Where things roll uphill....

There are spots in the world where things seem to be rolling uphill. Here's one in California:



For those of us in the UK there's one on the Isle of Man. In fact there are hundreds, worldwide.

So, have we gotten gravity drastically, horribly, wrong?

Possibly*, but this isn't good proof of it. There are a few ways to make something appear to roll uphill. Here's one made out of card - it's all in the angles:



There are other ways - just put 'ball rolling uphill' into Google.

Looking at the 'gravity hills' the same set of circumstances always seem to be present: A gentle slope, and surrounding hills that block the horizon. The human sense of balance isn't great at sensing gentle slopes, and so our brains rely more on our eyes to judge them - and the eyes can be fooled if the horizon isn't visible. You can even measure the road surface as flat at one spot with a spirit level, but the road as a hill can still be gently sloped the wrong way overall - you need to spirit level it all the way along to really tell.

So I'm betting that almost all of these magnetic hills are a simple optical illusion. But I won't say definitely all of them - if the world didn't still have mysteries then it would be pretty boring.....

* Being open to possibility that they've got something very basic drastically, horribly, wrong is actually 95% of what a scientist is meant to do.