Dark Thoughts
Supernova 1987A imaged in X-rays by the XMM-Newton spacecraft. X-rays are produced when the expanding shock wave interacts with surrounding materiel. Astronomers have found many such bubbles around supernova remnants. Though supernovae are expected to have neutron stars at their centres, none has been found for 1987A. Some astronomers speculate that the core has collapsed completely into a Black Hole.
When all the galaxies, including "dark" mass, are weighed the total is only about 30% of the mass necessary to close the Universe. This has fueled more speculation about a "dark energy." Observations of clusters by Alain Blanchard's team indicate that dark matter is 4 times as prevalent as thought, comprise the 95% of mass that is not baryons. But where is it?
Radio astronomers have found entire dark galaxies in the vicinity of the Milky Way and Andromeda. These galaxies are composed entirely of "dark" mass. These have been found because they are relatively nearby. A dwarf spheroidal galaxy called Tucana exists far from any visible galaxy. No astronomer knows how many more dark galaxies are out there.
In this month's SCIENTIFIC AMERICAN astronomers Wallace Tucker, Harvey Tananbaum and Andrew Fabian write about immense Black Holes at the centres of galaxy clusters. These Black Holes create immense bubbles of high-energy particles, like a supernova but 100 million times more powerful! Tananbaum is director of the Chandra X-ray Centre and will be principal investigator of the CONSTELLATION-X spacecraft, assuming "dark energy" doesn't delay the project.
It is comforting to see similiar processes working at a variety of scales. Black Holes have a huge influence on structure, from stars to galaxy clusters. Could they get any bigger? Astronomers Margaret Geller, John Huchra and the Sloan Digital Sky Survey have shown that galaxies are arranged in enormous walls with bubble-shaped voids in between. These could be home to ultra-massive BIG GULP Black Holes. Early in the Universe's history they would have swallowed everything within reach, leaving behind great voids. The missing mass ascribed to "dark energy" could be hidden in those voids.
Big Gulp Black Holes would swallow any radiation and be nearly impossible to detect visually. They could be detected by their immense magnetic fields. Astronomers have found powerful magnetic fields of unknown origin in intergalactic Space. Those fields may be the sign of the Universe's missing mass.
Labels: black holes, dark matter, galaxies
posted by L. Riofrio at 10:05 PM
6 Comments:
Hi Louise,
I agree there is evidence for dark (unidentified) matter, but the claimed precise estimates for the quantity are all highly speculative. Regards galactic rotation curves, Cooperstock and Tieu have explained galactic rotation ‘evidence’ for dark matter as not being due to dark matter, but a GR effect which was not taken into account by the people who originally applied Newtonian dynamics to analyse galactic rotation:
‘One might be inclined to question how this large departure from the Newtonian picture regarding galactic rotation curves could have arisen since the planetary motion problem is also a gravitationally bound system and the deviations there using general relativity are so small. The reason is that the two problems are very different: in the planetary problem, the source of gravity is the sun and the planets are treated as test particles in this field (apart from contributing minor perturbations when necessary). They respond to the field of the sun but they do not contribute to the field. By contrast, in the galaxy problem, the source of the field is the combined rotating mass of all of the freely-gravitating elements themselves that compose the galaxy.’
- http://arxiv.org/abs/astro-ph/0507619, pp. 17-18.
If that is true, and I'm aware of another analysis of the galactic rotation curves which similarly explains them as a calculational issue without large quantities of dark matter, then that's the major source of quantitative observational data on dark matter gone.
Another quantitative argument is the one you have, where you calculate the critical density of the universe using the Friedmann-Walker-Robertson solutions to GR by fitting a solution to cosmology evidence like the Hubble constant and alleged CC, and then compare that critical density to the observed density of visible masses in the universe.
The problem with that is the assumption that Einstein's field equation with fixed constants is a complete description of the effect of gravitation on the big bang.
I've evidence that it isn't a complete description. It is not compatible with all the other better understood forces of the universe, because if gravity can be unified with the other Yang-Mills quantum field theories, the exchange radiation should suffer redshift (energy loss) due to the relativistic recession of masses in the expanding universe.
In addition, it's clear that the only way to make an empirical prediction of the strength of gravity, for instance the gravity constant G, is for gravity to be interdependent (i.e., partly a result of) the big bang.
Yang-Mills exchange radiation will travel between all masses in the universe.
If a mass is receding from you in spacetime and behaving the Hubble recession v = Hr, then in your frame of reference, the mass is accelerating into the past (further from you).
If you could define a universal time by assuming you could see everything in the universe without delays due to the travel time of light, then this might be wrong.
However, in the spacetime which we observe whereby a greater distance means an earlier time, there is an apparent acceleration.
Suppose you see a galaxy cluster of mass M is receding at velocity v at an apparent distance r away from you.
After the small time increment T seconds have passed, the distance will have increased to:
R = r + vT
= r + (Hr)T
= r(1 + HT).
If the Hubble law is to hold, the apparent velocity at the new distance will be:
V = HR = Hr(1 + HT).
Hence the small increment
dv ~ V - v = {Hr(1 + HT)} - {Hr}
= (H^2)rT.
The travel time of the light from the galaxy cluster to your eye will also increase from t = r/c to:
(t + T) = R/c
= {r(1 + HT)}/c
= (r/c) + (rHT/c).
Hence the small increment
dt ~ T.
Now the observable (spacetime) acceleration of the receding galaxy cluster, will be:
a = dv/dt
= {(H^2)rT}/T
= (H^2)r.
This result is the outward acceleration of the universe responsible for the Hubble expansion at any distance r (it is not the alleged acceleration which is claimed to be required to explain the lack of gravitational slowing down of matter receding at extreme redshifts).
Calculating the total outward force, F = ma, where a is acceleration outward and m is matter receding outward, for the normal big bang is then fairly easy. Two problems are encountered but easily solved.
First, the density of the universe is bigger in the earlier spacetimes we see at the greatest distances. This would cause a problem because material density for constant mass should fall by the inverse cube of time as the universe expands. Hence, seeing ever earlier times means that density should rise toward infinity at the greatest distances.
But this problem is solved by the solution to the second problem, which is the problem that an outward force will, by Newton's 3rd empirically confirmed law, be accompanied by an inward reaction force.
The only thing we know of which can be causing an inward force is the gravitational field, specifically the gravity causing exchange radiation. This solves the entire problem!
By Newton's 3rd law, any mass which is accelerating away from you in spacetime will send gravity causing exchange radiation towards you, giving a net force on you unless this is spherically symmetric.
However, if the receding mass is receding too fast (relativistically), then the gauge boson radiation sent towards you is redshifted to a large degree, which means that matter receding at near the velocity of light doesn't exert much force on you: this is another way of saying that the Hubble acceleration effect breaks down when the recession velocity v approaches c, because once something is observably receding from you at near a constant velocity (c) it is no longer accelerating much!
Hence, even if the density of the universe approaches infinity at the earliest times, this doesn't make the effective outward force infinite, because the acceleration term in F = ma is cut. The first problem was that the masses, m, at extreme distances (early times) become large, making F go towards infinity. The solution to the second problem shows that although m tends to become large, the effective value of a falls at the greatest distances because the spacetime recession speed effectively becomes a constant c, so a = dc/dt = 0. Hence the product in F = ma can't become infinite for great distances in spacetime.
There is a straightforward mathematical way to calculate the overall net effect of these phenomena, by offsetting the density increase with redshift from the stretching of the universe.
Now we have the outward force of the big bang recession and the inward reaction force calculated, we can then see how exchange radiation works to cause gravity.
The exact nature of the gauge boson exchange radiation processes are supposed to be gravitons interacting with a mass-giving field of Higgs bosons, and there are physical constraints on what is possible. If you can assume each mass to be like a mirror and the gauge bosons to be like light, a pressure of is exerted each time the gauge bosons are reflected between masses (exchanged). (A light photon has a momentum of p = E/c if it is absorbed, or p = 2E/c if it is reflected.)
Because the universe is spherically symmetric around us, the overall inward pressure from each direction cancels, merely producing spacetime curvature (the gravitational contraction of spacetime radially by the amount (1/3)GM/c^2 = 1.5 mm for planet earth), a squashing effect on radial but not transverse directions (this property of general relativity is completely consistent with a gravity causing Yang-Mills exchange radiation).
What is interesting next is to consider the case of a nearby mass, like the planet earth.
Because all masses in a Yang-Mills quantum gravity will be exchanging gravity causing radiation, you will be exchanging such radiation with planet earth.
However, as already explained, for there to be a net force towards you due to exchange radiation from a particular mass, that mass must be accelerating away from you (the net force of radiation towards you is due to Newton's 3rd law, the rocket effect of action and reaction).
So because the earth isn't significantly accelerating away from you, the net force from the gauge boson radiation you exchange with the masses in the earth (which have small cross-sectional areas) is zero.
So the fundamental particles in the earth shield you, over their small cross-sectional areas, from gauge boson radiation that you would otherwise be exchanging with distant stars (the LeSage shadowing effect).
Gravity results because the tiny amount of shielding due to fundamental particles in the earth, reduces causes an asymmetry in gravity causing gauge boson radiation hitting you, and this asymmetry is gravity.
Besides predicting correctly mechanism for curvature of spacetime due to local gravitational fields in general relativity (the radial contraction can be calculated), this also predicts the correct form of gravity for low velocities and weak fields (Newton's law), which produces a relationship between the density we observe for the universe and the parameters G and H, which is different from the Friedmann-Walker-Robertson metric.
The dynamics of gravity differ from the Friedmann-Walker-Robertson solution to GR due to physical dynamics ignored by GR, namely gravity being (1) a result of the recession (or rather, interdependent on the recession, since the exchange of force causing gauge boson radiation between all masses sheds light on the mechanism for the Hubble law continuing after the real radiation pressure in the universe became trivial), and (2) due to exchange radiation which gets severely redshifted to lower energies in cases where the masses which are exchanging the radiation are receding at relativistic speeds.
You can completely correct GR by setting lambda = 0 and using a calculated value for G which is based on the mechanism. Hence, Einstein's GR is fine as long as you make the gravitational parameter G a vector which depends on various physical dynamics as described in outline above. The details maths for what is above is at http://quantumfieldtheory.org/Proof.htm.
There is some dark matter (no where near as much as the lambda-CDM model suggests) but no cosmological constant or dark energy. The result I get suggests that the Friedmann critical density is higher than the correct formula for the density (from the dynamics above) by the factor (e^3)/2 ~ 10, where e = base of natural logs. This comes from a calculation, obviously, at http://quantumfieldtheory.org/Proof.htm. (When I discussed this result about a year ago on Motl's blog, I think Rivero suggested that it was just numerology. This is the problem where you have a detailed mathematical proof. Where you give it, nobody reads it or will publish it. When you give the results from it, people just assume it has no proof behind it. Whatever you do, there is no interest because the whole approach is too different from orthodoxy, and orthodoxy is respected to the exclusion of science.)
On my old blog, I have an abstract of the theory very briefly at the top:
"The Standard Model is the best-tested physical theory. Forces result from radiation exchange in spacetime. Mass recedes at 0-c in spacetime of 0-15 billion years, so outward force F = m.dv/dt ~ m(c - 0)/(age of universe, t) ~ mcH ~ 10^43 N (H is Hubble parameter). Newton's 3rd law implies equal inward force, carried by exchange radiation, predicting cosmology, accurate general relativity, SM forces and particle masses."
I think the message isn't getting home because people are unwilling to think about velocity of recession being a function of time rather than space! Hence, ever since Hubble discovered it, the recession has been mathematically represented the wrong way (as a recession velocity increasing with distance, instead of as an acceleration). This contravenes spacetime. A nice description of the lack of this in popular culture is given by Professor Carlo Rovelli’s "Quantum Gravity" book, http://www.cpt.univ-mrs.fr/~rovelli/book.pdf :
‘The success of special relativity was rapid, and the theory is today widely empirically supported and universally accepted. Still, I do not think that special relativity has really been fully absorbed yet: the large majority of the cultivated people, as well as a surprising high number of theoretical physicists still believe, deep in the heart, that there is something happening “right now” on Andromeda; that there is a single universal time ticking away the life of the Universe.’ (P. 7 of draft.)
Best wishes,
Nigel
I've now rewritten my brief abstract at the top of my old blog:
The Standard Model is the most tested theory: forces result from radiation exchanges. Masses recede at Hubble speed v = Hr = Hct in spacetime, so there's outward force F = m.dv/dt ~ 10^43 N. Newton's 3rd law implies an inward reaction, carried by exchange radiation, predicting forces, curvature, cosmology and particle masses. Non-receding masses obviously don't cause a reaction force, so they cause asymmetry => gravity.
thank you Louise--and Nigel: facinating discussion here, esp of gravity, Newton->exchange radiation (though I understand only maybe 10% of it!)
Dear Space Advocate:
I am contacting you at the request of Tim Kyger, whom many of you know from many space-related activities. In his "spare" time, Tim is Chairman of the Heinlein Centennial, a commemoration of Robert A. Heinlein's life and influence that will be held on July 6-7-8, 2007, in Kansas City Missouri. There will be exhibits, tours, art, sales, and programming in three principal tracks--general science fiction, academic Heinleinia, and space. A birthday celebration, the Gala, is planned for Saturday, July 7, 2007, Heinlein's 100th birthday. Several guests have already committed to attend, including the head of NASA, Dr. Michael Griffin; astronaut and moon-walker Dr. Buzz Aldrin; the first winner of the $500,000 Heinlein Prize for Accomplishments in Commercial Space Activities, Dr. Peter Diamandis; and (through video link) Heinlein's most illustrious contemporary, Sir Arthur C. Clarke. Details can be found at the Centennial website: www.HeinleinCentennial.com.
It is no exaggeration to say Heinlein was the most influential science fiction author of the mid-20th century, but his influence extends to this day far beyond the literary. I had the fortune to meet him a handful of times. I recall him once saying he had several filing cabinet drawers of letters from the three full generations of his readers who had come of age during his writing career. Though himself childless, these "children of Heinlein" had written to him to say they had become scientists, engineers, and the like because they were influenced by his writing to enter such fields. Heinlein obviously thought being the sui generis of this nucleus of future technologists was his greatest contribution to humanity. He was a fierce advocate and believer that our human species would, inevitably, venture into space. At one time or another, his book "Starship Troopers" has been on the required reading list of all three service academies. In recognition of Heinlein's influence on readers who would later become aerospace engineers and scientists, the NASA Medal for Distinguished Public Service was awarded to him posthumously in 1988. There is a Robert A. Heinlein Chair in Aerospace Engineering at the Naval Academy as well.
Tim has asked me to contact a number of space-related websites to request the following of you:
(1) To encourage your attendance and participation at the Centennial.
(2) Mention the Heinlein Centennial on your website, and link to the Centennial website.
(3) "Virally" mention the Heinlein Centennial to anybody else you might think of or be in contact with.
Thank you so much for your time and consideration. I hope you can participate, and please contact me for further information or questions. I can be reached at kgkato@raytheon.com.
Yours truly,
Keith G. Kato
And all this proves...There is a God. Creator of all things.
Thx 4 bloggin'!
King Tut
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