Wednesday, January 11, 2012

Scientists map dark matter around us, provides clue about existence of dark energy

Dark matter is matter that we know is there, but we cannot actually detect. Hence the name. We deduce existence of dark matter by its effect on gravity. There is a big gap between the required gravitational force to hold stars and planets in galaxies together, and the amount of matter we can detect. Scientists from the University of Edinburgh mapped the locations of dark matter in the universe. The map, in turn, tells us something about where we may be able to find something called dark energy. This is equally undetectable, and has an anti-gravity effect, thus opposing the effect of dark matter.

Dark matter map 
To create a graphical view of the dark matter that is present around us, scientists observed about 10 million galaxies, with an average distance of 6 billion light years. In the universe, there is something called space-time, in which time is no longer detached from space. Instead, they function as one entity. Gravity is known to bend space-time, which makes light appear bend and warped. This effect, called gravitational lensing, can be used to calculate where matter is located. If we cannot see it, it must be because it's dark matter. At the University of Edinburgh, they created the largest map of dark matter to date.
Imagine bending of space-time is best visualized by thinking of the universe as a sheet.
Flocks, connected by small filaments
The map shows small flocks of dark matter, which are connected to each other by thin thread-like filaments. Though the map does not give a spectacular look at what our universe looks like with dark matter in it, it did match with computer predictions. It also told the researchers that the concept of dark energy is needed to account for what the map tells us. With just ordinary matter and dark matter, we may be able to explain all of the gravitational effects that we can observe, such as the aforementioned gravitational lensing, but it does not tell us why the universe is the way it is.
Dark matter, as seen in four directions. Small square represents the previous biggest dark matter map, and shows the moon, which scales.
Dark energy
Because a different research group, from Chicago, figured out the absolute distances to the observed galaxies, the map can tell us something about the properties of dark energy. Because the universe is expanding, galaxies move away from us. We need the concept of dark energy to explain this, because matter, be it dark or visible, actually pulls us together. Just as dark matter, dark energy is something we are unable to detect, but we know is there, because of the anti-gravity effects that cause the expansion of the universe. This is sort of dark matter in reverse. Without it, the universe would collapse on itself. By having dark matter mapped out, we have a tool to start searching dark energy more effectively. The Nobel Prize of physics of 2011 was awarded to dark energy research. An earlier study on dark matter revealed that whatever it may be, its particles must be very heavy.

No comments:

Post a Comment