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How Einstein Lost His Bearings, and With Them, General Relativity (quantamagazine.org)
Kevin Hartnett, writing for Quanta magazine: Albert Einstein released his general theory of relativity at the end of 1915. He should have finished it two years earlier. When scholars look at his notebooks from the period, they see the completed equations, minus just a detail or two. "That really should have been the final theory," said John Norton, an Einstein expert and a historian of science at the University of Pittsburgh. But Einstein made a critical last-second error that set him on an odyssey of doubt and discovery -- one that nearly cost him his greatest scientific achievement. The consequences of his decision continue to reverberate in math and physics today.
Here's the error. General relativity was meant to supplant Newtonian gravity. This meant it had to explain all the same physical phenomena Newton's equations could, plus other phenomena that Newton's equations couldn't. Yet in mid-1913, Einstein convinced himself, incorrectly, that his new theory couldn't account for scenarios where the force of gravity was weak -- scenarios that Newtonian gravity handled well. "In retrospect, this is just a bizarre mistake," said Norton. To correct this perceived flaw, Einstein thought he had to abandon what had been one of the central features of his emerging theory. Einstein's field equations -- the equations of general relativity -- describe how the shape of space-time evolves in response to the presence of matter and energy. To describe that evolution, you need to impose on space-time a coordinate system -- like lines of latitude and longitude -- that tells you which points are where. Another interesting read on Quanta: Why Stephen Hawking's Black Hole Puzzle Keeps Puzzling.
Here's the error. General relativity was meant to supplant Newtonian gravity. This meant it had to explain all the same physical phenomena Newton's equations could, plus other phenomena that Newton's equations couldn't. Yet in mid-1913, Einstein convinced himself, incorrectly, that his new theory couldn't account for scenarios where the force of gravity was weak -- scenarios that Newtonian gravity handled well. "In retrospect, this is just a bizarre mistake," said Norton. To correct this perceived flaw, Einstein thought he had to abandon what had been one of the central features of his emerging theory. Einstein's field equations -- the equations of general relativity -- describe how the shape of space-time evolves in response to the presence of matter and energy. To describe that evolution, you need to impose on space-time a coordinate system -- like lines of latitude and longitude -- that tells you which points are where. Another interesting read on Quanta: Why Stephen Hawking's Black Hole Puzzle Keeps Puzzling.
In this era of computers and CPU's and constant distraction, he wouldn't have managed to get to even first realization. The Theory of Relativity was a triumph of abstract thought; this is something that doesn't really happen anymore.
the monumental effort to reconcile general relativity with quantum theory flounders in part because of the difficulty of developing a theory of quantum gravity that has the same general covariance Einstein achieved with his field equations. “In some sense you could argue the reason we don’t have an adequate quantum theory of gravity is we don’t know how to express the solutions to Einstein’s equations in a way that completely removes any kind of coordinate dependence,” said Weatherall.
It sounds like he recognized that there was something he couldn't explain, so he backed off a bit and looked for the explanation rather than charge forward and risk looking foolish.
What actually happens when matter turns to energy and back?
It has never been observed to completion, only buildup of mass on high-speed particles and significant energy release on disassembly of atoms.
What's the difference between energy that is electromagnetic and energy that is motion?
How it interacts with other energies.
Why the difference?
They are essentially different, but also somewhat similar. That's why you are having trouble disconnecting the similarity in names from the difference in meaning.
Can you turn motion energy into photon energy?
There are many means of conversion.
Why not?
False.
Where does the value of C come from?
Observation and calculation.
Why is there a limit at all?
We suspect there is a limit because Maxwell's Equations have an asymptote at that value. We accept that there is a limit because high energy testing shows the predicted behavior.
Why is that limit exceeded by observation?
It hasn't been.
How come there are so many forces?
There are 4.
Why is gravity only an attraction force and others not?
Gravity and the strong nuclear force are attraction, the weak nuclear force is repulsion. Magnetism is directionally attraction.
What is time?
A direction.
Why does inertia and momentum require time?
By definition.
Why don't things happen instantaneuosly?
Things do, and trends don't.
What if they do? How would we perceive that?
You wouldn't. At best, your perception is functional on the order of 10^42 hypothetical distinct moments per AC observation.
What would motion look like in a world where everything happens instantaneously?
Have you been to a rave with a strobe light? Start from there.
In this era of computers and CPU's and constant distraction, he wouldn't have managed to get to even first realization.