If there are oth­er un­iverses out there—as some sci­en­tists pro­pose—then one or more of them might be de­tect­a­ble, a new study sug­gests.

Such a find­ing, “while cur­rently spec­u­la­tive even in prin­ci­ple, and probably far-off in prac­tice, would surely con­sti­tute an ep­och­al dis­cov­ery,” re­search­ers wrote in a pa­per de­tail­ing their stu­dy. The work ap­pears in the Sep­tem­ber is­sue of the re­search jour­nal Phys­i­cal Re­view D.

Cos­mol­o­gists gen­er­ally hold that even if oth­er un­iverses ex­ist, a con­tro­ver­sial idea it­self, they would­n’t be vis­i­ble, and that test­ing for their ex­istence would be hard at best.

A half-sky map of slight tem­per­a­ture vari­a­tions in the cos­mic mi­cro­wave back­ground ra­di­a­tion, thought to map struc­tures in the very ear­ly uni­verse. Blue stands for colder ar­eas; red for hot­ter re­gions, where it’s be­lieved mat­ter was dens­er. These dense re­gions are thought to have lat­er be­come ga­laxy-rich zones. The boxed ar­ea marks an un­u­su­al “cold spot” re­search­ers rec­og­nize in the da­ta. An un­ex­plained gi­ant cos­mic void has also been found in the di­rec­tion of that spot. In a new stu­dy, the­o­ret­i­cal phys­i­cists ar­gue that some sort of ir­reg­u­lar­ity in the mi­cro­wave back­ground, and in mat­ter dis­tri­bu­tion, might in­di­cate where our uni­verse once knocked in­to an­oth­er one. But the re­search­ers take no po­si­tion on wheth­er this cold spot could be the anom­a­ly they’re look­ing for. Much more work is needed, they say.

But the new stu­dy, by three sci­en­tists at the Un­ivers­ity of Cal­i­for­nia, San­ta Cruz, pro­poses that neigh­bor­ing un­iverses might leave a vis­i­ble mark on our own—if, per­chance, they have knocked in­to it. For such a scar to be de­tect­a­ble, they add, the col­li­sion might have had to take place when our un­iverse was very young. Just how the bruise might look re­mains to be clar­i­fied, they say.

Full Story: World of Science.

(Thanks James!)