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Theoretical physicist Eric Verlinde has finally published his much anticipated article on the nature of gravity. In a 2010 New York Times article Verlinde already stated: gravity is an illusion. His theory goes beyond the concept of gravity as envisioned by both Isaac Newton and Albert Einstein. It will be very interesting to see other scientists sink their teeth into this.
Abstract of his article:
Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional 'dark' gravitational force describing the 'elastic' response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton's constant and the Hubble acceleration scale a0 = cH0, and provide evidence for the fact that this additional 'dark gravity force' explains the observed phenomena in galaxies and clusters currently attributed to dark matter.
Heck, I'm not even going to pretend I grok any of this: I shine shoes for a living and just hope that my understanding of gravity-as-we-know-it is sufficient to catch the coins customers drop into my weary hand.
(Score: 2) by migz on Thursday November 10 2016, @08:16AM
IANAAP
Relativity uses "c", the speed of light as it's "base" unit of measure. If light does change speed then relativity ignores that, since it is using this as a base, the number doesn't change, so the change has to go somewhere else in the equation. This is why space time bends. It might or might not, this is how the model works.
Always remember, the map is not the territory. You can have different types of maps, of different accuracy. Just because a phenomena is on a map, does not mean that it is true in the real world.
As light approaches the sun, it cannot accelerate or decelerate, since by definition c is constant. What happens is spacetime warps.
Of course if you use a different model you could get different results.
Relativity works well, because we can brush a lot of things under the carpet by keeping c constant, and pushing all the wriggly bits into spacetime. Unfortunately you land up with unsatisfactory mismatch with reality which is bodged over with dark matter and dark energy.
Assuming that rather than bending spacetime, we shunt time over to the speed of light side of the equation. In this case we are in very speculative ground. I guess that it would make sense to talk about lighttime accelerating towards the sun leaving the rest in space (including gravity and all the other wriggly bits). In this model space is still bendy, but time is constant on that side of the equation.
What we need from this theory is a testable hypothesis that yields a different result from relativity, that can be tested in the real world. Then we can see who is right. Note more than one model can be "correct". Depending on what you are doing two different maps might be more accurate for what you are doing (e.g. topographical map, vs subway map).