I ask myself, where should the college-educated inquirer begin when there are so many good accounts of cosmic discovery addressed to the general reader? There are armchair tours of the Universe aplenty, written for Astronomy 101 liberal-arts courses in the US. These follow a predictable path, starting in the solar system and progressing by turns to the invisible universe of dark energy and dark matter. Here, however, James Kaler has crafted an outstanding short introduction to astronomy and cosmology by adopting a point of view that I have not seen before in a popular account of the cosmos.
For a gentler approach to astronomy, there is a rich literature of history and biography, plus the many thematic texts that outline the new cosmology or advances in planetary exploration. Heaven's Touch is subtler than curriculum-driven accounts, and it paints a larger canvas than the familiar cosmic cameos.
In this account, the backstory explores how the human race relates to the entire Universe. Before reading the book, I pondered on how I relate to the Universe at the personal level: I enjoy scanning the sky, by day or night, searching for the unexpected. Recently, without the benefit of visual aids or membership of an astronomical society, I have seen a dazzling circumzenithal arc (or upside-down rainbow) and exceptionally bright noctilucent clouds, on both occasions from my back garden in central Cambridge. Last December, on the top deck of Queen Mary 2 in the Caribbean, 300 passengers and I enjoyed a lovely shower of Geminid meteors. Prior to that, I witnessed a close conjunction of all five naked-eye planets, three memorably bright comets and two magnificent total eclipses, all accomplished by eye alone: after all, astronomy is looking up!
Why is it that what we see in the firmament induces such a sense of wonder in the human mind? This is not a new question: serious attempts to understand our relation to the cosmos commenced in the second millennium BC, with the compilation of planetary diaries in Mesopotamia.
In the succeeding four millennia, astronomical data consisted largely of two-dimensional positional information, tracking the motion of the planets and the places of the fixed stars. Only in the past century of progress in astrophysics has our gaze plumbed the third dimension, that of radial distance. Albert Einstein added the fourth dimension, time.
Our present knowledge of the metrics of the Universe raises fundamental questions: where do we stand in this immensity of space and time, and how, if at all, are we connected to the physical Universe? Kaler attempts the answer. In so doing, he delightfully negotiates a pathway that sidesteps ontological distraction and the anthropic principle, both of which touch on, in different ways, the notion that the Universe has the properties we measure because we are here as rational beings.
Kaler sensibly adopts for his survey a deliberate structure of how he believes humanity is hardwired to the entire Universe. His literary style is geocentric, and so we move by stages: action in the solar system takes us halfway on the voyage, then we are seriously into serious stars (Kaler's research field) in order to understand the origin of the chemical elements.
In this narrative, the Big Bang is a priori, dark energy and dark matter are not a worry because neither connects to the baryons of which we are made, and astrobiology does not feature at all, presumably because, like string theory, it has not yet produced hard evidence that biogenic processes are at work out there as well as down here.
How are biogenic processes on Earth connected to the heavens? Most obviously, of course, through the Sun, the heat and light of which is essential, even though we may pay it little heed. And it is through our innate ability to process photons through our eyes that our brains produce images not just of our surroundings, but also the Sun, Moon and stars, and our unaided reach extends to the Andromeda nebula, 2.5 million light years away.
Kaler's armchair tour starts on an ocean beach where the wind-driven waves crash on the shore as the tide gradually sweeps in and out. That is due to the gravitational influence of the Moon. GCSE science: no problem there. But wait, there's more. Add the Sun and we get the phenomena of spring and neap tides. For a third variant, let's add the ellipticity of the orbits, then have the Moon at its closest approach. Result: huge tides and massive damage if the heavenly alignments coincide with major storms. And this is all quite predictable: astronomy triumphs over astrology.
In one sense, our connection with the Sun is obvious. But there are surprises - solar neutrinos, for example, the almost massless particles released by the nuclear processes that produce solar energy. About 100 trillion of them passed through your body while you read the preceding sentence, and the total mass of the Sun dropped by 4 million tonnes.
The tilt of the Earth's axis is responsible for the four seasons, in a completely straightforward way. Much less obvious is the way in which the elliptical orbits of various players in planetary choreography combine to produce climatic extremes such as ice ages.
As I write this review, I see from a press release that space scientists in the UK have announced the development of a "gravity tractor" that will save the world. Possibly. Kaler is good on the risk assessment of the consequences of asteroids slamming into the Earth.
The past history of cataclysmic collisions suggests that life on our planet is punctuated by asteroid-driven mass extinctions every 100 million years, as a crude average. The geologic record is our silent witness to heavenly bodies that crashed to Earth, triggering global environmental change. A gravity tractor, as described by the British scientists behind the project, would steal up behind a rogue asteroid and then use gravitational attraction to ever so gently change its orbit.
Not that crashes with the neighbours have always been bad: Kaler reminds us of the gift of water and other volatiles from comets, a logistics solution provided by Jupiter's gravity to deliver frozen ices from the outer solar system to our home planet.
The gift that humans received from the Universe was the creation of the chemical elements. If I may be permitted to continue with the metaphor of gifts, the Big Bang gave us hydrogen, helium, photons and irregularities in the structure that allowed attractive gravity to craft the stars and galaxies. Heaven's Touch explains in an accessible manner the way in which stars acted as crucibles to fuse those gifts into the chemical elements and their isotopes. We are the children of the stars in the literal sense.
Heaven's Touch is a passionate account both of humanity's tangible contact with the Universe at large and the profound influence of the Universe on life on Earth.
In this book, Kaler offers a new take on astrophysics and cosmology, whereby he involves rational beings as participants in the grandeur of the cosmos. He treads in the footsteps of giants such as Sir James Jeans, Arthur Eddington and Sir Fred Hoyle without tripping up. Kaler equals them all by connecting our ordinary human experience of the world in which we live with the immensity of the firmament we can see when night falls.
James B. Kaler, emeritus professor of astronomy at the University of Illinois, earned his undergraduate degrees at the University of Michigan and went on to complete a PhD at the University of California, Los Angeles. He has been based at the University of Illinois since 1964.
His research area, in which he has published more than 120 papers, involves dying stars. Kaler has held Fulbright and Guggenheim fellowships, and he has been awarded medals from the University of Liege and the University of Mexico for his work in the field.
Kaler says he enjoys running when he can, although he says that bad knees have slowed him to half his original competition speed. In addition to indulging a love of cookery, he says he "tries" to play classical guitar and is a "pretty good" trumpet player who loves the baroque, "although it does not necessarily love me in return".
A keen gardener, he was pleased to see his flowers flourish this year. But he says not everything in the garden thrived: "Don't ask about the vegetables."
Heaven's Touch: From Killer Stars to the Seeds of Life, How We Are Connected to the Universe
By James B. Kaler
Princeton University Press
Published 16 September 2009