Why Is The Solar System: Cosmically Aligned?
Why Is The Solar System: Cosmically Aligned?
Why Is The Solar System: Cosmically Aligned?
Why is the
solar system
cosmically
aligned?
The solar system seems to line up
with the largest cosmic features. Is
this mere coincidence or a signpost
to deeper insights? ⁄ ⁄ ⁄ BY dragan huterer
I
magine visiting a Museum of Cos- a good distance away from the display to
mology, where the signature display get a better perspective, you notice the
is a giant case that contains a realistic larger structures: star clusters and galaxies,
model of the observable universe. each containing a sea of suns. Stepping
Herein lie all the stars and galaxies back farther, you start to discern a web of
we can see from Earth — the parts of the filaments in the vastness, and notice that
universe from which light has had enough clusters of galaxies lie at the intersections of
time to reach us in the 13.7 billion years the largest filaments. At this distance from
since the Big Bang. The museum curators the display, you can see patterns that extend
have done an excellent job, and the model 45 billion light-years, all the way out to the
is complete with planets, stars, and galaxies. edge of the observable universe.
As you stand in front of the display and Intrigued by this zoo of structures on
squint, you can barely discern the smallest- different scales, you walk over to the oppo-
scale features: billions of individual stars, site end of the huge Main Hall to get a
many with planets and moons. As you step sense of the big picture. And you are
Ecliptic plane
Huterer
The CMB in cosmic history
view, we could only see galaxies that are no
First stars farther than 45 billion light-years from us.
appear Dark energy accelerates Light from the more distant objects simply
380,000 years universe’s expansion
after Big Bang has not had time to reach us yet.
To map the universe’s structure we
sters evolve
Galaxies, galaxy clu would need something like a fossil record
preserving information about conditions in
the early universe, when the seeds were
planted that grew into structures we
Big WMAP observe 13.7 billion years later.
Bang Universe expands Fortunately, we have such a fossil. It’s
called the cosmic microwave background
(CMB). Arno Penzias and Robert Wilson of
Bell Laboratories discovered it in 1965.
In the early universe, photons (particles
of light with zero mass) and protons and
electrons (particles found in atoms)
swarmed in a dense mass, like a vast num-
ber of bees trapped in a box. Around
CMB map by 380,000 years after the Big Bang, however,
Wilkinson Microwave
Anisotropy Probe (WMAP) an important transition occurred: The
expanding universe became transparent to
radiation, and the photons were free to
travel. Today we observe the CMB as a fog
of microwave photons coming at us from
all directions, filling the entire universe.
IN THE FIRST moments after the Big Bang, the universe underwent a period of rapid
expansion. About 380,000 years later, the universe expanded enough to become trans
parent to radiation. From that time forward, particles of light (photons) traveled freely
Cosmic snapshot
throughout the cosmos. The cosmic microwave background (CMB) is a record of the
The CMB is a snapshot of the early uni-
universe’s state at that moment. As the universe expanded, stars and galaxies evolved. verse. After the Big Bang, gravity drew the
Later, large-scale structures such as galaxy clusters emerged. The Wilkinson Microwave densest regions together. These concentra-
Anisotropy Probe (WMAP) mapped the cosmic microwave background. NASA/WMAP Science Team tions of matter evolved over eons of time
into galaxies, galaxy clusters, and all the
shocked to see vast patterns within all those how could the early universe possibly have other cosmic structures we observe today.
stars and galaxies that seem to line up with “known” about the solar system’s geometry The less-dense, rarefied regions evolved
the direction of the Sun’s motion through when it developed 4.5 billion years ago? into vast expanses of cosmic emptiness,
the universe. Even stranger, some aspects of Could such a bizarre alignment have arisen filling the space between galaxies. You can
the cosmic geometry seem more flattened in the early universe, or is the answer in the see the results of gravitational collapse in
than spherical, and line up nearly perpen- solar system itself — some as-yet-unknown the night sky as a seemingly random pat-
dicular to the plane along which the planets factor that skews our observations? tern of stars and galaxies.
race around the Sun. The quest for an answer has whetted the The CMB’s temperature is nearly uni-
In reality, you would need a very special appetites of cosmologists to understand the form across the sky, measuring just 2.73
kind of vision to see the alignments cos- structure of the universe on its largest Kelvin, or 2.73° Celsius above absolute zero.
mologists have begun to find in the geo scales. Moreover, solving the mystery of But the CMB is not completely uniform; it
metry of the universe. Seeing them requires cosmic alignments may ultimately require contains many small patches where the
sophisticated mathematical analysis that us to revise some bedrock assumptions of background temperature is warmer or
enables us to explore the finest details of modern cosmology and what happened in cooler, varying slightly above and below
how the universe is put together. the first moments after the Big Bang. 2.73 K. These variations in the sea of radia-
Careful analyses have confirmed these tion are small, about one part in 100,000, or
alignments exist. But we don’t know A look in the microwave equivalent to the roughness of dust on a
whether they are bizarre coincidences or if With modern telescopes and sensitive billiard ball’s surface.
something more fundamental is at work. instruments, we can observe distant galax- The CMB’s rough spots, called anisotro-
The origins of the universe’s structure lie ies and clusters of galaxies, and accurately pies, reflect inhomogeneity in the early uni-
in the first moments after the Big Bang. But map their distribution. Unfortunately, it’s verse — ripples, if you will, on the surface
not possible to “zoom out” from our pres- of the vast photon sea that existed after the
Dragan Huterer is a theoretical cosmologist ent moment in time and space to observe Big Bang. Unlike stars, anisotropies in the
and a professor in the department of physics at the entire universe. Moreover, even with a CMB are extremely faint, invisible to the
the University of Michigan in Ann Arbor. perfect telescope and nothing blocking our naked eye and even to most telescopes.
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From multipoles to WMAP
Monopole Dipole Quadrupole
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