Physics

# Tractor Beam

A tractor beam is a device with the ability to attract one object to another from a distance. In science fiction, it is a hypothetical beam of energy that can be used to move objects such as spaceships or hold them stationary. The main challenge of building a tractor beam is pretty intuitive. When a stream of light hits an object, it tends to move in the direction that the light is. Tractor beams were generally only used at sub-warp velocities. To safely tow a vessel at warp speed, the target vessel’s engines had to be deactivated to avoid shearing forces against the towing vessel.

A tractor beam is a powerful ray or beam of energy that pulls objects into the emitter; a manipulation of the gravitational force around a selected object.

The tractor beam placed spatial stresses on the object in specific areas, allowing it to hold the “tractored” object in a fixed location or alter its position and/or trajectory. The concept originates in fiction: the term was coined by E. E. Smith (an update of his earlier “attractor beam”) in his novel Spacehounds of IPC (1931). Since the 1990s, technology and research have labored to make it a reality, and have had some success on a microscopic level.

A tractor beam is a powerful ray or beam of energy that pulls objects into the emitter; a manipulation of the gravitational force around a selected object. Less commonly, a similar beam that repels is called a pressor beam or repulsor beam. Physicists have identified a few basic ways that light can flex its muscle. Like a blast of water from a hose, a light beam exerts a tiny forward push when it hits something. Light can also pull an object, using something called the gradient force. While tractor beams were normally used to pull objects towards the beam source – usually to tow objects – conversely, they could also be set to repel objects. This force comes about because the electric and magnetic fields in the light polarize the material in the object, and the polarized object can then reduce its energy by moving to where the light is most intense. Most sonic tractor beams have a fundamental limitation that they can only levitate particles smaller than half the wavelength of the ultrasound used. The tractor beam would work in a new way. In this case, the light would pull an object toward the source of the beam even though the beam has the same intensity all along its length.

A tractor beam was an attenuated linear graviton beam used by starships and space stations to control the movement of external objects. Gravity impulse and gravity propulsion beams are traditionally areas of research from fringe physics that coincide with the concepts of the tractor and repulsor beams. The principle behind the new system is simple: Sound waves, which are waves of high and low pressure that travel through a medium such as air, produce force. This tractor beam makes use of some odd properties of light waves to pull objects along a path.