Birth of the universe 're-created': Large Hadron Collider generates 'mini Big Bang'

Scientists at the Large Hadron Collider have created a ‘mini Big Bang’ in an experiment that mimicked conditions a millionth of a second after the birth of the universe.

By colliding lead ions – atoms of lead stripped of their electrons – at close to the speed of light, researchers generated temperatures a million times hotter than the centre of the sun.

The explosions were so powerful they created a hot dense ‘soup’ of sub-atomic particles last seen just after the Big Bang, 13.7 billion years ago.

British scientists working at the collider near Geneva stressed that the experiments were completely safe and opened up a new era in particle physics.



A computer read-out of the real collisions between lead ions as seen by the ALICE inner detector at the Large Hadron Collider

The collisions generated temperatures a million times hotter than the centre of the sun, reproducing conditions not seen since just after the Big Bang.

The breakthrough comes after seven months of successfully colliding protons at high speeds at the LHC.



Dr David Evans, a member of the UK team from the University of Birmingham, said: 'We are thrilled with the achievement.

In search of the God Particle

The Large Hadron Collider (LHC) is a gigantic scientific instrument near Geneva, where it spans the border between Switzerland and France about 100 m underground.

It is a particle accelerator used by physicists to study the smallest known particles – the fundamental building blocks of all things. It will revolutionise our understanding, from the minuscule world deep within atoms to the vastness of the Universe.

These include the existence of anti-matter and the Higgs boson - a hypothetical particle that scientists think gives mass to other particles and therefore all objects in the universe. Two beams of subatomic particles called 'hadrons' – either protons or lead ions – will travel in opposite directions inside the circular accelerator, gaining energy with every lap.

Physicists are using the LHC to recreate the conditions just after the Big Bang, by colliding the two beams head-on at very high energy.

Teams of physicists from around the world will analyse the particles created in the collisions using special detectors in a number of experiments dedicated to the LHC.



'The collisions generated mini Big Bangs and the highest temperatures and densities ever achieved in an experiment.

'This process took place in a safe, controlled environment generating incredibly hot and dense sub-atomic fireballs with temperatures of over 10 trillion degrees, a million times hotter than the centre of the sun.

'At these temperatures even protons and neutrons, which make up the nuclei of atoms, melt resulting in a hot dense soup of quarks and gluons known as a quark-gluon plasma.'

Powerful magnets spun the lead ions round miles of underground tunnels at near the speed of light.



Flying in opposite directions, the particles were focused into a narrow beam and forced to collide inside the massive Alice 'detector'.

The experiments will come over the objections of some people who fear they could eventually imperil Earth by creating micro black holes - subatomic versions of collapsed stars whose gravity is so strong they can suck in planets and other stars.

Scientists have always dismissed any threat to Earth or people on it, saying that any such holes would be so weak that they would vanish almost instantly without causing any damage.

Scientists hope the quark-gluon plasma will allow them to learn more about the Strong Force, one of the four fundamental forces of nature.

'The Strong Force not only binds the nuclei of atoms together but is responsible for 98 per cent of their mass,' said Dr Evans. 'I now look forward to studying a tiny piece of what the universe was made of just a millionth of a second after the Big Bang.'

The Alice experiment is just one part of the LHC, whose circular beam tunnel runs for 16.7 miles, 328ft below the French/Swiss border.

Alice is 52.5ft high, 85 across and weighs around 10,000 tons.

Mini-versions of the 'Big Bang were created at the moment that these lead ions collided with each other. Their routes are traced in Alice's detector as seen here

A graphic showing the set up of the ALICE experiment including the beam tunnel that passes the protons and ions through the detector

Simulation: The Large Hadron Collider's ALICE experiment generated incredibly hot and dense sub-atomic fireballs to recreate the fundamental particles that existed in the first few microseconds after the Big Bang

The Alice experiment involves around 1,000 physicists and engineers from 100 institutes in 30 countries.

Britain's contribution includes eight physicists and engineers and seven PhD students from the University of Birmingham.

During the lead nuclei collisions Alice will download data at a rate of 1.2 gigabytes per second, producing the equivalent of more than three million CDs-worth of recorded information.

ALICE

All matter in the universe is made up of atoms. Each atom contains a nucleus composed of protons and neutrons, surrounded by a cloud of electrons. Protons and neutrons are in turn made of quarks which are bound together by other particles called gluons. This incredibly strong bond means that isolated quarks have never been found. In the ALICE experiment, the LHC collides lead ions to recreate the conditions just after the Big Bang under laboratory conditions. The data obtained will allow physicists to study a state of matter known as quark gluon plasma, which is believed to have existed soon after the Big Bang.

It is one of the four major experiments that sit in huge chambers at various points in the tunnel.

For lead-ions, as for protons before them, the procedure started with threading a single beam round the ring in one direction and steadily increasing the number of laps before repeating the process for the other beam.

Once circulating beams had been established they could be accelerated to the full energy of 287 TeV per beam. This energy is much higher than for proton beams because lead ions contain 82 protons.



Another period of careful adjustment was needed before lining the beams up for collision, and then finally declaring that nominal data taking conditions, known at CERN as stable beams, had been established.



The other three major experiments include CMS and Atlas, both of which are general-purpose detectors designed to analyse the myriad of particles produced by the collisions in the accelerator.



They are designed to investigate the largest range of physics possible.



The final experiment is LHC, which is also a specialised detector like Alice.



There are also two smaller experiments that are designed to focus on ‘forward particles’ (protons or heavy ions). These are particles that just brush past each other as the beams collide, rather than meeting head-on.