[3](a)A satellite orbits Earth at a radius of 7.0 × 10⁶ m, completing one orbit every 5580 s. Calculate its orbital speed.

[3](a)Light from a nearby star takes 4.24 years to reach Earth. Taking the speed of light as 3.0 × 10⁸ m/s, calculate the distance to the star in metres.

[1](a)State how orbital period changes as orbital radius increases, for planets orbiting the Sun.

[3](b)Explain, in terms of gravitational force, why a planet further from the Sun needs a lower orbital speed to maintain a stable orbit.

[3](a)Explain what redshift is, and what it tells astronomers about the motion of distant galaxies.

[2](a)A geostationary satellite orbits at radius 4.2 × 10⁷ m with an orbital period of 86 164 s. Calculate its orbital speed.

[2](a)Light from the Sun takes about 500 s to reach Earth. Taking the speed of light as 3 × 10⁸ m/s, calculate the Earth-Sun distance.

[1](a)State how the orbital speed of a planet compares for planets close to the Sun versus planets far from the Sun.

[2](a)State what is meant by the term 'the Big Bang theory'.

[3](a)Explain why redshift observed in light from distant galaxies supports the Big Bang theory.

[2](a)Explain why a satellite in a low orbit around Earth must travel faster than one in a high orbit to maintain a stable orbit.