Why can't we find Dark Matter?

Question

If dark matter comprises 25% of the universe's energy and mass total, shouldn't it be easier to find? Is it hard to find because it is....the only word that comes to mind is "Inert"....to interaction with any way we might detect it? Still, as 25% of the universe, wouldn't you expect to bump into a chunk of it now and then?

Thanks.

I guess the key issue is interaction...neutrinos generate heat, but dark matter doesn't. In addition I assume it doesn't bond to itself since I never see a chunk of it when I am walking down the street :-)

Answer 1

The evidence for DM from it's gravity is very strong. It's hard to detect particles of DM for the same reason it's dark ... because it reacts so weakly with regular matter. There are experiments running to detect single rare scattering events from DM particles by watching many atoms for long periods of time with sensitive light detectors. Nothing yet.

Answer 2

Dark matter/energy is more like 90% of the universe's energy and mass. The problem is we can't see it (hence the name dark matter). We just speculate it has to be out there because of the gravitational effects we have observed in the universe (this is also how we can calculate the 90%).

Answer 3

It could involve something like neutrinos. These can zoom through the whole of the earth without being stopped or deflected. If you can't detect something it is not easy to tell if it is there or not.

Answer 4

You're sitting on a chunk of dark matter. It's called the earth.

Answer 5

In astrophysics and cosmology, dark matter refers to hypothetical matter of unknown composition that does not emit or reflect enough electromagnetic radiation to be observed directly, but whose presence can be inferred from gravitational effects on visible matter. According to present observations of structures larger than galaxy-sized as well as Big Bang cosmology, dark matter accounts for the vast majority of mass in the observable universe. Fritz Zwicky used it for the first time to declare the observed phenomena consistent with dark matter observations as 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 galaxy evolution, 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 that which interacts with electromagnetic radiation: the remainder is called the "dark matter component".

The composition of dark matter is unknown, but may include ordinary and heavy neutrinos, recently postulated elementary particles such as WIMPs and axions, astronomical bodies such as 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 non-baryonic 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. Some hard-to-detect baryonic 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".

Answer 6

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Answer 7

Because it doesn't exist....its only speculation.