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Vacuum is not "empty"! Scientists may have discovered a fourth mode of heat transfer.
Release time:
2021-01-12 11:43
We all know that there are three main ways of heat transfer in real life: convection, conduction, and radiation. In a vacuum, however, heat cannot be transferred due to the absence of a medium.
For example, when we use a vacuum-insulated thermos to maintain the temperature of water, we may know that it is a good insulator because heat energy has difficulty passing through the empty space. If there are no atoms or molecules around, the vibrations of the atoms or molecules carrying heat energy cannot propagate at all.
Recently, scientists at the University of California, Berkeley published a study in the journal Nature that is enough to rewrite our textbooks again.
Middle school textbooks state that sound cannot propagate in a vacuum. In fact, sound is essentially a wave produced by molecular vibrations, which also generates energy, and heat energy is one of them.
This research found that sound can actually propagate in a vacuum; in fact, a vacuum is not 'empty'. The generated heat energy can cross a complete vacuum of hundreds of nanometers.
Is it that the experimental facts are problematic, or that our commonly accepted textbooks have errors? What substance causes this phenomenon?
The phenomenon discovered this time involves a quantum mechanical phenomenon called the Casimir effect. So what is the Casimir effect?
Assuming there are two parallel flat metal plates in a vacuum, the space between the plates is limited compared to the outside, so the number of particles between them will be less than outside the plates, and the pressure generated by the collisions of these particles on the plates will be greater outside than inside, causing the parallel plates to be subjected to a compressive force applied by the vacuum.
Some say that there is no medium in a vacuum, so where do the particles come from? According to quantum mechanics, there are many particles with measurable effects in a vacuum, which are called virtual particles. Virtual particles are the micro-particles that make up virtual matter, closely related to real particles, distributed around real particles, and have similar properties to real particles.
In the experiment, the research team placed two gold-plated silicon nitride films a few hundred nanometers apart in a vacuum chamber. When one film was heated, the other film also became warm—even though nothing connected the two films, and the light energy passing between them was negligible.
The researchers found that by carefully selecting the size and design of the films, heat energy could be transferred across hundreds of nanometers of vacuum. This distance is far enough that other possible modes of heat transfer can be ignored—for example, the energy carried by electromagnetic radiation, which is how energy from the sun warms the Earth.
Although this interaction is only meaningful over very short length scales, it could have profound implications for the design of computer chips and other nanoscale electronic components where heat dissipation is critical. The discovery of this new heat transfer mechanism opens up unprecedented opportunities for nanoscale thermal management, which is also very important for high-speed computing and data storage.
Scientists say that since molecular vibrations are also the basis of the sounds we hear, this discovery suggests that sound can also propagate through a vacuum. Phonons can indeed transfer through invisible quantum fluctuations in a vacuum. Quantum fluctuations may become a new way of heat transfer.
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