Background
For science fiction enthusiasts, the tractor beam will always hold some fascination. Now with the findings of a group of scientists, this dream may well become a reality in the days to come.
Scientists in China feel that they have unraveled the mystery of tractor beams. The key to this is that a backward pulling force should be created rather than a pushing one.
The Theory
Researchers of the Fudan University have met with considerable success in tractor beam research on a nano scale. The theory is based on the fact that photons tend to exert an outer momentum. What happens is that a kind of “solar sail” is produced which harnesses sunlight for the generation of a small thrust. Under certain conditions, the push can be converted into a pull. The conditions are as follows:
The outward momentum propagation should be very small.
Many multipoles exist within a certain target particles. These must be excited simultaneously.
When the beam’s angle is just right, the momentum can be converted from a positive thrust to a negative thrust.
This is the principle of a tractor beam.
Even though the force created is not spectacular, but it brings in exciting possibilities in the design and manufacture of optical systems.
