What is a rotating frame?

Imagine you had a green planet orbiting a yellow star. But you wanted to keep the green planet at the 3 o'clock position relative to the yellow star. You could pick up your computer monitor and rotate it to keep the green planet in the 3 o'clock position. But this wouldn't be very convienent. It's far easier to use the rotating frame feature. With the rotating frame feature turned on, Gravity Simulator rotates the display for you. Using the Rotating Frame Adjustment window available in the View menu, you can set the period with which the frame rotates. If you choose an object from the dropdown list, Gravity Simulator will do its best to match the period of the rotating frame with the orbital period of the object. Fine tuning may be necessary on your part using the + and - buttons.

Why would I want to do that?

Rotating a frame is a convienent way to expose certain resonances between two different objects. For example, imagine you had two asteroids locked into a 1:1 resonance with a planet by orbiting the planet's Lagrange 4 and 5 points in tadpole orbits. In a non-rotating frame, these asteroids would appear to have a similar orbit to the planet. But once you rotate the frame and match its period with the planet's period, it becomes obvious that the asteroids are trapped in the planet's L4 & L5 points as they trace tadpole-shaped paths.

In a non-rotating frame, the asteroids appear to have similar orbits to the planet. But in a rotating frame, the relationship between the asteroids' orbits and the planet's orbit becomes obvious as the asteroids trace tadpole-shaped paths around the planet's L4 & L5 points.