Scientists use red shift to calculate the age of the universe by measuring the rate at which galaxies are moving away from us. The further away a galaxy is, the faster it is moving away from us, and the greater its red shift. This relationship between distance and red shift is known as Hubble's law.

By measuring the red shift of galaxies, scientists can determine how fast they are moving away from us. This information can then be used to calculate the age of the universe. The current estimate for the age of the universe is 13.8 billion years old.

Here is a more detailed explanation of how scientists use red shift to calculate the age of the universe:

1. Scientists measure the red shift of galaxies. This is done by comparing the wavelength of light emitted by a galaxy to the wavelength of light that is observed on Earth. The difference between these two wavelengths is called the red shift.

2. Scientists use Hubble's law to calculate the distance to galaxies. Hubble's law states that the farther away a galaxy is, the faster it is moving away from us. The amount of red shift in a galaxy's light tells us how fast it is moving away, and this information can be used to calculate its distance.

3. Scientists use the distances to galaxies to calculate the age of the universe. The age of the universe is calculated by dividing the distance to a galaxy by its speed. This calculation gives us the amount of time it has taken light to travel from the galaxy to Earth. Since the speed of light is constant, this tells us how long ago the light was emitted by the galaxy.