Although it’s true that many of the at first counter-intuitive predictions of quantum mechanics (including the uncertainty principle) follow from the assumption that quantum mechanical particles behave like waves or wave-packets, it’s not the case that physicsts simply guessed that particles were waves and saw what happened. Rather, they were led to a wave equation by attempts to explain the existing physical data.
To elaborate: Equations of a certain form are called wave equations. If you can show that a certain physical phenomenon is described by such an equation, then it must be a wave. For instance, in the 19th century James Clerck Maxwell showed that the equations of electromagnetism give rise to a wave equation predicting electromagnetic waves travelling at the speed of light. He concluded that light itself is an electromagnetic wave.
Similarly, physicists in the early 20th century wanted to understand the spectrum of hydrogen (i.e. the frequencies of light that it can absorb and emit). Niels Bohr created a model of the atom which explained this spectrum by assuming that electrons could only orbit the atom at certain discrete energy levels, but didn’t really give a satisfactory explanation of why only these levels are allowed. Erwin Schrödinger later found an equation which predicted these energy levels, and that equation (the Schrödinger equation) had the form of a wave-equation.
A couple years earlier Louis De Broglie had also proposed that particles had wave-like properties. In that case, the prediction was based on the discoveries by Max Planck and Albert Einstein that the blackbody spectrum and the photoelectric effect (respectively) could be explained by assuming that light (which was previously thought to be a wave) had particle-like properties.
So it’s not quite right to think that physicists guessed there was a wave-particle duality and then found this resulted in predictions that agreed with experiments. What actually happed was something more like this: physicists found certain perplexing experimental results, discovered that those results could be explained by postulating a wave-particle duality, and then found that this assumption led to even more predictions which were themselves confirmed by experiment.
Don’t get me wrong. There may very well be aspects of our universe which are beyond our comprehension. My point was just that I don’t think the counter-intuitiveness of quantum mechanics is due to it being beyond our comprehension, so much as the fact that we just don’t have much experience with it in our daily lives. If you’d never seen a ball thrown through the air, the fact that it moves in a parabola might also be counter-intuitive to you. But most people have seen this many times since a young age, so an intuition for such things is formed.
At any rate, physicists certainly hope that in the end our universe will prove to operate according to laws that are simple enough for us to understand. Maybe this is a futile hope, but so far they are encouraged by the fact that many seemingly complex phenomena have turned out to be described by relatively simple laws. There’s no particular reason that the interactions of subatomic particles or the formation of stars had to be comprehensible to us as human beings, and yet they are. This perhaps-surprising simplicity is in fact one of the main reasons I personally have chosen to study physics.
Actually, unlike quantum mechanics string theory hasn’t yet been experimentally confirmed. In fact, it hasn’t yet been developed to the point where it can make a definitive experimental prediction which we could use to test the theory. (Some would dispute this claim, but all the proposed “predictions of string theory” I’ve ever seen don’t really “test the theory” in the usual sense.) For something to be considered a “scientific theory” it needs to be testable, and for this reason string theory is sometimes called a proto-theory rather than a full-fledged theory. That said, there are some reasons to hope that the theory can eventually be developed to the point where it makes testable predictions – at least enough so to keep a lot of smart people interested in working on string theory. (Plus, even if string theory turns out to be wrong as an an ultimate theory of everything, it is still a mathematically rich structure which may lead to interesting physical insights. In particular, certain types of quantum field theory are actually mathematically equivalent to string theories.)
String theory certainly doesn’t predict the masses of the elementary particles. Some hope that it will eventually explain why they have the masses they do, and this hope has been much touted. However, there are some recent results which suggests there may be 10^500 possible solutions to string theory, in which case such a prediction may prove unobtainable. Time will tell . . . .
You don’t have to travel very far before reality/nature goes beyond intuitive sense.
Can you understand how your body works, how the chemical/electrical pathway operate, how the enzymes work, how the cells function, what the brain does?
Can you explain even how a plant works?
Can you explain weather and the interrelatedness of wind/sun/clouds/water?
Can you explain basic electricity?
The earth isn’t even intuitively round.
My point is just that wanting an intuitive understanding of the basic composition of the universe is really asking a lot. You should look at it the other way round and marvel that we have come up with explanations of so much.
tim314, Oh, granted on string theory. I was just using that as an example that we can explain the underpinnings in a variety of ways not limited to cutting things smaller and smaller until they are point-sized.
It’s worth mentioning, by the way, that the Uncertainty Principle (or something analogous to it) shows up in all wave theories, not just quantum mechanics. There’s also a version of it which would apply to a vibrating guitar string, or to waves on the ocean, or amber waves of grain. Quantum mechanics, it turns out, happens to be a wave theory, and so it has an Uncertainty Principle.
The best way to understand the Uncertainty Principle that I’ve heard is to look at the difficulty in determining the fequency components in a classical wave You don’t need to understand tht math of Fourier Series and Transforms to see the problem if you look at it this way:
Suppose there is a radio wave that you are trying to measure and someone asks you to determine the frequencies in the wave at an exact point in time-- IOW, you are not allowed to sample the wave, you have to measure it at only one, infinitely small, point in time. Well, you can’t do it. A wave simply doesn’t have a frequency at a point in time. In order to determine the frequencies, you need to sample the wave over a length of time. And the shorter the time that you sample the wave, the less accurate your measurement of the frequency components is going to be. Uncertainty! So, just as we say it makes no sense to ask what the exact position and momentum of a particle* is, it makes no sense to ask what the frequency of a wave is at a specific time.
*A particle whose position is defined by a wave function, that is.
