History of Science Class Summary 4/29/2013

Number the Stars

This week we looked at the contributions of two 4th Century BCE astronomers - Eudoxus and Hipparchus - and their influence on mapping the sky. 

We learned that Eudoxus, a student of Plato, created a celestial coordinate system for mapping the locations of the stars.  About 150 years later, Hipparchus improved upon this sky map by adding a brightness classification for the stars.  He also thought to apply the grid of imaginary celestial coordinate lines directly to the map of the Earth, thus initiating the use of our Latitude and Longitude coordinate system.  He is known as the "Father of Trigonometry" and is credited with inventing the simple yet powerful astronomical instrument known as the astrolabe.  Using his knowledge of spherical angles and the astrolabe, Hipparchus was able to determine locations on Earth's surface and to measure geographical latitude.

---

Simple Astrolabe Design

Students reviewed the vocabulary terms from Chapter 20 to make sure they have a working knowledge of these basic mapping and astronomy-related terms:

• coordinate system
• celestial coordinates
  
• latitude
• longitude
• altitude
• horizon
• zenith
• azimuth

We then discussed the function of an astrolabe for measuring altitudes, positions and movements of heavenly bodies.  Using a simple template and some basic supplies, students created their own astrolabes, similar to the one shown in the image here.  We practiced using our astrolabes outside to measure the altitude of trees and buildings in the surrounding area.  Unfortunately, the weather did not cooperate as the rain and cold prevented us from spending much time outside, and we were unable to get an altitude reading on the sun (which was hiding behind all those clouds!).  However, I think all students were able to get the hang of using their astrolabe correctly.

For a wonderful presentation on the use, history, and inspiration of the astrolabe, please view this TED talk.

---

---

Homework

1. At home this week I have asked students to use their astrolabe to record measurements in the night sky of 1) the altitude of the moon and 2) the altitude of a star of their choice - the stars of the Big Dipper or Polaris might be easiest to locate, but I encourage you to consult a planisphere or star chart.  Please make sure you write down your findings so you can share them with the class next week.
2. Research and answer this question:  How does the International Dateline relate to Latitude/Longitude?
3. Read Chapter 22 in your textbook
4. Keep working on those science fair projects!