axial-tilt

Earth's 23.5-degree axial tilt, not its elliptical orbit, is why we have seasons. The tilt means each hemisphere receives more direct sunlight and longer daylight hours for part of the year (summer), then less direct light and shorter days for another part (winter). The two hemispheres always experience opposite seasons simultaneously. Solstices and equinoxes mark the extremes and midpoints of this tilt cycle.

If the Moon vanished overnight, Earth's tides, axial tilt, and life itself would change forever. Here's the science of what happens next.

Earth's 23.5° tilt creates seasons and stabilizes climate. What would happen if it vanished — or flipped to 90°?. Learn the science, key examples, and...

The Moon raises the ocean tides, slows Earth's rotation, and is drifting away at about 3.8 cm per year. Whether it also keeps Earth's tilt stable enough for a mild climate is a live scientific debate, and this article lays out both sides.