This Week in Science

摘要

In a dynamical universe (one that is expanding), you would expect to see Doppler, or red shifts, of spectrograph lines of distant objects that are moving further and faster away from the observer, and for such shifts to drift in velocity over time. Determining the extent of velocity drift, however, requires a level of precision that has not been available-less than one centimeter per second per year. Steinmetz et al. (p. 1335; see the Perspective by Lopez) show how that situation may change using a laser frequency comb produced by an optic fiber. In a proof-of-principle experiment, they combine such a comb of equally spaced wavelengths with an astronomical observation (the Sun) to precisely measure and calibrate the wavelengths of the spectrogram.