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


Ripples in space-time detected, astronomers say

March 17, 2014
Courtesy of the Harvard-Smithsonian 
Center for Astrophysics
and World Science staff

As­tro­no­mers say they have de­tected “rip­ples” in space and time caused by a pro­cess in which our uni­verse ex­pand­ed out of con­trol dur­ing its first fleet­ing frac­tion of a sec­ond.

The pro­cess is said to have be­gun al­most 14 bil­lion years ago dur­ing the Big Bang, an ex­plo­sive event that gave birth to the uni­verse. In an un­imag­inably small amount of time, the the­o­ry goes, the uni­verse stretched to be far big­ger than what our best tele­scopes would be able to see.

The B-mode or "twisty" pat­tern seen in the cos­mic back­ground light. The lines show the po­lar­i­za­tion strength and ori­en­ta­tion at dif­fer­ent spots on the sky. The red and blue shad­ing shows the de­gree of clock­wise and anti-clock­wise twist­ing of this B-mode pat­tern. (Cour­te­sy BI­CEP2 Col­lab­o­ra­tion)

This ver­sion of the Big Bang the­o­ry is known as “infla­t­ion.”

Sci­en­tists from a re­search col­la­bora­t­ion called BI­CEP2 an­nounced on Mon­day what they called the first di­rect ev­i­dence for this cos­mic infla­t­ion. Their da­ta al­so rep­re­sent the first im­ages of gravita­t­ional waves, or rip­ples in space-time. These waves have been de­scribed as the “first tremors of the Big Bang.” 

Fi­nal­ly, they said, the da­ta con­firm a deep con­nec­tion be­tween quan­tum me­chan­ics, the pre­vail­ing the­o­ry that de­scribes the realm of sub­a­tom­ic par­t­i­cles, and gen­er­al rel­a­ti­vity, which de­scribes events on cos­mic scales.

“De­tect­ing this sig­nal is one of the most im­por­tant goals in cos­mol­o­gy to­day. A lot of work by a lot of peo­ple has led up to this point,” said John Ko­vac of the Har­vard-Smith­son­ian Cen­ter for As­t­ro­phys­ics, lead­er of the BI­CEP2 col­la­bora­t­ion.

The find­ings came from ob­serva­t­ions by the BI­CEP2 tel­e­scope of the cos­mic mi­cro­wave back­ground—a faint glow left over from the Big Bang. Ti­ny fluctua­t­ions in this af­ter­glow pro­vide clues to con­di­tions in the early uni­verse. For ex­am­ple, small dif­fer­ences in tem­per­a­ture across the sky show where parts of the uni­verse had thick­er con­sist­ency, ma­ter­ial that would later con­dense in­to ga­lax­ies.

The cos­mic mi­cro­wave back­ground is a form of light, and light can be “po­lar­ized,” mean­ing many waves vi­brate in si­m­i­lar di­rections. This can oc­cur af­ter light scat­ters off atoms or oth­er par­t­i­cles; on Earth, sun­light be­comes po­lar­ized af­ter hit­ting the at­mos­phere.

“Our team hunt­ed for a spe­cial type of po­lar­iz­a­tion called ‘B-modes,’ which rep­re­sents a twist­ing or ‘curl’ pat­tern in the po­lar­ized ori­enta­t­ions,” said study co-lead­er Ja­mie Bock of the Cal­i­for­nia In­sti­tute of Tech­nol­o­gy.

Gravita­t­ional waves squeeze space as they trav­el, and this squeez­ing pro­duces a dis­tinct pat­tern in the cos­mic mi­cro­wave back­ground, the sci­en­tists ex­plained. Gravita­t­ional waves have a “hand­ed­ness,” much like light waves, and can have left- and right-hand­ed po­lar­iz­a­tions.

“The swirly B-mode pat­tern is a un­ique sig­na­ture of gravita­t­ional waves be­cause of their hand­ed­ness. This is the first di­rect im­age of gravita­t­ional waves across the pri­mor­di­al sky,” said co-lead­er Chao-Lin Kuo of Stan­ford Uni­vers­ity in Cal­i­for­nia.

The team ex­am­ined spa­tial scales on the sky span­ning about one to five de­grees, two to ten times the width of the full Moon. To do this, they trav­eled to the South Pole, where the views are clear­er, and said they were sur­prised to de­tect a B-mode po­lar­iz­a­tion sig­nal con­sid­erably stronger than many ex­pected. “This has been like look­ing for a nee­dle in a hay­stack, but in­stead we found a crow­bar,” said co-lead­er Clem Pryke of the Uni­vers­ity of Min­ne­so­ta.

* * *

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Homepage image: the sun sets behind BICEP2 telescope (foreground) and the South Pole Telescope (background). (Courtesy Steffen Richter, Harvard U.)

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Astronomers say they have detected “ripples” in space and time caused by a process in which our universe expanded out of control during its first fleeting fraction of a second. The process is said to have begun almost 14 billion years ago during the Big Bang, an explosive event that gave birth to the universe. In an unimaginably small amount of time, the theory goes, the universe stretched to be far bigger than what our best telescopes would be able to see. This version of the Big Bang theory is known as “inflation.” Scientists from a research collaboration called BICEP2 announced on Monday what they called the first direct evidence for this cosmic inflation. Their data also represent the first images of gravitational waves, or ripples in space-time. These waves have been described as the “first tremors of the Big Bang.” Finally, they said, the data confirm a deep connection between quantum mechanics, the prevailing theory that describes the realm of subatomic particles, and general relativity, which describes events on cosmic scales. “Detecting this signal is one of the most important goals in cosmology today. A lot of work by a lot of people has led up to this point,” said John Kovac of the Harvard-Smithsonian Center for Astrophysics, leader of the BICEP2 collaboration. The findings came from observations by the BICEP2 telescope of the cosmic microwave background—a faint glow left over from the Big Bang. Tiny fluctuations in this afterglow provide clues to conditions in the early universe. For example, small differences in temperature across the sky show where parts of the universe were denser, eventually condensing into galaxies and galactic clusters. The cosmic microwave background is a form of light, and light can be “polarized,” meaning many waves vibrate in similar directions. This can occur after light scatters off atoms or other particles; on Earth, sunlight becomes polarized after hitting the atmosphere. “Our team hunted for a special type of polarization called ‘B-modes,’ which represents a twisting or ‘curl’ pattern in the polarized orientations,” said study co-leader Jamie Bock of the California Institute of Technology. Gravitational waves squeeze space as they travel, and this squeezing produces a distinct pattern in the cosmic microwave background, the scientists explained. Gravitational waves have a “handedness,” much like light waves, and can have left- and right-handed polarizations. “The swirly B-mode pattern is a unique signature of gravitational waves because of their handedness. This is the first direct image of gravitational waves across the primordial sky,” said co-leader Chao-Lin Kuo of Stanford University in California. The team examined spatial scales on the sky spanning about one to five degrees, two to ten times the width of the full Moon. To do this, they traveled to the South Pole, where the views are clearer, and said they were surprised to detect a B-mode polarization signal considerably stronger than many expected. “This has been like looking for a needle in a haystack, but instead we found a crowbar,” said co-leader Clem Pryke of the University of Minnesota.