@objectivelygoodsongs: A CD can spin so fast that it completely shatters, even though it looks like a solid piece of plastic. At extreme speeds, the disc experiences more stress than it can handle. As the CD spins faster, stress builds inside the plastic, especially around small cracks. Eventually, one weak spot can cause the entire disc to break apart in a fraction of a second. When it shatters, sharp fragments fly outward at high speeds because of the energy stored in its rotation. The same forces affect turbines and other high-speed machines, which engineers must carefully design to withstand extreme speeds.