A not-all-together sane way of showing a class how retrograde motion works!


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Here's how to show your students why stars twinkle in the night sky!


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The geometry behind moon phases.


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Read more: Phases of the Moon

Sunspots are "dark" spots on the surface of the sun.

Here's how to show students why they appear dark.


This demonstration shows how atmospheric scattering filters 

the colour of the sun during a sunset.


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Read more: Why Are Sunsets Red?