“Gravity hills” tend to exist mainly where we lack a solid point of reference or the horizon is obscured in some way, causing us uncertainty in determining the slope.
Gravity hills are strange natural phenomena in the world where the natural laws of physics seem to be working in reverse. There are numerous ‘gravity hills’ located all over the world, meaning you might have passed through one without even noticing. Strange things happen, such as your car moving up a hill, instead of down, when the car is put in neutral. Or, similarly, placing a ball on the hill and watching it travel upward, not downward.
If you want to check one out for yourself, there’s Confusion Hill in California and even Magnetic Hill which can be found in Canada. As one might imagine, these strange locations have inspired myths such as massive magnets hidden in the Earth and even stories of witchcraft, but the truth is actually grounded in science.
This car here can be seen moving backward, up a gravity hill in Ayrshire, Scotland:
This road in Pennsylvania was tested out using a ball by one YouTube user:
Why is this happening? Basically, we’re seeing an optical illusion. An optical illusion is so profound that people often use equipment to fully understand what’s going on.
"The embankment is sloped in a way that gives you the effect that you are going uphill,” says materials physicist Brock Weiss.
"You are, indeed, going downhill, even though your brain gives you the impression that you're going uphill."
Psychologists say that this optical trick that confuses our brains happens because of the landscape and our point of reference. “Gravity hills” tend to exist mainly where we lack a solid point of reference or the horizon is obscured in some way, causing us uncertainty in determining the slope.
"The whole landscape tilts this way, and the road tilts in the same direction, but by a smaller amount, so the relative slope appears to go the [opposite] way,” says Rob Macintosh to the Science Channel.
So, next time you’re driving in an area with a horizon that is hard to see or that is obscured by the land around it, think about how you view the road. If it appears to be moving in the opposite direction as you, you’ll know that you’ve not entered the Twilight Zone, your brain is simply trying to figure out where you are relative to your surroundings. And doing somewhat of a poor job.
The brain is a powerful thing!