This 11-minute video lesson looks at Potassium-Argon (K-Ar) dating and it can be used to date very old volcanic rock and the things that might be buried in between. [Cosmology and Astronomy playlist: Lesson 79 of 85]

This 12-minute video lesson clarifies the effect of axial precession on the calendar and the date of perihelion and aphelion. [Cosmology and Astronomy playlist: Lesson 73 of 85]

This 2-minute video lesson provides a correction to the previous video about quasars. [Cosmology and Astronomy playlist: Lesson 36 of 85]

This 9-minute video lesson discusses quasars. [Cosmology and Astronomy playlist: Lesson 35 of 85]

This 17-minute video lesson discusses the radius of the observable universe. [Cosmology and Astronomy playlist: Lesson 8 of 85]

In this 11-minute video lesson Sal makes random predictions for the year 2060. [Cosmology and Astronomy playlist: Lesson 85 of 85]

This 10-minute video discusses redshift and the Doppler Effect. [Cosmology and Astronomy playlist: Lesson 10 of 85]

This 9-minute video lesson looks at refraction and focuses on refraction in seismic waves. [Cosmology and Astronomy playlist: Lesson 53 of 85]

This 8-minute video lesson examines the scale of distance from the solar system to the closest stars. [Cosmology and Astronomy playlist: Lesson 3 of 85]

This 10-minute video lesson looks at the scale of the Earth and the Sun. [Cosmology and Astronomy playlist: Lesson 1 of 85]

This 13-minute video lesson examines the size and scale of the solar system. [Cosmology and Astronomy playlist: Lesson 2 of 85]

This 13-minute video lesson examines the scale of our galaxy. [Cosmology and Astronomy playlist: Lesson 4 of 85]

This 11-minute video lesson attempts to comprehend the size of the universe and the scale of the large. [Cosmology and Astronomy playlist: Lesson 57 of 85]

This 13-minute video lesson attempts to comprehend the scale of the small: from honey bees, to cells, to viruses, to atoms. [Cosmology and Astronomy playlist: Lesson 58 of 85]

This 5-minute video lesson looks at seasons and why they aren't dictated by the Earth's closeness to the sun. [Cosmology and Astronomy playlist: Lesson 69 of 85]

This 9-minute video lesson considers seismic waves and how they are related to the composition of the Earth. It covers both S-waves and P-waves. [Cosmology and Astronomy playlist: Lesson 51 of 85]

This 7-minute video lesson looks at images of star fields and nebulas. [Cosmology and Astronomy playlist: Lesson 20 of 85]

This 12-minute video lesson looks at how to measure stellar distance using parallax. [Cosmology and Astronomy playlist: Lesson 23 of 85]

This 9-minute video lesson provides another introduction to stellar parallax. [Cosmology and Astronomy playlist: Lesson 22 of 85]

This 2-minute video lesson provides clarification on parallax. [Cosmology and Astronomy playlist: Lesson 24 of 85]