Gravity Hill…what goes up must come…up?

Rio Scarcelli | Staff Writer



Pennsylvania’s notorious rolling hills and windy roads are a big part of what contributes to a mysterious optical illusion in various parts of the state: gravity hills.

Allegheny County’s largest public park, North Park, is home to one of the state’s three gravity hills. The main sight to see is in an intersection between Kummer and McKinney Roads, which gives the illusion that you are defying the laws of gravity.

Also known as a magnetic hill or a mystery hill, a gravity hill is one a plot of land where the layout produces an optical illusion. It makes a slight downhill slope appear to look uphill. There are hundreds of gravity hills located across the world.

When driving through McKinney Road, a car, person or object will be travelling on a slightly downhill slope. But when a car driving down this road is put in neutral, it gives the perspective that it is actually rolling uphill.

There are certain conditions that allow this illusion to come to life. The first is that the skyline is obscured. Horizons are a way for our eyes to perceive the depth of an area and the slop to which a line is traveling. Without a horizon, a hill that goes downwards may actually appear to not have a slop or even look like it is travelling skyward.

Also playing a factor is the area around the road. Trees or tall natural objects throughout the drive can cause a perpendicular view of the surroundings becomes confused. Trees that lean slightly inwards with no skyline to reference can make a road travelling downhill appear uphill or vice versa.

Finally, the largest addition to the illusion is our own brains.

Many of these anomalies can be observed around the country and are called gravity hills, magnetic hills or mystery spots amidst other names. When exploring these kinds of mind-tricks, an idea is ingrained in our heads that the hill is going to defy gravity.

Without any explanations, the car is set in neutral and rolls downwards on the road. Knowing that the road being travelled is cognitive dissonance, which conflicts with the concept of travelling upwards in your brain.

Prior knowledge in your head creates a sort of placebo effect in your brain. The area is called Gravity Hill, and so it should have the ability to lose gravity. Psychologically, your eyes use this idea as a confirmation bias and compels your brain to see the travel of the object as going upward.

All that is left is to try the experiment for yourself.

Gravity Hill is one of many amazing natural sites to explore in Pittsburgh’s own backyard. You will not believe what kinds of tricks your own eyes can play on you. If your imagination can do it, maybe you too can bend the laws of gravity.