what is dark matter?

Question

tell me kid 13 simplefiy

Answer 1

i have dark matter but it is only visible to females sorry...

Answer 2

First of all, not much is known about dark matter. It is still in the realm of imponderables.I will put the matter in very simple words. Why is it called dark matter? This is because strangely, it does not reflect light or any form of electromagnetic radiation. How much of dark matter? Acording to current estimates, it is indeed amazing that, Dark matter is 95% of all material in the universe. It implies what ever satellites, planets, stars. galaxies, nebulae ....and so on we know it all amounts to only 5% of matter.It is also a conjecture that dark matter is responsible to hold the universe together and restricts the going apart of universe[we know every thing is flying away from each other as per Hubble]

Answer 3

You asked: simply... All above are fine, but not very simple.
We know a lot about the Universe. We have established formulas that explain how the Universe works. Pretty well, in fact, for everything!
So we apply our formulas to the Universe we observe.
And they don't work!
Something is wrong.
According to our formulas, there SHOULD be much more matter in the Universe than what we observe.
So, we have two choices:
- We admit that our formulas are not correct, and we try to develop a theory that works, or
- If our formulas are correct, we need more matter than the matter we see. So we "invent" a matter that fits our formulas. We call it "Dark matter" because we don't see it.
Where are we now?
We search for the dark matter, because we don't see it.
We try to improve our formulas.
What is the correct way?
We don't know! (Yet)
Sorry!

Answer 4

That is what they call the unknown mass that causes galaxy rotation to be wrong. The rotation of galaxies implies there is a lot of mass out there, more than can be accounted for by all the visible stars and dust and gas clouds. Nobody knows what it is or if it even exists. There could be another explanation for the strange motions of galaxies, but nobody have though of one yet.

Answer 5

when scientists observed other galaxies they discovered that their outer arms rotate too fast to explain this motion with current theories.
So they put 'dark matter' as a theoretical mass into the calculations to make it fit. (not to be confused with normal matter which cannot be directly seen and not to be confused with 'dark energy')

at present scientists are working hard to explain the universe with a 'Grand Unified Theory' but it seems that gravitation does not really fit into the picture we seem to have about our universe.

So from time to time its a usual process for them to 'invent' something to work with that in calculations.
if they would have invented the COKE-factor to make it fit, then we would have 'sticky matter' instead ;-)

Answer 6

Matter you can´t see.

Scientists think, because of various equations and anomolies in space that there isn´t enough matter, so they dreamed up Dark Matter, matter which is there but cannot be seen or measured.

A load of crap if you ask me, instead of considering that there theories might be wrong, the dream something up to fit.

Answer 7

Unknown as of yet...we only know of it because of the gravitational effects it makes on observable matter.

Answer 8

In astrophysics, dark matter is matter that does not emit or reflect enough electromagnetic radiation (such as light, X-rays and so on) to be detected directly, but whose presence may be inferred from its gravitational effects on visible matter. Among the observed phenomena consistent with the existence of dark matter are the rotational speeds of galaxies and orbital velocities of galaxies in clusters, gravitational lensing of background objects by galaxy clusters such as the Bullet cluster, and the temperature distribution of hot gas in galaxies and clusters of galaxies. Dark matter also plays a central role in structure formation and Big Bang nucleosynthesis, and has measurable effects on the anisotropy of the cosmic microwave background. All these lines of evidence suggest that galaxies, clusters of galaxies, and the universe as a whole contain far more matter than is directly observable, indicating that the remainder is dark.

The composition of dark matter is unknown, but may include new elementary particles such as WIMPs and axions, ordinary and heavy neutrinos, dwarf stars and planets collectively called MACHOs, and clouds of nonluminous gas. Current evidence favors models in which the primary component of dark matter is new elementary particles, collectively called nonbaryonic dark matter.

The dark matter component has vastly more mass than the "visible" component of the universe.[1] At present, the density of ordinary baryons and radiation in the universe is estimated to be equivalent to about one hydrogen atom per cubic metre of space. Only about 4% of the total energy density in the universe (as inferred from gravitational effects) can be seen directly. About 22% is thought to be composed of dark matter. The remaining 74% is thought to consist of dark energy, an even stranger component, distributed diffusely in space.[2] Some hard-to-detect baryonic matter (see baryonic dark matter) makes a contribution to dark matter, but constitutes only a small portion.[3][4] Determining the nature of this missing mass is one of the most important problems in modern cosmology and particle physics. It has been noted that the names "dark matter" and "dark energy" serve mainly as expressions of our ignorance, much as the marking of early maps with terra incognita.[2]
A proposed alternative to physical dark matter particles has been to suppose that the observed inconsistencies are due to an incomplete understanding of gravitation. To explain the observations, the gravitational force has to become stronger than the Newtonian approximation at great distances or in weak fields. One of the proposed models is Modified Newtonian Dynamics (MOND), which corrects Newton's laws at small acceleration. However, constructing a relativistic MOND theory has been troublesome, and it is not clear how the theory can be reconciled with gravitational lensing measurements of the deflection of light around galaxies. The leading relativistic MOND theory, proposed by Jacob Bekenstein in 2004 is called TeVeS for Tensor-Vector-Scalar and solves many of the problems of earlier attempts. A similar theory proposed by John W. Moffatt is Nonsymmetric Gravitational Theory.

In August 2006, a study of colliding galaxy clusters claimed to show that even in a modified gravity hypothesis, the majority of the mass must be some form of dark matter by demonstrating that when regular matter is "swept away" from a cluster, the gravitational effects of dark matter (which is thought to be non-interacting aside from its gravitational effect) remain.[17] However, a study claims that TeVeS may be able to produce the observed effect but needs the majority of the mass to be dark matter, possibly in the form of ordinary neutrinos.[18] Also Nonsymmetric Gravitational Theory has been claimed to qualitatively fit the observations without needing exotic dark matter.[19]

In another class of theories one attempts to reconcile gravitation with quantum mechanics and obtains corrections to the conventional gravitational interaction. In scalar-tensor theories, scalar fields like the Higgs field couples to the curvature given through the Riemann tensor or its traces. In many of such theories, the scalar field equals the inflaton field, which is needed to explain the inflation of the universe after the Big Bang, as the dominating factor of the quintessence or Dark Energy. Using an approach based on the exact renormalization group, M. Reuter and H. Weyer have shown[20] that Newton's constant and the cosmological constant can be scalar functions on spacetime if one associates RG scales to the points of spacetime





The first to provide evidence and infer the existence of a phenomenon that has come to be called "dark matter" was Swiss astrophysicist Fritz Zwicky, of the California Institute of Technology (Caltech) in 1933.[5] He applied the virial theorem to the Coma cluster of galaxies and obtained evidence of unseen mass. Zwicky estimated the cluster's total mass based on the motions of galaxies near its edge. When he compared this mass estimate to one based on the number of galaxies and total brightness of the cluster, he found that there was about 400 times more mass than expected. The gravity of the visible galaxies in the cluster would be far too small for such fast orbits, so something extra was required. This is known as the "missing mass problem". Based on these conclusions, Zwicky inferred that there must be some non-visible form of matter which would provide enough of the mass and gravity to hold the cluster together.

Much of the evidence for dark matter comes from the study of the motions of galaxies. Many of these appear to be fairly uniform, so by the virial theorem the total kinetic energy should be half the total gravitational binding energy of the galaxies. Experimentally, however, the total kinetic energy is found to be much greater: in particular, assuming the gravitational mass is due to only the visible matter of the galaxy, stars far from the center of galaxies have much higher velocities than predicted by the virial theorem. Galactic rotation curves, which illustrate the velocity of rotation versus the distance from the galactic center, cannot be explained by only the visible matter. Assuming that the visible material makes up only a small part of the cluster is the most straightforward way of accounting for this. Galaxies show signs of being composed largely of a roughly spherical halo of dark matter with the visible matter concentrated in a disc at the center. Low surface brightness dwarf galaxies are important sources of information for studying dark matter, as they have an uncommonly low ratio of visible matter to dark matter, and have few bright stars at the center which impair observations of the rotation curve of outlying stars.

According to results published in August 2006, dark matter has been observed separate from ordinary matter[6][7] through measurements of the Bullet Cluster, actually two nearby clusters of galaxies that collided about 150 million years ago.[8] Researchers analyzed the effects of gravitational lensing to determine total mass distribution in the pair and compared that to X-ray maps of hot gases, thought to constitute the large majority of ordinary matter in the clusters. The hot gases interacted during the collision and remain closer to the center. The individual galaxies and the dark matter did not interact and are further from the center.