This simulation illustrates the changes in the orbit of Halley's Comet over the centuries. You can run the simulation either forward or backward to see how the orbit changes. The comet is highlighted in the table to make it easier to watch the changing figures, and it's easy to see how the orbital period varies considerable from its average of about 76 years.
The simulation start date is set to 1st January 1986, which is shortly before Halley's Comet last reached perihelion. The evolution time step is set to one year, which is why the Earth appears to be fixed in position while the simulation runs. You can try changing the evolution time step to one day at any point in the simulation, to watch the short term movements of the comet and planets.
Since different computers run at different speeds, you may need to edit the evolution time step to get the simulation to run at an acceptable rate.
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