Astronomers discover massive dark matter structure

"Dark matter doesn't absorb or emit light"

Well if it doesn't absorb light, then maybe it should be call transparent matter. Maybe it's a big chunk of ice! And if the ice has some curves in it, then it could be acting as a lens. Maybe that is what is causing the lensing effect instead of gravity. Hmmm...

Hi S.

"Well if it doesn't absorb light, then maybe it should be call transparent matter."

It is transparent for sure, but at the same time, it does not radiate either. Ice would radiate copiously in the cold of space!

Another issue is: of the presumed 27% of critical cosmic density that is matter, only 4% is normal (baryonic) matter like us, stars, gas, ice, etc. The bulk of the dark matter must be exotic (non-baryonic).

Jorrie

Hi Jorrie,

"Ice would radiate copiously in the cold of space!"

Not if it is the same temperature, surely.

I thought the matter was detected by it's effect on the rotational velocities of the outer layers of the galaxies. It would not take exotic matter to have that effect, just cold matter that does not radiate.

"...that is matter, only 4% is normal (baryonic) matter..."

I'm not arguing, but how was this concluded?

Regards,
S

Hi S. You wrote: "Not if it is the same temperature, surely."

on my

"Ice would radiate copiously in the cold of space!"

You're right - a bad lapse of thinking on my part!

The 4% normal (baryonic) matter comes from the nucleosynthesis processes of the early universe, as understood today, e.g. from Wikipedia's http://en.wikipedia.org/wiki/Dark_matter: "However, studies of big bang nucleosynthesis have convinced most scientists that baryonic matter such as MACHOs cannot be more than a small fraction of the total dark matter."

About 4% baryonic, 23% exotic, 73% dark energy, making up the critical energy density for a Ω=1 ΛCDM (Lambda-Cold-Dark-Matter) cosmos.

Jorrie

Hi Jorrie,

Your link verified my assertion of galaxy rotation:

"The observed phenomena consistent with dark matter observations include the rotational speeds of galaxies…", but I don't understand their thinking. The outer layers of the galaxy having speeds like the inner layers violates Kepler's Laws which should apply to greater distances than solar systems. Notice that in the third law, the masses are in the denominator of the formula for T, so that increasing the mass (exotic or otherwise) reduces the sidereal period. The more mass, the slower the rotation by this formula.

Your link suggests that the dark matter may include dwarf stars and planets and primordial black holes. This would make sense because they are high mass entities with relatively small diameters. With the same spacing as normal stars and planets they would not absorb as much light, making the area mostly transparent. Regardless of what it is, it is curious that it is concentrated in the outer layers. Since it is affected by gravity, why would it not be as well integrated as the other types of mass?

I was intrigued by another theory in that link that says that other universes could affect our gravity (some theories of brane cosmology…). Do you have an opinion on this?

I certainly agree with one thing in that link "It has been noted that the names 'dark matter' and 'dark energy' serve mainly as expressions of human ignorance…".

Regards,

S

Hi S, apologies for the delayed response.

You wrote: "Notice that in the third law, the masses are in the denominator of the formula for T, so that increasing the mass (exotic or otherwise) reduces the sidereal period."

True for mass at the center, but in galaxies, the bulk of the dark matter is postulated to be more or less evenly spread up to the halo around the galaxy. Kepler's laws do not apply in such a system.

"I was intrigued by another theory in that link that says that other universes could affect our gravity (some theories of brane cosmology…). Do you have an opinion on this?"

Difficult to test, but possible. There is even a possibility that both dark energy and dark matter could be "leakage" from other dimensions...

Jorrie

Hi Jorrie,

You said "Difficult to test, but possible. There is even a possibility that both dark energy and dark matter could be "leakage" from other dimensions..."

Wow! Think of the possibilities. The WIMP (if found) could be the portal to ?????

-John

"...the bulk of the dark matter is postulated to be more or less evenly spread up to the halo around the galaxy. Kepler's laws do not apply in such a system."

Is that just your opinion, or do you have an explanation or a link that supports that belief?

Hi S. You asked: "Is that just your opinion, or do you have an explanation or a link that supports that belief?"

The http://en.wikipedia.org/wiki/Dark_matter has a reasonably good explanation and plenty of technical references.

Quote: "Galaxies show signs of being composed largely of a roughly spherically symmetric, centrally concentrated halo of dark matter with the visible matter concentrated in a disc at the center."

Jorrie

Hi Jorrie,

I didn't see anything in that link that explains my question. In the following link

http://astro.berkeley.edu/~mwhite/darkmatter/essay.html

Joe Silk says "The rotation velocity is found not to decrease with increasing distance from the galactic center. This constancy of velocity implies that the galaxy's cumulative mass must continue to increase with the radial distance from the center of the galaxy..." This is what I don't understand. How does it imply that?

He also states "What could the dark matter be? The dark matter in the disk most likely consists of very dim stars, such as white and even black dwarfs." This disagrees with the conclusions in the posts above. Somewhere I got a link to "A Historical Perspective on Dark Matter" by Scott Tremaine that I made into a .pdf file. It really points out that there is a crisis in cosmology. I have to agree with that.

Regards,

S

Hi S,

I think Joe did not state it clearly. I understand it this way: Newton's gravity demands that stars in a disk have differential orbit speeds starting from very low near the center, increasing rapidly as you measure outwards, until it starts to drop off again, in almost Keplerian style. Most disk galaxies show the initial increase, but not the drop-off, i.e., from some distance out the orbital speeds remain roughly constant.

If Newton's theory remains valid at galactic scales, this requires a massive, roughly spherical halo to surround the disk. There are visible halo stars, but not enough visible mass by far. It is also highly unlikely that the dark mass can be black holes or other compact baryonic mass - the nucleosynthesis theories after the BB do not allow so much baryons...

Hope this helps.

Jorrie

Do I understand this properly:?The galaxies behave as if they were one solid "wheel" instead of billions of separate stars? If so, then perhaps there is a mutiplying or regenerative effect of gravity that binds these parts together as one.

If you place one magnet behind another magnet, polarised in the same direction, the net force is increased on the opposite end of the magnets.They re-inforce each other.Could gravity work the same way?Would this not tend to lock everything in synch, or has this effect already been considered, or is it invalid?

Hi HTRN.

No, no, not like 'one solid wheel'; the actual speeds of the stars in the disk (outside of the core) are observed to be more or less the same. In a solid disk, the outer speeds go up linearly with radius.

Ordinary Newton demands that the speeds drop with distance, but they don't...

Jorrie

Jorrie, you said:

"If Newton's theory remains valid at galactic scales, this requires a massive, roughly spherical halo to surround the disk."

Not true according to this link:

http://mb-soft.com/public/galaxy.html

This has the explanation I was looking for. Here are some important points from the link:

"There is a rather strong gravitational "restoring force" acting on the Sun to transversely keep it within our Arm, and there is also a "forward boost" acceleration which aids the Sun in "keeping up" with the portions of the Arm that are forward and inward of it."

"This current presentation insists that each Spiral Arm has gravitational self-cohesion. This results in the component stars and other objects being decelerated when moving away from the Galactic Plane, by the billions of solar-masses "behind" it collectively providing that deceleration. In fact, the result certainly is that all such stars and other objects must be oscillating in the Arm (vertically) along the Z-axis."

"There are claims that enormous amounts of invisible mass must exist, as in a giant massive halo around the galaxy, but such claims seem to never have contemplates where that mass would have to be! In some such theories, a super-massive halo is supposed to exist OUTSIDE the Galaxy, but Newton showed us that such external mass would have no gravitational effects interior to it. In some such theories, a very massive torus of invisible material (dark matter, hidden matter, neutrinos) would have to exist around the rim of the Core, and additional peculiar distributions of that mass would have to exist, in order to cause the non-Keplerian fast revolving of the Spiral Arms. The alleged distribution is often simply referred to as an invisible halo! Such a structure would not be stable or even meta-stable."

There are many links within this link. I have a lot of reading to do!

Regards,

-S

Hi S, pardon me for not reading the link: it is from the same 'crank' that wrote about the 'twin paradox'.

If you can find corroborating scientific evidence (preferably peer reviewed), I'll be very interested, but I have little hope...

Jorrie

This article makes a lot of sense to me. That doesn't happen very often in an article like this.

"If you can find corroborating scientific evidence (preferably peer reviewed)..."

Just because 95% of the scientists get on the same 'ride', I will not accept their views until they give a clear and concise explanation. None of the links I have found on this subject have any explanation at all. Did Einstein have his theories peer reviewed before he submitted them? I don't think so. I will keep reading until I get some answers, clearly there are no answers here.

S

You go S!

I admire your tenacity.

-John

Hi S.

"Just because 95% of the scientists get on the same 'ride', I will not accept their views until they give a clear and concise explanation."

That 95% may be wrong on the existence of dark matter, but they are surely not wrong on Newton! The observations are 99.9% compatible with a homogeneous, spherically symmetrical concentration of mass within which the core and disk of a galaxy are embedded. Dark matter tends to clump together and is virialized just like ordinary matter; hence it does not only exist in a halo. On the larger scales, where the bit of matter in the disk becomes relatively unimportant, the rotation speeds follow Newton closely for the field inside a rotating, homogeneous ball of particles.

With that said, Newton's law may not hold at galactic scales, which may change the whole premises. It is still possible that dark matter is not required to explain the observations, but the article that you referenced, claiming to do it within Newton's framework, does not cut the muster. Example: "It is important to note that the scale of these accelerations are comparable to the Keplerian central force. They exist because the assumption of "symmetric mass distribution of the Galaxy" on which the Keplerian formulas are based, is not true, because of the presence and massiveness of the Spiral Arm structure."

Huh? Keplerian formulas only hold outside of a spherically symmetrical mass distribution.

Regards,

Jorrie

OK, Jorrie, you apparently read some of it since you made a quote. I think that you can see I'm frustrated in that I find the only explanation and you thumb it down. Let's see where we stand. I'll post some assertions from his article, and you can tell me if you agree. [I'll put my 'translation' or comments in square brackets]

1. "...galaxy spiral arm dynamics is primarily a combination of this "intra-arm" self gravitation and the traditional Keplerian central force effect. Both are simple applications of standard Newtonian gravitation." [mutual gravity between masses in the spiral arm tend to make it act like one mass and complicate the Kepler's law mathematics]

2. "...there is a significant net forward acceleration imparted on the Sun... because of the greater amount of mass in front of the Sun than behind it" "This forward effect enables the Sun to revolve around the Galaxy more quickly than suggested by Kepler alone ." [the mass between the galaxy core hastens the suns rotation around the galaxy, and BTW, the mass outside the sun's orbit slows down the sun's orbital velocity. The outer mass does not quite keep up, that's why it's a spiral]

3. "Our Milky Way Galaxy, like millions of other galaxies, has "spiral arms", which tend to be relatively symmetric... The fact that there are millions of other galaxies that have spiral arms seems to suggest that the arm structures are either stable or meta-stable in nature."

4. "There is strong empirical evidence that our Sun is currently moving (locally) toward a point in the direction of mu Herculis, which is around 26° degrees UPWARD of the Plane of our very thin Galaxy. The upward (Z-direction) velocity we have would cause us to entirely leave the Galaxy in only around 9 million years, barely a moment in the lifetime of most stars or a Galaxy [if it does not change direction sometime]."

5. "The complexity of a galaxy is such that BOTH the principles of Keplerian revolution AND this gravitational Arm self-cohesiveness must apply" [the sun rotates around the galaxy at a different rate than if it was by itself because of the other stars (and maybe dark matter in the arm)]

Well, it's getting late, and this is probably enough anyway. JohnJohn, HiTekRednek,Vermin,Roger Pink, feel free to jump in. Let's have a discussion!

-S

Hi S, OK, let's give it a go.

1. I tried to say many times now that Kepler's laws are not used in galactic rotational computations. The 'virial theorem', which is based on purely Newtonian principles are used. When all the sums are properly made, you are left with an excess observed speed, which Newton cannot explain...

2,3. To look at the Sun's speed has little benefit. The observations are from many 'edge-on' spiral galaxies (which is the only ones for which we can measure the orbital velocities), where the star velocities show the excess values. Your comment is more or less in line with conventional thought, except that stars are not 'bound' to the spiral arms, which are thought to be high pressure areas (actually sonic shock waves), where lots of new, hot stars are born. Individual stars are apparently free to move through the arms in their orbital paths.

4. Most stars may have an 'upward-downward' oscillation relative to the disk in their orbits. Studies of such movements are also supporting the dark matter halo theory. There are some highly technical papers on this, which I do not have access to right now - I'm away from my home base.

5. There is probably dark matter in the arms, but the latest thoughts are that a significant dark halo mass is needed to explain the complete orbital characteristics (using Newton, if Newton applies as is ...)

As 'S' has requested, anybody else with ideas?

Jorrie

Hi Jorrie,

"I tried to say many times now that Kepler's laws are not used in galactic rotational computations."

Yes, I know you said that, but there is a difference between "not used" and "could be used" and "was used". This is the first time you gave an explanation. Thanks for the link. I must ask one hypothetical question: If all matter except the sun and the galactic core was removed, do you believe that the sun would follow Kepler's laws in orbiting the core? (or do you think there is a range limit to the law?)

I assume that in the virial theorem each star and planet is considered a particle. Planets orbit stars, so maybe they don't apply? In any case nobody knows how many there are or how far apart (there could be many black dwarfs and black holes intermixed). It is beyond me how anybody could calculate the total effect. It is interesting to find that this theorem lead to the theory of dark matter. Something puzzles me: the theorem sums the force on each 'particle'; People (like you?) who support Einstein's theory of gravity, don't believe gravity has a force. ?????

"...you are left with an excess observed speed, which Newton cannot explain"

Carl Johnson can.

Concerning the oscillation of stars in the arm, I didn't notice an explanation in Carl's article. I am very interested in those technical papers that you mentioned. Like our other topic, this may take some time. That's it for now.

Regards,

-S

Hi S. You asked: "If all matter except the sun and the galactic core was removed, do you believe that the sun would follow Kepler's laws in orbiting the core? (or do you think there is a range limit to the law?)"

If Newton and Einstein are right, there is no range limit to Kepler's laws, for scenarios where they are applicable.

"Something puzzles me: the theorem sums the force on each 'particle'; People (like you?) who support Einstein's theory of gravity, don't believe gravity has a force. ?????"

In Newton's theory, gravity is a viewed as a force in 3D space. In Einstein's, it is viewed as geodesic movement in 4D spacetime, but that is (sort-of) a convention. If you take an object and drop it, you observe acceleration towards Earth's center, so you are entitled to view it as a force pulling it towards Earth. If you consider the spacetime geodesic as your reference frame, then there is no acceleration. As we are sitting in front of our computers, the chairs are accelerating us out of our geodesics. It's a matter of reference frame...

"Carl Johnson can. "

I beg to differ!

Jorrie

Jorrie,

How does the behaviour of the stars in the spiral arms of our galaxy about the galactic core differ from the orbits of the particles that form the rings around Saturn, and the rings as a whole?

Hi Guest, you asked: "How does the behaviour of the stars in the spiral arms of our galaxy about the galactic core differ from the orbits of the particles that form the rings around Saturn"

Galactic disks make up a considerable portion of the mass of the galaxy. Saturn's rings have negligible mass compared to the system. Actually, the rings are very much perturbed by the many large and small moons of Saturn. No real similarities between the systems (galactic disks and planetary rings), I think.

Jorrie

Hi Jorrie,

"5. There is probably dark matter in the arms, but the latest thoughts are that a significant dark halo mass is needed to explain the complete orbital characteristics (using Newton, if Newton applies as is ...)"

In some recent reading I found this in a book Mysteries of the Universe by Nigel Henbest (1981):

"Computer simulations of spirals show that we can stop a bar forming if there is a lot more matter in the halo than we think. Its gravitational effect would be more powerful than any of the disk, so the stars of the disc would circle in the uniform gravitation of the halo with relatively little of the gravitational pull from the other disk stars which leads to a bar forming."

There may, however, be more to it such as the shock waves that you mentioned, cosmic strings, or electromagnetic forces which are extremely more powerful than gravity. This thought was reinforced by another statement in the book:

"Io is linked to jupiter by a 'flux tube' through the magnetic field, which carries an electric current of five million amps between Io and jupiters magnetic poles."

That's a lot of current, and illustrates the 'potential'.

regards,

S

Hi S, you wrote:

"Io is linked to jupiter by a 'flux tube' through the magnetic field, which carries an electric current of five million amps between Io and jupiters magnetic poles."

That's a lot of current, and illustrates the 'potential'.

Wow! Frightening, actually, illustrating the forcefulness of nature!

Jorrie

Any indication of the voltage driving this current? P=IE?

I'm just curious about total power.

Hi HTRN,

"Any indication of the voltage driving this current? P=IE?"

No, this was by a 'picture' and also said that Io ejects atoms of sodium, sulphur, and hydrogen into a cloud which extends around Io's orbit, and that as the current penetrates Jupiter's atmosphere it produces intense aurorae. The two Voyagers didn't have long enough probes to measure the voltage . I'm guessing that the current was calculated from the magnetic field measurements.

regards,

S

Hello StandardsGuy

if the current is so large, as computed from the magnetic field, then the driving EMF over such a distance has to be hundreds of trillions of Volts.

What Earth needs, is a safe way of extracting that energy, and using it, if possible.

Kind Regards....

The summary above says: "Astronomers can infer its presence because it does have a gravitational pull, which affects other matter."

True, but at the same time misleading to an extent. The mechanism by which these structures were detected is by gravitational lensing of more distant galaxies, not by the effect on other matter.

Jorrie

PS: I have written something on gravitational lensing on CR4 before, where the lens was a galaxy; the same principles apply to dark matter lenses.

Gravitational lensing is caused by warping space time.Space time is warped by gravity.Gravity has an effect on matter and energy.Therefore the dark matter must have an effect on normal matter.It may not directly interact with matter, but it acts on matter in more subtle ways.It could cause matter to clump together to form galaxies,which would explain how galaxies stay together and don't fly apart.The galaxies are caught in a "spiderweb" of gravity caused by dark matter.

IMHO

My use of "spiderweb" was a poor analogy.Perhaps space time is not smooth on very large scales.Perhaps the "dark matter" is really dimples that formed in space time after the big bang .These would tend to make matter accumulate into the dimples, forming galaxies, etc. Note that dark matter is always near galaxies.So which came first, the galaxies or dark matter(dimples).

HTRN

It's all the fault of those software robots, who escaped from a laboratory some 30 years ago.

Now that they have spun a world wide web, they moved off-planet, and are now infesting space, to catch others in their web.

Kind Regards....

So if the mass of the Milky Way is aprox.2x10^42 kg, then there is about ten times that amount of dark matter in a sphere surrounding it? WOW!

An unseen, but definitely felt influence.

So what is the density of this dark matter, relative to visible matter,if is is contained within a sphere roughly the diameter of the Milky Way?(Assuming uniform density).

Hi HTRN, you asked: "So what is the density of this dark matter, relative to visible matter, if is is contained within a sphere roughly the diameter of the Milky Way?(Assuming uniform density)."

On large scale averages, the ~10:1 ratio of dark matter to baryonic matter density holds up well to a wide spectrum of astronomical observations. On cosmological scales, matter seems to make up 27% of the total energy density of the universe, while only about 4% seems to be visible, about a 7:1 ratio. For some galaxies, the ratio can be as high as 20:1.

http://en.wikipedia.org/wiki/Dark_matter seems to be a good, accessible source of dark matter information, including the history and the most recent findings.

Jorrie

When the space shuttle deployed a tether to test the power generated as it orbited the Earth, the first attempt destroyed the tether.The current was much higher than anticipated.Later attempts succeeded.By pumping current into the tether, the shuttle could be accellerated, by taking current out of the tether, it could be slowed.Newer satellites use tether technology to maintain proper orbit.No chemical fuel required!

Now, if we could harness that power and beam it back to Earth, via microwave, the potential is tremendous.Using the Earth to power the Earth.Of course, in a few million years we willl have slowed the rotation by a few milliseconds, but that will just give more daylight.

Hi Guest, you wrote: "Now, if we could harness that [orbital] power and beam it back to Earth, via microwave, the potential is tremendous."

Unfortunately, power extracted from a satellite's orbit must be replaced, probably by solar power. Not worth the bother, because we can do that cheaper here on Earth.

We are already using Earth's rotation to "power Earth" in by means of tidal current energy extraction (OK, the Moon also helps a bit there).

Jorrie

For those who have read my latest thread "The Big Bang Never Happened", what do you think of this quote from the article above?:

"Theories of dark matter suggest it formed a kind of gravitational well where hot gas from the big bang collected. The gas formed the first stars and galaxies."

Hot gas is plasma, is it not? Do you still believe this is dark matter?

S

Hi S, you wrote:

"Theories of dark matter suggest it formed a kind of gravitational well where hot gas from the big bang collected. The gas formed the first stars and galaxies."

Hot gas is plasma, is it not? Do you still believe this is dark matter?

Yea, because the current model says that hot plasma only makes up some 25% of the mass-energy of the early universe (ignoring dark energy). The other 75% is dark, so only 25% shines. Dark matter could have formed the gravitational wells into which the plasma collected.

Jorrie

For every action, there is an opposite and equal reaction.Where is the equal and opposite reaction to the big bang?Could it be in another dimension, and could gravity be a multi-dimensional effect, causing space-tiem warpage in our universe, possibly as our gravity causes the same effect in the other dimension?The hourglass shape, seen from only one side, looks like a funnel, and since we cannot be outside and inside of our dimension at the same time,that is all we will ever see.There is symmetry in nature, and I believe it is present from the largest to the smallest scales.

We live in a small triangle of reality, and we are connected to other triangles to form squares.Half of them are like our dimension, half are like the other.The divider is the speed of light.The common mode for all is gravity.

HTRN

After reviewing my post, I see I did not relate precisely what I was thinking, so I will attempt to expound on the triangle analogy.Take a piece of graph paper.Plot time on one axis, and the speed of light on the other axis.Scale the time to a maximum of 1 second, and the distance of 300000kms, the speed of light.Draw a line along the known speed of light, and, and you will get a triangle. We are bounded by this triangle, and the other half of the square is another dimension.This other dimension is also bounded by the speed of light, but as the minimum speed, not the maximum.Keep adding squares,all constructed the same way,like a tile floor that goes on for infinity.There are adjacent dimensions that have the same laws as ours, but to get there would require a time-travel trip, to weave out of our dimension and back into theirs.Maybe thru a wormhole of sorts.Now that we have that concept, make cubes from the squares.It gets very interesting after a while considering the possibilities.

I will leave the rest of the speculation to you: the loyal and patient readers and teachers.

HTRN