Forty-Three Arcseconds
Mercury's oval orbit slowly turns around the Sun, by 574 arcseconds a century. Newton's laws, counting the pull of every other planet, account for only 531 of them.
Did 43 missing arcseconds prove Newton wrong?
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Science · Physical Science
Chapter 1: Measurement and the Nature of Science
A theory that explains everything predicts nothing.
Mercury's oval orbit slowly turns around the Sun, by 574 arcseconds a century. Newton's laws, counting the pull of every other planet, account for only 531 of them.
Did 43 missing arcseconds prove Newton wrong?
Make your guess to turn the page.
Still to come: 10 pages · Lab · Words to Know · What We Learned · 4 questions · Explain It in Writing · Open Questions
The idea this lesson is working on — Students say experiments "prove" hypotheses, and the word hides the logic: passing a test supports a general claim, while one solid failure can refute it. The book sets the idea against Newton, well supported for two centuries and then limited by Mercury, and against the lab, where a result that could have gone the other way did not. Ask: what result would have shown this hypothesis wrong? The idea to reach is supported, not proven.
A theory that explains everything predicts nothing — A useful scientific claim rules something out. If no possible observation could contradict it, it cannot be tested. The Neptune and Vulcan story is the honest complication: a failed prediction can be rescued by an extra assumption, and deciding whether that rescue is science or evasion depends on whether the new assumption makes its own testable prediction. Le Verrier’s did, twice; one came true.