The Story of Physics: The Story of Physics Slide4: Physics is perhaps, a science which answers or tries to answer our most basic questions regarding nature and everything around us.
Curiosity demands that we ask questions.
Physics is a way of trying to answer these questions.
A definition Slide5:
Over the past few centuries, Physics has evolved into a very systematic sort of practice.
Observation, reason and experiment make up what is Physics! The Story Begins……:
The Story Begins…… Astronomy: Astronomy The branch of physics that studies celestial bodies and the universe as a whole
Astronomy is the oldest of the sciences. When StoneAge humans turned to an agrarian way of life and began to settle into communities, their interest must naturally have turned to the "heavens“.
As a subject of investigation among the Chinese; Greeks; Romans; and Muslims, Astronomy entered into the 15th century. Nicholas Copernicus (1473-1543): Nicholas Copernicus (1473-1543) A Polish priest who studied in Renaissance Italy at the University of Padua –
Mathematics, Astronomy, Medicine and Theology made up the curriculum. His idea of a heliocentric [sun-centered] universe was a mental breakthrough
A beautiful idea; ugly details
Sticks with the circular orbits of planets, some say he was obsessed with circles
Gives new knowledge, planetary distances
Most importantly, initiated further progress in Astronomy and Physics Nicholas Copernicus (1473-1543): On the Revolution of the Heavenly Bodies 1543 Nicholas Copernicus (1473-1543) De Revolutionibus Orbium Caelestium Slide10: An Italian Astronomer and Physicist performed fundamental observations, experiments, and mathematical analyses in astronomy and physics;
discovered mountains and craters on the moon,
the phases of Venus,
and the four largest satellites of Jupiter:
Io, Europa, Callisto, and Ganymede Galileo Galilie (1564-1642) Slide11: Galileo Galilie (1564-1642) Galileo’s work
on projectiles Galileo’s famous
telescope Galileo Galilie (1564-1642) : Galileo Galilie (1564-1642) Johannes Kepler (1571-1630): Johannes Kepler (1571-1630) Kepler's Laws of Planetary Motion
In 1605 he announced The First Law:
Planets move in ellipses with the Sun at one focus.
Prior to this in 1602, Kepler found from trying to calculate the position of the Earth in its orbit that as it sweeps out an area defined by the Sun and the orbital path of the Earth that:
The radius vector describes equal areas in equal times. (The Second Law)
On May 15, 1618 he discovered The Third Law:
The squares of the periodic times are to each other as the cubes of the mean distances.
Kepler can truly be called the founder of celestial mechanics.
A German Physicist Johannes Kepler (1571-1630): Johannes Kepler (1571-1630) Verification of Kepler’s Laws by precise instruments in outer space today.
The depth of his rigorous experimental work in the late 16th century shows the curiosity to unveil the hidden secrets of the universe! Sir Isaac Newton (1642-1727): Sir Isaac Newton (1642-1727) An English Mathematician and Physicist developed theories of gravitation and mechanics, and invented differential calculus The Law of Inertia
F = ma
The Law of Action and Reaction
F = G m1m2 / r2 ř Sir Isaac Newton (1642-1727): Sir Isaac Newton (1642-1727) The Principia is recognised as the greatest scientific book ever written.
Newton analysed the motion of bodies in resisting and non-resisting media under the action of centripetal forces.
The results were applied to orbiting bodies, projectiles, pendulums, and free-fall near the Earth.
He further demonstrated that the planets were attracted toward the Sun by a force varying as the inverse square of the distance and generalised that all heavenly bodies mutually attract one another. An English Mathematician and Physicist Sir Isaac Newton (1642-1727): Sir Isaac Newton (1642-1727) Further generalisation led Newton to the law of universal gravitation:-
... all matter attracts all other matter with a force proportional to the product of their masses and inversely proportional to the square of the distance between them. An English Mathematician and Physicist Astronomy after the Newton’s Law of Universal Gravitation: Astronomy after the Newton’s Law of Universal Gravitation Newton’s Laws applied to motion of the celestial bodies.
Some wobbling observed in the case of Jupiter, Saturn, and Uranus.
For Jupiter and Saturn all was well
But, Uranus was “weird”!
Newton’s Laws seemed unable to account for its motion
A completely well established truth was being falsified under the very eyes of those who believed in it as a divine truth
Was there a different equation for Uranus?
Slide19: Urbain Le Verrier (1811-1877)
A French Astronomer and Mathematician On 3 July 1841, while still an undergraduate, Adams made a note that he had decided to investigate:-
... the irregularities of the motion of Uranus...in order to find out whether they may be attributed to the action of an undiscovered planet beyond it. John Couch Adams
A British Physicist and Mathematician As one of his colleagues said:-
... he discovered a star with the tip of his pen, without any instruments other than the strength of his calculations alone. These two thought otherwise! Slide20: A Great Success of Theoretical Physics ! Slide21: Benjamin Franklin (1706–1790)
the first American physicist;
characterized two kinds of electric charge, which he named “positive” and “negative” American Statesman and Inventor If you would not be forgotten as soon as you are dead & rotten, either write things worth reading, or do things worth the writing. —Benjamin Franklin Slide22: Charles Augustin De Coulomb
experiments on elasticity, electricity, and magnetism; established experimentally nature of the force between two charges
F = q1q2/4πξ0r2 ř A French Physicist Andre` Marie Ampere (1775-1836): Andre` Marie Ampere (1775-1836) The father of electrodynamics
A French Physicist Ampère made important contributions to the theory of Electricity and magnetism. His theory became fundamental for 19th century developments. Michael Faraday (1791-1867): Michael Faraday (1791-1867) English bookbinder who became interested in electricity. discovered electromagnetic induction and devised first electrical transformer One of his most important contributions to physics was his development of the concept of a field to describe magnetic and electric forces in 1845. He first suggested that current produces an electric "tension" which produces an "electrotonic state," or polarization of matter molecules, and is responsible for transmitting the electric force. After further experimentation, he abandoned the concept of electrotonic forces in favor of "lines of force." He maintained that these lines could be made visible in a magnet using iron filings. Slide25: Carl Friedrich Gauss
German mathematician who is sometimes called the “Prince of Mathematics." Gauss worked in a wide variety of fields in both mathematics and physics including the number theory, analysis, differential geometry, geodesy, magnetism, astronomy and optics. His work has had an immense influence in many areas. The most prolific Mathematician in History Slide26: The Unification of Electrodynamics with Magnetodynamics propounded the theory of electromagnetism; developed the kinetic theory of gases : propounded the theory of electromagnetism; developed the kinetic theory of gases
In London, around 1862, Maxwell calculated that the speed of propagation of an electromagnetic field is approximately that of the speed of light. He proposed that the phenomenon of light is therefore an electromagnetic phenomenon.
Maxwell wrote the truly remarkable words:-
We can scarcely avoid the conclusion that light consists in the transverse undulations of the same medium which is the cause of electric and magnetic phenomena.
James Clerk Maxwell
(1831-1879) A Scottish Physicist Slide28: When the Edinburgh paper, the Courant, reported the result it noted that:-
Professor Maxwell is already acknowledged to be one of the most remarkable men known to the scientific world.
James Clerk Maxwell
(1831-1879) Maxwell’s Equations: Maxwell’s Equations The Differential form The Integral form And God said, And there was Light! Albert A. Michelson Edward Morley: Albert A. Michelson Edward Morley Albert A. Michelson
The Nobel Prize in Physics-1907 German-born American They devised an interferometer and used it to try to measure Earth's absolute motion; precisely measured speed of light Morley, Edward
A US Physicist who collaborated with Michelson The Michelson-Morley experiment, one of the most important and famous experiments in the history of physics, was performed in 1887 at what is now Case Western Reserve University, and is considered to be the first strong evidence against the theory of a luminiferous aether. The Michelson Morley Experiment: The Michelson Morley Experiment The Michelson Morley Experiment: The result of the experiments showed no such shifts (null result). The change in the path difference of the beams by one wave length <=> a shift of one fringe. The Michelson Morley Experiment The most famous failed experiment: The most famous failed experiment Hendrik Antoon Lorentz (1853-1928): Hendrik Antoon Lorentz (1853-1928) Introduced Lorentz transformation equations of special relativity; advanced ideas of relativistic length contraction and relativistic mass increase; contributed to the theory of electromagnetism In 1895, Lorentz concluded that the "null" result obtained by Michelson and Morley was caused by a effect of contraction made by the ether on their apparatus and introduced the length contraction equation
where L is the contracted length, L0 is the rest length, v is the velocity of the frame of reference, and c is the speed of light. A Dutch Theoretical Physicist The Black Body Problem: The Black Body Problem During the studies of Thermodynamics in the 18th century, a new concept was introduced into Physics, that of the radiation emitted by heated objects.
Two experimental observations
Temperature of the black body is directly proportional to the intensity of the emitted radiation (Stephan Boltzmann Law)
The higher the temperature, the shorter the wavelength of the most intense part of the spectrum (Wein’s Law)
But no one could explain the function R(λ,T) quantitaively, and suggest an equation that could fit all data! Max Karl Planck (1858-1947) : Max Karl Planck (1858-1947) formulated the quantum theory; explained wavelength distribution of blackbody radiation
Solved the famous Black Body Problem and gave the magical function which agreed remarkably with the Black Body Experimental Curves A German Theoretical
The Nobel Prize in Physics -1918 The Problems in Physics in 1905: The Problems in Physics in 1905 The null result of the Michelson Morley Experiment
Paradox of the constancy of the speed of light
The unexplainable Photoelectric effect
Maxwell’s Equations versus Newtonian Mechanics
No physical understanding and interpretation of Lorentz Transformations Albert Einstein (1879-1955): Albert Einstein (1879-1955) Einstein contributed more than any other scientist to the modern vision of physical reality. His special and general theories of relativity are still regarded as the most satisfactory model of the large-scale universe that we have. Born in Ulm, Germany in 1879, Albert Einstein is still considered one of the greatest scientific and mathematical geniuses in history.
In 1905, at the age of 26, he set forth his theory of relativity which discards the concept of time and space as absolute entities, and views them as relative to moving frames of reference.
At the same time, he postulated light quanta or photons, comparable to energy quanta, and on these based his explanation of the photoelectric effect. A German born US Theoretical Physicist
The Nobel Prize in Physics - 1921 Slide40: Albert Einstein (1879-1955) A German born US Theoretical Physicist
The Nobel Prize in Physics - 1921 In 1911, he asserted the equivalence of gravitation and inertia.
In 1916, he completed the mathematical formulation of his general theory of relativity, which included gravitation as a determiner of curvature of space-time continuum and represented gravitation as a field rather than a force.
In 1921, he won the Nobel Prize for his contributions to theoretical physics, especially for his work on the photoelectric effect.
In 1950, he presented his unified field theory, which attempts to explain gravitation, electromagnetism, and subatomic phenomena in one set of laws. He completed it’s mathematical formulation in 1953, just two years before his death in 1955 at the age of 76. The Special Theory of Relativity: The Special Theory of Relativity The laws of physics take the same form in all inertial frames.
In any inertial frame, the velocity of light c is the same whether the light is emitted by a body at rest or by a body in uniform motion. The Photoelectric Effect: The Photoelectric Effect Slide43: Albert Einstein (1879-1955) Einstein’s Legacy: Einstein’s Legacy Such incredible accomplishments for one individual! Yet, Einstein wrote in an essay entitled, SELF PORTRAIT,
"For the most part, I do the thing which my own nature drives me to do. It is embarrassing to earn so much respect and love for it.”
Schopenhauer’s saying “A man can do as he will, but not will as he will,” an inspiration to Einstein since his youth, seemed to express the basis of his humility. So what was the nature, the will, of the man himself? Einstein’s Legacy: Einstein’s Legacy ……A hundred times every day I remind myself that my inner and outer life depend on the labours of other men, living and dead, and that I must exert myself in order to give in the same measure as I have received
The most incomprehensible fact about the universe is that it is comprehensible
The search for truth is more precious than its possession
Before God we are all equally wise - equally foolish