The Origin and Evolution of the Universe

Don't Panic

Sections

Energy & Entropy
Early History of Cosmology
The Discovery of Galaxies
The Expanding Universe
Observing the Expanding Universe
The Accelerating Universe
The Big Bang
The Large Scale Structure
The Fate of the Observable Universe
Inflation Cosmology
The Multiverse

https://www.nhn.ou.edu/~jeffery/course/c_cosmos/cos.html

Energy & Entropy

energy

entropy

Energy is the universal conserved essence of structure---a reasonable suggestion for a one-line definition.
1. If you have a structure you have energy: matter (as E=mc**2 tells us), motion (kinetic energy), force fields (e.g., the electromagnetic field), electromagnetic radiation, and many other often overlapping categories.
2. Structures have many other characteristics, but they all have energy.
3. There are many different forms of energy and they are interconvertible---but not necessarily easily.
4. Forces cause the conversions---gravity, the electric force, etc.
5. If you have energy, it can be converted to do things.
6. But since it is conserved---the conservation of energy---there are limitations.
  If you don't have enough energy to do something, it can't be done.
7. The universe is full of evolving structures, and so of changing forms of energy.
8. You can tell almost any story IN PART as one of conversions of energy.
  You "follow the energy".
  For example, the microcosm:
  Basic overview of energy and human life.
9. This lecture is often a story of energy conversions---but often only implicitly.
Entropy is a quantified measure of disorder.
1. Random process tend to cause disorder to increase---think of your living room being reduced to total squalor.
2. At the microscopic level of atoms, molecules, etc., this disorder can be quantified by formulae as entropy.
  In a non-quantitative, non-formulaic way, there is also macroscopic "entropy".
3. Entropy will always increases in a closed system---if counted in the right way which is sometimes tricky---until it reaches a maximum which we call thermodynamic equilibrium.
  This rule is the 2nd law of thermodynamics.
4. As an example of increasing entropy consider free expansion:
  This free (or Joule) expansion is adiathermal (no heat flow) but it is not quasi-static neither is it reversible.
  You can reverse the situation, but only with outside help.
  The system will not spontaneously reverse.
5. Maximum entropy (i.e., thermodynamic equilibrium) for a closed system is a timeless, lifeless state.
  Timeless at the macro-level. At the micro-level, atoms continue to jiggle around.
6. Biota and the biosphere are NOT closed systems.
  Low entropy energy comes into these systems and leaves as high entropy energy.
7. Complexity is a different dimension from entropy.
  Both very low and high entropy states can be very simple.
  1. Light from the Sun coming into the biosphere is high entropy and the infrared light that leaves the biosphere is low entropy.
    Both are rather simple.
    But the biosphere is very complex in between.
    Let's have quick look at the Earth's energy budget.
    The biosphere is sustained by this budget.
  2. The observable universe, it seems, started in a low entropy simple state and will end in a high entropy simple state.
    In between, we have complexity: galaxies, stars, planets, us.
  Complex force interactions allow complex systems like atoms, nuclei, the biosphere, us.
8. The 2nd law of thermodynamics (i.e., the law of increasing of entropy) is sometimes called the arrow of time.
  It tells why many things, not all things, unfold in the order they do---eggs break on the floor and don't spontaneously reassemble themselves, etc.
9. The 2nd law of thermodynamics directs evolution of the observable universe.
  This factor underlies this lecture, but usually only implicitly.
The header image explicated.

Early History of Cosmology

The Discovery of Galaxies

So we had a universe of stars from the 16th century on.
But what was beyond the stars? Anything? Nothing?
Some thought there could be other star systems, other Milk Ways.
Maybe they were the nebulae.
Sketch made by Lord Rosse (William Parsons, 3rd Earl of Rosse) of the Whirlpool Galaxy in 1845
The Whirlpool Galaxy (Spiral Galaxy M51, NGC 5194), a classic spiral galaxy located in the Canes Venatici constellation, and its companion NGC 5195.
Edwin Hubble (1889--1953)
1. The good old days when a man could smoke at his desk.
2. Hubble determined that some nebulae were other galaxies by resolving stars in some of the nebulae and measuring distances to some nebulae.
3. He showed some nebulae were far outside of the Milky Way, and so were vast star systems.
4. The closest were of order 1 Mpc away.
5. 1 Mpc ≅ 3 million light-years (ly)
This is the 100 inch (2.5 M.) Hooker Telescope at the Mount Wilson Observatory in Los Angeles County, California.
Comparison of nominal sizes of primary mirrors of notable optical telescopes. Dotted lines show mirrors with equivalent light-gathering ability.
This deep image of the Virgo Cluster obtained by Chris Mihos and his colleagues using the Burrell Schmidt telescope shows the diffuse light between the galaxies belonging to the cluster. North is up, east to the left. The dark spots indicate where bright foreground stars were removed from the image. Messier 87 is the largest galaxy in the picture (lower left).
Map of the Orion Arm of the Milky Way: Artist's conception
Artist's conception of the Milky Way galaxy as seen from far Galactic North (in Coma Berenices) by NASA/JPL-Caltech/R. Hurt [2] annotated with arms (colour-coded according to Milky Way article) as well as distances from the Solar System and galactic longitude with corresponding constellation.
Hubble Deep Field (full mosaic) released by NASA on January 15, 1996.

The Expanding Universe

Observing the Expanding Universe

Schematic animation of a continuous beam of light being dispersed by a prism

Group Activity:

Form groups of 2 or 3---NOT more---and tackle Activity Questions: Cosmology problems 1--16.

Discuss each problem and come to a group answer.

Let's work for 5--10 minutes.

The winners get chocolates.

See Solution.

End of activity period End of activity period.

Caption: "This image shows a stack of chocolate, including milk chocolate, nut chocolate, dark chocolate, and white chocolate."

Credit/Permission: © Andre Karwath (AKA User:Aka) / Creative Commons CC BY-SA 2.5.

Image linked to Wikipedia.

The Accelerating Universe

Our light cone for the observable universe embedded in our pocket universe according to the concordance model.

The Big Bang

Hubble Deep Field (full mosaic) released by NASA on January 15, 1996.
Hubble Ultra Deep Field diagram. It shows the 1995 Hubble Deep Field and the Hubble Ultra Deep Field from 2003 and 2009.
Graphical timeline of the Big Bang
The main nuclear reaction chains for Big Bang nucleosynthesis
Big Bang Nucleosynthesis: 2 useful plots a bottom of page (1) the formation with time (2) the fit to the observations.
Periodic table showing origin of elements,
Recombination epoch 380,000 years after the Big Bang at z = 1100 and T ∼ 3000 K.
The monopole spectrum of the Cosmic Microwave Background = CMB T = 2.72548(57) K.
Five basic evidences for the Big Bang:
1. The expanding universe.
2. Big Bang nucleosynthesis accounts for the light elements.
3. The cosmic microwave background (CMB).
4. The fluctuations in the CMB suggest primordial density fluctuations that are adequate to account for the large-scale structure of the universe. Lots of other ingredients are needed, of course, to determine the large-scale structure.
5. Oldest Stars with ages of > ∼ 13.6 Gyr are not older than the age of the observable universe.
The Big Bang theory explains these evidences.
No other cogent theory does.
If the Big Bang theory were just plain wrong, it would be astonishing.

The Large Scale Structure

The Fate of the Observable Universe

What comes after the present for the observable universe?
Hm. Tricky.
Well star formation and illumination is turning off.
They probably peaked of order 10 Gyr ago???.
They are certainly in decline now.
See Driver et al. 2015 "Galaxy And Mass Assembly (GAMA): Panchromatic Data Release (far-UV --- far-IR) and the low-z energy budget" p. 25 for the summary image.
The illumination from stars and galaxies has decreased by ∼ 40 % since lookback time ∼ 2.3 Gyr.
Why?
Some fraction of interstellar medium (ISM) (mostly hydrogen and helium) is getting permanently locked up into compact remnants (white dwarfs, neutron stars, and black holes) in every generation of star formation and is NOT being fully replaced by inflows from the intergalactic medium (IGM).
The universal expansion is probably slowing the inflow of IGM which is also getting used up through there is a lot of it---about 9 times more than in stars (see Wikipedia: Pie Chart of Mass-Eenrgy Distribution of the Universe).
But it will be a long time to the end of the stars---see below.
What is the universal expansion leading too.
Well in the accelerating universe picture it's loneliness.
If the current rate of acceleration is extrapolated to the far future ∼ 150 Gyr, the gravitationally bound systems---like the Local Group of galaxies---will lose sight of each other (see Wikipedia: Future of an expanding universe: Coalescence of Local Group and galaxies outside the Local Group are no longer accessible).
These systems will have their particle horizons shrink to essentially themselves.
Space will be expanding so fast that light signals will be carried away faster than they can travel.
The gravitationally bound systems---like the Local Group---will probably coalesce into one big elliptical galaxy each.
This coalescence will probably be on the time scale of 100--1000 Gyr in the future.
With the stars gradually turning off, space will grow dark and cold---this happy fate is called the heat death of the universe---a state of maximum entropy.
For the time scales, see Wikipedia: Graphical timeline from Big Bang to Heat Death
Maybe the multiverse will save us from the heat death of the universe.
It could be that the multiverse is infinite and eternal.
The multiverse could be fundamentally an open system with no upper limit on entropy.

Inflation Cosmology

Cosmic evolution illustrated.
Inflaton field φ
Growth of the observable universe radius with inflation
Illustration of the horizon problem
Diagrams of three possible geometries of the universe: closed, open and flat from top to bottom
The flatness problem is illustrated by the following graph: Graph of the density Omega of the universe in units of the critical density as a function of cosmic time (not to scale)
The detailed, all-sky picture of the infant universe created from nine years of WMAP data. The image reveals 13.77 billion year old temperature fluctuations (shown as color differences) that correspond to the seeds that grew to become the galaxies
WMAP 3-year Power spectrum of CMB compared to recent measurements of BOOMERanG , CBI, VSA and ACBAR.
So there is some evidence for inflation, but it remains a highly speculative theory since, among other things, we don't know what the inflaton is.
There is at least one counter theory that has been discussed: the ekpyrotic universe.

The Multiverse

Eternal Inflation
We will continue our cosmological research remembering the words of Blaise Pascal (1623--1622):