We have seasons on Earth because Earth's axis is tilted about 23.4 degrees relative to its orbital plane around the Sun. This tilt means that as Earth orbits the Sun throughout the year, different parts of Earth receive varying amounts of sunlight and solar intensity. When one hemisphere is tilted toward the Sun, it experiences summer with more direct sunlight and longer days; when tilted away, that hemisphere experiences winter with less direct sunlight and shorter days. This axial tilt and Earth's consistent axial direction as it orbits cause the cyclical seasonal changes.