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# The Big Bang theory for OCR GCSE Physics

1. Red-shift
2. The Big Bang model

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.

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.

# 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.

# 2

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.

# 3

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.

# 4

What does the Big Bang model state about how the Universe started?

The Big Bang model states that billions of years ago, the whole Universe was a tiny, dense region of extremely high temperatures.

# 5

State one piece of evidence for the Big Bang model.

Red-shifted light from distant galaxies/CMBR

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