Guided tour leaves us a lot less lost in space

The Weekend Australian - Review - - Books -

In Can­dide, Voltaire satirises Got­tfried Wil­helm Leib­niz’s dic­tum that we live in the best of all pos­si­ble worlds. The naive Dr Pan­gloss clings to this as an es­sen­tial truth, de­spite en­dur­ing a chain of ter­ri­ble mishaps. By the end of Can­dide, it is hard to agree with the good doc­tor.

Aus­tralian as­tro­physi­cists Geraint Lewis and Luke Barnes open their charm­ing, in­tel­li­gent and well-writ­ten book by ar­gu­ing that we live in “a for­tu­nate uni­verse”. The Earth “is a spe­cial place” for hu­mans, “a rel­a­tive cos­mic par­adise where the con­di­tions are just right for life”.

Not only that, but “at ev­ery level, we find that our uni­verse’s abil­ity to cre­ate and sus­tain life forms is rare and re­mark­able”. The Univer­sity of Syd­ney duo then pro­ceed to con­vinc­ingly show why we should share their be­lief.

This re­quires a gen­tle stroll through the de­tails of the stan­dard model of par­ti­cle physics, as well as the stan­dard model of cos­mol­ogy, but the au­thors lead us with such a light hand, streak of hu­mour and lack of pedantry that the in­for­ma­tion is eas­ily ab­sorbed.

Atomic nu­clei are made up of neu­trons and pro­tons, and these in turn are com­posed of quarks. But what de­ter­mines the mass of the quarks and elec­trons that sur­round the nu­clei? Or, for that mat­ter, what sets the strength of the forces that hold the quarks to­gether or of those that bind the elec­trons to the nu­clei? De­spite decades of valiant re­search, we still don’t know.

A more tech­ni­cal state­ment of our puz­zle­ment is that the stan­dard model of par­ti­cle physics has 19 so-called free pa­ram­e­ters, num­bers whose val­ues have been de­ter­mined ex­per­i­men­tally but have evaded ex­pla­na­tion.

But those pa­ram­e­ters are not free in the sense that the world would be rel­a­tively un­changed if they had slightly dif­fer­ent val­ues. Here’s where the sub­ti­tle Life in a Finely Tuned Cos­mos en­ters the pic­ture.

Lewis and Barnes show us how small changes lead to a va­ri­ety of dis­as­ters. (“Ru­in­ing a uni­verse is easy,” Barnes quips.) Neu­trons and pro­tons are pri­mar­ily com­posed of up and down quarks. A lit­tle shift in the masses of those quarks causes pro­tons to de­cay into neu­trons rather than vice versa. In an­other ver­sion, the shifts pro­duce a uni­verse where hy­dro­gen and he­lium are the only el­e­ments present.

Af­ter an in­tro­duc­tion to the concept of fine­tun­ing in par­ti­cle physics, Lewis and Barnes turn to cos­mol­ogy and come face-to-face with the great dilem­mas posed in un­der­stand­ing how our uni­verse has come about and what its fu­ture is likely to be. The es­tab­lish­ment of the stan­dard model of cos­mol­ogy is re­garded as one of the great tri­umphs of mod­ern sci­ence.

Ac­cord­ing to the model, the uni­verse be­gan with a big bang a lit­tle less than 14 bil­lion years ago and has been ex­pand­ing since then. Atoms formed about 400,000 years af­ter the big bang, and, as ex­pan­sion and cool­ing con­tin­ued, stars, gal­ax­ies and plan­ets formed.

Is this all a happy co­in­ci­dence, as the au­thors ask each other in an amus­ing mock de­bate mod­elled on one that Galileo in­sti­gated 400

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