What is it?

     With digital animation and computer made diagrams, orreries are an instrument of the past. But before our time these were incredibly important tools for teaching and observing our solar system.

     An orrery, named in honor of the fourth earl of Orrery, is a fairly complex instrument that is used to display and predict the alignment of the planets and moons in our solar system in relation to the sun. It gives the user a two-dimensional visual representation of how our planets are aligned and their relative motion to each other. It uses gears of very precise size to connect each rod to an orb representing each planet/moon, when the user pushes a lever the gears rotate causing the model planets to orbit one another. On the surface of the disk there are relative angle measurements, months and other planetary notes that you can align with the rotating orbs above to glean information.

    Modern orreries still exist but are few and far between, they are much more complex and accurate, some even showing three-dimensional motion. The technology has become obsolete since the age of computers and projection which can be far more detailed, accurate and not held by physical constraints. This link is an example of a modern day physical orrery and its capabilities.