Space Physics: Red-shift

Red-Shift and the Doppler Effect

When a wave source is moving relative to an observer, there is a change in observed frequency and wavelength, termed the Doppler Effect.
This effect can be observed for any type of wave, including light and sound.
When a light source is moving away from us, its light appears more red than it would if it was stationary. This is known as red-shift.
Similarly, when a light source approaches us, its light is more blue due to the decrease in wavelength. This is referred to as blue-shift.
Red-shift is characterised by an increase in wavelength and decrease in frequency and energy. Conversely, blue-shift involves a decrease in wavelength and an increase in frequency and energy.

Red-Shift in Astronomy

In the field of astronomy, red-shift is a key piece of evidence supporting the Big Bang Theory.
Virtually all distant galaxies are moving away from us, as indicated by the red-shift of light they emit.
The larger the observed red-shift, the further away the galaxy is.
It has been observed that the further away a galaxy is, the faster it seems to be moving away. This is known as Hubble’s law.
These observations support the idea that the universe is expanding, with galaxies moving away from each other in every direction.

Cosmic Microwave Background Radiation (CMBR)

Another significant evidence for the Big Bang Theory is the Cosmic Microwave Background Radiation (CMBR).
This is the radiation left over from the early universe, shortly after the Big Bang occurred.
The CMBR is considered as the ‘afterglow’ of the Big Bang and it has been detected in all directions of the universe.
The discovery of the CMBR contributes to the model of an expanding universe from an initial singularity, known as the Big Bang.

The Big Bang Theory

According to the Big Bang Theory, the universe began from an extremely hot and dense point around 13.8 billion years ago.
The universe has been expanding since then, which is supported by the observed red-shift in distant galaxies and the CMBR.