What you'll learn
The structure and origin of the Universe.
Key ideas
- The solar system, galaxies and orbits held by gravity.
- Stars powered by fusion; the Big Bang and red-shift.
Exam tips
- Explain how red-shift supports the Big Bang.
- Orbital speed = circumference ÷ time period.
Common mistakes
- Confusing fusion and fission.
- Forgetting gravity provides the orbital force.