Michelangelo's David, perhaps the world's most famous Renaissance sculpture, looks good for a 514-year-old, but that doesn't mean he hasn't been subjected to the indignities of aging. In the case of this particular marble statue, the issue is one of posture—over the years, he has started tilting forward, causing his ankles to crack. As a result, in a few centuries, David could topple completely.
At Yale University, engineering students and the university's Institute for the Preservation of Cultural Heritage have been studying the effects of gravity on the statue in the hopes of one day coming up with a technique to stop him from falling.
The students built a machine called the Force Relay Exertion Device to imitate the stress of gravity on David's ankles over time. They built step-shaped models to mimic the angle and pressure on his ankles, using concrete, clay, and other materials to study how different media will hold up. They placed those models within the machine, applying pressure until the fake ankles broke into pieces. From that point the team could gauge what kind of force and time lapse would cause the ankles to crack.
The students didn't solve David's issues in the half-semester they spent studying the statue, but the machine they built is still being used by the Institute for the Preservation of Cultural Heritage in other materials sciences classes.
You can watch how the machine works in the video below.