Science Quiz

[col]

As far as i know you coud construct a universe which had the force reversed and build atoms with antiprotons and electrons. I cant think of a reason why that wouldnt work.

I dont Physics can ever really answer 'why' completely satisfactorily. As Kinniken says, you can move to a deeper level but ultimately you have to come to 'because thats the way things are'

 

[betazed]

Originally posted by col
I dont Physics can ever really answer 'why' completely satisfactorily. As Kinniken says, you can move to a deeper level but ultimately you have to come to 'because thats the way things are'

very true.

But we do know at a much deeper level (QED to be exact) why charges attract and why the signs of Maxwell are so and so.

If no one answers this by tomorrow I will give the answer as I understand it.

I asked this primaily because I am not satisfied with the understanding that I currently have and was hoping that someone on this forum can provide a cleaner answer because I know there are quite a few scientists here

 

[betazed]

Originally posted by col
As far as i know you coud construct a universe which had the force reversed and build atoms with antiprotons and electrons. I cant think of a reason why that wouldnt work.

yes but that would still require opposite charges to attact and like charges to repel, which was the gist of my question.

 

[The Last Conformist]

OK. I expected you to shooting it down. That was basically the intention behind posting it.

So it's something to do with photon emission from charges in motion? That means I'm totally out of my depth, so let's say that if EM potentials went the other way the gauge symmetry for EM wouldn't hold.

 

[col]

but QED is no 'deeper' than the conservation of energy.

 

[betazed]

Originally posted by col
but QED is no 'deeper' than the conservation of energy.

True.

But AFAIK, conservation of energy does not have anything to do in determining the sign of the forces between charges.

 

[col]

Originally posted by betazed


yes but that would still require opposite charges to attact and like charges to repel, which was the gist of my question.

So are you really asking 'why are there two types of electrical charge?'

 

[col]

The direction of the force follows from that formula for the potential energy of the system. The force is always in the direction of decreasing potential energy to satisfy conservation of work/energy. Since the energy of two charges goes as their product, the direction of the forces between like and unlike charges follows as per my first post.

 

[betazed]

Originally posted by col


So are you really asking 'why are there two types of electrical charge?'

Nooooooooo

While that is a very good question, that is wayyyyyyyyy beyond my ken.

I am asking given the fact that there are two kinds of charges why are the forces between them are as they are?

 

[The Last Conformist]

Allow me a threadjack:

col: Gravity has mass, EM charge and the strong interaction has colour. What does the weak interaction have?

 

[col]

Originally posted by The Last Conformist
Allow me a threadjack:

col: Gravity has mass, EM charge and the strong interaction has colour. What does the weak interaction have?

Intermediate vector bosons - W particles - discovered at CERN in the 90s I think. Carrying electroweak charges.

Strong force has colour, strangeness and charm.

 

[Gothmog]

From what I understand the calculation based on Feynman diagrams is not really about the repulsive or attractive forces, but more about how the two particles exchange energy and momentum as they pass by one another. The coulomb field effects are there as well, but the calculation, done correctly, takes care of them implicitly. I think that there are many variants of the correct formalism (QED has one too?), which look quite different in practice but all give the correct answer.

 

[betazed]

Originally posted by The Last Conformist
Allow me a threadjack:

col: Gravity has mass, EM charge and the strong interaction has colour. What does the weak interaction have?

As Col Stated: W and Z bosons interacting with fermions having certain 'flavor' which corresponds to charge in EM.

<edit> corrected:

 

[col]

Originally posted by betazed

I am asking given the fact that there are two kinds of charges why are the forces between them are as they are?

Ok - so I can rephrase that as 'why does the potential energy of two charges go as the product of the charges' then use my earlier 'proof'

 

[The Last Conformist]

Intermediate vector bosons would correspond to gravitons, photons, gluons. Electroweak charge? That sounds like it should belong to electroweak union, and dissolve into electric charge and something else below the symmetry breaking point?

 

[col]

I love this site

http://particleadventure.org/particleadventure/frameless/weak.html

http://particleadventure.org/particleadventure/frameless/electroweak.html

 

[betazed]

Originally posted by col
but QED is no 'deeper' than the conservation of energy.

Actually col after some thought I will humbly differ on this one.

All conservation laws come from symmetry and homegenity considerations in physics which is "deeper".

Conservation of momentum - homogeniety of space
Conservation of Angular momentum - Isotropy of space
Conservation of mass/Energy - homogeneity of time

Wouldn't you say so?

 

[col]

Well its a moot point isnt it. I thought it might provoke a response!

Homogeneity can be deduced from the conservation laws. Conservation laws can be deduced from homogeneity. I just regard them as alternative descriptions like energy and forces.

Neither is more fundamental, they are just different ways of looking at the same thing.

 

[betazed]

Possibly.

The concept of symmetry seems to be so tied with conservation in physics. And since symmetry and its breaking seems to be so important in particle physics I just intuitively considered it more fundamental.

I guess logically speaking I should not.

Originally posted by col
I thought it might provoke a response!

I did not know you were into baiting!

 

[Kinniken]

Well, it looks we will b waiting some time for a suitable answer - but when someone makes up a convincing one, we might just get our first CFC member with a Novel prize