INTRODUCTION

People tend to think the speed of light is constant, and Einstein said it. It isn't exactly true. Yes, he started with this as a postulate in 1905, but in 1911 he wrote On the Influence of Gravitation on the Propagation of Light, where you can see his ideas evolving as he talks about c = c0 (1 + Φ/c²). Then in 1916 in section 22 of Relativity: The Special and General Theory he explains the limitations of the SR postulate:

"In the second place our result shows that, according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity and to which we have already frequently referred, cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position. Now we might think that as a consequence of this, the special theory of relativity and with it the whole theory of relativity would be laid in the dust. But in reality this is not the case. We can only conclude that the special theory of relativity cannot claim an unlimited domain of validity; its results hold only so long as we are able to disregard the influences of gravitational fields on the phenomena (e.g. of light)".

People see the word "velocity" in the 1920 translation without seeing the context, and without seeing that Einstein wasn't talking about velocity as a vector quantity. He didn't speak English in 1920, it was a popular science book, this was the common usage of velocity, as in high-velocity bullet. What he said wasdie Ausbreitungsgeschwindigkeit des Lichtes mit dem Orte variiert.This translates into the speed of light varies with the locality. He was saying thespeedvaries with position, and so the light curves like a car veers when the near-side wheels encounter mud at the side of the road.

It comes as something as a shock for people to realise Einstein was talking about the variable speed of light. It doesn't fit with the relativity they think they know. And that's the size of it. Relativity today is something different, and people don't know it. People think Einstein told us about curved spacetime, but when you read The Foundation of the General Theory of Relativity it's just not there. Yes, he talks about geometry, but he also talks about the equations of motion, throughspace, because you can'tmovethrough spacetime. It's just where we plot our lines. There's other things that people don't know. They don't know that Einstein was derided by some theoreticians even in 1923. You can see a reference to this on page 53 of Graham Farmelo'sThe Strangest Man:

"At that time, Cunningham and Eddington were streets ahead of the majority of their Cambridge colleagues, who dismissed Einstein's work, ignored it, or denied its significance".

Many people don't know that despite the media accolades and public adulation, Einstein drifted out of the mainstream from 1927 when he fell out with Bohr and others over quantum mechanics. They don't know that General Relativity was a "cottage industry" until the sixties, when the Golden Age of General Relativity kicked in with paradigm shifts that changed it more than people know:

"The Golden Age of General Relativity is the period roughly from 1960 to 1975 during which the study of general relativity, which had previously been regarded as something of a curiosity, entered the mainstream of theoretical physics. During this period, many of the concepts and terms which continue to inspire the imagination of gravitation researchers (and members of the general public) were introduced, including black holes and 'gravitational singularity'. At the same time, in closely related development, the study of physical cosmology entered the mainstream and the Big Bang became well established... A number of simultaneous paradigm shifts characterize the Golden Age of general relativity. First and foremost, the Big Bang became the canonical cosmological model. Other paradigm shifts included a growing appreciation of the: Role of curvature in general relativity; Theoretical importance of the black holes; Importance of geometrical machinery and levels of mathematical structure, especially local versus global spacetime structure; Overall legitimacy of cosmology by the wider physics community".

Nor do they know how in 1949 Einstein and Godel worked out that time is cofounded with motion through space, not with space. It's there in A World without Time: The Forgotten Legacy of Godel and Einstein by Palle Yourgrau. But perhaps the signal most important thing people don't know, is that whilst aether is a taboo word which is most definitely out of the mainstream, Einstein's gave his Leyden address in 1920. And the title is Ether and the theory of relativity. There's Einstein, talking about inhomogeneous space and calling it an aether:

"Mach’s idea finds its full development in the ether of the general theory of relativity. According to this theory the metrical qualities of the continuum of space-time differ in the environment of different points of space-time, and are partly conditioned by the matter existing outside of the territory under consideration. This space-time variability of the reciprocal relations of the standards of space and time, or, perhaps, the recognition of the fact that ‘empty space’ in its physical relation is neither homogeneous nor isotropic, compelling us to describe its state by ten functions (the gravitation potentials gμν), has, I think, finally disposed of the view that space is physically empty".

All in all it adds up to something rather strange. It seems that Einstein's gravity has always been fighting against the mainstream, and still is. When you work it back all the way to the original electrodynamics and m=E/c² and look at what Einstein actually said, the realisation dawns that relativity is the Cinderella of modern physics, and she has some ugly sisters. What follows is a layman's overview of what I consider to be Einstein's gravity. See what you think.