Known un­knowns be­yond the night sky

The Washington Post Sunday - - BOOK WORLD - Carl Zim­mer is the author of “The Tangled Bank: An In­tro­duc­tion to Evo­lu­tion.” book­world@wash­

THE 4 PER­CENT UNI­VERSE Dark Mat­ter, Dark En­ergy, and the Race to Dis­cover the Rest of Re­al­ity By Richard Panek Houghton Mif­flin Har­court. 297 pp. $26

In 1969, an as­tronomer named Jeremiah Ostriker re­al­ized that the Milky Way was spin­ning too fast. That may sound odd, given that it takes the sun 230 mil­lion years to make a full or­bit. But when Ostriker tried to sim­u­late the Milky Way on a com­puter, he found that it was spin­ning so quickly that it should have ripped it­self apart long ago. There weren’t enough stars to hold it to­gether.

Ostriker went to his fel­low Prince­ton sci­en­tist James Pee­bles to share his puz­zle. “ There’s some­thing wrong here,” Ostriker said to Pee­bles. The two sci­en­tists de­cided there could only be one so­lu­tion: The stars we can see in the Milky Way are just a small frac­tion of the ac­tual galaxy. They are embed­ded in a vast, un­seen halo, made of an un­known stuff that has come to be known as dark mat­ter. When Ostriker and Pee­bles looked to other gal­ax­ies, they found hints of dark mat­ter there as well.

Other as­tronomers didn’t want to be­lieve it. Af­ter all, they had spent the past four cen­turies learn­ing about the uni­verse by col­lect­ing its light in their tele­scopes. Now it seemed they were missing most of the cos­mic show. But as Richard Panek chron­i­cles in his fas­ci­nat­ing new book, “ The 4 Per­cent Uni­verse,” it turned out that there was a lot more wrong with the uni­verse than even Ostriker had re­al­ized and that his and Pee­bles’s work was only the be­gin­ning of an enor­mous un­der­tak­ing by many sci­en­tists.

The lat­est sur­veys of the uni­verse in­di­cate that only 4 per­cent of it is made of or­di­nary mat­ter. Nearly 23 per­cent is made of dark mat­ter, which some physi­cists sus­pect con­sists of wispy sub­atomic par­ti­cles that may some­day be caught in a de­tec­tor. And the re­main­ing 73 per­cent is made up of some­thing far more baf­fling: an en­ergy that is caus­ing the uni­verse to ex­pand at an ever-in­creas­ing rate. Sci­en­tists call it “dark en­ergy,” and they have no idea what it is. “Get rid of us and of ev­ery­thing else we’ve ever thought of as the uni­verse,” writes Panek, “and very lit­tle would change.”

In “ The 4 Per­cent Uni­verse,” Panek re­con­structs the five decades of re­search that led to this hum­bling re­al­iza­tion. It is one of the most im­por­tant sto­ries in the his­tory of sci­ence, but also one of the hard­est to tell. The sci­ence is fiendishly tricky, and the hu­man his­tory is also ar­cane. The dis­cov­er­ies of dark mat­ter and dark en­ergy were not the work of some lone ge­nius. It took a huge net­work of sci­en­tists. In 2007, Cam­bridge Uni­ver­sity awarded the Gru­ber Prize in Cos­mol­ogy, the high­est honor a cos­mol­o­gist can win, to the dis­cov­er­ers of dark en­ergy. Fifty-two win­ners showed up.

In­evitably, Panek has to plunge into the bureau­cratic depths of mod­ern sci­ence. His pages are splattered with acronyms — NSF, CARA, COBE, DASI — for fund­ing agen­cies and as­sorted as­tron­omy projects. From time to time, I had the same trou­ble keep­ing track of the sci­en­tists that I have with the char­ac­ters in big Rus­sian nov­els. Some chap­ters have only ten­u­ous links to the rest of the book, read­ing more like mag­a­zine ar­ti­cles than vi­tal episodes in a greater story.

But Panek’s pas­sion for the mys­ter­ies of dark mat­ter and dark en­ergy wins the day. He suc­ceeds be­cause he rec­og­nizes that he’s writ­ing not just about red shifts and su­per­novae, but about peo­ple. They’re un­usual peo­ple to say the least, happy to stay up all night to take pic­tures of stars or write soft­ware that com­pares those pic­tures to find the pop of su­per­novae ex­plod­ing in dis­tant gal­ax­ies. And they’re far from per­fect. The as­tronomer Vera Ru­bin gets to pay a visit to the le­gendary physi­cist Ge­orge Gamow to talk about the na­ture of the uni­verse, only to dis­cover he’s an oaf who yells at his wife. “Where were his pa­pers? What had she done with his pa­pers? Why was she al­ways go­ing through his pa­pers?” Panek writes. “Whether Gamow’s wife was ever ac­tu­ally there, Ru­bin couldn’t be sure.”

The suc­cess of “ The 4 Per­cent Uni­verse” also stems from Panek’s wis­dom about how sci­ence works. It’s easy to think that the dis­cov­ery of dark mat­ter and dark en­ergy — the re­al­iza­tion that we have no idea what most of the uni­verse is made of — is a story of fail­ure. Ac­tu­ally, sci­en­tists are de­lighted to have learned that they have blasted be­yond any ready ex­pla­na­tion that physics can of­fer for the uni­verse. Now they have the op­por­tu­nity to build a new physics that can make sense of how the uni­verse, both light and dark, re­ally works. “What greater legacy could a sci­en­tist leave a uni­verse?” Panek asks.


As­tronomers us­ing theHub­ble Space Te­le­scope dis­cov­ered this ghostly ring of dark mat­ter, which was formed dur­ing a col­li­sion be­tween two mas­sive galaxy clus­ters.

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