Scientists have built a macroscopic tractor beam using laser light: ScienceAlert

Scientists have built a macroscopic tractor beam using laser light: ScienceAlert

Tractor beams make intuitive sense. Matter and energy interact with each other in countless ways throughout the Universe. Magnetism and gravity are both natural forces that can pull objects together, so there is some sort of precedent.

But designing an actual tractor beam is something different.

A tractor beam is a device that can move an object from a distance. The idea comes from a 1931 sci-fi story called IPC’s SpaceHounds:

“There’s a beam screen, you kill-joy, and there’s the lift or tractor beams – two things I’ve been trying to get rid of and you’ve given.
I cheer myself up Bronx. The Titans have had a tractor beam for centuries – he sent me full drugs on it – and the Jovians took them both. We’ll get them in three days, and it should be pretty simple to remove the opposite of a tractor as well—a thruster or pressure beam.”

If science fiction had anything to say about it, tractor beams would already be commonplace and we could thank Star Trek and Star Wars for their proliferation.

But tractor beams already exist, although their range is only microscopic.

Microscopic tractor phases are used in devices called optical tweezers. Optical tweezers use lasers to move microscopic objects like atoms and nanoparticles. They are used in biology, nanotechnology and medicine.

These tractor beams work on microscopic objects, but are not powerful enough to pull larger macroscopic objects.

Now, a team of researchers has successfully demonstrated a macroscopic tractor beam. They published the paper explaining their work in the journal Optics Express. Its title is “Knudsen force-based macroscopic laser shooting in rarefied gas,” and the lead author is Lei Wang of QingDao University of Science and Technology in China.

“In previous studies, the pulling force of light was too small to pull a macroscopic object,” Wang said.

“With our new approach, the pulling force of the light has a much larger amplitude. In fact, it is over three orders of magnitude greater than the light pressure used to drive a solar sail, which uses the momentum of photons to exert a small thrust. force.”


This macroscopic tractor beam only works under certain laboratory conditions, so it is a demonstration, not a practical development. At least not yet.

First, it works on purpose-built stuff: macroscopic graphene-SiO2 composite objects that researchers have built for experiments.

Second, it operates in a rarefied gaseous environment, which has a much lower pressure than Earth’s atmosphere. While this limits their effectiveness here on Earth, not every world has as much atmospheric pressure as our planet.

“Our technique provides a non-contact and long-range shooting approach that can be useful for various scientific experiments,” Wang said.

“The rarefied gas environment we used to demonstrate the technique is similar to that found on Mars. Therefore, it could have the potential to one day handle vehicles or aircraft on Mars.”

Their device works on the principle of gas heating. A laser heats composite objects, but one side is hotter than the other. The gas molecules behind get more energy, which drags the object. Combined with the lower pressure in the rarefied gas environment, the object moves.

The researchers built a device with a torsion – or rotation – pendulum made of graphene-SiO22 composite structure to demonstrate the laser firing phenomenon. That demonstration made it visible to the naked eye. They used another device to measure the effect.

“We found that the pulling force was more than three orders of magnitude higher than the light pressure,” Wang said. “In addition, the firing of the laser is repeatable and the force can be adjusted by changing the power of the laser.”

Other researchers have addressed tractor beams in recent years with mixed results. NASA was interested in pursuing the idea of ​​using tractor beams to collect samples with the MSL Curiosity surface rover. One of Curiosity’s instruments is ChemCam.

It includes a laser that vaporizes the rock or regolith and then a micro imager to measure its components spectroscopically. But NASA wondered if a tractor beam could draw tiny particles from the vaporized sample into the rover for a more complete study.

A 2010 NASA NIAC presentation said: “If Tractor Beam Technology was incorporated into a ‘ChemCam2’ to shoot dust and plasma particles, tractor beams could add a suite of additional science capabilities:

  • laser desorption ion spectroscopy
  • mass spectrometry
  • RAMAN spectroscopy
  • X-ray fluorescence”

The same presentation said the tractor beams could be used to collect particles from comet tails, ice plumes from Enceladus, and even clouds from Earth’s atmosphere or other atmospheres.

This never materialized, but it illustrates how compelling the idea is.

This new research has produced interesting results, although it is nowhere near a real practical implementation. A lot of work and engineering is needed before this comes close to being practical.

First, there must be a well-understood theoretical basis that describes how the effect works on objects of different sizes and shapes and with lasers of different powers in different atmospheres.

The researchers know this, of course, but point out that it is still an effective demonstration of feasibility.

“Our work demonstrates that flexible light manipulation of a macroscopic object is feasible when the interactions between light, object and environment are carefully controlled,” Wang said.

“It also shows the complexity of laser-matter interactions and that many phenomena are far from being understood at both the macro and micro scales.”

The critical part is that this study moves tractor beams from the microscopic to the macroscopic. This is a significant threshold, difficult to cross.

“This work extends the scope of optical pulling from the microscale to the macroscale, which has great potential in macroscale optical manipulations,” the authors write in their conclusion.

Spaceships may well use tractor beams one day, but they’re unlikely to look like they do in science fiction. Star Wars, Star Trekand SIPC pacehounds all have tractor beams in battle and conflict.

But in reality, they could prove to be valuable scientific tools.

This article was originally published by Universe Today. Read the original article.

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