The Scales of the Universe
The universe is too big, and atoms are too small, to be measured comfortably in meters or kilograms. We rely on highly specific units.
The Macro: Space
- Astronomical Unit (AU): Based on the average distance between the Earth and the Sun. Used for distances inside solar systems.
- Light-Year: The distance light travels in a vacuum over 365.25 days. Used for distances between stars.
- Parsec: The preferred unit of astronomers. Defined using parallax angles. 1 Parsec is roughly 3.26 Light-Years.
The Micro: Quantum
- Nanometer (nm) & Picometer (pm): Used extensively in semiconductor manufacturing. A TSMC 3nm chip uses lines barely wider than a few atoms.
- Electronvolt (eV): Energy on an atomic level is so minuscule that using Joules results in exponents like $10^{-19}$. Electronvolts provide a clean integer scale for particle masses and photon decay.
- Planck Length / Planck Time: Theoretical absolute limit floors where quantum gravity and relativity break down. Converting natural units into standard ones tests the limits of computer floating-point math.