Here's why:
* Equinoxes occur when the sun's rays are directly hitting the equator, meaning the day and night are approximately equal in length across the globe.
* The Earth's tilt is the reason for seasons. At an equinox, the Earth's tilt is neither pointed towards nor away from the sun.
* This means the sun's rays are hitting the Earth directly at the equator, making it the only place where the sun is directly overhead.
Let me know if you have any other questions!