Experts weigh in on whether scientific anomaly at work on Gravity Hill near Prosser (w/video)

By Drew Foster, Herald staff writerJune 21, 2009 

PROSSER -- Laws in science, unlike those in society, can't be broken, right?

Right. Actually, ...

About 15 miles north of Prosser -- inside the labyrinth of roads, past where the irrigated fields of grapes, hops, cherries and apples give way to dry-land farms and rolling fields of sagebrush and tall grasses -- sits Gravity Hill.

The concept is simple: Drive to the start line, stop, put your car in neutral, lift your foot off the brake and let nature pull you up Gravity Hill. As the vehicle inches away from the spray-painted line, it picks up speed, eventually coasting up an incline at more than 10 mph. With ease, the slope is crested, revealing an expansive view of the lower Yakima Valley.

But is Gravity Hill a scientific anomaly? A stretch of lonely road that defies one of the most basic laws of physics? A bizarre world where water runs uphill and dogs meow?

Not quite, say a Prosser High School physics teacher and Washington State University professor. Both men -- Mark Sundberg of Prosser and Sukanta Bose, a gravity expert at WSU -- said Gravity Hill is more likely a natural sleight of hand than a physics-defying phenomenon.

"There is such a kind of thing that if a slope looks one way, it's actually the other," Bose explained. "What is really looking up, is actually down."

"I wonder if it's just a perception thing," Sundberg mused.

Neither man has seen Gravity Hill, which is on North Crosby Road, only found after taking a long drive up Gap Road and several detours along other rural streets.

Sundberg plans to make a trip soon, and when he does, he'll bring a level. Bose said he'd use a plumb line.

"It would show you exactly what is up and down," Bose said.

A level placed at Gravity Hill's start line on a recent afternoon showed the area is indeed not level. Instead, the start line is on a slight, but noticeable, downward grade that, presumably, provides a car with momentum as it approaches Gravity Hill. Still, there is a feeling of being pushed uphill.

As evidenced by bumper-shaped lines of talcum powder on the asphalt behind Gravity Hill's start line, some people check to see if ghostly digits lend a helping hand.

"The basic phenomenon would not surprise me at all," Bose said of the feeling of being pushed uphill, not the otherworldly fingerprints.

One aspect of Gravity Hill, however, remains a bit more difficult to explain. Sitting at the start line, cars roll south toward Gravity Hill, utilizing the slight downhill grade. If a driver instead starts on Gravity Hill's steepest downward slope, facing north toward the start line, and puts the car in neutral from a dead stop, the vehicle doesn't budge. It sits suspended, frozen on the hill.

This, of course, must cause Sir Isaac Newton to roll in his grave, right?

"I'm certain he'd say there's got to be something else to it," Sundberg said of Newton. "As far as gravity's concerned, there's not much to argue about."

Without experiencing Gravity Hill himself, Bose couldn't offer a reason for the suspending effect, except to say he stands by his explanation of the area being an optical illusion.

If it weren't an illusion, and Prosser's Gravity Hill actually defied gravity, Bose laughed and said that "would be quite upsetting."

There is the possibility that a large magnetic rock or ore sits beneath Gravity Hill, pulling vehicles uphill and holding them on the downhill slope. Although he acknowledged it's possible, Sundberg said the theory is unlikely because the ore's mass would have to be greater than the vehicle's.

The history of Gravity Hill is about as shrouded as the reason why cars hang on the slope. Folks at the Benton County Historical Museum are unsure of its beginnings, and numerous area farmers deferred comment to other landowners, each one saying someone else could better explain Gravity Hill's history.

Theories and anomalies aside, both Bose and Sundberg said Gravity Hill is an interesting novelty. Bose compared it to the Mystery Spot in Santa Cruz, Calif., which causes tennis balls to roll uphill and people to lean at sharp angles while standing on what looks like flat ground. The Mystery Spot is a calculated optical illusion, where rustic cabins were built on angled earth. The product, like good magic or card shuffling, fools the eye.

"It was funny and fascinating," Bose said, adding that Gravity Hill should be looked at the same way.

Prosser's Gravity Hill was featured in the book Weird Washington, available at many bookstores.

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