"Long before it's in the papers"
January 27, 2015


“Inflation” theory of infant cosmos may need revision

July 26, 2013
Courtesy of the Kavli Foundation
and World Science staff

The most de­tailed map of the early uni­verse ev­er de­vised by peo­ple—re­leased this spring—is re­new­ing ques­tions among many phys­i­cists about what hap­pened in that dis­tant past.

At is­sue is the pre­vail­ing “infla­t­ion” mod­el of the uni­verse, which holds that the uni­verse briefly un­der­went an in­cred­i­ble burst of ex­pan­sion just af­ter the Big Bang, the ex­plos­ion-like event be­lieved to have started it all.

The new map, gen­er­at­ed by ob­serva­t­ions from the Eu­ro­pe­an Space Agen­cy’s Planck space­craft, re­vealed fluctua­t­ions in tem­per­a­ture of radia­t­ion left over from the Big Bang. This radia­t­ion, de­tect­a­ble across the whole sky, is known as the Cos­mic Mi­cro­wave Back­ground.

Planck mis­sion sci­en­tists have been puz­zled by some hard-to-explain fea­tures in this back­ground light, in­clud­ing a large cold spot. This spot points to a huge ar­ea of high dens­ity, or com­pact­ness of ma­te­ri­al.

The spot is too large to neatly fit the infla­t­ion mod­el, some sci­en­tists say. The Kavli Founda­t­ion, based in Ox­nard, Calif., this week re­leased a tran­script of a roundtable that it had held with three key mem­bers on the team. One im­por­tant ques­tion: Will the the­o­ry for how the uni­verse be­gan need to be mod­i­fied, amended or even fun­da­men­tally changed?

“Per­haps our the­o­ry of infla­t­ion is not cor­rect, de­spite its beau­ty and sim­pli­city,” said George Ef­s­tathiou, an as­t­ro­phys­i­cist at the Uni­vers­ity of Cam­bridge and di­rec­tor of the Kavli In­sti­tute for Cos­mol­o­gy at Cam­bridge.

Amer­ican phys­i­cist Alan Guth is cred­ited with first pro­posing the in­fla­tion mod­el, in 1980.

The the­o­ry “pre­dicts that to­day’s uni­verse should ap­pear un­iform at the larg­est scales in all di­rec­tions,” he ex­plained. “That un­iform­ity should al­so char­ac­ter­ize the dis­tri­bu­tion of fluctua­t­ions at the larg­est scales,” he added. “But these anoma­lies, which Planck con­firmed, such as the cold spot, sug­gest that this is­n’t the case.”

“This is very strange,” added Ef­s­tathiou, who has been in­volved in the Planck mis­sion since it was pro­posed in 1993. “And I think that if there really is an­y­thing to this, you have to ques­tion how that fits in with infla­t­ion.... It’s really puz­zling.”

“Infla­t­ion ac­tu­ally may have been more lim­it­ed in scope than pre­vi­ously the­o­rized,” said An­tho­ny Lasenby, an as­t­ro­phys­icist at Cam­bridge and dep­u­ty di­rec­tor of the insti­tute.

Some phys­i­cists have pro­posed that fea­tures such as the cold spot may al­so signify that oth­er uni­verses bumped in­to our own.

Krzysztof Gorski, a Planck Col­la­bora­t­ion sci­ent­ist and sen­ior re­search sci­ent­ist at the Jet Pro­pul­sion Lab­o­r­a­to­ry in Pas­a­de­na, Calif., told the roundtable that “per­haps we may still elim­i­nate these anoma­lies with more pre­cise anal­y­sis; on the oth­er hand, they may open the door to some­thing much more grand—a re­in­ves­ti­ga­t­ion of how the whole struc­ture of the uni­verse should be.”

The sci­en­tists al­so plan to an­swer ques­tions from the pub­lic dur­ing a live “Google Hang­out” July 31 at noon Pa­cif­ic time.

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The most detailed map of the early universe ever devised by people—released this spring—is renewing questions among many physicists about what happened in that distant past. At issue is the prevailing “inflation” model of the universe, which holds that the universe briefly underwent an incredible burst of expansion just after the Big Bang, an explosion-like event believed to have given birth to the cosmos. The new map, generated by observations from the European Space Agency’s Planck spacecraft, revealed fluctuations in temperature of radiation left over from the Big Bang. This radiation, detectable across the whole sky, is known as the Cosmic Microwave Background. Planck mission scientists have been puzzled by some hard-to-explain features in this background light, including a large cold spot. This spot points to a huge area of high density, or compactness of material. The spot is too large to neatly fit the inflation model, some scientists say. The Kavli Foundation, based in Oxnard, Calif., this week released a transcript of a roundtable that it had held with three key members on the team. One important question: Will the theory for how the universe began need to be modified, amended or even fundamentally changed? “Perhaps our theory of inflation is not correct, despite its beauty and simplicity,” said George Efstathiou, an astrophysicist at the University of Cambridge and director of the Kavli Institute for Cosmology at Cambridge The theory “predicts that today’s universe should appear uniform at the largest scales in all directions,” he explained. “That uniformity should also characterize the distribution of fluctuations at the largest scales,” he added. “But these anomalies, which Planck confirmed, such as the cold spot, suggest that this isn’t the case.” “This is very strange,” added Efstathiou, who has been involved in the Planck mission since it was proposed in 1993. “And I think that if there really is anything to this, you have to question how that fits in with inflation.... It’s really puzzling.” “Inflation actually may have been more limited in scope than previously theorized,” said Anthony Lasenby, a member of the Planck Core Team and professor of astrophysics and cosmology at Cambridge and Deputy Director of KICC. Some physicists have proposed that features such as the cold spot may also be indications that other universes bumped into our own. Krzysztof Gorski, a Planck Collaboration scientist and senior research scientist at the Jet Propulsion Laboratory in Pasadena, Calif., told the roundtable that “perhaps we may still eliminate these anomalies with more precise analysis; on the other hand, they may open the door to something much more grand—a reinvestigation of how the whole structure of the universe should be.” The scientists also plan to answer questions from the public during a live “Google Hangout” July 31 at noon Pacific time.