May Earth be Revolving around the Sun?
Ninth graders explore how Aristarchus used the position of the half-full Moon to estimate the distance to the Sun, and how he made a great error, but still figured out that the Sun is much larger than Earth.
9th Science 3 Views 2 Downloads
How Old is it Really? - How Do We Know that the Earth is 4.6 Billion Years Old?
Eight neat slides lead to the understanding of how geologists have determined Earth's age. Most of the slides are dedicated to explaining the absolute dating method of assessment. Color diagrams display radioactive isotopes and a graph...
9th - 12th Science
Exponential Decay Formula (can skip, involves Calculus)
Sal continues his discussion of decay by showing students the math involved in determining how much a substance is left after one half-life, two half-lives, and even three half-lives have gone by. He sets up a general function of time...
12 mins 7th - 10th Science