The Yugoslavian meteorologist Milutin Milankovitch is known for coming up with the idea of orbital forcing, also known as Milankovitch cycles. Orbital forcing is a fancy term for certain changes in Earth’s orbit, which are precession, obliquity, and eccentricity.
I’ve written about all three of these before, but here’s a brief overview:
Precession is the motion of Earth’s axis like a spinning top. Imagine the Earth’s day-by-day rotating motion as that of a top. What do tops also do? They wobble.
Although I’ve written about obliquity, I haven’t used the term before. It’s a fancy word for how the tilt of the Earth’s axis doesn’t stay at the same angle. It changes a bit over a very long period of time, ranging between 22° and 24°.
Eccentricity refers to the changing shape of Earth’s orbit. You might know that it’s not a perfect circle—it’s an ellipse, which I’ll talk about in more depth later. What you might not know is that how elliptical it is—that is, how far it is from being a perfect circle—also changes a bit over time.
These motions are all very well established in science today. We know that they each have an effect on Earth’s climate, and together they cause the ice ages. But Milutin Milankovitch, the scientist who first came up with the idea, had a lot going against him.
Although, Ice Age is actually a pretty good example of what happens during a real-life ice age. I haven’t seen enough of the movies to really talk about how accurate they are, but I know there’s a lot of ice.
And a lot of breaking of ice.
These movies take place during a time when much of the northern and southern regions of the Earth were covered in glaciers. The world looked a lot like the satellite image up above. Whether mammoths and smilodons (sabre-toothed cats) actually lived then is another question entirely.
For the record, dinosaurs were definitely not still alive back then. Even deep under the ice. The quote from the third movie basically sums it up:
“I thought those guys were extinct!”
“Then that is one angry fossil…”
Yeah, they were extinct. But fiction can do whatever it wants.
But why do ice ages happen…and why isn’t the world covered in glaciers now?
As a born Californian, I never saw seasons this dramatically until I went to college in Flagstaff, Arizona.
I remember, in my first year here, when I was taking a walk around campus with a few friends. We passed over a riverbed where water was gently trickling along. Green grass and brush lined the banks. The sight absolutely captivated me. I had never seen anything like it, even in the springtime.
Then winter hit in all its blizzarding glory. At night, the temperature dropped below freezing. Snow fell in flurries that contrasted beautifully with the night. By morning, snow banks over a foot high lined the footpaths. To say nothing of the state of my winter jacket!
Summer in Flagstaff is hot. And I mean hot. It’s sweltering. Everyone crowds under the nearest tree. I experienced two days of it during orientation, and I never want to be here in the summer again.
Flagstaff’s autumn isn’t quite like the red and golden season depicted above. It pours. The rain sweeps down from the skies in torrents, soaking you through to the bone within minutes of being outside. Don’t think you’re safe under an umbrella. Better get some waterproof slacks to cover up those jeans, or you’ll be freezing in your classes all day.
I remember learning that my good blogging friend, the Momma, experiences the opposite seasons. When it’s pouring over here, it’s all green and sunny in Australia. When it snows here, she’s getting summer—I only hope it’s not as sweltering as it is in Flagstaff!
But why? Why should Australia have seasons that are opposite those in America?