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My pet hate on YT are the videos which claim that gravity is caused by GTD!?
In general, it is a bad idea to cite lots of bad videos.Links to a video "promote" it on search engines...
but part of the argument was based on my calculation of agricultural carbon dioxide emissions.
My pet hate on YT are the videos which claim that gravity is caused by GTD!?Gravitational Time Dilation. I dismissed them, as nonsense, until the PBS Space Time's one. "Wot"!?Please have a look and comment upon them.
It's just that around an object like planet earth, most of that curvature is shown in the time component of the metric describing spacetime around the earth and not in the spatial components of the metric.
The sun can't just disappear in General Relativity, the local conservation of energy-momentum ( ∇μTμν = 0 ) will not allow it. As a consequence the Einstein Field Equations cannot sensibly be used - they would just be inconsistent. Hence, there is no way to know if a gravitational wave would emanate from where the sun was previously located or if the entire metric must change throughout all of space instantly. There is no correct answer, the situation is just fundamentally inconsistent with General Relativity.
But we do have instances of small masses evaporating into massless photons, with absolute conservation of energy and momentum, so what happens to the gravitational field of the electron-positron pair?
That's exactly what Prof.Brainy Greene/horn/e said, in his 2011 The Hidden Reality book in a footnote on p34?But what does it really mean? Even at the surface of the Sun, GTD is practically nothing!
Does L continue to accelerate towards where P was?
U may care to check out my reply to Halc in How close are we from building a virtual universe?It may shed some light on your Lagrangian Mechanics - Why is Nature lazy?
So let's consider a universe in which there is only a positronium pair P and a single, neutral lepton L. Clearly the gravitational field of P will attract L which accelerates towards P (it works for apples, and we assume so for all particles). Then P disintegrates into two photons which, in my simple universe, fly off at right angles to the track of L. Does L continue to accelerate towards where P was?