# Did quantum mechanics kill cause and effect?

#### hlreed

Registered Senior Member
Title says it all. One of the key notions of macro mechanics is that of cause and effect.
A = b + c ; means b and c cause A
Is this gone?

Harold

Originally posted by hlreed
A = b + c ; means b and c cause A
Well, I'm no crackpot, but it looks to me like the sum of b and c equals A.

- Warren

or A=b+c

Of course it does. If it were a machine, and it is, then b + c causes A. That it is equal is true, but b and c have to happen first in a machine, so why not say it causes A.
And you did not answer my question.

Harold

Hmmm... but then A-b = c, so c causes A-b... whatever that means.

And A-b-c = 0, so really zero is the cause of all things... whatever that means.

- Warren

I never said all things. I said this thing.
I know how to do algebra, you don't have to tell me that. What I don't know is quantum mechanics and I am reading that cause and effect are not preserved but momentum and energy are.

I knew a guy like you in college. Could not talk to him either.

Originally posted by hlreed
I knew a guy like you in college. Could not talk to him either.
"The rest of the world is nuts -- not me -- no, I'm the sane one, and they're the ones who are nuts." -- Lunatic

The truth is that cause and effect are still in full splendor in quantum mechanics. Could you provide an example of how cause and effect are 'broken?'

- Warren

chroot,

The truth is that cause and effect are still in full splendor in quantum mechanics. Could you provide an example of how cause and effect are 'broken?'

Isn't randomness a violation of cause-and-effect???

Tom

Originally posted by Prosoothus
Isn't randomness a violation of cause-and-effect???
Not that I'm aware of. Can either of you provide a specific example?

- Warren

RE:chroot

Could you provide an example of how cause and effect are 'broken?'

Yes, easily. The weather report saturday said that it was going to rain on Sunday. So I went and bought an umbrella on Saturday. It rained on Sunday. The the later even caused the preceding one.

Re: RE:chroot

Originally posted by ProCop
Yes, easily. The weather report saturday said that it was going to rain on Sunday. So I went and bought an umbrella on Saturday. It rained on Sunday. The the later even caused the preceding one.
The rain didn't cause you to buy an umbrella -- the weather report did.

Besides, I think this hardly qualifies as quantum mechanics -- shut up.

- Warren

chroot,

"Isn't randomness a violation of cause-and-effect???"

Not that I'm aware of. Can either of you provide a specific example?

I look at randomness as an effect without a cause. This seems to violate the principle of cause-and-effect.

Tom

RE:chroot

Besides, I think this hardly qualifies as quantum mechanics -- shut up.

Well the Sunday's rain might have been the cause of Saturday's weather report....but.. ok, I couldn't resists the joke. My sincere apology.

Originally posted by Prosoothus
I look at randomness as an effect without a cause. This seems to violate the principle of cause-and-effect.
Well, there's no reason to think of randomness as either 'an effect' or 'not an effect.' You can think of it either way.

Can you provide a specific non-relativistic quantum-mechanical example of an effect preceding a cause?

- Warren

In fact, QFT is constructed in such a way to explicitly preserve causality. any QFT textbook devotes 10 pages of chapter 1 to explain why the square root of the Klein gordon equation does not make a good wave equation for a QFT. it cannot preserve causality.

the goal of using the square root of the klein gordon equation is to eliminate negative energy solutions. but it can be shown that you cannot both restrict yourself to positive energy solutions, and preserve causality. since causality is pretty useful (understatement), we have to infer the existence of negative energy solutions. hence, antiparticles exist.

aren't you just using different notation? I think both cases are valid.. I think you have to be carefull about the context that you're using A = b + c. that's the problem. Warren is saying "you're making a mathematical statement" and hlreed is saying "i'm using mathematical symbols to say something about a mechanical system". it seems to me that either are correct, but it's important not to be confused about which you're referring to right?

cause and effect seem to be violated by the slit experiment right? there are a lot of other things about quantum mechanics (which I barely understand) which seem quite weird and it's easy to say "cause and effect" are violated when you're not sure how the whole thing works to begin with. though a lot of people know a lot of things about QM, I would imagine that most wouldn't say cause and effect are violated, just that they might not be as we once thought they were. make any sense?

Originally posted by wesmorris
Warren is saying "you're making a mathematical statement" and hlreed is saying "i'm using mathematical symbols to say something about a mechanical system".
hlreed is a crackpot, and was just taking the opportunity to rib him a bit.
cause and effect seem to be violated by the slit experiment right?
Not that I'm aware of. Can you be more specific?
I would imagine that most wouldn't say cause and effect are violated, just that they might not be as we once thought they were. make any sense?
Not really. QM does not lead to violations of causality. Period.

- Warren

chroot,

Well, there's no reason to think of randomness as either 'an effect' or 'not an effect.' You can think of it either way.

Can you provide a specific non-relativistic quantum-mechanical example of an effect preceding a cause?

I believe that the cause-and-effect principle is based on two rules:

1) Every effect must have a cause.

2) A cause will always precede an effect.

I don't think that anything violates rule two, but I think that randomness violates rule one.

Tom

Originally posted by Prosoothus
I don't think that anything violates rule two, but I think that randomness violates rule one.
Well, your rule 1 is not associated with the scientific meaning of 'causality' at all -- only rule 2.

According to rule 1, every physical law 'breaks causality.' Why are there two kinds of electric charge? Goodbye causality. Why does light appear to travel with the same velocity in every frame of reference? Goodbye causality.

It's kinda meaningless to apply your rule 1.

- Warren

chroot,

According to rule 1, every physical law 'breaks causality.' Why are there two kinds of electric charge? Goodbye causality. Why does light appear to travel with the same velocity in every frame of reference? Goodbye causality.

Are you sure that there isn't a reason (a cause) why there are only two kinds of charge (I'm assuming that your ignoring quarks)?

And as far as I know, relativity states that time dilation and length contraction is the reason (or cause) behind the principle of invariance of light.

Tom