December 5, 2012 - Happy Birthday, Werner Heisenberg!

He came up with the “uncertainty principle.”

He won a Nobel Prize for his part in the creation of quantum mechanics.

And these accomplishments created a physics that baffles most of us, and yet paved the way for amazing things: transistors, microprocessors, computers, cell phones, random number generators, and lasers. All those things may seem very commonplace to you—but I urge you to contemplate how different your life would be without any of this stuff, and I point out that most of the people who have ever lived had none of it.

We do live in amazing times, truly!

Uncertain about uncertainty?

You probably know that physicists use a lot of math to explore reality. The uncertainty principle is a variety of mathematical inequalities that show that we cannot measure exactly all the physical properties of a subatomic particle. In other words, we can never know both the position AND the momentum of a particle.

It's a bit like saying that we cannot know where a car is AND what direction it is traveling, at what speed. That seems silly—I bet you want to say “of course we can!”

But quantum physics is the physics of the very, very small—and when you are looking at things that are the size of an atom or electron, they don't always behave as we in the larger world expect.

Here's one kid-friendly explanation of the uncertainty principle. (I am uncertain whether or not this explanation is exactly accurate...but what could be more appropriate for an explanation of this principle than a little uncertainty and lack of precision!)

Heisenberg and World War II

Werner Heisenberg, born on this date in 1902, was a German physicist during the rise of Adolph Hitler in Germany. Some anti-Semitic (anti-Jew) physicists in Germany accused Heisenberg of being a “White Jew” (which was in their eyes an insult), and some said he should be “made to disappear.” Why did they hate this brilliant, prize-winning, Aryan (“white” German) scientist?

Two reasons: First, Heisenberg admired Einstein's contributions to physics, and he said so to his students. At the time, Nazis hated Einstein because he was Jewish but also because Einstein was a pacifist and humanist who believed in equality.

Second, some of the second-rate German physicists who hated Heisenberg didn't understand his discoveries and theories. They wanted to stick to classical physics and ignore what they called “Jewish physics.”

Heisenberg and his work in physics were viciously attacked in German newspapers, yet Heisenberg refused to emigrate to the U.S. as Einstein and some other other German scientists (mostly Jewish) did.

Heisenberg was saved from possible punishment from the Nazis by the fact that his mother and the mother of the head of the Gestapo (Nazi secret police) were friends.

I don't want to make Heisenberg sound like a hero. He compromised himself by staying in Germany and working with the Nazis. He still taught students about Einstein's theories, but without mentioning Einstein at all. Although Heisenberg wasn't political, he thought of himself as very practical—and it seemed to him that the Nazis were going to win World War II. As the chief theorist of the Nazi's Uranium Project, he wondered about the morality of inventing an atomic bomb to help his country win the war. He angered his former mentor, Niels Bohr, who thought Heisenberg was eagerly helping Hitler to gain an atomic weapon.

In actual fact, Heisenberg and other German scientists may have deliberately sabotaged the German efforts to invent a bomb. They seemed to have concentrated, instead, on inventing a nuclear reactor, a way of creating nuclear energy.

The whole subject about what Heisenberg did or did not do during World War II is pretty controversial and to even shrouded in mystery. If you want to read more, check out the National WWII Museum's blog.

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