# Why do like charges repel and opposite charges attract?

1. May 5, 2004

### protonman

Why do like charges repel and opposite charges attract?

2. May 5, 2004

### chroot

Staff Emeritus
Because, according to Coulomb's law,

$$F = \frac{1}{4 \pi \epsilon_0} \frac{q_1 q_2}{R^2}$$

the charges are multiplied together. When their signs are the same, the force is positive, representing a repulsion. When their signs are opposite, the force is negative, representing an attraction.

- Warren

3. May 5, 2004

### protonman

That doesn't answer the question. Anyone can observe that they do behave as I asked and make up an equation to show that. What I am asking is a more physical explanation.

4. May 5, 2004

### chroot

Staff Emeritus
What you're asking for is not a physical explanation; you're asking for a philosophical explanation. No one knows why there happen to be two kinds of electric charge (instead of four or nineteen) or why they work as they do. Even if one day a theory does present a logical reason for such behavior, we'll have to question the reasons why that theory exists, and so on, ad infinitum. Eventually, at a deep enough level, we'll just have to be assuaged with one of two beliefs:

1) It just is that way, and there's no deeper reason.
2) God, or some other sentient being, chose for it to be that way.

Personally, I'd just invoke the anthropic principle and not worry about it anymore.

- Warren

5. May 5, 2004

### protonman

What if Einstein just decided to "not worry" about the incompatibility between Maxwell's equations and Galilean relativity? You thinking is surprising for a scientist.

6. May 5, 2004

### chroot

Staff Emeritus
That's quite a different worry.

- Warren

7. May 5, 2004

### protonman

Strong or weak anthropic principle?

8. May 5, 2004

How is this?

9. May 5, 2004

### chroot

Staff Emeritus
When we have two mathematically-developed theories that disagree, something is obviously wrong with one or both of those theories. That prompts us to do more experimentation, to determine where and how the theories fail.

In contrast, when we have one mathematically-developed theory that produces valid predictions for all known experiments, we go home and sleep easy -- that's all we intended to do. We don't generally care too much about the philosophy of WHY that particular theory is correct, since it's pretty much a rhetorical question.

- Warren

10. May 5, 2004

### protonman

The term "we" in your quote is quite strong. Do you speak for all physicists?

11. May 5, 2004

### chroot

Staff Emeritus
Not for all, I'd imagine -- but certainly for the vast majority.

- Warren

12. May 5, 2004

### protonman

How do you come to this conclusion?

13. May 5, 2004

### chroot

Staff Emeritus
I read the things other physicists write. I converse with other physicists.

- Warren

14. May 5, 2004

### protonman

Have you read the writings of the vast majority?

15. May 5, 2004

### protonman

You are not even a physicist. I want to hear from a physics expert not an engineer.

16. May 5, 2004

### chroot

Staff Emeritus

- Warren

17. May 5, 2004

### Integral

Staff Emeritus
Warren,
You seem to be on the right track as far as I know. I think few Physicts would argue with you.

Protonman,
What is your point? Have you ever spoken to ANY physicists?

18. May 5, 2004

### protonman

First of all you can't speculate what the majority of physicists would say. As someone who claims to be involved in science it seems strange you would present something like that without evidence.

Second, I spent plenty of time with physicists and I have listened to many. From my personal experience your view does not represent the views of those scientists I have had encounters with.

19. May 5, 2004

### Nereid

Staff Emeritus
What views have they expressed to you?

20. May 6, 2004

### Integral

Staff Emeritus
Without a doubt you were hearing exactly what you wanted to hear without understanding a word that was said.

It would be interesting to hear more of the details.

Oh yeah, I spent 8 yrs working in the Physics department of a major research university. So, yes, I have spent some time around Physicists, both professionally and personally (ie around a keg of beer).