Conservation of charge in the Universe

[Pushoam]

TL;DR

Conservation of charge

The charge of an isolated system is conserved.
This implies the charge of the universe is constant.
This implies that charge can neither be created nor destroyed.
This implies that the net positive charge and the net negative charge of the universe are conserved. Is this right?

 

[anuttarasammyak]

TL;DR Summary: Conservation of charge

This implies that the net positive charge and the net negative charge of the universe are conserved. Is this right?

A closed universe is neutral, i.e., total positive charges and total negative charges cancel by Gauss theorem. For an open universe which has infinite volume and where Gauss theorem is not applicable, I don't think we can say whether infinite number of charge particles have finite net conserved sum with zero, positive or negative sign.

 

[jbriggs444]

I don't think we can say whether infinite number of charge particles have finite net conserved sum with zero, positive or negative sign.

Indeed, this would be very much like evaluating the sum of an infinite, conditionally convergent series. The answer you get depends on the order in which you do the summation.

[It's not really conditionally convergent because it is not convergent at all]

 

[Pushoam]

So, for a close universe, the total charge, total positive charge and total negative charge are constant. Is it so?

 

[topsquark]

A closed universe is neutral...

It makes sense, but how do we know this? For all we know, the Universe started with a net charge!

-Dan

 

[PeroK]

So, for a close universe, the total charge, total positive charge and total negative charge are constant. Is it so?

No. There's pair production, for example:

https://en.wikipedia.org/wiki/Pair_production

 

[anuttarasammyak]

anuttarasammyak said:
A closed universe is neutral.
It makes sense, but how do we know this? For all we know, the Universe started with a net charge!

In a closed universe let us take any closed surface. The universe is divided into two parts : inside the surface and outside the surface. Electric flux go through the surface. The flux correspond to all the charges inside the surface in one end and to all the charges outside the surface in other end. Thus we know that charges inside and outside cancel.
This is the explanation I find in section 111 of The Classical Theory of Fields by Landau and Lifshitz. How do you think of this discussion ?

 

[topsquark]

In a closed universe let us take any closed surface. The universe is divided into two parts : inside the surface and outside the surface. Electric flux go through the surface. The flux correspond to all the charges inside the surface in one end and to all the charges outside the surface in other end. Thus we know that charges inside and outside cancel.
This is the explanation I find in section 111 of The Classical Theory of Fields by Lev Landau and Lifshitz. How do you think of this discussion ?

Ah! I see the point now. Hmmm.... wouldn't that argument have to hold for gravity as well? I'll have to ponder that one.

-Dan

 

[PeroK]

In a closed universe let us take any closed surface. The universe is divided into two parts : inside the surface and outside the surface. Electric flux go through the surface. The flux correspond to all the charges inside the surface in one end and to all the charges outside the surface in other end. Thus we know that charges inside and outside cancel.
This is the explanation I find in section 111 of The Classical Theory of Fields by Landau and Lifshitz. How do you think of this discussion ?

I don't follow this argument at all.

 

[anuttarasammyak]

I interpreted : The surface integral of electric field is common for inside region and outside region but with opposite sign due to opposite direction of surface inside/outside. Applying Gauss theorem charges outside and charges inside are same amount but with different sign. Thus they cancel in sum.

 

[PeroK]

I interpreted : The surface integral of electric field is common for inside region and outside region but with opposite sign due to opposite direction of surface inside/outside. Applying Gauss theorem charges outside and charges inside are same amount but with different sign. Thus they cancel in sum.

So, a closed universe with only two electrons is impossible because ...

 

[anuttarasammyak]

So, a closed universe with only two electrons is impossible because ...

… it contradicts with Gauss theorem.

 

[Vanadium 50]

Landau is saying that if you have a source of field lines, you must necessarily have a sink.

I'm not going to argue with that, but I think this requires a static universe as well as a closed one. It probably requires a classical universe as well - no quantum effects like vacuum screening.

 

[PeroK]

Landau is saying that if you have a source of field lines, you must necessarily have a sink.

I'm not going to argue with that, but I think this requires a static universe as well as a closed one. It probably requires a classical universe as well - no quantum effects like vacuum screening.

Or, even, that in a closed universe with only two electons milling around, then Gauss's law doesn't hold.

 

[PeroK]

… it contradicts with Gauss theorem.

Let's see a proof of Gauss's Law for a closed universe.

 

[kered rettop]

No. There's pair production, for example:

https://en.wikipedia.org/wiki/Pair_production

Charge conservation is certainly a revered law. But what assumption is it based on? Physics keeps on formulating conservation laws and then finding cases where they are violated. How do we know that at some silly energy level, pair production doesn't create, say, two positrons?

Edited: I originally wrote "creates".

 

[PeroK]

Charge conservation is certainly a revered law. But what assumption is it based on? Physics keeps on formulating conservation laws and then finding cases where they are violated. How do we know that at some silly energy level, pair production doesn't create, say, two positrons?

Edited: I originally wrote "creates".

It would be odd and illogical to have a standard model and quantum theory where charge is not conserved when there is no evidence for it. Moreover, what would be the nature of the new law that encompases violation of charge conservation? Such a law can't properly be formulated until there is some idea of when it happens.

It's a common theme amongst science skeptics (and I'm not implying you are in this category), that physicists believe the current laws as though they were gospel. When, in fact, they are simply the laws that have hitherto withstood experimental tests.

 

[Vanadium 50]

But what assumption is it based on?

It's based on observation. Because Science.

If you want to argue that "maybe someday we'll see it violated", that's the same argument that even though we've never seen a flying reindeer, maybe we just haven't looked hard enough. I can push a million reindeer off a roof to their deaths, but the ever-growing pile of venison does not mean #1000001 won't fly.

Logically true, but hard to take seriously.

As an aside, charge conservation implies a zero-mass photon and vice versa. We see that a photon has a very, very tiny mass, entirely consistent with zero. Can I prove some future discover won't be different? No. But again, it would be silly to think otherwise.

Sorry, Rudolph. Off the roof with you.

 

[kered rettop]

It's based on observation. Because Science.

If you want to argue that "maybe someday we'll see it violated", that's the same argument that even though we've never seen a flying reindeer, maybe we just haven't looked hard enough. I can push a million reindeer off a roof to their deaths, but the ever-growing pile of venison does not mean #1000001 won't fly.

Logically true, but hard to take seriously.

[Examines contrived parallel, sees glaringly obvious flaw, decides to ignore entire thing.]

 

[kered rettop]

It would be odd and illogical to have a standard model and quantum theory where charge is not conserved when there is no evidence for it. Moreover, what would be the nature of the new law that encompases violation of charge conservation? Such a law can't properly be formulated until there is some idea of when it happens.

It's a common theme amongst science skeptics (and I'm not implying you are in this category), that physicists believe the current laws as though they were gospel. When, in fact, they are simply the laws that have hitherto withstood experimental tests.

In the region accessible to us. Which is why it is foolish to assume that they are universal.

 

[renormalize]

In the region accessible to us. Which is why it is foolish to assume that they are universal.

Why is it necessarily a foolish assumption? Just take it as a working hypothesis, to be used until evidence to the contrary is forthcoming.

 

[Drakkith]

In the region accessible to us. Which is why it is foolish to assume that they are universal.

We assume they apply until we observe that they do not. This doesn't mean we have chiseled these laws into immutable stone that can never be changed, we just haven't observed anything that violates them and we have no theoretical reason to believe that they will be.

 

[Hornbein]

In the end physics is a pragmatic applied science. You do the simplest thing that works.

 

[Hornbein]

It's provisional, like just about everything else in science.

 

[jedishrfu]

Since the original question has been explored well, I think its a good time to close this thread.

Thank you all for contributing here.

Jedi