Presentation is loading. Please wait.

Presentation is loading. Please wait.

Royal Astronomical Society Public Lecture 2012 May 8 THE ORIGIN OF STRUCTURE IN THE UNIVERSE Simon Mitton Department of the History and Philosophy of Science,

Similar presentations


Presentation on theme: "Royal Astronomical Society Public Lecture 2012 May 8 THE ORIGIN OF STRUCTURE IN THE UNIVERSE Simon Mitton Department of the History and Philosophy of Science,"— Presentation transcript:

1 Royal Astronomical Society Public Lecture 2012 May 8 THE ORIGIN OF STRUCTURE IN THE UNIVERSE Simon Mitton Department of the History and Philosophy of Science, University of Cambridge Fellow, St Edmund’s College, Cambridge

2 Why is there something rather than nothing?

3

4 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 The Greek geometers changed the nature of that enquiry forever. Geometry became the key to understanding the mechanics of the universe Eratosthenes measured the diameter of the Earth Hipparchus of Rhodes: first star catalogue (850 stars!); discovered precession of the equinoxes Ptolemy of Alexandria: brings the geocentric model of planetary motion close to perfection, but at a cost of complexity. Nevertheless it worked for 1400 years. Ptolemy’s Almagest is in the rare books room upstairs.

5 Newton’s Principia

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

7 William Herschel, discoverer of the universe, and first cosmologist

8

9

10 M51 Lord Rosse 1845

11 Astrophysics was in its infancy. So was astrophotography. The Nature of the Universe the last time we had a Diamond Jubilee (1897) Mainstream view was that the white nebulae are members of the Milky Way Cosmology did not exist In London professional astronomy was still dominated by the needs of navigation and time keeping, as well as star positions and stellar motion

12 Vesto Slipher 1875 – 1969 Step 1 to the First Great Discovery Lowell Observatory, Flagstaff, Arizona Territory Andromeda Nebula is coming towards the Milky Way at a high velocity (blueshift)

13 Andromeda galaxy

14

15 Vest Sipher 1875 – 1969 Step 1 to the First Great Discovery By 1917 Slipher discovered that a dozen nearby galaxies are speeding away from the Milky Way (redshifted) What could this mean? By the mid-1920s the number of redshifts was ~40

16 Einstein and Eddington, The Observatories Step 2 to the First Great Discovery 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, which henceforth joins the cosmologists’ toolkit

17 Step 3 to the First Great Discovery Georges Lemaître joins Eddington in Cambridge. They work together on models of the universe 1924 Lemaître the theorist goes to the other Cambridge to work at Harvard and MIT. He meets observers Slipher and also Edwin Hubble, with both of whom he discusses model universes

18 Step 4 to the First Great Discovery At Mount Wilson in the 1920s Hubble measures the distances to nearby galaxies for which velocities are available (almost all of them from Slipher). His truly great triumph was getting the distance to the Andromeda Nebula, proving beyond doubt that it was a great galaxy Hubble soon noticed a correlation: the larger the redshift (velocity of recession), the greater the distance to the galaxies

19 The First Great Discovery: The universe is expanding Speed away from us Distance from us

20 Step 5 to the First Great Discovery 1927 Lemaître has an explanation for Hubble’s results. Publishes in 1927 a paper 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 1930 Lemaître speaks on the expanding universe at the RAS, publishes the Primeval Atom concept in Nature, and the following year has a paper in Monthly Notices Lemaitre called his model the “Fireworks Universe”. The moniker “Big Bang came later, in 1948.

21 1948 – 1964 Cosmologists at war! Big Bang versus Steady State Much blood letting in this very room!

22 Big Bang versus Steady State Martin Ryle and Fred Hoyle The great battle between Ryle and Hoyle concerning cosmology ran from This is fully documented in my acclaimed biography, available from Amazon or the publisher, Fred Hoyle: A Life in Science By Simon Mitton Publisher: Cambridge University Press 2011 Online ISBN: Paperback ISBN: Subjects: Astronomy: general interest, History of science and technology

23 The Second Great Discovery: the whole universe is filled with microwaves 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

24 American Astronomical Society Meeting January 1992

25 2003 – 2008 Better maps of cosmic microwaves Tell us the age of the universe 13.7 by Reveal the presence of dark matter and dark energy Evidence of reverberating sound waves from the Big Bang (baryon acoustic oscillations)

26 The second great discovery - the ripples show irregularities beginning to form right after the Big Bang HM Queen Elizabeth II catches up on cosmology! 8 May 2007

27 The distant universe imaged by the Hubble Space Telescope

28 The universe: what’s in the pie?

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

30 An enormous ring of dark matter surrounds a great cluster of galaxies

31

32 “Why is there something rather than nothing?” The universe grew from a singularity, or quantum fluctuation, at the scale of the Planck length m. The resulting expansion could not have been infinitely uniform The universe went through cosmic inflation – 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

33 Present distribution of dark matter in the universe Zooming in on a massive cluster of galaxies

34 I ’ ve seen out to the limit of the observable universe and believe me it ’ s no better out there than it is here …

35 Big Bang versus Steady State Martin Ryle and Fred Hoyle The great battle between Ryle and Hoyle concerning cosmology ran from This is fully documented in my acclaimed biography, available from Amazon or the publisher, Fred Hoyle: A Life in Science By Simon Mitton Publisher: Cambridge University Press 2011 Online ISBN: Paperback ISBN: Subjects: Astronomy: general interest, History of science and technology

36 Royal Astronomical Society Book Series Editor: Simon Mitton Department of the History and Philosophy of Science, University of Cambridge Fellow, St Edmund’s College, Cambridge Forthcoming Book Taking the Back off the Watch A Personal Memoir Mitton, Simon (Ed.) Jointly published with the Royal Astronomical Society 2012, 2012, XVII, 225 p. 27 illus. ISBN Enthralling life story of one of the most remarkable astrophysicists of the second half of the twentieth century who explained pulsars as rotating neutron stars With intriguing anecdotes revealing Gold’s scientific curiosity and deep understanding of physics Carefully edited by the author of the biography of Sir Fred Hoyle With a Foreword by Freeman Dyson Published under the auspices of the Royal Astronomical Illustrated with photographs, many never previously published Thomas Gold ( ) had a curious mind that liked to solve problems. He was one of the most remarkable astrophysicists in the second half of the twentieth century, and he attracted controversy throughout his career. Based on a full-length autobiography left behind by Thomas Gold, this book was edited by the astrophysicist and historian of science, Simon Mitton (University of Cambridge).


Download ppt "Royal Astronomical Society Public Lecture 2012 May 8 THE ORIGIN OF STRUCTURE IN THE UNIVERSE Simon Mitton Department of the History and Philosophy of Science,"

Similar presentations


Ads by Google