Resumen de Cheating light pulses break Newtonian law
Isaac Newton just got cheated. Laser pulses have been made to accelerate themselves around loops of optical fibre, seeming to break the physicist's law that every action must have an equal and opposite reaction. The work exploits a trick with light that only makes it appear to have mass, so it is a bit of a dodge. Ulf Peschel at the University of Erlangen-Nuremberg in Germany and his colleagues have made a diametric drive using effective mass. As photons travel at the speed of light they have no rest mass. But if one shines pulses of light into some layered materials, such as crystals, some of the photons can be reflected backwards by one layer and forwards by another. That delays part of the pulse, causing it to interfere with the rest of the pulse until it propagates more slowly through the material.
