Cosmology Summary by Ben Cheung from Time/Life Books
CHAPTER 1 LESSONS IN UNITY
Newton 1666 Horizontal Movement + Downward movement if equal in orbit.
1687 The Mathematical Principles of Natural Philosophy, Principia  motion mechanics true for many physical event, only at extremes of v and m do equ of Einstein relativity.
Gravity,EM,Strong nuclear (binds protons + neutrons in nucleus) , weak nuclear (controls radioactive decay).
THE ELECTRIC_MAGNETIC CONNECTION
Greeks, amber static, lodestone(magnetite).
1785 C.A. Coulomb elec&mag obey Newton's inversesquare law.
H.C. Orsted  an electric current produces magnetism
Faraday  A source of magnetism set in motion creates electricity.
Iron filings around magnet.
MATHEMATICIAN TO THE RESCUE
Maxwell  4 equations proving electricity and magnetism different aspects of same basic force.
Since elec. field can generate a mag field and vv. can sustain each other and propagate through space far beyond their originating charge or mag. source. and e field produces a B field which produces a e field. form of this propagation is a wave.
A NEW PERSPECTIVE
Sir J.J. Thomson 1897 electron : i = stream of negatively charged particles.
Planck accelerated e emit radiation in discrete amounts (quanta)
Einstein : light consists of particles : photons not waves. (actually both)
 velocity of EM waves is absolute.
 since light from stationary train same v as from moving one, so scales of time and distance different for each train relative to motion. mass proportional to its kinetic energy. E=mc^2.
E. Rutherford  Dense + q, w/ array of e
Niels Bohr 1913  w/ Planck's quantum principle : e restricted to specific orbits w.r.t. en. level. Moved levels by releasing photons.
THE QUANTUM WAY
e can make quantum leap, jump orbits wo/ traversing the space inbetween.
central to quantum physics : en shifts take place in discrete steps.
also discrete /quantized : charge, angular momentum, spin rate.
1927 W. Heisenberg. e occupy quantum states, @ distinct en levels transition w/ emission or absorption of photons.
wrote eqn (quantum mechanics) for en emissions  broke commutative law (AB=BA)
1924 L de Broglie think of e as waves not particles.
Shrodinger  1926 wave equations predict behavior of electrons. so en. transition caused by change in wave frequency.

GUARANTEED UNCERTAINTY
If know position precisely (define as a particle) can't describe its momentum.
If specify its momentum (its wavelike nature) then particleposition unpredictable.
Since photons are EM radiation, need EM field. (uncertainty principle). So need to know how photons and e interact : the quantum theory for EM fields : i.e. quantum field theory.
Dirac 1928 (QED)  apply quantum theory to dynamics of EM fields. Applied to relativity.
matter and energy are equivalent. Creation and annihilation. e(hi en)=e(low en)+photon.
Predicted antimatter. Matterantimatter total annihilation (particles = burst of pure en photons).
EM force made of particles.
When e influence each other , photon represent EM force carries from 1 to the other. Pop into existence via quantum fluctuation then disappear  virtual photons.
Heisenberg & Pauli, (e spin) : some QED calculations = infinity. Problem when tried to find interaction of an e w/ its own field. electron's selfenergy.
THE WEAK AND THE STRONG
1932  neutron , antimatter confirmed.
some radioactive minerals emit highly energized electrons from nucleus  beta decay
Protons are sometimes known as alpha particles and electrons as beta.
1927 en lost w/ e != en lost in nuclei. 1930 Pauli suggest another paricle also emitted.
Fermi 1933 explained beta decay as product of a new force  weak interaction.
Fermi : beta decay change n to a p+ w/ creation + emission of e and neutrino (hi en, no charge)
Fermi : weak and short range. Bombarded nuclei w/ neutrons (n).
nucleus = many p+'s so should repel. Why not?
1935 : Hideki Yukawa, new nuclear binding force, strong nuclear force.
in nucleus : n turn into p+ & p+ to n. by exchanging virtual particle w/ (+) or () q. This flow = strong force.
Short range. virtual exchange particle = meson. Meson decay triggered by weak force. so meson can break into e and antineutrinos (beta decay).
1932 Anderson discover e+, in cloud chamber w/ cosmic rays. 1936 discover muon
1946 discover pion  strong force carrier.
QED'S TRIUMPH
1965 J.S. Schwinger, R.P. Feynman, S. Tomonaga. Used renormalization  took out infinities from QED.
mass of e w/ selfen + bare mass (unobservable), so can assign it infinite negative value , offset possitive infinity.
1954 C.N. Yang+R. Mills. Symmetry = Maintenance of a certain measurable value in the face of some kind of alteration.
EM in terms of symmetry : c same regardless of change in motion.
gauge invariance (gauge = standard of measurement). EM field is gauge invariant. Rules governing it do not change over the extent of its range, symmetry is preserved.
So : starting pt is ID a symmetry and mathematically build a gauge field to maintain it.
QUARKS, BY FLAVOR AND COLOR
1961 GellMann propose : hadrons organized so to maintain underlying symmetry despite variance in particle characteristics. (Y. Ne'eman same conclusion)
Gellmann (same time G. Zweig) symmetry arrangement if particles affected by the strong force were composed of different combination of smaller particles. Quarks.
Quarks : up,down,strange,bottom,top,charm.
1971 Fritzsch+GellMann QCD : theory to explain ho quarks combine , w/ color (qv charge)
red, green, blue, various allowed combinations. What holds quarks together?  gluons.
NEW COMBINATIONS
Yang+T.D. Lee , found breakdown of symmetry in weak reaction w/ kaons.
Glashow : 50's employed gauge principle (w/ symmetry maintained), to come up w/ unified theory of EM and weak force.
Predicted existence of weak force bosons, (analogous to photon). W+, W carried charge to account for the fact beta decay sometimes transmitted () or (+) charge. Z was neutral.
Theory had infinities. renormalize. But only if electroweak carriers were massless. W+/W/Z not massless.
THEN THERE WERE THREE
A. Salam, S. Weinberg, Glashow (electroweak theory). Key is broken symmetry
Build of Jeff Goldstone & Peter Higges concepts. Salam + Weinberg showed photons and weak force bosons different manifestations of the same fundamental entitiy. The 3 distinguishable by breaking of previously intact symmetry. Allows massless bosons to pick up mass.
Gerard 't Hooft used ingenious math technique that banished infinities.
Detect W&Z bosons to confirm electroweak theory.
GUT : try to merge strong nuclear w/ electroweak.
1974 Glashow + Georgi, a GUT w/ gluons,photons,weak force bosons,e indistinguishable. Key is at extremely high energy various particles & forces became interchangeable.
So : comology : space had hi en. forces united. After cooling , strong & electroweak become distinct.
Can test w/ proton decay, so far not observed.
THE MISSING PLAYER
GUT ignore gravity. Einstein tried to unify gravity w/ EM. w/ Quantum field theory, gravitation field must have a quantum particle = graviton.
But couldn't get quantum theory of gravity to work.
CHAPTER 2 SEARCH OF QUANTUM GRAVITY
Einstein showed acceleration results from gravity. Relativity 1915 massive objects warp the fabric of spacetime. A ball follows the shortest path in a warped space surface.
Planck radiation comes in discrete packets. Quantum of action (Planck's constant).
w/ c & g get fundamental unit of distance and time. Planck length 10^33cm.
Need to find a way to quantize gravity. gravity interactions @ elementary particle level.
DIMENSIONAL GROUNDWORK
1919 T. Kaluza : reworked relativity equations in 5 (vs4) dimensions, it generated an extra set of equations , which turned out to be the same as J.C. Maxwell's (for EM field).
He had unified gravity and EM. But what IS 5th dimension?
1926 O. Klein : 5th dimension is minute so as to be imperceptible even at a subatomic scale. (hosepipe /line example).
Today, all representation of fields, or architecture of space in >4 dim. are classified as KaluzaKlein theories.
SPACE ODDITIES
1927 Heisenberg : uncertainty  can't measure location and momentum simultaneously. e can be a wave (packet of en spread out over a volume) or as a particle (definite location but unknown momentum).
Schrodinger : a cat w/ radiactive gas. Since uncertainty governed atomic behavior  radiactive decay will be a probability, until you look to see if cat is dead or alive it will be both!
1928 Dirac QED equations, implied negative en states. Tenet of quantum physics : particles seek the lowest possible energy level. So all particles shoud be in negative energy states. Thus the antiparticle!
Virtual photons : pop in/out of existence by quantum fluctuation  create something from nothing. Since quantumscale volume of space can not be known w/ precision. Uncertainty principle. Space is filled w/ virtual particles
1973 Tryon realized quantum fluctuations can be of any size, large ones (w/ more energetic particles are just less frequent). A virtual particle of largest energy is big bang!
A NEW LANGUAGE
Traditional is geometry.
Topology : focus on relationships between surfaces, how they intersect, enclose or have discontinuities/holes (a square and circle are same can stretch , but a doughnut and cube are not must tear cube)
Wheeler 1957 : Wormhole  A rip or tear in the fabric of space  (topological transform sphere to doughnut), can open up a hole connecting two widely separated locations. Produced by quantum fluctuations in the topology of space @ the Plnck scale. By allowing extremely intricate spatial surfaces to be enfolded within a tiny region, within the folds of such a space, distant regions of the universe might come in contact with another.
Bottom up approach : Experimentalists; TopDown approach : Work from a framework of math & theories.
ON THE ROAD TO STRINGS
1968 Veneziano : Studies L. Euler. Found could use Euler's formula to create a model which described relationships in the Smatrix to predict particle interactions.
Smatrix (scattering matrix) particles from high energy collisions which scatter (a black box)
w/ Euler Smatrix is good tool for revealing inside of black box.
Problem : ghosts  negative probabilities. Only gone if reformulate in 26 dimensions.
w/ 26 coordinates to define positions within the Smatrix.
Veneziano's model similar to formulas describing how objects vibrate. Violin strings, vibrate to produce notes. Notes depend on tension, the string stores en and releases it at discrete intervals. In quantum : notes are unique localizations of en i.e. elementary particles.
1970 Y. Nambu  noticed correspondence between math of vibrating strings and Veneziano's eqns for behavior of hadrons. The model is equivalent to describing hadrons as if they were strings not particles.
Proposed strings length 10^13cm , and vibrations responsible for various types of hadrons.
Strings invisibly small, massless, elastic, travel @ v=~c. Vibrations & rot. followed quantum rules of discrete spin particles. Strings en level accounted for different kinds of hadrons.
STRINGS SIDETRACKED
Problems : How did string relate to quarks? Gellmann + Zweig , hadrons are combinations of quarks, yet string theory said hadrons are 1D vibrating strings. Maybe quarks @ the end of strings? Thus can't isolate a quark. If 3quarks , use Yshape quark.
Nambu's string theory did not encompass all hadrons. Nambu's theory only applied to integer spin, (thus hadrons which are bosons).
1971 P. Ramond formulated string theory to accommodate fermions.
J. Schwarz and A. Neveu came up w/ theory incorporating Ramond's. The resulting allembracing string theory included every type of hadron. The RNS theory only needed 10 dimensions (9space1 time) not 26.
1973 QCD took center stage, interest in strings faded.
KEEPERS OF THE FAITH
Schwarz and Scherk (S&S) still studied strings.
RNS theory predicted the hypothetical quantum of gravitation, the graviton.
S&S proposed, string might unify gravity and other forces if shrink string from 10^13cm (Nambu) to 10^33 cm (Planck scale).
THEORY AND SUPERTHEORY
Supersymmetry arises.
Global symmetry : involves identical changes everywhere throughout a system.
Local symmetry  underlying relatedness between diverse phenomena is maintained despite localized or different types of changes across the system.
Local symmetry applied to fields is gauge invariance. can explain how dissimilar forces can be unified.
EM,strong,weak = gauge forces (they exhibit local symmetry). Gravity not unified until supersymmetry is applied.
70s Wess, Zumino  find way to unify all types of fermions and bosons. via superspace (developed by Abdus Salam & J. Strathdee).
Superspace : +4 dimensions. Show that fermions and bosons really part of the same family. linked by supersymmetrical relationships.
Problem : Supersymmetry predicted every fermion & boson has a supersymmetrical partner (w/ "ino" suffix or "s" prefix) e.g. photons w/ photinos) not observed existed in Big Bang, supersymmetry broken in the cooler, lower energy state of the universe today.
Does it exhibit local symmetry? if so then a new gauge field w/ a new forcecarrying particle.(gravitino). A theory w/ all 4 fundamental forces?
Many supersymmetry models based on different symmetry groups. One provided solution to additional, unobserved dimensions. Described a process that caused extra dimensions to compactify or curl up into a minute structure and effectively disappear from view.
1976 Scherk,F. Gliozzi, D. Olive incorporated supersymmetry into string theory, incorporating graviton and gravitino. Essentially transformed RamondNeveuSchwarz strings into superstinrg.
THE EMERGENCE OF SUPERSTRINGS
1980 Schwarz & Green  came up w/ coherent theory describing superstring in a 10D version of spacetime. Type I
Type II superstrings w/ ends joined = closed loops.
The work was exhilarating "I never worked w/ such intensity in my life"
Problems w/ point particle theories is you get infinities.
W/ superstring theory Type I can be renormalized (infinities cancelled)
w/ type II, yields only finite results.
Problem w/ strings is 10dimensions, radical concept few followers
BREAKTHROUGH
Ed Witten & AlvarezGaume
Weak force has chirality. Assumed evenhanded universe (left/right symmetry) but this is broken by weak force. (qv p4043)
Witten showed chirality only w/ compactifying even # of dimensions. also showed 4 fources arise only from an odd # of dim. also showed most 10D theories have anomalies which lead to violations of convervation laws.
Most string theories have anomalies, but a single unique theory avoided this problem. w/ SO(32) symmetry group. 1984 Schwarz & Green reformulate Type I superstrings into requirements of SO(32) Symmetry group.
It was magical : supersymmetrical and chiral, and preserved the fundamental forces of the 4D universe, and no anomalies. And predicted the existence of gravity.
THE SUPERSTRING REVOLUTION
E8XE8 symmetry group also cancelled anomalies. D. Gross, J. Harvey, E. Martinec, R. Rohm (Princeton String Quartet). 1984. Theory w/ Type II closed strings w/ E8xE8 symmetry.
Dubbed Heterotic String theory (crossbred GreenSchwarz superstring model w/ VenezianoManbu string). Characteristics to distinguish particles by closed strings moving in opposite directions.
Heterotic strings 10D in one direction (fermion properties); 26D in another (for bosons).
(p8687) multiple closed strings represent tubes that merge & separate. This topology is key. Analogous to quantum fluctuations on fabric of spacetime.
Witten at el, showed compactification of superstrings, could curl up into tiny, complex, 6D structures not observable from 4D spacetime.
The structures for the compactification of heterotic strings fall into a broad class studied by ShingTung Yau and Eugenio Calabi. Yau tried to ferret out best fit from the CalabiYau spaces.
R. Feynman : "I have noticed, when I was younger, that lots of old men in the field couldn't understand new ideas very well, and resisted them w/ one method or another, and that they were very foolish (lacked imagination and were closeminded ) in saying these ideas were wrong...
Roger Penrose (qv p7275) worked in 60's on competing theory  twistor theory.
Maybe the very structure of spacetime is discrete?
A CONTINUING DEBATE
Feynman :"The only thing that's dangerous is that everybody does the same thing. We ought to be running around in as many directions as possible."
Problem w/ heterotic superstring is it is not experiemtnally testable. For Planck length 10^33cm need infeasible accelerator .
CHAPTER 3 ON THE MEANING OF NOW 
Can trace cosmos back to wi/ 10^43s of its inception. Before then infinite density. EM, Strong, Weak may have been fused.
Is time is a line or circle? expansions & contractions?
WHAT,THEN IS TIME?
St. Augustine tried to define time. Use earth,moon,sun?
arrived @ conclusion, God created time @ the beginning of creation
Time is a steady progression of events running from the past to the future.
Aristotle : but earth,moon,sun can be measured by time.
maybe it is cyclical? Augustine : no, goes against bible.
THE ART OF TELLING TIME
Sundials, Shadow clocks, Sumerians divided daylight into 12 periods.
Egyptians used stars so 24hr day. But varied.
Romans : dripping water clocks, hourglasses to mark off hourly intervals. But inconsistent.
11th cent AD : Chinese longrunning waterwheel w/ cups clock. No good on freezing day
13th cent AD : Europe used rope w/ weight in a balanced escapement that broke the fall of the weight into small steps revolving wheels. Needed someone to pull up weight.
14th cent AD : define minutes, seconds.
CONNECTING TIME AND SPACE
Relationship between time and space. Galileo Galilei quantified w/ help of pendulum.
measured rate at which objects fall. v=d/t. used waterclock, ball down incline. An object inc vel at 32fps every second,
Newton universal law of gravitation 1687. Ignored relativity. Time is always flowing forward
To analyze situations where speed/function changes over time, invented technique called calculus.
G.W. Leibniz 1684 also invented simultaneously. Debated who invented first.
Problems : supposedly universal laws of motion , is time an absolute as Newton claimed? problem is motion of light.
MEASURING THE SPEED OF LIGHT
1600 Galileo tried to measure w/ pair of lanterns.
1670 O. Romer noticed moon eclipses of Jupiter's moons varied by 22min / 6mo (earth nearest/farthest from Jupiter). This discrepancy lag = extra distance that light from the moons had to travel ~= diameter to Earth's orbit (known), so estimated 140,000 mps.
FINE TUNING
J. Bradley, stellar parallax. apparent shift in location of a star vs background of distant stars seen from Earth where position relative to star changes w/ planet's orbital movement around sun. 1725
But aberation due to slight deflection of starlight arriving from one direction at high veloc, viewed from planet orbiting in another direciton at a lower veloc.
qv A sail ship w/ vane angles toward faster of wind or ship. The telescope like vane tries to align w/ flow of light, but must account for orbital motion. 1830000mps.
1849 A. Fizeau. Lantern shines light through gaps in the rim of a spinning wheel to a mirror 5.16 miles away reflected back to observer. Increase spin rate until light doesn't return, but is blocked by teeth
J. Foucault replaced wheel w/ rotating mirror w/ facets. 186600mps.
A. Michelson 1931, refined to 186271mps
1980s Lasers, 186282.3974 mps National Bureau of Standards
A CRACK IN THE FOUNDATION
1887 Michaelson & E. Morely tried to detect ether. Invisible but universal medium in which EM waves & light propagate.
Like sound has a medium for transmission. Ether static, but like a runner feels breeze of parting air, ether should effect speed of light propagated at Earth's surface.
Used interferometer, split light beam at right angles then reflecting them back together. At the focal point, two waves would interfere to create bright and dark patterns/fringes, indicating how much one beam had been accelerated relative to the other. But found no aberation.
Discovered, frame of reference, had no effect on light's velocity.
H.A. Lorentz  Worked out transformation to relate time and distance in different frames of reference. 1904 principle of correlation, speed of light and EM radiation independent of frame of reference. i.e. Motion of the observer relative to the light source has no effect on the speed of light.
TRAVELLING FROM A LIGHT BEAM
Einstein : based on Lorentz and Michaelson  under no circumstances could speed of light be increased. But if light did not accelerate, then space must shrink, (lorentz contraction) or time must stretch out (time dilation).
as vel. approaches c, a timepiece runs slower , so a traveler time passes normally, but each hour would be years to a fixed frame.
1908 H. Minkowski Time is 4th dimension of space.
to represent static spatial event (eg earth's orbit), only need 3 dimensions, but to represent in time need a 4th line (time). A static occurence = world point, over time is a world line.
TIME AND GRAVITY
Einstein special theory of relativity  applied to bodies @ constant speeds. Looked at accelerated motion. Talked to man who fell from roof "I did not feel the tug of gravity on the way down"
During free fall no gravitational field, locally. Gravity only apparent when fall was decelerated. either by hitting ground or a parachute. Also one in floating weightlessly in space in a container only feels gravity in the container accelerates.
thus : principle of equivalence : forces of accleration and gravity are identical in effect.
An Accelerating one builds up a finite velocity affecting his clocks and rulers vs a stationary one. So by principle of equivalence : gravity field will have an effect on time passage. e.g. a clock near a star ticks slower than one far away (effect depends on size of star).
Thus 1915 General theory of relativity dealth w/ warping of spacetime by extremes of gravity and acceleration.
Twin goes in NAFAL ship, returns, twin is older. But if in gravity free environment, in which case twin under gravity's constant effect, could age more slowly! twin returns and is older!
TESTING THE THEORIES
1940 atomic clocks gauging precise frequencies Pound & Rebka, a source 74 higher, wi/ 1% of Einstein's figure.
1971 Flew 4 Csbeam atomic clocks around world.
VALIDATION
The W clock to gain is 273 nanoseconds. Eastward 59 ns loss.
Vessot & Levine used H2maser clock in rocket in suborbital flight. Frequency shift 1hz/1.42Ghz = 0.007% off from Einstein's predictions.
Used in timesensitive satellite navigation systems. Global positioning System.
Is universe closed or openended?
Hubble (Doppler)  analyzing spectra of starlight from distant galaxies : frequency of light is shifted , so universe is expanding. Thus the cosmos began in the past as an infinitely dense point wo/ dimension.
Would time eventually contact? thus reversing timedependent processes? Entropy would flow backwards, seems rather improbable.
ODDS AGAINST
S. Hawking : reverse entropy in terms of quantum theory  an observer cannot simultaneously measure the location and velocity of a particle, can't predict subsequent behavior of a particle. Can draw probabilities
A contracting universe would tend to be a very disordered state, not likely for a cup to reform perfectly.
Principle of uncertainty  undermines cause & effect, and the longstanding scientific belief that the laws of nature can be measured objectively , quantified precisely or deterministically.
Unnerving that on the very smallest scale ghostly fragments called virtual particles are popping into and out of existence. Wheeler dubs it the "quantum foam". Desireable to could look at this wo/ altering it beyond recognition.