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Curl's Physics: Jumping

The physics of Curl are so much fun! Rolling and jumping on a sphere is one of my favorite aspects of the game. But how exactly do the physics of Curl differ from the physics of real life? Read on to find out!

A Typical Level in Curl

In Curl, characters move across the surface of Glass Islands. These Islands can be different shapes, but frequently they are simple spheres or balls. The Earth, where we live, is of course a sphere as well. But where gravity on Earth always seems to pull in the same direction (down), in Curl the direction of gravity constantly changes. But if we live on a ball, why don't we experience a gravity that changes direction here on Earth? Actually, we do!

Gravity in Curl

As you move about in Curl it quickly becomes clear that gravity changes. Above a Glass Island gravity pulls you down toward the bottom of the screen. Below an Island, gravity pulls you up. To the left of an Island, gravity pulls you right, etc.

Gravity on Earth

But this is also true on Earth. Imagine, for a moment, that you could fly out far enough into space to see the whole Earth, with the north pole at the top and the south pole at the bottom. A person standing (or swimming*) at the north pole would then be pulled down toward the center of the Earth. But a person standing on Antarctica at the south pole would be pulled up toward the center of the Earth.

The real question is why don't we notice that the direction of gravity changes as we move about on Earth like we do in Curl? The answer is scale. There is a huge difference in the relative scale between us and our Earth and the relative scale between the characters in Curl and their Glass Islands: Where the Glass Islands of Curl are about 10 times the size of a game character, the Earth is about 10 million times bigger than you.

The Earth is very, very big.

The Earth is so big that we can't sense that the direction of gravity changes. Even in our fastest jets it takes many hours to travel around the Earth. By the time we get to the other side of the globe, our bodies have become used to the new direction of gravity and it appears to us that down never changed at all. In Curl, by contrast, you can reach the far side of a Glass Island in a second or so, making the change in the direction of gravity blindingly obvious.

But whether you are playing Curl or living on Earth, gravity always pulls you toward the ground -- in whatever direction that may be.

So, is there any difference, then, between the physics of Curl and that in the real world? Yes, there are several, but each difference is less obvious than the red herring of the changing direction of gravity.

The first real difference between gravity in Curl and gravity in our world is its strength. In the real world gravity is remarkably weak. An object has to be truly enormous before we even notice its gravity. The pull of an everyday object, such as a table or even a building is so small we can't feel it. Only something the size of a planet or moon can tug with enough strength to keep us pinned to its surface. In Curl, by contrast, it is impossible to escape the gravity of even a delicate Glass Island.

The second real difference between the gravity of Curl and that of our world is that the strength of gravity in Curl is constant. In the real world, the strength of the gravitational pull of an object depends on the distance you are from that object. The farther you are from an object the weaker its pull. But in Curl, no matter how far you are from your Glass Island, it will always pull on you with the same force.

Gravity on the Surface of the Earth

But actually, in our every day world, since the Earth is so big, we don't notice that the strength of gravity changes. You would have to travel more than 200 miles straight up from the surface of the Earth (well past the top of the atmosphere) before gravity would get even 10% weaker than it is down here where we live. In every day life, the strength of gravity on Earth acts as if it were constant.

The physics of Curl are so intuitive (and fun) precisely because they are so similar to the physics we actually experience in the real world. The strength of gravity in Curl is constant (just as it (approximately) is on the surface of Earth) but because of the change in scale in Curl, the direction of gravity varies (different from our every day experience, but exactly as it does in the large scale universe).

Happy Curling!

*There are actually very few places on Earth where there is land on exactly opposite sides of the globe. Most of the time, if you dig a hole straight down through the Earth, you come out somewhere in our vast oceans. And there are even fewer such opposing lands where people actually live. But one pair of places this does happen is China and the bottom cone of South America. If you live in Patagonia and dig a tunnel straight through the Earth, you really will come out in China!

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