How is the Solar System structured, how do stars live and die, and what does red shift tell us about the universe?
The Solar System and orbits, the life cycle of stars, red shift, and the evidence for the expanding universe and the Big Bang.
A CCEA GCSE Physics answer on the structure of the Solar System and orbits, the life cycles of stars, the meaning of red shift, and how red shift provides evidence for the expanding universe and the Big Bang.
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What this dot point is asking
CCEA wants you to describe the Solar System and orbits, outline the life cycle of stars, explain red shift, and describe how red shift is evidence for the expanding universe and the Big Bang. This is the descriptive space-physics topic.
The answer
The Solar System
Orbits and gravity
The life cycle of stars
Red shift and the expanding universe
Worked example: interpreting red shift
Examples in context
Example 1. GPS and weather satellites. Geostationary satellites stay above the same point on Earth, ideal for communications and continuous weather monitoring, while polar-orbiting satellites scan the whole surface as the Earth turns beneath them.
Example 2. Hubble's observations. Measuring red shifts of many galaxies showed that more distant galaxies recede faster, the key evidence that the universe is expanding and supporting the Big Bang theory.
Try this
Q1. What force keeps a planet in orbit around the Sun? [1 mark]
- Cue. Gravity (acting as the centripetal force).
Q2. State the final stage of a star with a similar mass to the Sun. [1 mark]
- Cue. A white dwarf.
Q3. What does the red shift of distant galaxies tell us about the universe? [2 marks]
- Cue. Galaxies are moving away, so the universe is expanding (supporting the Big Bang).
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA style4 marksDescribe the life cycle of a star with a similar mass to the Sun, from a cloud of gas and dust to its final stage.Show worked answer →
A cloud of gas and dust (a nebula) is pulled together by gravity to form a protostar, which heats up.
When it is hot enough, fusion begins and it becomes a stable main sequence star (like the Sun now).
When its hydrogen runs low it swells into a red giant, then sheds its outer layers and the core becomes a white dwarf, which slowly cools.
Markers reward the sequence: nebula, protostar, main sequence star, red giant, white dwarf.
CCEA style3 marksExplain what is meant by red shift and how it provides evidence that the universe is expanding.Show worked answer →
Red shift is the increase in the observed wavelength of light from distant galaxies, shifting it towards the red end of the spectrum, because the galaxies are moving away from us.
The light from more distant galaxies is red-shifted more, showing that more distant galaxies are moving away faster. This indicates that the whole universe is expanding, which supports the Big Bang model.
Markers reward: red shift as an increase in wavelength because galaxies move away; more distant galaxies more red-shifted (moving faster); supporting an expanding universe and the Big Bang.
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Sources & how we know this
- CCEA GCSE Physics specification — CCEA (2017)