# AQA GCSE Physics – Space Physics – Red Shift

Redshift in space occurs when the light from an object in space, such as a
star or galaxy, is stretched out and becomes redder in color.

This happens because the wavelength of the light, which is the distance between the
peaks of the light waves, is getting longer. This is known as the Doppler
effect and it happens because the object is moving away from us.

When an object is moving away from us, the light waves get stretched out,
making the wavelength longer and the light redder. Scientists call this “red
shift” and it’s used to measure the speed and distance of objects in space.

The more the wavelength of the light is stretched out, the faster and farther
away the object is moving.

On the other hand, when an object is moving closer to us, the light waves
get squished together, making the wavelength shorter and the light bluer.
This is called “blue shift”.

Red shift is also used to study the history of the universe. Because light
takes time to travel to us, when we observe an object that is far away, we
are also observing it as it was in the past.

By studying red shifted light from distant objects, scientists can learn about the early universe.

Image from here – https://earthsky.org/upl/2012/06/500px-Redshift_blueshift.png

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There is an observed increase in the wavelength of light from most
distant galaxies.

The further away the galaxies, the faster they are
moving and the bigger the observed increase in wavelength.

This effect is called red-shift.

The red shift is a phenomenon in which the wavelength of light emitted by
an object moving away from an observer is shifted to longer (red)
wavelengths.

This is due to the Doppler effect, which states that the frequency of a wave (such as light) will appear to change for an observer if the source of the wave is moving towards or away from them. In the case of a red shift, the source of the light is moving away from the observer, resulting in a lower frequency (longer wavelength) of the light.

Spectral lines, on the other hand, are specific wavelengths of light that are
emitted or absorbed by atoms or molecules in an object. These lines can
be used to identify the composition of an object, as different elements and
compounds have unique spectral lines. The study of spectral lines is known
as spectroscopy.

When an object is moving away from an observer, the
spectral lines will also appear to be shifted to longer wavelengths, which is
known as a red shift in the spectral lines.

In summary, the red shift is the phenomenon of an object’s emitted light
having its wavelength stretched out, usually due to the object moving away
from the observer.

Spectral lines are specific wavelengths of light that can be used to identify the composition of an object.

When an object is moving away from an observer, the spectral lines will also appear to be shifted to longer wavelengths, which is known as a red shift in the spectral lines.

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The observed red-shift provides evidence that space itself (the universe) is expanding and supports the Big Bang theory.

The Big Bang theory suggests that the universe began from a very small region that was extremely hot and dense.

Since 1998 onwards, observations of supernovae suggest that distant galaxies are receding ever faster.

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There is still much about the universe that is not understood, for example dark mass and dark energy

## Extra reading – for information read this on The Big Bang, Dark Matter and Dark Energy

The Big Bang theory is the widely accepted scientific explanation for the
beginning of the universe. It suggests that the universe started from a very
small and extremely hot and dense point, known as a singularity.

This singularity began to expand and cool, eventually leading to the formation of
stars, galaxies, and other celestial bodies.

Since 1998, scientists have been using observations of supernovae, which
are extremely bright explosions that happen when a star runs out of fuel, to study distant galaxies.

These observations have shown that distant galaxies are moving away from us at an ever-increasing speed.

This is known as the “expanding universe” and it’s one of the strongest pieces of
evidence that supports the Big Bang theory