Q: In the hills south of Rome there is an area which, in the very distant past, was volcanic. On the drive from Rocca di Papa to Albano there is a well-known gentle slope in the road which has an extraordinary property
If you stop your car, put it into neutral and then slowly release the brakes, the car will gradually, but perceptibly roll up the hill. I have observed this phenomenon twice, once as a passenger and once as the driver, both in broad daylight. Is there any physical explanation? (continued)
A: I remember from a university surveying course the case of a water main in the Republic of Ireland, where water was supposed to travel by means of gravity over a long distance. The drop was carefully calculated but very small. When water was introduced to the completed main, the engineers were horrified to see it flow uphill, back towards its source.
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The reason turned out to be a local gravity anomaly which meant that gravity in the region acted not perpendicular to the surface of the geoid, but at a slight angle backwards towards the water source. The very small anomaly was enough to overcome the even smaller gradient on the water main. Therefore the water really did flow uphill. I assume a small pump solved the problem.
A: I have experienced an occasion where a major river appears to run uphill. In the USA, Route 128 leaves Moab, Utah to the east and runs alongside the Colorado river for several miles. At a certain stretch, the river appears distinctly to be flowing uphill 鈥� a highly disorienting impression. The rocks of the canyon in which the river flows are stratified and I suspect that it is the line of their bedding which plays the trick on the eye.
A: I remember seeing a related phenomenon while on holiday in Cornwall in 1978. But rather than a hill you could roll up, this was, apparently, a sloping lake. The gradient appeared quite noticeable, although I did not try unpowered waterskiing on it.
From what I remember, the lake was somewhere near Cape Cornwall, although I have failed to find it again on subsequent visits to the area. Can any locals let me know where it is?
A: It would be impossible to prove or disprove the antigravity phenomenon using a spirit level as described in The Last Word (25 February 1995). If the antigravity effect can act on a motor car, it can probably also act on a few millilitres of fluid containing a bubble, causing the bubble to float downhill instead of uphill. I鈥檓 surprised the Skeptical Inquirer fell for that one.