Lecture 2. Astronomy and Cosmology

Ancient (Dualist, Geocentric) Cosmology

Solar System

Stars and Galaxies

“Big Bang” Cosmology

Nucleosythesis: where do chemical elements come from?

Star, Galaxy Formation

New Cosmology: after 1980, 1998

Did the Universe originate at random?

Ancient Egyptian Tradition

Pharaonic Egypt Tradition

Painted mural in tomb (~1500 BC)

Biblical Tradition

Giusto de Menabuoi, La creazione del mondo, Fresco (Padua), ca. 1376.

Hieronymus Bosch, Garden of Earthly Delights, Closed Triptych, ca. 1500

Hieronymus Bosch, Garden of Earthly Delights, central panel

“A pilgrim discovers where the Sky and the Earth touch”

Date?

Flat Cosmology

Good

Evil

Of course we all know that this “obvious” view is scientifically incorrect,but we often act as if it were the truth, in accordance with morality.

Robert Fludd, ca. 1618Copernicus, ca. 1514

TWO WORLD SYSTEMS

Commentariolus

Earth in the Universe

The Earth seen from Space

14

Earth rise on the Moon

Comet Churyumov-Gerassimenko seen from Rosetta spacecraft.

It is ~500 million km away and is traveling at ~60,000 km/hour.It is about 4 km in diameter.

Philae landed on comet on Nov 14, 2014 after 10-year journey, planned by European Space Agency. Came to rest after 3 bounces.

Our Sun: an average star

About 8 light-minutes away, by light, ~5 billion years left to live. Mass about 300,000 that of earth.

Venus transits in front of SunVenus

Magnetic storm (solar spots)

Relative sizes of stars in Milky Way

Pinwheel Galaxy, 21 million light-years away, 170 thousand ly. in diameter,~100 billion stars.

!

December 8, 2009

Hubble sees to edge of universeAstronomers have used the Hubble space telescope to discover the faintest and most distant galaxies ever seen. A new camera fitted to the orbiting observatory in May by shuttle astronauts has captured dim red "star cities" that formed only 600-900 million years after the Big Bang. The universe is thought to be around 14 billion years old and this new glimpse of them is a look back in time more than 13 billion years.

Galaxies set distance records:

Nature, Oct. 2010

Most distant object ever seen, 13.1 billion light years away, in “Hubble Extra Deep Field” region of space (photo taken in 100 hours viewing time).

Probably contains about one billion stars; formed within 600 million years after the Big Bang (13.78 billion years ago).

Very early, small Galaxy, formed within 480 million years after BB. Contains massive H-rich blue stars.

Now new record (Jan. 2011):

View of some of the “dishes”in the Atacama desert, the driest place on earth.

In the background: the Milky Wayand its central portion.

Joint Europe, US, Japan Collaboration,of banks of 7 and 12 m correlated telescopes acting as one super-teles-cope at 5000 (~17000 ft) in Chileandesert.

Sixty-six dishes planned at completion.Operation began in 2013.

Alma(Atacama Large Millimeter Array)

Albert Einstein (1879-1955)

1905: Special Relativity

1915: General Relativity

1917: Introduction of Cosmological Constant

1919: Experimental Confirmation (Eddington)

Edwin Hubble (1889-1953)

1924: “Nebulae” lie outside our Milky Way

1929: Galaxies are moving away from us at speed proportional to their distance

But how did it all begin?

Some of the protagonists and highlights:

Universal Expansion

“Hubble’s law” gives rise to:

Originators of the Big Bang Theory

Fundamental publications:

Friedmann: Zeitschrift für Physik, 1922 Lemaître: Annales de la Société Scientifique de Bruxelles, 1927;Translation: Royal Astronomical Society, London, 1931.

Conclusion of Lemaître’s 1927 6-page paper in a translation requested by Sir Arthur Eddington, which appeared in the Monthly Notices of the Royal Astronomical Society, March 1931.

Robert Millikan , Georges Lemaître , Albert Einstein

Pasadena, CA (1933)

Georges Lemaître, manuscript (1927), Louvain

... but not all agreed...

-- Fred Hoyle considered Lemaître’s hypothesis as a Papist plot to reintroduce an act of creation into cosmological theory. Hoyle accused Lemaître of wanting to start the Universe with a “Big Bang”. Hoyle proposed instead the idea of continuous creation.

-- Lemaître caught it from both sides: he was too theological for the atheist Hoyle, too materialistic for the fundamentalists; but loudly praised by the Pope.

-- Pope Pius XII was overjoyed that a Catholic Priest had proposed an “instant of creation”. But Lemaître rejected the Pope’s interpretation. The Pope backed down!

The Cosmic Microwave Background Radiation (CMB)vindicates Lemaître entirely.

-- Proof: serendipitous discovery by Penzias and Wilson (1964) of the CMB, then COBE (Cosmic Background Explorer, George Smoot et al., 1992), then WMAP (Wilkinson Microwave Anisotropy Probe; John Mather et al., 2003), then Planck (2014).

-- The BB generated intense EM radiation. As the Universe expanded, it cooled, becoming transparent about 380,000 years after BB, and light could propagate. Temperature is now 3 deg K (or -270 deg. C), in the microwave range.

-- Temperature of CMB varies from place to place by 1/100,000 of a degree. COBE, WMAP and Planck measure this variation: one deduces that the universe is practically flat, is ~13.79 GY old, came into being with a Big Bang and determines values of the Universe parameters.

-- Lemaître was apprised of the Penzias & Wilson results (in 1964) just before he died (in 1966).

COBE

WMAP

1992

2003

Planck CMB DataFrom European Space Agency, March 2013

Resolution is one-millionth of a degree!Determines Universe parameters: Temperature, Density, Age, Cosmological Constant,...

How was Matter “Created”?

Lemaître: in BB, from the “Primordial Atom”?

“The Beginning of the World from the point of view of Quantum Theory”, Nature, May 1931 [1/2 page!]

Not correct: Where did the Primordial Atom come from?

Actually, from Big Bang Nucleosynthesis: H, He, + very small amounts of Li, Be, B.

Followed by: Stellar Nucleosynthesis:Equilibrium: up to Fe

Non-equilibrium: beyond Fe{

Big Bang Nucleosynthesis

“The First 3 Minutes” of the Universe (Steven Weinberg, 1976)

At end of inflation (10-30 sec), start with “quark soup”. Universe expands rapidly.

1st Frame: t = 0.01 sec, T = 100 billion K, density = 4 billion that of water. Present: electrons, neutrinos, protons (+ other elementary particles). Very few protons and neutrons: p+ + e− ↔ no + ν

no + e+ ↔ p+ + ν

2nd Frame: t = 0.1 sec, T = 30 billion K, more protons than neutrons.

3rd Frame: t = 1 sec, T = 10 billion K, density 400,000 that of water.

4th Frame: t = 14 sec, T = 3 billion K. Present: 1H (=p), 2H, 3H, 3He.

5th Frame: t = 3 min, T = 1 billion K (70 times that of center of sun).

6th Frame: t = 30 min, T = 300 million K. Density 10 times that of water. Present: 75% H, 24% 4He, some Li, Be, B.

Main nuclear reactions occurring in early universe immediately after BB

7th Frame: t = 380,000 y, T ~ 1000 K.The universe now cool enough so that electrons attach to nuclei, and neutral atoms form, making the universe transparent to radiation.

There follows:

That situation is “seen” by COBE, WMAP and Planck: the radiation has come down to us in the form of microwave background radiation at T = 3 K, having cooled due to expansion of universe.

ConfirmationCurves of 4He, 2H, 3He, 7Li calcula-ted as a function of baryon density. Almost perfect match with obser-vation reached at baryon density as measured by WMAP.

Afterwards: Nucleosynthesis...

Heavier elements (C, N, O, ...) are made by accretion, as long as energy of progressively heavier nuclei decreases. Continues until Fe (# 26) is reached.Process takes place inside stars where temperature and pressure are highenough for nuclear reactions (fusion: from light elements to heavy ones) to take place.

After Fe, non-equilibrium fusion must take place. Requires explosive compression of stars, i.e. supernovae. Conversely, fission processes (heavy elements to lighter ones) generate energy, such as those involving U, Pu,... Fission reactions can be controlled industrially.

[Example of fusion: Hydrogen to Helium provides huge energy of reaction. Requires extremely high temperatures and pressures. How to contain reactants? That is why “Fusion is the energy source of the future, and always will be (like controlling an H bomb)!]

Summary: “Before Fe, fusion is energetically favorable; after Fe, fission is energetically favorable, but fusion is not.

Iron (Fe), has the most stable nucleus of all. That is why there is so much Fe in the solar system.

He

Fe

HU

Nuclear Stability

simplified 2-dim model

schematic 3-dim model

Where do the atoms (Mendeleev Table) come from?

Interior of a Star (schematic)

Star successively “burns” H, He, C, O, Ne, Mg, Si, S. Stops at Fe.

Where do we fit in?Stars tend to cluster into galaxies, galaxies into clusters and filaments. Remaining gas around a new star condenses into a disc, and the disc condense into planets. Extrasolar planets now number into the 1000’s, so that planetary systems are now the rule, not the exception. Some planets located in the “comfort zone” of a star may give rise to life, even in rare cases, to “intelligent” life.

Active star factory in our galaxy (Herschel European telescope) and Hubble’s “pillars of creation”

“We are all made of stardust” (Carl Sagan)

Exoplanets

Earliest discovery by Didier Queloz and Michel Mayor (Geneva) in 1995.

Now (2015) over 2000 confirmed, including ~1000 systems.

On average, about 1 planet/star; ~200 billion stars in Milky Way.

~ 11 billion planets in MW in “habitable zone”, i.e. with liquid water on surface.

Jan. 15, 2015, USB: Three nearly earth-size planets orbiting nearby star (150 ly).

Some conclusions...

Because of the finite velocity of light (300,000 km per second, in vacuum), and regardless of expansion, seeing further into space means seeing further back in time.

Because of expansion, there must have existed an initial instant of time and space.

Is there a final instant? No, expansion seems eternal. Universe will become infinitely more dilute, galaxies further and further away.

Because of expansion, Galaxies very far away are receding from us at velocity greater than the seed of light. This places an observational limit on how far out we can see (time horizon). That limits the observable universe by an “event horizon”.

In another scenario, expansion will slow down, resulting in a final Big Crunch.

Extragalactic SuperNovae (ESP?) Project (1998)

- Two independent teams (Berkeley: S. Perlmutter, G. Goldhaber ...;

A. Reiss, B. Schmidt, A. Filippenko, …)

- SuperNovae (SN) as standard candles.

Probability: about 1 in 100 years per galaxy..

- Distant SN fainter than expected from red shift (Hubble law).

So, expansion was slower in the distant past.

- Expansion of the Universe is accelerating!

From Saul PerlmutterUCB / LBNL (1998)

Georges Lemaître, manuscript (1927), Louvain

Composition of mass-energy of the Universe

Dark Energy70%

Dark Matter26%

Baryonic4%

Conclusions from Extragalactic Supernovae Project

Distant objects appear to recede from us more slowly that expected.

Thus the recession speed is increasing with time; the expansion of the universe is accelerating!

This independently confirmed observation (Perlmutter group, Adam Reiss group) is recognized as the most important result in astrophysics of the last half-century.

This acceleration can only be rationalized by postulating a universe on the average flat, containing “Dark Energy” making up 70% of the mass-energy of the universe, subjected to a repulsive Cosmological Constant providing the accelerated expansion. The Universe is 13.79 billion years old (after the Big Bang).

Confirmed by CMB, Cosmic Microwave Background Radiation.

The nature of this “Dark Energy” is unknown.

Needed: a theory of quantum gravity of space itself, of the vacuum.

since early ’90:

The Golden Age of Cosmology!

All these amazing results, and their consequences introduce,

Brian SchmidtSaul PerlmutterAdam Riess

George Smoot: Oct. 3, 2006 -- Saul Perlmutter: Oct. 4, 2011

Plus two Nobel Prizes in Physics for UC Berkeley:

Nobel ceremony held Dec. 10, 2011.

Andrei Linde, Sc. Amer. Nov. 1994

Self-Reproducing Inflationary Universe

Andrei Linde (1986)

Imagine a preexisting space of fluctuating “quantum fields”, with multiple hills and valleys. Such is the Landscape. Somehow at places (in this space) where the field is high, it can decay by “rolling down a hill” and come to rest in a “valley”. This process gives rise to violent exponential inflation (Alan Guth, 1980) which ends at a place where a new universe has been is created!

In principle, the landscape can be calculated by using string theory. It yields billions (10500) of valleys, so many that in this whole “landscape of possibilities” perhaps a few will have correct values of fundamental constants to allow the emergence of intelligent (?) life (Susskind).

Very different from the search for a universal mechanism which “zeroes in” on an optimal set of constants, in a “Theory of Everything”.

Physics ain’t what it used to beGeorge Ellis, Nature (Dec. 8, 2005) review of Susskind’s “Cosmic Landscape”.

The idea of countless pocket universes cannot be tested, so is it science?

Artist’s conception (Peter Arnold/Alamy)

In the Beginning...

Conclusions

Self-reproducing eternal inflation reconciles Lemaître and Hoyle: there is (for us) a moment of creation, but overall new universes, in the multiverse, are

constantly being created, ad infinitum. So are chaotic inflation and landscape concepts still considered Science, or metaphysics, or theology?

The Anthropic principle states: “the laws of nature must be consistent with the existence of intelligent life”. Our Universe does not have to be

designed, there are plenty to go around (10500 ?), a few with the right set of parameters. We happen to live in one of those; if we did not, we wouldn’t be

here to talk about it!

Alas, Paradigm Lost: the paradigm of an human-centered world with built-in vector of good and evil, created by an Intelligent Designer, just for us. Instead,

creation appears to be Random. Such is the Multiverse idea.