How to Understand Quantum Physics

As more than one notable scientist has observed, anyone who thinks he understands quantum physics-which describes the behavior of matter and energy at subatomic distances-really doesn't. With that proviso in mind, here's a quick introduction to the basic premises of this abstruse discipline, which has baffled the best minds of humanity since it was put together in the early 20th century.

Difficulty: Moderately Challenging

Instructions

1. Know that particles can be both "solid" and "wavy." You might think of a proton (one of the components of the atomic nucleus) as being like a billiard ball, but it in fact has a tenuous "wave" component, just like light. Physicists have shown that beams of protons or electrons will interfere with themselves, proving that these subatomic particles aren't "solid" in the macroscopic sense of the term and have some wave-like properties.

2. Know that you can't measure a particle's momentum and position with arbitrary accuracy. Known as the Heisenberg Uncertainty Principle, this law dictates that the more accurately you measure the location of, say, an electron, the more its momentum (and hence its energy) will increase, and vice versa. This doesn't reflect a limitation of our ability to measure particles; rather, quantum physics itself places limits on what can be measured.

3. Know that distant particles can be "entangled." For reasons that are way too involved to go into here, a particle light years away can instantaneously "know" what a companion particle here on earth has done, without light having had time to convey the information. This property-which has given physics and philosophers fits for decades-has been experimentally demonstrated, and is known as "entanglement."

4. Know that there's an innate element of probability. Unlike classical physics-in which you can, at least theoretically, calculate the future state of a system from the present configuration of all its particles-quantum physics has improbability at its very core. For example, it's impossible to predict exactly when an atom of a radioactive isotope will decay (which is a quantum process), only the probability that this will happen in any given time.

5. Understand that quantum physics is weird, but it isn't mystical. Despite all those books you see on the best-seller racks, quantum physics does not open some kind of "back door" to telepathy or reincarnation. (For example, that "entanglement" effect described above can't be used to mind-meld with your cousin in Peoria.) In other words, just because scientists don't understand everything about quantum physics doesn't mean that it's somehow "beyond science."

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[chetanpatil]

on 11/20/2009 It's really nice to read about quantum physics so shortly and precisely.I just want to ask , is there any criteria for determining particle or wave nature?