Curious Nashville: We Try Rolling Up Warner Park’s 'Gravity Hill' | Nashville Public Radio

Curious Nashville: We Try Rolling Up Warner Park’s 'Gravity Hill'

Aug 12, 2016

Here's an intriguing Curious Nashville question we received from Thais Carr:

Exactly how does "Gravity Hill" in Warner Park work? Many times I went up and backwards in my VW with just one tap on the gas.

If you've lived in Nashville for decades (rather than just years), you may remember when a certain road in Edwin Warner Park — now closed to car traffic — seemed to possess magical powers. 

People called it "Gravity Hill." You could stop your car on it, shift into neutral, let your foot off the brake and then roll uphill. 

At least, it felt that way. 

A quick web search reveals that this phenomenon exists in lots of places around the globe. Some folks call theirs “gravity hill,” like the one in Warner Park. Others are “magnetic hill” or “mystery hill.”

None of these names make sense. Isn’t any hill — where gravity is functioning as expected — a gravity hill? Shouldn’t a hill where the laws of gravity appear reversed be an “anti-gravity” hill? Likewise, “magnetic hill” obscures the actual cause of this phenomenon, and “mystery hill” insinuates that cause is unknown.

This is M.C. Escher's Waterfall. Follow the path of the water with your eyes, and get confused.
Credit Andréia Bohner via Flickr

WPLN’s Natasha Senjanovic once rolled a water bottle up one of these in Italy. She called it an “Escher hill,” after the Dutch artist M.C. Escher. Escher's lithographs play with perspective to create illusory worlds that defy the laws of physics. This hits the nail on the head. That’s exactly what’s going on over in Warner Park.

The first thing to keep in mind is that there is no flat ground anywhere near Gravity Hill — nothing for your eye to use as a basic calibration point.

Look at this photo, taken from below. I was holding the camera as flat as I could, but was probably thrown off by the illusion. 

Credit Mack Linebaugh / WPLN

See how Gravity Hill — going from left to right — appears to veer uphill as it branches away from Old Hickory Boulevard? That's the illusion.

So, after scoping out the scene and snapping some photos, we did some testing.

Who better than WPLN’s ever-impartial political reporter Chas Sisk to help get to the bottom of this. Disclaimer: We are not scientists, but I feel satisfied with what our quick experiment revealed.

Check it out in this video:

Following unsuccessful attempts with a soccer ball and an unmanned tricycle, the video shows what clearly appears to be Chas getting on his bike without pedaling and coasting uphill.

After the ride, we put a carpenter's level on the road in a few places that looked to us like they had an uphill slant. The level showed the opposite. Our eyes were being tricked.

Conclusions: 1) Gravity Hill really works. 2) It's caused by an optical illusion that’s created where the steep angle of Old Hickory meets the gentle slope of the park trail. The two slopes are at such dramatically different grades, they appear to be going in opposite directions when in fact they are not. 3) Gravity Hill needs to be renamed Escher Hill. 

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