It should be understood that when the temperature reaches the order of 1.2 degrees Celsius, the ordinary temperature measurement method will be invalid. Moreover, a single measurement method can not guarantee the accuracy, so many new technical methods are needed to measure the temperature of plasma! Before that, we need to know what the temperature is.
From a macro point of view, temperature is the performance of the reaction substance. For example, we will feel cold when the temperature is low, and we will feel hot when the temperature is high, but this is one-sided. In order to understand the nature of temperature, we need to start with microscopic particles.
With the development of modern physics, the observation of microscopic particles is no longer out of reach. On June 3, 2020, Nature published a paper, indicating that scientists have successfully observed the figure of a single atom through a cryoelectron microscope. This is a revolutionary pioneering work and provides a new technical means for microscopic particle observation.
At the microscopic particle level, physicists find that all substances are composed of small particles, and these small particles are constantly moving irregularly. The faster the microscopic particles move, the higher the temperature. On the contrary, the slower the particle moves, the colder the object is.
Of course, this refers to the average speed of all molecules of an object, not the specific speed of a single particle.
Having said that, I believe everyone should understand that there can be tens of billions of degrees of high temperature in the universe, as long as the particles in matter move faster. And the temperature can't be reduced indefinitely. The lowest temperature is the absolute zero when the particles stop moving, which is generally -273.8+05℃.
Knowing the definition of temperature, we can measure it.
After most objects are heated, the random motion speed of particles will be accelerated, and the space for particle motion will become larger, so the phenomenon of "thermal expansion and cold contraction" in physics appears. Through this phenomenon, we can make tools for measuring temperature.
Mercury thermometer is a typical example, but this method also has limitations. Mercury can't keep expanding, can it? Even if it can expand, the instrument carrying mercury can't withstand the high temperature of several thousand degrees. Moreover, the higher the measured temperature, the longer the scale is needed, so the mercury thermometer can only measure the temperature around 100.
The change of object temperature will not only cause thermal expansion but also cause other phenomena. For example, hot objects can produce different infrared rays, which is the principle of our present temperature measuring gun.
Of course, this infrared method is not suitable for forging steel, and there are too many interference factors. So there is another way to measure temperature-thermocouple. The specific principle is that when an object is heated, some electrons in it will gain enough energy and then run to the "cold end" (the other end is the heated end).
The number of electrons escaping from different metals is different, and the number of electrons distributed in the cold end is also different. At this time, the temperature of the heating end can be obtained by measuring the voltage on both sides of the cold end. This method is generally used for industrial temperature measurement, which can measure higher temperature, but it has limitations. In a few cases, the high temperature of 1000 can be measured.
But this is far from the threshold of 65.438+0.2 billion high temperature measurement. If you want to measure this high temperature, you can only find another way.
It is obviously unrealistic to directly measure 65.438+0.2 billion high-temperature objects, and we must rely on the most primitive temperature theory to measure the temperature. The speed of particle motion in matter is directly reflected in the temperature of matter.
The objects that the artificial sun emits heat are plasma, specifically electrons and ions. Simply put, measuring the temperature of plasma means measuring the speed of electrons and ions. What we want to build is not a thermometer, but a particle velocimeter.
Here is a microscopic particle velocimeter that everyone can understand. Its principle is the same as the speedometer used by traffic police, and it is measured by Doppler effect.
In this method, a laser beam is emitted to the plasma, and the laser interacts with the moving electrons, which will produce the scattering of laser light. By receiving the scattered laser and comparing it with the incident laser, we can find out the frequency affected by the speed of the electron itself, and then we can get the speed of the electron and the temperature of the substance through calculation.
Of course, the temperature measured by Doppler effect is not necessarily accurate, and many other temperature measurement methods are needed to draw a conclusion. This is due to the rigorous consideration of science and one of the most effective methods.
# Temperature #