Dark Matter/Energy Silliness?

Question

Dark matter and energy seem to be very vague and convienantly make-shift to me. A blanket thrown over the short-commings of our current understanding of gravity.

If 11-D String/M theories are on base at all, couldn't gravity be MUCH stronger then we see it as, holding objects togeather more tightly in higher dimentional states then we can detect?

EXAMPLE: Could gravitons, with very high degrees of freedom, perhaps form tendrils in higher dimentions that hold the galaxies togeather like cosmic bailing wire?

Answer 1

As a fan of M theories, i tend to agree with you. Did you know that if you tweak newtons acceleration equations ever so slightly, the galatic rotations make sense without Dark Matter? Its a theory called MOND (MOdified Newtonian Dynamics). Basically it says the instead of F=ma the equation for acceleration on large scale (galactic) objects is more like F=mµ(a/a0)a, where there is more of a distinction in the types of acceleration...and that is a sub-zero in the equation, it doesnt make sense with a real zero :) anyway, its not widely accepted because there is no why for the equation change at large scales, and cosmologists and most physicists dont like that. But it does totally dispel Dark Matter; theres no need for it when you use the modified equations to explain the faster rotation in the outer reaches of galaxies.

maybe you're onto the why :) keep looking into it!

Answer 2

Dark matter and dark energy are yet to be explained. This is true. However, there are physically plausible explanations for each which do not require us to resort to string theory.

Dark matter, in and of itself, need not be so far-fetched as one might think. Really, we think it's just particles which don't happen to interact electromagnetically. That is, they have no charge and no magnetic moments. Why should this be so inconceivable? Various extensions to the Standard Model of particle physics (ie, supersymmetry) give rise to particles which fit the bill. There are currently experiments being started to try to detect the dark matter particles through the Weak interaction. If they are successful, then the mystery will be solved.

Dark energy can be explained in two ways. The first is through Einstein's cosmological constant. If you've ever performed an integration, then you know that you need to tack on an arbitrary constant. Einstein's equations required this as well, although he thought it was unnecessary and detracted from the elegance of the theory, so he threw it out. But if it is nonzero, then it would explain the acceleration that we observe. The other way for this to happen is if vacuum itself has intrinsic energy. If you're familiar with elementary thermodynamics, then you can easily show that expanding a volume of vacuum under this condition implies a negative pressure. This encourages further expansion, and hence explains dark energy. Vacuum energy can be provided by the postulated Higgs Boson, which would fit within our current view of particle physics.

String theory does indeed provide many alternate explanations for the dark matter and dark energy. But string theory has yet to make any concrete predictions, and hence has yet to gain any real credibility with the general physics community.

Answer 3

> Dark matter and energy seem to be very vague and convienantly make-shift to me. A blanket thrown over the short-commings of our current understanding of gravity.

Even scientists will agree with this.

Answer 4

I agree dark matter and energy seem to be very contrived. Just as Ptolemy had his silly epicycles upon epicycles to try to make observations fit into existing theories, modern scientists may be doing the same thing. Then again, I think Superstring theory is the worst contrivance of all.

So I dunno, wake me up in 100 years.

Answer 5

for all intense purposus the moon is dark matter dont forget the distance we are from the observation just cause you see alot of somthing that dosent shine like a star dosent mean its a magical force of nature.

Answer 6

The concept of a theory is where we start to unravel things that we have observed but do not understand. Vague and makeshift, are words we could utilize, just as tendrils in higher dimensional states are terms that we can use. But they start out as ideas that we work on and have peer reviewed as we make progress. Following is a copy of the enclosed site for further consideration.

As if it weren't strange enough that the cosmos is loaded with invisible and elusive matter, a new theory has the stuff wandering through the early universe like a drunken sailor.

The idea is a serious attempt to examine dark matter -- which is far more prevalent than normal matter -- by modeling its behavior, despite the troubling fact that no one knows what it actually is. The result is an animation showing how thousands of relatively small and invisible dark matter galaxies might have developed and still reside in the vicinity of our own Milky Way.
Chung-Pei Ma, an astronomer at the University of California, Berkeley, unveiled the new theory here last week at a meeting of the American Physical Society. Ma envisions dark matter particles behaving like bits of dust bounced around by water molecules in a microscopic process called Brownian motion.
Brownian motion was discovered in 1827 by botanist Robert Brown, who noticed a pollen grain moving erratically for unseen reasons under his microscope. Einstein later figured out that molecules were bouncing randomly off the pollen. The concept was applied decades ago to better understand the behavior of stars in dense clusters. Simulated particles of dark matter wander like drunken sailors but finally come together in these five panels. However, in addition to a primary galaxy, several significant satellite knots of dark matter result.
Modeling the invisible
Scientist suspect the bulk of dark matter involves tiny particles they've yet to detect. The two leading candidates are called axions and neutralinos. Whatever they are, they are known to interact gravitationally with regular matter, because observable matter can't account for the speed with which stars move around galactic centers.

Dark matter particles appear not to interact with electromagnetic forces, however. They don't make or reflect light, which explains why they can't be seen.
"It has to be some kind of exotic particle, something we can't touch," Ma said.
Until recently, scientists assumed dark matter was distributed evenly in a massive halo around each galaxy. Not quite true, Ma and others have come to believe. The halos are there, but so possibly are thousands of clumps that can be thought of as dark, satellite galaxies, several researchers have suggested in recent years. One idea for along these lines was put forth in 2001 by a team led by Neil Trentham at the University of Cambridge. Trentham said that for every normal, star-filled galaxy, there might be 100 that contain primarily stuff we can't see.
Dark matter satellite galaxies -- if they exist -- cannot be detected by conventional telescopes because they don't contain enough normal matter to fuel star birth.
Ma and Bertschinger let millions of hypothetical dark matter particles interact over billions of years in a computer model governed by gravity. Many of the particles coalesce into central clumps as massive as billions of suns, a neat fit with expectations for the process that would build a normal galaxy.
But thousands of dark galaxies develop in the simulation, too, each containing masses equal to several million suns.
"We then realized that the motion of dark matter can also be described statistically by a similar equation used for the Brownian motion," Ma told SPACE.com. "This equation is very different from Newton's law [of gravity] used in the computer model. This doesn't mean Newton's law is not applicable -- it means the new equation that we found provides a new language for describing how dark matter clumps."
Finding dark matter
Dark matter makes up about 23 percent of the universe's mass-energy budget. Normal matter, the stuff of stars, planets and people, contributes just 4 percent. (The rest of the universe is driven by an even more mysterious thing called dark energy.)
A small portion of dark matter has already been identified and is no longer mysterious. Tiny particles called neutrinos, once thought to be massless, are now known to make up a sprinkling of the total dark matter column of the budget. Cold dead stars, recently found to be plentiful, also contribute modestly to this accounting.
If dark satellite galaxies exist, astronomers should be able to detect some of them. Their gravity would bend light traveling toward Earth from more distant objects, distorting and possibly magnifying them. This so-called gravitational lensing effect is used already to study distant objects by peering through and around visible, intervening galaxies or galaxy clusters.
Finding and cataloguing these dark matter galaxies would help researchers understand what they're made of.
"Different dark matter models [for material that is cold or warm] predict different number of these dark galaxies," Ma said. "So if we can estimate the number and masses of these galaxies, it can constrain the nature of dark matter."
Saul Perlmutter of the Lawrence Berkeley National Laboratory, speaking at the same meeting of physicists, said knowledge of dark matter has come a long way since the first strong hints of it emerged in the 1970s. Researchers no longer wrestle with whether it exists or how much there is but instead can focus on its properties, Perlmutter said.