The Federation has built tractor beams into most cargo bays of their starships and space stations, just in case a shuttle or small craft is damaged and has to be towed. Isn't it awesome of the Federation to be so practical? And isn't it sad that we don't have starships like they have? But cheer up ... we might just be GETTING their tractor beams.
Scientists in China and Hong Kong have recently written about conditions that would make a tractor beam possible.
We already know that, because of radiation pressure, light can be used as a source of propulsion: In 2010 the Japanese successful launched a spacecraft, the ship IKAROS, based on solar sail technology; according to Wikipedia, IKAROS passed Venus in six and a half months.
But pulling? That's a different level of complexity.
New Scientist broke it down for us:
The researchers showed that by measuring the shape of an object and its electromagnetic properties, you can predict these currents - and, in turn, the properties of the resulting secondary photons.
It should then be possible to create a beam with just the right properties that when it is shone at a particular particle, photons emitted from the particle's far side push on the particle with more force than those photons that are reflected back. In principle, this could be used to pull a particle all the way back to the beam's source, the researchers say.
There's no news on when we can see practical applications of a tractor beam. But if we do, we hope it can tug our shuttle back to our starship.