This article explains how ‘cosmic gravity’ is about 1% weaker than galactic gravity and is causing serious problems with Einstein’s GR
https://www.livescience.com/physics...rite-the-rules-of-the-universe-study-suggests
https://www.livescience.com/physics...rite-the-rules-of-the-universe-study-suggests
I read the above article about the "cosmic glitch" the other night, but it gave no indication of what the required "fix" to general relativity is.
Elsewhere I read that the "fix" is an alteration to the value of the gravitational constant and would be applied as calculations approach the "superhorizon" - the maximum distance light could have traveled since the origin of the universe.
P.S. A 'glitch' in the gravitational constant is mentioned in the original research paper: https://iopscience.iop.org/article/10.1088/1475-7516/2024/03/045
It appears that the 'fix' is up for further exploration as its application is at the expense of spoiling fits to "the baryonic acoustic oscillation scale" in galaxy surveys!
Elsewhere I read that the "fix" is an alteration to the value of the gravitational constant and would be applied as calculations approach the "superhorizon" - the maximum distance light could have traveled since the origin of the universe.
P.S. A 'glitch' in the gravitational constant is mentioned in the original research paper: https://iopscience.iop.org/article/10.1088/1475-7516/2024/03/045
It appears that the 'fix' is up for further exploration as its application is at the expense of spoiling fits to "the baryonic acoustic oscillation scale" in galaxy surveys!
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Really, @Bonsai, I must call you out for excessive use of Acronyms. @Galu obviously shares my disquiet.
What on Earth is TD? I noted earlier that you also use TP, which seems vague too.
And your latest horror in your most recent post. DE and DM?
This sort of stuff just muddies the waters. Imagine my disgust in sitting through 15 minutes of Matt O'Dowd's video on DFT (the familiar Discrete Fourier Transform, or so I hoped) and Schrodinger's equation, only to discover it was about some incomprehensible nonsense called "Density Functional Theory". Many disappointed YouTubers made the same mistake, and said they followed about 5% of it, rather than the usual 20% for Matt O'Dowd Space Time videos.
Feeling the need to address @Galu mentioning Prof. Saul Perimutter, Dr. Sheldon Lee Cooper was highly critical of him:
https://en.wikipedia.org/wiki/Saul_Perlmutter#Popular_culture
I always find it moving to rewatch Sheldon and Amy's moving acceptance speech for the Physics Nobel Prize for discovering Super-Asymmetry:
Back on topic, I always find these Gravity modification theories irritating. A bit of curve-fitting may have worked for Max Planck in Black Body Radiation, but to try and prove Einstein wrong reeks of stupidity.
In fact, I think the whole Galaxy Rotation Rate problem might be explained by Relativistic frame-dragging rather than Dark Matter:
See, the rotating Galaxy can speed us up on the periphery...
https://profoundphysics.com/black-hole-orbits/
Happy with that.
Best from Steve in Portsmouth, United Kingdom, and not an unexplained acronym in sight to boot.
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Back on topic, I always find these Gravity modification theories irritating. A bit of curve-fitting may have worked for Max Planck in Black Body Radiation, but to try and prove Einstein wrong reeks of stupidity.
A rational explanation that moves Einstein’s GR forward will emerge. Agree there seems to be much ‘curve fitting’ going on.
The difference in expected galaxy peripheral orbital velocity, reference the inner velocity peak predicted by Newtonian mechanics, is 2x. In the case of a typical exemplar, the inner orbital peak is c. 100 km/s, and the measured peripheral velocity is a similar figure, when it should be half that. No way TD or frame dragging could account for that - the gravitational potential energy (aka field strength) is just far too low. Per my earlier post, the TD difference is 9.5 us when, if it could explain the anomaly, would have to be of the order of 0.5 seconds. You only get that TD at 50 LY from the centre, assuming a (highly improbable) point mass model.
There is a further complication however. What if we considered the minute accelerative force arising from frame dragging at the periphery over a typical galaxy age of 7-10 billion yrs, surely that might account for the anomaly? The problem with that is it still leaves you with matter at the periphery moving faster than the galaxies eascape velocit.
Thr search continues . . .
NB TO = theoretical physics or theoretical physicists should reap TP = theoretical . . . [typing without specs again]
A rational explanation that moves Einstein’s GR forward will emerge. Agree there seems to be much ‘curve fitting’ going on.
The difference in expected galaxy peripheral orbital velocity, reference the inner velocity peak predicted by Newtonian mechanics, is 2x. In the case of a typical exemplar, the inner orbital peak is c. 100 km/s, and the measured peripheral velocity is a similar figure, when it should be half that. No way TD or frame dragging could account for that - the gravitational potential energy (aka field strength) is just far too low. Per my earlier post, the TD difference is 9.5 us when, if it could explain the anomaly, would have to be of the order of 0.5 seconds. You only get that TD at 50 LY from the centre, assuming a (highly improbable) point mass model.
There is a further complication however. What if we considered the minute accelerative force arising from frame dragging at the periphery over a typical galaxy age of 7-10 billion yrs, surely that might account for the anomaly? The problem with that is it still leaves you with matter at the periphery moving faster than the galaxies eascape velocit.
Thr search continues . . .
NB TO = theoretical physics or theoretical physicists should reap TP = theoretical . . . [typing without specs again]
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The system is up late for the Big Fight! Who'd have thought Usyk would win against the big fella?
Yes, Andrew, my frame-draggng idea might have some problems. And the maths is beyond me. But it's a reasonable long-shot... as good as anything.
Nightly duty done on Nova hunting too, all quiet at the moment:
Did I tell you my nephew's Nikon f1.8 35 and 50mm lenses were THE WRONG ONES for small format DX models? He has the FX lenses, which is wrong for his DX camera, though they work after a fashion.
They came out as f3.5 and 50 and 80mm respectively! No better than my 18-55mm f3.5-5.6 zoom. But I have found a f1.8 35mm DX lens in my local CeX store for £85. Very tempting.
Night all.
Best, Steve.
Yes, Andrew, my frame-draggng idea might have some problems. And the maths is beyond me. But it's a reasonable long-shot... as good as anything.
Nightly duty done on Nova hunting too, all quiet at the moment:
Did I tell you my nephew's Nikon f1.8 35 and 50mm lenses were THE WRONG ONES for small format DX models? He has the FX lenses, which is wrong for his DX camera, though they work after a fashion.
They came out as f3.5 and 50 and 80mm respectively! No better than my 18-55mm f3.5-5.6 zoom. But I have found a f1.8 35mm DX lens in my local CeX store for £85. Very tempting.
Night all.
Best, Steve.
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To set the scene for the casual reader, there is a discrepancy between the observed rotation of galaxies and their rotation as predicted by Newtonian gravitation.
The discrepancy can be illustrated by a galaxy rotation curve:
Above, the orbital velocities of stars are plotted against their radial distances from the galactic centre.
The white line shows the observed rotation rates, while the red line show those predicted by Newtonian gravity.
I believe the white line is known as a flat rotation curve.
Armed with this information, I will now attempt to get my head round your (Bonsai's) post, which I currently find rather impenetrable!
Nikon FX lenses are designed for use with Nikon’s full-frame DSLRs.
If you use a full-frame lens on an APS-C sensor camera you get a narrower angle of view than with a larger sensor.
Most APS-C cameras have a crop factor of 1.5 when, for example, a 50 mm lens is cropped to a 75 mm lens.
I had to find out about this when I wanted to use lenses designed for my Pentax 35 mm film SLR on my Pentax APS-C digital SLR, and have just refreshed my memory courtesy of this site: https://www.phototraces.com/b/full-frame-lens-on-aps-c-vs-aps-c-lens-on-full-frame/
Re you post on glaxy rotation speeds Galu.
The inner peak is that hump you see on the left up to where both the Newtonian predicted velocities agree. Beyond that, to the right, they diverge and you get the flat upper curve that has mystified cosmologists.
On the frame dragging thing, I just took a stab that it may provide some small accelerative force - probably not though.
The inner peak is that hump you see on the left up to where both the Newtonian predicted velocities agree. Beyond that, to the right, they diverge and you get the flat upper curve that has mystified cosmologists.
On the frame dragging thing, I just took a stab that it may provide some small accelerative force - probably not though.
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