mumbai

Updated: Dec 16, 2016 23:45 IST

What happens to a car left out of gear on a slope? It moves with the force of gravity, right?

Not on this hill in the heart of Mumbai.

Leave a car on this flyover just ahead of the Jogeshwari Vikhroli Link Road (JVLR) near Seepz and it is pulled backward, against the force of gravity.

Called a gravity hill, such mystery spots are found at several places around the world. While most of them are publicised tourist attractions — some even with an entry fee — what lies here on this busy suburban road, which thousands take to work every day, is one of Mumbai’s hidden gems, right under our noses, unexplored, but not unexplained.

So what makes the car roll up the slope of a hill? Do these mystery spots really defy the laws of physics?

To find out, HT set out to see the phenomenon in action. We landed at the spot early in the morning, set up our cameras and asked our driver to let the car take over. He switched to neutral transmission and left the brakes free — not for a moment believing what we said would happen. And then, it did.

The driver changes to neutral transmission to see if the car will actually start rolling upward. ( Pratik Chorge/HT photo )

The car started rolling back up the slope in good speed and we stared with our mouths agape.

What seems like some supernatural occurrence, however, can be explained as a glitch in human perception, scientists said.

“The so called ‘Magnetic Hill’ is a fairly common observation caused by an optical illusion. A car in neutral on a slight downhill slope appears to go uphill and the reason for this illusion is that the layout of the land obstructs the horizon,” explains Dr Lekha Nair, professor at the department of physics, Jamia Millia Islamia, New Delhi.

So it’s nature tricking our brains into believing something?

“Yes. Without a flat horizon, judging the slope of a surface is difficult, as a reliable reference is missing. The alignment of the road with the slope and the background can give the illusion that there is an upward slope, while it is actually downward,” Nair said.

If you are in the mood for a quirky science experiment, one way to prove the slope is actually downhill is to use a long spirit level . Or, use your car’s GPS to prove there’s nothing wrong with gravity. ( Pratik Chorge/HT photo )

So your car looks like it is getting mysteriously dragged ‘up’, but all it is doing is going with the force of gravity.

Another study at the Pennsylvania State University has a similar explanation. It says the illusion is created by the position of trees and slopes around the spot or a curvy horizon line that blend to trick the eye.

If you are in the mood for a quirky science experiment, one way to prove the slope is actually downhill is to use a long spirit level — a sealed glass tube almost completely filled with water. When placed flat on the ground, the side with the bubble will indicate the higher elevation.

“Or, you can also use the GPS in your car to measure altitude to get the true elevation above sea level,” Nair said.