What is the standard SI unit for distance?

The story behind the answer

Metre is the SI base unit for distance (length). In modern terms, it’s defined by a universal constant: the distance light travels in vacuum in 1/299,792,458 of a second. This ties the unit to the unchanging speed of light, ensuring precise and consistent measurements worldwide.

The other options aren’t SI base units: foot is an imperial unit, fathom is a nautical depth measure (6 feet), and angstrom is a non-SI unit used for atomic scales (1 Å = 10⁻¹⁰ m). Memory tip: “Metric = Metre.” Remember that both “metre” (UK) and “meter” (US) refer to the same SI unit.