… In almost all the movies the snake chases and overtake the girl who is running in a straight line … The snakes move in a wiggly fashion but still they move in a straight ahead … How?
There are 2 basic methods snakes use to move: they push themselves along by moving the “turns” in their body back and forth, called lateral undulation, or they extend their head forward, then pull their tail end up, repeat, known as the “concertina motion.”
They can also sidewind, or use rectilinear motion, sort of an inchworm-like motion.
The sideways motion cancels out, and the net motion is forward.
Imagine if you drew a line between someone’s footprints as they were walking. Each footprint would be somewhat forward, but also off to the side, since we don’t walk with our feet exactly in front of each other. The line would look like a zigzag, but the overall motion of the person would be forward.
Same with snakes, except instead of stepping, they push off from a curve in their body, first on one side, then the other.
It’s a three-dimensional wriggle, and only the outermost part of the curve is in contact with the ground. Also, girls in movies run really slow.
It’s not just the movies: the black mamba can hit 12 MPH (although you’d be hard pressed to get it to actually pursue you).
I think there may be something analogous to “gearing” going on. The snake doesn’t need much propulsive force to move forward at a steady speed, so it doesn’t need very large side-to-side oscillations to achieve that small propulsive force - just enough to overcome sliding friction against the ground (whcih isn’t all that much, because the snake’s body is pretty smooth).
The movies are wrong. While snakes can travel in a straight line, they don’t really chase their prey like that. Most snakes are ambush predators. If they miss their prey on the first lunge, they’re more likely to wait for something easier to come along than to pursue it.
What happens if the girl moves in a wiggly fashion and undulates? Does the snake stop and watch?
If you do any ice skating or roller blading, you’ll already have a sense of what a snake is actually doing. If an ice skater tries to push skates straight back, the skate just slides over the ice with no push forward, so you have to angle the blade out a little and push to the side. This translates to forward movement. The snake’s coils are doing the same sort of push to the side that translates to forward movement. In ice skating, you have to push to the side because there’s so little friction between blades and ice. A snake pushes to the side because it just doesn’t have good leverage straight back. But it’s the same principle at work.
great point … I was watching this deer chased by a lion … it looked like the deer was running in kind of squiggly wiggly way to prevent being caught … I hear elephants can not run like that