Iman+Salam


 * THE PHYSICS BEHIND THE ASTROLABE**

//What is an Astrolabe?// This instrument you see in front of you is called an Astrolabe. It was a navigation-compass like object that people (especially Arab scholars followed by the Greeks) used to depend on. An Astrolabe shows how the sky looks like at a specific place at a given time

Astrolabes helped people with so many tasks such as navigating on land by using the stars as reference points. According to the 10th-century astronomer Al-Sufi, an astrolabe could perform a thousand tasks useful in astronomy, astrology, navigation and surveying, estimating heights and distances. You can also use an astrolabe to figure out the current time, determine the time of a celestial event, or simply as a reference of positions of bodies like the sun and moon. But we will only focus on a few of those tasks and the way that Astrolabes function.



__The Different Parts of an Astrolabe:__
 * -Rete, which corresponds to the position of the stars.**
 * -Plate, used to the coordinate system**
 * -Mater, includes some scales and puts all the parts together**

__Stereographic projection concept:**__ So, How can we represent a 3D image of the whole sky that surrounds us into a portable 2D dimension device? Well, the idea is actually somewhat simple, Imagine that the Earth is at the center of the universe and surrounding it is the sky projected onto a sphere. Each point on the surface of the sphere is mapped through the bottom pole on to a flat surface where its then recorded. So the North Star corresponds to the center of the device.

The Ecliptic which is the path of the sun, the moon, and the planets corresponding to an offset circle The Bright Stars correspond to little daggers on a reet. The Altitude corresponds to the plate system

It brings two co-ordinate system that fit perfectly, there's the position of the sun, moon, and planets on the movable reet and then there's the location on the sky that seems from a certain latitude on the back plate.

As you can see, there are so many science elements related to the Astrolabe such as Astrology,gravity, time, and distance. But I only covered 3 of those elements such as Astrology, time, and distance. So, how can we tell the time from an Astrolabe? 1It inclydes a ruler than could be lined up relation to the star. So you pick a star and align it with the ruler, after that, you look at the astrolabe side that includes the drawings and names of the stars. After going through all that process, you will know the exact time, and how the sky looks. Would you rather have an iphone that could only tell the time? Or an Astrolabe that not only tells you the time, but the distance between us and the stars, what the sky looks like at that particular time, and it could do other calculation as well.

The man in the picture is using the astrolabe the correct way.

References: -http://astrolabes.org -http://www.ted.com/talks/tom_wujec_demos_the_13th_century_astrolabe.html -http://www.hps.cam.ac.uk/starry/isaslabe.html -http://www.cod.edu/middle/history/astrolabe.pdf -http://www.geog.ucsb.edu/events/department-news/669/the-astrolabe-a-mathematical-jewel/