Does Noether theorem explain the constant speed of light?

In summary, Emmy Noether's theorem states that every conserved quantity is due to a symmetry. Examples of this include conservation of energy as symmetry in time and conservation of momentum as symmetries in space. It is theorized that universal constants, such as the speed of light, may also be due to symmetries in the universe. However, these constants are not related to any specific symmetry and are instead arbitrary man-made units. The most fundamental constants are dimensionless and their values do not depend on the unit system chosen. Therefore, the reason for the existence of these constants and their proportion to one another is still unknown.
  • #1
Frigorifico
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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
 
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  • #2
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.
 
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  • #3
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
 

1. What is Noether's theorem?

Noether's theorem is a fundamental principle in physics that states that for every continuous symmetry in the laws of physics, there exists a corresponding conserved quantity. In other words, if the laws of physics remain unchanged under certain transformations (such as translation or rotation), then there must be a corresponding physical quantity that remains constant.

2. How does Noether's theorem relate to the speed of light?

Noether's theorem does not directly explain the constant speed of light, but it does provide a framework for understanding the symmetry that is inherent in the laws of physics. In particular, the principle of Lorentz symmetry (which states that the laws of physics are the same for all observers moving at a constant velocity relative to each other) is closely related to the constancy of the speed of light.

3. Can Noether's theorem be used to prove the constant speed of light?

No, Noether's theorem does not prove the constant speed of light. It is a mathematical principle that helps us understand the underlying symmetries of the laws of physics, but it does not provide a definitive explanation for why the speed of light is constant.

4. Are there other theories or principles that can explain the constant speed of light?

Yes, there are other theories and principles that attempt to explain the constant speed of light, such as Einstein's theory of special relativity. This theory posits that the laws of physics are the same for all observers in inertial frames of reference and that the speed of light is the maximum speed at which all energy, matter, and information can travel.

5. Is the constant speed of light still a mystery?

While the constant speed of light is still a topic of ongoing research and debate, it is generally accepted as a fundamental principle in physics. While we may not fully understand why the speed of light is constant, it has been extensively tested and supported by numerous experiments and observations, making it a cornerstone of our understanding of the universe.

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