# How Astronomers Determine the Distance and Age of the Universe

TLDR Astronomers use various methods such as measuring the speed of light, parallax, and the redshift to determine the distance of objects and the age of the universe. These methods involve observing the movement of stars, calculating the absolute brightness of light sources, and measuring the velocity of galaxies.

### Timestamped Summary

00:00 Astronomers determine the distance of objects and the age of the universe through observations and measurements of light, using the cosmic distance ladder.
02:17 The distance to the moon can be accurately measured using the speed of light, and reflectors left on the moon by the Apollo missions allow for precise measurements within centimeters; for stars closer to Earth, a method called parallax can be used to determine distances.
03:50 Parallax can be used in astronomy to measure the distance to stars by observing their apparent movement against the background of stars at different times of the year, and if the angle of the object's apparent change is one arc second, then the distance is defined as one parsec, which is equal to 3.26 light years.
05:25 Knowing the absolute brightness of a light source allows for the calculation of its distance using a simple formula, with Cepheid variable stars and type 1A supernovas being common standard candles used for this purpose.
06:53 Hubble's law states that galaxies move away from Earth at speeds proportional to their distance, and this can be measured using the redshift, which is the Doppler effect applied to light.
08:25 The Hubble constant, which measures the velocity of galaxies, can be used to calculate the age of the universe, which is currently estimated to be 13 billion 787 million years old.
10:08 The size of the universe is connected to its age through Hubble's law, which allows for the measurement of both.
Categories:

# How Astronomers Determine the Distance and Age of the Universe

Astronomical Distances and the Age of the Universe
by Everything Everywhere Daily