From candles to ladders: how astronomers measure very large distances in the universe
How do we know the universe is expanding? Your high school trigonometry is involved in the process.
Ever wondered how scientists know the distance to planets, stars, galaxies? Or even better, how to measure the universe’s size and its expansion? Well, they certainly don’t have a giant ruler, but they have other tools including “candles” and “ladders”.
The Parallax and 1 parsec = 3.26 light-years. Credits: astronomy.com
The easiest way to measure things far from Earth is called parallax and was discovered by ancient scientists not just the Greeks (who are usually responsible for discovering things), but several other ancient societies with knowledge of astronomy.
HOW OLD IS THE UNIVERSE?
A CENTURY ago, if you asked a cosmologist the universe’s age, the answer may well have been “infinite”. It was a neat way to sidestep the question of how it formed, and the idea had been enshrined in 1917 when Albert Einstein presented his model of a static universe through his general theory of relativity.
General relativity describes gravity, the force that sculpts the universe, as the result of mass warping its fabric, space-time. In the mid-1920s, astrophysicist George Lemaître showed that according to the theory, the universe wasn’t static but expanding– and would thus have been smaller in the past.