The universe: why does it exist? Why is there something rather than nothing? Where and why did structure arise: galaxies, and clusters of galaxies. This slide show is a full history of enquiry into how structure arises in the universe. It goes from Plato and Aristotle to the Nobel Prize in Physics 2011. The title Heart of Darkness refers to a book that has the full story: Heart of Darkness, by Jeremiah P Ostriker and Simon Mitton, ISBN 978 0691134307

1. Hay Festival
2013 June 1
HEART OF DARKNESS
Unraveling the Mysteries of the Invisible Universe
Dr Simon Mitton
St Edmund’s College,University of Cambridge
Vice President, Royal Astronomical Society
Guest Lecturer Astronomy, RMS Queen Mary 2
Website www.totalastronomy.com
Email simon@totalastronomy.com

2. 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.

3. ISAAC NEWTON

4. 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

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

6. 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

7. WILLIAM HERSCHEL
Gravity shapes the nebulae, making them more
condensed over time

8. WILLIAM PARSONS, THIRD EARL OF ROSSE

9. WILLIAM PARSONS, THIRD EARL OF ROSSE
1845, Discovery of spiral structure in the nebula M51

10. SIR JOHN HERSCHEL 1792-1871
At the Cape of Good Hope he completes his
father’s work on surveying the heavens

11. Vesto Slipher 1875 – 1969
VESTO SLIPHER 1875-1969 – clocks the speeds of galaxies
Lowell Observatory, Flagstaff, Arizona.
Dome and 24-inch telescope
In 1917 Slipher announced the measurement of the velocities
of a dozen galaxies, all of them rushing away from our Milky
Way galaxy

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

13. EDWIN HUBBLE 1889-1954
1920s, Hubble measures the
distances to nearby galaxies, his
greatest achievement
Edwin Hubble 1889 –1954

14. The data of Slipher and Hubble combined
The velocity-distance relation (Hubble Law)
SpeedSLIPHER
Distance from us HUBBLE

15. 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

16. 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 equations
Einstein regards this as preposterous but Eddington
supports his former student
1930 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.

17. 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

18. 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

19. 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

20. ARNO PENZIAS AND ROBERT WILSON
Arno Penzias and Bob Wilson
1978 Nobel Prize Physics
1964 This strange radio
telescope accidentally
discovered that the entire sky
emits a weak microwave signal
The 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

21. American Astronomical Society Meeting January 1992

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

23. 2003 – 2012 Better maps of cosmic microwaves
interpreted to discover major properties of the universe

24. 2013 European Space Agency Planck Mission:
the most precise all-sky map of the oldest light in the universe

25. The distant universe imaged by
the Hubble Space Telescope

26. The Hubble eXtreme Deep Field (2012)
5,500 galaxies
up to 13.2 billion light years away

27. Clusters of galaxies are weighed down by dark matter
Unseen dark matter is ten times more
common than ordinary matter

28. An enormous ring of dark matter surrounds
a great cluster of galaxies

29. NOBEL PRIZE PHYSICS 2011
Discovery of the accelerating universe
Saul Perlmutter Brian Schmidt Adam Reiss

30. A great discovery:
the expansion of the universe
is 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!

31. The universe: what’s in the pie?
Just over one quarter
of the universe is
unseen dark matter
Less than one-twentieth
of the universe is visible
matter
Two thirds of the
universe is present
as mysterious dark
energy

32. 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%)

33. 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!

34. “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

35. The Universe: What we do not know
1. In cosmology, the current generation always
claims to have the “right” model
2. 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?

36. Books by
Simon Mitton

37. Hay Festival
2013 June 1
HEART OF DARKNESS
Unraveling the Mysteries of the Invisible Universe
Dr Simon Mitton
St Edmund’s College,University of Cambridge
Vice President, Royal Astronomical Society
Guest Lecturer Astronomy, RMS Queen Mary 2
Website www.totalastronomy.com
Email simon@totalastronomy.com