The Beauty of Physics

Dark Energy, Dark Matter

2011-07-19T11:43:00.003+07:00

In the early 1990's, one thing was fairly certain about the expansion of the Universe. It might have enough energy density to stop its expansion and recollapse, it might have so little energy density that it would never stop expanding, but gravity was certain to slow the expansion as time went on. Granted, the slowing had not been observed, but, theoretically, the Universe had to slow. The Universe is full of matter and the attractive force of gravity pulls all matter together. Then came 1998 and the Hubble Space Telescope (HST) observations of very distant supernovae that showed that, a long time ago, the Universe was actually expanding more slowly than it is today. So the expansion of the Universe has not been slowing due to gravity, as everyone thought, it has been accelerating. No one expected this, no one knew how to explain it. But something was causing it.

Eventually theorists came up with three sorts of explanations. Maybe it was a result of a long-discarded version of Einstein's theory of gravity, one that contained what was called a "cosmological constant." Maybe there was some strange kind of energy-fluid that filled space. Maybe there is something wrong with Einstein's theory of gravity and a new theory could include some kind of field that creates this cosmic acceleration. Theorists still don't know what the correct explanation is, but they have given the solution a name. It is called dark energy.

What Is Dark Energy?

More is unknown than is known. We know how much dark energy there is because we know how it affects the Universe's expansion. Other than that, it is a complete mystery. But it is an important mystery. It turns out that roughly 70% of the Universe is dark energy. Dark matter makes up about 25%. The rest - everything on Earth, everything ever observed with all of our instruments, all normal matter - adds up to less than 5% of the Universe. Come to think of it, maybe it shouldn't be called "normal" matter at all, since it is such a small fraction of the Universe.

This diagram reveals changes in the rate of expansion since the universe's birth 15 billion years ago. The more shallow the curve, the faster the rate of expansion. The curve changes noticeably about 7.5 billion years ago, when objects in the universe began flying apart as a faster rate. Astronomers theorize that the faster expansion rate is due to a mysterious, dark force that is pulling galaxies apart.
NASA/STSci/Ann Feild

One explanation for dark energy is that it is a property of space. Albert Einstein was the first person to realize that empty space is not nothing. Space has amazing properties, many of which are just beginning to be understood. The first property that Einstein discovered is that it is possible for more space to come into existence. Then one version of Einstein's gravity theory, the version that contains a cosmological constant, makes a second prediction: "empty space" can possess its own energy. Because this energy is a property of space itself, it would not be diluted as space expands. As more space comes into existence, more of this energy-of-space would appear. As a result, this form of energy would cause the Universe to expand faster and faster. Unfortunately, no one understands why the cosmological constant should even be there, much less why it would have exactly the right value to cause the observed acceleration of the Universe.

These four dwarf galaxies are part of a census of small galaxies in the tumultuous heart of the nearby Perseus galaxy cluster. The galaxies appear smooth and symmetrical, suggesting that they have not been tidally disrupted by the pull of gravity in the dense cluster environment. Larger galaxies around them, however, are being ripped apart by the gravitational tug of other galaxies.

Another explanation for how space acquires energy comes from the quantum theory of matter. In this theory, "empty space" is actually full of temporary ("virtual") particles that continually form and then disappear. But when physicists tried to calculate how much energy this would give empty space, the answer came out wrong - wrong by a lot. The number came out 10120 times too big. That's a 1 with 120 zeros after it. It's hard to get an answer that bad. So the mystery continues.

Another explanation for dark energy is that it is a new kind of dynamical energy fluid or field, something that fills all of space but something whose effect on the expansion of the Universe is the opposite of that of matter and normal energy. Some theorists have named this "quintessence," after the fifth element of the Greek philosophers. But, if quintessence is the answer, we still don't know what it is like, what it interacts with, or why it exists. So the mystery continues.

A last possibility is that Einstein's theory of gravity is not correct. That would not only affect the expansion of the Universe, but it would also affect the way that normal matter in galaxies and clusters of galaxies behaved. This fact would provide a way to decide if the solution to the dark energy problem is a new gravity theory or not: we could observe how galaxies come together in clusters. But if it does turn out that a new theory of gravity is needed, what kind of theory would it be? How could it correctly describe the motion of the bodies in the Solar System, as Einstein's theory is known to do, and still give us the different prediction for the Universe that we need? There are candidate theories, but none are compelling. So the mystery continues.

The thing that is needed to decide between dark energy possibilities - a property of space, a new dynamic fluid, or a new theory of gravity - is more data, better data.

What Is Dark Matter?

By fitting a theoretical model of the composition of the Universe to the combined set of cosmological observations, scientists have come up with the composition that we described above, ~70% dark energy, ~25% dark matter, ~5% normal matter. What is dark matter?

One of the most complicated and dramatic collisions between galaxy clusters ever seen is captured in this new composite image of Abell 2744. The blue shows a map of the total mass concentration (mostly dark matter).

We are much more certain what dark matter is not than we are what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the Universe to make up the 25% required by the observations. Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them. Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter. Finally, we can rule out large galaxy-sized black holes on the basis of how many gravitational lenses we see. High concentrations of matter bend light passing near them from objects further away, but we do not see enough lensing events to suggest that such objects to make up the required 25% dark matter contribution.

However, at this point, there are still a few dark matter possibilities that are viable. Baryonic matter could still make up the dark matter if it were all tied up in brown dwarfs or in small, dense chunks of heavy elements. These possibilities are known as massive compact halo objects, or "MACHOs". But the most common view is that dark matter is not baryonic at all, but that it is made up of other, more exotic particles like axions or WIMPS (Weakly Interacting Massive Particles).

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Wormhole

2011-07-05T23:06:00.004+07:00

A wormhole is a theoretical entity allowed by Einstein's theory of general relativity in which spacetime curvature connects two distant locations (or times).

The term wormhole, first introduced by American theoretical physicist John A. Wheeler in 1957, based on an analogy of how a worm could make a hole from one end of an apple through the center to the other end, thus creating a "shortcut" through the intervening space. The picture simplified illustrate of how this would work in linking two areas of two-dimensional space.

The most common concept of a wormhole is an Einstein-Rosen bridge, first formalized by Albert Einstein and his colleague Nathan Rosen in 1935. In 1962, John A. Wheeler and Robert W. Fuller were able to prove that such a wormhole would collapse instantly upon formation, so not even light would make it through. (A similar proposal was later resurrected by Robert Hjellming in 1971, when he presented a model in which a black hole would draw matter in while being connected to a white hole in a distant location, which expels this same matter.)

In a 1988 paper, physicists Kip Thorne and Mike Morris proposed since that such a wormhole could be made stable by containing some form of negative matter or energy (sometimes called exotic matter). Other types of traversible wormholes have also been proposed as valid solutions to the general relativity field equations.

Some solutions to the general relativity field equations have suggested that wormholes could also be created to connect different times, as well as distant space. Still other possibilities have been proposed of wormholes connecting to whole other universes.

There is still much speculation on whether it is possible for wormholes to actually exist and, if so, what properties they would actually possess.

The Einstein-Rosen Bridge

2011-06-29T23:51:00.000+07:00

In 1916 Einstein first introduced his general theory of relativity, a theory which to this day remains the standard model for gravitation. Twenty years later, he and his long-time collaborator Nathan Rosen published a paper "In Physical Review 48, 73 (1935)" showing that implicit in the general relativity formalism is a curved-space structure that can join two distant regions of space-time through a tunnel-like curved spatial shortcut. The purpose of the paper of Einstein and Rosen was not to promote faster-than-light or inter-universe travel, but to attempt to explain fundamental particles like electrons as space-tunnels threaded by electric lines of force. The Einstein-Rosen Bridge is based on generally relativity and work done by Schwarzschild in solving Einstein’s equations; one of the solutions to these equations was the prediction of black holes.

A black hole is a region of space-time from which nothing can escape, even light. It can be said that black holes are really just the evolutionary end point of massive stars. But somehow, this simple explanation makes them no easier to understand or less mysterious.

Black holes are the evolutionary endpoints of stars at least 10 to 15 times as massive as the Sun. If a star that massive or larger undergoes a supernova explosion, it can leave behind a fairly massive burned out stellar remnant. With no outward forces to oppose gravitational forces, the remnant will collapse in on itself. The star eventually collapses to the point of zero volume and infinite density, creating what is known as a “singularity”. As the density increases, the path of light rays emitted from the star are bent and eventually wrapped irrevocably around the star. Any emitted photons are trapped into an orbit by the intense gravitational field; they will never leave it. Because no light escapes after the star reaches this infinite density, it is called a black hole.

The basic idea of wormholes dates nearly as far back as the concept of general relativity. Barely a few months after Einstein wrote down his equations, the first exact solution of the Einstein equations was found by Karl Schwarzschild[3]. One of the remarkable predictions of Schwarzschild's geometry was that if a mass, M, were compressed inside a critical radius, rs, nowadays called the Schwarzschild radius[4] (the farthest visible point), and then its gravity would become so strong that not even light could escape. The Schwarzschild radius, rs, of a mass, M, is given by

Curiously, the Schwarzschild radius had already been derived (with the correct result, but an incorrect theory) by John Michell in 1784. The English geologist realized that it would be theoretically possible for gravity to be so overwhelmingly strong that nothing, not even light[6] could escape. To generate such gravity, an object would have to be very massive and unimaginably dense. At the time, the necessary conditions for "dark stars", as Michell called them, seemed physically impossible. His ideas were published by the French mathematician and philosopher Pierre Simon Laplace in two successive editions of an astronomy guide, but were dropped from the third edition. In Laplace's 1795 edition, he put forward the following equation saying what the mass and radius would have to be to form a black hole.

The complete Schwarzschild geometry consists of a black hole, a white hole, and two Universes connected at their horizons by a wormhole. The name "black hole" was invented in 1968 by John Archibald Wheeler. Before Wheeler, these objects were often referred to as ‘black stars’ or ‘frozen stars’.

It was Austrian Ludwig Flamm who had realised that Schwarzschild's solution (called the Schwarzschild Metric) to Einstein's equations actually describes a wormhole connecting two regions of flat space-time; two universes, or two parts of the same universe.

A white hole (from the negative square root solution inside the horizon) is a black hole running backwards in time. Just as black holes swallow things irretrievably, so white holes spit them out. However white holes cannot exist, since they violate the second law of thermodynamics.

General Relativity is time symmetric. It does not know about the second law of thermodynamics, and it does not know about which way cause and effect go. However we do. The negative square root solution outside the horizon represents another Universe. The wormhole joining the two separate Universes is known as the Einstein-Rosen Bridge.

The prediction of the existence of black holes did not trouble Einstein, but he found that the black holes contained a singularity at its centre; this is a point of infinite density where time comes to an end. At the point of the singularity, all the known laws of physics start to breakdown. For Einstein this was a very troubling thought and he did not like them, the idea that they were shielding from the outside world by the event horizon of the black hole was not enough for him and he did not like the “concept that if you can not see it then do not worry about it.”

So he went to work with Nathan Rosen and in 1935 they produced a paper that produced evidence for a bridge between a black hole and a white hole, this was called the Einstein-Rosen Bridge.

Figure 1

The purpose of the paper of Einstein and Rosen was not to promote faster-than-light or inter-universe travel, but to attempt to explain fundamental particles like electrons as space-tunnels threaded by electric lines of force. However science fiction took the idea of Einstein-Rosen Bridges and applied it to moving spaceships faster than the speed of light through what was now being called ‘wormholes’. So what Einstein originally theorised was now being used by science fiction writers to get around the problems with not being able to go faster than the speed of light that Einstein’s General Relativity had inflicted upon them. The diagram (figure 1) shows an Einstein-Rosen Bridge with a spaceship entering the wormhole. However in the Einstein-Rosen theory the idea of objects larger than electrons being able to pass through a wormhole was not even considered and so the scenario that science fiction writers portray about the Einstein-Rosen Bridge is not correct.

The Einstein-Rosen work was disturbing to many physicists of the time because such a ‘tunnel’ through space-time, could in principle allow the transmission of information faster than the speed of light in violation of one of the key postulates of special relativity known as ‘Einsteinian causality’.

In 1962 John Wheeler discovered that the Einstein-Rosen bridge space-time structure was dynamically unstable in field-free space. They showed that if such a wormhole somehow opened, it would close up again before even a single photon could be transmitted through it, thereby preserving Einsteinian causality.

This work lead there to being two different classifications of wormholes: Lorentzian wormholes and Euclidean wormholes.

Lorentzian wormholes are essentially short cuts through space and time but they instantaneously close unless some form of negative energy can hold them open. It is possible to produce small amounts of negative energy in the laboratory by a principle known as the Casimir effect. However this energy would not be enough to keep open a wormhole.

A by product of Lorentzian wormholes would be that objects passing through them would not only be moved spatially but also temporally (assuming parallel universes exist).

Lorentzian wormholes come in at least two varieties:

1) Inter-universe wormholes, wormholes that connect ‘our’ universe with ‘another’ universe (Figure 2).

2) Intra-universe wormholes, wormholes that connect two distant regions of our universe with each other (Figure 3).


Figure 2	Figure 3

Euclidean wormholes are even stranger given that they live in "imaginary time" and are intrinsically virtual quantum mechanical processes. These Euclidean wormholes are of interest mainly to quantum field theorists.

In 1865 when there was no relativity, quantum mechanics and modern cosmology Charles Dodgson[14] wrote Alice in Wonderland a children’s story on the subject of parallel universes. There is a famous part of the story when Alice chases the white rabbit down a hole, this hole could now be described as an Einstein-Rosen Bridge. In Wonderland the laws of physics in this universe no longer applied and so strange processes could take place. It is however important to remember that Dodgson would not have known what type of mechanism would allow this to happen. In fact this idea, of using a ‘wormhole’ to travel large distances was used by Sagan in writing a novel ‘Contact’ in 1985. In his novel he wanted a method of moving a character faster than the speed of light though not in a manner violating Relativity.

Unfortunately, worm holes are currently more science fiction than they are science fact. A wormhole is a theoretical opening in space-time that is the mathematical solution to general relativity. If one day this was proven it could be used to travel to far away locations very quickly. It has never been proven that worm holes exist and there is no experimental evidence for them (due to black holes being hard to detect), but it is certainly testing to think about the possibilities their existence might create.

References

Introduction to Relativistic Gravitation, Rémi Hakim

Hyperspace, Michio Kaku

The Cosmic Frontiers of Relativity, Kaufmann

Black Holes, Wormholes and Time Machines, Jim Al-Khalili

Physics of Black Holes, Igor D. Novikov and Valery P. Frolov

Cosmological Physics, John A. Peacock
Black Holes: A traveler’s guide, Clifford A. Pickover
Lorentzian Wormholes, Matt Visser
Einstein Rosen Bridge

FTL ( Faster Than Light)

2011-06-10T13:45:00.000+07:00

In a Stargate Universe movie, we know about FTL. Faster-than-light travel. Hyperspace travel is the most common type of F.T.L. in the Stargate universe, but it is not the only type. The Ancient exploratory vessel Destiny uses a never-before-seen kind of F.T.L. travel.
That is a short brief history in Stargate Universe.

But, is there any speed which is faster than light in our space time ?

It is a well-known fact that nothing can travel faster than the speed of light. At best, a massless particle travels at the speed of light. But is this really true? In 1962, Bilaniuk, Deshpande, and Sudarshan, Am. J. Phys. 30, 718 (1962), said "no". A very readable paper is Bilaniuk and Sudarshan, Phys. Today 22,43 (1969). I give here a brief overview.

Draw a graph, with momentum (p) on the x-axis, and energy (E) on the y-axis. Then draw the "light cone", two lines with the equations E = +/− p. This divides our 1+1 dimensional space-time into two regions. Above and below are the "timelike" quadrants, and to the left and right are the "spacelike" quadrants.

Now the fundamental fact of relativity is that E² − p² = m². (Let's take c=1 for the rest of the discussion.) For any non-zero value of m (mass), this is a hyperbola with branches in the timelike regions. It passes through the point (p,E) = (0,m), where the particle is at rest. Any particle with mass m is constrained to move on the upper branch of this hyperbola. (Otherwise, it is "off-shell", a term you hear in association with virtual particles — but that's another topic.) For massless particles, E² = p², and the particle moves on the light-cone.

These two cases are given the names tardyon (or bradyon in more modern usage) and luxon, for "slow particle" and "light particle". Tachyon is the name given to the supposed "fast particle" which would move with v>c. (Tachyons were first introduced into physics by Gerald Feinberg, in his seminal paper "On the possibility of faster-than-light particles" [Phys. Rev. 159, 1089—1105 (1967)]).

Now another familiar relativistic equation is E = m*[1−(v/c)²]^−1/2. Tachyons (if they exist) have v > c. This means that E is imaginary! Well, what if we take the rest mass m, and take it to be imaginary? Then E is negative real, and E² − p² = m² < 0. Or, p² − E² = M², where M is real. This is a hyperbola with branches in the spacelike region of spacetime. The energy and momentum of a tachyon must satisfy this relation.

You can now deduce many interesting properties of tachyons. For example, they accelerate (p goes up) if they lose energy (E goes down). Furthermore, a zero-energy tachyon is "transcendent", or infinitely fast. This has profound consequences. For example, let's say that there were electrically charged tachyons. Since they would move faster than the speed of light in the vacuum, they should produce Cherenkov radiation. This would lower their energy, causing them to accelerate more! In other words, charged tachyons would probably lead to a runaway reaction releasing an arbitrarily large amount of energy. This suggests that coming up with a sensible theory of anything except free (noninteracting) tachyons is likely to be difficult. Heuristically, the problem is that we can get spontaneous creation of tachyon-antitachyon pairs, then do a runaway reaction, making the vacuum unstable. To treat this precisely requires quantum field theory, which gets complicated. It is not easy to summarize results here. However, one reasonably modern reference is Tachyons, Monopoles, and Related Topics, E. Recami, ed. (North-Holland, Amsterdam, 1978).

However, tachyons are not entirely invisible. You can imagine that you might produce them in some exotic nuclear reaction. If they are charged, you could "see" them by detecting the Cherenkov light they produce as they speed away faster and faster. Such experiments have been done. So far, no tachyons have been found. Even neutral tachyons can scatter off normal matter with experimentally observable consequences. Again, no such tachyons have been found.

How about using tachyons to transmit information faster than the speed of light, in violation of Special Relativity? It's worth noting that when one considers the relativistic quantum mechanics of tachyons, the question of whether they "really" go faster than the speed of light becomes much more touchy! In this framework, tachyons are waves that satisfy a wave equation. Let's treat free tachyons of spin zero, for simplicity. We'll set c = 1 to keep things less messy. The wavefunction of a single such tachyon can be expected to satisfy the usual equation for spin-zero particles, the Klein-Gordon equation:

(BOX + m²)phi = 0

where BOX is the D'Alembertian, which in 3+1 dimensions is just

BOX = (d/dt)² − (d/dx)² − (d/dy)² − (d/dz)².

The difference with tachyons is that m² is negative, and m is imaginary.

To simplify the math a bit, let's work in 1+1 dimensions, with co-ordinates x and t, so that

BOX = (d/dt)² − (d/dx)²

Everything we'll say generalizes to the real-world 3+1-dimensional case. Now, regardless of m, any solution is a linear combination, or superposition, of solutions of the form

phi(t,x) = exp(−iEt + ipx)

where E² − p² = m². When m² is negative there are two essentially different cases. Either |p| >= |E|, in which case E is real and we get solutions that look like waves whose crests move along at the rate |p|/|E| >= 1, i.e., no slower than the speed of light. Or |p| < |E|, in which case E is imaginary and we get solutions that look waves that amplify exponentially as time passes!

We can decide as we please whether or not we want to consider the second sort of solutions. They seem weird, but then the whole business is weird, after all.

1) If we do permit the second sort of solution, we can solve the Klein-Gordon equation with any reasonable initial data — that is, any reasonable values of phi and its first time derivative at t = 0. (For the precise definition of "reasonable", consult your local mathematician.) This is typical of wave equations. And, also typical of wave equations, we can prove the following thing: If the solution phi and its time derivative are zero outside the interval [−L,L] when t = 0, they will be zero outside the interval [−L−|t|, L+|t|] at any time t. In other words, localized disturbances do not spread with speed faster than the speed of light! This seems to go against our notion that tachyons move faster than the speed of light, but it's a mathematical fact, known as "unit propagation velocity".

2) If we don't permit the second sort of solution, we can't solve the Klein-Gordon equation for all reasonable initial data, but only for initial data whose Fourier transforms vanish in the interval [−|m|,|m|]. By the Paley-Wiener theorem this has an odd consequence: it becomes impossible to solve the equation for initial data that vanish outside some interval [−L,L]! In other words, we can no longer "localize" our tachyon in any bounded region in the first place, so it becomes impossible to decide whether or not there is "unit propagation velocity" in the precise sense of part 1). Of course, the crests of the waves exp(−iEt + ipx) move faster than the speed of light, but these waves were never localized in the first place!

The bottom line is that you can't use tachyons to send information faster than the speed of light from one place to another. Doing so would require creating a message encoded some way in a localized tachyon field, and sending it off at superluminal speed toward the intended receiver. But as we have seen you can't have it both ways: localized tachyon disturbances are subluminal and superluminal disturbances are nonlocal.

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Einstein - Biography

2011-05-10T11:59:00.000+07:00

Albert Einstein was born at Ulm, in Württemberg, Germany, on March 14, 1879. Six weeks later the family moved to Munich, where he later on began his schooling at the Luitpold Gymnasium. Later, they moved to Italy and Albert continued his education at Aarau, Switzerland and in 1896 he entered the Swiss Federal Polytechnic School in Zurich to be trained as a teacher in physics and mathematics. In 1901, the year he gained his diploma, he acquired Swiss citizenship and, as he was unable to find a teaching post, he accepted a position as technical assistant in the Swiss Patent Office. In 1905 he obtained his doctor's degree.

During his stay at the Patent Office, and in his spare time, he produced much of his remarkable work and in 1908 he was appointed Privatdozent in Berne. In 1909 he became Professor Extraordinary at Zurich, in 1911 Professor of Theoretical Physics at Prague, returning to Zurich in the following year to fill a similar post. In 1914 he was appointed Director of the Kaiser Wilhelm Physical Institute and Professor in the University of Berlin. He became a German citizen in 1914 and remained in Berlin until 1933 when he renounced his citizenship for political reasons and emigrated to America to take the position of Professor of Theoretical Physics at Princeton*. He became a United States citizen in 1940 and retired from his post in 1945.

After World War II, Einstein was a leading figure in the World Government Movement, he was offered the Presidency of the State of Israel, which he declined, and he collaborated with Dr. Chaim Weizmann in establishing the Hebrew University of Jerusalem.

Einstein always appeared to have a clear view of the problems of physics and the determination to solve them. He had a strategy of his own and was able to visualize the main stages on the way to his goal. He regarded his major achievements as mere stepping-stones for the next advance.

At the start of his scientific work, Einstein realized the inadequacies of Newtonian mechanics and his special theory of relativity stemmed from an attempt to reconcile the laws of mechanics with the laws of the electromagnetic field. He dealt with classical problems of statistical mechanics and problems in which they were merged with quantum theory: this led to an explanation of the Brownian movement of molecules. He investigated the thermal properties of light with a low radiation density and his observations laid the foundation of the photon theory of light.

In his early days in Berlin, Einstein postulated that the correct interpretation of the special theory of relativity must also furnish a theory of gravitation and in 1916 he published his paper on the general theory of relativity. During this time he also contributed to the problems of the theory of radiation and statistical mechanics.

In the 1920's, Einstein embarked on the construction of unified field theories, although he continued to work on the probabilistic interpretation of quantum theory, and he persevered with this work in America. He contributed to statistical mechanics by his development of the quantum theory of a monatomic gas and he has also accomplished valuable work in connection with atomic transition probabilities and relativistic cosmology.

After his retirement he continued to work towards the unification of the basic concepts of physics, taking the opposite approach, geometrisation, to the majority of physicists.

Einstein's researches are, of course, well chronicled and his more important works include Special Theory of Relativity (1905), Relativity (English translations, 1920 and 1950), General Theory of Relativity (1916), Investigations on Theory of Brownian Movement (1926), and The Evolution of Physics (1938). Among his non-scientific works, About Zionism (1930), Why War? (1933), My Philosophy (1934), and Out of My Later Years (1950) are perhaps the most important.

Albert Einstein received honorary doctorate degrees in science, medicine and philosophy from many European and American universities. During the 1920's he lectured in Europe, America and the Far East, and he was awarded Fellowships or Memberships of all the leading scientific academies throughout the world. He gained numerous awards in recognition of his work, including the Copley Medal of the Royal Society of London in 1925, and the Franklin Medal of the Franklin Institute in 1935.

Einstein's gifts inevitably resulted in his dwelling much in intellectual solitude and, for relaxation, music played an important part in his life. He married Mileva Maric in 1903 and they had a daughter and two sons; their marriage was dissolved in 1919 and in the same year he married his cousin, Elsa Löwenthal, who died in 1936. He died on April 18, 1955 at Princeton, New Jersey.

From Nobel Lectures, Physics 1901-1921, Elsevier Publishing Company, Amsterdam, 1967

This autobiography/biography was written at the time of the award and first published in the book series Les Prix Nobel. It was later edited and republished in Nobel Lectures. To cite this document, always state the source as shown above.

Warner Heisenberg - Biography

2011-05-07T11:59:00.016+07:00

Werner Heisenberg was born on 5th December, 1901, at Würzburg. He was the son of Dr. August Heisenberg and his wife Annie Wecklein. His father later became Professor of the Middle and Modern Greek languages in the University of Munich. It was probably due to his influence that Heisenberg remarked, when the Japanese physicist Yukawa discovered the particle now known as the meson and the term "mesotron" was proposed for it, that the Greek word "mesos" has no "tr" in it, with the result that the name "mesotron" was changed to "meson".

Heisenberg went to the Maximilian school at Munich until 1920, when he went to the University of Munich to study physics under Sommerfeld, Wien, Pringsheim, and Rosenthal. During the winter of 1922-1923 he went to Göttingen to study physics under Max Born, Franck, and Hilbert. In 1923 he took his Ph.D. at the University of Munich and then became Assistant to Max Born at the University of Göttingen, and in 1924 he gained the venia legendi at that University.

From 1924 until 1925 he worked, with a Rockefeller Grant, with Niels Bohr, at the University of Copenhagen, returning for the summer of 1925 to Göttingen.

In 1926 he was appointed Lecturer in Theoretical Physics at the University of Copenhagen under Niels Bohr and in 1927, when he was only 26, he was appointed Professor of Theoretical Physics at the University of Leipzig.

In 1929 he went on a lecture tour to the United States, Japan, and India.

In 1941 he was appointed Professor of Physics at the University of Berlin and Director of the Kaiser Wilhelm Institute for Physics there.

At the end of the Second World War he, and other German physicists, were taken prisoner by American troops and sent to England, but in 1946 he returned to Germany and reorganized, with his colleagues, the Institute for Physics at Göttingen. This Institute was, in 1948, renamed the Max Planck Institute for Physics.

In 1948 Heisenberg stayed for some months in Cambridge, England, to give lectures, and in 1950 and 1954 he was invited to lecture in the United States. In the winter of 1955-1956 he gave the Gifford Lectures at the University of St. Andrews, Scotland, these lectures being subsequently published as a book.

During 1955 Heisenberg was occupied with preparations for the removal of the Max Planck Institute for Physics to Munich. Still Director of this Institute, he went with it to Munich and in 1958 he was appointed Professor of Physics in the University of Munich. His Institute was then being renamed the Max Planck Institute for Physics and Astrophysics.

Heisenberg's name will always be associated with his theory of quantum mechanics, published in 1925, when he was only 23 years old. For this theory and the applications of it which resulted especially in the discovery of allotropic forms of hydrogen, Heisenberg was awarded the Nobel Prize for Physics for 1932.

His new theory was based only on what can be observed, that is to say, on the radiation emitted by the atom. We cannot, he said, always assign to an electron a position in space at a given time, nor follow it in its orbit, so that we cannot assume that the planetary orbits postulated by Niels Bohr actually exist. Mechanical quantities, such as position, velocity, etc. should be represented, not by ordinary numbers, but by abstract mathematical structures called "matrices" and he formulated his new theory in terms of matrix equations.

Later Heisenberg stated his famous principle of uncertainty, which lays it down that the determination of the position and momentum of a mobile particle necessarily contains errors the product of which cannot be less than the quantum constant h and that, although these errors are negligible on the human scale, they cannot be ignored in studies of the atom.

From 1957 onwards Heisenberg was interested in work on problems of plasma physics and thermonuclear processes, and also much work in close collaboration with the International Institute of Atomic Physics at Geneva. He was for several years Chairman of the Scientific Policy Committee of this Institute and subsequently remained a member of this Committee.

When he became, in 1953, President of the Alexander von Humboldt Foundation, he did much to further the policy of this Foundation, which was to invite scientists from other countries to Germany and to help them to work there.

Since 1953 his own theoretical work was concentrated on the unified field theory of elementary particles which seems to him to be the key to an understanding of the physics of elementary particles.

Apart from many medals and prizes, Heisenberg received an honorary doctorate of the University of Bruxelles, of the Technological University Karlsruhe, and recently (1964) of the University of Budapest; he is also recipient of the Order of Merit of Bavaria, and the Grand Cross for Federal Services with Star (Germany). He is a Fellow of the Royal Society of London and a Knight of the Order of Merit (Peace Class). He is a member of the Academies of Sciences of Göttingen, Bavaria, Saxony, Prussia, Sweden, Rumania, Norway, Spain, The Netherlands, Rome (Pontificial), the German Akademie der Naturforscher Leopoldina (Halle), the Accademia dei Lincei (Rome), and the American Academy of Sciences. During 1949-1951 he was President of the Deutsche Forschungsrat (German Research Council) and in 1953 he became President of the Alexander von Humboldt Foundation.

One of his hobbies is classical music: he is a distinguished pianist. In 1937 Heisenberg married Elisabeth Schumacher. They have seven children, and live in Munich.

From Nobel Lectures, Physics 1922-1941, Elsevier Publishing Company, Amsterdam, 1965

This autobiography/biography was written at the time of the award and first published in the book series Les Prix Nobel. It was later edited and republished in Nobel Lectures. To cite this document, always state the source as shown above.

Werner Heisenberg died on February 1, 1976.

Space-Time Continuum in Reality Part I

2011-05-04T23:56:00.002+07:00

Gravity is stronger on the surface of the earth than in space, but on the surface of the sun's gravity is stronger again. Atomic clocks in the sun will run slower than on Earth, about one minute per year. Because of the strong gravity in the sun, the light coming from the atoms in the sun will look 'more red' which indicate a lower frequency than on earth. French astronomers have discovered this at the time of their investigation in 1962. Red shit gravity is one of Einstein's theory of gravity estimate.

Similarly, the white dwarf stars that collapse. They have a very strong gravity. Astronomers have mendetesi redhift on white dwarf stars. On earth, time will run slower on the surface than at the top of a skyscraper. Today we can see what happens when a ball fell to the ground. Newton said that it happened because of gravity pulling, causing the ball is accelerating when it fell to the ground. But Einstein had a different opinion regarding this. Einstein argued, the atomic clock and light vibrates more slowly in the region with strong gravity. Because the relationship between energy and frequency, the atoms in the earth's surface has a smaller energy than he had when the atoms are located in space far from the source of gravity. A ball made of atoms will have a smaller energy when the ball is located on top of a tower. Therefore, the mass of the ball still will be reduced in accordance with Einstein's equations.

Suppose there is a ball that was free falling toward the ground. From time to time the ball entered the 'skin-skin time' is an increasingly slower. During the ball in free fall, 'no' forces acting on it. Since there is no force acting on the ball, the ball does not gain or lose energy. But the silence of the ball will lose energy due to enter the area with a slower time (areas with a stronger gravity).

Therefore, the ball should get some energy in another form that makes it have the same mass as before. The only way to compensate for lost energy silence (which means equivalent to the mass of silence) is to move faster. Total energy for the ball it fixed, then the ball should move with the acceleration fixed, ie, 9.8 meter per second per second (which by Newton referred to as the acceleration of gravity)

Difference beetwen General and Special Theory of Relativity

2011-05-01T00:01:00.002+07:00

THE BASAL principle, which was the pivot of all our previous considerations, was the special principle of relativity, i.e. the principle of the physical relativity of all uniform motion. Let us once more analyse its meaning carefully

It was at all times clear that, from the point of view of the idea it conveys to us, every motion must only be considered as a relative motion. Returning to the illustration we have frequently used of the embankment and the railway carriage, we can express the fact of the motion here taking place in the following two forms, both of which are equally justifiable:

1. The carriage is in motion relative to the embankment.

2. The embankment is in motion relative to the carriage.

In (a) the embankment, in (b) the carriage, serves as the body of reference in our statement of the motion taking place. If it is simply a question of detecting or of describing the motion involved, it is in principle immaterial to what reference-body we refer the motion. As already mentioned, this is self-evident, but it must not be confused with the much more comprehensive statement called “the principle of relativity,” which we have taken as the basis of our investigations.

The principle we have made use of not only maintains that we may equally well choose the carriage or the embankment as our reference-body for the description of any event (for this, too, is self-evident). Our principle rather asserts what follows: If we formulate the general laws of nature as they are obtained from experience, by making use of

1. the embankment as reference-body,

2. the railway carriage as reference-body,

then these general laws of nature (e.g. the laws of mechanics or the law of the propagation of light in vacuo) have exactly the same form in both cases. This can also be expressed as follows: For the physical description of natural processes, neither of the reference-bodies K, K' is unique (lit. “specially marked out”) as compared with the other. Unlike the first, this latter statement need not of necessity hold a priori; it is not contained in the conceptions of “motion” and “reference body” and derivable from them; only experience can decide as to its correctness or incorrectness

Up to the present, however, we have by no means maintained the equivalence of all bodies of reference K in connection with the formulation of natural laws. Our course was more on the following lines. In the first place, we started out from the assumption that there exists a reference-body K, whose condition of motion is such that the Galileian law holds with respect to it: A particle left to itself and sufficiently far removed from all other particles moves uniformly in a straight line. With reference to K (Galileian reference-body) the laws of nature were to be as simple as possible. But in addition to K, all bodies of reference K' should be given preference in this sense, and they should be exactly equivalent to K for the formulation of natural laws, provided that they are in a state of uniform rectilinear and non-rotary motion with respect to K; all these bodies of reference are to be regarded as Galileian reference-bodies. The validity of the principle of relativity was assumed only for these reference-bodies, but not for others (e.g. those possessing motion of a different kind). In this sense we speak of the special principle of relativity, or special theory of relativity.

In contrast to this we wish to understand by the “general principle of relativity” the following statement: All bodies of reference K, K', etc., are equivalent for the description of natural phenomena (formulation of the general laws of nature), whatever may be their state of motion. But before proceeding farther, it ought to be pointed out that this formulation must be replaced later by a more abstract one, for reasons which will become evident at a later stage.

Since the introduction of the special principle of relativity has been justified, every intellect which strives after generalisation must feel the temptation to venture the step towards the general principle of relativity. But a simple and apparently quite reliable consideration seems to suggest that, for the present at any rate, there is little hope of success in such an attempt. Let us imagine ourselves transferred to our old friend the railway carriage, which is travelling at a uniform rate. As long as it is moving uniformly, the occupant of the carriage is not sensible of its motion, and it is for this reason that he can un-reluctantly interpret the facts of the case as indicating that the carriage is at rest, but the embankment in motion. Moreover, according to the special principle of relativity, this interpretation is quite justified also from a physical point of view.

If the motion of the carriage is now changed into a non-uniform motion, as for instance by a powerful application of the brakes, then the occupant of the carriage experiences a correspondingly powerful jerk forwards. The retarded motion is manifested in the mechanical behaviour of bodies relative to the person in the railway carriage. The mechanical behaviour is different from that of the case previously considered, and for this reason it would appear to be impossible that the same mechanical laws hold relatively to the non-uniformly moving carriage, as hold with reference to the carriage when at rest or in uniform motion. At all events it is clear that the Galileian law does not hold with respect to the non-uniformly moving carriage. Because of this, we feel compelled at the present juncture to grant a kind of absolute physical reality to non-uniform motion, in opposition to the general principle of relativity. But in what follows we shall soon see that this conclusion cannot be maintained.

read more : bartleby.com

Space-Time Continuum in General Relativity Theory

2011-04-28T00:02:00.002+07:00

In the theory of general relativity, Einstein's gravitational force illustrated that as a result of the curvature of space-time continuum. The presence of objects with mass can warp space-time continuum. Depictions of these ideas include the idea of space-time in four dimensions. To be able to understand it, we describe it in two-dimensional object. Imagine a rubber sheet where there is a heavy iron ball on top of it. Then the rubber sheet would be distorted and warped. As this is the Einstein model the curved space-time due to the presence of matter, just that Einstein spacetime has four dimensions.

When we roll a marble across a flat rubber sheet, the marbles will be moving to take a straight path. However, if the rubber sheet is warped by the presence of a heavy iron ball, then roll marbles that we will move to take a curved path around a curve to exist on the rubber sheet. Einstein stated that effects like these that led to 'force' of gravity. But the real 'force', this is not the style that has the equation F = ma.

Curved trajectory is because the marbles are marbles that will take the path with the smallest obstacle in space and time. Trajectory is known by the name of the "geodesic" track. Not only the marble that can be experienced track like this, planets and even light, can also be experienced when walking through an area that has a strong gravity. Actually, these objects travel in straight trajectories of four-dimensional spacetime, but seemed to move the curve because we see it from three dimensions.

fig: geodesic track that make by light in space time continuum

The theory of general relativity which Einstein wrote three estimates put forward that can be tested, namely perihelion motion of Mercury, bending of the light path due to the presence of the body of mass and length and timing behavior in the gravitational field that became known as 'red shift’.

Special Relativity and the Weirdness

2011-04-25T00:05:00.004+07:00

In the theory of special relativity, the speed of light is always the same for every observer (300,000 km per second). The speed of light is not dependent on the motion of the observer or light source motion. And this is a concept that can not be accepted by the logic.

If I move through you with a high speed, then you will see that my time clock will run slower than the bell of your time. This will become clearer if I was an astronaut who was in one of two spacecraft flying side by side with equal speed. When I look out the window, I saw other spacecraft are still to my plane, while in the background, the earth seemed to move towards me. Then I decided to measure the distance between my plane and my friend plane with a laser beam. I sent a laser light that moves with the speed of light and measure the time to laser return again with my atomic clock. Laser light that I send will travel straight and direct path back to me via a straight path as well.

But the plane was on earth not seen anything like this. During a moment when the laser beam that I send from my plane was moving toward the plane of my colleagues, observers on Earth saw my colleague’s plane have moved forward. Meanwhile, the reflected laser beam will reach my plane which also has moved far ahead. As a result, the laser beam path is not straight, but zig-zag shaped. Therefore, according to observers on earth, the light beam has traveled a greater distance than I observe.

figure A : a laser beam observed from plane.

figure B : a laser beam observed from earth.

If the spacecraft speed is not too high, then the observed difference in distance will be very small. However, if the aircraft speed is high enough, say half the speed of light, then the observer on earth will see the laser beam passes over a length of about 20% compared with the trajectory that I observed. Keep in mind that the speed of light is the same for every observer. Therefore, the travel wakktu laser light beam to leave and go home if observed by the observers of the earth will have more time about 20% compared to the measurement of time which I do on the plane.

The speed of light in empty space that is not affected by the speed of the source is relaivitas interesting aspect, it also never been confirmed by Albert Michelson and Edward Morley in Cleveland circa the 1880s. It also found that there is no any objects that could move beyond the speed of light.

Why is not there something that moves faster than light? because if an object can move faster than the speed of light, then the object will 'return to the past'. If there is an object with speeds in excess of the speed of light close to us, then we will see it moving away from us, because the object will reach us in advance before the arrival of light that informs his arrival.

Atomic Clock and the effect of Gravity

2011-04-24T00:01:00.003+07:00

Every atom in the universe is a piece of time because the atoms that absorbs and emit light with a certain frequency. While most of the time measurement is based on measuring a series of regular events, such as change of day and night, the vibration of quartz crystals, and others. In this light, vibration is an electrical phenomenon. The frequency of visible light is around 5 x 10^12 vibrations per second. But in the cosmos appears like a rainbow of light radiation. On the one hand there is radio energy with a very low frequency vibration of only a few times just for second. On the other hand there is the frequency of gamma rays billion times greater than the frequency of visible light. All forms of energy such a move with equal speed and have the general properties of the same. When an expert on relativity speaks of 'light', it is meant the electromagnetic waves and not only visible light.

In an atomic process, there can be something in the atom that causes these atoms absorb or emit energy in the form of light. Because the atoms can only be arranged in certain patterns, then the light energy is absorbed or radiated a certain well. And Einstein who found that the energy of light depends on frequency,

In 1971, two American physicist named J.C.Hafele and Richard Keating did an experiment with a four bells cesium fly around the world with jet airplanes. They compared the time indicated the bell with a time standard at the U.S. Naval Observatory, Washington. Experiments carried out by flying to the west and east are completely taken as long as three days. The results of this experiment are the bells are not compatible with the standard time. For each day, the bells which were flown to the east lost an average of 59 nanoseconds, while the west has added time 273 nanoseconds, compared to standard time.

Operation of atomic clocks indicate that the atoms will vibrate more slowly under the influence of gravity is stronger than the resonance in empty space (without gravity). Similarly with our bodies, under the influence of strong gravity, then the impulse of the brain will be slower and the heart will beat more slowly.All who experienced the influence of gravity will feel the effects of time.

If you want to stay young, then you can visit a black hole. It’s not to enter into it, because doing this you might as well commit suicide. Visiting a black hole, meaning you should be able to as close to the black hole. Because of extremely strong gravity of black holes (even beam of light can not escape from the gravity force), then the bell of your time will slow down when viewed by observers that were located quite far from the black hole.

High-speed travel can also make you stay young. For that, we do not need to visit a black hole (which is relatively dangerous). We can plan a trip so that the bells of time in our spacecraft slower than the clock time at our house. The faster the plane moves, and the farther their journey is, the more benefits we can get time.

In this way we assume that we are in a vacuum far from sources of strong gravity. We are in special circumstances, the situation as depicted by the Special Theory of Relativity.

Light Cone

2011-04-22T01:18:00.000+07:00

Everyone who ever heard of relativity course will know what is called 'space-time'. We usually mention a particular event occurs in a place and at one time or a certain time. Thus, the events described occurred in space and time. For example is a plane crash. To determine the occurrence of events in space and time required data regarding the latitude, longitude and altitude of the aircraft from the ground, and the time of the accident. Latitude, longitude and altitude show what is called the spatial coordinates (three numbers coordinates). While the time of the accident is the time coordinate. If one coordinate is represented by one number only spatial coordinates and a fixed time coordinate number one, we can get what is called a diagram of space and time

Figure 1-1 : Space-Time Diagram

In Newtonian mechanics, the method of determining position in space and in time the position determination method may be no overall status are interdependent with each other. For this reason we impose time and space differently. Time in Newtonian mechanics is absolute, but the space is relative.

Einstein's special theory of relativity has changed. There are a number of different ways in determining the position in time. Two events can occur simultaneously viewed by an observer, but can also be viewed the events that one comes first instead of the other events by the second observer, and can also be seen that another incident that just happened earlier before a single event by a third observer. Here space and time are no longer independent of each other. If we change the determination of position in space, we will also change the time interval between two events that occurred. If we change the setting of time in space, we will also change the distance in space between two events. In special relativity is no longer absolute space and time are not absolute as well. What remains is the speed of light.

If our space-time diagram in figure 1-1 less developed, which used two spatial coordinates, we will get figure 1-2 that illustrate the events which appear flashes of light propagates in space-time.

Figure 1-2 : Light Cone Diagram

in Figure 1-2, suppose an event that occurs an O. If there are other events, the event must be located within a region of space-time. If the event is located in or on the cone of light, then this event will be in the future or the past O. Future light cone through O and all things therein referred to as the absolute future of O, and the past light cone O and all the things in it past referred to as absolute O.
Absolute terms this comes from the fact that the nature of the events is the same in every frame of reference in a particular area. That is, although space and time can be transformed into another time interval to a certain extent, but there are limits to this transformation. That is the time interval in the cone of light can’t be transformed into an interval that lies outside the cone of light. Areas outside the light cone is called absolute O elsewhere, or only briefly referred to elsewhere. This area has no contacts at all with O. so, if we observe a star located far away from earth, we only see light coming from the star's past. We did not know if the star is dead or not 'present'. Events that occurred on this elsewhere do not have any influence on the O, due to contact with the O signals needed to move faster than the speed of light, and is not allowed by special relativity. Conversely, events that occurred in or lie in a cone of light can affect O, due to contact with the O signals needed to move more slowly or equal to the speed of light.

Solar Source

2011-04-21T01:32:00.000+07:00

Nature store mystery until Einstein came to uncover. Energy still an ordinary object is very large, otherwise a number of energy is only a very small mass. All the energy that used by human civilization is only about a few tons. For example, a hot bar of steel, just a little more weight around one per billion compared with the same steel in a cold state.

For most of the motion that we can see around us, the mass changes caused by changes in energy it can be ignored because the comparison is very small. With hyper particle, the motion energy subatomic particles become large enough compared with the energy silence. One of the world's most powerful electron boosters is in Stanford, California. Hyper electron has a length of 3 km. If an electron were fired at the end of the hyper electron, the other tip, a distance of 3 km, the electron has a mass of 40,000 times heavier than the electron when at rest. All of the additional mass is energy of motion.

Earth receives about 160 tons of sunlight every day. Green plants absorb sunlight and use it to make carbohydrates water and carbon dioxide gas, so as to supply energy for life on earth.

A solar energy source is a big puzzle for humans before Einstein revealed equivalence between mass and energy are. Charles Darwin and the geologists of the 19th century argued that life on this earth has been going on for at least some hundreds of millions of years. But the physicists like Lord Kelvin and Hermann Helmholtz do not see any energy source that still makes the sun shine for so long. They view that the hot sun and other stars comes from gravity. With this model Kelvin predicted that the sun does not live more than 30 million years ago.

But thanks to Einstein's discovery of the equivalence between matter and energy, so the physicists can estimate the actual age of the sun. The answer is contained in the fusion and fission reactions contained in the sun which is a source of solar energy for survival.

At the core of a new star was born, gravity produces very high temperatures required for the merger nucleus of hydrogen atoms, i.e. protons. In a series of thermonuclear reactions, four protons / hydrogen atoms will combine to form a helium atom, the next heaviest element after hydrogen. Helim atomic rest mass will be much lighter than the rest mass constituent elements.

The material lost due to the merger was about 7 tons for each 1,000 tons of hydrogen are processed. So it turns out the age of the sun far longer than predicted by the Kelvin because of the nuclear reactions that can be explained through the equivalence of mass and energy of Einstein.

While the atoms heavier than hydrogen in our bodies for example, is the result of physical processes contained in the core of stars. When a star has burned all the hydrogen it has, then it started reacting helium star which then produces carbon and oxygen. This process can take place continuously to form elements heavier and will end when the silicon burned into iron. At the time the process has been formed of iron, the process will continue to take place accompanied by the release of energy for every one thousand tons of hydrogen will be produced almost ten tones of heat and light. Iron is the most stable element in which we cannot take them through the process of nuclear energy.

Some nuclei of heavy elements can break dramatically, especially when agitated by a small amount of additional energy. For example, elements such as Uranium-235 will split into two parts when pounded with a low-energy neutron. Neutrons are not electrically charged protons (neutral). When broken, Uranium-235 would release other neutrons from the core and Uranium-235 will hit the other. So forth, causing a chain reaction that releases energy. When these reactions take place in a short time, then the effect will occur as in perstiwa Hiroshima.

When Einstein wrote down the mass-energy equivalence formula was, no one can imagine that is, until all the facts observed and listened to. Currently, hyper-accelerator particles continue to produce a variety of particles with a wide range of behavior. However, all of which prove the truth of the formula E = mc ^ 2. And indeed E = mc ^ 2 is not only a secret energy of the sun, but also the law of all creation - energy creation.

Einstein and Walton experiments

2011-04-20T00:01:00.001+07:00

In 1905, an employee of the patent office in Switzerland, Albert Einstein, stated that the ether did not exist and the hypothesis of its existence is not required. Thus the idea of absolute time also should be abandoned. And Einstein proposed two famous postulates in his paper entitled "The Electrodynamics moving objects" which is currently better known by the name of the Special Relativity Theory. The first postulate states that all laws of science will be the same for all observers moving at constant speed. While the second postulate states that all observers will measure the speed of light is the same however the fast observer is moving. This simple idea has tremendous consequences that give key nuclear era, namely the equivalence of mass and energy that has the equation E = mc ^ 2 (E is energy, m is mass and c is the speed of light), and the law which states that nothing is can move faster than light.

Holding on to found Einstein's energy equation, the physicists are trying to learn the atomic particles in more depth. Some of them find a method to weigh individual atoms accurately and develop hyper engine particulate matter (particle accelerator). Ernest Walton John Crockfort and make electric boosters to atomic particles and used it to shoot protons (hydrogen nuclei), with lithium metal target. When protons hit the helium nuclei, protons will be fused with the nucleus and then blend it will split into two parts, the new core (helium nuclei). The mass of two helium nucleus is lighter than the mass of protons (hydrogen nuclei) plus lithium nuclei. In a nuclear reaction have the missing material, which turned into energy.

The researchers observed that the pair of helium nuclei out from the target in the opposite direction. Each of these helium atoms that exit from collision will cause tiny spots of light when it strikes the core of the fluorescence screen, like on the monitor screen. Crockfort and Walton then calculate the energy of motion helium atoms core by observing how the distance that atoms can gone through over the air. Apparently they found that the energy of motion of helium nuclei are similar to the missing mass of material in accordance with Einstein's equation, E = mc^2.

From the experiments Crockfort and Walton can be said that there are a number of mass motions are converted into energy helium nuclei. But the problem is not the case. Mass and energy can’t be exchanged just as we change the plastic into gold and vice versa. But in fact both are the same thing, mass energy. In these experiments, the core helium atoms that fly out of the lithium target actually has the same mass of particles that produce them, at least for the moment. Mass energy of motion they are added to the conventional mass (mass of silence). Helium nuclei will lose their mass-energy of motion when their movement is slowed when cores collide with atoms in the vicinity. And through observation, energy of motion has been converted into heat energy. The mass-energy that remain on the helium nucleus is often referred to as 'rest mass' which corresponds with the idea of conventional mass, the amount of matter contained in an object.

James Clerk Maxwell and electromagnetic wave

2011-04-19T00:01:00.003+07:00

A Scottish physicist who was born in Edinburgh in 1831, James Clerk Maxwell, trying to write a series of equations that combines electrical and magnetic phenomena that have been observed and measured. Maxwell's four equations formulated on the symptoms of electricity and magnetism. The first describes the magnetic field generated by electric currents, the second describes the electric field generated by a changing magnetic field, the third describes the electric field generated by electric charge, and the fourth describes the magnetic field itself is that the magnetic poles always appear in pairs.
Efforts are made Maxwell are actually an attempt to combine the symptoms of physical electricity and natural magnetism that made the first mathematically. Maxwell's famous discovery until today is the component of electric field and magnetic field components are integrated into single integrated electromagnetic fields that can appear and can move in space. Maxwell then calculates the propagation speed and gets the same speed as the speed of light (300,000 km / sec). We now know that light is one form of electromagnetic waves.
But at the time of Maxwell which is still influenced by the idea of Newton, the rate of electromagnetic waves should be referred as relative to something. At that time, the wave speed referred to the ether. Ether is a hypothetical substance that meets all existing space. But the Michelson-Morley experiment found that the speed of light is the same, not depending on the position and state of constant motion of the observer. Michelson was awarded the Nobel physics prize in 1906 for this work.

Newton Law's of motion

2011-04-18T17:17:00.001+07:00

Newton Law's of motion

Newton's laws of motion are three physical laws that form the basis for classical mechanics. They describe the relationship between the forces acting on a body and its motion due to those forces. They have been expressed in several different ways over nearly three centuries and can be summarized as follows:

First law: Every body remains in a state of constant velocity unless acted upon by an external unbalanced force. This means that in the absence of a non-zero net force, the center of mass of a body either remains at rest, or moves at a constant velocity.
Second law: A body of mass m subject to a net force F undergoes an acceleration a that has the same direction as the force and a magnitude that is directly proportional to the force and inversely proportional to the mass, i.e., F = ma. Alternatively, the total force applied on a body is equal to the time derivative of linear momentum of the body.
Third law: The mutual forces of action and reaction between two bodies are equal, opposite and collinear. This means that whenever a first body exerts a force F on a second body, the second body exerts a force −F on the first body. F and −F are equal in magnitude and opposite in direction. This law is sometimes referred to as the action-reaction law, with F called the "action" and −F the "reaction". The action and the reaction are simultaneous.

The three laws of motion were first compiled by Sir Isaac Newton in his work Philosophiæ Naturalis Principia Mathematica, first published on July 5, 1687. Newton used them to explain and investigate the motion of many physical objects and systems. For example, in the third volume of the text, Newton showed that these laws of motion, combined with his law of universal gravitation, explained Kepler's laws of planetary motion.

See more at wikipedia.org

Newtonian

2011-04-18T00:01:00.004+07:00

At the time of Aristotle, people follow the opinion that all laws governing the universe can be obtained only with the mind alone, until Galileo Galilee came to break the arrogance of this view. In experiments conducted by rolling balls with different weight on an inclined plane, he founded that if speed of each ball with a different weight is the same. Galileo seems to be the first to realize that the acceleration which will reveal the forces acting on these objects, and not the speed. On earth, there are always external forces that will slow the motion of an object unless we continue to encourage relevant bodies to keep moving. That is, an object will keep moving in the same direction with the same speed if an object is not experiencing external forces. The statement is what we now know as Newton's first law

If the work force outside the object, Newton then states does something like this: the same style with the object times the acceleration (change in velocity) of an object. This is called Newton's second law. And Newton also expands this law to explain the motion of planets around the sun. The law used to this is known as Newton's law of gravity. In the law of gravity, Newton states that the force of attraction acting on the objects will be inversely proportional to its distance quadratic. That is, if the mass of one object that has the force four times multiply, then the forces acting on it also will become four times. However if the distance between two mass was doubled, then the forces acting on these objects will become a quarter times the force at first.

Newton had the idea that there should be an absolute inertial reference frame, which is standard absolute silence which is defined by or referred to the empty space. Newton argued that these objects will move with constant velocity in an empty room, when no forces acting on it. Newton also believed the absolute time. In Newton's laws (or Newtonian mechanics), time and space is a thing apart, they must not interfere with each other each other. It lasted long enough until Einstein came to tear this belief.

Imagesetter dalam Teknologi CTP

2010-01-11T18:12:00.017+07:00

     Seperti yang kita ketahui, penggunaan Computer To Plate dalam industri percetakan sangatlah luas. Proses yang dilalui dalam menhasilkan plat dari sebuah image digital juga sangat panjang. Namun, disini akan saya uraikan satu demi satu, mulai dari sebuah gambar yang didesain menggunakan software desain, kemudian masuk dalam workflow proses Computer To Plate dan kemudian menghasilkan image digital yang akan dipergunakan untuk pembuatan plat dalam imagesetter. Pertama, akan kita kupas terlebih dahulu mengenai imagesetter. dengan pokok bahasan intinya adalah imagesetter.
     Secara garis besar, terdapat 3 jenis mekanisme yang digunakan dalam imageseter untuk menghasilkan plat yang dipergunakan dalam offset printing, yaitu internal drum, external drum dan flat bed imegesetter.

1. Penggunaan External Drum dalam imagesetter.
        Pada proses ini, plat yang akan diberi image, diletakkan di luar drum. Plat diletakkan melingkar
    mengelilingi sebuah silinder yang berputar. Dan terdapat sebuah (atau bisa beberapa) sumber laser yang
    ditembakkan tegak lurus terhadap bidang permukaan silinder. Seiring dengan berputarnya silinder yang
    memutar bidang plat, sumber laser bergerak tegal lurus dengan bidang putar silinder. Ilustrasi pergerakan
    silinder, plat dan sumber laser dapat dilihat pada gambar berikut

    Kelebihan imagesetter dengan mengunakan prinsip external drum adalah :
        - Optik / Sumber Laser berada sangat dekat dengan permukaan plat, sehingga mampu mengurangi
            distorsi sinar laser.
        - Karena optik / sumber laser berada di luar drum, maka dapat dimungkinkan untuk penggunaan optik /
            sumber laser secara pararel dengan jumlah yang banyak. Hal ini dapat mempercepat proses
            pembuatan plat pada imagesetter.
        Namun, disamping kelebihannya itu, imagesetter yang cara kerjanya menggunakan prinsip eksternal
    drum, masih mempunyai beberapa kelemahan. Karena silinder yang membawa plat tersebut berputar,
    maka dimungkinkan dapat terjadi ketidakseimbangan image yang dihasilkan sebagai akibat gaya sentrifugal.

2. Penggunaan Internal Drum dalam imagesetter.
        Untuk menghilangkan efek sentrifugal pada plat, dibuatlah desain internal drum. Konsep pembuatan
    imagesetter dengan prinsip kerja seperti ini datang dari konsep film imagesetter. Sebuah plat yang akan
    diberi image, diletakkan di dalam sebuah silinder. Sebuah sumber laser diletakkan di dalam silinder yang
    bergerak searah sumbu silinder. Pada sumber laser terdapat sebuah cermin yang mampu berotasi untuk
    memantulkan sinar laser ke bidang permukaan plat tegak lurus dari sumbu silinder.

        Sumber laser tersebut bergerak pelan searah sumbu silinder, namun cermin pemantul sinar lasernya
    mampu bergerak sangat cepat dan dapat mencapai kecepatan 40.000 rpm. Untuk mengurangi efek vibrasi
    dari getaran 40.000 rpm tersebut, beberapa perusahaan membuat cermin pada imagesetter denngan
    menggunakan material yang berbahan dasar granit yang mempunyai kelebihan solid, mempunyai geometri
    yang stabil dan mampu menghilangkan efek vibrasi. Plat yang akan diberi image, diletakkan pada posisi
    diam dan yang bergerak adalah sumber lasernya.
        Pada imagesetter model eksternal drum, untuk mempercepat proses pembuatan plat, maka diletakkan
    lebih dari satu sumber laser. Namun dalam imagesetter model ini, hal tersebut tidak dimungkinkan. Pada
    tahun 1997, "Luscher" memperkenalkan sistem "XPose!" untuk memberikan solusi dari permasalahan
    tersebut. Pada sistem "XPose!" ini, Luscher mengganti bagian cermin putarnya dengan menggunakan 64
    dioda sumber laser. Sehingga dimungkinkan untuk pembuatan plat secara cepat. Konsep ini
    didemonstarsikan oleh Fuji Film, ECRM dan Cymbolic Science.

3. Penggunaan Flat-Bed Design.
        Pada konsep ini, sebuah palt yang akan diberi image, diletakkan pada sebuah pidah datar. Sebua sinar
    laser dipantulkan oleh cermin poligon secara perbaris.

    Namun ada kelemahan pada prinsip kerja imagesetter dengan menggunakan konsep ini. Sinar laser yang
    jatuhnya di ujung plat bagian luar akan mengalami distorsi dan akan menghasilkan dot yang relatif lebih
    besar dibandingkan dengan dot yang dihasilkan oleh sinar laser pada bagian tengah plat. Namun demikian,
    imagesetter model seperti ini sangat cocok digunakan untuk produksi koran-koran yang lebih
    mengutamakan kecepatan.

Pengantar Computer To Plate

2010-01-07T18:26:00.003+07:00

Istilah "Computer To Plate" menggambarkan suatu proses dalam pembuatan plate secara direct imaging yang dikontrol oleh komputer dari data-data digital. Sistem dan Teknologi Computer To Plate ini pertama kali diperkenalkan di pasaran pada tahun 1993 di acara IPEX 93. Sejak saat itu, sistem dan teknologi Computer To Plate menjadi produk unggulan di pameran-pameran industri percetakan seperti DRUPA 95, IPEX 98 dan lain sebagainya. Seiring perkembangan industri yang semakin bergerak ke arah digital, penggunaan Computer To Plate ( CTP) semakin banyak dijumpai pada percetakan terutama di negara maju.

Sesuai dengan namanya, Computer To Plate (CTP) yang mempergunakan proses direct imaging, proses pembuatan plat yang awalnya (secara konvensional) menggunakan film topografi, maka dengan menggunakan CTP, image dapat dicetak ke plat secara langsung dari file komputer. Selain efisiensi waktu, percetakan yang menggunakan teknologi ini juga akan mendapatkan efisiensi biaya. Proses yang apabila dilakukan secara konvensional, seperti pembuatan film topografi, layouting dan screening dapat semuanya dilakukan secara digital di dalam komputer. Operator CTP hanya perlu melakukan beberapa klik pada mousenya tanpa perlu pindah tempat dan dapat menghasilkan plat hanya dalam hitungan menit. Efisiensi tenaga kerja juga merupakan salah satu bahan pertimbangan di percetakan-percetakan yang telah menggunakan teknologi ini karena teknologi ini bisa dijalankan hanya dengan menggunakan 1 operator CTP. Kelemahannya, percetakan yang menggunakan teknologi ini harus mempunyai operator yang "mengerti" tentang komputer dan paham tentang proses alur kerja (workflow) dalam CTP.

Secara umum, komponen yang dipergunakan dalam sistem Computer To plate ini ada 3 macam

a. Komputer

Komputer merupakan komponen utama dan juga merupakan komponen paling penting dalam alur

proses ( workflow) pembuatan plat dalam sistem CTP ini. Proses Imposisi, Raster Image Processor

(RIP) dan juga penyimpanan data dilakukan dengan menggunakan komputer.

b. Imaging System

Imaging System memegang peranan yang tidak kalah penting dalam proses Computer To Plate.

Transfer data digital dari komputer ke plat dilakukan oleh plat imagesetter dengan menggunakan laser

dengan daya dan panjang gelombang laser disesuaikan dengan sensitivitas permukaan plat.

c. Printing Plat

Komponen terakhir yang digunakan adalah plat. Saat ini, dapat dijumpai berbagai macam tipe plat

yang digunakan pada proses Computer To Plate ini. Namun tidak semuanya bisa dipergunakan karena

harus disesuaikan dengan jenis imagesetter yang digunakan.

Teori Warna

2009-12-17T17:10:00.000+07:00

Cahaya mempunyai 2 sifat fisik, yaitu cahaya sebagai partikel dan cahaya sebagai gelombang. Inilah yang diungkapkan oleh Louis de Broglie dalam hipotesanya : "Cahaya selain memiliki sifat sebagai partikel, juga memiliki sifat sebagai gelombang".

Sebagai sebuah partikel, cahaya mempunyai massa, kecepatan dan momentum (efek compton). Sedangkan sebagai sebuah gelombang, cahaya mempunyai panjang gelombang, frekuensi, dan amplitudo. Cahaya merupakan sekumpulan berkas gelombang yang mempunyai panjang gelombang terkecil s/d panjang gelombang yang terbesar. Namun, dari kesekian banyaknya panjang gelombang cahaya yang ada, hanya sebagian kecil saja yang bisa tertangkap oleh panca indera. Panca indera kita hanya bisa menangkap cahaya yang memiliki panjang gelombang antara 380 sampai 780 nanometer. Itulah yang kita sebut sebagai cahaya tampak.

Cahaya tampak sendiri bisa diuraikan lagi menjadi warna-warna pelangi oleh prisma kaca. warna-warna inilah yang sering disebut sebagai spectrum warna. Panjang gelombang yang paling rendah yang bisa ditangkap oleh panca indera adalah panjang gelombang cahaya warna ungu (380 nanometer). Panjang gelombang yang paling tinggi yang bisa ditangkap oleh panca indera adalah panjang gelombang warna merah (780 nanometer).

     Proses terlihatnya warna adalah dikarenakan adanya cahaya yang menimpa suatu benda, dan benda tersebut memantulkan cahaya ke mata (retina) kita hingga terlihatlah warna. Benda berwarna merah karena sifat pigmen benda tersebut memantulkan warna merah dan menyerap warna lainnya. Benda berwarna hitam karena sifat pigmen benda tersebut menyerap semua warna pelangi. Sebaliknya suatu benda berwarna putih karena sifat pigmen benda tersebut memantulkan semua warna pelangi.

     Sebagai bagian dari elemen tata rupa, warna memegang peran sebagai sarana untuk lebih mempertegas dan memperkuat kesan atau tujuan dari sebuah karya desain. Dalam perencanaan corporate identity, warna mempunyai fungsi untuk memperkuat aspek identitas. Lebih lanjut dikatakan oleh Henry Dreyfuss , bahwa warna digunakan dalam simbol-simbol grafis untuk mempertegas maksud dari simbol-simbol tersebut . Sebagai contoh adalah penggunaan warna merah pada segitiga pengaman, warna-warna yang digunakan untuk traffic light merah untuk berhenti, kuning untuk bersiap-siap dan hijau untuk jalan. Dari contoh tersebut ternyata pengaruh warna mampu memberikan impresi yang cepat dan kuat.

     Kemampuan warna menciptakan impresi, mampu menimbulkan efek-efek tertentu. Secara psikologis diuraikan oleh J. Linschoten dan Drs. Mansyur tentang warna sbb: Warna-warna itu bukanlah suatu gejala yang hanya dapat diamati saja, warna itu mempengaruhi kelakuan, memegang peranan penting dalam penilaian estetis dan turut menentukan suka tidaknya kita akan bermacam-macam benda.

     Dari pemahaman diatas dapat dijelaskan bahwa warna, selain hanya dapat dilihat dengan mata ternyata mampu mempengaruhi perilaku seseorang, mempengaruhi penilaian estetis dan turut menentukan suka tidaknya seseorang pada suatu benda. Berikut kami sajikan potensi karakter warna yang mampu memberikan kesan pada seseorang sbb :
1.   Hitam, sebagai warna yang tertua (gelap) dengan sendirinya menjadi lambang untuk sifat gulita dan
      kegelapan (juga dalam hal emosi).
2.   Putih, sebagai warna yang paling terang, melambangkan cahaya, kesucian.
3.   Abu-abu, merupakan warna yang paling netral dengan tidak adanya sifat atau kehidupan spesifik.
4. Merah, bersifat menaklukkan, ekspansif (meluas), dominan (berkuasa), aktif dan vital (hidup), panas
    membara, peringatan, penyerangan, cinta.
5. Kuning, dengan sinarnya yang bersifat kurang dalam, merupakan wakil dari hal-hal atau benda yang
      bersifat cahaya, momentum dan mengesankan kebahagiaan, keceriaan dan hati-hati
6. Biru, sebagai warna yang menimbulkan kesan dalamnya sesuatu (dediepte), sifat yang tak terhingga dan
      transenden, disamping itu memiliki sifat tantangan.
7. Hijau, mempunyai sifat keseimbangan dan selaras, membangkitkan ketenangan dan tempat mengumpulkan
      daya-daya baru, identik dengan pertumbuhan dalam lingkungan,pasukan perdamaian,kepuasan
8. Pink, warna yang identik dengan wanita, menarik/cantik, gulali
9.   Orange, warna yang identik dengan musim gugur, penuh kehangatan, halloween.
10. Coklat, warna yang mengesankan hangat, identik dengan musim gugur, kotor, bumi
11. Ungu, warna yang identik dengan kesetiaan, kepuasan, Barney (tokoh boneka berwarna ungu)

     Dari sekian banyak warna, dapat dibagi dalam beberapa bagian yang sering dinamakan dengan sistem warna Prang System yang ditemukan oleh Louis Prang pada 1876 atau disebut juga sebagai atribut warna meliputi :
1. Hue, adalah istilah yang digunakan untuk menunjukkan nama dari suatu warna, seperti merah, biru, hijau
     dsb.
2. Value, adalah dimensi kedua atau mengenai terang gelapnya warna. Contohnya adalah tingkatan warna
     dari putih hingga hitam.
3. Saturation/Intensity, seringkali disebut dengan chroma, adalah dimensi yang berhubungan dengan cerah
     atau suramnya warna.

     Selain Prang System terdapat beberapa sistem warna lain yakni, CMYK atau Process Color System, Munsell Color System, Ostwald Color System, Schopenhauer/Goethe Weighted Color System, Substractive Color System serta Additive Color/RGB Color System. Diantara bermacam sistem warna diatas, kini yang banyak dipergunakan dalam industri media visual cetak adalah CMYK atau Process Color System yang membagi warna dasarnya menjadi Cyan, Magenta, Yellow dan Black. Sedangkan RGB Color System dipergunakan dalam industri media visual elektronika.

Screening process part II

2009-12-17T14:39:00.005+07:00

Pada posting sebelumnya telah dijelaskan tentang 2 model screening yang dipergunakan dalam percetakan. Berikutnya akan dijelaskan mengenai model screening yang lainnya.

3. Hybrid Screening.

     Hybrid Screening merupakan gabungan antara AM Screening dan FM Screening. FM screening digunakan untuk gambar yang mempunyai intensitas warna yang kuat dan lemah. Sedangkan warna yang mempunyai intensitas sedang, menggunakan AM Screening. Kedua model AM screening dan FM screening ini dapat diterapkan bersama-sama pada sebuah objek gambar.

model hybrid screening.
pada ujung kiri dan kanan, digunakan model FM Screening
pada bagian tengahnya digunakan model AM Screening

4. Digital Screening

     Digital Screening merupakan proses modulasi gambar oleh komputer yang diterjemahkan ke dalam dot/titik. Digital screening ini biasanya digunakan oleh percetakan yang menggunakan sistem "Computer to ...... Technology". Sebagai Contoh Computer To Plate (CTP), Computer To Film, Computer To Press dll.
     Digital Screening ini mensimulasikan warna-warna yang terdapat pada setiap element gambar ( pixel : picture element ) kedalam dot-dot yang disesuaikan dengan resolusi yang digunakan. Semakin tinggi resolusi yang digunakan, gambar yang dihasilkan akan semakin bagus. Sebagai contoh untuk mesin sekelas Speedmaster, resolusi yang digunakan adalah 2400 dpi (dpi = dots per inchi).
     Pada model screening konvensional, warna-warna gray (warna pertengahan antara warna kuat dan lemah) mempunyai variasi diameter dot per screen cellnya. Untuk resolusi 60 lines/cm, dapat diasumsikan bahwa disana akan terdapat sekitar 70 s/d 100 dot per area (ini berarti bahwa dot-dot tersebut akan mempunyai kisaran diameter sekitar 1 s/d 2 um.
   Apabila sebuah gambar, yang tiap pixel-nya dirubah ke dalam bentuk raster (dot), maka jumlah intensitas warna akan ditentukan oleh ukuran dari screen cell dot tersebut. Dalam hal ini, jumlah intensitas warna dari gambar aslinya akan disimulasikan oleh komputer dengan menggunakan resolusi garis L (line per inchi ataupun line per cm) dan resolusi jumlah dot A (Addressability, dengan satuan dpi) yang diukur pada masing-masing posisi pixel gambar aslinya.
   Dalam model screening ini, sebuah gambar akan ditransformasikan / diterjemahkan oleh komputer kedalam bahasa PostScript, yang kemudian diterjemahkan kembali menggunakan RIP (Raster Image Processors). Pembahasan lebih lanjut mengenai PostScript ini akan dibahan di postingan selanjutnya.

Screening Process

2009-12-09T16:21:00.030+07:00

Screening yang ingin saya bahas disini bukanlah screening yang sering dilakukan pada saat pengkaderan organisasi. Tapi screening yang diberlakukan pada suatu image/gambar/grafik yang nantinya dipersiapkan untuk proses cetak.

proses screening terhadap sebuah objek atau gambar, dapat dilakukan melalui beberapa cara. Disini akan saya jabarkan dan telaah satu-persatu, sehingga kita dapat mengetahui mana yang terbaik dipergunakan untuk membuat cetakan gambar yang mengutamakan keindahan / desain ataukah cetakan yang mengutamakan keamanan / security printing.

1. Amplitude Modulation (AM)
Screening model ini mempunyai karaketristik jarak antar dot satu dengan dot yang lainnya adalah sama, namun memiliki diameter dot yang berbeda-beda. Sebagai contohnya, gambar dengan raster 45 % akan memiliki diameter dot yang lebih lebar dibandingkan gambar dengan raster 15 %. Screening model ini biasa dikenal dengan nama autotypical screening.

2. Frequency Modulation.
Screening model ini mempunyai karakteristik yaitu besarnya diameter dot pada semua bagian sama, namun memiliki jarak yang berbeda-beda antara satu dot dengan dot yang lain tergantung dari besar kecilnya raster di gambar/grafik tersebut. Ketika suatu image / gambar diproses dengan menggunakan screening model ini, sebuah warna, akan dikonversikan kedalam bentuk titik-titik / dot yang jumlahnya disesuaikan dengan kuat lemahnya warna itu di area tersebut. Area tersebut biasanya disebut screen cell.
Karena jarak antar satu dot dengan dot yang lain cenderung berbeda-beda, maka secara sepintas, penyebaran dot akan terlihat acak pada suatu gambar. Itulah kenapa, screening model ini biasa disebut stochastic screening.

Gambar disamping terlihat bahwa untuk proses screening dengan menggunakan Amplitudo Modulation (AM) jarak antar dot / titik adalah sama, namun memiliki diameter dot yang berbeda - beda untuk warna 40%, 20% dst.
Sedangkan untuk Frequency Modulation, ukuran dot di semua lokasi adalah sama, namun yang membedakan hanyalah jumlah dot yang terdapat dalam satu area ( dalam satu screen cell )

Dari kedua metode screening ini, terdapat perbedaan yang mencolok apabila sebuah image/gambar, telah mengalami proses pencetakan. Gambar di samping ini menggambarkan perbedaan yang mencolok.
Dengan menggunakan screening model AM, gambar yang ditampilkan akan terlihat kasar. Sedangkan dengan menggunakan screening model FM, gambar yang dihasilkan akan lebih halus.

Mekanisme Ink Transfer pada proses cetak

2009-12-08T13:38:00.004+07:00

Dalam dunia percetakan, Ink Transfer / Transfer tinta yang terjadi dari plat ataupun master ke media cetakan dipengaruhi oleh beberapa parameter :

1. ketebalan lapisan tinta yang terdapat pada plat/master cetakan
2. periode/waktu kontak yang terjadi antara plat/master cetakan dengan media cetakan ataupun blanket
    (biasanya disebut printing speed)
3. Pressure/tekanan antara plat/master cetakan dengan media cetakan ataupun blanket (biasanya disebut
    printing pressure)
4. sifat rheology dari tinta
5. ratio / perbandingan temperatur (temperatur ini mempengaruhi sifat rheology dari tinta tersebut)
6. sifat permukaan dari media cetakan dan plat/master cetakan (wettability, absorbsi/penyerapan, sifat
    kekasaran dll)

Faktor lain yang mempengaruhi proses ink transfer tersebut adalah tingkat absorpsi/penyerapan tinta ke media cetakan/kertas.

Proses ini dapat dijelaskan melalui gambaran sebagai berikut