11+RED-SHIFT+AND+CMB

3.17 Describe that if a wave source is moving relative to an observer there will be a change in the observed frequency and wavelength. 3.18 Demonstrate an understanding that if a wave source is moving relative to an observer there will be a change in the observed frequency and wavelength. 3.19 Describe the red-shift in light received from galaxies at different distances away from the Earth. 3.20 Explain why red-shift of galaxies provides evidence for the Universe expanding. 3.21 Explain how both the Big Bang and Steady State theories of the origin of the Universe both account for the red-shift of galaxies. 3.22 Explain how the discovery of the CMB radiation led to the Big Bang theory becoming the currently accepted model.

Red Shift-

**Red shift** is a term given to the **change in frequency** of a wave (Visible light in this case) and wavelength due to movement of the source relative to the observer. It is in essence a result of the **Doppler effect**. [|Doppler Effect simulation] For A Big Bang Theory explanation of the Doppler effect, follow the provided link: []

When a wave source moves away from the observer, the frequency is stretched and so becomes **lower in frequency**. As a result of this, the wavelength of the wave increases. This is **red shift**.

When a wave source moves towards the observer, the frequency is squashed and so becomes **higher in frequency**. As a result of this, the wavelength of the wave decreases. This is **blue shift**.

The image on the right taken by the Hubble telescope is of the Hubble deep field, it's is a perfect way of showing an example of **red and blue shift**, the extra solar object that appeares red in the image is actually a far away galaxy moving away from Hubble at great speed, the extra solar object that appeares blue in the image is also a galaxy, but instead it's moving toward the observer.

The **CMB** or cosmic microwave background, was discovered in 1964 by Arno Penzias and Robert Wilson. The **CMB** is thermal radiation filling the observable universe. The Big Bang Theory is supported by the **CMB**, however it disproves the Steady State Theory due to the later stating the universe maintains a constant average density.

The **CMB** supports the Big Bang Theory, because it starts off as Gamma radiation (which is a high frequency) and then transforms into Microwave radiation (with a lower frequency) by getting Red Shifted. This would mean that it has been sent out from a point and is travelling away from that point, so is being viewed by us as something with a lower frequency than it actually is. Also, when discovered, the **CMB** had a temperature close to that predicted for the Big Bang.

11 RED-SHIFT AND CMB

David Littleton and Caleb Gilliam-Scott