In this segment of Mr. David Butler which is named “How far away is it”, he introduces the most basic distance measurement techniques, and illustrate their use in my backyard.

These include direct measurement and triangulation. He talks about minutes and seconds of arc in a degree, and describe a theodolite. He then triangulates the Grand Canyon, Mt. Everest and more.

Mr. Butler then introduces lightening as an example where some basic scientific understand about observed phenomena is needed to help determine how far away it is. He discusses what lightening and thunder are, and the speed of sound in air to calculate how far away a lightning strike is.

Next, he covers “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, he illustrates how geometry can play a key role in determining distance as the video explains in detail how the Egyptian/Greek genius polymath Eratosthenes actually calculated the size of the Earth in 200 B.C from Egypt. Butler uses how many students could fit inside the Earth to highlight just how vast the Earth really is.

He concludes his 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.

He starts 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.

He then introduces the distance ladder and show how we have just built the foundational rungs in the ladder. He ends with a preview the coming distant ladder rungs and video book segments organized around them.