Astronomy
Parallax: Measuring Distances to Nearby Stars
Quick fact
The nearest star system, Alpha Centauri, has a parallax of only about 0.75 arcseconds—equivalent to the width of a human hair seen from 1 kilometer away.
Why this is interesting
Have you ever noticed how your finger seems to jump when you close one eye and then the other? Astronomers use this same effect, but with the entire Earth's orbit, to measure the distances to stars.