The smallest planet in our solar system and nearerst to the Sun, 

Mecury is only slightly larger than the Earth's Moon. From the surface of Mercury, the sun would appear more than three times as large as it does when viewed from Earth, and the sunlight would be as much as seven times bright...

"Technically, what is going on is that the Earth, Sun and all the planets are orbiting around the center of mass of the solar system," writes Cathy Jordan, a Cornell University Ask an Astronomer contributor.

"...

In layman's terms, the equinox happens because the planet earth is not tilted towards the sun while the sun is directly above the equator. This causes the equinox to happen.

So during this time of the year, both hemispheres get the same hours of daylight and night.

On a usual basis,...