Backyard Solar System

Its March and the weather is warming up and I got a chance to set up my scale model solar system, finally. I needed a basketball. (and a pump)

As long sufferers of this blog probably already know, I adhere to the model of Tycho Brahe/ Astronomia Danica model of our solar system.

The only difference between Astronomia Danica model of Longomontanus is that he adopted the diurnal spin of Copernicus. Well, he did make a few refinements to Tycho’s model.

It seems like Longomontanus might have been a bit more adept at geometry, being a little younger than Tycho and not having been self taught like Tycho; plus spending so much time at Tycho’s side and learning from the best.

I can tell you that he is harder to read than Tycho, technically. He expects you to know spherical geometry ahead of time. Tycho is less academic than Christian. I’m not positive Tycho read Greek but Longomontanus did without a doubt.

I digress.

Either way, the two models relative to sizes and distances are nearly identical. Longomontanus had a slightly larger distance for his AU than Tycho had.

I am using his AU which is of course based upon Earth semidiameters. He placed the mean value of the Sun at 1288 Earth semidiameters. This results in a Sun that is 5.8 times the diameter of Earth. Copernicus/Maestlin made the Sun to be ~6 times. Whether this was due to Copernicus’ erroneous value for his latitude or poor instrumentations or only using a few observations I do not know. However, Christian had ten years worth of observations since he was at Uraniborg that entire time. Nobody had as much data as they did up until their time. (maybe ever)

Regardless, 5.8 or 6 is in the same ballpark so it isn’t very important to our backyard model.

So we set the basketball to the size of the Sun in the model which gives us a very nice fit to a Ping-Pong ball for the size of Earth and a small ball bearing for the size of the Moon. In terms of AU this puts us at ~81 feet distant from the basketball to the camera, or Earth’s point of view. The Moon would therefore be about 3.5 feet away from the camera/earth.

Right from the first viewing the sizes of the Moon and Sun were spot on. I did this very much on the fly and of course the wind kicked up right as I got the camera out. Nevertheless, it was a fun exercise. My camcorders and DSL both had too long of a focal length to work. The camera phone worked much better optically but, I didn’t have a tripod set up for a phone so I did the best I could holding it by hand. I will make a better set up in the future on a calmer day to hopefully get some better syzygies framed up and possibly mimic some eclipses.