# Why does the temperature have a lower limit of minus 273.15 degrees Celsius, but not a clear upper limit?

This paper takes part in the series essay competition of “great science” of Recordunkown.

13.8 billion years ago, a singularity with infinitely large mass and infinitely small volume exploded, and then the universe was born. After the big bang, countless celestial bodies and other kinds of materials were born. At the same time, many cosmic laws and physical quantities were also born. For example, when the big bang happened, the physical quantity of temperature appeared.

I believe you are not unfamiliar with the word temperature. We are dealing with it all the time. In ancient times, people could only feel the temperature, but could not give a specific definition of temperature. Until mankind entered the era of science and technology, scientists provided a human definition of temperature. Since then, there has been a standard to measure the temperature.

There are upper limit and lower limit values for the temperature defined by human beings. I believe many friends know that the temperature can not be reduced infinitely. It has a limit value, which is absolute zero, that is minus 273.15 ℃. Although this is a lower limit of temperature, there is no temperature that can reach this value. Why?

All this needs to be explained from the essential change of temperature. Scientists have found that the reason for the change of temperature is actually the internal molecular thermal motion. When the molecular motion in the object becomes more and more intense, the temperature will continue to rise, and when the molecular motion becomes lower and lower, the temperature will continue to fall.

There is a lower limit for the motion activity of atoms and molecules, which is static. When the molecular motion stops completely, there is no motion. At this point, the temperature reaches its lower limit, which is absolute zero. But we all know that the motion of molecules can not be stopped, so absolute zero is only a temperature in theory, which is impossible in reality.

Does infinite temperature close to absolute zero exist in reality? Of course, there is. For example, the temperature of the cosmic background radiation is about 270 degrees below zero, close to absolute zero. Before human beings entered the era of science and technology, we can see that the temperature close to absolute zero can only appear in the universe, such as the background temperature of the universe, and the surface temperature of celestial bodies far away from the edge of the sun is close to absolute zero.

However, when human beings enter the era of science and technology, the power of science and technology makes many impossibilities become possible. For example, the temperature is infinitely close to absolute zero. At present, human beings can produce a low temperature of minus 273 ℃ by evaporation of liquid nitrogen, which is infinitely close to absolute zero. Even in the universe, such a low temperature has not been found. But it was made by scientists in the laboratory, and maybe this record will be broken in the future.

Now we know that the temperature has a lower limit of absolute zero, so some people have a new question: since the temperature has a lower limit, does it have an upper limit? Many people once said that there is no upper limit to the temperature, which can rise infinitely in theory. This is because there is no upper limit on the intensity of thermal motion of molecules. Is that true? Of course not.

Since temperature can have a theoretical lower limit of absolute zero, there will naturally be an upper limit of temperature, which is the theoretical Planck temperature. Compared with the lower limit of temperature, which is only minus 273.15 degrees Celsius, the theoretical upper limit of temperature is very high, about 100 million degrees Celsius. This is what kind of high temperature value, simple beyond people’s imagination.

Why is there a theoretical upper limit for temperature? The answer to this question is still to go back to the thermal motion of molecules. Many people will say that the minimum thermal motion of molecules is static, and there is no upper limit for the maximum. However, Einstein’s theory of relativity tells us that any mass material can only move infinitely close to the speed of light and can not reach it.

Molecules naturally have mass, and there is a limit to the intensity of their thermal motion, that is, the speed of light. Theoretically, when its motion reaches the speed of light, the temperature of the object reaches the upper limit, which is the Planck temperature. Maybe someone will say, what if the divided motion exceeds the speed of light? If the speed of molecules exceeds the speed of light, it violates the existing laws of physics.

Although the temperature has the upper limit of Planck’s temperature, it is difficult for us to approach the temperature infinitely. Scientists have now achieved an ultra-low temperature of minus 273 degrees Celsius in the laboratory, which is infinitely close to absolute zero. However, the highest temperature that humans can achieve in the laboratory is only 510 million degrees Celsius. This temperature is infinitely far away from the theoretical upper limit.

Thus, it can be seen that it is relatively easy to reduce the temperature infinitely close to absolute zero, but it may be extremely difficult to increase the temperature infinitely close to the Planck temperature. The increasing temperature value is of extraordinary significance to human beings. Some people may not understand that if the temperature is reduced to close to absolute zero, the human body freezing technology can be realized, and human beings can achieve a long period of dormancy. So what’s the point of raising the temperature infinitely close to the Planck temperature?

As a matter of fact, scientists have the highest expectations for the research on the rising temperature, because the rising temperature can enable us to realize controllable nuclear fusion technology first, which is a major breakthrough in energy. Once realized, human civilization will enter a new stage, which can directly upgrade an industrial era and enter a new era of Industrial Science and technology.

According to Einstein’s mass energy equation, temperature and matter can be transformed into each other. But in the real world, all we can see is the transformation of matter into energy, but we have never seen energy transform matter. The reason is actually very simple, because the energy level required for energy to transform into matter is too high, far beyond the current scientific and technological strength and cognition of human beings.

Temperature is the most powerful energy in the universe. As long as the temperature is infinitely high, it can create everything. Before the big bang, there was a singularity. There was no matter or celestial body in the singularity, but only infinite energy. When the big bang happened, the Planck temperature was produced in an instant. Such a high temperature energy realized the process of transforming energy into matter, so all kinds of matter began to be born, and now we see the wonderful universe.

Therefore, scientists believe that the Planck temperature may have only appeared in the big bang, which created everything. So theoretically, if human beings can achieve high temperature energy infinitely close to the Planck temperature in the future, we can also achieve the mode of energy transforming into matter. At that time, all kinds of materials, such as gold, minerals and other resources, could be realized through energy conversion, just like the production of materials out of thin air, without a long process of material formation and evolution.

If human beings can realize such ultra-high temperature energy one day in the future, in a sense, human beings will be the God of the universe. Because the creation of all things out of thin air is no different from that of God. Even one day, we will be able to create a new universe, which many people think is impossible. But the development of science and technology is to make many impossible possible. As long as we keep the temperature close to the upper limit, all these are possible. We are looking forward to this day.

Guys, what do you think of this? Welcome to leave a message below to discuss and express your opinions.

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