metoclopramid 20 ml metoclopramid gyogyszer read here 'Science mystified by the universe'
23 Sep 2007, 0150 hrs IST ,AFP
AMSTERDAM: Most of the universe - 96%, to be exact - is made of dark matter and energy whose composition we simply do not fathom, a Nobel laureate told physicists gathered this week to explore the intersection of the infinitely small and the infinitely large.
"We think we understand the universe, but we only understand four per cent of everything," said James Watson Cronin, who won the 1980 Nobel for physics by proving that certain subatomic reactions escape the laws of fundamental symmetry.
According the most recent models, he said, 73% of cosmic energy seems to consist of dark energy and 23% of dark matter, the pervasive but unidentified stuff that holds the universe together and accelerates its expansion. The remaining four per cent consists of so-called normal matter such as atoms and molecules.
Dark matter cannot be detected directly, because it does not emit or reflect light or radiation - or not enough to be picked up by available tools. But its presence can be inferred because its gravitational force deflects light from distant galaxies.
"We have an idea as to its parameters, but we still don't know what dark matter is made of," said Stavros Katsanevas, head of Frances national institute for nuclear and particle physics.
Most physicist attending the conference here on astroparticle physics think the basic ingredient is probably some as-yet undiscovered elementary particle, a relic of the "Big Bang" that created the Universe around 13 billion years ago.
The favoured candidate is the neutralino, a "supersymmetric" particle whose existence has yet to be proven. Over the next decade, explained Katsanevas, scientists will be tackling three big questions besides dark matter: the origin of cosmic rays, the existence of gravitational waves, and the mass of neutrinos, which have provided the first solid evidence of phenomena beyond what is called the Standard Model of particle physics.
Gravitational waves are often described as "ripples" in space-time. Just as a boat produces waves in the water, moving masses like stars or black holes produce gravitational waves in the fabric of space-time. Isolating gravitational waves - negligible at microscopic scales, and thus currently undetectable - would confirm one of the central predictions of Einsteins theory of relativity.
It could also be harnessed as a cosmological probe, especially to test the evolution of dark energy. Neutrinos, one of the universes fundamental particles, are also one of the least understood and hardest to detect. Travelling close to the speed of light, they lack any electric charge and can pass through ordinary matter almost undisturbed.
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