Hayke Kamalin Hones is a Dutch physicist. As early as 1908, he and his colleagues in the laboratory to condense helium into a liquid, the first realization of helium liquefaction, in the study, hones he found that when the temperature dropped below 4.2 K, that is, -269 degrees Celsius, the resistance of mercury will suddenly disappear, at first, he thought it was a strange phenomenon of mercury, he later found. Lead also has this phenomenon, he realized that at low temperatures, the thermal movement of some substances disappears, the resistance wireless is close to 0, he called such a phenomenon superconducting phenomenon, then the superconducting state of the object is a superconductor.
The nature of temperature
Temperature is everywhere and is closely related to human daily life. However, the concept of temperature has been unclear for a long time in the past. Natural philosophers like Galileo and Newton believed that heat was a "flow," while others believed that "cold" was caused by "cooling atoms." At the same time, the measurement of temperature is also confusing. The earliest and most reliable thermometers were designed according to the principle of thermal expansion of liquids. People limit the liquid in a glass ball or glass tube, fixing two immobile points, such as boiling point and freezing point, and then placing a scale between them to indicate the location of the liquid surface. In this way, the so-called "temperature" is displayed between these two points, which at that time was called "heat". In the first half of the 18th century, the German Daniel Gabriel warrenheit and the Swede Anders schylseuss established the Fahrenheit and Celsius temperatures, respectively. These two methods of representing temperature have been used until now.
However, the use of liquids to measure temperature depends on the physical properties of the substance, which is only a relative description of the so-called "cold" and "hot". In the mid-19th century, the British physicist William Thomson tried to define temperature without relying on any single material property, so he established the thermodynamic temperature scale in 1848. This temperature scale has become the standard temperature scale of modern science, called the absolute temperature scale. In 1892, the British government promoted Thomson to Lord Kelvin, so the ruler was also known as the Kelvin ruler, in K.
But what is the temperature? This problem has not been solved. Only when people understand the truth that matter is made of atoms can they get the answer. Now we know that what is called heat is actually kinetic energy produced by the movement of atoms; the so-called temperature is a measure of atomic velocity. In other words, temperature is actually the motion of atoms inside an object. When we feel the "heat" of an object, its atoms move very fast; when we feel that the object is "cold", its atoms move slowly. With this understanding, it is not difficult to understand what a state "absolute zero" is: it is a very quiet state inside an object. In this state, the movement of the atoms stops completely.
So, the next question must be: at "absolute zero", that is, what is the temperature of the atom when matter is completely at rest?
The never-ending "absolute zero"
In the 17th century, the Frenchman Guillaume Armonden discovered that the air pressure sealed inside the vessel decreased with the temperature of the air inside the vessel. Armmonton observed that when air dropped from the boiling point to the freezing point, the pressure inside the vessel dropped by about 4/1. Amunden speculated that if the air continued to cool, at some point, the pressure would disappear completely. At this point, there should be no way to lower the temperature, that is, it has reached "absolute zero". According to Ammonton's calculations at the time, this "absolute zero" was about minus 300 degrees. Now it seems that Ammonton's guess is not entirely correct. Today, "absolute zero" as defined on the absolute temperature scale is equivalent to -273.15 °C.
The establishment of "absolute zero" is equivalent to setting a "benchmark" in front of scientists. Whoever approaches it first wins the title of science. By the end of the 19th century, the race for "absolute zero" had officially begun.
However, although the road to the "benchmark" is already in sight, it is difficult to achieve "absolute zero" completely. This is because the method of manufacturing low temperatures is similar to the operation of a refrigerator. After the refrigerator wall comes into contact with a colder substance such as circulating refrigerant, heat is brought to the refrigerant, which cools the inside of the refrigerator. If you want to take away all the heat from an object and bring it to "absolute zero", you have to use a substance that is lower than "absolute zero". Could it be that the atoms in this material move so slowly, even slower than "stationary"? "Absolute zero" means that the atoms are completely at rest, and the volume of the gas should be zero, but this does not happen. However, the state of "absolute zero" can never be achieved, only infinitely close to it.
In the refrigerator, the refrigerant cools while expanding, and as the pressure drops, the movement of the molecules inside the refrigerant slows down. In the "absolute zero" competition, people adopt this method from the beginning. At that time, one gas after another is compressed and then rapidly expanding. This process not only lowers the temperature, but also condenses the gas into a liquid. In the late 1870s, the Frenchman Louis Paul Cayette used this method to obtain liquid oxygen at minus 183 °C and liquid nitrogen at minus 196 °C. In 1898, Scotsman James Dewar obtained liquid hydrogen at minus 250°C. After that, all that's left is helium. Ems's atoms were loosely connected and were the most difficult gases to liquefy, but Ennis did. This is the scene described at the beginning of the article: he discovered the phenomenon of superconductivity.
But that's not the end of it. What happened next was even more surprising. In general, helium nuclei contain two neutrons and two protons, so the most common form of helium atoms is helium-4. When the temperature drops to 3.2K, a lighter atom appears. It is helium-3, which is 1000 times thinner than helium-4. Helium-3 has only one neutron. Once liquefied, it "behaves" completely differently from helium-4. It's hard to imagine how the physical properties of liquid helium without neutrons would be different. As the temperature continues to drop to 2.17 k, the liquid helium on the surface of the bubble suddenly disappears and the liquid becomes unusually calm. How some liquid helium has entered a whole new state: it is completely sticky, frictionless, it can flow infinitely, it can easily pass through microtubules, it can pass through gaps that even gases cannot pass through unimpeded. This is superfluidic. In this state, no matter which part of the liquid becomes hot or bubbles appear, it takes away the heat and prevents the formation of bubbles, which is why the surface of liquid helium becomes so calm.
Adventures in the cryogenic world
What do these strange phenomena mean? It turns out that we live in a world that can be described by quantum mechanics, which can only be clearly felt in a world of low temperatures.
The study of quantum phenomena is also an important reason for people's desire to reach absolute zero. However, staying close to absolute zero has become extremely difficult. Even if there is a slight cooling, there will be unimaginable difficulties. For example, a 1 square centimeter copper coin has a temperature of 0.001K, a butterfly falls on the coin from a height of only 10 centimeters, and the heat generated by the butterfly "hitting" the coin is enough to raise the temperature of the coin by a factor of 100.
What should I do? People have thought of ways to collide photons in lasers with atoms in gas. Collisions take away some of the atom's kinetic energy, slowing them down. Essentially, it still relies on other substances to dissipate heat, but the "coolant" used is very different. It becomes more subtle and magical.
These advances soon paid off, giving people a rare opportunity to explore the behavior of matter controlled by quantum mechanics. For example, at low temperatures, the mass of the quasiparticle produced by the interaction between electrons can be thousands of times the mass of the free electron. Their "behavior" is very similar to that of the predicted particle, majora Fermions, which is thought to play an important role in the data processing of future quantum computers. Scientists can also use a controlled, purely quantum, supercooled material environment to simulate extreme conditions inside neutron stars, the interactions of elementary particles, and the earliest evolutionary processes of the universe since its birth. As our understanding of the cryogenic world deepens, such miracles will continue to occur, transporting us to a new, wonderful physical world.
At first, the temperature of the universe was astonishingly high in the instant after the Big Bang, reaching tens of trillions of Kelvin. The surface temperature of the Sun is 5800 K. When a star explodes, the temperature can reach 6 billion K. Explosions of supermassive stars and collisions of neutron stars are very hot. People know from observations of gamma-ray bursts that these processes can produce temperatures as high as 1 megacal. However, the universe has a surprising "two-sidedness." Elsewhere, after 13.7 billion years of cooling, the weather was unusually cold. Now scientists know that the cosmic microwave background radiation is 2.7K, but 2.7K is not the coldest. Located about 5,000 light-years from Earth, the Bomolyan Nebula is very cold, with a temperature of only 1 K. You might think there's no colder place in the universe, but beyond that, there's a much colder place on Earth, hidden in a human cryogenic lab where scientists set the low temperature there to be only 0.00000001 K higher than "absolute zero," a record that is being broken.