Why does the universe have a minimum temperature, but high temperatures can be infinite?

Speaking of object temperature, it is the most familiar but also the most unfamiliar concept to everyone. What is familiar is that we watch the weather forecast every day to see the highest and lowest temperatures of the day to decide what to wear the next day. clothes. During this epidemic, we need to measure our body temperature when entering and exiting the community, and we also know clearly what is the acceptable range of body temperature.

In most people’s conventional understanding, there should be no limit to temperature, and the highest and lowest temperatures can be infinite. However, the actual situation is far from this. The universe has temperature limits, and the lowest temperature is absolute zero. (0k), which is -273.15 degrees Celsius. According to the current scientific system, the maximum temperature also has a limit. We can call it the Planck temperature, which is about 1.42x10^32 degrees, which is the commonly seen data of 1.42 trillion trillion billion degrees.

To understand the high and low temperature limits of the universe, we must first clearly understand the concept of temperature. From a macro perspective, temperature is a physical quantity that measures the hot and cold state of an object. From a micro perspective, it represents the molecular heat of an object. The intensity of motion, or more accurately, the average kinetic energy of molecular motion. When the microscopic molecules move more violently, the temperature value displayed by the object is higher.

The next temperature limit is easy to understand. The average kinetic energy of molecular motion can be viewed from another perspective, that is, the speed of molecules. Under normal understanding, molecules can be stationary, and the fastest speed is the speed of light. Then according to this definition, the temperature limit can appear. But this is actually not correct, because molecules cannot be at rest, and at the same time, they cannot be at the speed of light. According to the limitations of Einstein’s special theory of relativity, objects with rest mass can never reach the speed of light, although molecules are microscopic particles with very small masses. , but still has rest mass.

Secondly, molecules cannot be completely still. This can be seen from the perspective of quantum mechanics. A very core concept in quantum mechanics is the uncertainty principle or the uncertainty principle, which can be easily understood. That is, we cannot grasp the position and momentum of microscopic quanta at the same time. They can only be expressed through probabilities. For example, we cannot say that a quantum is at point A, we can only say what the probability is that it is at point A. Then the same microscopic particle cannot be completely still. In that case, the position and momentum are determined, which directly overturns quantum mechanics.

So from a thermodynamic point of view, when the average kinetic energy of microscopic particles reduces to the lowest point allowed by quantum mechanics, the temperature of the object reaches absolute zero, which is -273.15 degrees Celsius (0k). But the lowest point of this theory cannot be reached, so absolute zero is also a theoretical value, which can only be infinitely close, but cannot reach absolute zero.

Now that we understand the minimum temperature limit of the universe, let’s continue to look at the maximum temperature limit of the universe. I mentioned earlier that the speed of light is the speed of microscopic particles, and that is the temperature limit, but this cannot be understood here. There should be no limit to the maximum temperature of the universe, but it becomes meaningless beyond a certain value.

Currently, the origin of the universe is believed to be the Big Bang at the singularity 13.8 billion years ago. After that, the universe continued to expand to become what it is today. Theoretically speaking, as the universe expands, the temperature gradually increases. decreases, then the temperature should be the highest at the moment after the Big Bang. We call it the Planck temperature. The value calculated by scientists is 1.4 trillion trillion billion degrees Celsius.

Why is it called the Planck temperature? Because according to the point of view of quantum mechanics, at the moment of the Big Bang we can accurately measure the time to 10^-43 seconds, which is the minimum span of time. We call it Planck time, so after this time span The temperature is the maximum temperature limit, the Planck temperature. In fact, we can also consider it from another perspective. If the temperature of the object is higher than the Planck temperature, then it will radiate electromagnetic waves with a wavelength smaller than the Planck length. However, currently the Planck length is the minimum length with practical significance. Anything less than this length is meaningless under the current scientific system.

So far we have not found a phenomenon that breaks the limits of the highest and lowest temperatures of the universe. The lowest temperature scientists have discovered in the universe is 1k (-272.15 degrees Celsius), which comes from the Boomerang Nebula. This nebula Located 5,000 light years from Earth in the constellation Centauri. Scientists analyze that the reason for such a low temperature is that the nebula underwent adiabatic expansion in its early stages, and the gas rapidly expanded to the outside, so the temperature dropped sharply.

It can be said that the current temperature limit of the universe is not set by anyone, but is derived under our current scientific system. The temperature below absolute zero and above the Planck temperature are not determined by current science. It is meaningless under the system, and no such situation has been found in real life.

Article/Science Black Hole, picture source is network intrusion and deletion.