WHAT IS ANTIMATTER

ANTI-MATTER :

Antimatter is the opposite of normal matter. More specifically, the sub-atomic particles of antimatter have properties opposite those of normal matter. The electrical charge of those particles is reversed. Antimatter was created along with matter after the Big Bang, but antimatter is rare in today's universe, and scientists aren't sure why.

Where is it?

Antimatter particles are created in ultra high-speed collisions. In the first moments after the Big Bang, only energy existed. As the universe cooled and expanded, particles of both matter and antimatter were produced in equal amounts. Why matter came to dominate is a question that scientists have yet to discover. 

One theory suggests that more normal matter was created than antimatter in the beginning, so that even after mutual annihilation there was enough normal matter left to form stars, galaxies and us. 

To better understand antimatter, one needs to know more about matter. Matter is made up of atoms, which are the basic units of chemical elements such as hydrogen, helium or oxygen. Each element has a certain number of atoms: Hydrogen has one atom; helium has two atoms; and so on.

In 1928, British physicist Paul Dirac wrote down an equation that combined quantum theory and special relativity to describe the behaviour of an electron moving at a relativistic speed. The equation – which won Dirac the nobel prize in 1933  – posed a problem: just as the equation x2=4 can have two possible solutions (x=2 or x=-2), so Dirac's equation could have two solutions, one for an electron with positive energy, and one for an electron with negative energy. But classical physics (and common sense) dictated that the energy of a particle must always be a positive number.

Dirac interpreted the equation to mean that for every particle there exists a corresponding antiparticle, exactly matching the particle but with opposite charge. For the electron there should be an "anti -electron", for example, identical in every way but with a positive electric charge. The insight opened the possibility of entire galaxies and universes made of antimatter.

WHAT IS QUARK ?

A quark is a fundamental particle which possesses both electric charge and 'strong' charge. They combine in groups of two or three to form composite objects (called mesons and baryons, respectively), held together by the strong force. Protons and neutrons are familiar examples of such composite objects -- both are made up of three quarks. 

Quarks and Lepton  are the building blocks which build up matter, i.e., they are seen as the "elementary particles". In the present standard model, there are six "flavors" of quarks. They can successfully account for all known mesons and Baryons  (over 200). The most familiar baryons are the Proton and Neutron , which are each constructed from up and down quarks. Quarks are observed to occur only in combinations of two quarks (mesons), three quarks (baryons). There was a recent claim of observation of particles with five quarks (pentaquark), but further experimentation has not borne it out.

WHAT IS ANTI-QUARK ?

Anti quark is the opposite of quark.the spins ,the charge are same but its a opposite of QUARK.

A anti-quark is a fundamental particle WHICH BUILD UP ANTI MATTER.

Antimatter spaceship?

When antimatter particles interact with matter particles, they annihilate each other and produce energy. This has led engineers to speculate that antimatter-powered spacecraft might be an efficient way to explore the universe.

it takes about $100 billion to create a milligram of antimatter. While research can get by on a lot less antimatter, this is the minimum that would be needed for application. 

"To be commercially viable, this price would have to drop by about a factor of 10,000," the agency wrote. Power generation creates another headache: "It costs far more energy to create antimatter than the energy one could get back from an antimatter reaction."

The design calls for pellets of Deuterium and tritium (heavy hydrogen isotopes with one or two neutrons in their nuclei, unlike common hydrogen that has no neutrons). An antiproton beam would then be beamed into the pellets, which would bash against a layer of uranium embedded inside. 

After the antiprotons strike the uranium, both would be destroyed and create fission products that would spark a fusion reaction. Properly directed, this could make a spacecraft move.

DOES TIME END

Does time have a beginning?

Any universal concept of time must ultimately be based on the evolution of the cosmos itself. When you look up at the universe you're seeing events that happened in the past – it takes light time to reach us. In fact, even the simplest observation can help us understand cosmological time: for example the fact that the night sky is dark. If the universe had an infinite past and was infinite in extent, the night sky would be completely bright – filled with the light from an infinite number of stars in a cosmos that had always existed.

For a long time scientists, including Albert Einstein, thought that the universe was static and infinite. Observations have since shown that it is in fact expanding, and at an accelerating rate. This means that it must have originated from a more compact state that we call the Big Bang, implying that time does have a beginning. In fact, if we look for light that is old enough we can even see the relic radiation from Big Bang – the cosmic microwave background [CMB] . Realising this was a first step in determining the age of the universe

Time's arrow

So we know time most likely started during the Big Bang. But there is one nagging question that remains: what exactly is time?

To unpack this question, we have to look at the basic properties of space and time. In the dimension of space, you can move forwards and backwards; commuters experience this everyday. But time is different, it has a direction, you always move forward, never in reverse. So why is the dimension of time irreversible? This is one of the major unsolved problems in physics.

Imagine a box of gas in which all the particles were initially placed in one corner (an ordered state). Over time they would naturally seek to fill the entire box (a disordered state) – and to put the particles back into an ordered state would require energy. This is irreversible. It's like cracking an egg to make an omelette – once it spreads out and fills the frying pan, it will never go back to being egg-shaped. It's the same with the universe: as it evolves, the overall entropy increases.

AN EXAMPLE OF ENTROPY 

It turns out entropy is a pretty good way to explain time's arrow. And while it may seem like the universe is becoming more ordered rather than less – going from a wild sea of relatively uniformly spread out hot gas in its early stages to stars, planets, humans and articles about time – it's nevertheless possible that it is increasing in disorder. That's because the gravity associated with large masses may be pulling matter into seemingly ordered states – with the increase in disorder that we think must have taken place being somehow hidden away in the gravitational fields. So disorder could be increasing even though we don't see it.

But given nature's tendency to prefer disorder, why did the universe start off in such an ordered state in the first place? This is still considered a mystery. Some researchers argue that the Big Bang may not even have been the beginning, there may in fact be "parallel universes " where time runs in different directions." 

DOES ANY END OF TIME ?

As far as astrophysicists can tell, the universe is expanding at an accelerating rate, and will likely continue to do so indefinitely. But now some physicists are saying that this theory, called eternal inflation, and its implication that time is endless pose a problem for scientists calculating the probability of any event occurring. In a recent paper, they calculate that time is likely to end within the next 5 billion years due to some type of catastrophe that no one alive at the time will witness.

To see that this is not merely a philosophical point, it helps to consider cosmological experiments, where the rules are less clear. For example, one would like to predict or explain features of the CMB [cosmic microwave background]; or, in a theory with more than one vacuum, one might wish to predict the expected properties of the vacuum we find ourselves in, such as the Higgs mass. This requires computing the relative number of observations of different values for the Higgs mass, or of the CMB sky. There will be infinitely many instances of every possible observation, so what are the probabilities? This is known as the 'measure problem' of eternal inflation.

One solution to this problem, the physicists explain, is to conclude that time will eventually end. Then there would be a finite number of events that occur, with the improbable events occurring less often than the probable events.

The timing of this "cutoff" would define the set of allowed events. Thus, the physicists have attempted to calculate the probability of when time will end given five different cutoff measures. In two of these scenarios, time has a 50% chance of ending within 3.7 billion years. In two other scenarios, time has a 50% chance of ending within 3.3 billion years.

In the fifth and final scenario, the timescale is very short (on the order of the Planck time). In this scenario, the scientists calculated that "time would be overwhelmingly likely to end in the next second." Fortunately, this calculation predicts that most observers are "Boltzmann babies" who arise from quantum fluctuations in the early universe. Since most of us are not, the physicists could rule this scenario out "at a high level of confidence."

What would the end of time be like for observers around at the time? As the physicists explain, the observers would never see it coming. "The observer will necessarily run into the cutoff before observing the demise of any other system," the scientists write. They compare the boundary of the time cutoff to the horizon of a black hole.

The boundary ... can be treated as an object with physical attributes, including temperature, the authors write in their paper. Matter systems that encounter the end of time are thermalized at this horizon. This is similar to an outside observer's description of a matter system falling into a black hole. What is radically new, however, is the statement that we might experience thermalization upon crossing the black hole horizon. Yet the thermalizing "matter system" would still not notice anything unusual when crossing this horizon.

For those who feel uncomfortable about time ending, the physicists note that there are other solutions to the measure problem. They don't claim that their conclusion that time will end is correct, only that it follows logically from a set of assumptions. So perhaps one of the three assumptions underlying the conclusion is incorrect instead.

The first assumption is that the universe is eternally inflating, which is a consequence of general relativity and well supported by the experimental evidence so far observed. The second assumption is that the definition of probability is based on the relative frequency of an event, or what the scientists call the assumption of typicality. The third assumption is that, if spacetime is indeed infinite, then the only way to determine the probability of an event is to restrict one's attention to a finite subset of the infinite multiverse. Some other physicist have already looked into alternatives to this third assumption.