(a)
For the correct order:
Sun → planets → Moon → asteroids
The Sun is a star and contains most of the Solar System’s mass. Planets are large bodies orbiting the Sun, while moons are natural satellites orbiting planets and are smaller. Asteroids are minor rocky bodies, generally smaller than moons.
(b)(i)
receding / moving away
Redshift occurs when light waves are stretched, increasing wavelength. This indicates the source is moving away from the observer, analogous to the Doppler effect for sound.
(b)(ii)
(Universe) expanding
If light from all distant galaxies is redshifted, they are all moving away from us. This implies the Universe was once concentrated at a single point and has been expanding since.
(c)(i)
distance travelled by light (in space) in one year
A light-year is a measure of astronomical distance, defined by how far electromagnetic waves travel through vacuum in one Julian year.
(c)(ii)
distances vast OR (planets) too far away
Interstellar distances are immense; even travelling at light speed would take years or centuries. Current technology cannot sustain human life or communication over such durations.
(d)
\(1.5 \times 10^{11} \text{ m}\)
\(3.0 \times 10^8 \times 500\)
Using the wave speed equation \(v = \frac{s}{t}\), rearranged to \(s = v \times t\). Substituting values: \(s = (3.0 \times 10^8 \text{ m/s}) \times 500 \text{ s} = 1.5 \times 10^{11} \text{ m}\).
(b) Redshift is an increase in the observed wavelength of the light emitted from distant galaxies.