November 29, 2022
The Earth is on average 93 million miles from the Sun. This distance is often referred to as an astronomical unit (AU). By measuring distances in AUs, it allows scientists to understand the large scale of our solar system more easily. For example, Pluto is approximately 39 AU from the Sun. This means that Pluto is 39 times farther from the Sun than Earth is.
By observing Venus passing in front of the solar disc, scientists were able to measure an astronomical unit. They observed the transit at many locations around the world, and used the parallax shift to determine the distance between the Earth and the Sun. This image shows the Venus transit of 2004. Image credit: Jan Herold