A square looks at light squared

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    Light Square
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Discussion Overview

The discussion revolves around the question of why the speed of light appears squared in equations relating mass and energy, particularly in the context of special relativity. Participants explore the implications of this relationship, its mathematical foundations, and the conceptual connections between light, speed, and mass.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • Some participants suggest that the squared speed of light is a mathematical necessity, arising from how the equations of physics are structured.
  • Others argue that the connection between light and mass-energy relationships is not immediately intuitive and question the significance of light in these equations.
  • A participant points out that for light, the energy equation simplifies to E=pc, raising questions about the absence of the squared term in that context.
  • There is a viewpoint that light's role is merely a consequence of it being the fastest entity in the universe, and not inherently tied to the mass-energy relationship.
  • Some participants express confusion over the reasoning behind certain claims and the formation of ideas in the discussion.
  • One participant emphasizes that the relationship between velocity and mass in special relativity is significant and involves the speed of light as an electromagnetic wave.
  • Another participant argues against the necessity of including photons in discussions of special relativity, suggesting that the theory could stand independently of them.

Areas of Agreement / Disagreement

Participants express a range of views on the relationship between light, speed, and mass. There is no consensus on the significance of the squared speed of light or the role of light in the equations, indicating ongoing disagreement and exploration of the topic.

Contextual Notes

Some participants highlight the potential limitations of using light in discussions of special relativity, suggesting that the theory could be understood without relying on photons. The discussion also reflects varying interpretations of the mathematical relationships involved.

tbco
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Third thread same topic.
Non physicist asks question-why speed of light squared?
Answers
Its the derivative that makes the equation work.
The speed of light is some kind of ultimate measuring device.
You are too stupid to understand.

I think the questioners are incorrectly phrasing what they actually want to know
We see the realtionship between Mass and Energy almost intuitively. What we don't see is
why light has anthing to do with it at all.( and don't answer-it doesnt,its the SPEED of light because saying light and the speed of light are not connected makes no sense) Some say it doesn't matter because the equation is so cool and valuable-who cares? Well, could it be that the next entire level of understanding of Physics could pivot on figuring out why these realtionships exist?
 
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tbco said:
Third thread same topic.
Non physicist asks question-why speed of light squared?
Answers
Its the derivative that makes the equation work.
The speed of light is some kind of ultimate measuring device.
You are too stupid to understand.

I think the questioners are incorrectly phrasing what they actually want to know
We see the realtionship between Mass and Energy almost intuitively. What we don't see is
why light has anthing to do with it at all.( and don't answer-it doesnt,its the SPEED of light because saying light and the speed of light are not connected makes no sense) Some say it doesn't matter because the equation is so cool and valuable-who cares? Well, could it be that the next entire level of understanding of Physics could pivot on figuring out why these realtionships exist?

This is utterly puzzling.

Please look at this FAQ entry:

https://www.physicsforums.com/showthread.php?t=511175

You'll notice that the FULL relativistic equation has another term to it! In fact, for light itself, its energy is only the other term, ie. E= pc.

So where's the "square" there? How come people are not "obsessing" over the fact that there is no square of the speed of light here?

Sometime, I just don't understand where and how people form their ideas.

Zz.
 
Last edited by a moderator:
ZapperZ said:
Sometime, I just don't understand where and how people form their ideas.

Zz.

+1 on that
 
tbco said:
Non physicist asks question-why speed of light squared?
What else could it possibly be? It has to have units of speed^2. It has to be composed entirely of universal constants. That makes it c^2.
 
tbco said:
Third thread same topic.
Non physicist asks question-why speed of light squared?

It's just the way the math works out. You might as well ask why the Lorentz transformation is set up as it is. Both are the result of how the rules of the universe interact with each other. Nothing more, nothing less.

What we don't see is why light has anthing to do with it at all.( and don't answer-it doesnt,its the SPEED of light because saying light and the speed of light are not connected makes no sense)

I'm sorry to say, but light has nothing to do with it. Light happens to travel at the maximum possible velocity in the universe. That's it. The fact that there is a maximum speed limit, along with other ways physics works, results in mass and energy being related by c2.
 
Drakkith said:
It's just the way the math works out. You might as well ask why the Lorentz transformation is set up as it is. Both are the result of how the rules of the universe interact with each other. Nothing more, nothing less.



I'm sorry to say, but light has nothing to do with it. Light happens to travel at the maximum possible velocity in the universe. That's it. The fact that there is a maximum speed limit, along with other ways physics works, results in mass and energy being related by c2.

OR everything - depending on how you look at it?
 
sophiecentaur said:
OR everything - depending on how you look at it?

You must be looking at it differently than I am.
 
Drakkith said:
You must be looking at it differently than I am.

I was looking at it from the point of SR. There is a strong link between velocity and mass and it involves the speed of light and light is an EM wave. You seem to be arguing against a very obvious association between those quantities. Or am I reading you wrong?
 
sophiecentaur said:
I was looking at it from the point of SR. There is a strong link between velocity and mass and it involves the speed of light and light is an EM wave. You seem to be arguing against a very obvious association between those quantities. Or am I reading you wrong?

I'm saying that there is a maximum speed limit in the universe, c, and that quantity is used in a variety of important ways in SR and other theories. It was my understanding that light itself simply happens to move at this velocity. Is that clearer?
 
  • #10
sophiecentaur said:
I was looking at it from the point of SR. There is a strong link between velocity and mass and it involves the speed of light and light is an EM wave. You seem to be arguing against a very obvious association between those quantities. Or am I reading you wrong?

I think Drakkith's point, which I agree with, is that there is a universal speed limit that exists REGARDLESS of whether photons happen to be massless. The fact that they ARE massless means that they travel at that speed limit. We use the speed of light in the models really as a stand-in for the universal speed limit.

Uh ... I think I just said the same thing Drakkith just said.
 
  • #11
I don't feel particularly happy with using photons along with a theory like SR. That always leads to circular arguments about impossible characteristics for photons. SR, being non quantum, is more to do with fields and the rate at which 'disturbances' propagate. No surprise that this involves a speed limit of c. (No surprise, once Albert introduced the idea at least). The fact that 'light' is and was used in the arguments which lead to SR is a mere chance, based on our visible wavelength range. If we worked at LF radio frequencies, SR would still have been the conclusion but it is less likely that we would be as obsessed with trying to include photons in all our discussions.
Saying that light just happens to behave that way seems to lose the intimate connection between all the quantities. To my mind it is not just peripheral. The maths just yields the answers that the input physical ideas force it to.
 
  • #12
The OP hasn't been back.
 
  • #13
Vanadium 50 said:
The OP hasn't been back.

Yep. It's like dads with their son's radio controlled car. They take over. I'm sure the OP never expected the overkill response.
 

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