"Long before it's in the papers"
July 11, 2011

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Is the universe spinning?

July 11, 2011
Courtesy of the University of Michigan
and World Science staff

New find­ings sug­gest the uni­verse was born spin­ning, which means it may still be, phys­i­cists say.

Sci­en­tists have long as­sumed space is bas­ic­ally the same in eve­ry di­rec­tion, but new find­ings chal­lenge that claim. The most plau­si­ble ex­plana­t­ion for the lack of sym­me­try is a spin in the whole cos­mos, which would tend to make mat­ter act dif­fer­ently de­pend­ing on the di­rec­tion you look, re­search­ers say.

Phys­i­cist Mi­chael Longo at the Uni­vers­ity of Mich­i­gan Ann Ar­bor and five stu­dents cat­a­logued the di­rec­tion in which tens of thou­sands of spir­al ga­lax­ies, pho­tographed pre­vi­ously in in a proj­ect known as the Sloan Dig­it­al Sky Sur­vey, are spin­ning.

The mir­ror im­age of a counter-clock­wise-spin­ning gal­axy would have clock­wise spin. More of one type than the oth­er would be ev­i­dence for a break­down of sym­me­try, al­so called a “par­ity vi­ola­t­ion” on cos­mic scales, Longo said. The group found an ex­cess of left-hand­ed, or counter-clock­wise ro­tat­ing, spir­als in the part of the sky to­ward the north pole of the Milky Way. The ef­fect ex­tend­ed be­yond 600 mil­lion light-years away, a light-year be­ing the length of space that light crosses in a year.

“The ex­cess is small, about 7 per­cent, but the chance that it could be a cos­mic ac­ci­dent is some­thing like one in a mil­lion,” Longo said. “These re­sults are ex­tremely im­por­tant be­cause they ap­pear to con­tra­dict the al­most un­iver­sally ac­cept­ed no­tion that on suf­fi­ciently large scales the uni­verse is iso­trop­ic, with no spe­cial di­rec­tion.”

If the uni­verse was born ro­tat­ing, like a spin­ning bas­ket­ball, Longo said, there would be one “spe­cial” di­rec­tion, that be­ing the ax­is of rota­t­ion. Ga­lax­ies would have re­tained traces of that in­i­tial mo­tion, he added. Is the uni­verse still spin­ning? “It could be,” Longo said. “I think this re­sult sug­gests that it is.” 

Be­cause the tel­e­scope used in the Sloan sur­vey is in New Mex­i­co, the da­ta the re­search­ers an­a­lyzed came mostly from the north­ern hem­i­sphere of the sky. An im­por­tant test of the find­ings will be to see if there is an ex­cess of right-hand­ed spir­al ga­lax­ies in the south­ern hem­i­sphere, the group said. That study is un­der way, but the cur­rent find­ings mean­while are pub­lished in the re­search jour­nal Phys­ics Let­ters B.

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New findings suggest the universe was born spinning, which means it may still be, physicists say. Scientists have long assumed space is basically the same in every direction, but new findings challenge that claim. The most plausible explanation for the lack of symmetry is a spin in the whole cosmos, which would tend to make matter act differently depending on the direction you look, researchers say. Physicist Michael Longo at the University of Michigan Ann Arbor and five students catalogued the direction in which tens of thousands of spiral galaxies, photographed previously in in a project known as the Sloan Digital Sky Survey, are spinning. The mirror image of a counter-clockwise-spinning galaxy would have clockwise spin. More of one type than the other would be evidence for a breakdown of symmetry, also called a “parity violation” on cosmic scales, Longo said. The group found an excess of left-handed, or counter-clockwise rotating, spirals in the part of the sky toward the north pole of the Milky Way. The effect extended beyond 600 million light-years away, a light-year being the length of space that light crosses in a year. “The excess is small, about 7 percent, but the chance that it could be a cosmic accident is something like one in a million,” Longo said. “These results are extremely important because they appear to contradict the almost universally accepted notion that on sufficiently large scales the universe is isotropic, with no special direction.” If the universe was born rotating, like a spinning basketball, Longo said, there would be one “special” direction, that being the axis of rotation. Galaxies would have retained traces of that initial motion, he added. Is the universe still spinning? “It could be,” Longo said. “I think this result suggests that it is.” Because the telescope used in the Sloan survey is in New Mexico, the data the researchers analyzed came mostly from the northern hemisphere of the sky. An important test of the findings will be to see if there is an excess of right-handed spiral galaxies in the southern hemisphere, the group said. That study is under way, but the current findings meanwhile are published in the research journal Physics Letters B.