In 1931, a Charlie Chaplin movie called City Lights premiered in Hollywood.

Chaplin's guest of honor at the premiere was none other than Albert Einstein.

As the two men strolled toward the theater and tuxedos, throngs of people cheered them,

screaming and pointing at these two very different celebrities.

Indeed, Chaplin turned to Einstein and said,

they cheer me because they understand me.

They cheer you because no one understands you.

It's a charming joke, but it does get at a deep truth.

Even today, most of us don't really understand Einstein's main achievement,

the theory of relativity, which brings up an uncomfortable question.

How then do we know that relativity is true?

The answer is other scientists.

They can point to experiments.

Einstein's theory makes certain predictions about the world.

Scientists can therefore run experiments and see whether the results match Einstein's predictions.

And historically, the results have matched time and time again.

So what were those experiments?

That's what we're going to explore in this three-part series.

When we think of Einstein today, we think of the rumpled genius, the wise sage,

the worldwide celebrity.

He is Saint Albert.

But in this series, we're going to go back to a time when Einstein was a nobody,

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