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and the edge of the universe. Dust
clouds and the effects of gravity
had interfered with the radiation on
its long journey to Earth. The data
from the three instruments were
used to detect and correct these
so-called secondary anisotropies.
Tiny fluctuations
After 10 months in space, COBE’s
helium ran out, which limited
the function of the two infrared
detectors, but the DMR continued
working until 1993. By 1992, the
COBE team’s analysis had shown
what they were looking for. The
CMB, and thus the early universe,
was not a uniform blob of energy.
Instead it was riddled with tiny
but significant fluctuations. The
differences were minute, with
density variations of about 0.001
percent. However, the pattern was
enough to explain why the contents
of the universe are clustered
together, while the rest of space
is made from vast empty voids.
THE TRIUMPH OF TECHNOLOGY
Since COBE, two subsequent
missions have added detail to
the picture of the CMB. Between
2001 and 2010, NASA’s Wilkinson
Microwave Anisotropy Probe
(WMAP) mapped the CMB to
a higher resolution than COBE.
Then, from 2009–2013, the ESA’s
Planck Observatory produced the
most accurate map to date.
Every wrinkle on the map is the
seed from which an entire galaxy
formed about 13 billion years ago.In addition to mapping the CMB,
WMAP measured the age of the
universe as 13.77 billion years, dark
matter as 24.0 percent of the universe,
and dark energy as 71.4 percent.
Improving resolution of the CMB
COBE’s imaging of the CMB shows
slight variations in a 10-sq-degree
panel of its all-sky map, proving that
the CMB is not uniform.
WMAP’s map of the CMB shows
greater detail within the same panel,
revealing smaller-scale features that
COBE could not identify.Planck’s resolution is 2.5 times greater
than that of WMAP, showing features as
small as^1 ⁄ 12 of a degree. This is the most
detailed map of the CMB to date.However, no known galaxy can
be seen forming in the CMB. The
CMB radiation detected today has
traveled from near the edge of the
observable universe over the course
of most of the age of the universe.
Astronomers can only see 13.8 billion
light-years away, but most of the
universe now lies farther away
than that. The galaxies forming in
the CMB are now far beyond what
can be observed, and are receding
faster than the speed of light. ■