What is a light-second?
the time taken for light to travel 3×108 m3 \times 10^8 \text{ m}3×108 m in a vacuum
the time taken for light to travel from the Moon to the Earth
the distance travelled in a vacuum by light in one second
the speed of light in a vacuum
104 exam-style questions on CIE IGCSE Physics 6.2 Stars and the Universe, covering 6.2.1 The Sun as a star, 6.2.2a Galaxies and astronomical distances, 6.2.2b The life cycle of a star, 6.2.3a Galaxies and the scale of the Universe, 6.2.3b Redshift, 6.2.3c The Big Bang Theory and cosmic microwave background radiation, and 6.2.3d The Hubble constant and the age of the Universe. Each one has a worked solution and a mark scheme showing where the marks go.