Monday, January 14, 2008

298)Invisible Dark Matter, making up a quarter of the contents of the Universe, uncovered; Quotes of Aga Khan IV.


Where the shadows lie

Jan 10th 2008
From The Economist print edition

A rare double ring illuminates the dark matter of the early universe

EINSTEIN himself reckoned that, although they must exist, they would be impossible to spot. Yet the great man was mistaken. Astronomers have seen “Einstein rings”, formed when light from a distant galaxy is bent by the presence of a nearer massive object, usually another galaxy, that lies directly in its path to Earth. Now they have discovered something even rarer: a double Einstein ring formed by two such intervening objects. The resulting image casts light, as it were, on the question of how “dark matter” was distributed in the early universe. The exact nature of this type of matter is unknown, but it seems to make up a quarter of the contents of the universe. The latest result suggests it is more widely spread than the visible matter that is clumped together to form galaxies, with implications for how those galaxies formed.

In his general theory of relativity, Einstein proposed that space and time are distorted by the presence of massive objects. Light, which normally and famously travels in straight lines, thus appears to follow a curved path when it passes near a heavy thing such as a galaxy. This effect is known as gravitational lensing, and the heavy object that causes it as a gravitational lens. If source, lens and observer are exactly aligned, the result is a luminous ring that appears to surround the lens.

Einstein despaired of ever finding a source and a lens precisely aligned with an observer on Earth and thought that, even if they did exist, telescopes would never be powerful enough to see the resulting ring. Nevertheless, the first such ring was observed in 1987. Now, a group of astronomers led by Tommaso Treu of the University of California, Santa Barbara, have seen two concentric rings.

Dr Treu and his colleagues first identified the most promising places to look for Einstein rings—parts of the sky where two or more clusters of galaxies can be seen one behind the other. They then searched these areas for galaxies that appeared to have two different spectrums, suggesting that what looked like a single object actually had another one sitting behind it. Having found a promising one in the constellation Leo, they turned the Hubble space telescope on it.

As they hoped, the image of the first galaxy, which lies about 2 billion light years away, was surrounded by a ring of light from the second one, which lies 6 billion light years away. To their surprise, however, they spotted a second ring, formed by light from a third galaxy 11 billion light years away.

This discovery, which Dr Treu presented to a meeting of the American Astronomical Society held in Austin, Texas, on January 10th, represents more than an unusual and pretty stamp for the astronomers' collection. The diameter of the rings depends not only on the distance to the galaxies that caused them but also on the masses of those galaxies. The more massive they are, the more the light is bent.

Dr Treu and his colleagues compared the mass the rings suggested was present with what they could actually see. They were thus able to study the distribution of dark matter. Earlier work had suggested that dark matter seeded the early universe, acting as nuclei around which visible matter clumped into galaxies. But Dr Treu found that the dark matter extended further than the visible matter, forming a halo around it. If that turns out to be true elsewhere, it makes galaxy formation harder to explain.

Having a double ring could also help explain dark energy, a mysterious force that is thought to pervade the universe, causing its expansion to accelerate. The outer ring is created by a galaxy that is some 5 billion years older than the inner one. If further double rings are discovered, and Dr Treu is optimistic that they will be, it should be possible to tell whether the amount of dark energy around has remained constant, or has changed over the course of time.

Einstein proposed the existence of something he called the cosmological constant, to fulfil the role now assigned to dark energy. As its name suggests, it was not expected to vary as the universe aged. But if it did, it would not be the first time that Einstein erred.

Quotes of Aga Khan IV:

"......The Quran tells us that signs of Allah’s Sovereignty are found in the contemplation of His Creation - in the heavens and the earth, the night and the day, the clouds and the seas, the winds and the waters...."(Aga Khan IV, Kampala, Uganda, August 22 2007)

"The Qur’an itself repeatedly recommends Muslims to become better educated in order better to understand God’s creation"(Closing Address by His Highness Aga Khan IV at the "Musée-Musées" Round Table Louvre Museum, Paris, France, October 17th 2007)

“Muslims believe in an all-encompassing unit of man and nature. To them there is no fundamental division between the spiritual and the material while the whole world, whether it be the earth, sea or air, or the living creatures that inhabit them, is an expression of God’s creation.”(Aga Khan IV, Charlottesville, Virginia, USA, 13 April 1984)

"Science is a wonderful, powerful tool and research budgets are essential. But Science is only the beginning in the new age we are entering. Islam does not perceive the world as two seperate domains of mind and spirit, science and belief. Science and the search for knowledge are an expression of man's designated role in the universe, but they do not define that role totally....."(Aga Khan IV, McMaster University Convocation, Hamilton, Ontario, Canada, May 15th 1987).

Easy Nash aka easynash

The Qur'an itself repeatedly recommends Muslims to become better educated in order better to understand God's creation: Aga Khan IV(2007)
The Quran tells us that signs of Allah's Sovereignty are found in the contemplation of His Creation: Aga Khan IV(2007)
This notion of the capacity of the human intellect to understand and to admire the creation of Allah will bring you happiness in your everyday lives: Aga Khan IV(2007)
Islam, eminently logical, placing the greatest emphasis on knowledge, purports to understand God's creation: Aga Khan IV(2006)