Right af­ter the Big Bang, the young uni­verse filled up with knots, pro­duc­ing the di­men­sions we live in, ac­cord­ing to a new ex­pla­na­tion of why the uni­verse has 3 di­men­sions. The the­ory changes the story of how the uni­verse formed.

Science Illustrated - - CONTENTS -

Why are there only three phys­i­cal di­men­sions? The an­swer may have some­thing to do with space­time knots in the early uni­verse. No re­ally.

Nick and Gabby want to meet in a restau­rant in Man­hat­tan, New York City. Nick ex­plains that the restau­rant is on the cor­ner of 58th Street and 12th Av­enue on the eighth floor. So, he has de­scribed their meet­ing place us­ing three num­bers – 58, 12, and 8 – but he might as well have used the de­grees of lat­i­tude and lon­gi­tude plus height. The lo­ca­tion of all points in space can be de­ter­mined by means of those three num­bers – the world is 3D.

The three spa­tial di­men­sions of the uni­verse are so ob­vi­ous to us that sci­en­tists have rarely tried to find out why it is or­ga­nized in this way, but physi­cists have de­vel­oped a new the­ory that ex­plains it: the uni­verse has three di­men­sions, as it is based on an ex­plod­ing net­work of en­tan­gled knots.

The uni­verse loses di­men­sions

To­day, physi­cists’ un­der­stand­ing of the Big Bang is based on the su­per­string the­ory, ac­cord­ing to which all mass and en­ergy in the uni­verse right af­ter the Big Bang con­sisted of tiny, vi­brat­ing su­per­strings, which ex­isted in 10 spa­tial di­men­sions. Sub­se­quently, the uni­verse ex­pe­ri­enced an ul­tra­fast ex­pan­sion known as in­fla­tion, dur­ing which the young uni­verse grew from the size of an elec­tron to the vol­ume of a foot­ball in a split sec­ond. When the in­fla­tion was over, the uni­verse only had three ma­jor, spa­tial di­men­sions.

The pass­ing from 10 to 3D dur­ing the ex­pan­sion is con­sis­tent with physi­cists’ Big Bang model, but the model does not in­clude any trig­ger­ing fac­tor, nor does it ex­plain how it hap­pened. In 2012, five physi­cists from Europe and the US be­gan to pon­der the ques­tion, and now they have come up with an an­swer.

The physi­cists’ new the­ory is based on tra­di­tional the­o­ries about the Big Bang com­bined with the knot the­ory, ac­cord­ing to which math­e­mat­i­cal knots can only ex­ist in 3D. The sci­en­tists were in­spired by the pri­mor­dial soup of the uni­verse, which formed af­ter the in­fla­tion and ex­isted one mi­crosec­ond af­ter the Big Bang. The pri­mor­dial soup con­sisted of equal quan­ti­ties of quarks and an­ti­quarks, which flowed about a soup of force par­ti­cles known as glu­ons. In the present ex­panded and cooled uni­verse, glu­ons bind quarks into pro­tons and neu­trons, and so hold atomic cores to­gether. But in the pri­mor­dial soup, all mat­ter was bil­lions of de­grees hot, and in the ex­treme heat, the build­ing blocks could not form, so the quarks were free. In­stead, brief gluon bind­ings formed be­tween quarks and an­ti­quarks. When mat­ter and an­ti­mat­ter en­coun­tered, the par­ti­cles de­stroyed each other and were con­verted into ra­di­a­tion. Dur­ing the de­struc­tion, quark and an­ti­quark moved away from each other, so the gluon "rub­ber band" be­tween them was stretched to its burst­ing point, burst, and was con­verted into ra­di­a­tion. The de­struc­tion re­leased suf­fi­cient en­ergy to pro­duce a new pair of one quark and one an­ti­quark linked by a gluon rub­ber band. The process was re­peated with myr­i­ads of mesons.

Knots or­gan­ised the world

In the new the­ory, it was not suf­fi­cient that a pri­mor­dial soup de­vel­oped af­ter the in­fla­tion, so the the­ory in­cludes a sim­i­lar sub­stance, in which de­struc­tion of quarks and an­ti­quarks hap­pened be­fore the in­fla­tion, when the uni­verse was smaller and much warmer than in the pri­mor­dial soup. The physi­cists thought that if the myr­i­ads of burst gluon rub­ber bands had time to en­tan­gle into knots, be­fore they were con­verted into ra­di­a­tion, the rub­ber bands would be sta­bi­lized and briefly sur­vive the de­struc­tion of the par­ti­cles.

Ac­cord­ing to the physi­cists' cal­cu­la­tions, the burst rub­ber bands en­tan­gled into a com­plex, com­mon net­work of knots. The en­tan­gle­ment hap­pened al­most au­to­mat­i­cally, as bil­lions of gluon rub­ber bands ex­isted in the young uni­verse, which was the size of an elec­tron.

If the uni­verse right af­ter the Big Bang pri­mar­ily con­sisted of a net­work of gluon rub­ber bands, the struc­ture would con­tain huge quan­ti­ties of en­ergy. The net­work would only be able to re­main sta­ble for a split sec­ond, be­fore col­laps­ing in an ex­plo-sion that re­leased all the en­ergy of the net­work. The ex­plo­sion pow­ered the uni­verse’s ex­treme ex­pan­sion dur­ing the in­fla­tion, and be­cause the knot net­work was 3D in it­self, it in­flated a 3D space.

Knots could be dark en­ergy

The five physi­cists aim to find out ex­actly how the re­pul­sive en­ergy trig­gered by the knot net­work in the ex­plo­sion func­tioned as an op­po­nent of grav­ity, en­abling the uni-verse to ex­pand. Both tra­di­tional the­o­ries and the new the­ory pre­dict that the type of re­pul­sive en­ergy that pow­ered the in­fla­tion is the same that has made the uni­verse’s ex­pan­sion ac­cel­er­ate for the past six bil­lion years – i.e. dark en­ergy. So, the sci­en­tists aim to find out if the knot net­work could also be the driv­ing force be­hind dark en­ergy.

In 2015, sci­en­tists man­aged to de­tect the first grav­i­ta­tional waves in space. Grav­i­ta­tional waves are emit­ted, when large masses are ac­cel­er­ated fast through space, which hap­pened dur­ing the in­fla­tion, when the en­tire uni­verse ex­panded at a speed faster than that of light. In a few decades, sci­en­tists’ equip­ment may be able to de­tect grav­i­ta­tional waves from the in­fla­tion of the uni­verse. If so, the marks left by the waves might re­veal where the ex­pand­ing force came from. And then we would know if the en­tan­gled knot net­work of the new the­ory is the rea­son why Gabby and Nick only need three num­bers to find each other. Well, there is a fourth num­ber of course: the time they hope to meet. But that's a whole other story...

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