dark matter into "white" (visible) matter?
396678
first of all, what u consider as dark matter is wrong. dark matter is not some hi-fi stuff which is highly radioactive or has some special properties. its just ordinary matter which cant be seen. secondly to ur question.. the outer limit of a black hole is called schwarzchild radius. when any matter approaches this limit, it cant escape whatsoever. ok, now our matter is in the black hole. first of all, 50% of the mass of the material gets converted into x-rays and other high energy radiation. of the remaining half, some part is used up in the fusion process, while the remaning part is used up in the expansion of the black hole. \nand because black hole is just an ordinary star with extraordinary high density, there is no such thing as a whilte hole. if u meant to say something like blackhole made up of antimatter which attracts matter and mutually anhilates, then may be ur question (2) makes sense.
1004125
I would like to to add a few words to a great input other people have already provided.\n\nIn Astronomy, as in all sciences, one can detect an object in one of two ways: either by observing it directly, or observing the effect that it has on other, more easily observed, objects. \nIt's always been known that there was matter in the night sky that we couldn't really directly see. When astronomers use telescopes, or even radio telescopes, they can only see objects which emit light or radio waves. Not all of the matter in the Universe does this - for instance, we wouldn't be able to see planets like our own, because they would be too dim to see. \nAll the mass of of all the planets in our solar system, though, is significantly less than one percent of the Sun's mass. So worrying about matter that didn't shine - non-luminous matter - wasn't of great concern. \nThe first evidence: Clusters of Galaxies The first evidence that there was a significant amount of matter that we couldn't readily see was in investigating clusters of galaxies, which are simply aggregates of a few hundred to a few thousand clusters otherwise isolated in space.\nWhat is Dark matter? This still is an open question.  There are many possibilities, and nobody really knows much about this yet.  Here are a few of the many published suggestions, which are being currently hunted for by experimentalists all over the world.  Remember, you need at least one baryonic candidate and one non-baryonic candidate to make everything work out, so there may be more than one correct choice among the possibilities given here.\nThe baryons are a family of subatomic particles including the proton and the neutron (collectively called nucleons), as well as a number of unstable, heavier particles (called hyperons). The term "baryon" is derived from the Greek barys, meaning "heavy," as they are heavier than the other main groups of particles. http://en.wikipedia.org/wiki/Baryon \n•Normal matter which has so far eluded our gaze, such as: \n dark galaxies \n brown dwarfs \n planetary material (rock, dust, etc.) \n•Massive Standard Model neutrinos.  If any of the neutrinos are massive, then this could be the missing mass.  On the other hand, if they are too heavy, as the purported 17 keV neutrino would have been, massive neutrinos create almost as many problems as they solve in this regard. \n•Exotica (See the Particle Zoo FAQ entry for some details. http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/particle_zoo.html) \n\nHere are a wew references \nWhat is the Universe Made Of? http://map.gsfc.nasa.gov/m_uni/uni_101matter.html \nCosmic Hide and Seek http://www.eclipse.net/~cmmiller/DM/ \n\nDark Matter, Cosmology, and Large-Scale Structure of the Universe http://www.astro.queensu.ca/~dursi/dm-tutorial/dm1.html \n\nExperiment\nExperiment with simulation of cluster of galaxies  http://www.astro.queensu.ca/~dursi/dm-tutorial/cluster-sim.html \n\nWhat is dark matter? http://math.ucr.edu/home/baez/physics/Relativity/GR/dark_matter.html
155835
The problem is to tabulate the total mass of the Universe, a realy BIG problem.  There may be a lot of undetected dark matter in the universe that would shift calculations of the Gravitational Constant that will determine the fate of the Universe.  It is like trying to count the mushrooms in a totally blacked out cellar while blindfolded, or even much harder.  Progress is being made as the limits of the Universe are being explored by every means possible, especially by use of the human brain.
682859
If you could find a gas that had a semi-stable quasistate that when excited would release a photon with a wavelength corresponding to "black", then yes.  However, I don't know exactly what band that would be.  The closest you'd be able to get to black would be a dark ultraviolet, or if you could overlap in phase multiple color lasers which could possibly (but unlikely) add together to make the appearance of black.  Most likely, you're out of luck.
773398
Gosh.  A sensible question, and you have to put up with fourteen completely dumb-cluck answers until one that is actually CORRECT.  The number of elementary particles in the universe is quite a modest number, and well-reasoned estimates of around 10^80 give or take a factor of 10 have been around for nearly a century.\n\nMost of the Universe is hydrogen, so troothskr's 2 x 10^79 hydrogen atoms converts to 4 x 10^79 particles.  Adding photons, neutrinos, and dark matter, it is still unlikely to exceed 10^81.
452314
i'll have to think about this.  if a white dwarf acquires additional mass it may create a surface flash of an explosive nuclear reaction and remove some of the white dwarf (nova) or it may build up without exploding increasing the mass of the white dwarf until it becomes a type ia supernova.  i'm not sure, but this question may be asking for 'black hole'.\n\ncan you rephrase the question?\ndo you have any more homework tonight?
752622
Dark matter is matter (the substances which make up physical objects) that does not emit or reflect enough electromagnetic radiation to be directly dected, but its prescence can be assumed by gravitation effects from surrounding physical objects. The composition of dark matter is currently unknown, but current evidence suggests that it is primarily made up of new elementary particles which are collectively being called nonbaryonic dark matter.\nDark matter is though to make up 25% of the universe. \n\nDark energy is a hypothetical form of energy that flows throughout space containing larges amounts of negative pressure and is used to account for the significant amount of missing mass in the known universe. Very little is known about dark energy but it is thought to make up 70% of the universe.
609227
I'm anxious to hear if any scientists have an answer to this question.  To me, it sounds like you're asking "Who initiated the Big Bang?" or "Why does gravity cause matter to be attracted to other matter?"  It seems to me like the question of "Why?" neutrons have neutral charges is kind of a God question.
589672
Good answer Azreal! Scientists in Australia have actually transported light matter across the laboratory in the last year though....hey its a start!
619512
This conversion is done daily at particle accelerators. The problem is that it is exceedingly difficult to produce much matter this way since anti-matter is always produced at the same time and because the energies needed are huge. So you will never seea hunk of matter that was produced this way, you can see the tracks of the particles that have been.
954004
No, not at all.\n\nProcesses in perfectly stationary nuclei turn mass into energy. For instance, the energy an emitted alpha particle has in alpha decay from a staionary nucleus is reflected by a tiny fall in mass of the nucleus.\n\nConversely, as you accelerate a particle towards the speed of light, more and more of the energy you give to the particle gets converted to mass. In fact, you can never get the particle to the speed of light - its mass will go to infinity first. This is quite measurable in a particle accelerator.
273384
Those photographs are not at all what you would see with the naked eye- even if you were in a spacecraft nearby.  The pictures are "artificially colored composites" using different colors in the human visual spectrum to represent the different gasses reflecting invisible light frequencies or impossibly subtle detail.\n\nFor a detailed explanation of color in astronomical photos, check out the link below to the Hubble Space Telescope FAQ's.\n\n++++++++\nAnd in response to a few snyde remarks from the peanut gallery, here is a direct quote from hubblesite.org:\n\n"Taking color pictures with the Hubble Space Telescope is much more complex than taking color pictures with a traditional camera. For one thing, Hubble doesn't use color film — in fact, it doesn't use film at all. Rather, its cameras record light from the universe with special electronic detectors. These detectors produce images of the cosmos not in color, but in shades of black and white.\n\nFinished color images are actually combinations of two or more black-and-white exposures to which color has been added during image processing.\n\nThe colors in Hubble images, which are assigned for various reasons, aren't always what we'd see if we were able to visit the imaged objects in a spacecraft. We often use color as a tool, whether it is to enhance an object's detail or to visualize what ordinarily could never be seen by the human eye."\n\nAny other comments?
535169
Matter and Anti-Matter
529002
The obvious answer is black holes. But other kinds are non reflective nebulae and dark matter.
380500
It's the matter in galaxies that provides enough gravitational force to prevent them from being flung apart by their angular momentum.  It's called dark because we can't see it
47984
Matter that is in space but is not visible to us because it emits no radiation by which to observe it. The motion of stars around the centers of their galaxies implies that about 90% of the matter in a typical galaxy is dark. Physicists speculate that there is also dark matter between the galaxies but this is harder to verify.\nhttp://pdg.web.cern.ch/pdg/cpep/glossary.html\n\nMatter that does not emit enough light or other radiation to be observed directly. Most of the matter in the universe is believed to be of this type. Cold dark matter had a low velocity compared to the speed of light during the epoch of recombination. An example would be elementary particles with mass about equal to that of a proton or higher. Hot dark matter had a high velocity (near the speed of light) during the epoch of recombination. An example would be light elementary particles.\nhttp://www.nap.edu/readingroom/books/cosmology/glossary.html\nIn cosmology, dark matter consists of matter particles that cannot be detected by their emitted radiation but whose presence can be inferred from gravitational effects on visible matter such as stars and galaxies. Estimates of the amount of matter in the galaxies, based on gravitational effects, consistently suggest that there is far more matter than is directly observable. ...\nhttp://en.wikipedia.org/wiki/Dark_matter
260891
Well, people have been spotting and reporting MACHOs for a long time, simply by how they affect light that passes through them.\n\nI believe that WIMPs, if they exist, would be the source for more of the energy density requirements to keep omega at ~1. MACHOs only exist within galactic halos, and are aggregated. WIMPs, on the other hand, are likely to be evenly distriubuted within and between galaxies, acounting for their rotation and their movements relative to one another. I think the lack of information about WIMPs is simply due to the limits of our technology in being able to detect particles that only respond to gravitational fields and require a lot of energy to make because they are heavy. If a particle does not interact with any force at all except gravity, it is likely to be a long time before we ever prove that it exists.\n\nI also think that the fermionic superpartner to the Higgs boson is a good candidate for the WIMP, and it is likely that the debate on the existence of supersymmetric particles will be put to rest as soon as those giant particle accelerators are built in Europe. I think the one is supposed to be online in 2008.