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Topic 7: Astronomy

4 dot points across 4 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How does gravity keep objects in orbit, and how does weight differ between bodies?

Orbits and gravity: how gravity provides the force for circular orbits, why orbital speed sets the orbit radius, and how weight and g differ between the Earth, Moon and other bodies.
A focused answer to Edexcel GCSE Physics 7.1 and 7.5 to 7.7 (separate physics), covering how gravity provides the centripetal force for circular orbits, why changing velocity at constant speed happens, how orbital speed relates to orbit radius, and how weight and gravitational field strength differ between bodies in space.
9 min answer →

What is red-shift, and how does it provide evidence for the Big Bang?

Red-shift and the Big Bang: the change in observed frequency from a moving source, red-shift of distant galaxies, and the Big Bang and Steady State theories with their evidence.
A focused answer to Edexcel GCSE Physics 7.8 to 7.15 (separate physics), covering how a moving source changes observed frequency and wavelength, the red-shift of light from distant galaxies, how red-shift and the cosmic microwave background support the Big Bang theory, and the comparison with the Steady State theory.
10 min answer →

How is a star born, how does it live, and how does it die?

The life cycle of stars: the formation of a star from a nebula, the main sequence, and the different fates of stars depending on their mass.
A focused answer to Edexcel GCSE Physics on the life cycle of stars (separate physics), covering the formation of a star from a nebula, the balance on the main sequence, and the contrasting later stages of stars similar to the Sun and stars much more massive than the Sun.
9 min answer →

What is in our Solar System, and how have ideas about its structure changed?

The Solar System: the Sun, planets, moons, dwarf planets, asteroids and comets, the order of the planets, and how models of the Solar System changed over time.
A focused answer to Edexcel GCSE Physics 7.2 to 7.4 (separate physics), covering the contents of the Solar System (the Sun, eight planets, moons, dwarf planets, asteroids and comets), the order of the planets from the Sun, and how ideas about the structure of the Solar System changed from geocentric to heliocentric.
8 min answer →