# DDES Chapter 16

If you have any questions about the course, feel free to ask the author of the book! You have to register in order to ask questions, but registration is free, and we won’t share your information with anyone.

# Links for the Sixteenth Chapter

Distance Measurements using Parallax
This video gives a great explanation of parallax and how it measures universal distances.

Astronomical Unit
This video shows you the distance scale of the universe and explains the astronomical unit.

Units for Distance in Space
This video starts with normal distance units and goes to AU, light year, and parsec.

Motion of the Solary System Through Space
We generally think of the sun as being motionless at the center of the solar system and all planets orbiting around it. However, the sun is in motion through the universe as well. This animation shows you what our solar system looks like as it travels through space.

The Heliosphere and How It Protects Us
This video explains how the sun’s heliosphere protects us from universal cosmic rays.

The Heliosphere and Its Motion
This animation has no sound, but it starts at the sun and then zooms out to show the heliosphere and how it moves through space.

Timelapse of Star Motion in the Sky
This animation has no narration but shows you how the stars move throughout the night. It then shows you a picture that traces that motion. The wide-angle lens distorts the shape of the horizon, but the timelapse is excellent.

Very Nice Illustration of Absolute and Apparent Magnitude
When you click on the link, you will get a picture that shows a star (Vega) at its actual distance from the earth. You can read its apparent magnitude and distance. Then, you can click on the star and move it, to see how that affects its apparent magnitude. If you put it on the 10 parsec mark, then you have its absolute magnitude. You can also do this for the sun, and you can choose other stars using the dropdown box.

Cepheid Variables
This video explains how Cepheid variable stars can be used as standard candles.

The HR Diagram
This video explains goes through the features of an HR diagram.

HR Diagram Animation
This video converts an image of stars into an HR diagram of those stars. The narrator talks about stellar lives, which is one way the HR diagram is interpreted, but that is pretty speculative. The real value of the video is showing how the HR diagram develops from color and brightness.

Redshift and The Expansion of the Universe
This animation has no sound, but shows how light traveling through the universe (the wave in the animation) stretches with the expansion of the universe, causing the redshift.

Young-Earth Creationist Cosmology
This is one example of a theory of the universe that allows for the earth to see light from billions of light years away, even though the earth is only thousands of years old.