Detection of nanohertz gravitational waves is very challenging, though, due to their extremely low frequency, where the corresponding period can be as long as several years and wavelengths up to several light-years.
https://phys.org/news/2023-06-scientists-key-evidence-nanohertz-gravitational.html
https://phys.org/news/2023-06-scientists-key-evidence-nanohertz-gravitational.html
From your link, long-term timing observation of millisecond pulsars is the only known method for effectively detecting nanohertz gravitational waves.
These pulsar timing array collaborations have been collecting data for 20 years now: the North American NANOgrav, the European EPTA and the Australian PPTA.
https://en.wikipedia.org/wiki/European_Pulsar_Timing_Array#:~:text=The European Pulsar Timing Array ( EPTA) is,with the specific goal of detecting gravitational waves.
The 40 year old Modified Newtonian Dynamics (MOND) hypothesis may be in for a boost!
MOND claims that our standard gravitational models break down at weak accelerations
Early analysis of data collected by the ESA’s Gaia space telescope has suggested that at acceleration rates lower than 0.1 nanometres per second squared the orbits of stars in a binary system deviate from the predictions of Newton’s law of gravitation and Einstein’s general relativity.
If preliminary results can be confirmed and refined with larger data sets in the future, it may be the end of the road for the dark matter hypotheses!
https://www.independent.co.uk/tech/gravity-evidence-astronomers-newton-b2392494.html
MOND claims that our standard gravitational models break down at weak accelerations
Early analysis of data collected by the ESA’s Gaia space telescope has suggested that at acceleration rates lower than 0.1 nanometres per second squared the orbits of stars in a binary system deviate from the predictions of Newton’s law of gravitation and Einstein’s general relativity.
If preliminary results can be confirmed and refined with larger data sets in the future, it may be the end of the road for the dark matter hypotheses!
https://www.independent.co.uk/tech/gravity-evidence-astronomers-newton-b2392494.html
Finding a flaw in Newton's law is an ever lasting quest.
Could be wrong at very large distances or very small ones, for instance.
Usually a finding makes the news for a short while and we do not hear about it anymore.
Well....How can we follow on this one at very small acceleration ?
Could be wrong at very large distances or very small ones, for instance.
Usually a finding makes the news for a short while and we do not hear about it anymore.
Well....How can we follow on this one at very small acceleration ?
0.1 nanometres per second squared is the gravitational strength at which MoND is theorised to significantly begin departing from Newtonian gravity.
This is equivalent to the change in Earth's gravity brought about by an elevation equal to the width of a fine human hair!
The variant of MoND that is involved in the binary star system analysis is called AQUAL.
https://www.universetoday.com/16274...t enough to match the galactic rotation curve.
The diagrams below show Newtonian gravity vs AQUAL in binary stars.
This is equivalent to the change in Earth's gravity brought about by an elevation equal to the width of a fine human hair!
The variant of MoND that is involved in the binary star system analysis is called AQUAL.
https://www.universetoday.com/16274...t enough to match the galactic rotation curve.
The diagrams below show Newtonian gravity vs AQUAL in binary stars.
Ah yes, MOND versus Dark Matter Theories to explain discrepancies in Newtonian Inverse Square gravity.... an interesting rabbit-hole.
I find a common thread in all this that MOND applies with low gravity accelerations. And approximates to inverse distance not inverse square.
I was reading Eureka 63 this morning, An annual publication of the mathematical students of Cambridge University, and very good it is.
https://archim.org.uk/eureka/archive/
This from Indranil Banik: Galaxies without DarkMatter.
Bit beyond my level, but what he seems to be saying is both theories work. But most interesting is this discrepancy in MOND might be a quantum effect.
The Vacuum Energy (think the Casimir Effect) is on a par with gravity at these low accelerations, so becomes significant. Aha!
I was trying to find a paper co-written by Prof. Ian Stewart, where he suggested that acceleration IS distinguishable from Gravity, because the observer sees a higher CMB temperature, but no luck so far.
https://ianstewartjoat.weebly.com/
I find a common thread in all this that MOND applies with low gravity accelerations. And approximates to inverse distance not inverse square.
I was reading Eureka 63 this morning, An annual publication of the mathematical students of Cambridge University, and very good it is.
https://archim.org.uk/eureka/archive/
This from Indranil Banik: Galaxies without DarkMatter.
Bit beyond my level, but what he seems to be saying is both theories work. But most interesting is this discrepancy in MOND might be a quantum effect.
The Vacuum Energy (think the Casimir Effect) is on a par with gravity at these low accelerations, so becomes significant. Aha!
I was trying to find a paper co-written by Prof. Ian Stewart, where he suggested that acceleration IS distinguishable from Gravity, because the observer sees a higher CMB temperature, but no luck so far.
https://ianstewartjoat.weebly.com/
My understanding is that MOdified Newtonian Dynamics (MOND) cannot explain certain phenomena that Dark Matter can, such as the patterns seen in the cosmic microwave background or the clustering of galaxies, and applies only on the scales of single galaxies.
The Dark Matter Halo appears to be the front runner in the race to explain the anomalous velocities of stars in the outer arms of spiral galaxies.
It may be worth giving an explanation of the problem that both MOND and Dark Matter attempt to solve:
If we look at our solar system, the further out a planet is from the Sun, the slower it goes in its orbit, e.g., the Earth takes a year while Saturn takes 29 years. This is exactly as predicted by Newton's theory of gravity.
You would think the same physics would be true of the stars rotating around our galactic centre, i.e., that the stars further from the centre should move slower than those closer in.
However, according to our measurements, the speed of the stars doesn't change as you move far out from the galactic centre, i.e., the most distant stars at the edge of our galaxy are moving faster than predicted by Newton.
This puts doubt on Newtonian Dynamics. To explain the discrepency, astrophysicists are currently working on two alternative theories. One is MOdified Newtonian Dynamics (MOND), the other is Dark Matter.
The Dark Matter theory is the easier one to grasp. If we postulate that there is invisible matter outside our galaxy which provides an extra gravitational pull, that would explain why the stars at the galactic rim move faster than predicted by Newton.
The Dark Matter Halo appears to be the front runner in the race to explain the anomalous velocities of stars in the outer arms of spiral galaxies.
It may be worth giving an explanation of the problem that both MOND and Dark Matter attempt to solve:
If we look at our solar system, the further out a planet is from the Sun, the slower it goes in its orbit, e.g., the Earth takes a year while Saturn takes 29 years. This is exactly as predicted by Newton's theory of gravity.
You would think the same physics would be true of the stars rotating around our galactic centre, i.e., that the stars further from the centre should move slower than those closer in.
However, according to our measurements, the speed of the stars doesn't change as you move far out from the galactic centre, i.e., the most distant stars at the edge of our galaxy are moving faster than predicted by Newton.
This puts doubt on Newtonian Dynamics. To explain the discrepency, astrophysicists are currently working on two alternative theories. One is MOdified Newtonian Dynamics (MOND), the other is Dark Matter.
The Dark Matter theory is the easier one to grasp. If we postulate that there is invisible matter outside our galaxy which provides an extra gravitational pull, that would explain why the stars at the galactic rim move faster than predicted by Newton.
If the formulas do not describe the motion of the galaxies, then the formulas can also be incorrect. Simply to invent uncritically "dark matter" in addition, in order not to have to approach the formulas, or the illusions, is not a sign for critical science;-)
https://www.eia.gov/energyexplained/electricity/how-electricity-is-generated.php
https://www.eia.gov/energyexplained/electricity/how-electricity-is-generated.php
Although typical stars in the Milky Way galaxy have velocities of hundreds of kilometres per second, they only experience gravitational accelerations in the order 10^-10 metres per second squared. This is equivalent to velocity changes of a few centimetres per second over a decade!
It is the measurements of such accelerations that are providing direct tests of to what extent Newtonian dynamics is applicable on scales of thousands of light-years.
It is the measurements of such accelerations that are providing direct tests of to what extent Newtonian dynamics is applicable on scales of thousands of light-years.
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One thing is or sure, @cumbb, Electric Plasma is not the explanation! 😀
I don't know if you are like me, but I find Special Relativity and Quantum Mechanics easy enough:
https://hepweb.ucsd.edu/ph110b/110b_notes/node54.html
Add E=hv for the massless photon, and add Schroedinger's Equation and I can calculate most things in Physics.
But General Relativity relating to Gravity is quite hard, IMO.
We are a long way from understanding Gravity. I have been trying to visualise it:
This is our current idea of what a charged Majumdar-Papapetrou spacetime Schwarzschild Black Hole would look like if you bumped into one on holiday in China:
I am not sure if I am more worried about falling off the Great Wall of China which seems to have no guard-rails, or being eaten by this Black Hole!
I have not calculated how many solar masses this Black Hole might have, but perhaps you can estimate. 🤔
I don't know if you are like me, but I find Special Relativity and Quantum Mechanics easy enough:
https://hepweb.ucsd.edu/ph110b/110b_notes/node54.html
Add E=hv for the massless photon, and add Schroedinger's Equation and I can calculate most things in Physics.
But General Relativity relating to Gravity is quite hard, IMO.
We are a long way from understanding Gravity. I have been trying to visualise it:
This is our current idea of what a charged Majumdar-Papapetrou spacetime Schwarzschild Black Hole would look like if you bumped into one on holiday in China:
I am not sure if I am more worried about falling off the Great Wall of China which seems to have no guard-rails, or being eaten by this Black Hole!
I have not calculated how many solar masses this Black Hole might have, but perhaps you can estimate. 🤔
I'm particularly interested in the fact that the energy-momentum 4-vector of a particle is the gravitational analogue of electric charge.
It's all down to Einstein merging electric and magnetic fields in his theory of special relativity, but don't ask me to repeat his calculations!
My, Steve, you are digging in deep!
In the absence of more information, I must assume you are talking about the Majumdar-Papapetrou solution for a binary black hole, which looks at the deformation of the geometry of spacetime in and around it caused by its companion.
More simply called the geometry of deformed black holes: https://journals.aps.org/prd/abstract/10.1103/PhysRevD.94.044006
A blackhole of that size would be more massive than Jupiter, nice laugh though. 😀
Millions of people in the US receive supplies from FedEx:
As a mathematician, could I point out the humour between E and x? The forward pointing arrow? You will never see it the same again. Total brilliance, IMO. 🙂
As a mathematician, could I point out the humour between E and x? The forward pointing arrow? You will never see it the same again. Total brilliance, IMO. 🙂
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More on the binary star system analysis that appears to support MOND at low accelerations:
If the stars had perfectly circular orbits around one another, their gravitational acceleration would remain constant. In reality, they have elliptical orbits, meaning that their separation from one another and hence their gravitational acceleration changes.
At the larger separations of "wide binaries" the acceleration becomes extremely small, and it is here that the South Korean analysis reveals discrepancies in the acceleration, with its value being greater than what the models of Newton and Einstein predict.
However, earlier this year, researchers at Scotland's University of St Andrews analysed wide binaries from Gaia in search of MOND’s influence, but found no evidence for it. The Scottish team only considered binary systems where the stars' velocities are accurately known, which they say the South Korean team failed to do, and say there is no MOND signal in local wide binaries.
I've extracted and edited the above information from this source: https://physicsworld.com/a/binary-star-study-favours-modified-gravity-over-dark-matter/
If the stars had perfectly circular orbits around one another, their gravitational acceleration would remain constant. In reality, they have elliptical orbits, meaning that their separation from one another and hence their gravitational acceleration changes.
At the larger separations of "wide binaries" the acceleration becomes extremely small, and it is here that the South Korean analysis reveals discrepancies in the acceleration, with its value being greater than what the models of Newton and Einstein predict.
However, earlier this year, researchers at Scotland's University of St Andrews analysed wide binaries from Gaia in search of MOND’s influence, but found no evidence for it. The Scottish team only considered binary systems where the stars' velocities are accurately known, which they say the South Korean team failed to do, and say there is no MOND signal in local wide binaries.
I've extracted and edited the above information from this source: https://physicsworld.com/a/binary-star-study-favours-modified-gravity-over-dark-matter/
"Since July 2022, the James Webb Space Telescope has delivered stunning news: it's seeing galaxies orders of magnitude brighter in the early universe then what science anticipated. It's an undeniable crossroads for astronomers, cosmologists and physicists—requiring a rewrite of the Standard Model of Cosmology which relies upon the Big Bang, Black Holes, Dark Matter and Dark Energy."
And also here: the observations correspond neither to the illusions nor to the - obviously inaccurate - "mathematics"-) Ergo: non-mathematics;-)
And also here: the observations correspond neither to the illusions nor to the - obviously inaccurate - "mathematics"-) Ergo: non-mathematics;-)
@cumbb, without watching your Thunderbolts/Electric Plasma video, can I guess you and your crank friends have discovered that the Universe is 6,000 years old? 🙄
This is the trouble with Philosophising, when you should be Scientifising!
I have no time for Philosophers:
Descartes, Cogito ergo sum an' all that?
It gets worse with William Blake!
William Blake: "The dark religeons are departed and (et) sweet science reigns"
I went to the Exhibition on the advice of an arty friend. I couldn't get out fast enough! It wasn't telling me anything I didn't already know. 😀
This is the trouble with Philosophising, when you should be Scientifising!
I have no time for Philosophers:
Descartes, Cogito ergo sum an' all that?
It gets worse with William Blake!
William Blake: "The dark religeons are departed and (et) sweet science reigns"
I went to the Exhibition on the advice of an arty friend. I couldn't get out fast enough! It wasn't telling me anything I didn't already know. 😀
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;-)
In this video the current mainstream popular big bang "scientists" have their say, like: "Our theories are obviously not true!"-)
In this video the current mainstream popular big bang "scientists" have their say, like: "Our theories are obviously not true!"-)
