# Light and electric charge constant?

• Naty1
In summary, the conversation discusses the concept of invariance in relativity, specifically in regards to electric charge and space-time intervals. It is noted that the four vector momentum, which is the norm of four-momentum and also known as invariant mass, is constant for all observers. The idea of a four-vector that has charge as its norm is mentioned, along with the concept of a current density four-vector. The conversation also touches on the deeper explanation or understanding behind these invariances and mentions the concept of phase as an intriguing invariant quantity.
Naty1
Peter Bergmann (a student of Einsteins) in THE RIDDLE OF GRAVITATION, PAGE 60 notes

... a bodies electric charge has the same value for all observers,...

And here I had been thinking only about the speed of light as invarient.
Is the above coincidence?? I can't tell...

and the space time interval, is also invarient, right??

Are there other entities constant for all observers? Yes, I think four vectors such as "four vector momentum" which in simple terms is E2 - p2 that is (energy)2 - (momentum)2...

I realize these transform (from one reference frame to another) as they do because of the mathematics of the formulations themselves, and the way they fit into relativity, but I can't help wondering if there is any deeper explanation or understanding. Any ideas?

Naty1 said:
Are there other entities constant for all observers? Yes, I think four vectors such as "four vector momentum" which in simple terms is E2 - p2 that is (energy)2 - (momentum)2...
The norm of four-momentum that you mention is the invariant mass (aka rest mass) which is the same for all observers.

I don't know about charge, I would guess that you could set up a current vector and then charge would be the timelike component, but then that wouldn't go along with Bergmann's comment. There must be some other four-vector that has charge as the norm. I actually haven't done much in the way of relativistic EM.

The total charge of an object is $$\int\rho d^3 r$$. It is shown in advanced textbooks that this integral is invariant. It is a tricky proof.

Naty1 said:
Peter Bergmann (a student of Einsteins) in THE RIDDLE OF GRAVITATION, PAGE 60 notes

And here I had been thinking only about the speed of light as invarient.
Is the above coincidence?? I can't tell...

and the space time interval, is also invarient, right??

Are there other entities constant for all observers? Yes, I think four vectors such as "four vector momentum" which in simple terms is E2 - p2 that is (energy)2 - (momentum)2...

I realize these transform (from one reference frame to another) as they do because of the mathematics of the formulations themselves, and the way they fit into relativity, but I can't help wondering if there is any deeper explanation or understanding. Any ideas?
This is how I understand it (but I'm not sure at all to be correct): take a scalar quantity which depends on the frame of reference, e.g. energy, time difference between events, frequency, ecc., then take a vectorial quantity which depends on the frame of reference and that is related with the first (there exist an equation which involve both) example: energy and momentum or time difference and spatial distance, frequency and wave vector, ecc. Then there must exist a four-vector made with that scalar and that vectorial quantity, which square modulus is invariant, because for the relativity principle, all frames of reference must be equivalent, so the above equation must be valid in every of them. All 4-vectors have this property.

Example: if in a frame of ref. S you find: (c*delta t)^2 = 1.5 + (delta x)^2 + (delta y)^2 + (delta z)^2 then you also have to find: (c*delta t')^2 = 1.5 + (delta x')^2 + (delta y')^2 + (delta z')^2 in another frame of ref. S' , so if you write (c*delta t)^2 - (delta x)^2 + (delta y)^2 + (delta z)^2 you have found an invariant quantity because it's always = 1.5

An intriguing (for me) invariant quantity is Phase. I'd like to know which is the 4-vector which square modulus is the phase.

Last edited:

## 1. What is the light and electric charge constant?

The light and electric charge constant, also known as the "fine structure constant", is a dimensionless physical constant that characterizes the strength of the electromagnetic interaction between charged particles. It is denoted by the symbol α and has a value of approximately 1/137.

## 2. How is the light and electric charge constant calculated?

The light and electric charge constant is calculated by dividing the square of the elementary charge (e) by two times the permittivity of free space (ε0) multiplied by the speed of light (c). The equation is expressed as α = e2 / (4πε0hc).

## 3. What is the significance of the light and electric charge constant?

The light and electric charge constant is significant because it determines the strength of the electromagnetic force, which is responsible for many fundamental interactions in nature such as light, electricity, and magnetism. It also plays a crucial role in determining the structure of atoms and molecules.

## 4. Why is the value of the light and electric charge constant approximately 1/137?

The value of the light and electric charge constant being approximately 1/137 is considered to be a coincidence and has puzzled scientists for many years. Some theories suggest that this value is related to the number of subatomic particles in the universe or may be a fundamental constant of nature that has yet to be discovered.

## 5. Has the value of the light and electric charge constant changed over time?

No, the value of the light and electric charge constant has not changed over time. It is considered to be a fundamental constant of nature that is independent of any external factors. However, some theories suggest that it may vary in different regions of the universe, but this has not been proven.

Replies
45
Views
6K
Replies
13
Views
2K
Replies
230
Views
18K
Replies
14
Views
2K
Replies
20
Views
1K
Replies
3
Views
3K
Replies
3
Views
1K
Replies
27
Views
2K
Replies
73
Views
4K
Replies
10
Views
496