The Doppler Effect: solving for the speed of the source

Telescopes

Why is Magnetism Important on the Sun?

Where Does The Sun's Energy Come From?

What is the Basic Structure of the Sun?

Neutrinos: Messengers from the Center of the Sun

An Introduction to Stellarium

Skydiving and Terminal Velocity

Using The SteadyPix Phone Adapter

Using The SkyScanner 100

Try this one simple trick to understanding moon phases

Addendum: "How Close Do I Have To Get To The Moon To Be Pulled Harder By Its Gravity Than Earth's?"

How Close Do I Have To Get To The Moon To Be Pulled Harder By Its Gravity Than Earth's?

Where is the "balance point" between the Earth and Moon?

Comparing Telescope Light-Collecting Areas

How do we represent really small numbers?

A Demonstration of Fiber Optics

Diffraction Through a Narrow Slit

Image Formation by Half a Lens

Demonstration of the Inverse Square Law for Light

image Formation by a Lens or Mirror

Diffraction Gratings and Spectra

Diffraction Through a Circular Hole

Seasons

Moon Phases