A.A. Michelson (velocity of light):

(1852-1931) American physicist famous for his work on measuring the speed of light & the Michelson–Morley experiment.  In 1907 he became the first American to win the Nobel Prize in a science (Physics).  He was founder & first head of the physics department  University of Chicago.  In 1869 he started planning a repeat of the rotating-mirror method of Foucault for measuring the speed of light, using improved optics & longer baseline.  He conducted preliminary measurements with improvised equipment in 1878.  Michelson's formal experiments took place in June and July 1879. He constructed a frame building at the Naval Academy (Annapolis) to house the machinery.  He published his results which set the speed of light at 299,910 ± 50 km/s in 1879.  He continued to "refine" his method and in 1883 published a measurement of 299,853 ± 60 km/s.

 

Lorentz (mathematic theorems for relativity):

For the special theory of relativity of 1905 (originally called the Lorentz–Einstein theory) Einstein used many of the concepts, mathematical tools & results that Lorentz discussed, indeed Lorentz had laid the groundwork.  Lorentz & others tried to explain how the speed of light was observed to be independent of the reference frame & understand the symmetries of the laws of electromagnetism. Between 1892-1904 he worked on describing electromagnetic phenomena in reference frames that move relative to the postulated luminiferous aether.   His 1904 paper includes the covariant formulation of electrodynamics, in which electrodynamic phenomena in different reference frames are described by identical equations with well-defined transformation properties; it was significant as it showed the outcomes of electrodynamic experiments do not depend on the relative motion of the reference frame.

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Minkowski (mathematic theorems for relativity):

In 1908 Minkowski realized that Einstein’s special theory of relativity could best be understood in a 4-dimensional space where time & space were not separated but intermingled in a 4 dimensional space-time.  "Minkowski spacetime" is a combination of 3-dimensional Euclidean space and time into a 4-dimensional manifold where the spacetime interval between any 2 events is independent of the inertial frame of reference in which they are recorded. Minkowski space is associated with Einstein's theories of special & general relativity and is the most common mathematical structure on which special relativity is formulated.

 

absolute time (relativity theory):

time is relative; every event can be assigned 4 numbers representing its time & position (the event's coordinates).  However, the numerical values are different for different observers.  The question of what time it is now only has meaning relative to a particular observer. 

 

Astronomical discoveries (proof of relativity):

In 1916 Einstein proposed 3 tests to establish observational evidence for the theory of general relativity:

• the perihelion precession of Mercury's orbit

• the deflection of light by the Sun

• the gravitational redshift of light

The deviation of Mercury from the precession predicted by Newtonian mechanics was recognized in 1859.  All previous solutions to explain this were uniformly unsuccessful.  In 1915 Einstein showed how the deviation was due to gravitation being mediated by the curvature of spacetime.  The Eddington experiment of 1919 first observed light deflection.  The expeditions measured the gravitational deflection of starlight passing near the Sun (as seen during a solar eclipse).  The deflection was predicted by Einstein in 1911.  The results were presented to the Royal Society of London; after some deliberation, they were accepted.  In 1907 Einstein predicted the gravitational redshift of light.  Astronomers believed the gravitational redshift of light might be measured in the spectral lines of a white dwarf star, which has a very high gravitational field.  An attempt was made in 1925 using the spectrum of Sirius-B but the results were considered unusable.

 

Radioactivity:

property exhibited by certain types of matter of emitting energy & subatomic particles spontaneously, an attribute of individual atomic nuclei whereby an unstable atomic nucleus loses energy; 3 common types of decay are: alpha, beta & gamma, all of which emit 1 or more particles or photons.  In the 19th century, experimenters began to detect unexpected forms of radiation: Wilhelm Röntgen discovered X-rays (1895); Henri Becquerel discovered radiation emission (1896); J. J. Thomson discovered the electron (1897), the Curies discovered new radioactive elements (1898).  Rutherford & Soddy identified 2 of Becquerel's forms of radiation with electrons & helium & identified alpha ray and beta ray (1899); in 1911 using experimental evidence Rutherford described the atom as a dense, positively charged nucleus surrounded by negatively charged electrons.

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Thermodynamics:

branch of physics concerned with the relations between heat and mechanical energy or work, and the conversion of one into the other; the behaviour of these quantities is governed by the 4 laws of thermodynamics which convey a quantitative description using measurable macroscopic physical quantities;  modern thermodynamics deals with the properties of systems for the description of which temperature is a necessary coordinate.

 

statics (antique):

branch of mechanics concerned with the analysis of loads, force & torque (or "moment") acting on physical systems that do not experience acceleration but are in static equilibrium with their environment.  The mathematicians & scientists who developed this field were Hellenic Greeks & Romans, notably Aristotle (384–322 BC), Euclid (flourished 300 BC in Alexandria, wrote Elements), Archimedes (287-212 BC On the Equilibrium of Planes, On Floating Bodies) & Ptolemy (100-179 AD, in Alexandria, wrote Optics, Harmonics).

 

Western dynamics (knows only such quantities):

branch of physical science, subdivision of mechanics, concerned with the motion of material objects in relation to the physical factors that affect them (force, mass, momentum, energy); it subdivides into: kinematics (describes motion, without regard to its causes, in terms of position, velocity & acceleration), kinetics (concerned with the effect of forces) and torques (concerned with the motion of bodies having mass).  Galileo laid the foundations of dynamics late 16th century when he recognized force as the cause of changes in the velocity of a body.  Newton formulated this idea in the 17th century (his 2nd law of motion).

 

mass (classical):

In Newtonian physics the mass of an object is related to how much matter it contains, it is the object’s ability to resist a given force (a body’s inertial mass) & so mass is associated with the concept of inertia).  In Newton’s second law the force (F), on a body is equal to the mass (m), times the acceleration (a) [F=ma] making mass is equal to Force divided by acceleration [m=F/a.]

 

quantum:

the minimum amount of any physical entity (physical property) involved in an interaction; a physical property can be "quantized" meaning the magnitude of the physical property can take on only discrete values consisting of integer multiples of one quantum; the energy of an electron bound within an atom is quantized & can exist only in certain discrete values

 

atomic ideas of Rutherford and Bohr:

see page 385 above

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atom (as planetary world): * see Endnote<C>

reference to the Planetary Model or Rutherford model (1911), based on Rutherford-Geiger–Marsden experiments of 1909.

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atom (as atom-swarms): * see Endnote<D>

reference to the plum pudding model, one of several models of the atom current at the time; it was superseded by the Rutherford model in 1911 (see above)