The Casimir force exists in all liquids

Physicists in the US have come up with research results that the Casimir force - a mysterious quantum phenomenon that can absorb two copies when they are close enough - can exist in a liquid.

The researchers found that two gold-plated surfaces submerged in ethanol would experience a gravitational pull when brought close to 200 nm, but two times weaker than the force determined in a vacuum. They say this could lead to a new effect called "quantum floatation effect", which can be used to design more accurate sensors.

First hypothesized in 1948 by Hendrik Casimir, the Casimir force occurs when two sides of two plates are brought close enough in a vacuum. According to quantum mechanics, every electronic field pushing back and forth between two plates can continuously fluctuate in intensity. At very small distances between the two plates, this field will create pressures on the average surfaces that are larger than the internal fields in the plates thus resulting in the suction of the two plates toward each other.

Figure 1. Schematic diagram of the Casimir force in an ethanol environment (Phys. Rev. A).

Jeremy Munday and Federico Capasso's team at Harvard University (USA) have shown that the Casimir force can exist when the vacuum is replaced by liquid. They attached a polystyrene sphere covered with a thin layer of gold to the top of a vibrating rod and hung in an ethanol tank and placed below it a gold-coated plane (pictured). Using a laser beam reflecting on the surface of the vibrator and recording with a photosensitive dector, the group recorded the intensity of Casimir force absorbed on the ball by changing the position of the reflected laser on the vibrator bar.

They discovered that the force can be obtained when the ball is brought close to the surface at a distance of 200 nm, and when the distance is 50 nm the attraction increases to 120 pm, 2 times smaller than the force recorded. in vacuum. According to Munday, this shows that ethanol has the effect of preventing Casimir force by changing the fluctuations of electromagnetic fields between plates.

Figure 2. The dependence of the Casimir force on distance (Phys. Rev. A).

Recently, physicists believe that the Casimir force can be used to design mechanical details, micro-mechanical components and theorists even think that it can be used to test the correctness. of Newton's law of gravitation at a distance below the millimeter scale.

Munday told PhysicsWeb: His team is assuming a form of "quantum levitation", which can be used in an environment with many different liquids that make the plate push instead of being sucked. . "Then, a plate will push the object up in the liquid," - he explains - "Because things do not have physical contact, static friction is almost destroyed, and the object is pushed up. can react with both very weak forces and allow us to create sensitive sensors or accelerometers ". These results are published in the latest issue of Physical Review A.

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According to American Physical Society & PhysicsWeb.org, Vietnam Physics