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What is a Sphere?

What is a sphere?

Summary

  1. Something like a basketball or baseball is like a sphere
  2. All points on a sphere are the same distance from the center
  3. The radius is the distance from the center to any point on the sphere
  4. A sphere can have many radii (pronounced 'ray-dee-eye', plural for radius)
  5. The diameter is twice the radius
  6. A sphere can also have many diameters
  7. Extending the radius shown to the opposite side forms a diameter of the circle drawn
  8. We can have a great circle anywhere there's a diameter
  9. Cutting a sphere along a great circle gives us two identical solid halves called hemispheres

Notes

    1. All points on a sphere are the same distance from the center
    2. A line segment drawn from the center to any point on the edge of the sphere is a radius
    1. Two radii that make a straight line segment form a diameter
    2. Radii (pronounced 'ray-dee-eye') is plural for radius
    1. Any line segment passing through the center that connects two points on the sphere forms a diameter
    1. A great circle can be drawn around any diameter of the sphere
    1. 'Circumference' is the distance around the circle, or its perimeter
    1. 'Bounded by a great circle' means the sphere shape stops at the great circle
    2. A great circle forms the flat surface of a hemisphere when you cut a sphere in half
    3. The prefix 'hemi' means 'half'