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Why is it winter in Canada when Earth is closest to the Sun in January? Picture a tilted plate under a flashlight. Face it toward the beam, and light concentrates. Tip it away, and that light spreads thin. Distance isn’t the main switch.

Earth spins around an imaginary line through its poles: its axis. That line stays tilted in nearly the same direction as Earth circles the Sun. When your half tilts toward the Sun, light hits more directly, like the plate facing the flashlight. Longer days add more warming time.

In January, Australia has summer while Canada has winter, yet both share Earth’s distance from the Sun. One gets stronger light and longer days; the other gets weaker light and shorter days. What actually makes one hemisphere’s summer? Its tilt brings more direct sunlight and longer days.