The Universe

What the syllabus asks of you

• Know that the Milky Way is one of many billions of galaxies making up the Universe and that the diameter of the Milky Way is approximately 100 000 light-years
• Describe redshift as an increase in the observed wavelength of electromagnetic radiation emitted from receding stars and galaxies
• Know that the light emitted from distant galaxies appears redshifted in comparison with light emitted on the Earth
• Know that redshift in the light from distant galaxies is evidence that the Universe is expanding and supports the Big Bang Theory
• Know that microwave radiation of a specific frequency is observed at all points in space around us and is known as cosmic microwave background radiation (CMBR)
• Explain that the CMBR was produced shortly after the Universe was formed and that this radiation has been expanded into the microwave region of the electromagnetic spectrum as the Universe expanded
• Know that the speed v at which a galaxy is moving away from the Earth can be found from the change in wavelength of the galaxy’s starlight due to redshift
• Know that the distance d of a far galaxy can be determined using the brightness of a supernova in that galaxy
• Define the Hubble constant H0 as the ratio of the speed at which the galaxy is moving away from the Earth to its distance from the Earth; recall and use the equation H0 = v / d
• Know that the current estimate for H0 is 2.2 × 10–18 per second
• Know that the equation d v = 1 / represents an estimate for the age of the H0 Universe and that this is evidence for the idea that all the matter in the Universe was present at a single point