Parallax

Explore 19.1 Fundamental Units of Distance to learn about the meter as a standard unit of length and how radar signals are used to measure distances within the solar system.
Astronomers have tried to measure the distance to the stars for hundreds of years, even before the telescope was invented (remember Tycho?). It wasn’t until the mid-1800s that astronomers were able to successfully measure the distance to a star - why did it take so long? In short, because they are really far away.
Parallax has been a method for measuring distance for thousands of years. The principle can be illustrated very simply. Point your index finger toward the ceiling and place it just in front of your nose. Then blink between your left and right eye. Do you notice how your finger appears to move with respect to a distant wall? Now move your finger further away from your face and repeat the experiment - you see that your finger does not move as much.
Watch the video of a Parallax Simulation to see how the orbit of the earth around the sun creates a similar effect for the apparent location of a nearby star. Watch to the end so you can see how the parallax of the star is less apparent with a low-resolution “home telescope” than it is with a high-resolution “space telescope.”
Review 19.2 Surveying the Stars to understand how stellar distances are determined using techniques like parallax, and the significance of units like light-years and parsecs in astronomy.
The Gaia Space Mission has revolutionized our ability to map out the precise location and motion of stars in our galaxy. Watch the ESA video Gaia’s Astronomical Revolution to learn more.
There are so many cool results from the Gaia Mission! Watch the brief video, Amazing Results of the Gaia Mission where I highlight a few of my favorites.