5 ms·

The fun part about this is that gravity has to either be self interacting or capable of propagating faster than light. If gravity wasn't self interacting it wo

The fun part about this is that gravity has to either be self interacting or capable of propagating faster than light. If gravity wasn't self interacting it wouldn't follow the shortest path that gravity itself creates. Light does follow this path. Gravity would move in different directions and at different velocities to light across the universe which is full of gravitational field if it wasn't self interacting. We have seen zero evidence that gravity does propagate differently to light. In fact ligo and other gravity experiments have only confirmed it's the same. So gravity is almost certainly self interacting. What does this mean? Well it wouldn't change much at small scales. There's not enough effect at say planetary scales to really notice. But what happens when you have a field self interacting across vast distances and involving vast galaxy sized masses? Well your link looks at this and yes it matches some of the anomaly's we are at large scale. It's a good theory and I suspect despite being hard to argue against it will face opposition since it means a lot of scientists were chasing a dead end.

deleted 4y ago
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Zamicol 4y ago
In my mind, gravity must self interact due to moving at exactly the same speed as light (and light is affected by gravity). To put this in quantitative terms, the paper "Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A" (https://arxiv.org/abs/1710.05834 https://arxiv.org/abs/1710.05834) constrains the "difference between the speed of gravity and the speed of light to be between −3×10^−15 and +7×10^−16 times the speed of light."
- AnotherGoodName 4y ago
  Yep I feel like ligo and Virgo are the Michelson Morley experiment of this century. They have shown something that is not well accounted for in current theories. Just as MM showed light is always observed travelling at the same velocity Ligo has shown gravity is self interacting. Now we need to change our models and build mathematical frameworks to account for this. It is not acceptable to have a theory that doesn't account for this post Ligo.
  - HardlyCurious 4y ago
    I'm not convinced of that interpretation of MM. MM found a signal below the margin of error. I think if they spun the table faster the signal would grow in strength. But subsequent experiments stopped rotating the assembly at all and just relied on the rotation of earth, and thus had even slower rotation and even smaller signals. But at this point nobody is going to revisit MM, attempting to do so would immediately ruin your scientific reputation.
    - oneshtein 4y ago
      Some of us have no scientific reputation at all, so we are free from the reputation trap.
      - HardlyCurious 4y ago
        I would love to revisit MM myself, but I don't have the expertise to actually setup the experiment. I might be able to resolve that gap, but I definitely don't have the funding either, and that is a gap I don't know how to solve.
    - bigbillheck 4y ago
      > MM found a signal below the margin of error Wiki has their data: https://upload.wikimedia.org/wikipedia/en/thumb/d/d1/Michelson_Morley_1887_Figure_6.png/600px-Michelson_Morley_1887_Figure_6.png https://upload.wikimedia.org/wikipedia/en/thumb/d/d1/Michels... In Michelson's own words (per wiki): > The expected deviation of the interference fringes from the zero should have been 0.40 of a fringe – the maximum displacement was 0.02 and the average much less than 0.01 – and then not in the right place. The data doesn't look anything like a signal, and wiki also says: > Roberts (2006) has pointed out that the primitive data reduction techniques used by Miller and other early experimenters, including Michelson and Morley, were capable of creating apparent periodic signals even when none existed in the actual data. > But subsequent experiments stopped rotating the assembly at all and just relied on the rotation of earth This is also untrue. Per https://arxiv.org/abs/1002.1284 https://arxiv.org/abs/1002.1284 (found via references in wiki): > Our measurement compares the resonance frequencies of two orthogonal optical resonators that are implemented in a single block of fused silica and are rotated continuously on a precision air bearing turntable
- oneshtein 4y ago
  My bet is that difference between gravitational waves and gamma rays due to the effect known as "surfing". A gravitational wave pushes light back from peak, where light is slower, to bottom, where the speed of light is normal again. The difference between gravitational wave and gamma rays is more dependent on initial magnitude of gravitational wave, than on distance traveled.
- jiggawatts 4y ago
  I like this gedankenexperiment: Imagine you're in the vicinity of a supergiant black hole orbited by a close binary pair of neutron stars about to merge with each other. The neutron stars are close enough to the black hole that you see multiple images of them, and the images are highly distorted. E.g.: You can see them even when they're "behind" the black hole due to the highly bent path of the light. You have hundreds of probes scattered over a large volume of space, each equipped with an optical telescope and a gravity wave sensor similar to LIGO. What would you expect to observe? Would the frequency of the final "ringdown" chirp before the merger be observed identically in the optical and gravity sensors? Would they be observed as "coming from" the same spots in the sky? Would you expect to feel a higher contribution to gravity by the neutron stars due to their multiple images? Etc... It's interesting that our intuition about the consistency of the rules related to the speed of causality imply that the answers ought to be: Yes, identical, yes, yes, etc... But that means that gravity is definitely self-interacting, and it also means that gravity can be focused, just like light can be focused by gravitational lensing. This implies that stars at the edge of a galactic disk "see" more gravity from the opposite side of their galaxy due to the lensing effect of the central bulge!
codethief 4y ago
> If gravity wasn't self interacting it wouldn't follow the shortest path that gravity itself creates. I don't know if this is the right way to think about this. Gravity follows all paths. In a sense, it is the path. Or, as Hawking described it[0]: > [Gravity] shapes the arena in which it acts, unlike other fields which act in a fixed spacetime background. Back to your comment: > So gravity is almost certainly self interacting. I'm confused by the "almost certainly". I think this has long been established[1], but for entirely different reasons: The Einstein field equations are highly non-linear, so of course there will be self-interaction. Or, if you prefer to think of the Einstein-Hilbert action: The Lagrangian density L = R · sqrt(det|g|) behaves as L ~ g⁻¹ · Ric · g², and the Ricci tensor is Ric ~ (∂g)∂(g⁻¹) + g⁻¹ ∂²g + (g⁻¹)²(∂g)², so if we view gravity as a quantum field theory (effective or whatever), there are plenty of self-interaction terms that will prevent the N-point function from vanishing for N > 2. Already in the weak field approach (where you approximate g = 1 + h) you get a triple graviton vertex, see p. 21 of https://arxiv.org/abs/1702.00319 https://arxiv.org/abs/1702.00319 . Maybe we are talking about different definitions of "self-interaction here"? [0]: Hawking: The Nature of Space and Time (1994), https://arxiv.org/abs/hep-th/9409195 https://arxiv.org/abs/hep-th/9409195 [1]: See e.g. https://physics.stackexchange.com/questions/293873/do-gravitons-interact-with-each-other https://physics.stackexchange.com/questions/293873/do-gravit...
dilyevsky 4y ago
There are some papers on this subj from Alexandre Deur. Here’s a good explanation - http://dispatchesfromturtleisland.blogspot.com/p/deurs-work-on-gravity-and-related.html?m=1 http://dispatchesfromturtleisland.blogspot.com/p/deurs-work-... It really is a beautiful theory if correct
- jiggawatts 4y ago
  A solved problem doesn’t attract funding for the next financial year, which is why his “too simple” explanation is being systematically ignored.

deleted 4y ago

[deleted]

Zamicol 4y ago

In my mind, gravity must self interact due to moving at exactly the same speed as light (and light is affected by gravity). To put this in quantitative terms, the paper "Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A" (https://arxiv.org/abs/1710.05834 https://arxiv.org/abs/1710.05834) constrains the "difference between the speed of gravity and the speed of light to be between −3×10^−15 and +7×10^−16 times the speed of light."

AnotherGoodName 4y ago
Yep I feel like ligo and Virgo are the Michelson Morley experiment of this century. They have shown something that is not well accounted for in current theories. Just as MM showed light is always observed travelling at the same velocity Ligo has shown gravity is self interacting. Now we need to change our models and build mathematical frameworks to account for this. It is not acceptable to have a theory that doesn't account for this post Ligo.
- HardlyCurious 4y ago
  I'm not convinced of that interpretation of MM. MM found a signal below the margin of error. I think if they spun the table faster the signal would grow in strength. But subsequent experiments stopped rotating the assembly at all and just relied on the rotation of earth, and thus had even slower rotation and even smaller signals. But at this point nobody is going to revisit MM, attempting to do so would immediately ruin your scientific reputation.
  - oneshtein 4y ago
    Some of us have no scientific reputation at all, so we are free from the reputation trap.
    - HardlyCurious 4y ago
      I would love to revisit MM myself, but I don't have the expertise to actually setup the experiment. I might be able to resolve that gap, but I definitely don't have the funding either, and that is a gap I don't know how to solve.
  - bigbillheck 4y ago
    > MM found a signal below the margin of error Wiki has their data: https://upload.wikimedia.org/wikipedia/en/thumb/d/d1/Michelson_Morley_1887_Figure_6.png/600px-Michelson_Morley_1887_Figure_6.png https://upload.wikimedia.org/wikipedia/en/thumb/d/d1/Michels... In Michelson's own words (per wiki): > The expected deviation of the interference fringes from the zero should have been 0.40 of a fringe – the maximum displacement was 0.02 and the average much less than 0.01 – and then not in the right place. The data doesn't look anything like a signal, and wiki also says: > Roberts (2006) has pointed out that the primitive data reduction techniques used by Miller and other early experimenters, including Michelson and Morley, were capable of creating apparent periodic signals even when none existed in the actual data. > But subsequent experiments stopped rotating the assembly at all and just relied on the rotation of earth This is also untrue. Per https://arxiv.org/abs/1002.1284 https://arxiv.org/abs/1002.1284 (found via references in wiki): > Our measurement compares the resonance frequencies of two orthogonal optical resonators that are implemented in a single block of fused silica and are rotated continuously on a precision air bearing turntable
oneshtein 4y ago
My bet is that difference between gravitational waves and gamma rays due to the effect known as "surfing". A gravitational wave pushes light back from peak, where light is slower, to bottom, where the speed of light is normal again. The difference between gravitational wave and gamma rays is more dependent on initial magnitude of gravitational wave, than on distance traveled.
jiggawatts 4y ago
I like this gedankenexperiment: Imagine you're in the vicinity of a supergiant black hole orbited by a close binary pair of neutron stars about to merge with each other. The neutron stars are close enough to the black hole that you see multiple images of them, and the images are highly distorted. E.g.: You can see them even when they're "behind" the black hole due to the highly bent path of the light. You have hundreds of probes scattered over a large volume of space, each equipped with an optical telescope and a gravity wave sensor similar to LIGO. What would you expect to observe? Would the frequency of the final "ringdown" chirp before the merger be observed identically in the optical and gravity sensors? Would they be observed as "coming from" the same spots in the sky? Would you expect to feel a higher contribution to gravity by the neutron stars due to their multiple images? Etc... It's interesting that our intuition about the consistency of the rules related to the speed of causality imply that the answers ought to be: Yes, identical, yes, yes, etc... But that means that gravity is definitely self-interacting, and it also means that gravity can be focused, just like light can be focused by gravitational lensing. This implies that stars at the edge of a galactic disk "see" more gravity from the opposite side of their galaxy due to the lensing effect of the central bulge!

codethief 4y ago

> If gravity wasn't self interacting it wouldn't follow the shortest path that gravity itself creates. I don't know if this is the right way to think about this. Gravity follows all paths. In a sense, it is the path. Or, as Hawking described it[0]: > [Gravity] shapes the arena in which it acts, unlike other fields which act in a fixed spacetime background. Back to your comment: > So gravity is almost certainly self interacting. I'm confused by the "almost certainly". I think this has long been established[1], but for entirely different reasons: The Einstein field equations are highly non-linear, so of course there will be self-interaction. Or, if you prefer to think of the Einstein-Hilbert action: The Lagrangian density L = R · sqrt(det|g|) behaves as L ~ g⁻¹ · Ric · g², and the Ricci tensor is Ric ~ (∂g)∂(g⁻¹) + g⁻¹ ∂²g + (g⁻¹)²(∂g)², so if we view gravity as a quantum field theory (effective or whatever), there are plenty of self-interaction terms that will prevent the N-point function from vanishing for N > 2. Already in the weak field approach (where you approximate g = 1 + h) you get a triple graviton vertex, see p. 21 of https://arxiv.org/abs/1702.00319 https://arxiv.org/abs/1702.00319 . Maybe we are talking about different definitions of "self-interaction here"? [0]: Hawking: The Nature of Space and Time (1994), https://arxiv.org/abs/hep-th/9409195 https://arxiv.org/abs/hep-th/9409195 [1]: See e.g. https://physics.stackexchange.com/questions/293873/do-gravitons-interact-with-each-other https://physics.stackexchange.com/questions/293873/do-gravit...

dilyevsky 4y ago

There are some papers on this subj from Alexandre Deur. Here’s a good explanation - http://dispatchesfromturtleisland.blogspot.com/p/deurs-work-on-gravity-and-related.html?m=1 http://dispatchesfromturtleisland.blogspot.com/p/deurs-work-... It really is a beautiful theory if correct

jiggawatts 4y ago
A solved problem doesn’t attract funding for the next financial year, which is why his “too simple” explanation is being systematically ignored.