# Light Speed Not Constant: Impact on E=mc^2

• lwymarie
In summary, many scientists think that light speed is not a constant. If it is true, then E=mc^2 does not hold because c is no longer a constant. Does this mean that E is not conserved? If yes, many theorems will be wrong...How about everything we know about particle physics and relativity?
lwymarie
recently many scientists think that light speed is not a constant. if it is true, then E=mc^2 does not hold because c is no longer a constant. Does it mean that E is not conserved? if yes, many theorems will be wrong...

How about everything we know about particle phyiscs (which is based on QFT) and relativity (special & general).I think Newton wouldn't mind...

Daniel.

the varying constant-matter has been widely debated here :

As to your original question. Suppose c varies with time, all laws will remain valid because we can assign an 'epoch' to them, just like we do in astronomy when describing the orbits and dynamics of celestial objects like planets. But in the end, all formula's in QM that we know of are completely correct. If you want proof, just look at every functioning electronics-device that you use every day. Ofcourse, certain changes will have to be made and this still is all very speculative. I my opinion, such notions are to some extent quite overblown

marlon

marlon said:
the varying constant-matter has been widely debated here ...

that issue (at least as far as i can see) was more about the meaningfulness (from the POV of mortals) of a vaying dimensionful constant vs. the meaningfulness of a varying dimensionless "constant". I'm not saying that $\alpha$ has varied (i think not as likely) but if it did, we would know the difference. stuff, as we could measure it would be different. if $c$ or $G$ or $\hbar$ varied in and of itself (all other quantities remaining contant), we could not know the difference. we could not measure it.

r b-j

It's very highly improbable that "c","hbar" and "e" to have varied over the billions of years in such way as to keep "alpha" constant...So how about quitting speculations?

Daniel.

dextercioby said:
It's very highly improbable that "c","hbar" and "e" to have varied over the billions of years in such way as to keep "alpha" constant...So how about quitting speculations?

Daniel,

i do not at all take issue with you about whether or not these measurable universal constants have been changing. only to point out that when someone says that c has changed, they have a much more difficult metrological problem even stating such a proposition than if they say that $\alpha$ has changed. saying the latter actually means something. might not be true, we got to measure it carefully, if we could conceivably measure such a change and that would mean something. since, in experiments and in our perception of reality, we only measure dimensionless quantities (we measure dimensionful quantites agaisnt a like dimensioned standard or "unit"), saying c has changed, in and of itself, means nothing. As Michael Duff pointed out, it is like saying that the number of pounds in a kilogram has changed.

so, with regard to changing dimensionful constants, i am trying to clip speculation at an even earlier point. changing $\alpha$ or $\frac{m_p}{m_e}$ can go a little farther before speculation gets clipped.

r b-j

## 1. How does the speed of light not being constant affect the equation E=mc^2?

The equation E=mc^2 is based on the assumption that the speed of light is constant. If the speed of light is not constant, this equation may not accurately calculate the energy of a given mass. Instead, a more complex equation, such as E=√(m^2c^4 + p^2c^2), may need to be used.

## 2. What evidence is there to support the idea that the speed of light is not constant?

One piece of evidence is the observed phenomenon of redshift, where light from distant objects appears to have longer wavelengths than light from closer objects. This could suggest that the speed of light is decreasing over time. Additionally, some theories, such as the Variable Speed of Light (VSL) theory, propose that the speed of light may have varied in the past.

## 3. How would a changing speed of light impact our understanding of the universe?

If the speed of light is not constant, it would greatly impact our understanding of the universe. Our current understanding of the universe is based on the assumption that the speed of light is constant, and many fundamental principles and equations, such as E=mc^2 and the theory of relativity, are built upon this assumption. A changing speed of light could potentially require a complete reevaluation of our understanding of the universe.

## 4. Are there any experiments or observations that could confirm a changing speed of light?

There are ongoing experiments, such as the OPERA experiment, that are attempting to measure the speed of neutrinos and see if it varies based on their energy levels. Additionally, future space missions, such as the Euclid mission, may be able to measure the speed of light in different regions of the universe and see if it varies.

## 5. What implications would a changing speed of light have on other scientific principles and theories?

A changing speed of light would have significant implications on many other scientific principles and theories, including the theory of relativity, quantum mechanics, and the Big Bang theory. It could also potentially impact our understanding of gravity, the behavior of particles, and the formation of the universe.

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