I Does Noether theorem explain the constant speed of light?

AI Thread Summary
The discussion explores the relationship between Noether's theorem, which connects symmetries to conserved quantities, and the constancy of universal constants like the speed of light. It suggests that if the universe had inherent symmetries, these could explain the constancy of such values. However, it is clarified that the speed of light is more akin to a conversion factor between units rather than a result of symmetry. The conversation also touches on dimensionless constants, like the fine-structure constant, which do not correspond to any symmetry. Ultimately, the participants express uncertainty about the underlying reasons for the existence and proportionality of these constants.
Frigorifico
Messages
32
Reaction score
0
I learned in Analytical Mechanics: "Emmy Noether's theorem shows that every conserved quantity is due to a symmetry".
The examples I learned where conservation of energy as symmetry in time and conservation of momentum as symmetries in space.

Now I wonder, do universal constants are also due to symmetries like the speed of light?.
Maybe if we lived in a word that couldn't help but be symmetric in space, then there would be a universal value for momentum for all things, or I don't know.

The idea is that the speed of light is constant because of a symmetry inherent to the universe, but knowable nonetheless.

The speed of light is the first one I thought about, but now I wonder if this could apply to other universal constants, like G for gravity and k for electromagnetism.

Now, I have no idea what this symmetries would be, and maybe I am generalizing wrong, if so please illuminate me.

Thanks
 
Mathematics news on Phys.org
The speed of light as constant is similar to the conversion between miles and kilometers: 1 mile = 1.609 km. This conversion is true everywhere in the universe, in every reference frame, but it is just a conversion between arbitrary man-made units.

We could express all lengths in light-seconds, or all times in meters. It would not change physics, and in fact this is frequently done in particle physics, where energy, momentum and mass are all expressed in the same units (eV). In those unit systems, ##c=1##. There is no symmetry related to a constant that is 1.
You can also set ##\hbar = 1 ##, then particle lifetimes can be expressed in 1/eV. Add ##G=1## (sometimes defined with a prefactor) and you get the Planck units.

The really fundamental constants are dimensionless constants: their value does not depend on the unit system we choose. The most prominent example is the fine-structure constant, about 1/137. But those don't correspond to any symmetry either.
 
  • Like
Likes BvU
mfb said:
The speed of light as constant is similar to the conversion between miles and kilometers: 1 mile = 1.609 km. This conversion is true everywhere in the universe, in every reference frame, but it is just a conversion between arbitrary man-made units.

We could express all lengths in light-seconds, or all times in meters. It would not change physics, and in fact this is frequently done in particle physics, where energy, momentum and mass are all expressed in the same units (eV). In those unit systems, ##c=1##. There is no symmetry related to a constant that is 1.
You can also set ##\hbar = 1 ##, then particle lifetimes can be expressed in 1/eV. Add ##G=1## (sometimes defined with a prefactor) and you get the Planck units.

The really fundamental constants are dimensionless constants: their value does not depend on the unit system we choose. The most prominent example is the fine-structure constant, about 1/137. But those don't correspond to any symmetry either.

Thanks. I wanted there to be a reason for some values to be constant, but I guess we still don't know the reason for the constants to exist nor they proportion to one another
 
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. In Dirac’s Principles of Quantum Mechanics published in 1930 he introduced a “convenient notation” he referred to as a “delta function” which he treated as a continuum analog to the discrete Kronecker delta. The Kronecker delta is simply the indexed components of the identity operator in matrix algebra Source: https://www.physicsforums.com/insights/what-exactly-is-diracs-delta-function/ by...
Suppose ,instead of the usual x,y coordinate system with an I basis vector along the x -axis and a corresponding j basis vector along the y-axis we instead have a different pair of basis vectors ,call them e and f along their respective axes. I have seen that this is an important subject in maths My question is what physical applications does such a model apply to? I am asking here because I have devoted quite a lot of time in the past to understanding convectors and the dual...
Back
Top