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Dark Matter Measurements
ksp0704 writes: "According to this article at space.com, scientists have finally measured the approximately 90% of the universe we can't see (the dark matter)." I'm sure it will continue to be a topic of debate for years, but two independent measurements agreeing is a good sign.
Figuring that Excite got /.'ed here:
"Astronomers Celebrate Reliable Measure of Dark Matter
By Heather Sparks
Staff Writer
posted: 12:48 pm ET
29 October 2001
Scientists are closer than ever to balancing the
checkbook of cosmic matter. This is because two recent independent measurements of normal matter in the universe are in agreement. The results further strengthen the case for the Big Bang theory and for the nature of the universe as astronomers understand it today.
The universe contains normal atomic matter, what makes you, your dog, the stars, and everything in between. Normal matter is what Carl Sagan was talking about when he said we are all star-stuff.
But in addition to star-stuff, there is invisible dark matter that is known only because the universe is denser than normal matter alone, as evidenced by how structures, like clusters of galaxies, are bound together by gravity. Even individual galaxies don't have enough normal matter in them -- that which can be directly detected -- to keep them from simply flying apart.
Now, through different measurements of conditions existing at the very start of time, astronomers are beginning to see the light.
"There is more than one way of measuring the total amount of matter in the universe," said astronomer Brian Fields from the Center for Theoretical Astrophysics at the University of Illinois, Urbana-Champaign. "And if you have an idea of how much normal stuff there is to all the universe, then you know how much other stuff there is, too." Creation of normal matter
All the "normal stuff" is thought to have been made in two steps, one occurring when the universe was roughly three minutes old, and the other some 300,000 years later.
According to the leading theory, an enormous nuclear explosion called the Big Bang happened 13 billion to 15 billion years ago. From it, the universe appeared in an instant, but as a billion-degree mess of neutrons, protons and electrons. The explosion was so energetic that nothing could come together close enough, for long enough, to form atoms. But the universe expanded and cooled so rapidly that within three minutes protons and neutrons bonded in twos and fours, and formed all the atomic nuclei in the universe. This Big Bang Nucleosynthesis determined how much normal matter would ever exist.
Just how much matter that was can be estimated from observing the most recently formed stars and galaxies, because they are fueled by the hydrogen atoms formed from those original nuclei of twos.
Fields explained that young stars, like our Sun, are just now fusing that original hydrogen into helium whereas older stars fuse helium into oxygen and iron. Because the hydrogen fuel has not been converted, scientists are able to measure the proportion of original normal matter to dark matter.
"Stars change the amount of hydrogen and helium in the universe," he said, "and we want to know what the Big Bang did. So we have to find places where pollution from stars is minimal" to estimate the original amounts of normal and dark matter.
But before any stars could form, hydrogen atoms had to exist. This took 300,000 years after the Big Bang Nucleosynthesis the universe had to cool down enough so that electrons could bind with the nuclei.
Once this happened, there was a curious side effect: the creation of light in the Universe. Unbound electrons scattered the UV radiation from the Big Bang, but once the electrons were bound, the radiation was allowed uniform movement, thus, light was finally released in the young cosmos.
This light has existed since then, travelling along the edge of the universe, stretching and weakening into a still measurable microwave radiation, called the Cosmic Microwave Background, or CMB as astronomers call it.
Weak attraction
At the time of the original release of light, dark matter had congregated in clumps, which created small fields of gravity that eventually pulled in normal matter as well. Images of the CMB are therefore mostly smooth, but have spots, or wiggles, of slight variation, a result of the dark and normal matter pooling together.
"The nature of these 'wiggles' is basically saying how the normal matter was responding to that crazy dark matter," explained Fields, "by amplifying the places where the extra density was."
The CMB, most recently measured by highly sensitive probes in Antarctica, therefore gives a detailed measure of the proportion of normal to dark matter.
Phenomenally, both the measurements of young galaxies and of the cosmic microwave background showed that normal matter makes up just one-tenth of the universe. The rest must be dark matter, researchers say. Fields, who wrote about this astronomical agreement in the Oct. 19 issue of the journal Science, explained why this is causing astronomers to "bring out the bubbly."
"It didn't have to be true," Fields explained, "because they're completely independent things. It's just gorgeous that they agree with each other."
Earlier studies had showed that dark matter made up anywhere from 85 to 95 percent of the universe. Only now do the two different measures of dark matter agree. Now, 90 percent of everything is known to be virtually nothing."
forget it.
Astronomers Celebrate Reliable Measure of Dark Matter
By Heather Sparks
Scientists are closer than ever to balancing the checkbook of cosmic matter. This is because two recent independent measurements of normal matter in the universe are in agreement. The results further strengthen the case for the Big Bang theory and for the nature of the universe as astronomers understand it today.
The universe contains normal atomic matter, what makes you, your dog, the stars, and everything in between. Normal matter is what Carl Sagan was talking about when he said we are all star-stuff.
But in addition to star-stuff, there is invisible dark matter that is known only because the universe is denser than normal matter alone, as evidenced by how structures, like clusters of galaxies, are bound together by gravity. Even individual galaxies don't have enough normal matter in them -- that which can be directly detected -- to keep them from simply flying apart.
Now, through different measurements of conditions existing at the very start of time, astronomers are beginning to see the light.
"There is more than one way of measuring the total amount of matter in the universe," said astronomer Brian Fields from the Center for Theoretical Astrophysics at the University of Illinois, Urbana-Champaign. "And if you have an idea of how much normal stuff there is to all the universe, then you know how much other stuff there is, too."
Creation of normal matter
All the "normal stuff" is thought to have been made in two steps, one occurring when the universe was roughly three minutes old, and the other some 300,000 years later.
According to the leading theory, an enormous nuclear explosion called the Big Bang happened 13 billion to 15 billion years ago. From it, the universe appeared in an instant, but as a billion-degree mess of neutrons, protons and electrons. The explosion was so energetic that nothing could come together close enough, for long enough, to form atoms. But the universe expanded and cooled so rapidly that within three minutes protons and neutrons bonded in twos and fours, and formed all the atomic nuclei in the universe. This Big Bang Nucleosynthesis determined how much normal matter would ever exist.
Just how much matter that was can be estimated from observing the most recently formed stars and galaxies, because they are fueled by the hydrogen atoms formed from those original nuclei of twos.
Fields explained that young stars, like our Sun, are just now fusing that original hydrogen into helium whereas older stars fuse helium into oxygen and iron. Because the hydrogen fuel has not been converted, scientists are able to measure the proportion of original normal matter to dark matter.
"Stars change the amount of hydrogen and helium in the universe," he said, "and we want to know what the Big Bang did. So we have to find places where pollution from stars is minimal" to estimate the original amounts of normal and dark matter.
But before any stars could form, hydrogen atoms had to exist. This took 300,000 years after the Big Bang Nucleosynthesis the universe had to cool down enough so that electrons could bind with the nuclei.
Once this happened, there was a curious side effect: the creation of light in the Universe. Unbound electrons scattered the UV radiation from the Big Bang, but once the electrons were bound, the radiation was allowed uniform movement, thus, light was finally released in the young cosmos.
This light has existed since then, travelling along the edge of the universe, stretching and weakening into a still measurable microwave radiation, called the Cosmic Microwave Background, or CMB as astronomers call it.
Weak attraction
At the time of the original release of light, dark matter had congregated in clumps, which created small fields of gravity that eventually pulled in normal matter as well. Images of the CMB are therefore mostly smooth, but have spots, or wiggles, of slight variation, a result of the dark and normal matter pooling together.
"The nature of these 'wiggles' is basically saying how the normal matter was responding to that crazy dark matter," explained Fields, "by amplifying the places where the extra density was."
The CMB, most recently measured by highly sensitive probes in Antarctica, therefore gives a detailed measure of the proportion of normal to dark matter.
Phenomenally, both the measurements of young galaxies and of the cosmic microwave background showed that normal matter makes up just one-tenth of the universe. The rest must be dark matter, researchers say. Fields, who wrote about this astronomical agreement in the Oct. 19 issue of the journal Science, explained why this is causing astronomers to "bring out the bubbly."
"It didn't have to be true," Fields explained, "because they're completely independent things. It's just gorgeous that they agree with each other."
Earlier studies had showed that dark matter made up anywhere from 85 to 95 percent of the universe. Only now do the two different measures of dark matter agree. Now, 90 percent of everything is known to be virtually nothing.
"If he thinks he can hide and run from the United States and our allies, he's sorely mistaken." Bush on bin Laden
Others, Finzi in 1963, and Sanders in 1984, proposed that the gravitational force becomes stronger at greater radii with the form;
U = -GM(1-Be^(-r/ro))
----------------
(1-B)r
B and ro are beta and r subscript o respectively. Pg 636 Galactic Dynamics. The variables can be selected to eliminate a lot of the dark mass anomalies. But there is no model that gives a reason to justify this or other attempts.
In essence, if the force of gravity becomes a little stronger with large distance, then it would explain the constant velocity profile in spiral galaxies and other organizations of matter without requiring that 90 percent of the mass of the universe be dark matter (Tremaine and Binney, Galactic Dynamics).
Another way of getting a similar thing is if you superpose a thrust directed radially outward that *decreases* with increasing radius. One can assume such a thrust to arise from the mass depletion in stars nuclear reactions, if same emit aether, aka space. Such a mechanism would give rise to a force directed essentially radially outward that was proportional to the amount of energy being emitted inside of the radius being considered. In this case, one gets an equation of the form;
U = -GM + k*sum(Li)
------------------
R
where k is a coupling constant, sum(Li) is the sum of the luminosity of stars from 1 to n that are inside of radius R being considered;
This assumes that the luminosity emitted from inside of radius R is proportional to the total energy emitted, and therefore the mass converted into energy. It also assumes that space consists of a material aether that is emitted during the fusion reaction of mass to energy conversion. Also, the term k is selected to balance out the forces, and the second positive term is always less than G, otherwise individual stars would blow themselves apart like a super nova. Though solar flares and solar coronal heating could be the result of such an emission of aether if aether exists.
Note that due to the form, we would not notice any variance in the orbits of planets about a single star. Only groups of stars will exhibit any peculiarities, ie galaxies. At the boundaries of large groups of stars, there will be a discontinuous reduction in the emissions of aether into space, and so the outward motions of bodies in that aether will be altered and give rise to what would be considered an acceleration inward, when it was actually a *reduction* in the acceleration outward.
Is any one aware of any proposals to alter the form of the Newtonian gravitational potential into this kind of an equation?
Also, does anyone know where Sanders, Finzi, Milgrom, and/or Bekenstein are working today, I would like to get in contact with them regarding their models. Locations and or email addresses would be great.
I have been looking at globular clusters and their velocity dynamics. If correct, then there should be a variance in the gravitational force that is anomolous any time the field drops from being strong to being essentially flat. The reason is the drop off in the repulsive mechanism. A dropping repulsion will appear to be a rising gravitational attraction effectiveness if one bases the analysis on Newtonian gravitation correctly describing the interaction of stellar bodies.
At the maximum radius of a group of stars, ie galaxies or GC's, there should be a marked fall off in the repulsion profile and this should show up as anomalous velocities of stars or gases in those regions. Such is found in GC's but is attributed to "evaporation" ie stars with escape velocity. If it could be shown from measurements of the **accelerations** of the stars or other objects in those regions that the values are too large, then it may be demonstrable implying dark matter in GC's where it is not otherwise believed to exist as I understand.
In the solar vicinity the same thing may be possible by a study of the solar "bubble" and interaction with aether emissions from the Milky Way.
There may also be an assymetry in the direction of the flow that is inclined up out of the disk which would provide an apparent force tending to compress the disk as the expansion falls slightly in that region.
On earth, I don't know yet how to try to measure it. However, solar flare activity is also anticipated to be involved. If the emissions are taking place in the interior of the sun, then they must escape. But we have no manner currently to measure the velocity or actions of "space". It is not even a question deemed askable or intelligible. However the two effects that should occur in and around the sun is a rapid expansion of the aether coming out of the sun which would act like a fluidized bed. And, the increase in the temperature of the gas around the exterior of the sun, ie the solar corona, due to the expansion and formation of a nodal structure to interface with exterior space.
Another curious observation is the polarization of the light coming out of some flares. It implies a commonality to the energy source.
Finally, on earth, some researchers have noted synchronized variance in radioactivity rates at cites thousands of miles apart. And other researchers have noted variances in the gravimetric constant that matched the solar activity. I don't have good references on these last two so don't place a lot of weight on them.
So, in answer, I don't know if we can get it yet but I am looking. I have been hoping to link with others better at the formalization of such a theory. I have the ground work pretty well laid out but need a little more to get some credibility. The formulation of gravitation in the manner of my concepts links it with the other forces.
rtfm
I mean, com'on, things are event-driven or object-oriented, and without objects, one must only assume that an event triggered what was to follow - the big bang. Something was there to explode, and something had to cause it. Did one of the tiny dark matter particles spark up the wrong way and set it off?
:)
Interesting statement. Things are either (A) event-driven or (B) object oriented. But objects have not always existed (that is, the big bang caused the objects to exist). Hence the objects are event-driven (i.e., they are the results of the big bang). Thus everything is event-driven. Thus object are really events. But everything in Java inherits from Object. Thus, Java sucks. quod erat demonstrandum.
Tastes like burning! - Ralph Wiggum
Humans will never be smart enough to do the right tests.