Understanding why correlation does not imply causality (even though many in the press and some researchers often imply otherwise).

This 10-minute video lesson looks at the beginnings of life on Earth. Life and photosynthesis start to thrive in the Archean Eon. [Cosmology and Astronomy playlist: Lesson 39 of 85]

This 10-minute video lesson looks at the formation of the Earth which is a the byproduct of a local supernova. [Cosmology and Astronomy playlist: Lesson 38 of 85]

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]

Data on Chinese / U.S. balance of payments. [Economics playlist: Lesson 17 of 20]

Sal discusses the conditions of matrix dimensions for which addition or multiplication are defined. Created by Sal Khan.

This lesson compares rational number and orders them from least to greatest using the number line. [Developmental Math playlist: Lesson 132 of 196]

This lesson demonstrates how to compare whole numbers. [Developmental Math playlist: Lesson 7 of 196]

This 10-minute video lesson provides an introduction to 2nd order, linear, homogeneous differential equations with constant coefficients. [Differential Equations playlist: Lesson 13 of 45]

This 8-minute video lesson continues the discussion from the previous video and shows how to find the general solution. [Differential Equations playlist: Lesson 14 of 45]

This 6-minute video lesson continues the discussion from the previous videos and introduces some initial conditions to solve for the particular solution. [Differential Equations playlist: Lesson 15 of 45]

This 9-minute video lesson continues the discussion from the previous videos and provides another example using initial conditions. [Differential Equations playlist: Lesson 16 of 45]

This 10-minute video lesson looks at what happens when the characteristic equations has complex roots. [Differential Equations playlist: Lesson 17 of 45]

This 10-minute video lesson continues the discussion of what happens when the characteristic equation has complex roots. [Differential Equations playlist: Lesson 18 of 45]

This 10-minute video lesson concludes the series on complex roots of characteristic equations and demonstrates an example with initial conditions. [Differential Equations playlist: Lesson 19 of 45]

This 18-minute video lesson provides an introduction to the Dirac Delta Function. [Differential Equations playlist: Lesson 41 of 45]

This 12-minute video lesson gives the first example of solving an exact differential equation. [Differential Equations playlist: Lesson 6 of 45]

This 8-minute video lesson provides some more examples of exact equations. [Differential Equations playlist: Lesson 7 of 45]

This 10-minute vidoe lesson provides one more exact equation example [Differential Equations playlist: Lesson 8 of 45]

This 10-minute video lesson provides intuiton on exact equations including the chain rule using partial derivatives (not a proof; more intuition). [Differential Equations playlist: Lesson 4 of 45]