Sextant Math: How the Stars Give You Your Position
📍 Navigation
Question
How does a sextant give you your position on the ocean?
Latitude from a star's altitude: in the northern hemisphere, Polaris sits almost exactly above the North Pole, so its angle above the horizon is your latitude. Longitude from time: the Earth rotates 360° in 24 hours, so it turns 15° per hour. Measure the time difference between your local noon (when the Sun is highest) and noon at a reference meridian (Greenwich), and multiply by 15° per hour. This is the math behind MCToon's $10,000 sextant challenge.
The math
Latitude ≈ altitude of Polaris (within ~1°). Longitude = (local time − Greenwich time) × 15°/hour. The Earth turns 360° / 24 h = 15°/hour - so a one-hour time difference is 15° of longitude.
Why it matters
This is how ships navigated the oceans for centuries, and it is the exact math behind the $10,000 challenge: fix a position from three star angles using only flat-earth geometry. No submissions since 2022 - the method flat-earthers claim exists does not appear to exist.