Transcript Research Assignment 1 () - Department of Physics and Astronomy

PHYS 2070
Research Assignment 1:
The Early Universe
By Cole Treyturik
What is meant by the “Early”
Universe?
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A very broad topic
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Usually defined as the first 100m years of the Universe's existence
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Began with the Big Bang
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[1], [5], [6]
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What is the Big Bang?
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Currently the most accepted, most supported theory for the early
development of the Universe
In the 1920s, Edwin Hubble determined that galaxies further away from us
appear to be moving away from us faster than those that are closer
In 1931, Georges Lemaitre presented a theory of the “primeval atom,” which
theorized that since everything appeared to be moving away, there must
have been a time at which everything was much closer together.
[5], [6]
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What is the Big Bang?
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The name “Big Bang” was coined by Fred Hoyle during an interview in 1949
After WWII, there were two theories about the “origin” of the Universe; the
Big Bang theory and the Steady State theory
The Big Bang theory gained general acceptance as more and more
evidence was found for it
Last nail in the Steady State theory's coffin was when the CMB radiation
was discovered and confirmed
[5], [6]
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What is the Big Bang?
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A theory that postulates that the Universe was, at one time, infinitely dense
and infinitely hot
This occurred about 13.7 billion years ago
For some unknown reason, the Universe began to expand at an exponential
rate
It is the beginning of this expansion that most people refer to as “the Big
Bang”
Actually a theory that attempts to explain what happened after the
expansion began
[5], [6]
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Timeline of the Big Bang
Epoch
From t=
To t=
Planck
0s
10^-43 s
GUT*
10^-43 s
10^-35 s
Quark
10^-35 s
10^-4 s
Lepton
10^-4 s
10^2 s
Nuclear
10^-2 s
5x10^4 yr
Atomic
5x10^4 yr
2x10^8 yr
Galactic
2x10^8 yr
3x10^9 yr
Stellar
3x10^9 yr
?
*GUT = Grand Unified Theory
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Summary of Epochs
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Planck Epoch: Little is known of the Planck Epoch, as most known laws of
physics break down this close to the Big Bang. It is believed that all four
fundamental forces – Gravity, Electromagnetic, Strong Nuclear and Weak
Nuclear – are unified as one force during this period
GUT Epoch: The gravitational force separates from the other three forces
as the universe expands and cools. Near the end of the epoch, the Strong
Nuclear force and the Electroweak force (electromagnetic and weak nuclear
forces combined) separate
[1], [2]
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Summary of Epochs
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Quark Epoch: Universe undergoes and incredibly rapid expansion in size,
referred to as “inflation.” This inflation “smoothed out” the Universe allowing
for the virtually uniform appearance of the CMB today
Lepton Epoch: Particles and anti-particles, created shortly after the Big
Bang, annihilate each other. Most of the anti-particles are destroyed, due to
annihilation or instability, allowing normal particles to become dominant in
the Universe
Nuclear Epoch: Deuterium (heavy Hydrogen) and Helium begin to form by
fusion during this epoch
[1], [2]
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Summary of Epochs
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Atomic Epoch: Atoms begin to form in this epoch, as the electroweak force
splits into the electromagnetic force and the weak nuclear force
Galactic Epoch: Large, primordial galaxies begin to form. The first stars –
much shorter lived, and likely hotter, than most stars today – form, as do the
first quasars
Stellar Epoch: The first stars die in violent supernova, creating more
elements. Smaller, cooler stars (such as the Sun) begin to form, and even
smaller objects – planets, asteroids and comets – become more abundant
[1], [2]
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Baryon-Lepton Symmetry
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In the early Universe, there was a symmetry between Baryons and Leptons
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In order for neutrinos to have a non-zero mass, this can not hold true
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Thus a spontaneous symmetry breaking of the B-L symmetry is required
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This is explained in detail in the paper Spontaneous B-L Breaking as the
Origin of the Hot Early Universe by Wilfried Buchmüller, Valerie Domcke
and Kai Schmitz, of the Deutsches Elektronen-Synchotron in Germany.
http://arxiv.org/abs/1202.6679
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What is the CMB?
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Stands for “Cosmic Microwave Background”
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Is a radiation in the microwave wavelength which fills the entire Universe
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Is a near-perfect Black Body spectrum at 2.725 K
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Emitted about 380,000 years after the Big Bang
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The result of neutral atoms first forming, allowing photons to begin freely
traveling through space instead of being “scattered” by free electrons and
protons
Only the Big Bang has properly predicted the near-perfect black body curve
of the CMB, which is why it is the currently most supported model of the
Universe
[3], [4]
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Studying the CMB?
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The CMB is a very active field of research in modern cosmology
As our instruments gain ever increasing sensitivity, we can gain an ever
better insight into the early Universe by observing the CMB
The paper The Cosmic Microwave Background: Observing Directly the
Early Universe by Paolo de Bernardis and Silvia Masi of the Sapienza
Universita di Roma in Italy has excellent examples of the kind of data we
can gather from this event, as well as why it is important to continue refining
out equipment
http://adsabs.harvard.edu/abs/2012arXiv1208.0298D
[3], [4]
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Observing the Early Universe?
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Due to its very nature, the early Universe is very hard to actually observe
directly
There's a limit as to how far we can look back in time: the Universe was
essentially opaque before the CMB was emitted
Powerful telescopes (such as Hubble) are able to see back billions of years
Three examples of such from Hubble:
- Hubble Deep Field, 1995 (HDF)
- Hubble Ultra Deep Field, 2004 (HUDF)
- Hubble eXtreme Deep Field, 2012 (XDF)
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Observing the Early Universe?
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The most recent of Hubble's Deep Fields is the eXtreme Deep Field, XDF
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Over two million seconds of exposure time
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An area “a small fraction of the angular diameter of the Full Moon”
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Over 5500 galaxies, faintest less than one ten-billionth of human eye
visibility
http://tinyurl.com/eXtremeDF
[3], [4]
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Hubble Deep Field
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Hubble Ultra Deep Field
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Hubble eXtreme Deep Field
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Image Credits
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Hubble Deep Field, Hubblesite.org
http://hubblesite.org/newscenter/archive/releases/1996/01/image/a/
Hubble Ultra Deep Field, Hubblesite.org
http://hubblesite.org/newscenter/archive/releases/2004/07/image/a/
Hubble eXtreme Deep Field, nasa.gov
http://www.nasa.gov/mission_pages/hubble/science/xdf.html
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Bibliography
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[1] University of Oregon. 2011. The Early Universe. Eugene, OR: University of Oregon Physics
Department. http://physics.uoregon.edu/~jimbrau/astr123/Notes/Chapter27.html
[2] Sean Carroll. 2008. Cosmology Primer. California Institute of Technology Physics Department.
http://preposterousuniverse.com/writings/cosmologyprimer/index.html
[3] E. Komatsu et al. Five-Year Microwave Anisotropy Prove (WMAP) Observations: Cosmological
Interpretation. astro-ph
http://arxiv.org/abs/0803.0547
[4] NASA. 2010. WMAP's Introduction to Cosmology. National Aeronautics and Space
Administration. http://map.gsfc.nasa.gov/universe/
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[5] Hawking S. 1988. A Brief History of Time. New York, NY: Random House. 248 pp.
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[6] Hawking S. 2001. The Universe in a Nutshell. New York, NY: Random House. 215 pp.
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