Sizes of Earth and the Sun



We always hear of “astronomically large numbers,” but who can really wrap their brains around these concepts? Curious people wonder how do scientists arrive at such numbers….

Finding the distance to Venus is easy. Anyone can visually measure Venus’ maximum elongation. If you then draw a right triangle and crunch a couple numbers on a calculator, you can quickly learn that Venus is 72% of the distance of the Earth from the Sun. Then if you take measurements during a transit of Venus from different parts of the Earth, you can use simple trigonometry to discover that the distance from the Earth to the Sun is about 93 million miles. Armed with this knowledge and the fact that the Sun has an angular diameter of a half-degree, you can do a couple more trig calculations and find out that the Sun is 864,000 miles in diameter.

These calculations were first performed centuries ago, and any high school student learning trigonometry can prove these numbers. So why don’t our students learn such things in school? Why instead do science textbooks hand down such numbers and other scientific conclusions strictly on authority, with no explanation of the methodology?

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