Doppler shift of light (Part 1 of 4) Fly a rocket at amazing speeds and see how light waves are doppler shifted. By observing the light waves emitted by a space ship students learn about red and blue shift.
	Red shift (Part 2 of 4) Follow in the footsteps of scientists by observing the hydrogen spectra from distant galaxies. What can you deduce about the motion of the galaxies?
	The expanding universe (Part 3 of 4) This application allows you to view the expansion of the universe and take measurements.
	The age of the universe (Part 4 of 4) If you know the expansion rate of the universe, you can run things backwards to estimate the age of the universe. This application does just that!

If these applications are used in sequence they provide a logical progression for teaching about the expanding universe.

1. Doppler shift
By observing the light waves emitted by a space ship students learn about red and blue shift.

2. Red shift
Students observe the hydrogen spectra from near and distant galaxies. Using the knowledge gained from application 1 they can deduce that all galaxies are moving away from each other.

3. The expanding universe
This animation illustrates the conclusions of application 2, namely: the universe is expanding.

4. The age of the universe
This model shows that if the rate of expansion is known scientists can work backwards to estimate the age of the universe.

Note: Subscribers to eChalk can access the member's area where these resources can be resized to fill the entire screen area.