The Earth tilts on its axis at an angle of about 23.4 degrees from the perpendicular to its orbital plane. This angle is also known as the Earth's axial tilt or obliquity. The tilt causes the variation in sunlight that leads to the seasons. It slowly oscillates between about 22.1 and 24.5 degrees over a cycle of approximately 41,000 years due to gravitational forces from the Sun, Moon, and other planets.
