If the Earth didn't have this tilt, we wouldn't have seasonal changes and the length of the day would remain the same year-round. Instead, we have two equinoxes each year - one in March and one in September - when the sun shines directly at the equator and day and night are nearly equal around the world. In the Northern Hemisphere, the Winter Solstice occurs three months after the September equinox, when the North Pole is most tilted toward the Sun, receives the least sunlight each day, and our northern nights are longest. At this time, near the North Pole, the sun may not rise above the horizon for weeks. This is the polar night.
The summer solstice in June in the northern hemisphere is just the opposite, a day tilted toward the sun. Near the Arctic Circle, places like northern Alaska or Norway experience a phenomenon called the "midnight sun," in which the sun never sets at all but instead traces an oval path across the sky without ever setting below the horizon. The further north you go, the higher the sun will be in the sky during this extended day. At the North Pole, as the sun continues to circle, it does not set for six months.
The earth's axis of rotation is not perfect. It has a slight wobble with a period of about 26,000 years. This means that, over the centuries, the dates of solstices and equinoxes shift slightly and then move back again.
Early civilizations noticed the rotation of the Earth around the Sun. Stonehenge - no one is entirely sure who built it or when - coincides perfectly with sunrise on the summer solstice.
Egypt's Great Sphinx (built about 5,000 years ago) also faces the rising sun at the vernal and autumnal equinoxes. Like many cultures, the main god of the ancient Egyptians was the sun god Ra, who was worshiped as the creator of all things.
El Castillo Castle was built nearly 2,000 years ago by the Maya people of Mexico's Yucatan Peninsula. The Mayans were known for having an extremely accurate calendar. El Castillo was built so perfectly that during the spring and autumn equinoxes, the sunlight casts shadows along the steps of the pyramid, giving the illusion of Kukulkan, the "Serpent of Light" sliding down to meet the reptilian head carved into the stone at the base of the steps. This is all pretty accurate considering the Mayans used several different calendars rather than our modern Gregorian calendar - although, technically, one of the Mayan calendars - the "Haab calendar" - does have 365 days.
It’s pretty cool to see the Earth’s time lapse from a geostationary perspective, but it’s also pretty cool to see the Earth’s time lapse from the International Space Station.