The Earth

In this segment of our “How far away is it” video book, we introduce the most basic distance measurement techniques, and illustrate their use in my back yard. These include direct measurement and triangulation. We introduce minutes and seconds of arch in a degree, and describe a theodolite. We then triangulate the Grand Canyon, Mt. Everest and more. We then introduce lightening as an example where some basic scientific understand about observed phenomena is needed to help determine how far away it is. We discuss what lightening and thunder are, and the speed of sound in air to calculate how far away a lightening strike is. Next, we cover “going there” as a technique for determining distance, using our atmosphere as the prime example. From balloons to the space station, we cover the troposphere, stratosphere, mesosphere and thermosphere. Then, we illustrate how geometry can play a key role in determining distance as we cover in detail how Eratosthenes actually calculated the size of the Earth in 200 B.C. We use how many students could fit inside the Earth to highlight just how vast the Earth really is. We conclude our coverage of the Earth with a look at distances to a number of cities using pictures and video taken by the international space station at night. We start close to home and move out to the most distant cities – much like we’ll be moving from neighboring celestial objects out the furthest reaches of space in subsequent video book chapters. We then introduce the distance ladder and show how we have just built the foundational rungs in the ladder. We end with a preview of the coming distant ladder rungs and the video book segments organized around them.