Scientists have created an ultrasensitive torque detector that could measure a counterintuitive quantum effect called vacuum friction. While we may think of a vacuum as being truly empty and therefore frictionless, physicists have theorized that friction is possible in a vacuum. Now, a laser-based detector could prove whether the theory is true.
A Few Contradictory Definitions
Friction is the force that resists the relative motion of one thing against another. Or, in more technical terms, friction “corresponds to wasted energy and therefore determines the efficiency and useful lifetime of all moving systems, from biological to aeronautical,” according to Science Advances.
In the simplest terms, a vacuum is a space without matter (remember, air is matter — it’s just not very dense). Scientists can create a vacuum on Earth by using a vacuum pump to remove the air from a sealed container or by reducing the pressure using a fast flow of fluid, according to Britannica.
Given these definitions, the idea of vacuum friction doesn’t make sense. How can friction exist in a frictionless environment?
Vacuum friction is a quantum effect where an object spinning in a vacuum experiences drag even though it’s surrounded by nothingness, according to Science News. Why? Scientists suggest that even when there isn’t any matter present, drag can be caused by the ever-present electromagnetic fields that constantly appear and disappear. It would be great to confirm this weird quantum effect, but it would be so subtle and on such a small scale that it’s extremely difficult to measure.
Torque Detector to the Rescue
A team of physicists at Purdue University may have the answer. Phys.org reports that the Purdue scientists built the world’s most sensitive torque measuring device. They suspended a speck of twirling dust in a laser beam inside a vacuum. Then they used another laser to alternate the torque and test its sensitivity. The device is made of a silica nanoparticle (that’s the dust) suspended inside of a vacuum chamber by a laser beam. The physicists fired a pulsating, circularly polarized laser beam at the nanoparticle for 100 seconds at a time. This made the particle spin 300 billion times per minute, making it the fastest human-made rotor in the world.
According to Science News, the torque detector can measure tiny twisting forces, and it is the most sensitive torque detector ever — 700 times as sensitive as the next best sensor. Just how sensitive is it? In the lab, the sensor could measure torques as tiny as 0.4 trillionths of a quadrillionth of a newton-meter, a unit of torque. For context, Science News explains that it takes about one newton-meter of torque to twist a cap off a soda bottle.
Quantum Mechanics in Practice
According to the researchers at Purdue, the nano-torque detector will help measure and investigate several aspects of quantum theory. Not only will it help unveil vacuum friction, but it could also measure other related effects. It could eventually measure the Casmir effect and nanoscale magnetism. With a better understanding of these quantum effects in the future, engineers could use them to develop and control nanoelectronic devices.