Newton’s Bucket Argument

By Johny Jagannath

There is a simpler version of this argument. If you spin around, your arms fly outward. And the reason they fly outward is because of centrifugal forces. If the joints in your arms were rigid, then no amount of rotation or spinning around would cause your arms to fly outward. Therefore one can always tell if you are spinning or if it is the universe that is spinning.
Newton used a bucket and water to show that one can always tell whether a bucket is spinning or not, by looking at the surface of the water in the bucket. The water molecules in a spinning bucket experience centrifugal forces that push them outward.

This is similar to the bulging of the Earth [at the equator owing to the Earth’s rotation]. But in the Newton’s bucket scenario, the walls of the bucket are rigid [and the bottom of the bucket is closed] therefore the water molecules have no choice but to push themselves upward that gives a concave surface to the water in the bucket. Therefore, Newton declared that one can always know whether one is spinning or not, relative to the universe.

Assuming the bucket were large enough one can always sit in it to find out if the bucket is spinning or not. If the bucket were spinning, one would be pinned to the wall of the bucket, owing to the centrifugal forces. If the bucket were spinning sufficiently fast, you would be thrown out of the bucket, if there were nothing there to hold on to in the bucket.

But for some reason, Einstein’s General Relativity [a mathematical equivalent of Newton’s theory of Gravity] ignores centrifugal forces and the physical effect it has on rotating objects, and reduces the Newton’s Bucket Argument to a paradox, where there is none. Wiki sums up the resolution of a non-existent paradox, according to General Relativity in the following manner:
Therefore whether a bucket is spinning can be decided by first transforming the coordinate system so that the metric is flat and uniform throughout the Universe. That the Universe has a coordinate system where the metric on the large scale is flat comes from cosmology and is due to the Universe coming into being from the Big Bang. That is why we measure whether a bucket is spinning or not relative to the 'fixed' stars which follow the cosmological flow.

As you can see, there was no mention of centrifugal forces in the resolution of the so-called-paradox and no mention at all of the physical effects that centrifugal forces have on the water molecules in the bucket. All we see is jargon like flat metric, coordinate system, cosmology, fixed stars, Big Bang and cosmological flow. We will look at the jargon in the following chapters to see how much of it is mechanics and how much of it is ‘action at a distance’.

Einstein's error or misunderstanding of "inertia" (and by extension centrifugal force) can be seen in his 1920 address at the University of Leyden where he said the following about "inertia/centrifugal-force".

"But inertial resistance opposed to relative acceleration (rotation) of distant masses presupposes action at a distance; and as the modern physicist does not believe that he may accept this action at a distance, he comes back once more, if he follows Mach, to the ether, which has to serve as medium for the effects of inertia.
The error in Einstein's claim is that centrifugal-forces produced due to the rotation of a body is a product of, "action at a distance". And this is patently wrong, because, an object cannot be rotated without making a physical contact with it. Therefore, Einstein demonstrates a glaring misunderstanding of basic Newtonian mechanics. Instead of correcting himself, or admitting to an error, Einstein bizarrely went ahead and redefined, "centrifugal force" and therefore, "inertia", as an entity arriving from "distant stars", via his "medium" aka spacetime. Today, "centrifugal force" aka "inertia" is redefined as a "curvature of spacetime". Phew. What a load of nonsense that is.

As we have seen "centrifugal force" and therefore "inertia" is a simple Newtonian concept that is based on a "contact force" and is not a product of "action at a distance". Period!


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