Measuring Characteristics of Planets
Obtain characteristics of planets without direct measurement.
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:
- The first law states that all the orbits are in the shape of an ellipse.
- The second law states that the area a planet travels is equal for given speed.
- 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!
Personalizing Your Project
- What do you want to measure? Density? Mass? Distance?
- There are measurements known already with great accuracy. How does your measurement correspond to these values? Where would the error come from?
- Can you predict when the next eclipse will be? How does an eclipse change the gravitational force you feel?
- If you couldn't find any values, how would you measure it yourself?
Things to Consider
- Make sure you cite the sources properly
- Be aware of error bar of values used.
- This is a thought experiment. There is are no physical dangers.
Google Key Words
To do more research on measuring characteristics of planets, try typing these words into a Google search.
- Rotational Motion
- Kepler's Law
- Centripetal Force
- Gravitational Force
- Planet Database
- Introduction to Modern Astrophysics by Bradley W. Carroll, Dale A. Ostlie either edition
- Six Easy Pieces By Richard P. Feynman (Chapter FIVE)