ben's notesUnits
Distances and Measurements #
How big is 1 Astronomical Unit (AU)?
- 1 AU is the distance from the Earth to the Sun: about 150 million km ($1.5 \times 10^8$ km)
How long does it take for light to travel from the Sun to Earth?
- About 500 seconds, or 8.3 minutes
SI Unit Prefixes #
| k | kilo- | $10^3$ | 1km = 1000m |
|---|---|---|---|
| c | centi- | $10^{-2}$ | 100cm = 1m |
| m | milli- | $10^{-3}$ | 10mm = 1cm |
| M | mega- | $10^6$ | 1Mm = 1000km |
| G | giga- | $10^9$ | 1Gm = 1000Mm |
| $\mu$ | micro- | $10^{-6}$ | 1 $\mu$m = 1000nm |
| n | nano- | $10^{-9}$ | 1000 nm = 1 $\mu$m |