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The Big Bang theory for AQA GCSE Physics

The Big Bang theory

This page covers the following topics:

1. Red-shift
2. The Big Bang model
3. Dark mass and energy

Redshift is the apparent shift of wavelength of light as the source is moving away from us. When the source is at a constant distance from the person, the waves emitted will have a constant wavelength, and thus a constant colour. If the source is moved away, the distance the person will see between the two next wavefronts will be greater than the original and thus the wavelength of the waves received by the person will be greater, and thus the wave was shifted towards the red end of the light spectrum. Redshift acts as evidence for the Big Bang theory. This is because the redshift observed from distant stars and galaxies acts as evidence that the universe is moving away from us, and thus expanding. This means that a "Big Bang" must have occured so that all matter is constantly moving away from the initial point.

Red-shift

The Big Bang model states that billions of years ago, the whole Universe was a tiny, dense region of extremely high temperatures. The theory states that the whole Universe as we know it today expanded from that small region. The red-shifted light received from distant galaxies provides evidence for this model, as it suggests that the Universe is currently expanding. Cosmic Microwave background radiation (CMBR) has been detected coming from all directions in space and has a very low temperature. CMBR is said to be the remains of the energy procuded in the Big Bang and is spread thinly across the Universe, thus providing more evidence for this model.

The Big Bang model

Distant galaxies are moving away increasingly faster, and thus the expansion of the Universe seems to be acceleration. This is a phenomenon which cannot be currently explained, thus scientists have stated that the cause of this is something called dark energy. Not much is understood about dark energy other than the fact that it causes the Universe to expand increasingly faster. Dark energy is approximated to account for 68% of the Universe. Another thing which cannot be explained is the fact that galaxies rotate quicker than they should be, according to the mass of their stars. This suggests that the Universe holds a mass which has yet to be detected by humans. This was given the name of dark matter. It is approximated that 27% of the Universe is made up of dark matter. Overall, only 5% of the Universe is made of matter that can be understood by humans.

Dark mass and energy

1

How does redshift provide evidence for the Big Bang model?

The red-shifted light received from distant galaxies provides evidence for this model, as it suggests that the Universe is currently expanding.

How does redshift provide evidence for the Big Bang model?

2

Describe the phenomenon about the roation of galaxies which cannot be understood and why.

Something that cannot be understood is the fact that galaxies rotate quicker than they should be, according to the mass of their stars.

Describe the phenomenon about the roation of galaxies which cannot be understood and why.

3

Explain why the idea of dark energy arose.

Distant galaxies are moving away increasingly faster, and thus the expansion of the Universe seems to be acceleration. This is a phenomenon which cannot be currently explained, thus scientists have stated that the cause of this is something called dark energy.

Explain why the idea of dark energy arose.

4

Explain what redshift is.

If a light source source is moved away from the observer, the distance the person will see between the two next wavefronts will be greater than the original and thus the wavelength of the waves received by the person will be greater, and thus the wave was shifted towards the red end of the light spectrum. This is called redshift.

Explain what redshift is.

5

Describe the Big Bang model.

The Big Bang model states that billions of years ago, the whole Universe was a tiny, dense region of extremely high temperatures. The theory states that the whole Universe as we know it today expanded from that small region.

Describe the Big Bang model.

End of page

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