Universe in a box

Originally published 5 February 2006

Accord­ing to leg­end, Christ appeared to the medieval mys­tic Julian of Nor­wich and showed her a lit­tle thing the size of a hazel­nut that he placed in her hand. “What is it?” she asked. He answered, “It is all that is made.”

Cos­mol­o­gists are telling us some­thing sim­i­lar today. The entire observ­able uni­verse was once con­tained in a seed small­er than a hazel­nut, they say. Stars, galax­ies, plan­ets, you and me — the whole she­bang. An infi­nite­ly hot hazel­nut of pure ener­gy that explod­ed out­ward. The Big Bang.

The prob­lem with cos­mol­o­gy as a sci­ence is that cos­mol­o­gists have only one uni­verse to observe. Sci­ence works best when it can make com­par­isons, do exper­i­ments, twid­dle the vari­ables and see what hap­pens. Cos­mol­o­gists can observe the uni­verse and try to explain it, but as for a con­trolled exper­i­ment — well, for­get it.

Would­n’t it be love­ly if we had a way to go back to the begin­ning — to those first few tril­lion tril­lion tril­lionths of a sec­ond of the Big Bang — and change, say, the ratio of the strength of the grav­i­ta­tion­al force to the strength of the elec­tri­cal force. Or the ratio of the mass of the pro­ton to the mass of the elec­tron. And see what hap­pens. See if we still get a uni­verse where stars live long enough for life to evolve. Or a uni­verse where stars make enough heavy ele­ments — car­bon and oxy­gen, for exam­ple — to make life pos­si­ble. See just how spe­cial a uni­verse has to be for con­scious crea­tures to appear who look into the depths of space and won­der what it all means.

Well, maybe some­thing like this is pos­si­ble. Last year a paper appeared in the jour­nal Nature, titled “Sim­u­la­tions of the For­ma­tion, Evo­lu­tion and Clus­ter­ing of Galax­ies and Quasars,” that did not get near­ly the atten­tion it deserved in the pop­u­lar press. A con­sor­tium of Euro­pean cos­mol­o­gists ran the most detailed com­put­er sim­u­la­tion yet of the evo­lu­tion of the uni­verse, from the Big Bang to the present.

They pro­grammed into a super­com­put­er the laws of physics as best we under­stand them today. Start­ed with a seed of ener­gy and let the darn thing go. 500 quadrillion cal­cu­la­tions. And watched — watched as stars and galax­ies evolved on the screen of the com­put­er, form­ing them­selves into knots and stream­ers that look spec­tac­u­lar­ly like the uni­verse we see with our telescopes.

The uni­verse in a box!

Now you might think that what was accom­plished is a mere tau­tol­ogy: We derived the laws of physics by look­ing at the uni­verse in the first place, so it should not be sur­pris­ing that those same laws spin out a uni­verse like the one we live in. But remem­ber that the laws of physics employed in the sim­u­la­tion were derived here on Earth, in the lab­o­ra­to­ries of the Michael Fara­days and Marie Curies, and in the minds of the Albert Ein­steins and Stephen Hawk­ings. And now a com­put­er sim­u­la­tion shows that we are doing some­thing right.

With super­com­put­ers, we have a way to turn cos­mol­o­gy into an exper­i­men­tal sci­ence, of sorts. Play God, if you will.

Hun­dreds of bil­lions of galax­ies, stars in uncount­able num­bers, dark mat­ter, dark ener­gy, spilling out into the light-years and the eons on the screen of a com­put­er. Anoth­er great medieval mys­tic, John of the Cross, spoke of “the know­ing that unknows.” And I think there is some­thing of that here, too, in those flick­er­ing stream­ers of galax­ies in the super­com­put­er sim­u­la­tion: A kind of know­ing that makes us recon­sid­er every­thing that we thought we knew — about our­selves, about the ori­gin and des­tiny of the uni­verse, about God. A kind of know­ing so spec­tac­u­lar in breadth and scope that it stretch­es our understanding.

Our chal­lenge is to let our­selves be stretched.