FE Meme
Lightbulb Logic: Why Not 24-Hour Sunlight?
#247: If Earth were flat we would see sunlight 24 hours a day; we do not, because the Sun is small and localized like a lightbulb that cannot illuminate an entire wall.
The Meme
Room photo with desk lamp beside a wall; bold Q&A text comparing localized lamp beams to day/night cycles on a flat plane.
Why It Spreads
Everyone has seen a desk lamp brighten only part of a wall, so mapping that onto the Sun makes day/night feel intuitive without a distant fusion sphere. The room photo Q&A implies flat Earth should have 24-hour sunlight unless the Sun is localized like a bulb that cannot light the whole room.
What It Gets Wrong
The room photo with a desk lamp beside a wall asks why a flat Earth would not have 24-hour sunlight, comparing a localized bulb beam to day/night cycles. A desk lamp at ~1 m spreads intensity by inverse square law; the Sun at ~150 million km delivers nearly parallel rays across Earth's ~40075 km equatorial width, producing terminator shadows as the planet rotates at 15°/h. Local lamps cannot reproduce opposite seasons between hemispheres, eclipse shadow geometry, simultaneous polar day and night bands, or Eratosthenes-style noon-angle spreads the bedroom analogy breaks at astronomical scale. TestTheGlobe's A Local Sun Explains Day and Night and TestTheGlobe's Day and Night Simulator walk through the observations and predictions this image skips.
The Debunk
The desk-lamp room photo asks why a flat Earth would not have 24-hour sunlight, comparing a localized bulb beam to day/night cycles. A desk lamp at ~1 m with a finite bulb spreads intensity by inverse square law; the Sun at ~150 million km delivers nearly parallel rays across Earth's ~40075 km equatorial width, producing terminator shadows as the planet rotates at 15°/h.
- A ~1 m lamp cannot illuminate a disk thousands of kilometres wide uniformly; TestTheGlobe's A Local Sun Explains Day and Night details why nearby bulbs fail opposite-season and eclipse tests.
- TestTheGlobe's Day and Night Simulator models rotation and illumination on a sphere versus localized lamp circles on a disk.
- Parallel solar illumination at Earth scale requires astronomical distance, not a room fixture; TestTheGlobe's Sun Rays Prove A Local Sun addresses crepuscular-ray misreads that feed lamp analogies.
- Measured seasonal noon angles swing by tens of degrees with a 23.5° axial tilt; TestTheGlobe's Seasons On A Flat Earth With A Local Sun shows why a circling lamp cannot match those numbers.