"dark matter"

[supafunky]

scientists and astronomers are searching for dark matter inside the known universe, but have they considered the universe could be being pulled from the outside?

 

[pyoko]

Things like galaxies (definitely small objects inside the Universe) and clusters of galaxies behave as if there is dark matter within them, not a pull from somewhere infinitely distant, so, no.

 

[trumptor]

Maybe he was referring to dark energy.

 

[MeteorWayne]

It would be good if posters starting the 6th thread on the same topic knew what they were talking about.

I know, far too much to ask....

 

[supafunky]

can you xplain what you mean by they act like there is dark matter within them?

 

[SteveCNC]

first , your confusing dark matter with dark energy for the ummm speeding up of the expansion of the universe .

Dark matter is responsible for gravitational behaviours in more local areas than the universe at least that's current thought if I'm not mistaken .

Dark Energy is the force accelerating the expansion of the universe .

 

[csmyth3025]

can you xplain what you mean by they act like there is dark matter within them?

An overview of the current thoughts on dark matter (why we think it's there, for instance) can be found in the Wikipedia article on it here:

http://en.wikipedia.org/wiki/Dark_matter

Chris

 

[kk434]

Dark energy might be located outside the observable universe, it is so mysterious that there is not even a clue to what it may consist of. Dark matter is relatively well understod, it has mass that affects the galaxy rotation curve, stars rotate around the galaxy center much faster then what Newtons laws predict. Being unable to interact with photons makes it dark.

 

[acsinnz]

Dark matter is I believe the invisible matter that we know is there as observation show a star wobble or blink. Beyond that there is dark gases and ions in the vacuum of space.
But dark energy should be renamed "the force pushing the universe apart" which may well be an electric magnoflux force with no mass in it whatsoever.
We haven't lost 70% of the universe really; only the gravitationalists have!
CliveS

 

[csmyth3025]

Dark matter is I believe the invisible matter that we know is there as observation show a star wobble or blink. Beyond that there is dark gases and ions in the vacuum of space.
But dark energy should be renamed "the force pushing the universe apart" which may well be an electric magnoflux force with no mass in it whatsoever.
We haven't lost 70% of the universe really; only the gravitationalists have!
CliveS

Your statement: "...Dark matter is I believe the invisible matter that we know is there as observation show a star wobble or blink...." indicates that your confusing dark matter with companion objects that are orbiting a star. The observations you mention are largely responsible for the inferred detection of exoplanets, as explained in the Wikipedia article on this subject here:

http://en.wikipedia.org/wiki/Exoplanets

Dark matter, on the other hand, is believed to be something other that just "normal" gas and ions that we can't see, as expained in the Wikipedia article here:

http://en.wikipedia.org/wiki/Dark_matter

Dark energy can, indeed, be aptly described as "the force pushing the universe apart". A good explanation of the current thoughts about it and why we think it's there can be found in the Wikipedia article here:

http://en.wikipedia.org/wiki/Dark_energy

Chris

 

[acsinnz]

Thanks Chris
The real problem is that the standard gravitional model from wikipedia considers that there is no electric fields in space as the positive charges cancel out the negatives in all matter.
We used to think that the solar system was the same; until the solar wind was discovered.
If there are any gas molecules in the space between the sun and earth they will be ionized only if a voltage is applied. The solar wind is full of protons or H+ ions not hydrogen molecules. If the sun earth connection voltage collapses then the H+ ions will pair with a free electron and a gas molecule will just float around in the vacuum.
There are, I am sure, electric fields in outer space also which may have the effect of being a force that pushes the universe apart. We cant ignore these electric fields forever! or can we?
CliveS

 

[csmyth3025]

There are, I am sure, electric fields in outer space also which may have the effect of being a force that pushes the universe apart. We cant ignore these electric fields forever! or can we?
CliveS

There are a lot of researchers out there who are a lot smarter than me. I suspect that the extent and the effect of electric fields in space have been thoroughly studied. If it is possible to attribute some or all of the force of "dark energy" to the effect of electric fields I'm sure the scientific community would be overjoyed.

For scientists to admit that 70% of the matter/energy of the universe is something that they have no idea what it is or how to detect it directly, it is an embarrassment of the highest order. They're not likely to ignore anything that stands the slightest chance of getting them out out their quandary.

Chris

 

[Saiph]

You've got an odd concept of electric fields. Yes, there are charged particles in space, but taken as a whole, or over any significant area (like a cubic meter) the overall charge is zero. The solar wind, despite being made up of individual charges, is NEUTRAL in composition.

In order for an electric field to arise, you need to separate the charges, to create a voltage. And that takes energy, and a mechanism. You can't just 'apply a voltage' and watch the charges separate.

While there are large electric, and especially magnetic fields in space, they cannot account for the very, very large discrepancies we see in our data that we call 'dark matter and dark energy'

 

[acsinnz]

Yes Saiph it is neutral in composition BUT the H+ ions are coming towards us from the sun and the electrons are going back towards the sun. That balances very well and would be electrically correct.
You give the impression that the H+ ions and electrons are just floating around with no where to go which is electrically incorrect as a couple would get together with the electrons and form a hydrogen gas molecule given half a chance.
CliveS

 

[csmyth3025]

Yes Saiph it is neutral in composition BUT the H+ ions are coming towards us from the sun and the electrons are going back towards the sun. That balances very well and would be electrically correct.
You give the impression that the H+ ions and electrons are just floating around with no where to go which is electrically incorrect as a couple would get together with the electrons and form a hydrogen gas molecule given half a chance.
CliveS

I'm not sure how you arrived at the conclusion that "the H+ ions are coming towards us from the sun and the electrons are going back towards the sun" but this idea is wrong. The solar wind is composed of energetic protons and electrons moving away from the sun. An overview of this phenomenom can be found in the Wikipedia article on it here:

http://en.wikipedia.org/wiki/Solar_wind

The energy (speed) of the electrons is too high for them to couple with the protons and form hydrogen atoms. Thus, the solar wind is composed of separate positively and negatively charged particles which are, overall, electrically neutral. The solar wind is a plasma, which you can read about in the Wikipedia article on it here:

http://en.wikipedia.org/wiki/Plasma_(physics)
NOTE: for some reason this link keeps dropping the last parenthesis mark, which resuluts in directing you to a wiki query page. Just add the last parenthesis to the address in the url bar or click on the link to the correct page indicated in the query.

Chris

 

[acsinnz]

Chris
I have read these articles before but there are so many different alternative theories none of which seem to fit in properly with the lamda CDM model. I still believe that electric fields 5th forces are causing the expansion but we will just have to wait and see what new evidence can be found in space.

CliveS

 

[michaelmozina]

scientists and astronomers are searching for dark matter inside the known universe, but have they considered the universe could be being pulled from the outside?

FYI, the term "dark matter" typically applies to "missing mass" that is related to galaxy rotation patterns, and/or lensing patterns that are seen around various galaxies. One expects to find "missing mass" in and around galaxies, but it would not accelerate the universe in any way, it would act like any other mass and tend to "slow it down over time" just like any other type of mass.

The term "dark energy" is the term that I believe you meant to refer to. The term "dark energy" relates to a "pattern of acceleration" of the whole physical universe that can be interpreted from redshift patterns. That acceleration process could in fact be "caused"" by mass located around the outside of our physical universe. External mass *could* cause acceleration or what we think of as "dark energy".

 

[EarthlingX]

http://en.wikipedia.org/wiki/Plasma_(physics)
NOTE: for some reason this link keeps dropping the last parenthesis mark, which resuluts in directing you to a wiki query page. Just add the last parenthesis to the address in the url bar or click on the link to the correct page indicated in the query.

Chris

You can also enclose in the URL tag, like this :

[url]http://en.wikipedia.org/wiki/Plasma_(physics)[/url]

http://en.wikipedia.org/wiki/Plasma_(physics)

or even better, like this :

[url=http://en.wikipedia.org/wiki/Plasma_(physics)]Plasma (physics)[/url]

Plasma (physics)

 

[csmyth3025]

Thanks for the tip EarthlingX

Chris

 

[EarthlingX]

Thanks for the tip EarthlingX

Chris

Thank you for your nice post.

 

[acsinnz]

OK earthlingx thanks for redirection to plasma_physics.

My only observation is that the plasma fountain diagram is confusing me as the hydrogen and oxygen are needed here on planet earth to form water and the electrons need to return to the sun [star] to release light. How can we be sure which way the plasma gas and electron flows are in? With electricity historically we nearly always get the flows in the wrong direction!

 

[MeteorWayne]

The sun doesn't need electrons to produce light. It is produced by a "nuclear" reaction, i.e. related to the nucleus of atoms.

 

[a_lost_packet_]

scientists and astronomers are searching for dark matter inside the known universe, but have they considered the universe could be being pulled from the outside?

Actually, yes. Though, I don't know what links to pull up right now to confirm that. If necessary, I'll drag some up.

But, the idea is that there could be mass outside of our Universe acting upon it. There are problems, though. The biggest one is "Where did it come from?" For that amount of mass to have originated with our own "Big Bang" it would mean that our Universe should be collapsing in on itself, not being drawn outwards by it's own mass. That's just not something that could be seen to easily happen.. What we know insists that gravity doesn't work like that.

Another problem is gravity and the speed of light. As far as we know, mass is communicated by gravity at the speed of light. If the Sun moved, the Earth would respond in 8 minutes or so. If this is consistent everywhere, things at the extreme edge of our visible horizon and beyond would be receding faster than gravity could compensate for. At some point, gravity would never be able to catch up as the distance between them and other objects expanded at greater than c. (At least, relative to our own visible horizon.) Differences in these effects due to relative positions and visible horizons should be something that would be noticeable if there was mass that was outside of our own visible horizon, having an effect. I don't know that many have found any. But, IIRC, there have been some that have theorized specific cases recently in the past couple of years or so. (Can't remember who, but I think SDC had an article on it.)

Combined with the two comes the last unlikely effect - The Universe seems to be expanding uniformly and at an increasing rate. In fact, points appear to be receding from any point in the Universe you'd care to look, allowing for direction of travel, of course. So, our view from Earth in regards to expansion should be no different than the view anywhere else. If there was mass outside our visible horizon, somehow fueling this expansion, how could we explain its uniformity of effect? How could we explain the increasing rate of expansion? Whatever the theory is, it must comply with observation. There isn't an easy, observable, way to prove that mass outside our visible horizon would be able to accomplish what we observe as expansion.

Some have even thought that our Big Bang might not be the only one in this Universe. But, because the others would be outside of our visible horizon, we'll just never be able to know. Certainly, it wouldn't be noticeable until they began to interact with each other within a visible horizon. If that ever happens, things will certainly get interesting.

 

[EarthlingX]

Wiki : Dark flow

Dark flow is a term from astrophysics describing a peculiar velocity of galaxy clusters. The actual measured velocity is the sum of the velocity predicted by Hubble's Law plus a small and inexplicable (or dark) velocity flowing in a common direction.

The authors (A. Kashlinsky, F. Atrio-Barandela, D. Kocevski, and H. Ebeling) suggest that the motion may be a remnant of the influence of no-longer-visible regions of the universe prior to inflation. Telescopes cannot see events earlier than about 380,000 years after the big bang, when the universe became transparent (the Cosmic Microwave Background); this corresponds to the particle horizon at a distance of about 46 billion (4.6×1010) light years. Since the matter causing the net motion in this proposal is outside this range, it would in a certain sense be outside our visible universe; however, it would still be in our past light cone.

http://www.nasa.gov : A measurement of large-scale peculiar velocities of clusters of galaxies: results and cosmological implications. (pdf)

A. Kashlinsky1, F. Atrio-Barandela2, D. Kocevski3, H. Ebeling4
ABSTRACT

Peculiar velocities of clusters of galaxies can be measured by studying the fluctuations in the cosmic microwave background (CMB) generated by the scattering of the microwave photons by the hot X-ray emitting gas inside clusters. While for individual clusters such measurements result in large errors, a large statistical sample of clusters allows one to study cumulative quantities dominated by the overall bulk flow of the sample with the statistical errors integrating down. We present results from such a measurement using the largest all-sky X-ray cluster catalog combined to date and the 3-year WMAP CMB data. We found a strong and
coherent bulk flow on scales out to at least >» 300h¡1Mpc, the limit of our catalog. This flow is difficult to explain by gravitational evolution within the framework of the concordance ΛCDM model and may be indicative of the tilt exerted across the entire current horizon by far-away pre-inflationary inhomogeneities.

news.nationalgeographic.com : New Proof Unknown "Structures" Tug at Our Universe

John Roach

for National Geographic News

Published March 22, 2010

The Coma Galaxy Cluster, which appears to participate in the mysterious motion known as dark flow.

"Dark flow" is no fluke, suggests a new study that strengthens the case for unknown, unseen "structures" lurking on the outskirts of creation.

In 2008 scientists reported the discovery of hundreds of galaxy clusters streaming in the same direction at more than 2.2 million miles (3.6 million kilometers) an hour.

This mysterious motion can't be explained by current models for distribution of mass in the universe. So the researchers made the controversial suggestion that the clusters are being tugged on by the gravity of matter outside the known universe.

Now the same team has found that the dark flow extends even deeper into the universe than previously reported: out to at least 2.5 billion light-years from Earth.

After using two additional years' worth of data and tracking twice the number of galaxy clusters, "we clearly see the flow, we clearly see it pointing in the same direction," said study leader Alexander Kashlinsky, an astrophysicist at NASA's Goddard Space Flight Center in Maryland.

"It looks like a very coherent flow."

The find adds to the case that chunks of matter got pushed outside the known universe shortly after the big bang—which in turn hints that our universe is part of something larger: a multiverse.

[youtube]http://www.youtube.com/watch?v=9dRnDFR-QYI[/youtube]

SpaceFellowship
March 11, 2010

The colored dots are clusters within one of four distance ranges, with redder colors indicating greater distance. Colored ellipses show the direction of bulk motion for the clusters of the corresponding color. Images of representative galaxy clusters in each distance slice are also shown. Credit: NASA/Goddard/A. Kashlinsky, et al.

 

[EarthlingX]

news.discovery.com : U.S. Lab Simulates the Awesome Power of Galactic Mergers

Analysis by Ian O'Neill

Sat Oct 2, 2010 06:55 AM ET

The scales are mind-boggling and the physics is cutting edge, so how do you go about simulating the collision of two galactic clusters? Using some of the most powerful computers in the world, researchers at Argonne National Laboratory near Chicago Ill. have done just that.

...

The code simulates the interaction of both normal matter and dark matter. The normal matter interacts, mixes and generates turbulence as the collision progresses. For this component of the simulation they use a hydrodynamic code -- it's basically the science of how two liquids or gases mix. As the two clouds of dark matter inside each cluster can only interact gravitationally (the dark matter particles cannot collide, or scatter, via any other mechanism), each particle is modeled individually. This an N-body code.

Once the simulation is sent on its way, the mixing of normal matter is simulated along with the dark matter. As the dark matter cores from both clusters reach an equilibrium state, orbiting inside the post-collision cluster, its motion gravitationally mixes the normal matter.

"The dark matter cores slip past and through each other,whereas the two gas components interact and mix," narrator Carrie Eder explains during the collision visualization.

"It is also clearly seen that the mixing of the gas is driven completely by the violent orbital motion of the dark matter cores."

Here is the simulation in all its glory:

[youtube]http://www.youtube.com/watch?v=opP7ttCCC20[/youtube]

ArgonneNationalLab | August 09, 2010

Since structure in the universe forms in a bottom-up fashion, with smaller structures merging to form larger ones, modeling the merging process in detail is crucial to our understanding of cosmology. At the current epoch, we observe clusters of galaxies undergoing mergers. It is seen that the two major components of galaxy clusters, the hot intracluster gas and the dark matter, behave very differently during the course of a merger. Using the N-body and hydrodynamics capabilities in the FLASH code, we have simulated a suite of representative galaxy cluster mergers, including the dynamics of both the dark matter, which is collisionless, and the gas, which has the properties of a fluid. 3-D visualizations such as these demonstrate clearly the different behavior of these two components over time.

Credits:
John Zuhone (Harvard-Smithsonian Center for Astrophysics), Don Lamb (Flash Center, U of C), Jonathan Gallagher (Flash Center U of C)

This work was supported in part by the DOE NNSA ASC ASAP and by the NSF. This work also used computational resources at the ALCF at ANL awarded under the INCITE program, which is supported by the DOE Office of Science.

This simulation was completed in part using the computational resources of the Argonne Leadership Computing Facility at Argonne National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under contract: DE-AC02-06CH11357.

This visualization was produced using the visualizationand analysis resources of the Argonne Leadership Facility that is supported by the Department of Energy's Office of Science.