Whitehead's theory of gravitation facts for kids
Alfred North Whitehead, a smart mathematician and philosopher, introduced his idea about gravity in 1922. This idea, called Whitehead's theory of gravitation, was once seen as a possible way to explain gravity, just like general relativity by Albert Einstein. However, after more tests and thinking, scientists now consider Whitehead's theory to be outdated.
How Whitehead's Theory Works
Whitehead developed his theory by looking at how the path of a tiny particle is affected by other particles nearby. He came up with something he called "potential impetus." This idea changed Newton's law of universal gravitation by adding a time delay. This means that gravity's influence doesn't travel instantly; it takes time to reach other objects.
Whitehead's formula used something called the Minkowski metric. This is a mathematical tool that helps figure out which events are connected and how gravity's effects are delayed by distance. This "potential impetus" then helped calculate a physical spacetime metric. The movement of a test particle (a tiny object used to study forces) was then described by a path called a geodesic based on this metric.
Unlike Einstein's theory, Whitehead's theory is "linear." This means if you have two solutions to the theory, you can simply add them together to get another solution. This is a key difference. Because of this, Einstein's and Whitehead's theories would often predict different things when more than two large objects are involved.
Testing the Theory
For many years, Whitehead's theory seemed to work well. It made the same predictions as general relativity for four classic tests in our solar system. These tests include how light bends around massive objects, how the orbit of planets shifts slightly over time (like the perihelion of Mercury), and how gravity can slow down light signals (called Shapiro delay). It also predicted the gravitational red shift, where light loses energy when it moves away from a strong gravitational field.
However, in 1971, a scientist named Clifford Will found a problem. He showed that Whitehead's theory predicted a regular change in local gravity that was much larger than what experiments had observed. This change would be 200 times bigger than what was actually measured.
The famous physics textbook Gravitation by Misner, Thorne, and Wheeler also pointed out a major issue. They stated that Whitehead's theory predicted how ocean tides would ebb and flow over time. This prediction was completely different from what people experience every day with the tides.
Some scientists tried to defend Whitehead's theory. They suggested that different tidal predictions could be made if a more realistic model of our galaxy was used. Others even claimed that the tidal effects used to disprove the theory were not fully proven. However, later studies confirmed Will's original calculations, showing that the theory's predictions for tides were indeed wrong.
In 1989, a changed version of Whitehead's theory was suggested to fix the unobserved tidal effects. But this new version had its own problem: it didn't allow for the existence of black holes. Because of these issues, Whitehead's theory is no longer considered a correct way to describe gravity.
Ideas and Debates
Clifford Will also discussed a feature of Whitehead's theory called "prior geometry." In his view, Whitehead's theory had an interesting characteristic: light waves would travel along paths in the actual spacetime (the space and time we experience). But gravitational waves, according to this theory, would travel along paths in a flat, unchanging background space, like Minkowski spacetime. This means that gravity's influence could be described as waves that are delayed by this background space.
There were also debates about how Whitehead's ideas fit with his own philosophy. Some argued that Will's explanation of the theory didn't match Whitehead's deeper philosophical views about nature. They suggested that if interpreted correctly, Whitehead's theory might actually be another way of looking at general relativity, just with different math. However, other scientists disagreed with this idea.
See also
- Classical theories of gravitation
- Eddington–Finkelstein coordinates
