What caused the earth's ice ages, and why did they occur at such equal time intervals (first once every 41,000 years, then once every 100,000 years)? It's a big debate in Earth Sciences, and seems to be taking a new turn recently.
The two major explanations, if I understand them correctly, are:
-Fluctuations in the sun's energy output, which in a model occur at either 41,000 or 100,000 years intervals (which is compatible with our data of the Ice Ages on earth);
-Changes in the earth's orbit, called Milankovitch cycles. These would only create small temperature changes on earth, but we know several mechanisms which could enhance them and turn small fluctuations into full Ice Ages. Problem: this hypothesis doesn't explain why the regular intervals of Ice Ages suddenly changed a couple million years ago (first a regular 41,000 years, then a regular 100,000 years interval).
The solar fluctuation hypothesis (#1) seems to become stronger, but the problem is that it's hard to observe what happens within the Sun (while changes in the Earth's orbit should be observable).
So what's your take on this debate?