Measuring Characteristics of Planets


Obtain characteristics of planets without direct measurement.


Procedure: Medium

Concept: Hard



While we have great telescopes to observe neighboring planets to distant galaxies, we do not have any direct way to measure how big the sun or the moon is, even with astrophysicists obtaining the data they can and looking for clues that can tell us about the vast universe. There is no scale big enough to weigh a planet, (or that would properly function as a matter of fact). However, by observing how they interact with each other, this information can be indirectly measured.

Our solar system is under a delicate balance of forces which enables each planet to orbit on its orbit track. These forces include gravitational forces that hold the planets in orbit around the sun. These dynamics were well understood and stated by a German astronomer Johannes Kepler.

This is explained in three laws:

  1. The first law states that all the orbits are in the shape of an ellipse.
  2. The second law states that the area a planet travels is equal for given speed.
  3. The third law says the square of the period is directly proportional to the cube of its distance.

We know our earth's period and distance from the sun very well. So by knowing the period of any other planet in our solar system, we can figure out how far they are!

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