Wednesday, December 7, 2011

The Certainty in Quantum Physics

In a Scientific American guest blog on the relationship between physics and philosophy, James Lloyd writes:
"If we can’t be certain about the properties of fundamental particles, what does that say about our knowledge of nature?"
The author is referring to quantum physics, which accurately describes the probability of a given event on the scale of elementary particles, but cannot predict when (or if) it would occur.

Does quantum physics imply an inherent uncertainty in nature, as the author presumes?

No. Contrary to the claims of some leading physicists, all that quantum physics provides is certainty. Elementary particles behave exactly in accordance with the probabilities calculated using equations of quantum physics. Just because the equations do not predict which one of the possible ways an interaction would occur, it does not follow that such occurrences are causeless and, hence, metaphysically uncertain.

If not for the certainty, a quantum computer would be inconceivable.

And, "what does that say about our knowledge of nature"?

Not that it’s unreliable, as most modern philosophers jump to conclude. Rather, the achievements of physics, including those of quantum physics, are a testament to the fact that knowledge is possible, and can be obtained with certainty.

Just as an egg laid by an ostrich cannot give birth to a chicken, the facts identified by physicists cannot, in the end, invalidate factual knowledge.

Update [Dec. 08, 08:16 UTC]: Slightly edited for clarity.