Is the Total Charge in the Universe Really Zero?

[Q_Goest]

If some insane diety wanted to play a trick on us by taking the negative charge on electrons and quarks and making them positive instead, and then taking all positive charges and making them negative instead, would there be any way that we could tell? Is there any measurement we could perform that would indicate that the negative and positive charges had suddenly changed?

 

[dst]

To my knowledge, no. Unless there's some strange asymmetry going on between the charges. I thought they were perfectly symmetric and hence, switching them over would change absolutely nothing. Of course, in a magnetic field there would be different effects. If all 4 'charges' were reversed then how could you tell a difference?

 

[Q_Goest]

Thanks dst.

If all 4 'charges' were reversed then how could you tell a difference?

Not sure what other two charges you're referring to. Please elaborate.

 

[dst]

Magnetic poles. Hey, my knowledge doesn't go far at all so it's pure speculation from me.

 

[TVP45]

If some insane diety wanted to play a trick on us by taking the negative charge on electrons and quarks and making them positive instead, and then taking all positive charges and making them negative instead, would there be any way that we could tell? Is there any measurement we could perform that would indicate that the negative and positive charges had suddenly changed?

Can you state the difference(s) between the two kinds of charge other than how we write them?

 

[Q_Goest]

Thanks for chiming in TVP. I'm holding off on offering any responce on this question.

I'm assuming you see no change either? In which case, what proof would you offer?

 

[PatPwnt]

I believe you wouldn't see a difference in magnetic poles either. If you think about charges, what truly is the difference between them? Nothing besides that they are opposite. We can't really differentiate them apart otherwise. Same with north and south poles. If you reverse them both, they are still opposite and will behave the same exact way.

 

[ranger]

I wonder if we could use the Hall effect?

So if the hall voltage is proportional to the electron drift velocity and this drift velocity is in turn dependent on the electron mass...

 

[Q_Goest]

Thanks for the responces. I fully agree there shouldn't be any difference, but wanted to see if I might have missed anything. Regarding the magnetic poles, since the magnetic field is created by the moving electric charge, the magnetic poles will flip so to speak, but then since the charges are also flipped, any path taken by an electrically charged particle through this magnetic field shouldn't change, so there would be no way of knowing the two charges were switched.

Any other comments would be welcome.

 

[PleaseEnter]

...by taking the negative charge on electrons and quarks and making them positive instead, and then taking all positive charges and making them negative instead, would there be any way that we could tell...

...Any other comments would be welcome.

My understanding is that negative and positive are just definitions that Faraday (or someone around that time - maybe Franklin) applied, so it's irrelevant which way around they are used. He could have called them apple and orange charges (or some name that wasn't already in use) and applied them any way he wanted - they're arbitrary

In 1839 Michael Faraday showed that the apparent division between static electricity, current electricity and bioelectricity was incorrect, and all were a consequence of the behavior of a single kind of electricity appearing in opposite polarities. It is arbitrary which polarity you call positive and which you call negative. Positive charge can be defined as the charge left on a glass rod after being rubbed with silk.

edit...
Come to think of it, that doesn't really answer your question. Changing the definition of negative and positive isn't quite the same as a fiendish diety popping down from heaven (or wherever they hang out) and physically changing the -ve (or apples) to +ve (or oranges), or rather switching the physical properties that -ve and +ve refer to. I think if they did change them around you would be able to tell the difference because nothing would work anymore and you and the universe probably wouldn't be here anymore, although then you couldn't really tell the difference because you would know the "before" but not the "after" as you wouldn't exist in the "after". Tricky...

 

[rbj]

it's like i and -i. they both have equal claim to square to be -1. they are additive inverses of each other, otherwize they are identical in every qualitative respect. switch them around and no one could tell.

 

[belliott4488]

Isn't this just charge conjugation? I thought the Maxwell Eqs. are known to be invariant under charge conjugation, so there would be no difference in any field solutions.

 

[Gokul43201]

If some insane diety wanted to play a trick on us by taking the negative charge on electrons and quarks and making them positive instead, and then taking all positive charges and making them negative instead, would there be any way that we could tell? Is there any measurement we could perform that would indicate that the negative and positive charges had suddenly changed?

Yes, there is!

The direction of emission of electrons from beta decay of spin polarized nuclei would change (i.e., Wu's Co-60 experiment).

belliott: Why should we restrict ouselves to probing EM interactions?

PS: For more on this, look for "charge conjugation" or "C-symmetry". The important thing here is that the EM interaction is invariant under charge reversal, but the weak interaction is not.

 

[MaWM]

Gokul beat me to it. You *can* tell the difference. Its very subtle, be it might add up over time.

 

[belliott4488]

Thanks, gokul - C-P violation ... didn't think of that!

 

[Q_Goest]

Thanks Gokul, I was worried there might be something else to it. All the obvious stuff such as magnetic pole reversal seems fairly straightforward. I've heard of "symetry violations". Is that what this is about?

So the next thought is to change a few other fundamental forces or constants. (Our insane diety is just dying to play a dirty trick on us!)

Is there something else she could do that might prevent us from finding out that something has changed? Are there other constants of nature that he might flip such that everything goes back to normal, including “the direction of emission of electrons from beta decay of spin polarized nuclei”?

 

[MaWM]

As far as we can tell, even theoretically, if all particles were switched for their antiparticles, all charges were flipped AND time were reversed, the resulting world would be indistiguishable from our own

 

[Gokul43201]

http://everything2.com/index.pl?node_id=1788979

MaWM, swiching charge and particles for antiparticles is the same thing, no?

 

[MaWM]

hmmmm when I mentioned antiparticles, I was trying to talk about parity inversion, which is the reflection of all spatial coordinates. My mistake.

 

[Sojourner01]

This is effectively a discrete symmetry question. As Gokul stated, the weak interaction isn't invariant under charge symmetry, but it is invariant under (IIRC) charge-parity symmetry. In other words, if you were to invert the charges as you suggested and switch the labels on the concepts of 'left' and 'right', there would be no perceivable difference in physical laws.

 

[MaWM]

The weak interaction isn't CP invariant either. It is CPT invariant though

 

[Sojourner01]

Gah, yes you're right, typing running ahead of my brain again.

 

[nonequilibrium]

I believe you wouldn't see a difference in magnetic poles either. If you think about charges, what truly is the difference between them? Nothing besides that they are opposite. We can't really differentiate them apart otherwise. Same with north and south poles. If you reverse them both, they are still opposite and will behave the same exact way.

Really? Is that correct?

The sun's magnetic field changes poles every 11 years or so -- how do we know this happens if there's no noticable difference? (it's an actual question, not a retoric one trying to proove you wrong)

 

[Q_Goest]

Hi mr. vodka,
We’re not talking about the possibility that a magnetic field can physically be flipped or reversed, such as would happen if we simply reversed the direction of the flow of electricity through a wire for example. This thread regards what happens if all negative particles in the universe were to become positive and all positive were to become negative. This is called “charge conjugation”.
http://hyperphysics.phy-astr.gsu.edu/Hbase/particles/cpt.html#c2

Magnetic fields are created by the motion of electrical charges as explained here:
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfie.html

The magnetic field is created at right angles to the direction of the motion of the charge. Check this link for a visual.
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magcur.html#c1

You might create a uniform magnetic field for example, in the center of a solenoid as shown here:
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/solenoid.html#c1
The magnetic field in the center of the windings of the solenoid are all parallel and in the same direction.

If you were to have a positive electron moving through the wire instead of a negative electron, the direction of the magnetic field would flip in the opposite direction. Obviously, humans can’t take the negative charge off an electron and put a positive one on, which is why I suggested some supernatural deity, just for the sake of argument. Remember, this is called charge conjugation.

So the point PatPwnt was making is that if you change the charges, then the magnetic field also changes direction. We can determine the direction of a magnetic field by examining the direction of a charged particle moving through that field. A charge will be made to go into a circular motion as shown here:
http://www.pa.msu.edu/courses/1997spring/PHY232/lectures/magforces/circle.html

In the case of this inverted charge creating a reversed magnetic field however, the circular motion of the inverted charge as it passes through a reversed magnetic field will be in the same direction as before the charges were swapped so there would be no way of telling from this particular experiment that the charges were swapped by some devious deity.

So regarding the change in magnetic field in the sun, this is not caused by charge conjugation since the electrons in the sun are all still negative and all the protons still positive.

 

[nonequilibrium]

Wow, thanks for the detailed explanation.

 

[Gokul43201]

Magnetic fields are created by the motion of electrical charges as explained here:
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfie.html

This is sufficient, but not necessary. It is possible to have magnetic fields created not by electrical currents, but by the intrinsic spins of fundamental particles. This is actually what makes most commercial magnets magnetic.

 

[Q_Goest]

Hi Gokul,
Gage your audience. Anyone explaining how electric currents create magnetic fields generally understands how permenant magnets have no measurable electric currents.

PS: thanks again for the CPT explanation

 

[DyslexicHobo]

Just out of curiosity, not that it would affect the question in any way-- what is the net charge of the universe? Or rather, is the total number of positive charges equal to the total amount of negative charges?

 

[belliott4488]

This is sufficient, but not necessary. It is possible to have magnetic fields created not by electrical currents, but by the intrinsic spins of fundamental particles. This is actually what makes most commercial magnets magnetic.

Yikes - I would have thought that if we changed only the signs of the charges, the magnetic moments associated with those intrinsic spins would have changed direction as well ... not so? IOW, while there's no current, the magnetic fields still depend on the signs of the fundamental particles, don't they?

 

[Quatl]

Just out of curiosity, not that it would affect the question in any way-- what is the net charge of the universe? Or rather, is the total number of positive charges equal to the total amount of negative charges?

I remember reading that the total charge in the universe is zero. However I can't remember where, or how they justified the statement.

Total charge is a "conserved quantity" in physics though, so the universe should have the same charge as it started with.