Keshav Mohan[1] & Anjana Prasad[2]
1.M S M College, Kayamakulam, Kerala, India
2.Sree Budha College of Engineering, Noornad, Kerala, India
INTRODUCTION – BIG BANG THEORY
Over a very long time, scientists had a great deal of thought of how and when did the universe form and the types of matter and energy filled the universe. A branch of science named Physical Cosmology deals with the study of physical evolution and origin of the universe. As like any other fields of science, cosmology involves in the formation of theories about the universe, which make specific predictions for phenomena that can be tested with observations. The Big Bang Theory is currently the dominant scientific explanation for the prevailing theory about the origin and evolution of our universe. The Big Bang model of cosmology rests on two key ideas that date back to the early 20th century: The first key idea dates to 1916 when Einstein developed his General theory of Relativity in which he proposed that gravity is no longer described by a gravitational “field” but rather it is supposed to be a distortion of space and time. The second key idea was the Cosmological principle, which assumes the matter in the universe is homogeneous and isotropic when averaged over very large scales.
The Big Bang model is a broadly accepted Cosmological theory for the origin and formation of universe. NASA's Wilkinson Microwave Anisotropy Probe (WMAP) project estimates the age of the universe to be between 13.5 and 14.0 billion years, at that time the portion of the universe we can see today was only a few millimeters across and it expanded from a hot dense state into the vast and much more cooler cosmos.
Artist's depiction of the WMAP satellite
Scientists were trying to conduct an experiment on a miniature version of the "Big Bang" which will recreate the conditions a few moments after the Big Bang. Scientists hope to find answers to questions about black holes, dark matter and why the universe appears the way it does.
The term Big Bang generally refers to the idea that the universe has expanded from a primordial hot and dense initial condition at some finite time in the past, and continues to expand to this day. The Big Bang theory developed from observations of the structure of the universe and from theoretical considerations. In 1912 Vesto Slipher measured the first Doppler shift of a "spiral nebula" (spiral galaxies), and soon discovered that almost all such nebulae were receding from Earth. Ten years later, Alexander Friedmann, a Russian cosmologist and mathematician, derived the Friedmann equations from Albert Einstein's equations of general relativity, showing that the universe might be expanding in contrast to the static universe model advocated by Einstein. In 1924, Edwin Hubble's measurement of the great distance to the nearest spiral nebulae showed that these systems were indeed other galaxies. Hubble discovered a correlation between distance and recession velocity—now known as Hubble's law. He also proposed that the light from a given galaxy was shifted further towards the red end of the light spectrum (Red Shift).
In 1927, Georges Lemaitre, a Belgian physicist and Roman Catholic priest, predicted that the recession of the nebulae was due to the expansion of the universe. In 1931 Lemaitre went further and suggested that the evident expansion in forward time required that the universe contracted backwards in time, and would continue to do so until it could contract no further, bringing all the mass of the universe into a single point, a "primeval atom". The discovery and confirmation of the cosmic microwave background radiation in 1964 secured the Big Bang as the best theory of the origin and evolution of the cosmos. Huge strides in Big Bang cosmology have been made since the late 1990s as a result of major advances in telescope technology as well as the analysis of copious data from satellites such as COBE, the Hubble Space Telescope and WMAP.
Hubble Deep Field Image: The famous "Deep
Field Image" taken by the Hubble Space Telescope
THE BIG BANG THEORY
According to the standard Big Bang theory, our universe sprang into existence as "singularity" around 13.7 billion years i.e. there were no differentiated planets, stars, suns, and galaxies. Singularities are thought to exist at the core of "black holes." Black holes are areas of intense gravitational pressure. The pressure is thought to be so intense that finite matter is actually squished into infinite density
After its initial appearance, five billion years ago, the compact hydrogen soup blasted apart with huge force, matter was hurled in all directions. The Big Bang theory predicts that the early universe was a very hot place. The early hot, dense phase is itself referred to as "the Big Bang", and is considered the "birth" of our universe. The universe was filled homogeneously and isotropically with an incredibly high energy density, huge temperatures and pressures, and was very rapidly expanding and cooling.
Approximately 10−35 seconds into the expansion, a phase transition caused a cosmic inflation, during which the universe grew exponentially. After inflation stopped, the universe consisted of a quark-gluon plasma, as well as all other elementary particles. Temperatures were so high that the random motions of particles were at relativistic speeds, and particle-antiparticle pairs of all kinds were being continuously created and destroyed in collisions leading to a very small excess of quarks and leptons over antiquarks and anti-leptons. This resulted in the predominance of matter over antimatter in the present universe.
The universe continued to grow in size and fall in temperature; hence the typical energy of each particle was decreasing. At about 10−6 seconds, quarks and gluons combined to form baryons such as protons and neutrons. The small excess of quarks over antiquarks led to a small excess of baryons over antibaryons. The temperature was now no longer high enough to create new proton-antiproton pairs. A similar process happened at about 1 second for electrons and positrons. After these annihilations, the remaining protons, neutrons and electrons were no longer moving relativistically and the energy density of the universe was dominated by photons.
A few minutes into the expansion, when the temperature was about a billion neutrons combined with protons to form the universe's deuterium and helium nuclei in a process called Big Bang Nucleosynthesis (BBN).
Most protons remained uncombined as hydrogen nuclei. As the universe cooled, the rest mass energy density of matter came to gravitationally dominate that of the photon radiation. After about 379,000 years the electrons and nuclei combined into atoms (mostly hydrogen); hence the radiation decoupled from matter and continued through space largely unimpeded. This relic radiation is known as the cosmic microwave background (CMB) radiation.
WMAP image of the cosmic microwave background radiation
Over a long period of time, the slightly denser regions of the nearly uniformly distributed matter gravitationally attracted nearby matter and thus grew even denser, forming gas clouds, stars, galaxies, and the other astronomical structures observable today. The details of this process depend on the amount and type of matter in the universe.
The three possible types of matter are known as cold dark matter, hot dark matter and baryonic matter. The best measurements available show that the dominant form of matter in the universe is cold dark matter. The other two types of matter make up less than 18% of the matter in the universe.
A pie chart indicating the proportional composition of different energy-density components of the universe
About 3,00000 years later, when things cooled, light elements like hydrogen and helium were formed. This condition, which catapulted in expanded direction that allowed the volume to increase and created the universe.
The gravitational force brought them together in clumps. These clumps became the seeds of galaxies. After a long time, stars formed including the Sun, our closest star. We can see the remnants of this hot dense matter as the now very cold CMB radiation, which still pervades the universe.
We may not be able to exactly confirm whether the Big Bang Theory is accurate or not. But based on the observations in the past, there are evidences, which supports Big Bang theory. Our universe is indeed expanding up to this very moment. Edwin Hubble’s discovery supports the idea of the Big Bang. He observed that some galaxies are accelerating outward and becomes farther away from our vantage point. The main concept is that, if the materials in the universe are staying away from each other at an expanded direction, then everything must have been closer together initially. The National Aeronautics and Space Administration's (NASA) Cosmic Background Explorer (COBE) spacecraft mapped the cosmic background radiation between 1989 and 1993. It verified that the distribution of intensity of the background radiation precisely matched that of matter that emits radiation because of its temperature, as predicted for the big bang theory. It also showed that the cosmic background radiation is not uniform, that it varies slightly. These variations are thought to be the seeds from which galaxies and other structures in the universe grew. Another possible concept that supports the theory is the presence of abundant elements around us and in space. Hydrogen and Helium are both abundant in the cosmos. This only tells us that everything must have come from a variety of these two elements, which are initially the main components of that initial condition before the universe was born
THE BIG BANG EXPERIMENT
The European Laboratory for Particle Physics (CERN), based outside Geneva, conducted a series of experiments, which smashed together heavy lead ions in a fireball to prove a theory that had only existed on paper for years. For the tests, engineers built a giant contraption called Large Hadron Collider (LHC).
The Large Hadron Collider (LHC) is the world's largest and highest-energy particle accelerator, intended to collide opposing beams of protons or lead ions, each moving at about 99.9999991% of the speed of light.
The large circle, 17 miles in circumference, shows the LEP tunnel which houses the massive machine buried under 100 meters of rock.
The LHC, which is the heart of this experiment, took two decades to construct. It is the world's largest and highest-energy particle accelerator. The LHC was built by the European Organization for Nuclear Research (CERN) with the intention of testing various predictions of high-energy physics, including the existence of the hypothesized Higgs boson, which is a theoretical particle responsible for the transition between energy and matter. The LHC lies in a 17 mile tunnel buried under 100 meters of rock in the borders of Switzerland and France between the Jura Mountains and the Alps near Geneva, Switzerland.
An underground representation of the Large Hadron Collider, which stretches for 27 kilometers
The collider is contained in a circular tunnel, with a circumference of 27 kilometers (17 miles), at a depth ranging from 50 to 175 meters underground. The 3.8 m wide concrete-lined tunnel, constructed between 1983 and 1988, was formerly used to house the Large Electron-Positron (LEP) Collider. It crosses the border between Switzerland and France at four points, with most of it in France. The collider tunnel contains two adjacent parallel beam pipes that intersect at four points, each containing a proton beam, which travels in opposite directions around the ring.
Inside the accelerator, two beams of particles travel at close to the speed of light with very high energies before colliding with one another. The beams travel in opposite directions in separate beam pipes – two tubes kept at ultrahigh vacuum. They are guided around the accelerator ring by a strong magnetic field, achieved using superconducting electromagnets.
LHC in its tunnel
These are built from coils of special electric cable that operates in a superconducting state, efficiently conducting electricity without resistance or loss of energy. This requires chilling the magnets to about ‑271°C – a temperature colder than outer space! For this reason, much of the accelerator is connected to a distribution system of liquid helium, which cools the magnets, as well as to other supply services.
View of LHC cryo-magnet inside the tunnel
Thousands of magnets of different varieties and sizes are used to direct the beams around the accelerator. These include 1232 dipole magnets of 15 m length, which are used to bend the beams, and 392 quadrupole magnets, each 5–7 m long, to focus the beams. Just prior to collision, another type of magnet is used to 'squeeze' the particles closer together to increase the chances of collisions. The particles are so tiny that the task of making them collide is akin to firing needles from two positions 10 km apart with such precision that they meet halfway.
Detectors inside LHC
All the controls for the accelerator, its services and technical infrastructure are housed under one roof at the CERN Control Centre. From here, the beams inside the LHC will be made to collide at four locations around the accelerator ring, corresponding to the positions of the particle detectors.
The six experiments at the LHC are all run by international collaborations, bringing together scientists from institutes all over the world. Each experiment is distinct, characterized by its unique particle detector.
The two large experiments, ATLAS and CMS, are based on general-purpose detectors to analyze the myriad of particles produced by the collisions in the accelerator and two medium-size experiments, ALICE and LHCb, have specialized detectors for analyzing the LHC collisions in relation to specific phenomena. The other two experiments, TOTEM and LHCf, are much smaller in size. They 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
The ATLAS, CMS, ALICE and LHCb detectors are installed in four huge underground caverns located around the ring of the LHC. The detectors used by the TOTEM experiment are positioned near the CMS detector, whereas those used by LHCf are near the ATLAS detector.
ATLAS (A Toroidal LHC ApparatuS) - is one of two general-purpose detectors at the LHC. It will investigate a wide range of physics, including the search for the Higgs boson, extra dimensions, and particles that could make up dark matter.
Assembly and installation of ATLAS
The size of ATLAS detector is about 46m long, 25m high and 25m wide. The ATLAS detectors is the largest volume particle detector ever constructed which weight 7000 tones and is located at Meyrin, Switzerland
The main feature of the ATLAS detector is its enormous doughnut-shaped magnet system. This consists of eight 25‑m long superconducting magnet coils, arranged to form a cylinder around the beam pipe through the centre of the detector. During operation, the magnetic field is contained within the central cylindrical space defined by the coils. More than 1700 scientists from 159 institutes in 37 countries work on the ATLAS experiment.
CMS (Compact Muon Solenoid) - The CMS experiment uses a general-purpose detector to which have the same scientific goals as the ATLAS experiment. It uses different technical solutions and design of its detector magnet system to achieve these.
View of CMS
The Size of CMS is 21 m long, 15 m wide and 15 m high and is located in Cessy, France. The CMS detector is built around a huge solenoid magnet. This takes the form of a cylindrical coil of superconducting cable that generates a magnetic field of 4 teslas, about 100 000 times that of the Earth.
The magnetic field is confined by a steel 'yoke' that forms the bulk of the detector's weight of 12 500 tonnes. An unusual feature of the CMS detector is that instead of being built in-situ underground, like the other giant detectors of the LHC experiments, it was constructed on the surface, before being lowered underground in 15 sections and reassembled.
View of ALICE
The Size of ALICE is 26 m long, 16 m high, 16 m wide and is located at St Genis-Pouilly. Collisions in the LHC will generate temperatures more than 100 000 times hotter than the heart of the Sun. Physicists hope that under these conditions, the protons and neutrons will 'melt', freeing the quarks from their bonds with the gluons. This should create a state of matter called quark-gluon plasma, which probably existed just after the Big Bang when the Universe was still extremely hot.
LHCb (Large Hadron Collider beauty) - The LHCb experiment will help us to understand why we live in a Universe that appears to be composed almost entirely of matter, but no antimatters. It specializes in investigating the slight differences between matter and antimatter by studying a type of particle called the 'beauty quark', or 'b quark'.
The Size is around 21m long, 10m high and 13m wide and is located at Ferney-Voltaire, France. Instead of surrounding the entire collision point with an enclosed detector, the LHCb experiment uses a series of sub-detectors to detect mainly forward particles. The first sub-detector is mounted close to the collision point, while the next ones stand one behind the other, over a length of 20 m.
TOTEM (TOTal Elastic and diffractive cross section Measurement) - The TOTEM experiment studies forward particles to focus on physics that is not accessible to the general-purpose experiments. Among a range of studies, it will measure, in effect, the size of the proton and also monitor accurately the LHC's luminosity.
LHCf (Large Hadron Collider forward) - The LHCf experiment uses forward particles created inside the LHC as a source to simulate cosmic rays in laboratory conditions. Cosmic rays are naturally occurring charged particles from outer space that constantly bombards the Earth's atmosphere. They collide with nuclei in the upper atmosphere, leading to a cascade of particles that reaches ground level.
THE LHC EXPERIMENT begins: On September 10, 2008, the Large Hadron Collider (LHC) switched on in Geneva. The first beam was circulated through the collider. CERN successfully fired the protons around the tunnel in stages, three kilometers at a time. The particles were fired in a clockwise direction into the accelerator and successfully steered around it. After a series of trial runs, two white dots flashed on a computer screen showing the protons traveled the full length of the collider. CERN next successfully sent a beam of protons in a counterclockwise direction, taking slightly longer at one and a half hours due to a problem with the cryogenics.
A simulated lead – ion collision within the LHC device
Beams of protons will be accelerated in opposite directions through the ring-shaped tunnel, which is supercooled to just 1.9 degrees above absolute zero (minus 271C), the lowest temperature allowed by nature.
Reaching velocities of 99.99% the speed of light, each beam will pack as much energy as a Eurostar train travelling at 150 kilometers per hour. That is enough to melt 500 kilograms of copper. The particles will be brought together in four huge "detectors" placed along the ring. Each detector is like a giant microscope, designed to probe deeper into the heart of matter than has ever been possible before. A chain of smaller accelerators, built for earlier projects, are first used to speed up the proton beams to the point where they can be injected into the LHC. The start of the process is a bottle of hydrogen gas no bigger than a fire extinguisher. Hydrogen atoms are stripped of their electrons to produce streams of protons that are fed into accelerators of increasing size. The last link in the chain before the LHC, the Super Proton Synchrotron (SPS), is itself buried underground and covers a distance of seven kilometers.
Switching on the LHC will create conditions that existed a fraction of a second after the Big Bang. Timing between the SPS and the LHC has to be accurate to within a fraction of a nanosecond. The first 'switch on' involved transferring a beam from the SPS to the LHC so that it is circulating around the machine in a stable fashion. After this has been successfully accomplished another beam will be sent spinning in the opposite direction. The final step will be to boost the energy of each beam to a record five tera electron volts (Tev). (One Tev is equal to a trillion (1,000,000,000,000) electron volts. Eventually the aim is to raise the energy level to seven Tev, probably by 2010.) It is in these conditions that scientists hope to find fairly quickly a theoretical particle known as the Higgs Boson, named after Scottish scientist Peter Higgs who first proposed it in 1964, as the answer to the mystery of how matter gains mass. Without mass, the stars and planets in the universe could never have taken shape in the eons after the Big Bang, and life could never have begun - on Earth or, if it exists as many cosmologists believe, on other worlds either.
CHALLENGES IN THE BIG BANG EXPERIMENT
As we know challenges is always part of any big experiments. There were some major operational challenges during the Big Bang experiment. The size of the LHC constitutes an exceptional engineering challenge with unique operational issues on account of the huge energy stored in the magnets and the beams. While operating, the total energy stored in the magnets is 10 GJ (equivalent to one and a half barrels of oil or 2.4 tons of TNT) and the total energy carried by the two beams reaches 724 MJ (about a tenth of a barrel of oil, or half a lightning bolt).
Loss of only one ten-millionth part (10−7) of the beam is sufficient to quench a superconducting magnet, while the beam dump must absorb 362 MJ, an energy equivalent to that of burning eight kilograms of oil, for each of the two beams. These immense energies are even more impressive considering how little matter is carrying it: under nominal operating conditions (2,808 bunches per beam, 1.15×1011 protons per bunch), the beam pipes contain 1.0×10-9 gram of hydrogen, which, in standard conditions for temperature and pressure, would fill the volume of one grain of fine sand.
On 10 August 2008, a group of hackers calling themselves the Greek Security Team defaced a website at CERN, criticizing their computer security. If the hackers were managed to enter the second computer network, they could have turned off many parts of the experimental machine. There was no access to the control network of the collider.
Scientists at CERN had to shut down the huge particle collider, just 10 days after the project kicked off, due to some technical glitch of leaking helium into the tunnel housing the machine. After a technical fault in the LHC, the CERN reported that the collider will not be able to start until spring 2009. According to CERN, the reason behind the helium leakage into the collider’s tunnel was probably due to a faulty electrical connection between two of the accelerator’s massive magnets. However, to understand the whole fault the team of scientists will now have to raise those sections of the tunnel back from its operating temperature of minus 271.3 degrees Celsius to room temperature and open up the massive magnets for inspection. The investigation and repairs may take three to four weeks time, which will be followed by CERN’s winter maintenance period. The whole repairing process may take several weeks; hence the CERN is hopeful to restart the complex project by early spring 2009.
Once the LHC starts functioning again, CERN will resume sending particle-beams around the 27 km long tunnel. The next step of the experiment is to smash beams travelling in opposite directions into each other at a speed almost close to that of light. The beams would recreate heat and energy of the ‘Big Bang’ on a miniature scale. When at a full speed, the collider will generate 600 million collisions every second of subatomic particles called protons that will detonate in a burst of new and formerly unknown types of particles. With the experiment, the CERN scientists are expecting to come across the phenomena of ‘Big Bang’, which is believed by cosmologists to be behind the origin of our expanding universe.
We are all curious to know the origin and formation of our universe, and we hope these experiments and theories will delight those hidden truths one day or other.
REFERENCES:
· http://en.wikipedia.org/wiki/Big_bang
· http://public.web.cern.ch/public/
· http://map.gsfc.nasa.gov/site/
· http://astro.berkeley.edu/%7Emwhite/darkmatter/hubble.html