When I tell people I'm a physicist, they usually act all impressed. "Oooh, that's so hard!" While that's nice ego-boo, I have to admit to a certain level of bemusement that people are so willing, and so proud, to say, in essence, "I'm stupid".
OK, I'm not really bemused. We have a very strong cult of thought in this country that being smart is dangerous. But that's a different rant.
In reality, physics is not particularly more demanding of brainpower than anything else you can become an expert in. Humans are really good at making our three-pound lumps of grey jello into powerful computers on just about any subject. It's just that most people don't care to do so with respect to physics.
Physics is, to be sure, highly mathematical and abstract. But compared to, say, financial derivatives? Tax law? People who can remain friends with their exes? Nah. Physics is just another set of skills and talents.
Back when I was in graduate school, I tutored for extra money. Freshmen in Physics 102 were always at their most worried, if not their most befuddled, when the profs got to the unit on relativity.
And I'll admit, it took me probably about three different classes' worth of relativity before I started to get it on the level when you know you really understand something.
Einstein's theory of special relativity is taught at the intro level with a lot of whiz-bang about time paradoxes and space paradoxes and the like. Here's what I told my students: Ignore it. All you need to know about relativity is contained in the equations. Just apply the equations and you'll get the right answer and you don't have to worry about whether it makes sense.
And I still maintain that's true. You still have to set the equations up properly and read off the result in the right way, but there's no more to it than earlier in the semester when you learned out to set up equations for mechanics, like firing a cannonball or moving a lever. It's a trick, of course: by the time you can set up the equations properly, you can tell whether the answer makes sense.
Einstein is an iconographic smart man. And he was, indeed, brilliant. But not in the way most people think of him. Special relativity was inevitable. Einstein's special brilliance was in asking the question and understanding the answer, not in some grand deductive leap. Newton was more creative than Einstein in that respect. Einstein was building on other people's work, whereas Newton was working in a much emptier idea-space.
Here's the background on special relativity.
Back in the mid-1800s, James Clerk Maxwell, a Scottish physicist, wrote Maxwell's equations, one of the first examples of a unification theory. It said that electricity and magnetism were aspects of the same thing, governed by a consistent set of equations. Maxwell was standing on the shoulders of giants: he based his work on the laws of Gauss, Faraday, and Ampere. His particular contribution to the theory was assembling it into one place and adding a single term that symmetrized the equations.
In fairly short order, people realized a couple of amazing things about Maxwell's equations. First, you can use the equations to create a wave--an electromagnetic wave--of oscillating electric and magnetic fields. Second, this wave propagated itself at the speed of light. Now light was unified with electricity and magnetism.
Hendrik Antoon Lorentz, a Dutch physicist, noted something peculiar about these equations, however: They cared how fast you were moving. The speed of light and the behavior of electricity and magnetism seemed to depend on your particular speed. In technical terms, the equations were not invariant under a Galilean transform.
That's a very troublesome idea. In principle, for a sensible universe, the laws of physics should be the same for everybody all the time. (Technically, only for everybody in inertial frames.) Lorentz sat down and said, OK, if Maxwell's equations are invariant, let's work backwards and figure out what kind of transform we get.
He got some very peculiar-looking equations now called the Lorentz transform. Like the Galilean transform, they were a set of rules for how stuff looked when you went from standing by the side of the road to riding in a car. But unlike the Galilean transform, they said light, electricity, and magnetism work the same for the guy by the side of the road as they do for the guy in the car.
Lorentz knew he was on the right track, because his transform looked like the Galilean transform when you were dealing with small speeds. And that's small compared to the speed of light, which pretty much meant all speeds that anybody in the late 19th century was used to dealing with.
Something peculiar fell out of the equations, though. Like Maxwell's equations producing the speed of light as a byproduct, the Lorentz transform said the speed of light is a limit. The equations break down as you reach the speed of light.
This was the situation when Einstein came in. in 1900, he published his paper on special relativity. His particular contribution was not the invention of grand new ideas. His contribution was: Let's assume Lorentz's equations are right, i.e., that this is how the universe really works. What can we deduce? And he followed the math: Under Lorentz transforms, moving clocks run slow and moving objects get shorter, and other results increasingly paradoxical to people used to living at slow speeds. He called it relativity because the results are relative. If you're moving, I see your wristwatch running slow. But to you, I'm the one that's moving, i.e., I'm moving relative to you, and you see my wristwatch running slow.
Recognizing how both of us could be right about the other's wristwatch is Einstein's special contribution. Not the math, not the stuff most folks would recognize as smart. That came from Lorentz and Maxwell and Gauss, Faraday, and Ampere. Einstein did build on the math, to be sure. One consequence of a Lorentz transform is that the equation expressing the kinetic energy of an object changes. A extra term based on the mass of the object shows up. Einstein's famous equation E=mc^2 is the trivial case (for a motionless object) of this new energy equation.
Einstein showed that a universe operating under invariant Maxwell equations, using Lorentz transforms, with a fixed speed limit of the speed of light, had some peculiar properties at very high speeds, but was consistent and sensible. He suggested ways that these properties could be tested. That's good science. That's great science. But it's not science so brilliant that it should forever mark physics as an achievement beyond common intelligence.
Posted by Greg at August 26, 2002 3:40 PM