What does a higher red-shift indicate about a galaxy's motion?

A higher red-shift indicates that a galaxy is moving away from us at a faster speed.

When we observe light from distant galaxies, we often notice that the light is shifted towards the red end of the spectrum. This phenomenon is known as red-shift. The term "red-shift" comes from the fact that red light has a longer wavelength than blue light. When a galaxy is moving away from us, the wavelengths of the light it emits are stretched, making the light appear redder. This stretching of light waves is similar to the way the sound of a siren changes pitch as an ambulance drives past you, a concept known as the Doppler effect.

The amount of red-shift can be measured and is directly related to the speed at which the galaxy is receding. A higher red-shift means that the wavelengths are stretched more, indicating that the galaxy is moving away from us more quickly. This relationship was first discovered by Edwin Hubble in the 1920s and is a key piece of evidence for the expanding universe theory. According to Hubble's Law, the farther away a galaxy is, the faster it appears to be moving away from us.

In practical terms, astronomers use red-shift to estimate the distance to faraway galaxies. By measuring the red-shift, they can determine how fast a galaxy is receding and, using Hubble's Law, calculate its distance from Earth. This helps scientists map the universe and understand its structure and evolution.

So, when you hear that a galaxy has a high red-shift, it means that galaxy is not only moving away from us but doing so at a significant speed, providing valuable insights into the dynamics of our expanding universe.