May 29 – Theory of Relativity: Confirmed!

These measurements agreed with the prediction made by Albert Einstein in his Theory of Relativity. It was one of the first confirmations of the theory, and Eddington’s work quickly became both famous and controversial.

Albert Einstein

Einstein wasn’t the first to suggest that really large objects could bend light; Henry Cavendish and Johann Georg von Soldner both pointed out that Newton’s theory of gravity makes this prediction. Einstein came up with his Theory of Relativity in part to explain things not explained by Newtonian principles, and he came up with a different prediction for the amount that light should bend in a gravitational field. Einstein’s prediction was twice as large as Soldner’s!

Sir Arthur Eddington realized that an upcoming total solar eclipse would allow scientists to test the new Theory of Relativity. During a total solar eclipse, the Moon entirely covers the Sun, and stars that appear in the sky near the Sun can be observed. Eddington’s team did observations simultaneously in a city in Brazil and in Sao Tome and Principe, on the west coast of Africa, and their measurements found that light was deflected (bent) the amount predicted by Einstein.

Brazil, in South America, is colored green. The teeny island nation Sao Tome and Principe, off the coast of Africa, is inside the orange circle.

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Sir Arthur Eddington

Eddington’s results, as I said, were widely publicized, making the front page of most newspapers. (How often does the result of a scientific experiment make the front page of newspapers?) According to Wikipedia, this publicity had the effect of making Einstein and his theory world-famous.

Eddington’s Results: Einstein Is Right!
But…Is Eddington Right?

I mentioned that Eddington’s results were also controversial. Some scientists suggested that there were errors and possibly confirmation bias. Wow! Confirmation bias sounds bad, doesn’t it?

Actually, it’s really common, and it plagues all of us, not just scientists. Confirmation bias is the very human tendency to see what we expect or want to see—to only notice the things that confirm a belief or opinion or hope, and not to notice things that conflict with the belief / opinion / hope. Notice that we do this without knowing we are doing it! We cannot completely trust our own brains!

Confirmation bias is one reason that doctors don’t often operate on or diagnose loved ones, and detectives don’t investigate loved ones. Confirmation bias tells us that, when we keep up with current events, we should read and listen to several different perspectives—keeping in mind the fact that our minds will tend to better remember the stuff we agree with, and will tend to forget the stuff we prefer not be true.

We all indulge, to some extent, in wishful thinking—but if we are aware of this tendency, we can reduce its effect on our memory and reasoning.

Scientists try to eliminate confirmation bias in several ways:

By doing double-blind tests – in which neither the experimenter nor the subject knows what to expect. For instance, when testing a new medicine in a double-blind test, neither the experimenters nor the subjects know which bottles hold medicine and which hold flavored and colored water…

And by repeating observations.

The people who suggested that Eddington’s results might be tainted by this bias were right to question the results. They turned out to be wrong—Eddington was right—but the questioning itself was right-on.

Does that make sense to you?

You see, Eddington was an early supporter of Einstein’s theory, and he had already become the major explainer of the theory in Britain. So he had every reason to want the results of his observations to back up the theory as correct.

Naturally, many scientists wanted to repeat the observations to see if the results stood up. And Eddington’s results—and Einstein’s theory—were backed up by observations made during a solar eclipse in 1922 and many, many times since then.


Play “Guess the Rule”

A hypothesis is a guess about what’s going on. It tends to be a thoughtful guess, what we call an “educated guess,” not just some random idea.

If someone said that she had one specific rule in mind, and your goal was to guess her rule, your job would be to come up with one or more hypotheses (guesses) about what the rule is—and then to test your idea. The person with the rule (let’s call her the Ruler) gives you one example that follows her rule:

2, 4, 6

One of the students tests these three numbers:

10, 12, 14

The Ruler says, “Yes, that follows my rule.” The next student tests these three numbers:

18, 20, 22

The Ruler says, “Yes, that follows my rule.” Another student suggests:

234, 236, 238

The Ruler says, Yes, that follows my rule.”

Do you think you know what the rule is?
What three numbers would you test, when it’s your turn?

If you’re interested in more, here is a website with some great diagrams about the geometry of the universe. I love this stuff!