grand unified theory

According to many physicists, the primary goal of physics today is the grand unified theory. it is supposed to describe the four forces as different aspects of a same force.
the four forces, gravity, electromagnetic force, strong nuclear force, weak nuclear force have to be established as single form at some point(energy level) that get branched later on in the evolution process(cooling of earth) after big bang
scientists,indeed,successfully combined three of the forces other than gravity.the first two forces that got unified were electromagnetic force and weak nuclear force in the year 1967 by Abdus Salam and Steven Weinberg.

They suggested that there were other massive particles along with photon(EM force carrier) having same spin,that carry weak nuclear force, collectively called as massive vector bosons(W+,W-,Z0), and the way they got divided is explained by a property called spontaneous symmetry breaking,which means that,what ever appear to be a number of completely different particles at low energies are in fact found to be all the same type of particle,only in different states.all these particles behaves similarly at higher energies(around 100's of Gev) and the symmetry get broken at lower particle energies to form massive W+,W- and Z0 along with photons.

later it was found that the strong nuclear force which was carried by gluons get weaker at higher energies making quarks and gluons act freely.
It creates a new hope,that there must be some energy level where gluons, photons and bosons all behave the same & they predicted that it must be around thousand million million Gev and it can't be proved as there are no such oscillators till date.
they also predicted that quarks and electrons would behave the same at that grand unified energy level.

Now the process of unifying gravity along with the other three is going on...

hope they will find answers soon.
check this video

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four fundamental forces

The four fundamental force of universe are
1.gravitational force
2.electromagnetic force
3.strong nuclear force
4.weak nuclear force

these four forces are carried by their respective particles as listed below
gravitational force by gravitons
electromagnetic force by photons
strong nuclear force by gluons
weak nuclear force by bosons

out of the four forces gravitational force is considered the weakest, and the strong nuclear force which is carried by gluons is considered the strongest.

Gravitational force

Gravitational force, the weakest of the four forces, is about 10^-36 times the strength of the strong nuclear force.The messenger particle of gravitational force is the graviton. It has not been experimentally verified, mainly because it is extremely hard to find the smallest denomination of the weakest force. Recent calculations show that it will likely be massless.

Gravitational force is always attractive and that's what hold our universe together.

And somehow scientists are trying to include this in to a grand unified theory, where they successfully included the other three ..

Electromagnetism

Its strength is a bit less than strong nuclear force, and unlike gravitational force, it has both attractive and repulsive nature and is of infinite range--like gravity.

If gravitational force is what responsible for keeping up our universe together, EM is responsible for keeping up electrons around nucleus(attraction force between nucleus and electrons).

It is the force that causes the interaction between electrically charged particles; the areas in which this happens are called EM fields, also known as B fields in physics classes.

The particle that carry electromagnetism is the photon, a massless particle that travels at a speed of 299 792 458 m/s or 299 972 km/s .

The Weak Nuclear Force

The weak nuclear force is one of the less familiar fundamental forces. It operates only on the extremely short distance scales found in an atomic nucleus. The weak force is responsible for radioactive decay. In actuality, it is stronger than electromagnetism, but its messenger particles (W and Z bosons) are so massive and sluggish that they do not faithfully transmit its intrinsic strength.

The Strong Nuclear Force

Like the weak force, its range is limited to subatomic distances. quarks which forms the protons and neutrons stick together through this force. this fprce is carried by gluons and is a massless particle, as it glues the quarks together,its called a gluon.gluons also acts on other glons and that is why, as the distance increases the force increases at subatomic level .

Attempts have been going on to unify all these four fundamental forces to form a grand unified theory, and had successfully unified the other three, excluding gravity. Hope they will succeed soon.

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Dark matter and dark energy

Dark matter and dark energy ,these two are the most interesting problems in world of astronomy.they dominate the universe like comprising almost 96 percent of mass and energy that exists in the universe.
But noone knows what they are. It's tempting to consider them products of the same unknown phenomenon, something theorist Robert Scherrer suggests. The professor of physics at Vanderbilt University says "k-essence" is behind it all.
Dark matter was invoked decades ago to explain why galaxies hold together. Given regular matter alone, galaxies might never have formed, and today they would fly apart. So there must be some unknown stuff that forms invisible clumps to act as gravitational glue.
Dark energy hit the scene in the late 1990s when astronomers discovered the universe is not just expanding, but racing out at an ever-faster pace. Some hidden force, a sort of anti-gravity, must be pushing galaxies apart from one another in this accelerated expansion.
Separate theories have been devised to try and solve each mystery.
To explain dark energy, for example, theorists have re-employed a "cosmological constant" that Einstein first introduced as a fudge factor to balance the force of gravity. Einstein called the cosmological constant a great blunder and retracted it. Yet many theorists now are comfortable re-employing it to account for the effects of dark energy. But it does not reveal what the force is.
Scherrer agrees two explanations might be necessary, but he's also bothered by that complexity.

"It is somewhat embarrassing to have two different unknown sources for the dominant forms of matter and energy in the universe," he said in an e-mail interview. "On the other hand, that may just be the way things are. We don't get to pick the universe we live in."
To explain this, Scherrer invokes an interesting energy field called scalar field. It's a bit like an electric or magnetic field, with energy and pressure and a magnitude. But a scalar field has no direction. A scalar field is thought to have been behind inflation, the less-than-a-second period after the Big Bang when the universe expanded many billions of times before settling into a more reasonable rate of growth.
Scherrer borrows from work by Princeton University's Paul Steinhardt, V. Slava Mukhanov at the University of Munich and Christian Armendáriz Picón of the University of Chicago, relying on a specific type of second-generation scalar field they envisioned called k-essence, short for kinetic-energy-driven quintessence.
K-essence changes behavior over time in Scherrer's model, clumping early on to help form galaxies, and now forcing the universe apart. Right now, dark matter has a density that decreases as the universe expands, he explained, while dark energy has a density that stays constant as the universe expands.
"That means that at very early times, the dark matter 'piece' of the k-essence is the dominant one," Scherrer said. "As the universe expands and the density of the dark matter 'piece' of the k-essence decreases, it eventually falls below the density of the dark energy 'piece,' and the k- essence behaves more like dark energy."
"Scherrer's model , not the first trying to tie dark energy and dark matter together ", was published July 2 in the online version of the journal Physical Review Letters.

drawback

Although Scherrer's model has a number of positive features, it also has some drawbacks. For one thing, it requires some extreme "fine-tuning" to work. The physicist also cautions that more study will be required to determine if the model's behavior is consistent with other observations. In addition, it cannot answer the coincidence problem: Why we live at the only time in the history of the universe when the densities calculated for dark matter and dark energy are comparable. Scientists are suspicious of this because it suggests that there is something special about the present era.

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Quarks and Leptons

Leptons (the most famous being the electron), and quarks (of which baryons, such as protons and neutrons, are made) combine to form atoms, which in turn form molecules. Because atoms and molecules are said to be matter, it is natural to phrase the definition as: ordinary matter is anything that is made of the same things that atoms and molecules are made of. (However, notice that one also can make from these building blocks matter that is not atoms or molecules.) Then, because electrons are leptons, and protons and neutrons are made of quarks, this definition in turn leads to the definition of matter as being "quarks and leptons", which are the two types of elementary fermions. Carithers and Grannis state: Ordinary matter is composed entirely of first-generation particles, namely the [up] and [down] quarks, plus the electron and its neutrino. (Higher generations particles quickly decay into first-generation particles, and thus are not commonly encountered.)

This definition of ordinary matter is more subtle than it first appears. All the particles that make up ordinary matter (leptons and quarks) are elementary fermions, while all the force carriers are elementary bosons. The W and Z bosons that mediate the weak force are not made of quarks or leptons, and so are not ordinary matter, even if they have mass. In other words, mass is not something that is exclusive to ordinary matter.

The quark–lepton definition of ordinary matter, however, identifies not only the elementary building blocks of matter, but also includes composites made from the constituents (atoms and molecules, for example). Such composites contain an interaction energy that holds the constituents together, and may constitute the bulk of the mass of the composite. As an example, to a great extent, the mass of an atom is simply the sum of the masses of its constituent protons, neutrons and electrons. However, digging deeper, the protons and neutrons are made up of quarks bound together by gluon fields (see dynamics of quantum chromodynamics) and these Gluons fields contribute significantly to the mass of hadrons. In other words most of what composes the "mass" of ordinary matter is due to the binding energy of quarks within protons and neutrons. For example, the sum of the mass of the three quarks in a nucleon is approximately 12.5 MeV/c2, which is low compared to the mass of a nucleon (approximately 938 MeV/c2).The bottom line is that most of the mass of everyday objects comes from the interaction energy of its elementary components.

from:wikipedia.org

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Fundamental particles that made universe

Formation of Matter

All matter, including the atoms in our bodies, the air we breathe and the gas in the Sun is composed is combinations of fundamental particles that were created during the Big Bang and subsequent evolution of the Universe. Before giving an outline of the key stages in the formation of matter we need to review the fundamental particles and forces in the Universe.

Fundamental particles, the building blocks of the Universe

Our current understanding of physics allows us to model events in the Universe nearly, but not quite back to the moment of the big bang. Significant developments in our understanding of the very early Universe are due to advances in high-energy particle physics and particle accelerators such as those at CERN. According to the "Standard Model" of particle physics we now know that all the matter around us is composed of combinations of only a few fundamental particles. These twelve particles fall into two families, quarks and leptons.

Quarks are the particles that group together to form hadrons. Hadrons made of three quarks in turn are called baryons. The most familiar baryons to us are the protons and neutrons that comprise the nuclei of the atoms in our bodies and the rest of the Universe. A proton comprises two up quarks and one down quark, whilst a neutron has two down quarks and only one up quark. If you study the following table you will see that quarks have charges that are fractions of the charge of an electron, e. Hence the overall or net charge of a proton = 2 × (+2e/3) - 1 ×(-1e/3) = +1e and the overall charge of the neutron is 0.

Leptons include three charged particles, the electron, muon and tau particle. Each of these has an associated neutrino particle that is neutral.

Together these twelve particles are the building blocks of matter. Interestingly though, each of them has a corresponding antiparticle. These differ only in having the opposite charge but have the same mass as the corresponding matter particle. These antiparticles collectively are known as antimatter.

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big bang theory-some common misconceptions

The most common misconception regarding big bang is: lot of people think that Big Bang is an enormous explosion that took place at the beginning of our universe, and is not true.

Its actually was an expanding process that had begin around 13.7 million years ago and is still in continuation.
If you want to imagine the process, try to imagine a balloon expanding when we blow air in to it rather than a popping out balloon.

The second common misconception is that we try to imagine singularity as some glowing fire ball present somewhere in space.

The truth being space, time, matter, and energy, are meaningless before big bang.

Our known universe didn't exist before big bang, and it implies that space happens to exist inside the singularity, not that singularity exists in space.

No one until now knows, where and why did this singularity happened to appear!
All that we know so far is, our universe lies inside it and at some point it was not there and neither did our universe.
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simple than you believe

I don't know how to write my first post,lot of thoughts start whirling in me.lets start like this.

our universe might be confusing at times but there is always a reason and it can be found if you really believe that it can be found.that is what most of physicists do.Stephen hawking is trying to found the universal theory where most of us won't believe in.

start seeing the universe in a different view. don't follow them,try to find your own universe and the rules that govern ,they are very simple..

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