematical scale..
I dropped out of physics at 16..
No flashy signature..
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| Re: Particle and Theoretical Physics [message #156600] |
Thu, 26 May 2005 09:07 |
Kanezor
Messages: 855
Registered: February 2005
Location: Sugar Land, TX, USA
Karma: 0
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Colonel |
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| Jzinsky |
| DaveGMM |
I didn't think that there was a test that proved it was both.
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Well you can't stop light, I figure at that speed it either bounces off (reflection) or gets absorbed into whatever it hit (causing colour) thus you cannot stop light, but I guess the theory is ifyou could, it would be a particle with a mass on a micro mathematical scale..
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If you could not stop light, then nothing would be absorbing light, correct? In a way, that's true... because the things that absorb light become hot. A black surface absorbs more light than a white surface, and a black surface will become equally more hot than a white surface.
Also, you're only partially correct when you say that absorbing light causes color; color is caused when one part of the spectrum is absorbed while the other part (the part you see; the color you see) is bounced off.
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| Particle and Theoretical Physics [message #156653] |
Thu, 26 May 2005 12:49 |
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Javaxcx
Messages: 1943
Registered: February 2003
Location: Canada, eh?
Karma: 0
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General (1 Star) |
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Remember, light can be characterized as both a particle and a wave. That being said, we can measure energy in two forms.
E=mc^2 works wonders for stuff with mass. But conversely, E=hf works pretty well for stuff with no mass. You can't use them interchangibly because you'll always get a 0 answer for your energy outputs.
For example, if you were to say that because E=mc^2 and E=hf, then mc^2=hf. But mass doesn't have frequency (for the sake of argument) and waves don't have mass. Therefore, since h and c are always constant, your overall answers are going to be 0 net energy.
What it really comes down to, with my understanding of the photon, is that it has an apparent mass when travelling at c. Now, I know what you physics geeks are thinking, "it's impossible to have a mass and travel at c". But you can presuppose an apparent one using momentum theory. Remember, when dealing with relativity, p = E/c. But p also is mass x velocity.
Because of this, we can rearrange the whole system and solve for the apparant mass of a photon. That is;
m = hf/c^2
This should look pretty familiar. It's the combination of E=mc^2 and E=hf.
The trick is: E=mc^2 relies on one thing. That the object with mass, m, is withOUT momentum. Have you ever seen a wavelength of frequency 0? Of course not. Now, since I'm fairly sure that all of you know that the speed of light is consistent regardless of frame of reference, we make the assumption that light always has momentum when travelling in spacetime. This means that light ALWAYS has an "apparent" mass because of the equation aforementioned. Now, if light weren't a wave either, then it wouldn't have a frequency, wouldn't have mass, and wouldn't have any energy. But light clearly does have momentum! That is important!
I'm sure all of you at one time or another saw those little motors that were driven by light's momentum. They were little cardboard fans, one side was black, one was white, and it was balanced on a pin in a vacuum that looks a lot like a lightbulb. When white (and just about only white light, I'm not sure about blue) was shot at the BLACK side, it started to spin. I'm also sure your teachers told you that the light is absorbed by the black and reflected off the white. This is a perfect model proving that light must have energy AND momentum in it. And thus, it has an apparant mass as well.
Of course, this is just my understanding of it. Feel free to critisize or clarify.
Sniper Extraordinaire
Read the FUD Rules before you come in and make an ass of yourself.
All your base are belong to us.
You have no chance to survive make your time.
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| Particle and Theoretical Physics [message #156657] |
Thu, 26 May 2005 12:58 |
Spoony_old
Messages: 1105
Registered: December 2004
Karma: 0
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General (1 Star) |
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| Javaxcx |
Remember, light can be characterized as both a particle and a wave. That being said, we can measure energy in two forms.
E=mc^2 works wonders for stuff with mass. But conversely, E=hf works pretty well for stuff with no mass. You can't use them interchangibly because you'll always get a 0 answer for your energy outputs.
For example, if you were to say that because E=mc^2 and E=hf, then mc^2=hf. But mass doesn't have frequency (for the sake of argument) and waves don't have mass. Therefore, since h and c are always constant, your overall answers are going to be 0 net energy.
What it really comes down to, with my understanding of the photon, is that it has an apparent mass when travelling at c. Now, I know what you physics geeks are thinking, "it's impossible to have a mass and travel at c". But you can presuppose an apparent one using momentum theory. Remember, when dealing with relativity, p = E/c. But p also is mass x velocity.
Because of this, we can rearrange the whole system and solve for the apparant mass of a photon. That is;
m = hf/c^2
This should look pretty familiar. It's the combination of E=mc^2 and E=hf.
The trick is: E=mc^2 relies on one thing. That the object with mass, m, is withOUT momentum. Have you ever seen a wavelength of frequency 0? Of course not. Now, since I'm fairly sure that all of you know that the speed of light is consistent regardless of frame of reference, we make the assumption that light always has momentum when travelling in spacetime. This means that light ALWAYS has an "apparent" mass because of the equation aforementioned. Now, if light weren't a wave either, then it wouldn't have a frequency, wouldn't have mass, and wouldn't have any energy. But light clearly does have momentum! That is important!
I'm sure all of you at one time or another saw those little motors that were driven by light's momentum. They were little cardboard fans, one side was black, one was white, and it was balanced on a pin in a vacuum that looks a lot like a lightbulb. When white (and just about only white light, I'm not sure about blue) was shot at the BLACK side, it started to spin. I'm also sure your teachers told you that the light is absorbed by the black and reflected off the white. This is a perfect model proving that light must have energy AND momentum in it. And thus, it has an apparant mass as well.
Of course, this is just my understanding of it. Feel free to critisize or clarify.
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Remember, it's... actually, no, I won't go there.
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| Re: Particle and Theoretical Physics [message #157300] |
Sun, 29 May 2005 08:09 |
Jzinsky
Messages: 339
Registered: June 2004
Location: Warrington
Karma: 0
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Recruit |
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| Kanezor |
| Jzinsky |
| DaveGMM |
I didn't think that there was a test that proved it was both.
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Well you can't stop light, I figure at that speed it either bounces off (reflection) or gets absorbed into whatever it hit (causing colour) thus you cannot stop light, but I guess the theory is ifyou could, it would be a particle with a mass on a micro mathematical scale..
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If you could not stop light, then nothing would be absorbing light, correct? In a way, that's true... because the things that absorb light become hot. A black surface absorbs more light than a white surface, and a black surface will become equally more hot than a white surface.
Also, you're only partially correct when you say that absorbing light causes color; color is caused when one part of the spectrum is absorbed while the other part (the part you see; the color you see) is bounced off.
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Well the point really was that you can't grab hold of a particle of light because the only way to actually stop that particle would be to absorb it into some other object and thus rendering it unremoveable.
Yeah it's both, but actually being able to prove it 100% for definate for all to see is in the realms of science fiction, unless there's something I don't know about?
No flashy signature..
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