Virtual particles - enough gravity to constitute the dark matter?
346451
There is a very basic problem here. If you do a computation of the energy associated with the virtual particles, you get way, way, WAY more than enough to produce a closed universe. By one estimate, the answer is *at least* 63 orders of magnitude off. This is one of the worst predictions ever made! Clearly something is going on and nobody seems to have a good idea about how to get plausible results from this type of calculation. A *lot* of cancellation has to occur.
397017
You would have to be able to take a base measurement on the number of quarks that is associated with gravity in an area observed and tell over time if there is a gain or loss of quarks from the base measurement.\n\nP.S.\nThere is no way in the world that the current technology can even begin to do this provided that we would have to agree that // universes exist.
258042
Fact.  Sort of.\n\nWhat is a fact is that every single repeatable measurement of large scale mass shows a very large discrepancy between how much dynamical mass is there (that is to say how much gravity says is there), and how much we can account for using every trick we know (and some we don't).\n\nGalaxy rotation, galaxy cluster temperature, WMAP data, you name it, everything we do to measure dynamical mass of very large objects comes back with us missing large amounds of accountable mass.\n\nEither there is some form of "dark matter" or we are encountering some new aspect of Gravity.  Right now Dark Matter is winning out because no one has been able to come up with a new twist on gravity that gets things right.
477879
Well, the one is matter and the other is energy.\n\n=====\n\nIn cosmology, dark matter refers to hypothetical matter particles, of unknown composition, that do not emit or reflect enough electromagnetic radiation to be detected directly, but whose presence can be inferred from gravitational effects on visible matter such as stars and galaxies. The dark matter hypothesis aims to explain several anomalous astronomical observations, such as anomalies in the rotational speed of galaxies (the galaxy rotation problem). Estimates of the amount of matter present in galaxies, based on gravitational effects, consistently suggest that there is far more matter than is directly observable. The existence of dark matter would also resolve a number of inconsistencies in the Big Bang theory, and is crucial for structure formation.\n\nIf dark matter does exist, it has vastly more mass than the "visible" part of the universe [1]. Only about 4% of the total mass 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, that probably cannot be thought of as ordinary particles. Determining the nature of this missing mass is one of the most important problems in modern cosmology and particle physics. Its urgency is underlined by David B. Cline in a 2003 article in Scientific American, in which he writes: "The terms . . . 'dark matter' and 'dark energy,' serve mainly as expressions of our ignorance." [2]\n\n=====\n\nIn cosmology, dark energy is a hypothetical form of energy which permeates all of space and has strong negative pressure. According to the theory of relativity, the effect of such a negative pressure is qualitatively similar to a force acting in opposition to gravity at large scales. Invoking such an effect is currently the most popular method for explaining recent observations that the universe appears to be expanding at an accelerating rate, as well as accounting for a significant portion of the missing mass in the universe.\n\nTwo proposed forms for dark energy are the cosmological constant, a constant energy density filling space homogeneously, and quintessence, a dynamic field whose energy density can vary in time and space. Distinguishing between the alternatives requires high-precision measurements of the expansion of the universe to understand how the speed of the expansion changes over time. The rate of expansion is parameterized by the cosmological equation of state. Measuring the equation of state of dark energy is one of the biggest efforts in observational cosmology today.\n\nAdding a cosmological constant to the standard theory of cosmology (i.e. the FLRW metric) has led to a model for cosmology known as the Lambda-CDM model. This model agrees closely with established cosmological observations.\n\nThe term dark energy was coined by Michael Turner.\n\n=====\n\nZack,\n\nDark matter is not detectable.  It can't be seen with visible light, or astronomers would see fuzzy halos around galaxies.\n\nDark energy is a force that is causing the expansion of the Universe to accelerate.  Instead of holding the Universe together, dark energy is blowing it apart.
895176
Eather is debunked idea proven to not exist experimentally. Michelson-Morley experiment showed eather can't exists. I think dark matter is really something else. But it comes into play some role in Einstein's struggle to deal with expanding universe which he originally believed was static and unchanging.\n\n\nhttp://en.wikipedia.org/wiki/Michelson-Morley_experiment
877563
The actual origin of gravity is still a mystery to physicists. Yes, everything with mass has gravity, but that doesn't explain where it actually comes from. The current hypothesis is that gravity originates from a hypothetical particle called the "Higgs boson", which hasn't yet been observed. Physicists hope that the Large Hadron Collider at CERN (Switzerland) will be able to detect it soon.
1108157
You should be able to measure all three, in both cases.. limited only by the sensitivity and accuracy of your instruments.\n\nwhen a particle with mass moves past you, or you move past it, the force excerted by gravity between you and the particle changes with distance. Of course you need to have a mass too. and your instruments need to be good enough to distinguish these forces from other gravitational and other kind of forces.\n\nIf a charged particle moves, it produces a magnetic field. this is the same effect as seen in a elecromagned where moving elecrons produce magnetic fields.\n\nif a charged particle moves past you, and you have a detector that is based on charge too, you will notice an increase or decrease in attractive or repulsive force between your detector and the charged particle as the distance between the both changes. again this force is miniscule and is easily confused with other stray forces including the above gravitational ones.
970786
It would seem so.\nMatter/antimatter annihilation (which has been observed many many times both naturally and man made), results in energy, i.e. photons, which, though massless, do have gravitational interactions. That is the point of general relativity (light bends in a gravitational field). It's a long story... 4 years of college majoring in physics and 6 years writing a PhD in high energy physics will clear it all up for you.
1150780
In fact, there is a great deal of evidence showing it is not. What little we know of the dark matter and energy is that they are not composed of baryons. But anti-protons *are* bosons. There are some candidates for the dark matter (axions are a good bet) but anti-matter in the usual sense is ruled out by observation.
707260
The virtual particle that mediates electromagnetism is the photon, which is mass-less. therefore, it will not curve the spacetime it lives in.
75146
There currently is no explanation for dark matter just some guesses based on observations.  Some of the observations are the following: \n\n1.  Gravitational lensing from massive galaxies is stronger than expected based upon the average "visible" mass of many galaixes.\n\n2.  Galactic rotation curves do not follow Keplerian motion at distances far from the center of spiral galaxies which seem to imply that there is unseen matter in a halo around most galaxies.  It has been recently proposed that cetain general relativistic treatments of mass distributions of galaxies could explain rotation curves with out the use of dark matter.  It appears that this latter theory is beginning to gain acceptance (see paper under sources).   \n\nIf dark matter does exist then it is matter that doesn't interact (or weakly) via photons (the electromagnetic force), likely not made of electons, but does interact gravitiational.  Nothing currently is known to have these properties.  Objects like brown dwarfs, black holes and white dwarfs were believed to contribute to dark matter however it has been shown that the space density of these object don't add up to a signifcant amount.  \n\nOther theories include MACHOs (Massive Astrophysical Compact Halo Objects; origin unknown) or the theoretical particles called axions and WIMPs (Weakly Interacting Massive Particles).
891624
i'm not sure how you consider it mathematically unlikely - where's your working for that?\n\nThe theory is that yes, the matter in the universe can from the dense plasma that expanded from the singularity that began the big bang.  Howver, if dark matter theory is to be believed, there is a lot of matter unaccounted for - but it is still likely to have originated from the Big Bang
564206
are you asking about "dark matter"?  dark matter is an unknown kind of matter that only interacts with ordinary matter gravitationally.  about 85 percent of the matter in the universe is dark matter.  swiss astronomer fritz zwicky originated the term 'dark matter'.\n\nread these pages.  they will help.\nhttp://en.wikipedia.org/wiki/Dark_matter\nhttp://map.gsfc.nasa.gov/m_uni.html
706023
All it means is that we don't know everything. We've learned quite a bit in the short time since we developed written language and the scientific method, and the rate of learning is accelerating. We'll learn more in the next 10 years than we've learned in the last 100. We'll probably understand the nature of dark matter in the next 10-20 years, and I would bet long odds that it won't require any supernatural explanation.
1044107
None.  That is the point.  If they exist is not proved, and hypothetical tests to see if they exist are flawed.  \n\nOn your other question of visualizing multiple dimensions, I have a few hints.  Have you read Flatland yet?  Start there, its good, and not overly mathematical.  Multiple dimensions can mean different things to different scientists.  We use them all the time for their mathematical properties.  But mathematics is just a description, the real world is something observable.  In terms of observation, you would not be able to detect a separate dimension by any means pedantic.  We may be able to prove that physical space has more than three dimensions, but that does not mean that those other dimensions are physical space.  Just like time.  Some particle interactions appear to go backward in time briefly.  What if there is more than one time dimension?  \n\nSo the classic three dimensional physical picture of multiple dimensions will always be flawed by the observers expectation of the properties of the unseen dimension.  Which is why we describe those dimensions using 'imaginary' constructions.  Hope this helps a bit.
453562
We don't (as yet) know what dark matter is composed of. It certainly is *not* ordinary matter since it is known not to be composed of baryons (like protons and neutrons). While neutrinos are certainly *part* of the dark matter, there are not enough of them to account for all the dark matter we know exists. Other suggestions are particles called axions, but nothing is certain in this regard.
943536
Currently, dark energy seems to be a "fifth" force that seems to conteract gravity at large distances.\n\nHowever, there could be many more forces that we don't know about. For example, what if every dominant force we know is result of a strong force overpowering a weaker force?\n\nIn the case of "dark energy" and gravity, gravity is just a small fraction stronger than dark energy. So it takes a lot of mass to have a reasonable gravitational field. But like the strong and weak nuclear forces, gravity is only stronger than "dark energy" at relatively short distances. As the distances increase, dark energy overpowers gravity and pushes objects away from each other.\n\nIt's something to think about. Counteracting forces, especially if one of them is dominanting, would be difficult to discern.\n\nBut that's just one example. There could be many others that we just haven't experienced yet. These may be all there are. Scientists are making new discoveries everyday so only time will tell.\n\n~X~