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A Theory of Everything

The fundamental particles of the universe that physicists have identified—electrons, neutrinos, quarks, and so on—are the "letters" of all matter. Just like their linguistic counterparts, they appear to have no further internal substructure. String theory proclaims otherwise. According to string theory, if we could examine these particles with even greater precision—a precision many orders of magnitude beyond our present technological capacity—we would find that each is not pointlike but instead consists of a tiny, one-dimensional loop. Like an infinitely thin rubber band, each particle contains a vibrating, oscillating, dancing filament that physicists
have named a string.

Are the fundamental particles that comprise galaxies and everything else in the universe made of tiny, vibrating loops? So say string theorists

Although it is by no means obvious, this simple replacement of point-particle material constituents with strings resolves the incompatibility between quantum mechanics and general relativity (which, as currently formulated, cannot both be right). String theory thereby unravels the central Gordian knot of contemporary theoretical physics. This is a tremendous achievement, but it is only part of the reason string theory has generated such excitement.

FIELD OF DREAMS

In Einstein's day, the strong and weak forces had not yet been discovered, but he found the existence of even two distinct forces—gravity and electromagnetism—deeply troubling. Einstein did not accept that nature is founded on such an extravagant design. This launched his 30-year voyage in search of the so-called unified field theory that he hoped would show that these two forces are really manifestations of one grand underlying principle. This quixotic quest isolated Einstein from the mainstream of physics, which, understandably, was far more excited about delving into the newly emerging framework of quantum mechanics. He wrote to a friend in the early 1940s, "I have become a lonely old chap who is mainly known because he doesn't wear socks and who is exhibited as a curiosity on special occasions."

Einstein was simply ahead of his time. More than half a century later, his dream of a unified theory has become the Holy Grail of modern physics. And a sizeable part of the physics and mathematics community is becoming increasingly convinced that string theory may provide the answer. From one principle—that everything at its most microscopic level consists of combinations of vibrating strands—string theory provides a single explanatory framework capable of encompassing all forces and all

String theory is sometimes described as possibly being the "theory of everything

String theory proclaims, for instance, that the observed particle properties—that is, the different masses and other properties of both the fundamental particles and the force particles associated with the four forces of nature (the strong and weak nuclear forces, electromagnetism, and gravity)—are a reflection of the various ways in which a string can vibrate. Just as the strings on a violin or on a piano have resonant frequencies at which they prefer to vibrate—patterns that our ears sense as various musical notes and their higher harmonics—the same holds true for the loops of string theory. But rather than producing musical notes, each of the preferred mass and force charges are determined by the string's oscillatory pattern. The electron is a string vibrating one way, the up-quark is a string vibrating another way, and so on.

Far from being a collection of chaotic experimental facts, particle properties in string theory are the manifestation of one and the same physical feature: the resonant patterns of vibration—the music, so to speak—of fundamental loops of string. The same idea applies to the forces of nature as well. Force particles are also associated with particular patterns of string vibration and hence everything, all matter and all forces, is unified under the same rubric of microscopic string oscillations—the "notes" that strings can play.

Taken from pbs.org

God particle: A closer look at the Higgs boson

In Geneva Scientists announced the discovery of a new subatomic particle that looks remarkably like the long-sought higgs-boson. Sometimes called the "God particle" because its existence is fundamental to the creation of the universe, the hunt for the Higgs involved thousands of scientists from all over the world.

What is the God particle anyway?

School physics teaches that everything is made up of atoms, and inside atoms are electrons, protons and neutrons. They, in turn, are made of quarks and other subatomic particles. Scientists have long puzzled over how these minute building blocks of the universe acquire mass. Without mass, particles wouldn't hold together and there would be no matter.

A CMC Proton-proton Collision image

One theory proposed by British physicist Peter Higgs and teams in Belgium and the United States in the 1960s is that a new particle must be creating a "sticky" field that acts as a drag on other particles. The atom-smashing experiments at CERN, the European Center for Nuclear Research, have now captured a glimpse of what appears to be just such a Higgs-like particle.

Why is this important?

The Higgs is part of many theoretical equations underpinning scientists' understanding of how the world came into being. If it doesn't exist, then those theories would need to be fundamentally overhauled. The fact that it apparently does exist means scientists have been on the right track with their theories. But there's a twist: the measurements seem to diverge slightly from what would be expected under the so-called Standard Model of particle physics. This is exciting for scientists because it opens the possibility to potential new discoveries including a theory known as "super-symmetry" where particles don't just come in pairs - think matter and anti-matter - but quadruplets, all with slightly different characteristics.

How much did it cost?

CERN's atom smasher, the Large Hadron Collider, alone cost some $10 billion to build and run. This includes the salaries of thousands of scientists and support staff around the world who collaborated on the two experiments that independently pursued the Higgs.

Were there any practical results from the search?

Not directly. But the massive scientific effort that led up to the discovery has paid off in other ways, one of which was the creation of the World Wide Web. CERN scientists developed it to make it easier to exchange information among each other. The vast computing power needed to crunch all of the data produced by the atom smasher has also boosted the development of distributed - or cloud - computing, which is now making its way into mainstream services. Advances in solar energy capture, medical imaging and proton therapy - used in the fight against cancer - have also resulted from the work of particle physicists at CERN and elsewhere.

What's next

"This is just the beginning," says James Gillies, a spokesman for CERN. Scientists will keep probing the new particle until they fully understand how it works. In doing so they hope to understand the 96 per cent of the universe that remains hidden from view. This may result in the discovery of new particles and even hitherto unknown forces of nature

Taken from ibnlive.in

What is the Higgs boson ?

The Higgs boson is a type of elementary particle within the Standard Model of particle physics. It plays a key role in modern scientific theories of the universe and its existence or non-existence is considered pivotal in determining which theories about the nature of the physical universe are more likely to be correct.

Higgs boson has been found at CERN, a great accomplishment in the field of theoretical particle physics. This discovery means that the model we are currently using is completed: the final ingredient has been found. This model, called the Standard Model, yields very good predictions of what is happening in nature.

THE MYSTERY OF THE MASSIVE PARTICLES

When physicists were deriving the physics of elementary particles, they used certain assumptions about the universe, most of them are related to symmetries. What's a symmetry? Take for example rotational symmetry. Imagine you are standing in the middle of a round football stadium. It does not matter if you rotate, you will still see the same image. There is a very fancy theorem that says that every symmetry has an accompanied conserved quantity. The rotational symmetry, for example, yields conservation of angular momentum, whereas translational symmetry in time (meaning physics looks the same now and 10 minutes from now) yield conservation of energy.

Using some more advaced symmetry groups all of our beloved standard particles can be found:

The group in red are called gauge bosons. They are resultants of a very special symmetry and they can be interpreted as forces working on all the other particles. In fact, every elementary force has a matching gague boson. The photon (symbolised with a gamma), or "light", transfers electromagnetic forces, the gluon the strong force and Z and W the weak force.

But there is a problem. The theory requires the W and Z boson to be massless in order for the theory to work. This is obviously not the case, because these particles have been found to have mass. In fact, they are pretty heavy!

THE HIGGS MECHANISM

When physicist discovered that the theory was in trouble, they started searching for solutions. The symmetry of nature that can be used to find the gauge bosons worked far too good to just abandon it. Then, a new idea rose: we keep the symmetry, but we say nature broke it spontaneously. Wait, what?

How does this work? Imagine you have a piece of plastic between your fingers and you apply a little pressure to it. Initially, the plastic stick is straight, even when you apply a little pressure to it. Now the system (nature) has a symmetry: there is for example rotational symmetry if you are standing at the position of the rod (if you ignore the hand).

But remember the hand was applying a force? This means that the stick could spontaneously jump to either the left or the right, as can be seen in the picture (try this at home ;) ). Now the symmetry that nature had is broken, spontaneously and without external help. Note that in the analogy, the hand should be seen as an initial energy that the universe has.

Spontaneous symmetry breaking

A similar scenario this of a toy car that is sitting on a small mountain, but it has some energy which makes the car shift a little. Given enough time, the car will roll off the mountain into a valley, where it will remain.

Now, it turns out that breaking this symmetry can be done by introducing a particle: the Higgs particle. When analysing the properties of this particle, it turns out that this particle interacts with all the other particles, including itself! Due to these interactions, the particles gain mass.

WHY DID THIS TAKE SO LONG TO FIND?

Well, we didn't know where to look. Basically, in the LHC particles are shot at eachother with incredible speeds, and thus incredibly high energies. Since E=mc^2, it takes very high energies to create particles with high mass. The problem is, we don't know the mass of the Higgs, it is a free parameter of the theory. This means the mass is not predicted by the theory. And because of that, the whole LHC range has to be explored (with no guarantee that the Higgs boson is actually in this range).

Complications arise due to the fact the Higgs particle decays intoa lot of other particles very, very quickly. So we can actually only see the remnants of the Higgs particle. When there is enough energy to create a Higgs, we'd expect to see more of these remnants: a peak in a graph.

Today, the people at CERN announced that the peaks they found in many expirements, are trustworthy enough to say that the Higgs particle has been found at about 126 GeV. This is great news, because now we can confidently continue the search for theories that expand the standard model, like supersymmetry and other theories that may introduce gravity into the picture.