Photons are bizarre: They have no mass, but they do have momentum. And that allows researchers to do counterintuitive things with photons, such as using light to push matter around.
Recently, a group of scientists led by chemist Gordon Shaw at NIST’s Physical Measurement Laboratory (PML) has been taking advantage of this property to develop devices that can create and measure minute forces, an area traditionally underserved by the metrology community.
Source: http://www.nist.gov/pml/div684/grp07/measuring-tiny-forces-with-light.cfm.
