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Astronomy

The Cosmic Distance Ladder: From Parallax to Standard Candles

Quick fact

The first rung of the cosmic distance ladder, stellar parallax, only works for stars within about 1,600 light-years. To reach farther, astronomers link this to Cepheid variables, whose brightness pulses are tied to their true luminosity, letting us measure distances to galaxies millions of light-years away.

Why this is interesting

Have you ever tried to guess how far away a mountain is by squinting? Astronomers face a similar problem, but for stars and galaxies trillions of times farther away. How can we measure distances that are simply impossible to reach with a ruler?