Astronomy
How stellar parallax anchors the cosmic distance ladder
Quick fact
Astronomers measure the distance to a star by observing its apparent shift against distant stars from opposite sides of Earth's orbit—a baseline of about 300 million kilometers. This technique, called stellar parallax, is so precise that a star's distance in parsecs is simply the inverse of its parallax angle in arcseconds.
Why this is interesting
Have you ever noticed how objects seem to shift when you look at them from one eye and then the other? Stars do the same thing—only on a cosmic scale—and measuring that shift lets us map the universe.