An insider’s tale of Curiosity

When the Mars rover Curiosity landed safely after its “seven minutes of terror” descent to the red planet’s surface, Roger Wiens’ sigh of relief was bigger than most. As the principal investigator for the rover’s ChemCam instrument – which uses a laser to vaporize Martian rocks and a spectrometer to sniff out the chemical composition of the resulting debris – Wiens had more than a decade’s worth of work invested in the craft’s survival. And survival, as he explains in his book Red Rover, was anything but assured. Before becoming involved with Curiosity, he worked on a spacecraft called Genesis, which spent 27 successful months collecting particles from the solar wind only to crash into the Utah desert when its parachute failed to deploy during re-entry. That disaster was far from total, since Wiens and his colleagues were able to recover significant amounts of data from the craft’s shattered innards. Nevertheless, he acknowledges in the book that the last-minute failure of Genesis coloured his view of Curiosity’s chances: “In my dreams, everything that could go wrong played itself out at least once,” he writes. The list of things that could have prevented Curiosity from settling safely in Mars’ Gale Crater was indeed long. Wiens gives roughly equal time to bureaucratic obstacles and technical ones, but although descriptions of scientific review panels are unlikely to set the literary world alight, he has a good eye for interesting details and is clearly passionate about his work. He is also immune from the scourge of “mention-itis” (a disease that compels some scientist-authors to mention the name of everyone who ever contributed to a project), and is frank but not rude when it comes to describing disagreements and disappointments. The result is a book that anyone interested in a career in space science should read, and many outside the field will appreciate.

• 2013 Basic Books £17.99/$25.99hb 256pp

Moonshine and sunshine

In the early 1930s Ernest Rutherford called the energy gained from fusion “a very poor kind of thing”, adding that “anyone who expects a source of power from [fusion] is talking moonshine”. By the 1950s the situation seemed more promising: one researcher, James Tuck, named his fusion device at the Los Alamos National Laboratory “the Perhapsatron”. Since then, the fortunes of fusion have oscillated between moonshine and sunshine, and in his book A Piece of the Sun: the Quest for Fusion Energy, Daniel Clery skilfully chronicles this complex history. He begins by outlining the great attractions of fusion, such as the abundance of the fuel and the relatively small amount of waste produced. Unfortunately, there are numerous practical barriers to achieving controlled fusion, and Clery spends the rest of the book describing how scientists in (mostly) the UK, US and Russia overcame some of them and continue to struggle with others. Throughout fusion’s history, he notes, funding has “ebbed and flowed depending on the eagerness of governments to find alternative sources of energy”. Unfortunately for fusion’s proponents, that pattern may not bode well for the future. Although construction on the ITER fusion reactor is under way in France, and the US National Ignition Facility is (theoretically) still trying to live up to the middle part of its name, the emergence of fracked natural gas as a politically popular new source of conventional energy suggests that fusion funding could be heading for another fallow period. Certainly, we are unlikely to return to the glory days of the late 1950s when one Soviet researcher, Vladimir Mukhovatov, suggested to his boss that lining the walls of his fusion device with gold might prevent the plasma from being contaminated. As Clery puts it, “A week later a 2 kg lump of gold was sitting on his desk.”

• 2013 Overlook Press $27.95hb 320pp/Gerald Duckworth £25hb 336pp

The hardest problems

What constitutes a hard problem? For a computer scientist like Lance Fortnow, the answer can be summed up by an acronym: NP. In The Golden Ticket: P, NP, and the Search for the Impossible, Fortnow explains what these two letters mean and why it matters. Initially, he defines NP only loosely, as “the collection of problems that have a solution that we want to find”, while its counterpart, P, is “the problems to which we can find a solution quickly”. If P = NP, he explains, we live in “the beautiful world” where computers can work out most anything we ask them to. But if P ≠ NP, as most mathematicians and computer scientists believe, we are going to have to do some things the hard way. Later, Fortnow elaborates on his definitions of P and NP by describing the imaginary land of “Frenemy”, in which everyone is either friends or enemies with everyone else. In Frenemy, the government needs to know how many colours of paint are required if neighbouring houses must not share the same colour; primary-school teachers would like their classes to contain as few pairs of enemies as possible; and children play a game in which pairs of friends pass a stick to each other and everyone must get the stick exactly once. These challenges may sound simple, but in fact they are all NP problems. In fact, they are “NP-complete”, the hardest type of NP problem, and a solution to one of them – if it existed – could also be used to solve the others. Fortunately, many NP-complete problems do have “good enough” inexact solutions, which is why your sat nav can work out a good route even though finding the absolute shortest route between n points (the “travelling salesman” problem) is NP-complete. Fortnow uses examples such as these rather than equations, and in the introduction he explains that he borrowed this tactic from Stephen Hawking’s A Brief History of Time. The book’s more direct connections to physics are perhaps less happy; the chapter on how quantum computing might affect the NP conundrum is cursory, and Fortnow’s suggestion that algorithms in “the beautiful world” could predict the weather a year in advance seems to conflict with chaos theory. Still, The Golden Ticket does a good job of explaining a complex concept in terms that a secondary-school student will understand – a hard problem in its own right, even if not quite NP.

• 2013 Princeton University Press £18.95/$26.95hb 192pp