ရခိုင့္အေတြးအေခၚ

The Current Paradigm in Natural Science began around the turn of the 20th Century. It is the third major paradigm in the history of science.
Ancient Paradigm (Aristotle and Ptolemy)
Earth centered universe
The only thing that exists is matter (or matter and the void
Universe has seven spheres which revolve around earth (sometimes in retrograde motions—Ptolemy)
Newtonian Paradigm(Copernicus, Galileo and Newton)
Sun centered universe
All that exist are matter and energy
All bodies revolve around the sun
Universe is materialistic and mechanistic
New Paradigm (Einstein, Bohr, Heisenberg)
Undefined center of universe
All things composed of space-time in relationship of probability
Universe is non-material and stochastic
Rethinking the structure of reality
Is the nature of reality material, ideal, both, neither? The structure of reality is the basis of the accepted paradigm in science. As the idea of the structure changes, the paradigm changes.
WERNER HEISENBERG (1901 - 1976)
Who was he?
Heisenberg was one of the greatest physicists of the twentieth century. He is best known as a founder of quantum mechanics, the new physics of the atomic world, and especially for the uncertainty principle in quantum theory. He is also known for his controversial role as a leader of Germany's nuclear fission research during World War II. After the war he was active in elementary particle physics and West German science policy
Albert Einstein 1875-1955
What he did!
Albert Einstein’s theories solved centuries-old problems in physics and rocked even non-physicists’ view of the world.
E=MC2
Albert Einstein’s theories solved centuries-old problems in physics and rocked even non-physicists’ view of the world. This is what is meant by paradigm change.
How he changed science
In 1905, Einstein published five papers in the German Yearbook of Physics, three of them groundbreaking.
Einstein's first principle
The motion of particles suspended in liquid: He developed a mathematical formula to explain that the visible motion of particles was due to the invisible motion of the molecules of the liquid.
Einstein's second principle
The photoelectric effect, or the release of electrons from metal when light shines on it: Einstein explained it in terms of quanta, or packets of energy. Einstein received the Nobel Prize in physics for this paper, “for his services to Theoretical Physics, and especially for his discovery of the law of photoelectric effect.”
Einstein's third principle
Einstein published his special theory of relativity. This reached the shocking conclusion that time, weight or mass are not constant. When moving at high speeds all of these things get compressed; only the speed of light remains the same. That happens because energy is equal to mass times the speed of light squared, or e=mc2.
How this changed age old concepts
Several old truths became untrue or at least questionable.
1. The principle of identity doesn't work (nothing can be itself and something else at the same time –light is)
2. No two portions of matter can occupy the same space at the same time
3. Movement without motion is impossible
E=MC2
Special theory of relativity: The most well-known, perhaps of Einstein’s careen or even the entire field of physics!
When first published, the article didn’t include the now-famous equation e=mc2, but later in 1905, he added it to another publication
The only constant—speed of light
The theory stated that the speed of light is constant and absolute—it always goes the same speed and nothing can go faster than that.
As things travel at speeds approaching the speed of light, strange things happen to them: They get shorter in the direction of travel, their mass increases, and time passes more slowly for them
Two chronometers
If you take two identical chronometers that are equally accurate and place one on the highest mountain and one at sea level, the one on the mountain will be two seconds slower after one year.
Why?
Good bye Sir Isaac!
All this was incredibly shocking to a world that saw Newton’s laws of physics as sacrosanct.
No longer Newton
The nature of the universe
Everyone knew that space had three dimensions and time only one.
Einstein put them together in one four-dimensional system where space and time cannot be separated or viewed independently.
What is Einstein's universe made of
Space-Time
E=mc2
Energy and mass are really the same: E=mc2. Energy equals matter times the speed of light squared. You only need a minute amount of matter, say an atom, to create tremendous amounts of energy.
Special Theory of Relativity
Einstein’s 1905 theory is the “special” theory because it is limited to bodies moving in the absence of a gravitational field.
General Relativity
It took Einstein eleven more years to formulate a set of general laws that took account of gravity. The result: Einstein’s second landmark paper on General Relativity.
Relativity and subjective time
Put your hand on a hot stove for a minute and it seems like an hour. Sit with a pretty girl for an hour and it seems like a minute. That’s relativity.
General and special theories
In 1916 Einstein expanded his Special Theory to include the effect of gravitation on the shape of space and the flow of time.
This theory, referred to as the General Theory of Relativity, proposed that matter causes space to curve.
The Big Bang
Present theories of how the cosmos began rest in part on Einstein’s work
Space-time and a new idea of gravity
Since the universe is made of space-time not matter and force, the idea of gravity as Newton saw it does not apply. It explains things on earth adequately but not in the universe as a whole.
There is a better explanation
Gravity
Earth has greater density than you do. So it bends space time more and that pulls you toward it. More dense bodies bend the fabric of the universe more than less dense ones. That all there is to it.
The Rubber Net analogy
Imagine how it works
If you have a rubber net and put a bowling ball and a ping pong ball on it. The bowling ball will bend the net more and pull the ping pong ball towards it.
Einstein's explanation
Smaller masses travel toward larger masses not because they are ‘attracted’ by a mysterious force. The smaller objects travel through space that is warped by larger objects.
Warping space time
Space Travel
Space travel might be possible if instead of moving from point A to B which is an enormous distance and could take centuries, enough energy could be generated to bend space-time so that Points A and B come close together. This is good science fiction and may be good science theory. Warp=Bend
Uniform gravitational field
Theory of General relativity: A uniform gravitational field (like that near the Earth) is equivalent to a uniform acceleration.
Newton was wrong (But of course he was British)
A person cannot tell the difference between (a) standing on the Earth, feeling the effects of gravity as a downward pull and (b) standing in a very smooth elevator that is accelerating upwards at exactly 32 feet per second squared. In both cases, a person would feel the same downward pull of gravity. Einstein asserted that these effects were actually the same.
Gravity as a curve
Einstein’s general theory of relativity describes gravity as a curvature of space-time caused by the presence of matter.
The more dense the object the greater its gravitational pull
Very massive or dense objects generate very strong gravity. The most compact objects imaginable are predicted by General Relativity to have such strong gravity that nothing, not even light, can escape their grip.
Most dense object
What is it?
Scientists call such an object a black hole. Why black? The main reason is that no light can escape from inside a black hole. It has, in effect disappeared from the visible universe.
How it happens
During most of a star’s lifetime, nuclear fusion in the core generates electromagnetic radiation, including photons; the particles of light. This radiation exerts an outward pressure that exactly balances the inward pull of gravity caused by the star’s mass.
Birth of a black hole
As nuclear fuel is exhausted, the outward forces of radiation diminish, allowing the gravitation to compress the star inward. The contraction of the core causes its temperature to rise and allows remaining nuclear material to be used as fuel. The star is saved from further collapse…but only for a while. Eventually, all possible nuclear fuel is used up and the core collapses. If the star is sufficiently massive or compressible, it may collapse to a black hole.
Niels Henrik David Bohr1886-1962“
Nils Bohr
“For his services in the investigation of the structure of atoms and of the radiation emanating from them.”
The most radical thinker
Einstein was a great theorist who changed the paradigm of science. However Nils Bohr was even more radical and was willing to throw out all old ideas. Einstein was not.
Both important
Together their work created the new paradigm. Einstein concerned himself with the vast space of the universe. Bohr was concerned with the tiny particles that make up everything including objects on earth.
Restructuring the atom
In 1911, Bohr traveled to England on a study grant and worked under J. J. Thompson, who had discovered the electron 15 years earlier. Bohr began to work o the problem of the atom’s structure. Ernest Rutherford had recently suggested the atom had a miniature, dense nucleus surrounded by a cloud of nearly weightless electrons.
Problems with old model
There were a few problems with the model, however. For example, according to classical physics, the electrons orbiting the nucleus should lose energy until they spiral down into the center, collapsing the atom.
Bohr's model
Bohr proposed adding to the model the new idea of quanta put forth by Max Planck in 1901. That way, electrons existed at the set levels of energy, that is, at fixed distances from the nucleus. If the atom absorbed energy, the electron jumped to a level further from the nucleus; if it radiated energy, it fell to a level closer to the nucleus.
Changing the paradigm
His model was a huge leap forward in making theory fit the experimental evidence that other physicists had found over the years. A few inaccuracies remained to be ironed out by others over the next few years, but his essential idea was proved correct. He received the Nobel Prize in 1922, and it’s what he’s most famous for. He was only 37 at the time
Niels Bohr also developed
the theory of the nucleus as a liquid drop
the idea of “complementarity” –that things may have a dual nature(as the electron is both a particle and a wave) but we can only experience one aspect at a time.
Later work
Niels Bohr demonstrated that uranium 235 is an isotope that splits to form other atoms. he moved to the United States during World War II and worked on development of the first atomic bomb. After World War II he returned to Holland and began work on peaceful uses of atomic energy. Niels Bohr died in Holland on November 18, 1962.
The wave-particle duality of light and matter
In 1690 Christiaan Huygens theorized that light was composed of waves.
In 1704 Isaac Newton explained that light was made of tiny particles.
Dual theories
Experiments supported each of their theories. However, neither could explain all of the phenomena associated with light! Scientists (especially Bohr began to think of light as both a particle and a wave.
Louis de Broglie
In 1923, as part of his PhD Thesis, Louis de Broglie argued that matter has the same ambiguity of possessing both particle and wave properties.
He suggested that:
Quantization could be observed everywhere experimentally and asserted in an ad hoc fashion Bohr’s theory arose from this wave property of matter.
Schrodinger's theory
Schrodinger developed a wave equation for matter. His work is the foundation of all our modern physical theory.
Quantum Mechanics
Quantum Mechanics is the study of matter and radiation at the atomic level.
Quantum Mechanics has given us a clear understanding of colors, energies and atoms, and provides the foundation for all modern electronics, lasers and space exploration
How can something be both a particle and a wave at the same time?
Do not think of light as a stream of articles moving up and down in a wavelike manner. Light and matter exist as particles.
Particle of light as a probability
It is the probability of where that particle will be that behaves like a wave.
Explanation
The reason that light sometimes appears to act as a wave is because we are noticing the accumulation of many of the light particles distributed over the probabilities of where each particle could be.
Reality is mathematical
Bohr saw the electron as a probability and, thus, established a mathematical basis of reality.
Pythagoras
In the 8th century BC, the Greek philosopher and mathematician, Pythagoras claimed that reality is mathematical. Bohr proved him right
Albert Einstein and Niels Bohr
Their debate
One of the most sparkling and prolonged scientific jousting matches took place between Niels Bohr and Albert Einstein in the 1920’s and 30’s.
Their Debate
Einstein, who could never accept the probabilistic, stochastic nature of quantum mechanics, “thought experiments” designed to disprove the new theory.
Bohr would then attempt to show where Einstein had gone wrong.
Bohr the more radical thinker
In one of Bohr’s successful attempts at this, he was especially pleased to note that Einstein had forgotten that according to his own theory of general relativity clocks run more slowly under the influence of a gravitational field. Thus, probability was inherent in Einstein’s own relativity theory.
The New Paradigm in Science
The new paradigm in science that appeared in the early 20th century challenged and then refuted many of the accepted truths of the older paradigms in science. Most important among these are:
Principles of new paradigm
That existence is composed of matter and energy. (Einstein’s theory of special relativity refutes this and makes the universe one composed of space-time.
The the relationship between objects and forces is orderly and predictable (mechanistic)
Principles continued
The principle of identity, i.e. that nothing can be both itself and something else at the same time (Bohr’s duality concept does not allow this age old principle)
The principle of non-convergence, i.e. “no two portions of matter can occupy the same space at the same time.” (Again, Bohr’s description of the quark and of probability particles refutes this principle.)