Observe Gravity

Gravity in Action!

Select a gravity animation to view by clicking on the planet icon. Use on the "Play" button to start the animation. To pause the animation, click "Pause". The "Step" button allows you to view the animation between each calculation.

Earth bound orbits

Satelites and the moon.

These animations find the length of time for an orbit as well as the highest and lowest points of the orbit. The space station grid is laid out in meters and uses an interval of 100 seconds between frames. The Earth/Moon system uses grid spacing of 10,000 meters and time spacing of 20,000 seconds.

Sun bound orbits

The inner solar system.

Asteroids - Earth crossing and the asteroid belt.

Outer planets - plus Pluto, the former planet.

How it Works

The gravitational force between objects is calculated using Newton's laws and displayed on the screen as "Force". This force is added between each frame to the current motion of each object.
The "Motion" of each object goes up or down by the amount of force between it and other objects on each timestep.
The motion of each object is added its prior "Location" to calculate the new location of the object.

View the inner Solar System!

Click here for access

Get planet positions on particular dates
http://www.fourmilab.ch
"...lets you view the solar system in a variety of ways for any date between 4713 B.C. and 8000 A.D. ... given orbital elements in the form published in the IAU Circulars, the orbit and position of asteroids and comets can be plotted."