# I was wondering why Einstein picked C for this equation.

## Main Question or Discussion Point

I was wondering why Einstein picked C for this equation. C is just one spot on the energy spectrum, the high end of which we are probably not yet aware. A nuclear explosion, for example, produces energy in the full range, sound, microwave, radio, etc., (we assigned names for identifying convenience). Could it be because light is the most noticed because our life form developed the ability to see this particular spectrum and it is most on our minds. It might sound silly but why not E=M(microwave)2 or E=M(subwoofer-level)2. Does C produce the maximum energy during the conversion and does C include all the other energy spectrum released in this equation. Specifying only C cannot be accurate as to the amount of energy released and if the equation is not accurate why has it not been replaced or at least updated with a more accurate model. Surely our instrumentation is up to generating a higher standard.

If the equation is maintained as a monument to Einstein then that I can understand but I find it hard to believe it hasn't been attacked.

Thank you. Please try not to hammer me too hard, just the standard amount.

Sunblock

Related Special and General Relativity News on Phys.org

C is not 'light'. C is the 'speed' of light, which is constant no matter what the energy is.

Thank you.

Would everyone please add "speed of" in front of any reference to the energy spectrum.

Sunblock

russ_watters
Mentor

Thank you.

Would everyone please add "speed of" in front of any reference to the energy spectrum.

Sunblock
Huh? What "energy spectrum"?
I was wondering why Einstein picked C for this equation.
Einstein set about the task of figuring out the implications of a constant speed of light and principle of relativity. He derived this equation based on those implications. Nothing was "picked".
C is just one spot on the energy spectrum, the high end of which we are probably not yet aware.
That sentence has no meaning that I can discern. You have a misconception about something, but what, exactly, it is I don't know. It almost sounds like you think C is a frequency of em radiation (like radio, microwaves, gama waves, light, etc.). It isn't, it is just the letter used to signify the speed of EM radiation.
If the equation is maintained as a monument to Einstein then that I can understand but I find it hard to believe it hasn't been attacked.
It has been "attacked" plenty! Every time you use a GPS receiver or nuclear power, you are "attacking" (challenging) it! It has withstood a swarm of highly precise "attacks" over the hundred years since it was devised.

Thank you. Please try not to hammer me too hard, just the standard amount.
Sunblock
As you may have found out by now, the standard amount of hammering is probably a little high.

C is a constant for the speed of light. Unlike other objects, the speed of light does not depend on the energy of its waves, or particles. The electromagnetic spectrum consists of different groups, but it is irrelevant when dealing with the constant C. It is nonsensical (and rather amusing ) to say 'microwave squared' because a microwave is just light with a defined energy range. Its speed is still C, the constant, the speed of light.

If you want, you could wiki E=mc^2. This would probably help you understand it better.

That sentence has no meaning that I can discern.
It is referring to the spectrum of potential speeds of energy propagation.

Sunblock:
Radio, microwaves, gamma rays, visible light, etc, all travel at the exact same speed (c). According to the modern theories of physics (QFT/GR), no kind of energy can ever go faster than c (not gravity, not sound of any frequency, not nuclear waves, not rocket-ships, etc), and as Russ says, these theories are standing up well to experiment.

cesiumfrog, thank you. You have a desirable ability to go right to the point right through a mass of unprofessionalism.

Therein lies part of my question. Why use C which specifies "light" rather than some other identifier that has the same parameters for usage within the equation. It would seem because it is the most familiar understanding and term for humans within the discipline. Did someone say, "We have to use the speed of light because we can see it and it is familiar to us." Or was the absolutely incredible development of eyes in the majority of life on this planet to absorb and process what we call "light" part of the product of the energy process and life cycle of the universe and it's usage is simply second nature.

Sunblock

You have a desirable ability to go right to the point right through a mass of unprofessionalism.
Sunblock
The last thing I would do is start attacking us. I don't understand your question anymore. It is simply not a question that makes any sense. I don't know if you really know what C equals.

C = the speed of light = 299 792 458 m / s.

What we call light is just really packets of photons, made of energy. Why use light? in this equation? This makes no sense. C is a variable. Its like using n to represent a random number.

"Why use C which specifies "light" rather than some other identifier that has the same parameters for usage within the equation? "

If E=mc^2, what else do you want it to equal? There is no other option.

E=m x (299 792 458 m / s)^2. C is a number.

"C is just one spot on the energy spectrum, the high end of which we are probably not yet aware."

This is completely irrelevant. Like I said, the energy of the light is irrelevent when we talk about C. C never changes. It is true for all energies of the spectrum.

As for future posts lets not undermine each other. You have to understand that Russ, me, and a lot of others are complete nerds over this stuff. We know what we are saying, especially Russ.

Thank you benk99nenm312 for attacking just the standard amount.

When I said "through a mass of unprofessionalism", I ment the way I posed the question without knowing the proper language. I would never feel comfortable attacking anyone on this forum.

I ask these questions because at my age I have maybe 5 or 8 or 10 years left and I wanted to find out some answers to some of my thoughts. The answers were specific and I thank you and everyone. I still have some problems with this current question, however inaccurately asked but I'll sort that out. I know that you and the others know this stuff inside and out, nevertheless, they don't call them theories and current models for nothing. What a fantastic way to spend your life. Congratulations.

Sunblock

russ_watters
Mentor

Therein lies part of my question. Why use C which specifies "light" rather than some other identifier that has the same parameters for usage within the equation. It would seem because it is the most familiar understanding and term for humans within the discipline. Did someone say, "We have to use the speed of light because we can see it and it is familiar to us."
I explained that already: the equation was derived, the parameters were not chosen arbitrarily. I'm not even sure Einstein realized he would find that energy and mass were equivalent when he set out to explore the implications of a constant speed of light.

It is a commonly asked question: http://van.physics.illinois.edu/qa/listing.php?id=1783

Or was the absolutely incredible development of eyes in the majority of life on this planet to absorb and process what we call "light" part of the product of the energy process and life cycle of the universe and it's usage is simply second nature.
No. Again, that doesn't make any sense.

Perhaps the most important thing to learn about science is that very little about it is arbitrary. Things aren't usually picked, ideas aren't usually pulled out of thin air. They are derived mathematical (or logical) relationships between pieces of data.

Last edited:

When I said "through a mass of unprofessionalism", I ment the way I posed the question without knowing the proper language. I would never feel comfortable attacking anyone on this forum.
Sunblock
I'm so very sorry. I completely misinterpreted what you said. I thought you were referring to the posts that Russ and I posted. I understand this now. I feel terrible. I hope you can forgive me.

marcus
Gold Member
Dearly Missed

This thread would seem more appropriate for the General Physics forum, or for the Relativity forum. It is not about the overall structure and dynamics of the universe.

benk99nenm312, don't be silly. Contention and hammering makes us think. A very valuable tool. I don't use the proper definitions and I'm not very clear. Don't you suffer too.

Sunblock

Thank you all. I appreciate the answers and the tolerance. Time to move on.

Sunblock

Redbelly98
Staff Emeritus
Homework Helper

Therein lies part of my question. Why use C which specifies "light" rather than some other identifier that has the same parameters for usage within the equation. It would seem because it is the most familiar understanding and term for humans within the discipline. Did someone say, "We have to use the speed of light because we can see it and it is familiar to us." Or was the absolutely incredible development of eyes in the majority of life on this planet to absorb and process what we call "light" part of the product of the energy process and life cycle of the universe and it's usage is simply second nature.
Hi Sunblock,

It may be that you are confused between two different uses of the word "light". In popular language, it usually means visible electromagnetic radiation. But in physics, it can (but doesn't always) refer to e-m radiation of any wavelength.

From http://en.wikipedia.org/wiki/Light :
Light is electromagnetic radiation, particularly radiation of a wavelength that is visible to the human eye (about 400–700 nm), or perhaps 380–750 nm. In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not.
Since "the speed of light" is the same for all wavelengths, we really aren't restricting ourselves to visible light when we write equations like E=mc2 for example.

Hope that helps.