**The Great Physicists from Galileo to Einstein, George Gamow, 1961** (Dover reprint, 1988)

What exactly is “quantum mechanics?”

The word “quantum” comes from “quanta,” which refers to packets of energy, or quantifiable increments in mass. But, what does that mean?

Traditionally, people thought that energy and mass followed simple, continuous “straight” lines. That is, in classical “Newtonian” physics, if you look at a car traveling from point A to point B, you can get the time it takes to cover that distance. Measure again at point C, and you’ll probably be able to calculate acceleration. If the car’s acceleration doesn’t change between points, you’ll be able to plot distance and velocity curves that will let you work backwards to where the car started moving, and forward to predict where it will be at any given time in the future. Take more measurements to get the accuracy you want. The lines will be continuous, and you can pick any value for time that you want (3.21 seconds, or 1.45 microseconds) and get the correct answer for velocity and distance.

This changed as physicists got to where they could measure individual units of light and mass. Light seemed to be traveling in packets, and electrons needed specific amounts of energy to jump from one energy level to the next. The graphs were no longer straight lines, instead turning into areas of probability for where something might be, or when. The new physics that emerged at the beginning of the 1900’s was based on these light and energy units – quanta. And to distinguish this from the rules of physical mechanics (i.e. – the mechanics that Newton described) we got “quantum mechanics.” That is, the formulas of very tiny, very fast things operating at atomic (and subatomic) particle scales. Which ties Einstein, Schrodinger, Heisenberg, Bohr, Pauli and Gamow together.

George Gamow (1904-1968) was a theoretical physicist and cosmologist who help develop quantum theory, from the 1920’s to the ’30’s. Later, he started writing about physics, with at least 10 books on science, 6 in the Mr. Tompkins fiction series (where Tompkins learns about physics), and 8 textbooks (I may have missed one or two). He liked combining the science side with backgrounds on the people involved in making the discoveries.

George’s purpose with “The Great Physicists” book is to show the development and progress from early philosophy to classical mechanics as classified by Newton and his contemporaries, and then demonstrate how all of that broke down in the face of discoveries of radiation, proof that there is no ether surrounding us in space, and the ability to measure individual atoms. He continues with Einstein’s theories supporting curved space, time dilation, and the idea that mass and energy are related. George finishes with quantum mechanics as it had become in the mid-1950’s, after stalling from the 30’s onward. But, along the way he spends almost equal time talking about each of the physicists as people, relating personal details where available, and anecdotes when known.

There’s a certain amount of duplication between **30 Years That Shook Physics** and this book, especially with the background stories on people like Bohr and Pauli. There’s not a lot of really difficult theory in the book, and George keeps the math to a minimum. Even so, there were a couple paragraphs that I skipped over because I didn’t feel like trying to follow the proofs he was providing. But, the book does flow well, and I did learn a lot more about quantum mechanics than I had before. In fact, I did study a lot of this when I was in university in the early 1980’s, but no one had clearly explained to me what “quantum” represented, or what Heisenberg had done in proving that uncertainty is an unavoidable side-effect of the universe we occupy.

Again, Dover simply reprinted the original book without corrections or updates, leaving George scratching his head over certain puzzles that no one had been able to solve, and not knowing what the future path of physics would be. He stops just short of speculating how gravity could be unified with the other 3 forces, as if he was on the doorstep of String Theory, but hadn’t realized there was a door there.

I enjoyed reading **The Great Physicists**, and I do recommend it to anyone that wants to learn more about what Pauli, Einstein, Bohr and the others were like. It’s not a real textbook, but it is entertaining.

George also presented an interesting puzzle that illustrates the importance of understanding your frame of reference.

Say person A is in a speed boat on a river, going upstream. On the back of his boat is a half-full bottle of whiskey. When the boat reaches a bridge passing over the river, the whiskey bottle falls overboard and immediately starts floating downstream. After 20 minutes, person A realizes that the bottle is gone, and he immediately turns around and heads back downstream to rescue the bottle, at the same velocity with respect to the river as before. He picks up the bottle a mile downstream of the bridge. Question: How fast is the river flowing?