The Earth-centric model of the Solar System was first proposed by the Greek astronomer Ptolemy around 150 AD. That logical, but foundationally incorrect, model endured for 1500 years until Copernicus suggested a simpler explanation for the movement of the planets. It took over 200 years before most people came to believe that Copernicus was correct. Discoveries made by Kepler, Galileo, and Newton all helped to show that a Sun-centric model was how things really were "in the wild."
When we gave a FirstLook of Hubbard Scientific's Celestial Globe in September, some readers were confused as to how that globe could properly represent the heavens. The question reminded us of something Sensei Gleason often says in class when explaining an Aikido technique: "You must see with your eyes, but don't let what you see fool you, because what you see is not what's happening." OK, as cryptic as that explanation may be, that is exactly what is going on with the Celestial Globe. An explanation of how to setup the Celestial Globe for the FirstUse will make clearer how it works.
The Celestial Globe is designed to properly illustrate the relationship of what someone on Earth would see when they look up to the sky. Imagined that you are tiny person standing on the surface of the Earth sphere under the clear globe. Everything is relative to that specific point of view . In other words, the globe is constructed such that if you point it North, set the date and time, then look through the globe , the constellations you will see through the globe are the same ones you will see up in the sky.
Since everything is relative to the the user, setting up the Celestial Globe for use is actually quite simple. The first step is to orient the tilt of the globe (ie: set the latitude). To set the Globe for a given spot on Earth (Boston in our case), just position the sphere and turn the knob until the desired location (North America for Boston) is facing straight up. This will orient the clear sphere properly at the appropriate latitude. For us here in Boston, that is about 42º.
Where the stars are at different times is then just a matter of moving the clear globe to the desired time marker. To do that, just set the month (November) of the year. This is done by rotating the clear surface until the desired month marking aligns with the time dial. This has the effect of shifting the clear constellations sphere until the right ones are "up in the sky."
With the Celestial Globe properly set up, we can now use it to visualize all kinds of apparent astronomical movements. We need to stress that they are APPARENT movements because they are what someone standing outside looking up would see, NOT what is actually happening for real. However, even thought the geocentric model is not how things really are, it is still a useful way of representing the heavens and an excellent way to learn, as long as we keep in mind what is REALLY going on. [Permalink] - Celestial Globe Setup