Scientists can now measure the mass of individual molecules

A new nanodevice is able to measure the mass of a single molecule.  The way this works is the device has a certain vibrational frequency.  This is like a spring that is oscillating at some frequency (simple harmonic motion).  But what we learn about springs is that the frequency depends on the mass that is attached to the spring.  What happens with this device is that when a molecule lands on the device, the frequency changes.  It is the change in frequency that determines the mass.

So this is a wonderful example of taking a basic physics principle and applying it in a new environment.  The engineering of the device is, of course, tricky, but the principle can be understood with the physics we study in class.  Very cool!