Michelangelo's sixteenth-century Pietà in the Museo dell'Opera del Duomo in Florence, Italy, incorporates a mystery as deep as its expressive beauty. Having worked for a decade on the carving he intended for his own tomb, Michelangelo apparently attacked his 2.5-metre sculpture in a fit of rage, hacking limbs from the four carved figures. These were later re-attached by his assistant, apart from Christ's left leg, which remains missing.

Why did he do it? Did he fear it fell short of perfection? Was he angered by a flaw emerging in the marble? Had he been afraid that his positioning of the left leg across the Virgin's lap was immodest?

In a collaborative project with art historian Jack Wasserman, scientists have used IBM's most sophisticated three-dimensional imaging technologies to create a 'virtual Pietà'. This has enabled Wasserman to learn more about how the sculpture was physically carved and repaired. It has also allowed him to put forward his theory that Michelangelo was not intending to destroy his work in anger at all. By 'virtually dismembering' the re-attached limbs, and studying the carving from all angles, Wasserman concludes that the limbs had been detached selectively, and with care, perhaps to create a composition where Christ is being lowered from the Virgin's lap, rather than into it.

Wasserman's book Michelangelo's Florence Pietà, published by Princeton University Press ($75), describes the extraordinary technical analysis of one of the most important artworks of post-Renaissance Italy. It also includes a CD of the virtual Pietà.