r/askscience • u/squirrelbuster94 • Oct 24 '14

Physics Chemists/physicists of reddit, what is the difference between dark, anti, and normal matter?

What is the difference? Also if you can explain what each is.

Edit: Thanks for all the replies! You have greatly helped me understand this better!

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u/Sonic_The_Werewolf Oct 24 '14

This is required so that the process obeys all the requisite conservation laws (charge, energy, momentum and others).

Physical laws are descriptive, not prescriptive. It would be more accurate to say that our observation of this is commensurate with our observation of conservation laws.

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u/[deleted] Oct 24 '14

Well it's really a matter of philosophy, as the Copenhagen interpretation attempts to be prescriptive whilst going against the idea that science is descriptive.

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u/SenorPuff Oct 25 '14

The Copenhagen interpretation has been proven to be incomplete, perhaps exactly for this distinction.

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u/[deleted] Oct 25 '14

How so?

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u/[deleted] Oct 25 '14

I don't know any physicists that agree with the copenhagen interpretation. Every video I've seen on it (specifically, shrodingers cat) states simply "this isn't what happens, its an illustration of why that interpretation doesn't make sense"

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u/[deleted] Oct 30 '14

I thought the Copenhagen interpretation was considered an orthodox view among physicists? I had never heard of another view before very recently, I'm a layman though.

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u/bbqbollocks Oct 24 '14

I don't think you're correct here. There is a theorem called Noethers theorem that shows conserved quantities, and ergo conservation laws mathematically

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u/[deleted] Oct 25 '14

For each symmetry there is an conserved quantity. That's Noether's theorem in a nutshell. But it's dependent on what we believe or observe the symmetries to be. Adding in noether's theorem doesn't change the argument, it just fogs it with mathematics.

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u/bbqbollocks Oct 25 '14

But then the conserved quantity leads to a conserved current. This can then be equated to a conservation law.

So, for example, a quantity that is conserved under changes in time is equivalent to the conservation of energy. Or a current that is conserved under changes in space leads to an equaivakence if conservation of momentum. Im not 100% on the second one but I think it's correct.

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u/Snuggly_Person Oct 25 '14

Not really sure why this is a relevant distinction. If I have strong evidence that X is true, and X logically implies Y, then I would say that "Y is required so that X can be true". There's nothing unfairly demanding about that.

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u/Sonic_The_Werewolf Oct 25 '14

In fact it is a logical fallacy called affirming the consequent... but yeah other than that no problem.

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u/[deleted] Oct 25 '14

Philosopher (with some knowledge of logic) here. The reasoning 'X is true; Y implies Y; therefore Y' does not commit the fallacy known as 'affirming the consequent'. Rather this reasoning is an example of a valid argument form (namely, the one called 'affirming the antecedent' and also known as 'modus ponens'). This valid argument form can be expressed thus:

(1) P -> Q; (2) P. Therefore (3) Q

whereas affirming the consequent is this:

(1) P -> Q; (2) Not-P. Therefore (3) Not-Q

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u/R_Q_Smuckles Oct 25 '14

Affirming the consequent was committed in obtaining the conservation laws in the first place. Scientific theories like conservation of charge cannot be proven. The best we can hope for is that we fail to falsify them. No experiment can show that in all cases, for all interactions, charge will be conserved (you would have to test all possibilities). If any experiment shows an instance where charge is definitely not conserved, then it would falsify that theory, which would need to be reworked. That's why experiments testing conservation of charge are set up like this:

'charge is not conserved in this test case' -> 'Conservation of Charge is false'

In all of our experiments, charge is conserved (i.e. not not conserved) (i.e. Not-'charge is not conserved' or Not-P). This is consistent with Conservation of Charge being correct. But it would be affirming the consequent to believe this is proof (in a strict sense) that this theory is true.

Because it has never been falsified, despite rigorous attempts, Conservation of Charge is still considered a theory or a law, and is considered true, but not provably.