Para Peraih Nobel dari California Institue of Technology I

"There is no likelihood man can ever tap the power of the atom. The glib supposition of utilizing atomic energy when our coal has run out is a completely unscientific Utopian dream, a childish bug-a-boo. Nature has introduced a few fool-proof devices into the great majority of elements that constitute the bulk of the world, and they have no energy to give up in the process of disintegration."

 ~Prof. Robert A. Millikan, 1928 at the Chemists' Club (New York)

ROBERT ANDREWS MILLIKAN (1868–1953)

 
Robert A. Millikan was Caltech’s first Nobel Prize winner. He was awarded the physics prize in 1923 for isolating the electron and measuring its charge. 

An impressive experimentalist, Millikan is also credited with the verification of Einstein’s photoelectric equations and with the numerical determination of Planck’s constant. 

He also initiated serious study of cosmic rays, and in fact gave them their present nam.

Millikan left a professorship at the University of Chicago to become director of Caltech’s new Norman Bridge Laboratory of Physics in 1921. 

With George Ellery Hale and A. A. Noyes, Millikan formed the executive council that molded the Institute into a preeminent research university. Refusing the presidency of Caltech, he instead served as the chairman of the council from 1921 until his retirement in 1945. 

In his will, he left one-fifth of his estate—$100,000—as an endowment fund for one of his favorite campus organizations: the Caltech Y.

THOMAS HUNT MORGAN (1866–1945)

 
Thomas Hunt Morgan won the Nobel Prize in Physiology or Medicine in 1933 for his chromosome theory of heredity. On the basis of experimental research with the fruit fly (Drosophila), he demonstrated that genes are linked in a series on chromosomes and that they determine identifiable, hereditary traits. 

An embryologist by training, Morgan turned his attention to Drosophila in 1908. On the basis of fly-breeding experiments, he developed a hypothesis of sex-linked characteristics, which he theorized were part of the X chromosome of females.

In 1928, he came to Caltech to organize work in biology. 

The most influential biologist in America at that time, Morgan pioneered the new science of genetics, the essential science for the future of biology. In 1930, he also established a marine biology laboratory at Corona del Mar (the lab is still in use today). 

By then, Morgan had left Drosophila genetics and had returned to his earlier interest in developmental biology.

He often spent weekends at the marine station working with an organism called the sea squirt. He remained on the Caltech faculty for the rest of his career. 

CARL DAVID ANDERSON (1905–1991)

 
Carl D. Anderson was a corecipient of the Nobel Prize in Physics in 1936, when he was only 31 years old and still an assistant professor at Caltech. 

Anderson won the prize for discovering the positron, the first empirical evidence for the existence of antimatter, in the course of his cosmic-ray researches. (He shared the physics prize with Victor F. Hess of Austria, the discoverer of cosmic rays.) It was Robert A. Millikan, Anderson’s graduate advisor, who had steered Anderson into cosmic-ray research.

Anderson arrived at Caltech in 1923 as an 18-year-old freshman, and never left. He discovered the positron in 1932, using a cloud chamber. 

Shortly thereafter, Anderson and his graduate student, Seth Neddermeyer, discovered mu-mesons, or muons. During World War II, Caltech scientists produced and tested land and aircraft rockets for the United States Navy. 

Anderson supervised the testing of aircraft rockets at China Lake and later visited the front lines in Europe to observe how the rockets performed. 

He served as chair of the Division of Physics, Mathematics and Astronomy from 1962 to 1970, and was named emeritus in 1976.

EDWIN MATTISON MCMILLAN (1907–1991)

Edwin M. McMillan won the Nobel Prize in Chemistry in 1951 for his discovery of element 93, neptunium, the first so-called transuranium (heavier than uranium) element. He shared the prize that year with Glenn T. Seaborg.

McMillan received his bachelor’s and master’s degrees at Caltech in 1928 and 1929, respectively, then earned his doctorate at Princeton University in 1932. 

He then accepted a faculty position at the University of California, Berkeley, where he was named professor in 1946 and director of the Lawrence Radiation Laboratory in 1958. He discovered neptunium, a decay product of uranium-239, in 1940, while studying nuclear fission. 

In 1945, he made a major advance in the development of Ernest Lawrence’s cyclotron, when he synchronized the device’s electrical pulses to allow atoms to accelerate indefinitely. McMillan served as president of the National Academy of Sciences from 1968 to 1971.

LINUS CARL PAULING (1901–1994)

 
Linus Pauling was the only winner of two unshared Nobel Prizes in different categories. He is also considered by many to be the greatest chemist of the 20th century. 

He was awarded the 1954 Nobel Prize in Chemistry for his work on molecular structure and chemical bonds, and he won the Peace Prize in 1962 for his efforts to prevent the testing and use of nuclear weapons.

Pauling came to Caltech as a graduate student, receiving his PhD in physical chemistry in 1925. 

He then joined the faculty, becoming a full professor in 1931 (at the age of 30), and chair of the chemistry and chemical engineering division six years later. 

In addition to his research on chemical bonding, he made important discoveries in molecular biology, such as identifying the genetic defect in the hemoglobin molecule that causes sickle-cell disease. 

In 1951, Pauling and Robert Corey discovered the alpha helix structure that serves as a universal structural building block for protein molecules. 

In the 1970s, Pauling provoked controversy by suggesting that large doses of Vitamin C would promote good health. After leaving Caltech in 1963, he was a member of the Center for the Study of Democratic Institutions in Santa Barbara, a professor at Stanford University, and director of research at the Linus Pauling Institute of Science and Medicine in Palo Alto.

WILLIAM BRADFORD SHOCKLEY (1910–1989)

William B. Shockley shared the 1956 Nobel Prize in Physics with John Bardeen and Walter H. Brattain for their development of the transistor, which largely replaced the much-larger, less-efficient vacuum tube and made possible the construction of microelectronic devices.

Schockley received his BS degree at Caltech in 1932; he then earned a PhD at Harvard. In 1936, he accepted a position on the technical staff of Bell Labs, where he began the work that ultimately produced the transistor. He served as director of research for the Antisubmarine Warfare Operations Research Group of the U.S. Navy during World War II. 

Schockley returned to Caltech in 1954 as a visiting professor of physics, then worked for a year as deputy director of Weapons Systems Evaluation for the Department of Defense. 

He joined Beckman Instruments, Inc., in 1955, and founded the Shockley Semiconductor Laboratory there. In 1958, he went to Stanford University, where he became the first Poniatoff Professor of Engineering Science in 1963. 

He retired in 1974.

Sumber:

California Institute of Technology

http://www.pma.caltech.edu/GSR/physics.html

Nobel Prize

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Practical techniques

Further information: List of orbits

Transfer orbits

Transfer orbits allow spacecraft to move from one orbit to another. Usually they require a burn at the start, a burn at the end, and sometimes one or more burns in the middle. The Hohmann transfer orbit typically requires the least delta-v, but any orbit that intersects both the origin orbit and destination orbit may be used.

Gravity assist and the Oberth effect

In a gravity assist, a spacecraft swings by a planet and leaves in a different direction, at a different velocity. This is useful to speed or slow a spacecraft instead of carrying more fuel.

This maneuver can be approximated by an elastic collision at large distances, though the flyby does not involve any physical contact. Due to Newton's Third Law (equal and opposite reaction), any momentum gained by a spacecraft must be lost by the planet, or vice versa. However, because the planet is much, much more massive than the spacecraft, the effect on the planet's orbit is negligible.

The Oberth effect can be employed, particularly during a gravity assist operation. This effect is that use of a propulsion system works better at high speeds, and hence course changes are best done when close to a gravitating body; this can multiply the effective delta-v.

Interplanetary Transport Network and fuzzy orbits

Main article: Interplanetary Transport Network

See also: Low energy transfers

It is now possible to use computers to search for routes using the nonlinearities in the gravity of the planets and moons of the solar system. For example, it is possible to plot an orbit from high earth orbit to Mars, passing close to one of the Earth's Trojan points. Collectively referred to as the Interplanetary Transport Network, these highly perturbative, even chaotic, orbital trajectories in principle need no fuel (in practice keeping to the trajectory requires some course corrections). The biggest problem with them is they are usually exceedingly slow, taking many years to arrive. In addition launch windows can be very far apart.

They have, however, been employed on projects such as Genesis. This spacecraft visited Earth's lagrange L1 point and returned using very little propellant.

A Unified Physics By 2050 Part III

 

"Kasih hanya akan datang kepada mereka yang mengenal dirinya dan Tuhannya"

~arip~

A Unified Physics by 2050?

Experiments at CERN and elsewhere should let us complete the Standard Model of particle physics, but a unified theory of all forces will probably require radically new ideas.

By: Prof. Steven Weinberg, Ph.D.

Suppressed Interactions 

What then? There is virtually no chance that we will be able to do experiments involving processes at particle energies like 10^16 GeV. With present technology the diameter of an accelerator is proportional to the energy given to the accelerated particles. To accelerate particles to an energy of 10^16 GeV would require an accelerator a few light-years across. Even if someone found some other way to concentrate macroscopic amounts of energy on a single particle, the rates of interesting processes at these energies would be too slow to yield useful information. 

But even though we cannot study processes at energies like 10^16 GeV directly, there is a very good chance that these processes produce effects at accessible energies that can be recognized experimentally because they go beyond anything allowed by the Standard Model. The Standard Model is a quantum field theory of a special kind, one that is "renormalizable." This term goes back to the 1940s, when physicists were learning how to use the first quantum field theories to calculate small shifts of atomic energy levels. 

They found that calculations using quantum field theory kept producing infinite quantities, a situation that usually means a theory is badly flawed or is being pushed beyond its limits of validity. In time, they found a way to deal with the infinite quantities by absorbing them into a redefinition, or "renormalization," of just a few physical constants, such as the charge and mass of the electron. (The minimum version of the Standard Model, with just one scalar particle, has 18 of these constants.) Theories in which this procedure worked were called renormalizable and had a simpler structure than nonrenormalizable theories.

Image: Johnny Johnson

THE HIERARCHY PROBLEM is a measure of our ignorance. Experiments (yellow band) have probed up to an energy of about 200 GeV and have revealed an assortment of particle masses (red) and interaction energy scales (green) that are remarkably well described by the Standard Model. The puzzle is the vast gap to two further energy scales, that of strong-electroweak unification near 10^16 GeV and the Planck scale, characteristic of quantum gravity, around 10^18 GeV.

It is this simple renormalizable structure of the Standard Model that has let us derive specific quantitative predictions for experimental results, predictions whose success has confirmed the validity of the theory. In particular, the principle of renormalizability, together with various symmetry principles of the Standard Model, rules out unobserved processes such as the decay of isolated protons and forbids the neutrinos from having masses. Physicists commonly used to believe that for a quantum field theory to have any validity, it had to be renormalizable. This requirement was a powerful guide to theorists in formulating the Standard Model. It was terribly disturbing that it seemed impossible, for fundamental reasons, to formulate a renormalizable quantum field theory of gravitation. 


Today our perspective has changed. Particle physics theories look different depending on the energy of the processes and reactions being considered. Forces produced by exchange of a very massive particle will typically be extremely weak at energies that are low compared with that mass. Other effects can be similarly suppressed, so that at low energies one has what is known as an effective field theory, in which these interactions are negligible. Theorists have realized that any fundamental quantum theory that is consistent with the special theory of relativity will look like a renormalizable quantum field theory at low energies. But although the infinities are still canceled, these effective theories do not have the simple structure of theories that are renormalizable in the classic sense. Additional complicated interactions are present; instead of being completely excluded, they are just highly suppressed below some characteristic energy scale.

Image: Slim Films

WHAT COMES NEXT? There are several possibilities for the unified physics that lies beyond the Standard Model. Technicolor models (a) introduce new interactions analogous to the "color" force that binds quarks. Accompanying the interactions are new generations of particles unlike the three known generations. Supersymmetry (b) relates fermions to bosons and adds the supersymmetric partners of each known particle to the model. M-theory and string theory (c) recast the entire model in terms of new entities such as tiny strings, loops and membranes that behave like particles at low energies.

Gravitation itself is just such a suppressed nonrenormalizable interaction. It is from its strength (or rather weakness) at low energies that we infer that its fundamental energy scale is roughly 10 ¹⁸ GeV. Another suppressed nonrenormalizable interaction would make the proton unstable, with a half-life in the range of 10 ³¹ to 10 ³⁴ years, which might be too slow to be observed even by 2050 [see my article "The Decay of the Proton"; Scientific American, June 1981]. Yet another suppressed nonrenormalizable interaction would give the neutrinos tiny masses, about 10^-11 GeV. There is already some evidence for neutrino masses of this order; this should be settled well before 2050. 

Observations of this kind will yield valuable clues to the unified theory of all forces, but the discovery of this theory will probably not be possible without radically new ideas. Some promising ones are already in circulation. There are five different theories of tiny one-dimensional entities known as strings, which in their different modes of vibration appear at low energy as various kinds of particles and apparently furnish perfectly finite theories of gravitation and other forces in 10 space-time dimensions. 

Of course, we do not live in 10 dimensions, but it is plausible that six of these dimensions could be rolled up so tightly that they could not be observed in processes at energies below 10 ¹⁶ GeV per particle. Evidence has appeared in the past few years that these five string theories (and also a quantum field theory in 11 dimensions) are all versions of a single fundamental theory (sometimes called M-theory) that apply under different approximations ["The Theory Formerly Known as Strings"]. But no one knows how to write down the equations of this theory.

Further Reading:

1. Unified Theories of Elementary-Particle Interaction. Steven Weinberg in Scientific American, Vol. 231, No. 1, pages 50-59; July 1974.

2. Dreams of a Final Theory. Steven Weinberg. Pantheon Books, 1992.

3. Reflections on the Fate of Spacetime. Edward Witten in Physics Today, Vol. 49, No. 4, pages 24-30; April 1996.

4. Duality, Spacetime and Quantum Mechanics. Edward Witten in Physics Today, Vol. 50, No. 5, pages 28-33; May 1997.

5. The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory. Brian Greene. W. W. Norton,1999.

http://hera.ph1.uni-koeln.de/~heintzma/Weinberg/Weinberg.htm 

The Author
 

STEVEN WEINBERG is head of the Theory Group at the University of Texas at Austin and a member of its physics and astronomy departments. His work in elementary particle physics has been honored with numerous prizes and awards, including the Nobel Prize for Physics in 1979 and the National Medal of Science in 1991. 

The third volume (Supersymmetry) of his treatise The Quantum Theory of Fields is out from Cambridge University Press. The second volume (Modern Applications) was hailed as being "unmatched by any other book on quantum field theory for its depth, generality and definitive character."