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Monday , January 10, 2011. The Cosmic Foundations of the Origin of Life. Definition of the Universe. the huge space which contains all of the matter and energy in existence everything - not just everything you see, but everything that ever was, is, or will be

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Definition of the Universe
  • the huge space which contains all of the matter and energy in existence
  • everything - not just everything you see, but everything that ever was, is, or will be
  • the universe is everything that we can perceive and more
  • it is all the mass that exists, from the largest galaxies to the tiny subatomic particles, and since mass is exchangeable with energy, it is also all the forces and energies that exist
Building Blocks of the Universe
  • while the microscopic realm of atoms and nuclei seems far removed from the vast realm of planets, stars and galaxies, they are the building blocks from which all else is made
  • the behaviour of very large objects frequently depends on the laws that govern their smallest components
Fundamental Particles of Mattter
  • all matter is composed of atoms
  • atoms are an ordered collection of various subatomic particles - the central nucleus contains the protons and neutrons, around this are electrons
  • while electrons (a type of lepton) are true fundamental particles, protons and neutrons are made up of smaller particles, called quarks
in the modern theory, known as the Standard Model, there are 12 fundamental matter particle types and their corresponding antiparticles
  • the matter particles divide into two classes, quarks and leptons
  • there are six particles of each class and six corresponding antiparticles
  • in addition, there are gluons, photons, and W and Z bosons, the force carrier particles that are responsible for strong, electromagnetic, and weak interactions respectively - these force carriers are also fundamental particles
  • every quark and lepton has a corresponding anti-quark and anti-lepton
  • anti-electron (or positron) is identical to an ordinary electron
  • when a particle and its corresponding anti-particle meet, the result is mutual annihilation
  • the combined mass of the particles and anti-particle turns completely into energy in accord with E = mc2
  • this process also works in reverse, as occurred during the first few moments after the Big Bang
Fundamental Forces in the Universe
  • Interactions in the Universe are governed by four fundamental forces:
Fundamental Forces in the Universe
  • Electromagnetic – the force that acts between electrically charged particles. Electricity, magnetism, and light are all produced by this force and it also has infinite range
Fundamental Forces in the Universe
  • Strong Nuclear Force – the attractive force that binds neutrons and protons together in the cores of atoms and is a short range force – it overwhelms the mutual repulsion of the protons by the electromagnetic force
Fundamental Forces in the Universe
  • Weak Nuclear Force – the force that causes beta (β-) decay (the conversion of a neutron to a proton, an electron and an antineutrino)
  • Like the strong force, the weak force is also short range.
Fundamental Forces in the Universe
  • Gravity - the force of attraction that acts between all mass in the universe and it has infinite range
  • gravity is different than the other forces because at the moment it has no quantum mechanical theory to describe it
  • the best theory of gravity at the moment is Einstein's general theory of relativity, which views gravity as being caused by curvature in space time  
Fundamental Forces in the Universe
  • in the very early universe when temperatures were very high compared with today, the weak, electromagnetic, and strong forces were unified into a single force
  • theories that postulate the unification of the strong, weak, and electromagnetic forces are called Grand Unified Theories (often known by the acronym GUTs)
Fundamental Forces in the Universe
  • there is further speculation, that at even higher temperatures (the Planck Scale) all four forces were unified into a single force
  • theories that add gravity to the mix and try to unify all four fundamental forces into a single force are called Superunified Theories
  • the process of the forces separating from each other is called spontaneous symmetry breaking
origin of the universe
Origin of the Universe
  • in 1948, Russian-American physicist George Gamow published the first model about the universe starting from a hot and dense fireball  the hot Big Bang
  • the Big Bang hypothesis is the most accepted mechanism for the origin of the Universe
  • it suggests that the universe started at an incredibly small volume (smaller than an atom) and rapidly expanded and cooled
history of the big bang19
History of the Big Bang
    • Chronology of the Formation of the Universe
  • Time: 0 seconds:
  • Time and space begin. The universe did not come into existence into any form of pre-existing time and space, but instead created them. At the beginning it appears that time, space, matter, and energy were unified in some form.



Animation shows the expansion history of the Universe by modeling the Universe as a two-dimensional grid of galaxies. The Big Bang, shown as a flash of light, is immediately followed by rapid expansion of the Universe. This expansion then slows down because of the gravitational attraction of the matter in the Universe. As the Universe expands, the repulsive effects of dark energy become important, causing the expansion to accelerate.

what started the big bang
What Started the Big Bang?
  • general relativity implies that our expanding universe began from a singularity
  • a singularity marks a point where the curvature of space-time is infinite, or, in other words, it possesses zero volume and infinite density
  • a singularity must form during the creation of a black hole - when a very massive star reaches the end of its life, its core, which was previously held up by the pressure of the nuclear fusion that was taking place, collapses and all the matter in the core gets crushed out of existence at the singularity
quantum fluctuation
Quantum Fluctuation
  • the most accepted theory for the start of the Big Bang is a quantum fluctuation, which through the mechanism known as inflation grew into all that we know as the universe
  • one of the remarkable insights of Quantum Physics is that particle/anti-particle pairs can be spontaneously created from nothing (i.e., E=mc2)
  • they do not exist very long before being destroyed by collision with their opposite
The Planck Era
  • Time: 0-10-43 seconds; Temperature: 1.4 x 1032 K
  • symmetry breaking in the early Universe results in a series of phase changes (like when ice melts to water or water boils to steam)
  • the decoupling of gravitational force from the unified strong, weak, and electromagnetic forces provides the energy input for phase changes in the Universe
  • the Universe passes from total chaos to the era of spacetime foam and the energy release was used to create spacetime
  • the Universe at the time of the cosmic singularity was a time of pure symmetry, all the forces had equal strength, all the matter particles had the same mass (zero), spacetime was the same everywhere (although all twisted and convolved) - as forces decouple, they lose their symmetry and the Universe becomes more disordered
The separation of forces as a function of energy measured in billions of electron volts (TOE – theory of everything; GUT – grand unification theory)
Grand Unification Epoch
  • Time: 10-43 –10-38 seconds; Temperature: 1032 K
  • strong, weak, and electromagnetic forces are unified
  • rapid inflation of the universe is occurring by an anti-gravitational mechanism
  • atoms and electrons did not exist
  • at this age and temperature, matter and antimatter existed in almost equal amounts, but they were both dominated by the background energy of the universe
inflation epoch
Inflation Epoch
  • Time: 10-37 seconds
  • a period of very rapid inflation, where the universe expanded much more quickly than it had or has since
  • inflation is driven by the energy released from the phase transition when the strong force separates from the electroweak (weak and electromagnetic) forces
  • spacetime and matter separate and a tremendous amount of energy is released
  • inflation produces a universe many times larger than a simple linear expansion
Inflation Epoch
  • Note - the horizon distance is the distance a light ray could have travelled since the big bang explosion
Inflation Epoch

No matter what you start with, if something is expanded by such a big (1035) factor, it will look very flat anyplace you look.

quark epoch
Quark Epoch
  • Time: 10-34 seconds; Temperature: 1027 K; Size 10-25 cm
  • the universe cooled enough for particles that are the building blocks of atoms to form; mostly quarks (up, down, top, bottom, charm, strange), leptons (electrons and neutrinos) and bosons (e.g., photons) in what can be called a Quark soup
  • the creation and annihilation of particles and anti-particles, the universe generated 1ppb excess of matter compared to anti-matter – a difference that allows us to exist today – otherwise the universe would consist of photons and nothing else
nucleosynthetic epoch
Time: 3 min; Temperature 109 K; Size: 1020 cm:

by 100 seconds after the Big Bang, the primary stable particles of matter, i.e., electrons, protons, and neutrons, existed

protons and neutrons were able to combine to form very simple groups like hydrogen (H), but free neutrons are not stable and decayed into protons and electrons

Nucleosynthetic Epoch
  • however, collision of neutrons with protons resulted in nuclei on one proton and one neutron (deuterium), two protons and one neutron (helium - 3He), or two neutrons and two protons (helium - 4He)
recombination epoch the universe becomes transparent
Recombination Epoch:The Universe Becomes Transparent
  • Time: 3 – 4 minutes
  • the universe lit up like the center of a star
  • after 4 minutes, the universe was no longer hot or dense enough to create atomic nuclei
  • Time: 10,000 years:
  • the first major era in the history of the universe in which most of the energy is in the form of radiation
  • as the universe expands, the waves of radiation are stretched and diluted until today, they make up the faint glow of microwaves which bathe the entire universe
Time: 380,000 years; Temperature: 3000 K
  • matter and cosmic radiation (photons) decouple as electrons can now bind to nuclei and form atoms
  • photons were no longer scattered by collisions with charged particles, so for the first time they traveled largely unimpeded through space - this process is called "recombination”
  • this "first light” or “afterglow" is what we now see as Cosmic Microwave Background Radiation (CMB)
Oldest Light in the Universe – the Afterglow of the Big Bang

The microwave light captured in this picture is from 380,000 years after the Big Bang. Colors indicate "warmer" (red) and "cooler" (blue) spots. The oval shape is a projection to display the whole sky.

This is the limit of our view. If we could see beyond this, we could see the Big Bang itself no matter in which direction we looked.

matter epoch modern universe
Matter Epoch: Modern Universe
  • Time: 300 million years; Temperature: 18 K
  • as matter was freed of the radiation pressure that had resisted the contraction of dense clumps, under the attractive influence of gravity, the denser areas of the universe coalesced into stars and galaxies
  • hydrogen burning, etc. occur , supernova explosions occur
  • Time: 8 billion years; Temperature: ~3 K
  • the sun forms within a cloud of gas in a spiral arm of the Milky Way Galaxy
  • a vast disk of gas and debris that swirls around this new star gives birth to planets, moons, and asteroids - Earth is the third planet out
  • Time: 13.7 billion years; Temperature: 2.75 K; Size: 1027 cm
  • present day
observational evidence for the big bang
Observational Evidence for the Big Bang

The evidence for the Big Bang hypothesis is:

  • expansion of the universe
  • cosmic microwave background (CMB) radiation
  • relative abundance of light elements [hydrogen (H), deuterium (D), helium (He), and lithium (Li)]
the expanding universe
The Expanding Universe
  • until about 70 years ago the scientific community thought that the universe was static - neither expanding nor contracting
  • with the development of more powerful telescopes, images and spectra of more distance galaxies could be taken
  • observations of spectral lines of elements ofdistant galaxies and quasars show that these objects are redshifted, meaning that the light emitted from them has been shifted to longer wavelengths
  • furthermore, the dimmer the galaxy, and hence the larger the distance, the more the spectrum was shifted toward the red
  • the relationship between red shift and distance is a fundamental observational inference
measuring the speeds of stars and galaxies
Measuring the Speeds of Stars and Galaxies

Red shift (or Doppler shift):

z is the red shift,

e is the wavelength of light measured in the laboratory at the point of emission,

o is the wavelength of light of a star observed on Earth,

dR/dtis the speed the star is moving, and

c is the speed of light.


Spectrum of a star that is moving away from us might look like (simplified), i.e., the shift is toward the red (longer) wavelengths:



Spectrum of a star that is moving toward us might look like (simplified), i.e., the shift is toward the blue (shorter) wavelength:


The wavelength of light emitted by a moving object is shifted - this effect is called the doppler shift
  • if the object is coming toward you, the light is shifted toward shorter wavelengths, blue shifted
  • if the object is going away from you, the light is shifted toward longer wavelengths, red shifted
  • Blue shifted = higher frequency = higher pitch
  • Red shifted = lower frequency = lower pitch

The amount of shift is bigger if the emitting object is moving faster - we don't normally notice this for light, but it is easy to notice for sound (e.g., think about the sound of an approaching train)

hubble s law
Hubble’s Law
  • Edwin Hubble demonstrated that many nebula in the sky were outside of our own galaxy (Milky Way) and were moving away from us in a specific manner
  • a redshift corresponding to a Doppler shift for the radiation can be measured which is explained by a recessional velocity
  • when the recessional velocities are plotted against the distances to the objects, a linear relationship, known as Hubble's law, is observed:
      • V = H0D
  • where,
    • V is the recessional velocity of the galaxy or other distant object
    • D is the distance to the object and
    • H0 is Hubble's constant, measured to be (70 +2.4/-3.2) km/s/Mpc
two implications of hubble s law
Two Implications of Hubble’s Law
  • we are at the center of an explosion of galaxies, a position which is untenable given the Copernican principle
  • the universe is uniformly expanding everywhere as a unique property of spacetime
further implications
Further Implications

The fact that the galaxies might have existed as a compressed point suggests that in the past the universe was hotter because compression heats up objects (think of an air pump). Also, we imagine that some sort of “explosion” far beyond our current capabilities may have caused the initial expansion of

the universe.

observational evidence for the big bang44
Observational Evidence for the Big Bang

The evidence for the Big Bang hypothesis is:

  • expansion of the universe
  • cosmic microwave background (CMB) radiation
  • relative abundance of hydrogen (H), deuterium (D),
  • helium (He), and lithium (Li)
the cosmic background radiation
The Cosmic Background Radiation
  • astronomers Penzius and Wilson, while working on satellite communications in the early 1960’s discovered an annoying “hiss” on their microwave radio receiver that seemed to come from all directions in the sky
  • they soon recognized that what they were measuring was remnant radiation from the Big Bang
Spectrum of the Cosmic Microwave Background

Measurement of the cosmic background radiation from the NASA COBE (COsmic Background Explorer) satellite

The light that is reaching us has been stretched out as the universe has stretched, so light that was once beyond gamma rays is now reaching us in the form of microwaves. Microwaves are the same as the light we see with our eyes, but stretched out to a longer wavelength.

the cosmic background radiation47
The Cosmic Background Radiation
  • every object gives off radiation - the spectrum of the radiation, or microwave background radiation, is a function of the object’s temperature (think of an oven)
  • Penzius and Wilson’s first measurements indicated that the average temperature of the Universe was 2.7515 K above absolute 0 (= -273.15 oC)
  • if the source of this radiation is beyond the farthest galaxies, then it must be a strongly red-shifted signal of something that originally was at much shorter wavelength, and much higher temperature
But if the Big Bang was an Explosion, it should have been Hot . . .
  • the reason the temperature of the universe is so cold is because it has expanded so much
  • by compressing the universe from its current measured volume, 1 x 1083 cm3, back to a volume of ~ 1 cm3,the temperature would increase to 1028 K!
  • and we currently think the universe was much, much smaller than this when it began
  • thus, we can consider the 2.715 K background to be the “ashes of creation”

The universe cools as it


Age of the Universe
  • given the amount of matter in the cosmos and the temperature of the background radiation, it is possible to calculate the age of the universe
  • the most recent determination of the age of the universe comes from the NASA satellite Wilkinson Microwave Anistropy Probe combined with data from ground-based telescopes
  • the time since the primordial fireball is 13.7 billion years ± 200 million years
observational evidence for the big bang50
Observational Evidence for the Big Bang

The evidence for the Big Bang hypothesis is:

  • expansion of the universe
  • cosmic microwave background (CMB) radiation
  • relative abundance of hydrogen (H), deuterium (D),
  • helium (He), and lithium (Li)
Abundance of Primordial Elements
  • using the Big Bang model it is possible to calculate the concentration of helium-4, helium-3, deuterium and lithium-7 in the universe as ratios to the amount of ordinary hydrogen, H
  • all the abundances depend on a single parameter, the ratio of photons to baryons
  • the ratios predicted (by mass, not by number) are about 0.25 for 4He/H, about 10-3 for 2H/H, about 10-4 for 3He/H and about 10-9 for 7Li/H
  • the measured abundances all agree with those predicted from a single value of the baryon-to-photon ratio, although the agreement is relatively poor for 7Li and 4He, the two elements for which the systematic uncertainties are least understood
  • this is considered strong evidence for the Big Bang, as the theory is the only known explanation for the relative abundances of light elements
what is the ultimate fate of the universe
What is the Ultimate Fate of the Universe?
  • up until 1920, Albert Einstein believed that the universe was static (i.e., neither expanding nor contracting), and he modified his equations in his General Theory of Relativity by including a “cosmological constant” to keep it so(his “greatest blunder”)
  • however, originally general relativity predicted a contracting Universe, since space itself would shrink due to the Universe’s mass and the effect of gravity
  • in the early 1920s, Russian physicist and mathematician Alexander Friedmann became the first person to embrace the idea that the equations of Einstein’s general theory of relativity called for a universe in motion
  • ultimately however, there are many possible solutions to the equations of general relativity, and each solution implies a possible ultimate fate of the universe
fate of the universe
Fate of the Universe
  • observations have shown that the gravitational attraction between galaxies can overcome the expansion of the Universe in localized regions
  • calculations show that gravity can overcome expansion if the current density of the universe exceeds 10-29 gram per cubic centimeter (which is roughly equivalent to a few hundred hydrogen atoms in a volume the size of a closet)
  • for gravity to stop the entire Universe from expanding depends on the total mass density of the Universe
  • the dividing line between eternal expansion and eventual collapse is called the critical density,i.e.,the mass density required for this gravitational pull to equal the kinetic energy of the Universe
        • if mass density < critical density, the Universe will expand forever
        • if mass density > critical density, the Universe will eventually re-collapse into a Big Crunch (i.e., singularity)
Critical Density
  • the mass density parameter, Omega (ΩM), is defined as the average matter density of the universe divided by a critical value of that density (ΩM= density of matter ÷ critical density)
  • the measurement of the ΩMincludes contributions from all sources of matter: normal matter + dark matter (matter that does not emit or reflect enough electromagnetic radiation to be detected directly, but whose presence may be inferred from its gravitational effects on visible matter)
  • the value of ΩM determines the fate of the universe, because it tells us how much matter there is in the universe, and therefore, whether or not there is enough gravity to keep the universe from expanding forever
Fate of the Universe
  • Four possible outcomes for the fate of the universe:
  • Recollapsing Universe: - the expansion will someday halt and reverse - ΩM > 1
  • Critical Universe: will not collapse, but will expand more slowly with time - ΩM = 1
  • Coasting Universe: will expand forever with little slow down - ΩM < 1
  • Accelerating Universe: the expansion will accelerate with time
Fate of the Universe
  • observations and measurements suggest that ΩM < 1 (0.2-0.3), so it seems there is not enough matter to recollapse the universe or even halt the expansion
  • until the late 1990’s, it was still debated whether the universe was critical or coasting (nobody really thought it would recollapse)
  • but as observations slowly mounted on the side of a lightweight, coasting universe, cosmologists became perturbed as they believed that for stability purposes ΩM = 1
  • however, a new set of observations shook cosmology: the universe was not just expanding, but the rate of expansion was accelerating!
Mass Density Parameter and the Expansion Rate
  • without dark energy:
    • gravity is always attractive, so the expansion of the universe is always decelerating!
      • the higher ΩM is, the bigger the deceleration
      • if the universe were empty, it would have the constant expansion, no acceleration or deceleration
      • therefore, if we can measure the expansion speed of the universe at high-redshift (distant past), we can measure the deceleration rate of the universe, and hence the density parameter
  • with dark energy:
    • the case is more complicated… dark energy can be repulsive, therefore, the universe could be accelerating!
White Dwarf Supernovae Show Accelerating Universe

By calibrating a precise brightness-distance relation, astronomers are able to estimate not only the expansion rate of the universe (parameterized by the Hubble Constant), but also the geometry of the universe we live in (parameterized by Omega and Lambda). The large number and great distances to supernovae measured over the past few years have been interpreted as indicating that we live in a previously unexpected universe.

White Dwarf Supernovae Show Accelerating Universe
  • white dwarf supernovae are fainter than predicted for their redshifts
  • this means the galaxies back then are farther away than even an empty (coasting) Universe would predict!
  • therefore, Universal expansion rate must be accelerating?

Hubble diagram displaying distance vs. redshift for Type Ia Supernovae. . The distant supernovae are simply too faint, i.e., too distant to be compatible with a universe filled with matter and radiation only. There has to be a component to the energy density that has accelerated the expansion.

  • Is there a mysterious force pushing on the Universe?
      • it must pervade space
      • provide an isotropic pressure (expand space in all directions
      • the pressure must be non-local
  • astronomers call this force dark energy
Dark Energy
  • the universe is not only made of matter, but also of energy
  • normal” energy (mostly in the form of the cosmic microwave background radiation, but also starlight) is negligible compared to matter
  • dark energy (i.e., vacuum energy) is a repulsive force (antigravity) in the universe that causes the universe to accelerate
Dark Energy
  • the total density parameter (ΩT) includes the contribution from both matter and energy
  • by measuring the acceleration of the universe, we can measure the total amount of dark energy, and the contribution of dark energy to the total density of the universe: ΩT = ΩM + Ωdarkenergy
  • ΩT determines the geometry of the universe
if the total density of the universe exceeds the critical density (ΩT > 1), then the geometry of space is closed and positively curved like the surface of a sphere

in a closed universe without dark energy, gravity eventually stops the expansion of the universe, after which it starts to contract until all matter in the universe collapses to a point, a final singularity termed the "Big Crunch"

if the universe has a large amount of dark energy, then the expansion of the universe can continue forever - even if ΩT > 1

Closed Universe (ΩT > 1)




  • spherical (closed) geometry
  • saddle-shaped (open) geometry
  • flat (critical) geometry
The Big Crunch

In a Universe without dark energy or where it fades away eventually leads to a slowing of the expansion of the Universe, followed by a recollapse, the so-called "big crunch". In some ways this scenario resembles the Big Bang in reverse.

if the density of the universe is less than the critical density (ΩT<1), then the geometry of space is open and negatively curved like the surface of a saddle

even without dark energy, a negatively curved universe expands forever, with gravity barely slowing the rate of expansion

with dark energy, the expansion not only continues, but accelerates

Open Universe (ΩT<1)




  • spherical (closed) geometry
  • saddle-shaped (open) geometry
  • flat (critical) geometry
The Big Rip

If dark energy increases with time, the Universe may experience a catastrophic, runaway expansion. Within about a 100 billion years every galaxy, star and atom in the Universe would be ripped apart.

if the density of the universe exactly equals the critical density (ΩT=1), then the geometry of the universe is flat like a sheet of paper

without dark energy, a flat universe expands forever but at a continually decelerating rate, the rate of expansion asymptotically approaching zero

inflation predicts a flat universe

with dark energy, the expansion rate of the universe initially slows down, due to the effect of gravity, but eventually increases

Flat Universe (ΩT=1)




  • spherical (closed) geometry
  • saddle-shaped (open) geometry
  • flat (critical) geometry
Continued Expansion

If dark energy is constant, consistent with Albert Einstein's suggestion, then the expansion of the Universe should continue accelerating until in a hundred billion years or so, only a tiny fraction of the known galaxies in the Universe will be observable

The Fate of the Universe
  • modern observation shows:
    • the total density ΩT = 1: the universe’s geometry is flat
    • the mass density ΩM ~ 0.3, the universe is light-weighted, and will expand forever
    • the dark energy density Ωdark energy ~0.7, the universe is dominated by dark energy, and is accelerating