# In-Class Activities

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Published 2022-10-09

# 7.6 In-Class Activities

# Activity 1

# The Curved Space of a 2-Sphere

# Triangles on a 2-sphere

Blow a balloon into an approximately nice spherical shape. Define the north and south poles on your balloon. Draw a set of longitudes using a fine marker. Draw the equator as well.

Form a triangle with 2 longitudinal lines and the equator, draw it out with a thick marker.

Measure the interior angles of the triangle and find the sum of the three angles.

# Geodesics on a 2-sphere

A geodesic is a generalised notion of a straight line. It is the shortest distance between two points in space. It is the line whereby a non-accelerated body will move on.

Blow another balloon into a sphere. Mark out two points on the balloon and call them NiuLang and ZhiNü. How would you draw the shortest distance, aka the geodesic, between them?