- 2167 -
PLANCK - measures the Cosmic Microwave
Background. We have a Universe with 5%
normal matter, 27% dark matter, and 68% dark energy. At last, we can state,
with extraordinary confidence, what the Universe is made of. The curvature of the Universe is no greater
than 1-part-in-1000, indicating that the Universe is indistinguishable from
perfectly flat. Where have I heard that
before? Christopher Columbus did not
believe it either. Math: at the end of Review.
-
-
-
-
------------------ 2167
- PLANCK -
measures the CMB
-
- When
God made the Universe he left 95% of it to be a mystery, We only know 5% that we call Ordinary Matter
and that makes up the world and life that we understand. But, with that 5% we have built satellites
that made the measurements that bring us to this conclusion. We are using 3 satellites, COBE, WMAP, and PLANCK.
This is their story as of November, 2018.
-
- It's
been more than 50 years since humanity discovered a uniform bath of low-energy,
microwave radiation originating from all regions of the sky. It doesn't come
from the Earth, the Sun, or even the galaxy; it originates beyond every star or
galaxy we've ever observed. It is the
theoretical leftover glow from the Big Bang.
-
- The
cosmic microwave background (CMB), has had its properties measured extensively.
The most advanced observatory to ever measure its properties is the European
Space Agency's Planck satellite, launched in 2009. The satellite took its full
suite of data over many years. Here's
how it's measurements changed our view of the Universe forever.
-
- The
leftover glow from the Big Bang, the CMB, isn't uniform, but has tiny
imperfections and temperature fluctuations on the scale of a few hundred
microkelvin temperature. The Universe's
temperature is only non-uniform at a level that's less than 0.01%. Planck has
detected and measured these fluctuations to better precision than ever before.
-
- This
baby picture of the Universe measures light that was emitted when the Universe
was only 380,000 years old. In the
early 1990s, the COBE satellite gave us the first precision, all-sky map of the
cosmic microwave background, down to a resolution of about 7 degrees. About a
decade ago, WMAP managed to get that down to about half-a-degree resolution. Planck measured all the way down to just 5
arcminutes (0.07°) in nine different frequency bands.
-
-
Planck has measured this radiation and its fluctuations in more
frequency bands than any satellite that came before. COBE had four (only three
were useful), and WMAP had five. COBE could measure temperature fluctuations
that were approximately 70 microkelvin in magnitude; Planck can get down to
precisions of around 5 µK. The high
resolution and the multiple frequency bands have enabled us to understand,
measure, and subtract out the effects of dust in our galaxy better than ever
before.
-
- A
complete dust map of the Milky Way, provided by Planck, showcases a
lower-resolution, 2D map of what our galaxy's dust distribution looks like.
This 'noise' needs to be subtracted out to reconstruct the background,
primordial, cosmic signature that Planck gives us.
-
- Using the temperature fluctuations on large,
intermediate, and small scales we were able to figure out:
-
• how
much normal matter, dark matter, and dark energy are in the Universe,
•
• what
the initial distribution and spectrum of density fluctuations were,
• -
• and
what the shape or curvature of the Universe is.
-
- The
magnitudes of the hot and cold spots, as well as their scales, indicate the
curvature of the Universe. To the best of our capabilities, we measure it to be
perfectly flat. Baryon acoustic oscillations and the CMB, together, provide the
best methods of constraining this, down to a combined precision of 0.1%.:
-
- We
have learned:
-
• when
the Universe became reionized (and, therefore, when star formation reached a
certain threshold),
•
• if
there are fluctuations on scales larger than the horizon,
•
• whether
we can see the effects of gravitational waves,
•
• what
the number and temperature of neutrinos were back then,
-
- The
Universe has more matter and is expanding more slowly than we previously
thought. Before Planck, we thought the Universe was about 26% matter and 74%
dark energy, with an expansion rate in units of 73 km/s/Mpc. ( km/s/Mpc = kilometers per second per megaparsec. A
megaparsec is equivalent to 3.3 million lightyears distance).
-
- The
Planck measurements put the Universe
with 31.5% matter, that is 4.9% is normal matter and 26.6 % dark matter. 68.5%
is dark energy creating a Hubble expansion rate today of 67.4 km/s/Mpc.
-
. The latest Planck results also definitively
point to only 3 species of light neutrino.
And , that the mass of any individual neutrino species can be no more
than 0.04 eV/c2 which is more than 10 million times less massive than that of
an electron.
-
- We
also know that these neutrinos had a cosmic temperature that would correspond
to 72% of the temperature or kinetic energy that the CMB photons have; if they
were massless, the temperature would be just 2 K today, not 2.73K.
-
-
Other quantities have changed mildly. The Universe is a little
older at13.8 instead of 13.7 billion
years that we previously thought. The
distance to the edge of the observable Universe is a lit
-
- So,
with all the data in:
-
• Yes
to inflation, no to gravitational waves created by inflation.
•
• Yes
to three very light, standard-model neutrinos, no to any extras.
•
• Yes
to a slightly slower-expanding, older Universe, no to any evidence for spatial
curvature.
•
• Yes
to a little bit more dark matter and normal matter, yes also to a little less
dark energy.
•
• No
to changing dark energy; no to the Big Rip or the Big Crunch.
-
- We
have a Universe with 5% normal matter, 27% dark matter, and 68% dark energy. At
last, we can state, with extraordinary confidence, what the Universe is made
of. Ok, now I can have a drink of wine
my job is done here.
-
-----------------------------------------------------
-
- Ok I
have had my glass of wine. So now let's do some math. The CMB picture shows light and dark patches
across the sky when we magnify it by 100,000 times. We assumes these more dense and less dense
patches are the early formation of galaxies.
How big are they?
-
- A typical dark patch is 1/2 millimeter in diameter
when the photo is magnified to be 160 millimeters width. The photo spans 45 degrees of arc or 1 millimeter
per 0.28 degrees. 1/2 millimeter would
be 0.14 arc degrees, and that is about the size of the smaller spots.
-
- 45
arc degrees / 160 millimeters = 0.28
arc degrees per millimeter.
-
- To
get a feel of this size across the sky think of the Full Moon which is 0.5 arc
degrees diameter. Therefore the CMB
spots are about 1/3 the size of the Full Moon.
-
- The
scale at that distance to reach the CMB is 62 parsecs per arc second.
-
- A
parsec is an early astronomer's definition for units of great distances. It is the distance of one astronomical unit
that subtends an angle of one arc second.
It is equal to 3.26 light years distance,
which is equal to 19 trillion miles. Ok, an astronomical unit is the distance
between the Earth and the Sun, about 93
million miles. ( The earlier astronomers
had their own way of doing things. We live
with their definitions today.) 1 degree
is 3,600 arc seconds.
-
- That
would put the small dark spots in the CMB at 0.14 degrees * 3600 arc
seconds / degree * 62 parsecs / arc
second = 35,000
parsecs . So the dark spot on the CMB is 35,000 parsecs x 3.26
lightyears / parsec
= 114,000 lightyears.
-
- The Milky Way Galaxy is 100,000 lightyears across. So, these dark spots in the CMB are about the size of our Milky Way galaxy today. Our Galaxy is about 13.51 billion years old. The age of the Earth is 4.543 billion years. See what a glass of wine will do?
- The Milky Way Galaxy is 100,000 lightyears across. So, these dark spots in the CMB are about the size of our Milky Way galaxy today. Our Galaxy is about 13.51 billion years old. The age of the Earth is 4.543 billion years. See what a glass of wine will do?
-
-
November 14, 2018. An
Index of more recent Reviews is available.
----------------------------------------------------------------------------------------
-----
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---
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--------------
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to: ------ jamesdetrick@comcast.net ------
“Jim Detrick” -----------
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--------------------- Wednesday, November 14, 2018 -------------------------
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