B00B7H7M2E EBOK (44 page)

The age of the universe, its shape, its expansion rate, its composition, its density . . . when a satellite called the Wilkinson Microwave Anisotropy Probe, better known as WMAP, took to the heavens in June 2001, the hope was that it would settle most of these issues once and for all.  WMAP lived up to its promise. In February 2003, after the decades of research and debate that you’ve read about in the later chapters of this book, WMAP nailed down the age of the universe: 13.7 billion years. 

WMAP was the result of a partnership between the Goddard Space Flight Center and Princeton University, and its primary mission was to produce a map of the cosmic microwave background radiation that was more precise than had ever before been possible.  WMAP could detect and measure temperature differences of a millionth of a degree.  Being a satellite rather than a land based instrument, it could take these measurements over the entire sky. 

In addition to determining the age of the universe, WMAP data showed that the patterns in the CMBR froze into place when the universe was 380,000 years old.  WMAP results also showed that space is flat (Friedmann’s third model, see Chapter 6), and that most of the energy in the universe today is ‘dark energy,’ also called “missing energy” (see Chapter 8). WMAP measurements showed that the variations in temperature and density in the CMBR, observed across the sky – the variations that seeded the formation of galaxies -- all had roughly the same amplitude regardless of their length.  The distribution of the variations was random and all forms of energy had the same variation, just as predicted by the standard Big Bang inflationary model. As John Barrow summed it up, ‘The growing observational evidence for the distinctive pattern of temperature variations in the microwave background radiation means that we take very seriously the idea that our visible portion of the universe underwent a surge of inflation in its very earliest stages.’

Fine tuning the “standard model,” different versions of inflation theory had been presenting slightly different scenarios of precisely how inflation happened, and they were making different predictions about what pattern of temperature variations we should expect to find in the incoming CMBR if we compare its temperature in different directions. WMAP data gave scientists ways to test the different inflation stories. The temperature of the CMBR is dispersed extraordinarily evenly, but it does vary slightly from point to point in the sky.  Warmer areas are assumed to correspond with denser regions in the very early universe. 

WMAP results released in 2008 showed that the data was placing tight constraints on inflation, supporting some versions and not others. WMAP principal investigator Charles Bennett expressed his astonishment “that bold predictions of events in the first moments of the universe now can be confronted with solid measurements.” A results summary in January 2010, when the WMAP mission was preparing to wind down, confirmed that the large-scale temperature fluctuations in the CMBR are slightly more intense than the small-scale ones (a subtle but key prediction of many inflation models), and the universe is indeed flat – a conclusion supported in part by the randomness of locations of hot and cold points in the CMBR.

Other important issues remained unresolved.  One important piece of evidence was missing: Inflation theory predicts what the patterns and characteristics of gravitational waves originating from the Big Bang should be like as they show up in the CMBR. WMAP failed to detect these gravitational wave footprints. Nor was it determined whether the “dark energy” (or “missing energy”) was due to the cosmological constant –“vacuum energy” – or “quintessence.”

When the WMAP satellite went into “graveyard orbit” in October 2010, the torch was handed on to a new satellite from the European Space Agency.  The Planck satellite had been launched in May 2009, when the WMAP mission was preparing to wind down.  Planck’s detectors were designed to operate at a temperature of minus 273.05C, just a tenth of a degree above absolute zero. The project’s first goal was to study some foreground sources that make studies of the CMBR tricky, but a formal release of fully prepared CMBR images, analyses, and scientific papers is expected, at the earliest, in 2013.  Watch also for results coming from projects known as LIGO and LISA, which use a technique called laser interferometry to detect gravity waves, for these waves potentially offer the most direct opportunity we are likely ever to have to probe what the universe was like during the first split second of its existence.

1. A 15th century woodcarving of Ptolemy (second century AD), in the Ulm Cathedral: ‘When I trace at my pleasure the windings to and fro of the heavenly bodies, I take my fill of ambrosia, food of the gods.’

2. Drawing from Nicolaus Copernicus’s book
De revolutionibus
(1543), placing the Sun at the centre with the planets orbiting it. Beyond them is the ‘immobile sphere of the fixed stars’. The Moon orbits the Earth.

3. Johannes Kepler (1571–1630), discoverer of eliptical orbits: ‘Don’t sentence me completely to the treadmill of mathematical calculations – leave me time for philosophical speculations, my sole delight.’

4. Aristotle, Ptolemy and Copernicus on the Frontispiece of Galileo’s
Dialogo
(1632). The title page assures that this ‘discourse concerning the two chief systems of the world, Ptolemaic and Copernican,’ discusses ‘without prejudice one view, then the other, on the basis of philosophy and natural law’.

5. Woodcut showing the Octagon Room at the Royal Observatory in Greenwich as it looked in Flamsteed’s time, in the 17th and early 18th century.

6. One of the earliest photographs ever taken: Sir John Herschel’s 1839 photo of his father’s great 40-foot telescope.

7. Edmond Halley (1656–1742): ‘There remains but one observation by which one can resolve the problem of the Sun’s distance, and that advantage is reserved for astronomers of the following century.’ He left instructions for studying the transit of Venus across the Sun in 1761.

8. Sir William Herschel, astronomer and composer (1738–1822): ‘I used frequently to run from the harpsichord at the theatre to look at the stars during the time of an Act and return to the next Music.’

9. Caroline Lucretia Herschel, in a drawing made when she was 97, in 1847. A friend wrote that it does not ‘do justice to her intelligent countenance’.