Final answer:
The Earth's tilt at 23.5 degrees is crucial for seasonal changes, as it causes the Sun's rays to hit the planet at varying angles throughout the year. Without it, there would be little to no seasonal variation. Changes in Earth's obliquity affect the severity of seasons.
Step-by-step explanation:
The statement If the Earth was not tilted on its axis by 23.5 degrees, there would be no seasons whatsoever is largely true. The tilt of the Earth's axis is critical for the shifting of seasons that we experience. The Earth's axis is currently tilted at approximately 23.5 degrees, which causes the Sun's rays to strike different parts of the planet more directly at different times of the year, leading to seasons. Without this tilt, we would not have significant seasonal variations. If the Earth's axis were not tilted, the Sun would always be positioned at the equator, leading to minimal variation in day length and sunlight throughout the year.
Earth's axial tilt has a cycle known as obliquity, which ranges from about 22.1 to 24.5 degrees and takes roughly 41,000 years to complete. Changes in Earth's obliquity can affect the extremity of seasons, with a higher angle increasing the difference between summer and winter temperatures, resulting in hotter summers and colder winters. A lower angle would lead to milder seasons.
Considering other planets, their seasons are also a result of their axial tilt. Planets with a tilt similar to Earth's would likely have similar seasonal cycles, while those with little to no tilt might not experience significant seasons. The inclination of a planet's axial tilt from the normal to its orbital plane creates the variety in the seasons.