Презентация - "Презентация на тему: Dark Matter (Темная материя)"

DARK MATTER
Armashura Anita PKS-21

Dark matter is…
Dark matter is a component of the universe, a mysterious non-luminous substance making up the vast majority of matter in the universe.
It emits no light or energy and thus cannot be detected by current instruments.
Dark matter makes up 30 percent of the matter-energy composition of the universe; the rest is dark energy (65 percent) and “ordinary” visible matter (5 percent).

Discovery
In the 1930s, a Swiss astronomer named Fritz Zwicky, while studying galaxies in the Coma cluster, noticed that a few galaxies were moving at a very high speed. In fact, they were so quick that Zwicky felt that they could no longer remain gravitationally bound and would rip off.
He surmised that around 100 more matter would be needed to justify the exorbitant pace of these receding galaxies. He was suspicious of this mysterious matter, but was sure that it was not visible like ordinary matter. Thus, he called it dark matter.

The dark history of the universe
Just like the regular stuff, dark matter is believed to have been created in the Big Bang – or as one theory suggests, even before it, during a period of cosmological inflation. Either way, the structure we see out in the cosmos today would be very different without dark matter.

Why do we think dark matter exists?
Scientists are confident it exists because of the gravitational effects it appears to have on galaxies and galaxy clusters.
It could also explain certain optical illusions that astronomers see in the deep universe.

Dark energy vs Dark matter
Dark matter and dark energy are the yin and yang of the cosmos. Dark matter produces an attractive force (gravity), while dark energy produces a repulsive force (antigravity).
Dark energy is why our universe is expanding. In fact, in 1998, astronomers studying distant supernovae were shocked to learn that, around 7.5 billion years after the Big Bang, the universe began expanding faster.

The big hunt
Different types of experiments are hunting for different theoretical dark matter particles. Perhaps the most famous experiments are those being conducted by CERN, at the Large Hadron Collider. There, scientists are looking for dark matter by trying to create it.

Another methodic
While the LHC is searching in one part of the spectrum of possibility, other experiments are trying to detect it in different ways. 
For example, direct detection experiments. So the idea is you take a suitably large detector, you put it in a very quiet environment which is free from background influences that could mimic your dark matter signal, and then you just watch the detector and you wait for the nucleus of an atom to suddenly zip off for no apparent reason. The idea is that a dark matter particle has come along, hit the nucleus and caused it to zip off.

Is dark matter necessary?
Some astronomers have tried to negate the need the existence of dark matter altogether. They postulate something called Modified Newtonian dynamics (MOND). The idea behind this is that gravity behaves differently over long distances from what it does locally. This difference of behavior would explain phenomena such as galaxy rotation curves which we attribute to dark matter.

Null doesn’t mean void
Sadly enough, all of the experiments have either returned null results on dark matter, or are purely theoretical for now. But not getting a signal doesn’t make an experiment a total washout – null results are important to help whittle away at that gigantic possibility space.
Each test searches for dark matter candidates within a certain mass range and with certain properties, and as we cross them off the list we’re getting ever closer to the truth. And it helps that many of the experiments are getting upgrades in the future that will make them ever-more sensitive.