Final answer:
If Earth was not tilted on its axis, it would not experience the seasons as we know them. Instead, there would be minimal variation in temperature and day length throughout the year, leading to a more uniform climate globally with decreased seasonality.
Step-by-step explanation:
If Earth was not tilted on its axis, the seasons as we know them would not exist. The familiar cycle of the seasons is a direct result of Earth's 23.5° tilt on its axis. Due to this tilt, during the summer solstice, the Sun is higher in the sky, and its rays strike the Earth more directly, resulting in longer days and more intense sunlight, leading to higher temperatures. Conversely, during the winter solstice, the Sun's rays come in at a sharper angle and the days are shorter, causing cooler temperatures. If Earth's axis were not tilted, day and night would still occur because of the planet's rotation around its axis, but there would be minimal variation in temperature and day length throughout the year, leading to a more uniform climate globally.
The tilt of the Earth's axis, known as obliquity, oscillates between 22.1 and 24.5 degrees over a cycle of approximately 41,000 years, affecting the seasonality of our climate. Higher obliquity increases the contrast between seasons, while lower obliquity leads to milder seasonal changes. Without any tilt, Earth would experience decreased seasonality, meaning that the differences between summer and winter temperatures would be greatly diminished, if not eliminated, resulting in mild weather patterns year-round.