Astronomy › Section A · Science and the universe › Topic A.2
Numbers in astronomy and light travel time
Astronomy deals in numbers far too large and too small for everyday notation. Scientific notation and a few special distance units make them manageable, and the finite speed of light turns every telescope into a way of looking back in time.
In this topic
- Numbers too big to write out
- Scientific notation
- Calculating with powers of ten
- SI units and prefixes
- The astronomical unit
- The light-year and the parsec
- Worked example: how far is a light-year?
- Light takes time to arrive
- Looking out is looking back
- Worked example: talking to Mars and beyond
- Common mistakes to avoid
- Key takeaways
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