John Norton, our professor for today, is sitting on a bench in the Monroeville Mall, feet planted firmly on the ground. When shoppers walk near enough, he can feel the flooring tremble slightly beneath his sneakers.

Fiona Hanson, Press Association via AP A fiberglass head of Albert Einstein is delivered to the Science Museum in London Tuesday, for a new exhibition: "Move Over Einstein: The Next Generation Is Here." Click photo for larger image. Related article Doctor kept Einstein's brain in jar 43 years

"Feel that?" he asks, his Australian accent in full lilt. "That's Einstein."

When you spend an afternoon with Norton, you quickly understand that Einstein is not only beneath your shoes, but nearly everywhere else, too. He's in your CD player, your cell phone, your slice of pizza, your cup of tea.

Norton, chair at the University of Pittsburgh's Department of History and Philosophy of Science, is one of the world's pre-eminent Albert Einstein experts. This year -- the 100th anniversary of Einstein's landmark papers, and tomorrow's 50th anniversary of his death -- Norton has been forced to cut his course load to make time for speaking engagements in London, Berlin, Israel and elsewhere.

But you don't have to stray far from home for an Einstein refresher course. The world is Norton's campus, and the shopping mall makes a fine classroom.

So back to the bench. What we have here is a brief illustration of Einstein's general theory of relativity -- that the universe is not a static, immovable backdrop, but something that responds to the items, actions and gravitational forces within it.

"It was one of his most powerful intuitions," Norton said.

That is Lesson One in this impromptu lecture series. Lesson Two comes at the nearby Make-a-Wish coin funnel, where nickels and dimes spin concentrically toward the black hole at the bottom.

Those funnels, as it happens, make a nice visual representation of the special theory of relativity. In Einstein's mind, the fabric of space-time, Norton explained, is warped by the distribution of mass and energy within it. Imagine pulling a beach towel taut, then dropping a bowling ball onto the towel, creating a funnel-like depression in the middle.

The towel is Einstein's space-time, and it bends around heavy objects. "This is how Einstein got the Nobel Prize" in 1921, Norton said, for his many mind exercises in theoretical physics.

Norton himself has to perform some mental calisthenics when asked why he made a career of studying Albert Einstein.

	John Norton, chair at the University of Pittsburgh's Department of History and Philosophy of Science, is one of the world's pre-eminent Albert Einstein experts.

"I'm not sure," he says. "I think I just wanted to know how he did it."

Now 51, Norton has been in Pittsburgh for two decades, coming from Sydney by way of a short stop in Princeton, N.J., Einstein's base. He is married to Eve Picker, the Pittsburgh real estate developer who specializes in loft apartments, and he maintains with authentic earnestness that a Pittsburgh winter beats an Australian summer any day.

Norton's next lesson is a few steps from the coin funnel at the American Cafe, where he asks a baffled waitress if he can have a quick look at the pizza oven. What ensues is an introduction to heat radiation, the process by which heat energy is transferred from object to object. Einstein, hitchhiking on work done by Max Planck, helped show that electromagnetic radiation behaves as though it were a particle, as well as a wavelength.

"It's exactly the same thing with light," Norton says. In light, we call it the photoelectric effect -- the idea that light energy comes in waves as well as photon packets. Further, if energy of a certain frequency is shone on certain metals, the photon energy can knock loose electrons, meaning the metal is now emitting its own energy.

And voila, we have the science behind a fluorescent light bulb, Norton says. The bulb creates light when the energy inside collides with the bulb's phosphor coating.

It's also the basic science behind solar calculators, street lamps and automatic doors, not to mention the concept we now know as the laser -- Light Amplification through Stimulated Emission of Radiation. Einstein lay the frame for the laser in a 1917 paper, and today we use lasers in CD players, DVD players, laser pointers, even to treat certain types of surface cancer.

Norton's just getting started. From the mall's second floor, he looks down on a kiosk selling Dakota watches. Clocks are key in explaining Einstein's special theory of relativity. Before Einstein, it was assumed that time ran independent of clocks, and clocks were simply the measuring instruments. After the special theory, Einstein calculated that, for example, a clock in motion ticks more slowly than a static clock. The effect is called "time dilation," one of many brain-cramp-inducing side effects of his special theory.

This effect also means that the clocks aboard global-positioning satellites in outer space run differently from the clocks on Earth. And that means that the onboard GPS clocks must be set differently from their earthly counterparts. Otherwise, the satellites wouldn't be able to pinpoint the location of the GPS receivers in your cell phones or your more sophisticated GPS devices. Without the daily time adjustment, the GPS satellites would say you're about seven miles from your actual location.

We're at the halfway point now, and Norton heads to the food court. It's tea time. He buys a cup of hot water and tea bag from Gloria Jean's coffees, and asks the clerk for a side of honey.

"We don't have any honey," the clerk announces grimly.

Hmmm. Anything syrupy, then?

Norton and the clerk compromise with a shot-glass-size cup of vanilla syrup. Up next is a lesson on viscosity, diffusion and the calculation of atomic size.

Before Einstein came along, there was a phenomenon known as "Brownian motion," the idea that pollen grains or any other particles zigzag randomly in water, presumably due to the impacts of millions of H2O molecules. It's also known as the random walk.

Einstein used that theory to prove that molecules existed, even though they are too small to be seen. To demonstrate, Norton dumps the syrup into the hot water. Common sense says the syrup will settle, but actually, its soluble parts will diffuse randomly through the water. Same goes for the soluble tea bits.

What does that mean? To Einstein, it meant the speed of diffusion, the change in viscosity, the temperature of the water, and the size of the visible particles were all indirect measurements of Brownian motion, and by calculating those factors, he could provide evidence of the very existence of atoms.

"The calculation was so difficult," Norton says with understanding in his voice, "he actually got it wrong."

No matter. His groundwork, later corrected by French chemist Jean Perrin, would launch physics in a new direction. What once had been principally a meditation on thermodynamics would become a science combining atomic and kinetic theory.

It's one of Einstein's least-known, but most important, contributions to physics. This theory was included in his doctoral thesis in 1905, the same year he proposed special relativity and the idea of light quanta.

From the food court, Norton jogs to the nearby elevator. Time for another lesson in gravity, general relativity and the "equivalence principle" upon which relativity is erected.

He steps in, hits the second-floor button and waits for the upward jerk. That brief sensation of increased gravitational pull, Norton says, would play out even if the elevator were in outer space, without Earth's gravity.

That's because an elevator in space, accelerating at the same rate as Earth's gravitational pull -- 9.8 meters per second squared -- produces the same gravitational effect as a stationary elevator on Earth. So if you're in the Earth elevator, and you drop your car keys, they fall at the same speed as they would in the moving space elevator, even though the space elevator is nowhere near a star, planet or any other object that creates gravity.

Got it?

Out of the elevator, it's a short walk to Brookstone, the gadget store. Norton spies an array of magnifying glasses, binoculars and telescopes. He holds one of the magnifying glasses up to the ceiling, for a small-scale light-bending experiment. The glass scatters the light in different directions, producing a fractured image that distorts reality.

"A star," Norton explains, "can focus light.

That's because of something called the "gravitational lensing effect" -- the notion that light rays passing near a massive object are bent by the gravitational field of the object. That means, if you're observing a solar eclipse and you think you see a star next to the sun, you're really seeing an optical illusion. The star's actual position is thrown off by the sun's light-sucking powers, so what you see is the star's "observed" position.

Isaac Newton pondered this effect in the early 1700s, but Einstein was the one who brought it into focus, so to speak. He calculated the value by which light would be sent from its normal trajectory, according to the gravitational tug of a particular celestial body. That effect has practical applications today in astrophysics and cosmology.

At the Barnes & Noble bookstore now, Norton engages the patient woman at the help desk, and asks her to use her computer to do a key word search for any inventory bearing the name "Einstein." The search produces 54 items -- children's videos, biographies, novels and any number of self-help books that use Einstein's name in the title, just to lend intellectual credibility to the work.

One is called "The Einstein Factor: A Proven New Method for Increasing Your Intelligence." Another is "Einstein Never Used Flashcards: How Our Children Really Learn."

This, perhaps, is Einstein's most remarkable legacy, as much as the laser or the atomic bomb -- his image. For all he predicted, Einstein never saw this coming. A few years before he died, he wrote to a friend: "You imagine that I look back on my life's work with calm satisfaction, [but] there is not a single concept of which I am convinced that it will stand firm, and I feel uncertain whether I am in general on the right track."

The world has since concluded that he was.

"He is everywhere," Norton announces proudly, not just in science journals, but diffusing unexpectedly across the American landscape, in books, movies, educational flashcards, and, of course, your CD players and your afternoon tea. His likeness, it would appear, has taken a long, random walk of its own.

Class dismissed.