Sunday, August 12, 2007

Fun Science 'Save the Moon' part 2

In part 1 we have watched the Moon in orbit around the Earth at different speeds. The program Space Simulation draws 10 times per second the Moon and the Earth in accelerated motion - 1 second represents one day. In this second part we verify the speed of the Moon around our planet.


1. Run the program What do you observe?

The Moon does a fairly stable circular orbit around the Earth - as shown in the above screenshot. The speed of the Moon is set to 998 meters per second.

2. How to calculate the speed of the Moon around the Earth

The Moon is in average at 384,400 kms from the Earth. It does a full tour around our planet in 28 days - remember the full Moon shows up every 28 days because it occupies the same position in our sky at this interval. The perimeter of a circle of radius 384,400 is obtained by multiplying 384,400 by two times Pi. So we have the following formula (distance in meters and time in seconds give us the speed in meters per second)

speed = distance / time = 384,400,000 * 2 * 3.14 / ( 28 * 24 * 60 * 60 )

You can use you own calculator or Google's calculator to get the result: 998 meters per second

We have confirmed our simulation. The Moon rotates around the Earth at a speed of one kilometer per second.

No comments: