Category: Quantum Vs Classical Physics

By the turn of the twentieth century, classical physics had racked up a very impressive series of accomplishments. Newton’s laws of motion could successfully predict the mechanics of all macroscopic bodies. When these laws were combined with his theory of gravity, all of celestial mechanics could be described with tremendous precision. The principles of electricity… Continue reading The End of Physics?

Imagine you visit an old Civil War fort and observe the ceremonial firing of its cannons, and consider this question: if one were to stretch a large sheet of tissue paper across the cannon’s path, what are the chances a fired cannon ball would bounce off the paper rather than simply tear through? Impossible, right?… Continue reading The Nuclear Model

Although his discovery would provide the basis for every piece of electronics in our modern households, Thomson was not satisfied to stop there. Instead, he wanted to understand how exactly the electron fit into the atom’s structure. He surmised that the atom was a small sphere of matter, with a positive charge distributed uniformly throughout,… Continue reading The Plum Pudding Model

In the spring of 1889, the World’s Fair opened in Paris in the shadow of the newly-built Eiffel Tower. Six years later, while his fellow Parisians were still craning their necks to study this architectural marvel, the physicist Henri Bequerel was sitting across town, in a darkened room, wrapping rocks in paper. He was studying… Continue reading The Divisible Atom?

A number of subsequent experiments have proven this early estimate for the atom’s size to be amazingly accurate. One of the more elegant of these was conducted in Munich in 1912 by Max von Laue. Here, he and his students combined the wave theory of light with the concept of the atom to develop a… Continue reading X-Ray Crystallography

Imagine you were stranded on a desert island with only a block of pure gold and a very, very sharp knife. Given that there’d be nothing much else to do, you might just take that knife and cut the block of gold in two. Having managed that feat, you might eventually get around to cutting… Continue reading The Indivisible Atom

We have now learned about the greatest triumphs of classical physics, summed up nicely by Newton’s laws of motion and Maxwell’s equations along with a dab of thermodynamics. We will see how eighteenth and nineteenth century physicists applied these concepts to explore the microscopic world—the domain of quantum physics. We will learn how scientists at… Continue reading Early Atomic Theory

Though he’ll be forever remembered as the father of electromagnetism, one of James Clerk Maxwell’s most famous lectures had nothing at all to do with this subject. In 1873, he addressed the British Association for the Advancement of Science on another topic close to his heart. He spoke of “molecules,” though he was referring more… Continue reading A Touch of Thermodynamics

Today, we know that visible light isn’t the only kind of electromagnetic wave out there. The radio waves picked up by your cell phone and the microwaves that cooked your leftover meatloaf are both waves that fit into a broad electromagnetic spectrum. The only difference between these different types of waves is the rate at… Continue reading Electromagnetic Spectra

When Maxwell arrived on the scene, physicists had already learned that static electricity is created whenever they rubbed, say, a piece of amber with a rabbit fur. They had also discovered that a compass needle could be moved whenever a magnet is brought nearby. Given the very different nature of these effects, these two phenomena… Continue reading Maxwell’s Famous Equations