Selected developments in Physics during the last few centuries E. Matsinos ([email protected])

Selected developments in Physics during the last few

centuries

E. Matsinos ([email protected])

Is this the end of Physics? 2

On how progress is made

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Complacency

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Dissension

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Maximisation of activity (mainly by theorists)



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Nothing seems to make senseCreativity phase



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Complacency

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The scientific method

“Principles and procedures for the systematic pursuit of knowledge involving:– the recognition and formulation of a problem,– the collection of data through observation and

experiment, and – the formulation and testing of hypotheses”

[Webster's dictionary]

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From Mythology to Geometry

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Eratosthenes of Cyrene (276 BC – ca. 195 BC)

First measurement of the Earth radius

First measurement of the Moon radius (eclipse)

First measurement of the Earth-Moon distance



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Aristarchus of Samos (310 BC – ca. 230 BC)

First measurement of the Earth-Sun distance (a factor of 20 off!)

First measurement of the Sun radius



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Aristarchus of Samos (310 BC – ca. 230 BC)Heliocentric Cosmology

Why was Aristarchus’ Heliocentric Cosmology not accepted?

o If the Earth moved, there should be constant ‘wind’ and the ground should disappear under our feeto If the Sun were the centre of the universe, then all objects (on the Earth) should fall onto (move toward) ito Stellar parallax

Friedrich Wilhelm Bessel, 1838; 313.6 mas (0.00008710)

Today’s value: 287.18 mas (→ 11.36 ly)



Claudius Ptolemy (ca. 90 – 168)

o Almagest: the only surviving comprehensive ancient treatise on astronomy

o Tables to compute future (or past) positions of the Sun, Moon, and planets; also the rising and the setting of the stars

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Geocentric Cosmology


Medieval Cosmology

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Wycliffe Translation

Psalm 93:1

for he [the Lord] made steadfast the world; that shall not be moved

Psalm 96:10

and he [the Lord] hath amended the world, that shall not be moved

Psalm 104:5

which hast founded the earth on his stableness; it shall not be bowed into the world of world

1 Chronicles 10:3

for he [the Lord] hath founded the world unmoveable

Ecclesiastes 1:5

the sun riseth, and goeth down, and turneth again to his place; and there it riseth again


Starting the scientific revolution

Nicolaus Copernicus (1473 – 1543)• Heliocentric Cosmology removed the Earth from its

privileged status of being the ‘centre of the universe’

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De revolutionibus orbium coelestium, 1543


Starting the scientific revolution

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From Copernicus' Commentariolus (1514):1. There is no one centre of all the celestial circles or spheres.2. The centre of the Earth is not the centre of the universe, but only of gravity and of the

lunar sphere.3. All the spheres revolve about the Sun...4. ... the distance from the Earth to the Sun is imperceptible in comparison with the height of

the firmament.5. Whatever motion appears in the firmament arises not from any motion of the firmament,

but from the Earth's motion. The Earth ... performs a complete rotation on its fixed poles in a daily motion, while the firmament and highest heaven abide unchanged.

6. What appear to us as motions of the Sun arise not from its motion but from the motion of the Earth ... We revolve about the Sun like any other planet.

7. The apparent retrograde and direct motion of the planets arises not from their motion, but from the Earth's. The motion of the Earth alone, therefore, suffices to explain so many apparent inequalities in the heavens.


Observations

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Haec immatura a me iam frustra leguntur oy(These are at present too young to be read)

Cynthiae figuras aemulatur Mater Amorum(Cynthia's figures are imitated by the Mother of Love)


HistoryIsaac Newton (1642 – 1727)• Foundation of Classical Mechanics

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History

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• The nature of light – Newton (particle aspect)– Huygens (wave aspect)– Rømer (c is finite, Io’s eclipses, 1676)– Young’s experiment (1803)

• The classification of the elements– Lavoisier– Gay-Lussac– Mendeleyev

• Electromagnetism– Ørsted– Faraday


History

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0/ E

0 B

t

BE

t

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cjB

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1

Differential form of Maxwell’s ‘microscopic’ equations

Gauss’ law

Gauss’ law for magnetism

Faraday’s law

Ampère’s law


History

Classical Physics

• Gravitation (Newton)• Electromagnetism (Maxwell)

Galilean transformation

• Open questions/problems– Invariance of laws of Physics– Relativity principle– Introduction of aether– Structure of matter

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History

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The Michelson–Morley experiment (1887)

Aimed at detecting the relative motion of matter relative to the luminiferous aether (aether wind)

Negative result


History

Albert Einstein (1879 – 1955)

Special Theory of Relativity (1905)

General Theory of Relativity (1915)• Strong gravitational fields distort the

space-time• It did not take long for GR to be tested

and verified– precession of Mercury’s perihelion, – deflection of light of remote galaxies, …

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History

• General Relativity generalises Special Relativity and Newton’s law of universal gravitation, providing a unified description of gravity as a geometric property of space-time

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T

c

Gg

RR

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T

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Ggg

RR

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History

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Correction (arcsec/century) Cause

531.63±0.69 Gravitational tugs of the other planets

0.0254 Oblateness of the Sun (quadrupole moment)

531.66±0.69 Total ‘theoretical’

574.10±0.65 Observed

Precession of the perihelion of Mercury’s orbit

Recognised in 1859 as a problem in celestial mechanics by Urbain Le Verrier (re-analysis of the transits of Mercury over the Sun’s disk from 1697 to 1848); Le Verrier estimated an anomaly of 38 arcsec/century

Correction (arcsec/century) Cause

531.63±0.69 Gravitational tugs of the other planets

0.0254 Oblateness of the Sun (quadrupole moment)

42.98±0.04 General Relativity

574.64±0.69 Total ‘theoretical’

574.10±0.65 Observed


An ‘extreme case’ of precession

• Binary-star system: two neutron stars (M~1.4M☼) orbiting each other → precession of the periastron: 4.20 yr-1

o T=7.751939106 hro e=0.617131o a=1,950,100 kmo Rate of decrease of orbital period: 76.5 ms/yro Rate of decrease of semi-major axis: 3.5 m/yro Calculated lifetime: 300 Myr

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PSR B1913+16 (Hulse–Taylor binary pulsar)


History

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Gravitational deflection of light

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4

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GM 75.1 arcsec


History

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Gravitational deflection of light


HistoryThe ray-frenzy era

Röntgen von LaueBequerel Curie’s Rutherford

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First Solvay Conference, 1911


History

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‘… as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you’

Plum-pudding model

First ‘realistic’ model of the atom


HistoryQuantum mechanics

PlanckRutherford Bohr Pauli Heisenberg Schrödinger de BroglieBorn Dirac

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Fifth Solvay Conference, 1927


Fundamental forces and elementary particles (1st half of 20th century)

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Gravitation Electromagnetism Quantum Theory

Electron (Thomson, 1897)Proton (Rutherford, 1919)Neutron (Chatwick, 1932) - RutherfordAntielectron (Anderson, 1932) - DiracMuon (Anderson, 1936)Pion (Powell, 1947) - Yukawa

One problem solved (electrons in stable orbits), another remained

(stability of the nucleus)


Fundamental forces and elementary particles (2nd half of 20th century)

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Birth of Quantum Electrodynamics (QED)Feynman, Schwinger, and Tomonaga

(Maxwell’s equations + Quantum Theory + Special Theory of Relativity)



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Cockcroft-Walton

Cyclotron (Lawrence)

Synchrotron (McMillan)

1952: BNL, proton synchrotron, 3 GeV; Cosmotron



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1954: Berkeley, 6 GeV; Bevatron 1957: Dubna, 10 GeV; Synchrophasotron

1957: CERN, 28 GeV; PS ring

New particles were discovered with these accelerators

Further discoveries Electron neutrino (Cowen and Reines, 1953) - PauliMuon neutrino (Steinberger, Ledermann, and Schwartz, 1962)



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Gell-Mann and Ne’eman arranged the existing hadrons

in geometrical patterns

Gell-Mann predicted the existence of a new particle in

1962, discovered one year later

Friedman, Kendall, and Taylor showed that the proton has structure

Gell-Mann and Zweig introduced the quarks as

elementary blocks of matter

Baryons consist of three quarksMesons consist of a quark-antiquark pair

Introduction of ‘colour’

Quantum Chromodynamics (QCD) is born Fritzsch, Gell-Mann, and Leutwyler (early 1970s)

The six quarks (u, d, c, s, t, and b) are the building blocks of the hadrons and they interact by

exchanging gluons



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GR QED Weak QCD

Do these states really exist?

11/137 10-1310-38



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GR QED Weak QCD

ElectroweakGlashow, Weinberg, and Salam (Higgs, t’ Hooft)

First evidence for W+, W-, Z0 (UA1 and UA2, 1983)

First evidence for gluons (three-jet events, PLUTO, 1978)

Standard Model

The Higgs boson was tentatively confirmed to exist on 14 March 2013 (ATLAS and CMS, 4 July 2012)

~ 125


Unification: problems

• There is no real unification between the Electroweak interaction and QCD; they simply co-exist within the Standard Model

• There is little logics in the grouping of the elementary blocks of matter

• Fermion-boson asymmetry• The Standard Model contains 24 parameters which

cannot be obtained from ‘principles’• GRAVITY AND QUANTUM THEORY ARE

CONCEPTUALLY INCOMPATIBLE

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Unification: why bother?

• Order and simplicity• At the early times of the Universe, gravitation

was equally important as the other forces• Quantum fluctuations in the ‘primeval soup’

led to the creation of stars and galaxies

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Unification

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String Theory (1980s)

All the particles (and all forms of energy) in the Universe may be identified as one-dimensional, tiny 'strings'Our Universe is functioning in ten (or eleven) dimensions!

Five string theories have emerged and seem to be self-consistent!

M-theory (Witten, 1994)

‘The true sign of intelligence is not knowledge, but imagination’

[Albert Einstein]


Future

'The most important fundamental laws and facts of physical science have all been discovered, and these are now so firmly established that the possibility of their ever being supplemented in consequence of new discoveries is exceedingly remote... Our future discoveries must be looked for in the sixth place of decimals.'Albert Michelson, University of Chicago, 1894

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Thank you!

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E. Matsinos ([email protected])

Selected developments in Physics during the last few centuries E. Matsinos ([email protected])

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Transcript of Selected developments in Physics during the last few centuries E. Matsinos ([email protected])