text: Photons are massless, but then do possess momentum.\nA photon's momentum comes from the energy it carries.\nE = mc^2 + pc\nWhere E is the photon's energy, m is its rest mass (= 0), c is the speed of light, and p is the momentum.\np = E / c\n\nIt is possible to use the momentum of light to move objects.  Since momentum must be conserved, a photon's momentum is transferred to the object in a collision, thereby applying a force and causing an acceleration.  The Energies (and this momentums) of single photons are very small, and thus their momentum changing effects on other objects are also very small and difficult to measure under normal circumstances.\n\nNothing with mass can ever travel at, or exceed, the speed of light.  To accelerate a mass to the speed of light it would take an infinite amount of energy, and in the entire universe, there is not an infinite amount of energy.