The heavens declare the glory of God; the skies proclaim the work of his hands. Day after day they pour forth speech; night after night they

display knowledge. There is no speech or language where their

voice is not heard.”

Psalm 19:1-3 NIV

1

“When I consider your heavens,

the work of your fingers,

the moon and the stars,

which you have set in place,

what is man that you are mindful of him,

the son of man that you care for him?”

Psalm 8:3-4 NIV

“The Most Incomprehensible Thing

About

the Universe is that it is

Comprehensible”Albert Einstein

COSMOLOGY

Three Simple Questions..........

What is the nature of the Universe?

What is its past?

What is its future?

As long as men have been looking up to the skies at night and

observing the panorama of the heavens, some men have been wondering about the origin and

nature of the universe.

COSMOLOGY

• .......the study of the origin, structure, and evolution of the

Universe

– 1914 Vesto Slipher was studying rotation of the Andromeda Nebula using the Doppler Effect• could not observe any rotation• did observe a large Doppler Shift

corresponding to a “blueshift equiv. to 700,000 mph

– Observed a total of 12 “nebulae” or “fuzzy clouds”• found all except Andromeda exhibited

redshifts many receding from the earth at very high speeds

•Modern Cosmology began in the early 1900’s

– Edwin Hubble was grad student in audience and became interested in the project• Hubble was a ex-lawyer turned astronomer

– By 1925 Slipher had measured 40 nebulae and found redshifts much more common than blueshifts

– At that time it was not known exactly what the “fuzzy” objects like Andromeda were• local objects...in our galaxy?• extra-galactic objects...outside our galaxy?

•Slipher reported on work at American Astronomical Society meeting

General Relativity

• 1915 Albert Einstein introduced the ideas of General relativity– accelerations in space-time cannot be

distinguished from gravitation attraction

– gravitational forces are explainable as a curvature of space-time due to presence of mass

– bending of light by strong gravitational fields

– movement of perihelion point of Mercury– gravitational redshift of spectral lines

Einstein’s GR made 3 testable predictions

•All 3 have been experimentally confirmed

–first 2 by early 1920’s

– his solutions were unstable and dynamic, i.e. they implied that the universe is changing

• Einstein believe the universe was static– added a “fudge-factor” to his

equations to make the answer static

•Einstein used General relativity to solve for the structure of space-time for the universe

Friedmann showed there were 3 stable solns and all were dynamic– each different soln was characterized

by a unique curvature of space• spherically curved• hyperbolically curved• flat

1922 Russian mathematician Alexander Friedmann disc. error in Einstein’s calcs. (he had divided by zero at one point)

• 1917 Edwin Hubble began work at Palomar observatory and with help of Milton Humason (acknowledged as the best observational astronomer in the world - and totally self-taught!) expanded Slipher’s measurements and began to try to interprete their meaning

•1920 Curtis-Shapley debate at the National Academy of Sciences over the nature of Nebulae...(inconclusive!)

The nature of Slipher’s “fuzzy objects” or nebulae was being vigorously debated by astronomers……were they galactic or extra-galactic?

• At first even Hubble could not accept what an application of Henrietta Leavitt’s period luminosity relation for Cepheids implied....– a distance MUCH larger than any distance

estimated for other “nebulous” objects

•Using Palomar telescope, Hubble & Humason were able to resolve individual Cepheid Variables in Andromeda Nebula

Cepheid Variables in the Andromeda Galaxy......... identified by red arrows

Cepheid Variables are very large and bright stars with variable light output (due to pulsations in size). They are identifiable by their characteristic light curve.

Period-Luminosity Relation for Cepheid Variable Stars

Knowing the period gives one a measure of the star’s luminosity (actual total energy output of the star) and comparing this with its perceived brightness (from Earth), one can use the inverse square law and estimate the distance to the object.

Using the Period-Luminosity relation for Cepheids, they determined that the nebula was at least 2.2 million light years away and therefore EXTRAGALACTIC!

Hubble soon discovered several Cepheid variables all implying the same result...

This showed that many of the “fuzzy” nebulae were actually galaxies like our own

– All of the distant galaxies in all directions were receding from the earth

– the velocity of recession was directly proportional to the distance of the galaxy

•Hubble-Humason examined several dozen galaxies within 7 Million light years in which Cepheids could be resolved, and made an Astonishing discovery!

Redshift Data for 5 Representative Galaxies at increasingly larger distances

Hubble’s Original Data

• Hubble’s work was experimental confirmation of the theoretical predictions of General Relativity– the universe was expanding– the expansion was isotropic (same in

all directions)

This is known as the Cosmological Red Shift

it is space-time itself that expands and NOT the objects in it

Doppler shift compared to the Cosmological redshift

Raisin Bread Analogyor Balloon Analogy

Cosmological Redshift

Expanding Cake Analogy

Just as all the chocolate chips move apart as the cake rises, all the superclusters of galaxies recede from each other as the universe expands.

Big-Bang

• Once Hubble’s Law was established– simple matter to run the expansion

backwards and conclude that all galaxies were originally at same point in space-time

– in fact all matter! the universe itself!, and space and time originated at this point

– point in space-time at which the universe began is known as the Big-Bang

Age of Universe

• Since Hubble’s Law can be written– velocity of recession = (constant) x

distance• the constant is Hubble’s Constant H0

• i.e. v = (H0 )(d)

• Running the expansion backwards• H0 = velocity/distance

• 1/H0 = distance/velocity = time

– the “time” since the expansion began, i.e. the age of the universe

• Using a value of H0 of 75 km/sec per megaparces or about 24 km/sec per million light years gives a time of– about 13 x 109 or 13 billion years

The actual value of Hubble’s Constant has been a subject to intense debate with values as high as 100 km/sec/Mpc and as low as 50 km/sec/Mpc advocated.

this gives age of universe between about 9 to 17 billion years

Most of the very latest data presented within the last year or so has indicated that a value of 65 - 75 km/sec/Mpc, with a avlue close to 70 being favored.This gives a Hubble Age of about 13 Billion years.

Observable Universe

• As the universe expands, looking out in distance is thus equivalent to looking back in time– a telescope is a sort of ‘time machine’

• The observable limit of the universe is the distance that light could have traveled since the beginning of the universe– for value of 75 km/sec/Mpc this is 13 Bly

The Observable Universe

– Many astronomers did not accept the idea of a dynamic, expanding universe

– objections were primarily philosophical•Big-bang implies an origin•an eternal universe was desirable

– Plausible alternative was the Steady-State universe

Objections to the Big-Bang Universe

Fred Hoyle (originator of the term big-bang!), Thomas Gold, and Hermann Bondicould explain expansion and keep an eternal universe with no origin by allowing matter to be created at a rate to keep density of universe constant

Steady-State theory

This required violating the Law of Conservation of Energy

Steady State Universe

Enough matter appears to keep average density constant

Steady State Universe

Violation of conservation of energy would be small - less than 1 hydrogen atom per cubic meter per 50 million years

Much too small to observe!

Cosmic Microwave Background

• 1946 Physicists Ralph Alpher and George Gamov worked on the creation of elements in a big-bang (nucleosynthesis)– disc. there should be a very cool

residual radiation left over from the Big-Bang

– this diffuse radiation should be a blackbody radiation at about 5 K

The energy radiated by a Blackbody takes a special form when the relative brightness (or strength) of the radiation is graphed as a function of the wavelength

• Calibrating antenna to eliminate noise

• With antenna set at 7.35 cm (4080 MHz)– far from any galactic radio emissions– kept getting peculiar static

• const regardless of time of day, season of year, direction in the sky

1964-65 Bell Labs scientists Arno Penzias & Robert Wilson were working on a microwave horn antenna for satellite communication

• recalibrated antenna• cooled their detectors• removed nesting pigeons from

horn• cleaned antenna• could not eliminate the static

“Noise” in their Antenna

• Realized they were seeing this residual radiation remnant from the Big-Bang– Cosmic Microwave Background Radiation

• If a blackbody curve is assumed – 7.35 cm corresponds to 3.5 Kelvin

• 1976 Penzias & Wilson received a Nobel Prize

Contacted a group at Princeton University who were working on a design for a system to detect the residual radiation

• Very little of the 3 K background radiation can penetrate the atmosphere– difficult to measure radiation curve– used balloons, rockets, aircraft, etc.

•1989 NASA launched the Cosmic Background Explorer (COBE) satellite to measure this radiation

Cosmic Background Explorer (COBE) Satellite

In Search of Primordial Photons

The balloon-carried telescope BOOMERANG

Blackbody Spectrum of COBE Satellite and fit to a 2.73 K Curve

All sky COBE data : variations of 1 part in 10000

Observe the uniformity across the universe.

• Cosmic Background Radiation was unexplainable in a steady-state universe– death blow to that theory

Currently only variations of Big-Bang cosmologies are widely accepted

COBE data is accurate enough to measure the motion of the earth relative to the background radiation by analyzing the data to 1 part in 10,000 variation

COBE Dipole: Speeding Through the Universe Credit: NASA, COBE, DMR, Four-Year Sky Map

Astronomy Picture of the Day, February 5, 1996

A more detailed analysis of COBE data with the all sky uniform data and the dipole data subtracted out, yields a view of the density variations in the early universe as shown on the next slide.These variations shown are at the 1 part per 100,000 level

A map of the brightness of the cosmic microwave background made by the cosmic background explorer (COBE) satellite. At < 1 part per 10,000 level Notice the patchiness of the brightness. Each pink patch may represent a "lump" of matter from which groups of galaxies ultimately grew. The patches were approximately one half billion light years across when they emitted the radiation. (NASA GSFC and the COBE Science Working Group.)

June 30,2001 NASA launched the Wilkinson Microwave Anisotropy Probe or WMAP to gain more detailed data on the Microwave Background Radiation (CMB). With better detectors and much longer operating life (mission runs until 2009) WMAP has revolutionized the analysis of the CMB

Wilkinson Microwave Anisotropy Probe (WMAP) satellite, launched in 2001

WMAP data showing fluctuation in the CBR

ΔT range on this plot is +/- 200μK or +/- 0.0002 K

Big-Bang Cosmologies

• The only commonly accepted cosmologies to date are some form of “big bang”

• “Standard” Big Bang only model until 1980s

• There are problems with all big bang models and especially with the “standard” model

Problems with the Standard Model

• The very tiny variations in the background radiation seen by COBE imply that all parts of the universe are at equilibrium– variations in BB temperature < 1 part

in 10,000– for objects to be in thermal

equilibrium, they must have been in contact or close interaction

how can this uniformity exist?opposite sides of universe 26 Bly apart. too far apart to have been in contact during the lifetime of the universe..could not be at same temperature unless in contact at some time!HORIZON PROBLEM

Flatness Problem

• In standard big bang models, current flatness of universe is a problem– today universe is VERY flat

• Requires a density during initial stages of big bang with a density within 50 decimal places of the critical density

• this is highly unlikely!

• One solution to these “problems” is called the “inflationary universe”

as universe developed from big-bang it was initially extremely small - so all parts were in contact-early in life of universe it experienced an “inflationary epoch” where universe suddenly ballooned to billions of times its original size-all parts of universe were in thermal

contact before inflation, so BB temps are similar

The Inflationary Model

Inflation solves flatness problem

• Newborn universe (before inflation) could have been highly curved

• inflation expands the size of universe so much ( about 1050 times), that any curvature left is too small to see today– consider how earth looks flat

After Inflation - Universe Looks Flat

In general the WMAP data supports an inflationary universe as well as a cosmological constant.

The Results!

The Hubble Constant Ho = 71 +4,-3 km/sec/Mpc

Age of the Universe 13.2 0.2 Billion years

Constituents of the Universe

baryonic (normal) Matter 4%

cold dark matter 23%

dark energy 73%

First stars born only 200 million years after Big Bang

What We Can See!

We Can Detect its Gravitational Effects

Currently detectable only by acceleration effects of distant supernovae & WMAP data

Brief History of Matter

• Four Fundamental Forces in Nature– Gravitational– Electromagnetic– Strong Nuclear– Weak Nuclear

• “unified field” theories– all 4 fund. forces were originally 1

force• (very high temps & energies)

– as universe expands and “cools” each manifestation “freezes out”

– produces the 4 forces we see today

Study of the origin and structure of matter and the universe is closely tied to the study of particle physics

• Experimental evidence for the “electro-weak” force in very high energy particle experiments– electromagnetic & weak force unified

• Some evidence for unification of strong nuclear & electroweak

• incorporating gravity remains an unsolved problem

Force History of the Universe

Time Scale of Big Bang• 0 - 10-43 sec PLANCK time

– all forces unified....1033 K quantum “soup”

• Planck time– gravity “freezes out”

• becomes a force separate from other 3

• 10-35 to 10-24 sec INFLATIONARY EPOCH– strong nuclear force “freezes out”– inflation begins

• 10-6 sec CONFINEMENT– individual protons & neutrons can

exist

• 10+13 sec TRANSPARENT UNIVERSE– universe become transparent to

photons which spread throughout the universe forming the cosmic background radiation seen today

• 10-12 sec–weak nuclear “freezes out” from the EM force

Matter created from energy

• in first few minutes of big-bang there was enough energy to create (via a process like pair-production)– all the hydrogen– most of the helium– trace amounts of lithium & beryllium

• all other elements produced via stellar evolution

Pair Production particle annihilation (particle-antiparticle pair)

Conversion of Energy into Matter

gamma ray photon creates an electron-positron pair in a bubble chamber

(paths are bent due to a magnetic field in the chamber

Radiation & Matter Eras of Universe

• first 300,000 years was Radiation Era– universe was shimmering sea of high

energy opaque plasma– to much energy to permit protons &

neutron to combine and form atoms– “primordial fireball”

– not enough energy to prevent protons and electrons from combining to form hydrogen

– almost all protons used up in hydrogen gas which is transparent

– universe becomes transparent to light (photons)

– escaping photons form the cosmic background radiation seen today• cooled to about 3 K by the present

At 300,000 years, temperature of plasma drops to less than 3000 K and the “matter-dominated “ universe begins

Cosmic Background Radiation is Oldest Thing That Could be Seen in

the Universe• Since universe was opaque before

the “era of recombination” at 300,000 years, we cannot ever see back beyond this time

According to the current cosmological models, what

is the destiny of the universe?

Mass is the main factor!

• For the Universe, total mass is impossible to measure

• Cosmological theories are therefore expressed in terms of Mass Density– kilograms per cubic meter– critical density = 2.4 x 10-26 kg/m3

• depends on value of H0 (75 km/sec/Mpc)

Gravity is the Dominant Force in Universe

• Of four fundamental forces only gravity acts over long distances in universe and cannot be cancelled out (no antigravity)

• gravity pulls back on the expanding universe

• strength of the pull determines what happens to the universe

• expand forever• expand at a minimal rate• expand, stop and then re-contract

Universe can:

• If density of universe is low (less than critical density)– gravity too weak to stop expansion

and universe expands forever• If density of universe is high (more

than critical density)– gravity stops the expansion and pulls

the superclusters back together

• Since gravity always acts during expansion - pulling on expanding regions

gravity slows down the rate of expansion

• If the mass density is equal to the critical density– the superclusters will just barely

manage to keep moving apart

End result depends on

mass density of the universe 0

value of Hubble’s constant H0

• The effect of gravity should theoretically be seen in a deviation of Hubble’s Law from a linear relationship (straight line)– the value of H0 was different in the

past

• Since looking out in distance = looking back in time– if can measure H0 for increasingly

distant clusters, then could know H0 as changes with time

Deceleration Parameter

• Cosmologists use parameter q0 called the deceleration parameter in their models to describe this phenomenon– q0 = 0 means an empty universe

containing no matter at all• such a universe expands forever at a

constant rate

– q0 = 1/2 means a universe at critical density• universe just barely manages to expand

forever

• For q0 between 0 and 1/2 the universe is UNBOUNDED

• If q0 is more than 1/2 – the universe stops expanding at some

point and begins to collapse in to a BIG CRUNCH

Measuring q0 (equivalent to. H0 as function of time)

• Extremely difficult to measure– significant deceleration effects only

occur beyond a billion light years out– uncertainties in data at these

distances make reliable values currently impossible

Hubble’s Law and Deceleration Parameter for Extremely Distant Galaxies

Current Results

• Best current data indicate a value of q0 near a value of 1/2 with the best data being less than 1/2– this would mean a marginally

unbounded universe

Curvature of Space-Time

• The value of the mass density of the universe or equivalently the deceleration parameter also determined which of Friedmann’s solutions apply– i.e. what is the shape of space-time

q0 > 1/2

spherical curvature

density > critical value

q0 = 1/2

flat space

density =critical value

q0 < 1/2

hyperbolic curvature

density<critical value

Scientifically What is Ultimate Destiny of the Universe

• Best values of density, q0 , and H0, and all other data indicate too little matter (even including estimates of dark matter) to close the universe

• In reality WE DO NOT KNOW!– Universe will expand forever

Results in the last 5 years from measurements of distant supernovae have given a startling conclusion:

The universe’s expansion has accelerated

This is contrary to the expected result of gravity gradually slowing the expansion down

Further microwave background studies seem to confirm the result that the universe overall is essentially flat...i.e. at critical density

Dimmer Distant Supernova

•These HST images show the galaxy in which the supernova SN 1997ff occurred. •This supernova was dimmer than expected. •The distance to it is greater than it would be if the universe had been continually slowing down. •An outward force is acting over vast distances in the universe.

Dimmer Distant Supernova

One possible explanation of these results has cosmologists re-introducing Einstein’s Cosmological constant which produces a force partially balancing the attraction of gravity in the universe as a whole.

In 2002 the MAP (Microwave Anisotropy Probe) group released their results for the first year of data from the MAP spacecraft in orbit about one of the L2 positions in Earth’s orbit.

The Results!

The Hubble Constant Ho = 71 +4,-3 km/sec/Mpc

Age of the Universe 13.2 0.2 Billion years

Constituents of the Universe

baryonic (normal) Matter 4%

cold dark matter 23%

dark energy 73%

First stars born only 200 million years after Big Bang

Recombination era began 380,000 years after the Big Bang

The universe is perfectly flat

Not enough matter to close the universe - it will expand forever

Polarization of the CBR implies inflation models

Dark energy results support a Cosmological constant term rather than quintesence

What IS the destiny of the Universe?

• We DO KNOW!– at some point God will pull the plug!– Universe will cease to exist

• Col. 1:16-17 (NASB)– “For in him all things were created,

both in heaven and on earth, visible and invisible ............And he is before all things, and in Him all things hold together”

And that of course is…..

THE END