If there are oth?er un?iverses out there-as some sci?en?tists pro?pose-then one or more of them might be de?tect?a?ble, a new study sug?gests.
Such a find?ing, ‘while cur?rently spec?u?la?tive even in prin?ci?ple, and probably far-off in prac?tice, would surely con?sti?tute an ep?och?al dis?cov?ery,’ re?search?ers wrote in a pa?per de?tail?ing their stu?dy. The work ap?pears in the Sep?tem?ber is?sue of the re?search jour?nal Phys?i?cal Re?view D.
Cos?mol?o?gists gen?er?ally hold that even if oth?er un?iverses ex?ist, a con?tro?ver?sial idea it?self, they would?n’t be vis?i?ble, and that test?ing for their ex?istence would be hard at best.
A half-sky map of slight tem?per?a?ture vari?a?tions in the cos?mic mi?cro?wave back?ground ra?di?a?tion, thought to map struc?tures in the very ear?ly uni?verse. Blue stands for colder ar?eas; red for hot?ter re?gions, where it’s be?lieved mat?ter was dens?er. These dense re?gions are thought to have lat?er be?come ga?laxy-rich zones. The boxed ar?ea marks an un?u?su?al “cold spot” re?search?ers rec?og?nize in the da?ta. An un?ex?plained gi?ant cos?mic void has also been found in the di?rec?tion of that spot. In a new stu?dy, the?o?ret?i?cal phys?i?cists ar?gue that some sort of ir?reg?u?lar?ity in the mi?cro?wave back?ground, and in mat?ter dis?tri?bu?tion, might in?di?cate where our uni?verse once knocked in?to an?oth?er one. But the re?search?ers take no po?si?tion on wheth?er this cold spot could be the anom?a?ly they’re look?ing for. Much more work is needed, they say.
But the new stu?dy, by three sci?en?tists at the Un?ivers?ity of Cal?i?for?nia, San?ta Cruz, pro?poses that neigh?bor?ing un?iverses might leave a vis?i?ble mark on our own-if, per?chance, they have knocked in?to it. For such a scar to be de?tect?a?ble, they add, the col?li?sion might have had to take place when our un?iverse was very young. Just how the bruise might look re?mains to be clar?i?fied, they say.