I learned about something called
axial precession in astronomy class several years ago, which is the idea that as something rotates along its axis, it will slowly trace out a cone if the weight of the object isn't equally distributed. In the case of Earth, Earth isn't a perfect sphere as many of us may think it is -- it actually bulges out in the middle enough for it to allow this phenomenon to occur. At the time, all I really took from this concept was how fascinating it is for the north axial pole to move 1° every 72 years from where it is now, and complete one full cycle every 26 000 years. However, I never managed to understand how this concept could fit in to my understanding of why ice ages
[1] occur, and why they too follow a specific cyclical occurrence pattern every
x number of years, in unison with 26 000 year precessional cycle. It's really important that you watch the video below, which discusses axial precession in detail; I figure these guys will do a much better job helping you understand and believe in the concept. Make sure you keep watching until after they finish demonstrating the
gyroscope!
Before putting these two concepts together, I always doubted that ice ages ever even occurred -- even with the vast amount of geological evidence. Theories without strong, understandable, and related evidence never works well with me. As axial precession continues, the current tilt of the Earth, which is currently at (23.5°) will gradually change. Consequently, in 26 000 years, the north-American summer (June through September) will become winter, and vice versa for the countries that are currently below the equator. What happens half way through the precessional cycle could cause the next ice age. The current 23.5° axial tilt is what causes the seasons to occur; if there was no tilt, climate would change all across the globe. The spot that would remain consistent would be at the equator. All in all, ice ages are real and inevitable.
[1] An
ice age, or more precisely, a
glacial age, is a period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers.
