Georges Lemaître:

An overview of his

contributions to physics and

cosmology

VaticanObservatoryConference,2017H. Kragh,NielsBohrInstitute,UniversityofCopenhagen

Georges Édouard Lemaîtrephysicist and priest, pioneer of big-bang cosmology

Lundmark’s data of 1924

Do the redshifts of the spiral nebulae vary systematically with their distances?

krz =D

=ll

?

The incredible

shrinking constant

Lemaître 1927 H0 ≅ 625 km/s/Mpc

Hubble 1931 H0 ≅ 558 km/s/Mpc

Planck 2015 H0 = 67.8 km/s/Mpc

L-Emodel

Lemaître-Eddington model (1927; 1930)

The universe (which has always existed) starts in an Einstein state and approaches a de Sitter state.

L-model

Lemaître’s “primeval atom” universe of 1931

Finite-spaceandfinite-agemodel.Keepscosmologicalconstant (Λ >0),whichsecuresa“stagnationphase”andsolvesthetime-scaledifficulty.

Letter to Nature, May 9, 1931

The world started in a radioactive explosion of a “primordial atom” of density as an atomic nucleus.

Typeddraft,withdeletedreferencetoGod.

ArchiveLemaître,Louvaindelaneuve.

Einstein, “Zum kosmologischen Problem der allgemeine Relativitätstheorie,” Sitzungsber. Preuss. Akad. Wiss. 1931: 235-237.

A. Einstein & W. de Sitter, ”On the relation between the expansion and the mean density of the universe,” Proc. Nat. Acad. Sci. 18 (1932), 213-314.

Big bang models without a big bang…

”According to Lemaître’s theory, all the matter in the universe was once packed within a single, gigantic atom, which … burst, its fragments forming the stars of which our

universe is built. …”

Lemaître’s big bang as described in Popular Science Monthly 1932.

G. Lemaître & M.S. Vallarta, ”On Compton’s latitude effect of cosmic radiation,” Phys. Rev. 43 (1933), 87-91.

Thestudyofcosmicrays”givessomeexperimentalsupporttothetheoryofsuper-radioactiveoriginofthecosmicradiation.”

”Thelasttwothousandmillionyearsareslowevolution…ashesandsmokeofbrightbutveryrapidfireworks.”

Computational cosmology?IntheircalculationsofenergiesandtrajectoriesofchargedparticlesintheEarth’smagneticfield,seenasatestoftheprimeval-atomhypothesis,LemaîtreandVallartamadeuseofMIT’sdifferential-analyzercomputerdevelopedbyVannevarBush.

”I do not think that many cosmogonists have yet been persuaded by the theory of Lemaître. It is usually regarded as a brilliantly clever jeu d’espritrather than a sober reconstruction of the beginning of the world.”

E. W. Barnes, Scientific Theory and Religion (Cambridge, 1933).

”Lemaître’s hypothesis is the wildest speculation of all … an example of speculation run mad without a shred of evidence to support it.”

J. H. Plaskett, ”The expansion of the universe,” J. Roy. Soc. Canada 27 (1933), 235-252.

”We must be careful to keep our judgements uninfected by the demands of theology and unswerved by human hopes and fears.”

”The discovery of models, which start expansion from a singular state of zero volume, must not be confused with a proof that the actual universe was created at a finite time in the past.”

Tolman warns against

”the evils of autistic and

wishfulfilling thinking” in

cosmology

Lemaître and the cosmological constant (I)

G.Lemaître,”Evolutionoftheexpandinguniverse,”Proc.Nat.Acad.Sci.20 (1934),12-17.

Lemaître and the cosmological constant (II)

”SinceIhaveintroducedthistermIhadalwaysabadconscience.…Ifounditveryuglyindeed…andamunabletobelievethatsuchanuglythingshouldberealizedinnature.”

EinsteintoLemaître,26Sep1947

”Thetheoryremainsopentonewdevelopmentswhichmayconnectthetheoreticallyunknownvalueofthecosmicalconstantwithotherconstantsofphysics.”

Itisa”logicalconvenience”andwasfoundby”ahappyaccident.”

LemaîtretoEinstein,3Oct1947

11th Solvay Congress 1958

Theconference,devotedtoastrophysicsandcosmology,hadstrongparticipationofsteady-statetheorists(Hoyle,Bondi,Gold,McCrea).Lemaîtrewasaloneinadvocatingmodelsofthe

big-bangkind.

Lemaître and the Nobel Prize

As the first theoretical cosmologist ever,

Lemaître was nominated for the Nobel Prize in

physics, in 1954 for his prediction of the

expanding universe.

But until the mid-1970s, the Nobel

Committee did not admit astrophysics and

cosmology as proper physics.

Remarkably, he was also nominated for

the 1956 Nobel prize, this time for his

primeval-atom theory, but in chemistry!

Nature139 (1937)