Monday, October 22, 2012

Big Bang Science

A hundred metres below ground, under the border between France and Switzerland, scientists are travelling back in time to study matter as it was in the first fractions of a second after the beginning of the Universe. They are using the world's largest scientific instrument to help reveal how this primordial matter developed into the building blocks that form the great diversity of the Universe today.
These scientists-many from the UK- are explorers, extending our horizons in time as well as space, in an attempt to answer one of the most fundamental of questions:

Where do we come from?


At CERN, the European laboratory for particle physics near Geneva,
the path of the world's largest particle collider beneath the border
between France and Switzerland.
The observations of astronomers imply that the Universe is still expanding from an infinitely dense and energetic state, after an initial 'hot big bang' some 15 billion years ago. But how did the matter of the present-day Universe evolve from this state? This is one of the major questions that modern research in particle physics seeks to answer. High energy collisions of subatomic particles can take us back in time to the forms of matter that probably existed in the first fractions of a second after the big bang. In this way studying matter at the smallest of scales (subatomic particles) has become inextricably linked with research at the largest of scales (the cosmos). The particle physicists of today have joined forces with astronomers in exploring the origins of the Universe-and in particular, the origins of matter.

A Brief History of Particle Physics

During the past two centuries, scientists have made great progress in understanding what we and the world about us are made of. First came the realisation that matter consists of basic substances, or elements, with well defined physical and chemical properties. These elements range from hydrogen, the lightest, through to uranium and beyond.
Each element consists of building blocks - atoms - unique to the element, but the different atoms can combine to form an enormous variety of compounds from simple water to complex proteins. Yet, as scientists first discovered towards the end of the 19th century, atoms are not the simplest building bricks ofmatter.
Discovering the Nucleus, Geiger and Rutherford at Manchester University.
We now know that most of the mass of an atom is concentrated in a small, dense, positively-charged nucleus. A cloud of tiny negatively-charged electrons envelopes the nucleus, but at a relatively large distance, so that much of the volume of an atom is empty space. In most atoms the nucleus contains two types of particle of almost equal mass: positively-charged protons and electrically neutral neutrons. To make the atom neutral overall, the number of protons exactly balances the number of electrons.
This picture of the atom stems largely from pioneering work at Cambridge and Manchester Universities. At Cambridge in the 1890s, two physicists began unwittingly to probe the world within the atom. One, Joseph ('J.J.') Thomson, discovered the first known subatomic particle, the electron, while one of his students, Ernest Rutherford, started to explore the new phenomenon of radioactivity, in which atoms change from one kind to another. This was to lead Rutherford eventually to the discovery of the atomic nucleus, in work with Hans Geiger (of Geiger counter fame) and Ernest Marsden at Manchester University in 1909-10. Later, Rutherford found that atoms contain positively-charged particles, identical to the nucleus of hydrogen. He called the particles protons. And at Cambridge in 1932, James Chadwick showed that the nucleus must also contain neutrons. By this time Rutherford and his colleagues had established much of the modern picture of the atom.
The first observation of a positive Kaon by Clifford Butler and
George Rochester in 1947. (The Kaon decays at 'B')
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