A millennium of Quantum Physics - ways to meet precision
ब्रह्मैवेदममृतं पुरस्तात् ब्रह्म पश्चात् ब्रह्म उत्तरतो दक्षिणतश्चोत्तरेण ।
अधश्चोर्ध्वं च प्रसृतं ब्रह्मैवेदं विश्वमिदं वरिष्ठम् ॥
This is a reference to the Mundaka Upanishad mantra (above) in which the Vedic understanding of the connectivity of living entities is put forward to help the Bhakta (practitioner of yoga) to understand the difference between the body and the living entity. How the real nature of the living entity is realized only in union with the source, the supreme being (Brahman/Krishna) through a platform of transcendental divine loving service. Schrödinger, in speaking of a universe in which particles are represented by wave functions, said, “The unity and continuity of Vedanta are reflected in the unity and continuity of wave mechanics. This is entirely consistent with the Vedanta concept of All in One.”
Max Planck hypothesized that the total energy of a vibrating system cannot be changed continuously. Instead, the energy must jump from one value to another in discrete steps, or quanta, of energy. This opinion of energy quanta was so radical that Planck let it lay uncultivated. Then, Einstein, in his wonder year of 1905, acknowledged the implications of quantization for light. So new and bizarre concept has managed little progress and further physicists endeavoured for discovering modern quantum theory.
Importance of quantum mechanics realised when several theories are facts and were simply empirical laws but were not much satisfying. For instance Thousands of pages of spectral data listed precise values for the wavelengths of the elements, but nobody knew why spectral lines occurred, much less what information they conveyed. Thermal and electrical conductivities were interpreted by suggestive models that fitted roughly half of the facts. The masses of equal volumeThe Periodic Table, which provided a key organizing principle for the flourishing science of chemistry, had absolutely no theoretical basis.
The greatest achievements of the revolution is :- Quantum mechanics has obtained a quantitative theory of matter. Anyone can understand essentially every detail of atomic structure; the Periodic Table has a simple and natural explanation; and the vast arrays of spectral data fit into an elegant theoretical framework. Quantum theory permits the quantitative understanding of molecules, of solids and liquids, and of conductors and semiconductors. It explains bizarre phenomena such as superconductivity and superfluidity, and exotic forms of matter such as the stuff of neutron stars and Bose-Einstein condensates, in which all the atoms in a gas behave like a single superatom. Quantum mechanics provides essential tools for all of the sciences and for almost all technogical advancements.
Quantum physics actually encompasses two entities. Quantum Mechanics (Theory of matter at atomic level) and Quantum Fields
Quantum Mechanics :- The specific challenge was to understand the spectrum of light emitted by hot bodies: blackbody radiation. Planck applied his quantum hypothesis to the energy of the vibrators in the walls of a radiating body. Quantum physics might have ended there if in 1905 a novice--Albert Einstein--had not reluctantly concluded that if a vibrator's energy is quantized, then the energy of the electromagnetic field that it radiates--light--must also be quantized. Experiments on the photoelectric effect in the following decade revealed that when light is absorbed its energy actually arrives in discrete bundles, as if carried by a particle. Once again, the door to progress was opened by a novice: Niels Bohr. In 1913, Bohr proposed a radical hypothesis: Electrons in an atom exist only in certain stationary states, including a ground state. Electrons change their energy by "jumping" between the stationary states, emitting light whose wavelength depends on the energy difference.
In 1923 Louis de Broglie, in his Ph.D. thesis, proposed that the particle behavior of light should have its counterpart in the wave behavior of particles. He associated a wavelength with the momentum of a particle: The higher the momentum the shorter the wavelength. The idea was intriguing, but no one knew what a particle's wave nature might signify or how it related to atomic structure. Nevertheless, de Broglie's hypothesis was an important precursor for events soon to take place.
Satyendra N. Bose proposed a totally new way to explain the Planck radiation law. He treated light as if it were a gas of massless particles (now called photons) that do not obey the classical laws of Boltzmann statistics but behave according to a new type of statistics based on particles' indistinguishable nature.
Einstein immediately applied Bose's reasoning to a real gas of massive particles and obtained a new law--to become known as the Bose-Einstein distribution--for how energy is shared by the particles in a gas. Under normal circumstances, however, the new and old theories predicted the same behavior for atoms in a gas.
It was recognized that all particles obey either Fermi-Dirac statistics or Bose-Einstein statistics.
Dirac laid the foundations of quantum field theory by providing a quantum description of the electromagnetic field.
Heisenberg laid the foundations for atomic structure theory by obtaining an approximate solution to Schrödinger's equation for the helium atom in 1927, and general techniques for calculating the structures of atoms were created soon after by John Slater, Douglas Rayner Hartree, and Vladimir Fock.The structure of the hydrogen molecule was solved by Fritz London and Walter Heitler. Heisenberg explained the origin of ferromagnetism. The Schrödinger version of quantum mechanics, sometimes called wave mechanics.
The solutions to Schrödinger's equation are known as wave functions.Wave function, explains the entire knowledge of a system and from the wave function one can calculate the possible values of every observable quantity. The probability of finding an electron in a given volume of space is proportional to the square of the magnitude of the wave function.
Consequently, the location of the particle is "spread out" over the volume of the wave function. The momentum of a particle depends on the slope of the wave function: The greater the slope, the higher the momentum. Because the slope varies from place to place, momentum is also "spread out." The need to abandon a classical picture in which position and velocity can be determined with arbitrary accuracy in favor of a blurred picture of probabilities is at the heart of quantum mechanics.
A helium atom consists of a nucleus surrounded by two electrons. The wave function of helium describes the position of each electron.
One of the astonishing discoveries in quantum mechanics is that for electrons the wave function always changes sign. The consequences are dramatic, for if two electrons are in the same quantum state, then the wave function has to be its negative opposite. Consequently, the wave function must vanish. Thus, the probability of finding two electrons in the same state is zero. This is the Pauli exclusion principle. For particles with integer spin, including photons, the wave function does not change sign. Such particles are called bosons.
Atoms in a gas have been cooled to the quantum regime where they form a Bose-Einstein condensate, in which the system can emit a superintense matter beam--forming an atom laser.
Conclusion :- An Century ago indepth understanding of the physical world was empirical. Quantum physics provided the world, a theory of matter and fields, and that knowledge transformed our world. In the current century, quantum mechanics continue to provide fundamental concepts and essential tools for all of the sciences. We can make such forecasting and prediction confidently because for the world around us quantum physics provides an exact and complete theory.
Perhaps string theory--a generalization of quantum field theory that eliminates all infinities by replacing pointlike objects such as the electron with extended objects--or some theory only now being conceived, will solve the riddle.
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