Gravity Hill | Hacker News Reader

Gravity Hill

en.wikipedia.org

102 pointsJPLeRouzic33 comments

Legit.

"Roadside America" [1] was my go-to app when road tripping with my daughters years ago. It listed a few "gravity hills" (among many other crazy things). Looking at the list of "Gravity Hills" I believe it was the highway near Ocotillo, California [2].

I saw it coming up on the app. Not expecting much I followed the directions in the info and pulled off the highway at the determined exit. You get to the bottom of the off ramp, stop, and then put the car in neutral.

"Okay", I said, putting it in neutral, "what, am I going to roll backward up the off-ramp? Ha ha.

Oh yes, to my surprise, that is exactly what happened. It very much appeared as though we had come down hill from the off-ramp. Completely surprised me.

[1] Also a web page: https://www.roadsideamerica.com

[2] https://www.roadsideamerica.com/tip/15643

BTW, loved the years when we road-tripped with the kids. Roadside America did make it a lot of fun too. The "Clown Motel", the graveyard behind it, the underground gardens, various Japanese Fire Balloon-related locations, weird "amusement" parks and museums....

The Oregon Vortex is not a gravity hill, but is a related kind of roadside attraction, and even has an impressive pseudoscientific explanation:

http://www.oregonvortex.com/science.htm

I've never been, but my dad did, decades ago, and bought the book, which is how i know about it:

http://www.oregonvortex.com/product-notesanddata.htm

I recommend Kokchi Sugihara's website. https://www.isc.meiji.ac.jp/~kokichis/Welcomee.html

There's a printable gravity hill sculpture among other optical illusions. His back story is that he was working on machine vision for taking in 2d scans of technical drawings and reconstructing the 3d wire frame. Just for the sake of experiment, he fed the program an impossible object and was surprised to find it output some coherent 3d shape. So naturally he built the shape and sure enough, from a specific angle with one eye closed, it looked like the original impossible construction. He's been making impossible constructions ever since.

Thank you for sharing that. People often say that they miss the old internet here, and I think this website is a prime example of that. Someone passionate about something sharing their passion.

I found one of these on a road trip a long time ago. We were heading up the hill to Magazine Mountain in Arkansas in the rain. My old Chevy pickup was struggling as if we were climbing and with all the twists in the road we couldn't go very fast. I was looking out the side window making sure I didn't find the ditch and we could plainly see that the water was flowing uphill from our frame of reference. The engine felt like we were climbing and the water was definitely moving in the apparent uphill direction. I filed that away in my memory as a curiosity. Thanks for the nice explanatory site.

It is possible that the illusion persisted because our horizon was completely blocked by the mixed hardwood forest we were driving through.

The old Chevy was a bit of a clunker. Top speed was just over 55 mph with that worn-out engine although the Missouri State Police with their "speed checked by airplanes" were gracious enough to give me (and a couple others with out of state plates) a ticket for 72 in a 55 as we reached the state police checkpoint just before we left Missouri. The old truck carried us to the beach in Charleston, SC and then back up through the Smokies and across Tennessee to our home in Texas. Cheap trip. When I got home I had just spent my last few dollars on gas and a loaf of bread for our peanut butter. It was a great way to celebrate graduating high school. Good times.

Does anyone else find the example picture unconvincing? It looks more like a very shallow valley to me. Far in the distance it looks like it's rising, but closer to the camera, it looks like it's (admittedly very slightly) downhill.

Sometimes these sort of things aren’t as apparent in a picture compared to actually being there.

I thought the same until I realized that the example picture is attempting to demonstrate the effect using the direction of the flow of the puddle of water in the foreground (the caption reads : Water appearing to run uphill at Magnetic Hill in New Brunswick).

Great places for Nikola to showcase their latest vehicles!

Several impressive gravity hills can be found inside a pub in the UK called The Crooked House. It's so wonky you can feel a little queasy if you stay in there a while!

https://en.wikipedia.org/wiki/The_Crooked_House

I came across one of these once without knowing about the phenomenon. It’s in Golden Gate Park near the intersection of JFK Drive and Transverse Drive. Water in the stream next to the road appears to flow uphill. Very surreal.

I drove half way across my state yesterday to visit a gravity hill after finding it on Roadside America. If seeing this on the front page of HN less than 24 hours later isn't a sign, I don't know what is.

Birthday paradox?

Maybe, but only if observed from the outside - collision of properties from within a sufficiently large sample.

From the point of view of the gp it is a collision of its own property (sample size 1) with properies of something else, of possibly huge sample size (all things discussed online) and not even independend (would gp have read the post and posted without having been there recently?).

Not exactly birthday paradox. This thing needs a different name.

I noticed a huge upsurge in coincidences starting around five years ago. I assume the simulation has depleted its entropy pool.

"List of Gravity Hills": https://en.wikipedia.org/wiki/List_of_gravity_hills

"Gravity/Magnetic Hills Explained": https://youtu.be/-lXAeIJdxDc

That appears to be a pretty comprehensive list but it's missing Northern Michigan's Mystery Spot:

https://www.atlasobscura.com/places/st-ignace-mystery-spot

Went there as a little kid. Most folks touring were a bit scared by it. I viewed it as a magic trick and wanted to figure out how they did it.

Makes sense that our brain has instinctual mechanisms to differentiate between force due to gravity and forces due to something else.

This type of illusion gives us insight into how it works. Obviously it's visually based. Our brain instinctively rationalizes the force as something other than gravity (rolling uphill) if the visual markers don't align.

We tend to think conscious judgement and categorization is part of the executive decision making process of our brain. But this illusion shows that it is not. Categorizing a force as gravity or not gravity is done by a very primitive part of our brain.

What people don't realize that these primitive modules extend beyond physical forces to even morals. What you categorize as good and evil is done instinctively by a primitive part of your brain and suffers from identical counterparts to optical illusions that are a part of the vision module of our brain.

We used to go to one in Sonoma County. I would have thought these were pretty common but apparently it was one of only 6 listed in California on the wikipedia page https://en.wikipedia.org/wiki/List_of_gravity_hills

With regards to the last sentence there, in my experience cycling a "false flat" is simply a very gradual uphill that saps your energy slowly. Not really an optical illusion in the same sense as these gravity hills.

A "gravity hill" is a slope that appears to be sloped the other way, and a "false flat" is a slope that appears to be flat. One example that most people don't realize is the Munich gravel plain (https://en.wikipedia.org/wiki/Munich_gravel_plain) - even though it has the word "plain" in its name, it actually has a very slight gradient going up toward the mountains to the south, because it's formed from gravel eroded from the Alps. Once you are aware of it, you do notice that it takes a little bit less effort to cycle northward rather than southward, and you can also see it if you look at your car's current fuel consumption.

There's one of these outside of Petaluma, CA. Google Map it. I don't want to link to it because the locals are a bit not OK with people hording onto it. It's a small, remote road, but legit.

There is a gravity hill in New Zealand on the road between Wanaka and Queenstown. There is no view of the horizon as described in this article. What makes it even more interesting is there is a stream besides the road that appears to be flowing up hill. My wife and I couldn't understand what was happening for the longest time, but I ultimately put it down to some sort of optical illusion. Interesting to hear there is a name for this phenomenon.

Maybe you could add it to the Wikipedia page? There’s none listed in NZ

There's one of these in one of the cemeteries in my city. We'd go there as teenagers at night, turn the car off, put it in neutral and....

You can get similar fun on long escalators, especially those in tunnels like at metro stations and enhanced when the architectural features are perpendicular to the plane of travel. Suddenly everyone will appear to be leaning wayyyy back or forward and you get a really weird disorienting transition when stepping off the conveyor onto the slanted floor at the end.

This happens to me at the tunnel for the 7 train at Hudson Yards in NYC. EVERY TIME. and it doesn't matter that I've ridden it dozens or possibly hundreds of times.

Tested one of these in New Brunswick [1].

There were lots of bikers testing it out. Good fun, very interesting despite initially thinking that it was a very dull attraction.

[1] https://en.wikipedia.org/wiki/Magnetic_Hill_(Moncton)

> The opposite phenomenon—an uphill road that appears flat—is known in bicycle racing as a "false flat".

This phenomenon is very common here in the Low Countries. These destroy the noob cyclists.

> The opposite phenomenon—an uphill road that appears flat—is known in bicycle racing as a "false flat".

It's funny, as i've got older, i've come across more and more of these.

Funny coincidence to see this suddenly on the front page of HN, as I just heard about this for the first time watching Vampires of Pittsburgh.

For those wondering what Vampires of Pittsburgh is: https://sob.fandom.com/wiki/Vampires_of_Pittsburgh

"Frequency illusion, also known as the Baader–Meinhof phenomenon or frequency bias, is a cognitive bias in which, after noticing something for the first time, there is a tendency to notice it more often, leading someone to believe that it has a high frequency of occurrence" https://en.wikipedia.org/wiki/Frequency_illusion

I'm not saying that it's your case, but it could be :)

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