In this segment of our “How far away is it” video book, we cover distances inside our Solar System.

We start out with a brief history beginning with how Nicolas Copernicus used planetary retrograde motion to help move us from the Earth-centric view to the Sun-centric view of our Solar System. We work our way through the contributions made by: Tycho Brahe and his detailed observations made with mural quadrants and sextants; Kepler and his mathematics of elliptical orbits; and Galileo and his observations using the newly invented telescope. We conclude this history with Newton and his theory of gravity. Gravity gives us the first opportunity to explain the inverse square law that will play such a central role in celestial distant measurements as we move out to the stars.

We then explain planetary parallax as an extension to triangulation and use it to determine the distance to the Moon. We also illustrate all the additional information that becomes available once the distance is known, such as diameter, area and volume.

Next, we take a look at the surface of Mars, the orbit of Mars and the Earth and the distance of Mars from the Sun, followed by distances of all the planets and Pluto from the Sun.

We then focus on Jupiter to gain a feel for its size. We watch the comet Shoemaker Levy collide with Jupiter. We explain Lagrange Points and cover Jupiter’s Trojan and Greek asteroids orbiting two of these points. This takes us to Earth’s Trojan asteroid, 2010 TK7.

Then, after covering the Kuiper Belt, we turn our attention to the Sun. We triangulate the Sun with Venus to calculate our distance from the Sun – one Astronomical Unit. With distance to the Sun known, we calculate its diameter, surface area and volume; the length of Earth’s orbit; the Earth’s velocity around the Sun; and with that, the Sun’s mass.

Next, we use Jupiter’s moon Io to calculate the speed of light and with that we calculate how long it takes the Sun’s light to reach the Earth.

We end with adding the parallax rung to our distance ladder.