Hay Festival2013 June 1

HEART OF DARKNESSUnraveling the Mysteries of the Invisible

Universe

Dr Simon Mitton

St Edmund’s College,University of CambridgeVice President, Royal Astronomical SocietyGuest Lecturer Astronomy, RMS Queen Mary 2

Website www.totalastronomy.comEmail simon@totalastronomy.com

The nature of the universe. What the ancients achieved, and why we should be impressed

• Plato and Aristotle taught that the heavens can be subjected to rational enquiry. Our book Heart of Darkness presents the full history of attempts to understand why the universe has structure

• The Greek geometers changed the nature of that enquiry forever. Geometry became the key to understanding the mechanics of the universe. Geometrical argument remains at the heart of understanding structure in the universe.

• Hipparchus of Rhodes: first star catalogue (850 stars!); discovered precession of the equinoxes. Our narrative stresses the great importance of astronomical surveys for revealing the structures within the universe.

ISAAC NEWTON

ISAAC NEWTON

Newton’s universal law of gravitation means each object in the universe is attracted to all other objects

Universal attraction of gravity means the solar system (and the universe) is unstable

Thomas Wright puts the Sun as a star at the center of the Milky

Way

explores objects beyond the solar system

1755 Immanual Kant proposes “island universes.”

From 1782 – 1802 Herschel undertakes sky surveys to catalogue and examine the nebulae.

WILLIAM HERSCHEL 1738-1822

WILLIAM HERSCHEL

Gravity shapes the nebulae, making them more condensed over time

WILLIAM PARSONS, THIRD EARL OF ROSSE

WILLIAM PARSONS, THIRD EARL OF ROSSE1845, Discovery of spiral structure in the nebula M51

SIR JOHN HERSCHEL 1792-1871

At the Cape of Good Hope he completes his father’s work on surveying the

heavens

Vesto Slipher 1875 – 1969

VESTO SLIPHER 1875-1969 – clocks the speeds of galaxies

Lowell Observatory, Flagstaff, Arizona. Dome and 24-inch telescopeIn 1917 Slipher announced the measurement of

the velocities of a dozen galaxies, all of them rushing away from our Milky Way galaxy

ALBERT EINSTEIN 1879-1955In1915 Einstein published the General Theory of Relativity, a theory of gravity that includes the “time” dimensionArthur Eddington in Cambridge understands that GR can be used to model the properties and behaviour of the entire universeAt the Total Eclipse of 1919 Eddington confirms GR – a geometrical theory, which joins the cosmologists’ toolkit

EDWIN HUBBLE 1889-1954

1920s, Hubble measures the distances to nearby galaxies, his greatest achievement

Edwin Hubble 1889 –1954

The data of Slipher and Hubble combinedThe velocity-distance relation (Hubble Law)

Speed away from us

SLIPHER

Distance from us HUBBLE

GEORGES LEMAîTRE 1894-1966

1923-24. Georges Lemaître joins Eddington in Cambridge. As mathematicians, they work together on geometrical models of the universe using GR

1924 Lemaître the theorist goes to the other Cambridge to work at Harvard and MIT. He meets observers Vesto Slipher and also Edwin Hubble, with both of whom he discusses model universes

The FIREWORKS UNIVERSE 1927

1927 Lemaître has an explanation for Hubble’s results.

Publishes in 1927 a paper (in French) on the expansion of the universe in which he demonstrates that the model is an allowed solution to Einstein’s GR equationsEinstein regards this as preposterous but Eddington supports his former student1930 Lemaître speaks in London on the expanding universe, and publishes the Primeval Atom concept in Nature

Lemaître called his model the “Fireworks Universe”. The moniker “Big Bang” came later, in 1948, courtesy of Fred Hoyle.

FRITZ ZWICKY 1898-1974

1933 Coma cluster, measures internal velocities, proposes Dark Matter

1935 Pioneers the use of Schmidt cameras for survey work

1942 Caltech. 1948 First astronomer to use the 200-inch at Palomar

1960s Catalog of Galaxies and Clusters of Galaxies

ALLAN SANDAGE 1926-2010

Hubble’s successor at Palomar

Devoted his career to a “search for two numbers”, the Hubble constant and the deceleration parameter. These two numbers would specify the type of universe we are in.

The work was a quest for “standard candles” to provide the distance scale of the universe

BEATRICE TINSLEY 1941-1981

1966 Awarded PhD Univ Texas at Austin, and received a postdoc Fellowship

Her 1968 paper in Astrophysical Journal brings Sandage’s house of cards crashing down! Stellar evolution implies galactic evolution, therefore all galaxies are not the same. She destroys the “search for two numbers”.

Further papers follow; she published 11 papers in 1972

ARNO PENZIAS AND ROBERT WILSON

Arno Penzias and Bob Wilson1978 Nobel Prize Physics

1964 This strange radio telescope accidentally discovered that the entire sky emits a weak microwave signalThe microwaves are a form of heat energy at a very low temperature

What had been discovered was heat energy, in the form of microwaves, released in the Big Bang

American Astronomical Society Meeting January 1992

Mapping the microwave background

1992, Ripples in the background radiation show structure when the universe was 380,000 years old

2003 – 2012 Better maps of cosmic microwaves

interpreted to discover major properties of the universe

2013 European Space Agency Planck Mission:

the most precise all-sky map of the oldest light in the universe

The distant universe imaged by the Hubble Space Telescope

The Hubble eXtreme Deep Field (2012)

5,500 galaxiesup to 13.2 billion light years away

Clusters of galaxies are weighed down by dark matter

Unseen dark matter is ten times more common than ordinary matter

An enormous ring of dark matter surrounds a great cluster of

galaxies

NOBEL PRIZE PHYSICS 2011

Discovery of the accelerating universe

Saul PerlmutterBrian Schmidt Adam Reiss

A great discovery:the expansion of the universeis accelerating!

Distant galaxies - 10 billion light years away - are going more slowly than expected

Nearer to home, the rate of expansion has speeded up in the last 5 billion years. This cosmic jerk is driven by mysterious Dark Energy!

The universe: what’s in the pie?

Just over one quarter of the universe is unseen dark matterLess than one-twentieth of the universe is visible matterTwo thirds of the universe is present as mysterious dark energy

The Universe: What we know

1. It is expanding, and the rate is speeding up

2. It had a hot beginning - the Hot Big Bang

3. Its age is 13.82 billion years

4. It contains ordinary matter (5%), dark matter (27%), and dark energy (68%)

The Universe: How galaxies formed

1. The microwave background radiation shows that structure existed 380,000 years after the Big Bang2. This structure must have been present before the inflation era

3. Dark Matter provided the gravitational attraction to allow formation of structure on the scale of clusters of galaxies

4. Without Dark Matter, the Dark Energy would have propelled the expansion too fast. No galaxies, stars, or planets would exist!

“Why is there something rather than nothing?”

• The universe grew from a singularity, or quantum fluctuation, at the scale of the Planck length 10-43 m. The resulting expansion could not have been infinitely uniform

• The universe went through cosmic inflation 10-36 – 10-33 seconds. Fluctuations preserved – baryon acoustic oscillations

• The First Three Minutes – origin of light elements. The next 700,000 years – era of recombination

• Fine tuning of the universe: expand too fast -> no structure, too slow -> collapse under gravity.

• The Goldilocks solution: conditions “just right”. But honey and nice words do not work in cosmology …

• … Dark matter to the rescue! Amount detected is “just right” to allow structure to develop via the gravity of dark matter – the visible matter alone is insufficient

• Let’s see the dark matter simulation

The Universe: What we do not know

1. In cosmology, the current generation always claims to have the “right” model2. Can we really believe our models of the universe when it was 10-36 seconds old? Is it not hubris to proclaim in these terms?3. We do not know what dark matter is. Our

searches have been fruitless.

4. Dark energy is a complete mystery. Is it a new realm of physics?

Books bySimon Mitton

Hay Festival2013 June 1

HEART OF DARKNESSUnraveling the Mysteries of the Invisible

Universe

Dr Simon Mitton

St Edmund’s College,University of CambridgeVice President, Royal Astronomical SocietyGuest Lecturer Astronomy, RMS Queen Mary 2

Website www.totalastronomy.comEmail simon@totalastronomy.com