📐 What if Earth had no axial tilt?
No seasons. Ever. The equator bakes, the poles freeze, permanently.
The science
Seasons exist because Earth's axis tilts 23.4° toward or away from the Sun during the year. With zero tilt, every day would be like an equinox: 12 hours of light everywhere, the equator always hot, poles always in twilight cold.
Immediate consequences (modelled)
Seasons vanish; day length becomes 12 hours worldwide, year-round.
Possible long-term consequences (hypotheses)
Polar ice caps would likely grow; the habitable band could narrow toward mid-latitudes.
Assumptions: All else (orbit, atmosphere) unchanged.
Limitations: Does not model climate, geology, biology or engineering in full detail.
Reference: NASA / peer-reviewed planetary science