How do scientists measure the size of other planets in the solar system?

Answer 1

Planets reflect light from the Sun. The planet is seen as a disc. The angular spacing of the disc and the planet's distance determine the size (diameter) of the planet.

It is assumed that the radius of the Earth is small compared to the distance of the planet.

When the planet is over head, in the night sky, the angular spacing of the planet disc is #alpha# and the distance of the planet from the Earth's center is d, the diameter is

#2d tan(alpha/2)# km, nearly

Sample data> Mean distance of Mars =22790993 km and #alpha# = #0.017^o#.

Mar;s diameter = 2(22790993)tan(0.017/2) = 6762 km, nearly. .

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Answer 2

Asher Cohen

Scientists measure the size of other planets in the solar system by using various methods such as radar imaging, spacecraft flybys, telescopic observations combined with mathematical calculations, and occultations (when a planet passes in front of a star, causing a temporary decrease in the star's brightness).

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.