A working tractor beam? In science fiction the idea of a tractor beam, an invisible or at least non-physical energy-based attractive connection, is used as a plot device. A space ship might “lock on” to another ship or to an object with this technology in order to tow it or otherwise move it. You may be surprised to learn that a working tractor beam was experimentally demonstrated by the team of David B. Ruffner and David G. Grier at the Dept. of Physics and Center for Soft Matter Research (NY). The results were announced online 10/22/2012. The official paper title is “Optical Conveyors: A Class of Active Tractor Beams“.
How does it work? A YouTube video had a few clues:
Tractor Beams May Actually Work: NASA Studying 3 Methods – YouTube
Although light manipulation techniques have existed since the 1970s, researchers said of the 2012 work that it was the first time a light beam had been used to draw objects towards the light source. As that time, the technique had only been effective at a microscopic level. (Irish Examiner)
If you thought of cows being levitated by UFOs when you saw that spiral suction beam, you are not alone. Could there be a real lifting beam that could work on heavy objects? It would be quite surprising. The force of light to move things is not known to be very strong.
The paper on PhysOrg answers this question to some degree about scaling it up. It states:
The tractor beam the two built would require far too much energy to scale up to allow for moving large objects, and likely would destroy those objects in the process if such a device were built. But it does suggest that such a device might be possible using another less energy intensive source.
In 2018 scientists were able to levitate a two centimeter polystyrene ball using spinning sound waves. Unfortunately for these researchers, there are no living species of super light two centimeter high cows, at least currently. Also, as far at this concept working in space, it would not. There is not air in space with which to transmit sound waves.
How much does the average cow weigh? A quick search says the answer is about 1 ton, or 1,500 lbs. There should be some extra power built-in, so we will assume that a flying saucer should have a 3,000 lb capable tractor beam for the effective levitation of cows.
So far as we know, the technology to levitate a cow up to a space ship does not exist, but we hope it will be discovered one day. A good tractor beam would be useful to rescue stranded cows, for example, and to solve many problems from medicine to manufacturing as well