# Classical vs Quantum mechanics

1. Jul 9, 2011

### Laptu

Which is better at determining whether the universe has a cause? From my basic understanding, quantum mechanics is generally accepted to be indeterministic whereas classical mechanics is deterministic. Posted in the philosophy question because this is related to the first premise of the Kalam cosmological argument i.e. whatever beings to exist must have a cause. The obvious answer to me seems like classical mechanics due to the fact that it operates at a macroscopic scale. But, want to see others opinion.

2. Jul 9, 2011

### Ivan92

I would say Quantum Mechanics.

Source: http://en.wikipedia.org/wiki/Quantum_mechanics

Seems to be more fit than Classical Mechanics.

Source: http://en.wikipedia.org/wiki/Classical_Mechanics

3. Jul 10, 2011

### dx

"Does the universe have a cause" is not really a well defined question neither in classical nor quantum mechanics. However, the main conceptual difference between quantum mechanics and classical mechanics is indeed the fact that the existence of the quantum of action makes it impossible to combine unrestrictedly the causal and spacetime descriptions. In classical mechanics, it is assumed that a system may be observed without disturbing it appreciably. However, the quantum implies that any observation of a system involves an interaction with the measuring instruments which cannot be neglected. Thus, neither the system nor the agencies of observation can be ascribed an independent reality in the ordinary sense. The definition of the state of a system claims the elimination of all external disturbances, and so, because of the quantum, any observation will be impossible, and the concepts of space and time lose their immediate sense. On the other hand, if we permit interactions with measuring bodies, and unambiguous definition of the state is no longer possible, and hence the causal mode is no longer applicable. Thus, in quantum theory, causality and spacetime coordination are complementary.

4. Jul 10, 2011

### Ryan_m_b

Staff Emeritus
The KCA is easy to refute as an argument. The argument goes;

1) Everything that begins to exist has a cause

2) The universe began to exist

C) The universe has a cause

Premise 1 is dodgy because firstly it has not been proven and secondly proponents usually say that the universes cause does not apply. It is a weak argument to say that this cause must be an exception to the premise with no evidence.

Premise 2 is also dodgy because it is unknown if the universe began at all (it could be an infinite, cyclic universe). There's also the problem of definition, can time ever "begin".

Lastly the conclusion doesn't get you anywhere, yes it is a good conceptual question that can lead us to do good science in an attempt to explain if the notions of "before" and "cause of" the big bang. However as the KCA is usually used to promote the existence of an intelligent cause it is rarely used to invoke good reasoning, usually the argument goes "the universe must have a cause therefore god".

5. Jul 10, 2011

### wuliheron

The universe is by definition "all that exists" and, therefore, any causal agent separate from the universe would defy logic and the law of identity. For either theory to be more applicable would require that you at least first create clearer definitions of the terms.

6. Nov 7, 2012

### osman ibn ali

Don't virtual particles refute the first premise??

7. Nov 8, 2012

### Jimmy Snyder

I don't think either classical or quantum mechanics would be better at answering this question. After all, quantum mechanics is just classical mechanics in the limit as 0 approaches h. Put another way, if the graininess of particles is orange, and the repetitiveness of waves is yellow, then wave-particle duality is nothing more than amber waves of grain

8. Nov 9, 2012

### Drakkith

Staff Emeritus
Nothing in the universe is ever created out of nothing and without a cause. This seems to imply, to me at least, that the universe has either always existed, or was created out of something that existed prior to the universe. Of course it may be possible that the universe was created out of nothing as well, as that can't be ruled out either since we cannot observe everything in the entire universe at all points in time and we may have just "missed" seeing a particle created from nothing. Hmm...looks to me like trying to apply logic to this problem gets us absolutely nowhere.

I think a better question is can we can even determine if the universe has a cause. If so, what would we look for?
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