Is pulling objects with light possible? How far away are we from tractor beams?

It is a known fact that light has the ability to push objects away. This is used in the concept of solar sails, which I explained in the first post on this blog.

In a new development though, researchers from Hong-Kong and China have calculated what is needed for a laser to pull instead of push. This can not be achieved with normal lasers, instead the researchers used what is known as a Bessel beam. They have a few rather unusual properties, for example they can re-assemble themselves. With conventional lasers, if you place an obstruction in their path they stop, whereas Bessel beams continue behind the object.
This allows the energy of the beam to be precisely controlled, and allows them to place more energy behind an object than in front of it, pushing it towards the source of the beam.

A close up, head on, view of a Bessel beam. (Credit: California Institute of Technology)

Rather than in science fiction however the effect is only predicted to occur over small distances, and will therefore mainly impact particle science. We unfortunately won't be able to use this to levitate or pull enemy space ships into our hangar, but it is fascinating none the less.

"Light can indeed pull a particle," the researchers wrote.