Transcript or CMB - Planck Mission

Visualization Project
Seeing and Hearing the CMB
Education and Public Outreach Group, Planck Mission, NASA:
University of California, Santa Barbara:
Purdue University:
Purdue-Calumet, VisLab
Lead Application Developers:
Jerry Dekker, Lead Programmer
John “Jack” Moreland,
Visualization Specialist
Haverford College
Bruce Partridge, Friend of the
Project
Department of Physics
Jatila van der Veen (formerly at Purdue-Cal.)
Philip Lubin
UCSB AlloSphere
JoAnn Kuchera-Morin, AlloSphere Director
Lead Application Developers:
Wesley Smith and Basak Alper,
Ph.D. candidates in Media Arts Technology
Matt Wright, Media Systems Engineer
Lead P.I., Planck Visualization Project: Jatila van der Veen
Planck Project Scientist and Lead Principal Investigator at NASA/JPL:
Charles R. Lawrence
Planck Launch: May 14, 2009
photo: Charles R. Lawrence
Planck is a Mission led by the European Space Agency, with significant participation by
NASA.
Planck’s purpose is to map the Cosmic Microwave Background radiation (or CMB)
- the oldest light we can detect - with a sensitivity of a few millionths of a degree Kelvin,
and an angular resolution as fine as 5 arc minutes on the sky.
This is equivalent to being able to detect the heat of a
rabbit on the Moon from the distance of the Earth, and
resolve a bacterium on top of a bowling ball!
The CMB is all around us, bathing the Earth, filling all of the visible Universe!
5
The CMB originated at the time when the
universe first became cool enough so as to be
oldest light
transparent to electromagnetic radiation,
approximately 380,000 years after the Big Bang.
The CMB is like a wall of fog that we can’t see
behind...
youngest
6
A condensed slice through spacetime:
transparent
opaque
CMB wall
Although the early universe was bright and hot, the CMB signal is
observed today as microwaves, invisible to human eyes, due to the
stretching of space over the past 14 billion years.
CMB
Image credit: http://mail.jsd.k12.ca.us/bf/bflibrary/images/electromagnetic-spectrum.jpg
To a first order, the CMB is uniform, and
follows a perfect black body thermal radiation
curve which peaks at 2.725 Kelvin. This
temperature corresponds to a wavelength of
light of 2 mm, or microwave radiation.
An observed temperature difference across the
sky of a few parts in 1,000 is not part of the
CMB, but an artifact of our motion through the
cosmos. Because of our net motion through
space, the sky temperature appears slightly
warmer in the direction in which we are
moving, and slightly cooler in the direction
from which we are coming.
warmer
cooler
9
In 1992 the COBE satellite revealed small
variations in the CMB for the first time, all
across the sky, which are independent of the
motion of the Earth through space. COBE’s
instruments were sensitive to few parts in
100,000 in temperature, and had a spatial
resolution of 70 of arc on the sky.
Called anisotropies, meaning deviations from uniformity,
these small temperature variations that we observe in
the CMB today are the light echoes of variations in the
distribution of matter and energy in the early universe,
which acted as ‘seeds’ for galaxies to form later on, by
gravitational attraction.
COBE all-sky map
The CMB anisotropies give us a picture of the Last
Scattering Surface of the expanding universe, seen
at one moment in time – when matter and
radiation first separated. Observing the CMB
anisotropies with a sensitivity of a few parts in
100,000 is like measuring centimeter-height ripples
on the surface of the ocean as seen from an
airplane, a few kilometers above the ground.
10
For reference, 10 of arc on the sky
is approximately equal to the
width of your pinky, held at
arm’s length.
A patch of 5 arc minutes on a side
is approximately 6 billionths of
the total area of the sky.
11
Since the 1980’s, numerous balloon-borne and ground-based experiments have mapped
portions of the sky at increasingly fine resolution, but only two previous satellites, COBE and
WMAP, have successfully mapped the entire sky. This figure compares the resolution with
which COBE and WMAP have been able to map the CMB, with that expected from Planck.
1989
2000
May 14, 2009
How will Planck complete its
mission of mapping the CMB
at such fine resolution?
Primary mirror,
1.9 x 1.5 meters
Secondary
mirror
1.1 x 1.0
meter
The Planck spacecraft is 4.2 m high and has a
maximum diameter of 4.2 m, with a launch
mass of around 1.8 tons. The spacecraft
comprises a service module, which houses
systems for power generation and conditioning,
attitude control, data handling and
communications, together with the warm parts
of the scientific instruments, and a payload
module. The payload module consists of the
telescope, the optical bench, with the parts of
the instruments that need to be cooled - the
sensitive detector units - and the cooling
systems.
13
Planck was built by an international
industrial team. Different components,
including the mirrors, instruments,
payload package, and cooling systems were
built in France, Austria, Germany,
Denmark, Finland, Belgium, Italy, Ireland,
the Netherlands, Norway, Portugal, Spain,
Sweden, Switzerland, the United Kingdom,
and the United States.
14
Planck will measure the
temperature of the sky
across 9 frequency
channels.
HFI (High frequency Instrument):
an array of microscopic
temperature sensors called spider
web bolometers, cooled to 0.1 K
LFI (Low frequency Instrument):
an array of radio receivers using
high electron mobility transistor
mixers, cooled to 20 K.
HFI feed horn
array
LFI feed horn
array
15
Peak frequency response for each detector, compared with the sky signals
HFI
LFI
30
44
70
100
143
217
353
545
857
Expected maps of the sky at each frequency:
17
What do we expect to learn from the data?
From the accurate temperature maps, we will be able to calculate the Power
Spectrum of the anisotropies of the CMB extremely accurately. From a
careful analysis of this power spectrum, we expect to derive important
characteristic properties of the Universe,
and resolve questions in fundamental physics.
map
power spectrum
fundamental
physics
18
What techniques do we use to extract information from
these data sets?
slide adapted from Mark Whittle
Planck is measuring the
microKelvin fluctuations
in temperature
which are translated into
slightly stretched (red
shifted) and compressed
(blue shifted) fluctuations
in microwave radiation.
From these microwave
fluctuations, we infer
pressure differences in the
universe at the time that
matter and radiation first
separated. These pressure
differences indicate
lumpiness in the
distribution of matter and
radiation at the time that
matter and energy first
separated – the CMB. The
power spectrum of the
CMB tells us the sizes of
the lumps in the early
universe. We analyze the
power spectrum of the
CMB using techniques
that we know from the
physics of MUSIC.
Planck will also
map the
polarization of
the CMB
Mapping the polarization
of the CMB will give us an
idea of how photons
scattered off charged
particles on the Last
Scattering Surface. This
will give us a picture of the
distribution of matter in
the universe at that time –
similar to the way in which
sunlight scatters off the
surface of a lake reflects
the undulations in the
surface of the water.
20
The Planck Mission in Virtual Reality
Under development at Purdue University
Jerry Dekker, Jack Moreland,
Jatila van der Veen
Utilizing state-of-the-art visualization,
gaming, and distributed computing
technology, we are developing
applications for the Planck Mission
using Virtual Reality to reach the
widest possible international audience.
Starting from a
flight simulator screen ...
...the user can explore the mission
from launch...
to orbital insertion...
to data gathering operations...
from any vantage point in the solar system.
Finally, the user stands “in space” while Planck paints
the CMB all around, beyond the starry background.
On May 14, 2009, at 13:12 UT, Planck was launched
from the European Space Agency’s launch pad in
Kouru, French Guiana.
Hi-tech visualization facilities:
• VR facilities
• Planetaria
• Virtual Classrooms
Museums and Science Centers
• Thousands of potential sites!
• DVDs for Museums and mass dist.
• Kiosk interactive display
• Passive viewing as movie
Web Distribution
Currently still in
development and testing.
If you wish to receive a
copy to test, please send
an email to
[email protected].
• Download, single computer
• Interactive served application
• Computers in classrooms
Popular Culture
• iPhone application
• Google Universe
• Screen savers
Available in a variety of 3D technologies, from simple
anaglyph to high-tech
varieties.
The Music of the Cosmos
Using sound to explain how we extract information about the early universe
from the power spectrum of the CMB.
primordial
Planck
COBE
WMAP
Under development at UC Santa Barbara
Jatila van der Veen
JoAnn Kuchera-Morin
Wesley Smith, Basak Alper, Matt Wright
The variations in temperature that
we observe in the CMB ...
T 

T

...tell us about variations in
density in the early universe,
which we now observe as...
... anisotropies in the CMB.
The CMB anisotropies originate from two different processes :
Initial distortions in the actual shape of the Universe, which
originated in the first moments of its existence
Gravity-driven pressure waves in the matter-radiation fluid
which filled the young universe during the first 380,000 years of
its existence – up to the time when matter and radiation
separated.
Those gravity-driven pressure
waves in the matter-radiation
fluid of the early universe not
only left their imprints in the light
of the CMB; they determined the
distribution of matter and energy
in the universe at later times, as
seen in the large-scale clusters
and walls of galaxies.
Images courtesy of Professor Max Tegmark, MIT
That is why it is so important to understand the scale of anisotropies in the CMB: the
variations in the oldest light of the universe predict the distribution of matter and energy
throughout the universe. This includes “normal” matter, in the form of galaxies that emit
radiation, “exotic” dark matter, which gravitates but does not shine, and the stranger still
dark energy.
In a sense,
understanding
the CMB
is like deciphering
the genetic code of
the universe!
Measuring and analyzing the CMB is based on the same principles which
are involved in making music and broadcasting it!
Pressure waves (sounds) in the concert hall are converted to electromagnetic radiation,
transmitted across spacetime, and reconverted to sound waves that your ears can hear.
Similarly, pressure waves in the early universe resulted in variations in the light that was emitted as
radiation and matter decoupled. This light has been transmitted across spacetime (nearly 14 billion
years!) to our microwave detectors. Using techniques that are familiar to sound engineers, we can
convert these light echoes into to sound that your ears can hear.
In order to understand how we can listen to the sounds of the early universe,
we first need to understand how sounds are produced on Earth.
Sound waves are just pressure waves
which have wavelengths and frequencies
that we can hear. Humans can hear
frequencies from around 20 to
20,000vibrations/second (Hertz).
The frequency, or
number of vibrations
per second,
determines the pitch
of the sound we hear.
Higher frequency =
more vibrations/sec =
higher pitch.
Figures adapted from Mark
Whittle, University of Virginia
Higher frequency
waves have shorter
wavelengths, and
lower frequency
waves have longer
wavelengths, as
indicated in these
pictures.
Frequency and
wavelength are
related by the speed
of sound by the
following equation:
Wave speed = frequency x wavelength
Thus if you know the speed of sound and the frequency, you can calculate wavelength.
The speed of sound in air is approximately 330 meters/second. So…
The “red tone” of 200 Hz has a wavelength of 330 m/sec / 200 Hz = 1.65 meters.
The “cyan tone” of 600 Hz has a wavelength of 330 m/sec / 600 Hz = 0.55 meters or 55 cm.
The “magenta tone” of 1000 Hz has a wavelength of 330 m/sec / 1000 Hz = 0.33 meters or 33 cm.
The amplitude of the pressure variations determines the loudness of
the sounds we hear. Higher amplitude = greater variation in
pressure = louder sound.
Figure adapted from Mark Whittle, University of Virginia
The temperature variations of the CMB indicate pressure variations of a few parts
in 10,000, or ΔP/P of 10-4 = 110 db,
approximately the volume of a typical rock concert.
Finally, we need to understand how instruments produce pleasing sounds:
To produce musical tones, you need an object with a well-defined shape
and size, which can vibrate – a RESONATOR.
Resonators – such as flutes, guitars,
drums, or bells - have a fundamental
tone which is the longest wavelength
that can fit within the walls
of a given resonator.
The fundamental is the lowest
pitch that a given resonator can
produce. Higher harmonics are
whole number multiples of the
fundamental frequency.
The fundamental frequency
tells you the time it takes for the
longest wave to travel
across the
resonator and back
one time.
Bigger resonators produce lower tones. Click on the speaker
icons to hear music produced by pressure waves vibrating in
each of these wind instruments.
Next we’ll investigate the sound waves
produced by a computer, by real
instruments, and by a star such as the
Sun.
Finally, we’ll apply these concepts to
understanding the sounds produced by
pressure waves in the early universe.
The simplest sound wave one can imagine is just a single pure tone, with only one
frequency, corresponding to a single wavelength. The top figure shows this tone as a
single frequency wave, with a period of 1/440th of a second, or .002273 second.
wavelength
Click on the speaker to
hear a pure “A” of 440
Hz, generated by a
computer:
The POWER SPECTRUM of any sound tells
you what frequencies are present and how loud
each one is.
Here is the power spectrum of this tone: a single peak
at a frequency of 440 Hertz, or cycles/second:
39
Here are 3 A’s, an octave apart: 220 Hz, 440 Hz, and 880 Hz. In the top figure,
we display the wave form, which is the superposition of the three waves, and
in the bottom figure we display the power spectrum of this sound, comprised
of these three notes.
The power spectra
and wave forms
shown on these pages
were produced using
the software “Cool
Edit Pro”
Click on the speaker
to hear the tones.
220
440
880
40
Here is the sound of a clarinet playing an A of 440 Hz.
Notice that even though only one note is being played,
the wave form and power spectrum are more complicated than
those of an A being played by a computer! This is because the way the pressure waves
bounce around inside the actual clarinet creates higher harmonics, or overtones, and it is
the overtones which allow you to distinguish one instrument from another, and notes played
by real instruments from the same notes synthesized by a computer!
Compare the sound of the clarinet
(above) playing an A of 440 Hertz,
with the sound of a pure A played on
a computer:
41
And here is the power spectrum of the clarinet playing an A of 440 Hz. The first peak
is the fundamental, at 440 Hz. The successive peaks represent the higher harmonics,
which are integer multiples of the fundamental. Compare the spectra and sounds of
the real clarinet and the synthesized sound generated by a computer.
Clarinet playing an A
440 Hz
880
1320
etc...
Pure A synthesized on a
computer has only one peak at
440 Hz.
42
Let’s compare the sound of a trumpet playing a middle C (261 Hz) with
the same note, synthesized on a computer. Here are the wave forms:
Trumpet
Source:
http://www.ugcs.caltech.edu/~ta
sha/
Computer
43
And here are the power spectra. Again, notice the higher harmonics are
multiples of the fundamental. The presence of these higher harmonics
allows you to tell that this note is played by a trumpet.
Trumpet
261
522
783
etc...
Pure C synthesized on a computer.
Notice a single peak at 261 Hz. The
absence of the higher harmonics makes
this note sound artificial!
44
The point of all this is to demonstrate that although instruments may play the same
pitch at the same loudness, each instrument (resonator) has a unique POWER
SPECTRUM which is determined by the size and shape of that instrument.
The power spectrum, consisting of the fundamental and higher harmonics, is
what gives each instrument its unique sound quality (which musicians call TIMBRE),
and allows us to distinguish the sound of a piano from that of a violin, trumpet,
clarinet, or a tone produced by a computer.
Trumpet
Clarinet
Before we apply these principles to the CMB, we have to look at one little problem:
Poor resonators produce “noisy” power spectra, with poorly-defined peaks. The universe was a
poor resonator, since it had no well-defined boundaries in space, thus we have to know how to
“clean up” a power spectrum before we can listen to the music of the cosmos!
If there is a fair amount of “hiss” in a
resonating system, it can be difficult to
pick out the peaks – the fundamental
and higher harmonics – in the power
spectrum. For example: Here’s our piper, playing
one note :
It is difficult to find the fundamental in this power spectrum, but with
mathematical tools called Fourier analysis (after the fellow who invented them)
we can remove the hiss and pick out the fundamental tone.
Here is the bag pipe again, but with its power spectrum “cleaned up” to pick
out the harmonics from the noise. We hear the fundamental, but the tone has
lost its breathy quality, so that it no longer sounds like a bag pipe.
Now we have are ready to analyze the sounds of natural systems,
starting with the Sun,
and then the universe!
Natural systems such as the Sun and the Earth are also resonators. The Sun, being a
ball of gas without well defined boundaries, produces very hissy sounds, like these,
which have been compressed by several orders of magnitude so as to be audible to
human ears:
Source: bison.ph.bham.ac.uk/
10 Hz
100 Hz
~420 Hz
1,000 Hz
48
Using the same Fourier analysis, we can clean up the Sun’s power
spectrum and pick out the fundamental and higher harmonics which are
buried in all the hiss. With the hiss removed, and scaled to audible
frequencies, the Sun would sound something like this:
... Sounds pretty eerie, doesn’t it!
The early universe was a resonator, albeit a very hissy one, like the Sun.
Thus it should have a fundamental tone which was determined by the size of
the universe at the time that the CMB was produced – when matter and
radiation first separated.
We can determine the wavelength of the fundamental from the power
spectrum of the CMB, and knowing the approximate speed of sound in the
early universe, we can calculate the fundamental frequency.
We can clean up the power spectrum, scale the frequencies to the range of
human hearing, and listen to the sounds of the early universe!
Slide courtesy of Mark Whittle, University of Virginia
Anisotropies of 20 and
smaller in the CMB
correspond to pressure
waves in the early
universe...
20
which correspond to the
fundamental and higher
harmonics in the power
spectrum of the CMB.
This graph
is more fully explained in the
next two slides...
52
Angular resolution of features, in degrees, on the sky
fundamental
Sound “Loudness”
Figure courtesy of Mark Whittle, University of Virginia
harmonics
Spatial frequency of features, expressed as waves over the surface of a sphere. Lower “l” means
larger wavelength, lower frequency. l (angular wave number) is approximately calculated as
1800/ where  = angular resolution (top scale of this graph).
Amplitude of temperature anisotropies
scaled to units of micro-Kelvin2
This graph compares spatial frequency on the sky to frequencies of sound,
scaled to the range of human hearing, and related to notes on a piano.
Figure adapted from website of Mark Whittle, University of Virginia
Amplitude of temperature anisotropies
scaled to units of micro-Kelvin2
Superimposed on the previous graph, here we show the range of spatial frequencies
mapped by each satellite
Planck
WMAP
COBE
primordial shape
of the universe
Figure adapted from website of Mark Whittle, University of Virginia
The speed of sound in the pre-CMB early universe was approximately:
c 3x108 m / sec
vsound 

 1.73x108 m / sec
1.73
3
The fundamental wavelength on the CMB tells the distance that the longest
wave, with the lowest tone, traveled in the first 380,000 years of the universe’s
existence. Converting 380,000 yearsv into
and multiplying by speed of
c
3seconds,
x10

sound gives us the approximate size of3the fundamental in “real” units:
8
s
sec
8 m
21
380,000 yrs  3.15 10
1.73 10
 2.08 10 m
yr
sec
7
Converting meters to light years, we get:
2.08 1021 m  9.46 1014 m / ly  220,000ly
Thus, 220,000 light years is the wavelength of the fundamental ‘note’
of the CMB. This means 1 wave every 220,000 years!
If the period is 220,000 years, this means that the fundamental frequency is 1
wave /220,000 years, or 1 wave in 6.94 x 1012 seconds!
We invert this number to calculate the fundamental frequency in Hertz:
1/6.94 x 1012 = 1.44 x 10-13 Hz (waves/second)
Human hearing ranges from ~ 20 Hz to 20,000 Hz, thus the fundamental
tone of the universe is between 1.4 x 1014 and 1.4 x 1017 times LOWER
than human hearing.
(We got this by dividing 20/1.44 x 10-13 and 20,000/1.44 x 10-13)
Since 1 octave = doubling in frequency, this comes out to around
51 octaves below the “concert A” of 440 Hz that we played in slide #39!
Figure courtesy of Mark Whittle, University of Virginia
Scaled to human hearing, the CMB sounds something like this:
58
Played in Cool Edit, the power spectrum of this sound looks like this:
“Cleaned up” using the same tools of Fourier analysis that we used
on the sounds of the Sun, we can hear the fundamental and higher
harmonics of the CMB, scaled to human hearing:
Further filtering gives
this ghostly tone:
Here is a comparison of the broad, “hissy” CMB spectrum of angular
wavelengths (C(l)), compared with a cleaned up power spectrum (P(k)),
compared with the filtered single tones of the power spectrum:
Figure and sound files courtesy of Mark Whittle, University of Virginia
The CMB represents the LAST echo of the sloshing sound waves
that propagated during the 380,000 years after the big bang.
Expanding universe creates deepening sound...
Sound file courtesy of Mark Whittle, University of Virginia
If you are ambitious, you can scale the power spectrum by different factors to
create the tones of different size universes, then add them together to create a
changing tone!
Changing the properties of the universe would give it a different
power spectrum...which would sound different.
You can use the program CMBFAST, which can be found at
http://lambda.gsfc.nasa.gov/ to change the ingredients of the
universe, get a new power spectrum, and then listen to its sounds.
The CMB Power Spectrum holds clues to understand fundamental
cosmological parameters, and may even allow us to distinguish
between particle and string models of inflation.
The tools for analysis are the similar to other types of harmonic
analysis.
Starting from the CMB Power Spectrum, you can use any sound
editing package to reproduce the sounds of the Universe.
This is a great way to incorporate music into a science class: The
Universe actually has a primordial sound!
This is a work in progress! If you wish to download a beta-version of
the Mission Simulation, please send email to
[email protected] for the anonymous ftp site at the Jet
Propulsion Lab where you can download it.
These slides will be posted somewhere on the site
www.deepspace.ucsb.edu in the near future.
Ultimately, we plan to distribute:
• A Virtual Reality simulation of the Plank Mission, and CMB
• An activity guide for teachers on understanding the CMB using
music
• An interactive lab for high school and college students, using
CMBFAST and listen to the sounds that are derived from the power
spectrum of each one.
For an in-depth treatment on Big Bang Acoustics:
http://www.astro.virginia.edu/~dmw8f/BBA_web/index_frames.html
Mark Whittle, University of Virginia
For more information about Planck:
http://planck.caltech.edu/ - NASA Planck page at JPL
http://www.esa.int/SPECIALS/Planck/index.html ESA Planck page
To receive a preliminary copy of the mission simulation for
classroom use, please send email to me at
[email protected]