Einstein and the big bang

Transcription

1 Einstein and the big bang A new perspective on Einstein s universe The Big Bang: Fact or Fiction? Cormac O Raifeartaigh FRAS (WIT)

2 Cosmology: the study of the universe How big is the universe? Is it finite or infinite? Did it have a beginning? Is it of finite age or eternal? How old is the universe? How will it end? What is the nature of time? What is the nature of space?

3 Newton s universe Orbits of the planets due to gravity Attractive force Gravity caused by mass of sun Infinite, eternal universe Newton ( ) Olber s paradox Seelinger s paradox

4 The discovery of the galaxies (1925) Edwin Hubble Starry nebulae at immense distance Far beyond Milky Way Hooker 100-inch reflector Many galaxies

5 Motion of galaxies: redshift frequency of light depends on motion of source relative to observer Doppler Effect Vesto Slipher measure motion of stars and galaxies from light emitted

6 The runaway galaxies Galaxies moving away (redshifts) Linear relation between motion and distance Hubble s Law (1929) Far-away galaxies rushing away at a speed proportional to distance v = H o d

7 Newton Explanation for runaway galaxies? Gravity pulls in not out Space is fixed Time has no beginning Isaac Newton How can galaxies be receding? What is pushing out?

8 Modern theory of gravity General theory of relativity (Einstein, 1915) space + time not fixed spacetime affected by motion affected by mass G μν = T μν gravity = curvature of space-time

9 Evidence for general relativity Bending of light by gravity (1919) Black holes Time stretching by gravity GPS

10 Apply relativity to the universe Predicts dynamic Universe Space expanding, contracting Alexander Friedman 3 possibilities (Friedman 1922, 24) Depends how much matter Rejected by Einstein Static universe (1917) G μν + λg μν = T μν

11 Lemaître s universe (1927) Redshifts of galaxies = expansion of space? Early data from Hubble Eternal, expanding universe Starts from Einstein universe at t = - Fr Georges Lemaître Not an empirical law Rejected by Einstein Votre physique est abominable Ditto for Friedman models

12 Hubble s law and relativity (1929) RAS meeting (1930) Eddington, de Sitter If redshifts are velocities and effect is non-local Hubble s law = expansion of space? Static models don t fit data Dynamic relativistic models required Friedman-Lemaître models Time-varying radius Density of matter decreases Evolving universe Cosmic expansion?

13 The expanding, evolving universe (1930 -) Eddington (1930, 31) On the instability of the Einstein universe Expansion caused by condensation? de Sitter (1930, 31) Further remarks on the expanding universe Expanding universes of every flavour Tolman (1930, 31) On the behaviour of non-static models Expansion caused by annihilation of matter? Einstein (1931, 32) Friedman-Einstein model λ = 0, k = 1 Einstein-deSitter model λ = 0, k =0 If redshifts represent expansion Evolving universe

14 An origin for the universe? Expanding U smaller in the past Rewind Hubble graph to origin Extremely dense, extremely hot Fr Georges Lemaitre Explosive beginning at R = 0? Later called the big bang

15 The big bang model (1931) U originally concentrated in tiny volume Extremely dense, hot Expanding and cooling since Wrong age (Hubble) Singularity problem density, temp at t = 0?

16 Steady-state universe (1950s) Alternative to big bang (Fred Hoyle) Expanding universe BUT Continuous creation of matter? Unchanging universe No beginning No age problem Very little matter needed

17 Radio-astronomy (1960s) Bitter debate between S-S and BB Study most distant galaxies Compare with local galaxies Density the same at all times? (S-S) Or different? (BB) Answer: different End of steady-state model

18 Bonus: cosmic background radiation CMB discovered accidentally Universal signal (1965) Low frequency (microwave) Low temperature (3K) Penzias and Wilson Echo of Big Bang!

19 Cosmology today Measurements by satellite Full spectrum of CMB Comparison with theory Ground telescopes Balloon experiments Satellite experiments COBE satellite (1992)

20 New! Einstein s steady-state model (WIT) Unpublished AE manuscript AE Archive (1931) Contains steady-state model of the cosmos Expanding universe of constant matter density Continuous formation of matter from vacuum Inconsistent theory Fatal flaw Abandoned Einstein in California (1931) Turns to evolving models Friedman-Einstein, Einstein-de Sitter

21 Einstein s steady-state model (1930s-) Hubble s law (1929) Expanding universe Age problem of evolving models Conflict with stellar ages Unchanging universe? Continuous creation of matter Associated with λ - energy of space Anticipates Hoyle et al. Doesn t work: no creation term Einstein declines to alter GR!

22 Einstein s steady-state model: key quotes New solution In what follows, I wish to draw attention to a solution to equation (1) that can account for Hubbel s facts, and in which the density is constant over time Matter creation If one considers a physically bounded volume, particles of matter will be continually leaving it. For the density to remain constant, new particles of matter must be continually formed within that volume from space Dark energy The conservation law is preserved in that, by setting the λ-term, space itself is not empty of energy; its validity is well known to be guaranteed by equations (1).

23 An abandoned model A fatal flaw De Sitter metric Matter creation associated with λ Null result masked by error Derivation incorrect Einstein s crossroads Identifed problem on revision Declined to amend GFE Evolving models? Less contrived and set λ = 0

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26 Significance of Einstein s steady-state model Unsuccessful theories important Understanding the development of successful theories New perspective on steady-state theory Logical possibility: not a crank theory Insight into Einstein s philosophy Discards model rather than add new term to GFE Occam s razor approach Insight into scientific progress Not Kuhnian paradigm shift Slow dawning Links with modern cosmology Dark energy: creation energy and λ Cosmic inflation: de Sitter metric

27 Einstein s steady-state model and cosmology today Dark energy (1998) Accelerated expansion (observation) Positive cosmological constant Einstein s dark energy The conservation law is preserved in that, by setting the λ-term, space itself is not empty of energy; its validity is well known to be guaranteed by equations (1). Cosmic inflation Inflationary models use de Sitter metric Used in all steady-state models Flat curvature, constant rate of matter creation Different time-frame!

28 The big bang model

29 COBE measurements of CMB Expected temperature Expected frequency Perfect blackbody spectrum Radiation very uniform Galaxy formation? Variation of 1 in 10 5 Nobel Prize 2006 COBE (1992)

30 Problems Background radiation raised new questions Horizon problem Galaxy problem Flatness problem why so uniform? how did galaxies form? fine balance? Singularity problem density, curvature at t = 0? Stephen Hawking quantum gravity?

31 Einstein s 1931 model (F-E) Instability of static universe Eddington s paper Hubble s observations Expanding cosmos Remove cosmic constant? Friedmann-Einstein universe Adopt Friedmann 1922 analysis Time-varying universe, k =1, λ = 0 Age and singularity problems Attributes to limitations of theory

32 Einstein s 1931 model (F-E) Numerical estimates of radius and density Use Hubble parameter P ~ 10 8 light-years, ρ ~ g/cm 3 Oxford lecture (May 1931) Calculations problematic H 0 ~500 kms -1 Mpc -1 : D 2 ~10-55 cm -2 Age estimate problematic Age from Friedmann Not a periodic solution Model fails at P = 0

33 Einstein-deSitter model (1932) Remove curvature Not known (Occam s razor) Adopt Friedmann analysis Time-varying universe with k =0, λ = 0 Critical universe Calculate critical density g/cm 3 : agrees with astrophysics Well-known model Despite age problem

34 Models: observational parameters needed Spatial curvature k = -1,0,1? Cosmic constant λ = 0? Deacceleration q 0 = - R /R 2 Density of matter ρ < ρ crit? Timespan τ = yr? Hubble constant R R = 500 kms -1 Mpc -1? What do redshifts represent? Is expansion a local effect? Hubble and Tolman 1935

35 The formation of galaxies Growth in static medium Natural fluctuations in density Exponential growth by gravitational collapse λ j =c s /(Gρ 0 /π) 1/2 Growth in expanding medium Lemaître 1934, Tolman 1935 Linear growth of density perturbations δρ/ρ R James Jeans Structure not from density fluctuations? New mechansim needed Eddington-Lemaître model?

36 An origin for the universe? Rewind Hubble graph U smaller in the past Extremely dense, extremely hot Primeval atom Expanding and cooling since The big bang Singularity problem density, temp at t = 0? Quantum theory Age problem U younger than stars?

37 Lemaître s hesitating universe ( ) Primeval atom Explosive expansion from radioactive decay Expansion slows down Positive cosmic constant Energy of vacuum; stagnation Indefinite timespan No age problem Formation of structure? Accelerated expansion de Sitter universe at large t Cosmic rays = radiation from early universe?

38 Finale: Paradigm shift or slow dawning? Hubble/Slipher Empirical law for nebulae Friedmann Time-varying solutions Lemaître Theory and observation Obs: Parsons, Huggins, Leavitt, Shapley Models I: Einstein, de Sitter, Weyl, Lanczos, Robertson Models II: Einstein, de Sitter, Eddington, Tolman, Robertson Slow emergence of theory and evidence Slow acceptance: no upsurge of interest

39 Act IV Slow acceptance: Hot big bang (1940s) Nucleosynthesis in the hot infant universe? Background radiation from early universe? Little interest from community No search for the cosmic radiation General relativity difficult, abstruse Gamow, Alpher and Hermann Steady-state universe (1948) Hoyle, Bondi and Gold Continuous creation of matter from vacuum No age or singularity problems Later ruled out by experiment (1960s) Radio-galaxy counts, CMB

40 Act V Cosmic background radiation Search for radio signals Large, sensitive receiver Universal signal (1965) From every direction Low frequency (microwave) Low temperature (3K) Penzias and Wilson Echo of big bang Radiation from early universe BB model goes mainstream

41 Cosmology today Satellite measurements of CMB No interference from atmosphere Expected temperature Expected frequency COBE satellite (1992) Full spectrum Perfect blackbody spectrum Perturbations Variation of 1 in 10 5

42 Planck Satellite (ESA): Results

43 Paradigm shift or slow dawning? Revolutionary v normal science Normal science interspersed by revolutions The paradigm shift Change of worldview occurs Social factors important Thomas Kuhn Incommensurability New worldview incommensurate with old Exp U: Slow exploration of theory and observation Slow acceptance of new paradigm ( )

44 Tolman s annihilation of matter Non-static line element (1930) Einstein, de Sitter models ruled out ds 2 = e 2kt dx dx dx 3 + c 2 dt 2 Cause of cosmic expansion? General evolutionary process Transformation of matter into radiation Rate of transformation From Hubble s law and from stellar physics δλ λ = kδl 1 dm M dt = 3k Influenced Einstein Steady-state model k = 5x10 10 yr -1

45 New results: Planck Satellite (ESA, 2013) 1. Improved sensitivity 1x10 6 T T 2. Full spectrum of T anisotropy New acoustic peaks :scale invariance? Accurate values for Ω Λ, Ω M 3. Gravitational lensing Remove degeneracies 4. Polarization measurements E-modes: fluctuations B-modes: gravity waves?

46 Planck results (2013) 1. New Hubble constant km/s/mpc Age = 13.8 billion yr No age conflict with astrophysics 2. Curvature: flat Ω k = Positive cosmic constant Ω Λ = 68% 4. New mass/energy parameters Ω DM = 27%, Ω OM = 4.9 %

47 Planck Results 1. Power spectrum Not scale invariant n s = Compatible with inflation Simple slow-roll models Higgs-type field? 3. Complex inflation out Double field out Hybrid models out Cyclic models out

48 The big bang model - questions Nature of dark energy? Role in BB? Nature of dark matter? Particle experiments? Which model of inflation? No-boundary universe The multiverse? The singularity problem What banged? What does time zero mean? The case is never closed