Dark matter is believed to be a form of matter thought to account for approximately 85% of the matter in the universe and about 27% of its total mass–energy density or about 2.241×10−27 kg/m3. Its presence is implied in a variety of astrophysical observations, including gravitational effects that cannot be explained by accepted theories of gravity unless more matter is present than can be seen.
For this reason, most experts think that dark matter is abundant in the universe and that it has had a strong influence on its structure and evolution. Dark matter is called dark because it does not appear to interact with the electromagnetic field, which means it does not absorb, reflect or emit electromagnetic radiation, and is therefore difficult to detect.
Theory of Dark matter
The existence of dark matter can be traced back to the pioneering discoveries of Fritz Zwicky and Jan Oort that the motion of galaxies in the Coma cluster, and of nearby stars in our own Galaxy, do not follow the expected motion based on Newton's law of gravity and the observed visible masses.
difference between antimatter and dark matter?
The key is that our universe is mostly made of regular matter, so antimatter cannot stick around for very long. Very soon after antimatter is created, it bumps into regular matter and gets destroyed again. ... Dark matter is matter that does not interact electromagnetically, and therefore cannot be seen using light.
Astronomers and cosmologists think around 25 per cent of our universe is made of something called dark matter, and the remainder—around 70 per cent—is what’s known as dark energy. Dark matter doesn’t interact with light, so we can’t see it. The only reason we know there’s something out there beyond what we can directly see is because it interacts with gravity.
Dark matter doesn't interact with light, so we can't see it.
The work of many astronomers contributed to our current understanding of dark matter. In 1933, the astronomer Fritz Zwicky observed that galaxies within the Coma cluster were moving faster than expected; speeds which should have caused them to leave the cluster rather than being held in by its gravitational pull. Some years later, Australian astronomer Ken Freeman noticed gas was moving around galaxies at greater and greater distances at the same speed, despite there being little material at these large distances. Vera Rubin saw the same thing with stars on the edges of many galaxies.
These observations indicated that the gravitational fields in the galaxies were greater than expected based on their amount of visible mass—the large gravitational pull they were exerting could only be explained by the presence of some sort of additional mass. The best guess as to where this mass comes from is that it’s some sort of strange exotic particle: dark matter.
No one knows much about this particle, except to be pretty sure it’s something we’ve never encountered here on Earth. It doesn’t interact with light, hence the name ‘dark’ matter, which means that it’s neutral, with no electrical charge. It's also slow moving, being concentrated in galaxies and clusters rather than dispersed evenly throughout space.
Even though we don't know what it is and we can't see it, we do know that dark matter matters.
Comments
Post a Comment