What is the legendary "absolute zero"?

Absolute zero is a concept that has intrigued countless people. We have all heard of this temperature, but we know very little about its specific value and meaning. What is this mysterious absolute zero? What strange phenomena will occur at such an extremely low temperature? Today, let us unveil the mystery of absolute zero and find out.

Absolute Zero

Absolute zero refers to the temperature of an object at zero Kelvin, or -273.15 degrees Celsius. It is the lowest limit of temperature and is considered an important benchmark in disciplines such as thermodynamics and statistical mechanics. This concept was first proposed by British physicist William Thomson and discovered by Dutch physicist Heike Onslow in the late 19th century. The temperature of absolute zero is 0K, which means that the average kinetic energy of all molecules of a substance is zero, which means that the substance no longer has temperature or thermal energy. When the temperature of a substance approaches absolute zero, the properties of the substance will undergo very strange and mysterious changes. For example, when helium liquid approaches absolute zero, it will become a mysterious substance called a superfluid, which has zero viscosity and infinite heat transfer capacity, while metals will exhibit superconducting properties when they approach absolute zero, and electrons can conduct freely in the metal. This has led to the emergence of a large number of new research fields such as lossless refrigeration, high-speed circuits, and strong magnetic fields in recent years, which have been widely used in many fields such as experimental physics, quantum computing, and biomedicine.

Although absolute zero is the theoretical limit, humans cannot cool objects to this temperature because it violates the third law of thermodynamics, which states that no object can be cooled to absolute zero in a finite number of steps.

Changes at absolute zero

At the molecular level, absolute zero marks the end of all thermal motion. At this extremely low temperature, the thermal vibration of molecules almost stops, and the vibration and rotation of atoms and molecules almost disappear. In this situation, the molecular structure of matter becomes extremely stable, allowing the atoms or molecules of condensed matter to be closer to each other, forming a special state of matter. For example, superfluids and superconductors lose their original properties, such as viscosity and resistance, at a certain temperature. They can flow without friction or resistance.

These phenomena only occur at extremely low temperatures and are closely related to the slowing down of molecular thermal motion and quantum effects. At absolute zero, some bosons may gather at the same energy level, a phenomenon known as Bose-Einstein condensation. This is a unique quantum phenomenon that reveals the possibility of new states of matter and has important implications for quantum physics and potential applications.

In addition, although the average kinetic energy of molecules at absolute zero is close to zero, they still vibrate slightly in the form of quantum fluctuations. This tiny vibration has a profound impact on the properties and structure of matter and is one of the basic phenomena of quantum mechanics.

Finally, some insulators may become conductors at sufficiently low temperatures, a phenomenon known as the insulator-to-conductor transition. At absolute zero, the vibrations of atoms virtually disappear, allowing electrons to move freely in the lattice, resulting in conductivity.

In general, absolute zero is not only an important concept in natural science, but also a gateway to explore the quantum world. At this extreme temperature, matter exhibits many unique and surprising properties. These properties not only deepen our understanding of nature, but also provide endless possibilities for scientific and technological innovation.

Absolute zero cannot be reached

At the edge of the solar system, icy Pluto orbits the sun alone, with surface temperatures sometimes dropping to -248 degrees Celsius. However, when we look up into the depths of the universe, we find that it's even colder there than Pluto. The background temperature of space is as low as -270.3 degrees Celsius, a temperature scientists call 3K. When the universe was born, it was extremely hot, and then it underwent a rapid expansion process, like a bomb exploding, with the core temperature gradually dropping as energy spread. Over time, the remaining heat in space cooled to what we call today the cosmic microwave background radiation, which is the result of energy radiating outward in the form of electromagnetic waves.

5,000 light years away from the Earth, there is a celestial body called the "Bomerang Nebula". This is a naturally formed "pole" of the universe, with the lowest temperature reaching minus 272 degrees, two degrees lower than the background temperature of the universe. However, this is not a normal phenomenon. Scientists analyzed that space is close to a vacuum, so the speed of heat transfer is very slow. The Boomerang Nebula is a nebula formed by gas molecules thrown outward at a speed of 164 kilometers per second by a star that has evolved to its final stage. When these nebulae expand under the pressure inside, it is like an explosion: the gas expands adiabatically, the volume increases, and the temperature drops, so its temperature is lower than the background temperature. Although humans have created the highest record of 0.5×10^(-7)K in the laboratory, this temperature cannot reach absolute zero.

Absolute zero means absolute stillness, and according to the uncertainty principle in quantum mechanics, we cannot measure the position and momentum of a particle at the same time. If a particle is absolutely still, then its speed and momentum are both zero, which is obviously impossible. Therefore, absolute zero can be infinitely close, but it can never be reached. This is because the basic particles that make up matter must maintain their quantum properties.

The highest temperature in the universe

The highest temperature of the universe is an unimaginable number, which was generated by the moment of the Big Bang. At this temperature, all matter and energy gathered in a very small space, forming the initial state of the universe. In the moment after the Big Bang, the temperature of the universe rose rapidly, reaching a value that we cannot imagine.

Scientists have calculated that within seconds of the universe's birth, its temperature reached a trillion degrees. This temperature was so high that all matter was broken down into its most basic particles, including protons, neutrons, and electrons. As the universe expanded and cooled, these basic particles began to gather together to form atoms and molecules. In this process, the temperature of the universe gradually dropped, eventually reaching the normal temperature we know today. Although we cannot directly measure the maximum temperature of the universe, scientists infer this value by observing the cosmic microwave background radiation.

The cosmic microwave background radiation is the residual heat left after the Big Bang. It is spread throughout the universe and provides scientists with an important tool to peek into the early state of the universe. By analyzing the data of the cosmic microwave background radiation, scientists have concluded that the maximum temperature of the universe is about 300 billion degrees. This temperature has dropped a lot compared to the instantaneous temperature at the Big Bang, but it is still a very high value.

In short, the highest temperature of the universe is generated by the instant of the Big Bang, which is an unimaginable number. Although we cannot directly measure this value, we can infer its approximate range by observing the cosmic microwave background radiation. The existence and evolution of this temperature provides important clues for our understanding of the origin and evolution of the universe.

At absolute zero, would light be frozen into a stick or a wave?

First of all, we have to make it clear that absolute zero is currently unattainable, so this experiment can only be imagined. From a realistic point of view, atoms at absolute zero should be in an "absolutely static" state. If light intervenes, the atoms in the light will break this static state. In simple terms, light brings moving atoms, and these moving atoms will break the static state and make it heat up, and then it is no longer absolute zero.

When we make theoretical conjectures, we can imagine what form light, which is known as the "fastest light in the universe", will take when it is "frozen". If you were to guess, would you support light becoming a "stick" or a "wave"? If it is a stick, this perception is mainly based on geometric optics. In middle school physics class, the most common phrase the teacher said was "light travels in a straight line". Therefore, many people think that if the light emitted in this way is frozen at absolute zero, it will definitely become a straight "stick".

What if it is in the form of waves? This is based on the "wave theory" of light. Newton, who first proposed that light is a particle, used relevant experiments to prove his view. But later, after discussing with Newton, Huygens believed that light should be a "wave". In the "wave theory" of light, it is believed that light is essentially a "mechanical wave", so everyone thinks that light will become a wave because they think this statement is more credible. It is worth mentioning that according to the propagation theory of light waves, what may be frozen is not just "one wave" but "several waves".

In addition, regarding what light is, Einstein combined the two controversial views of particles and waves, proposing that light has the dual nature of waves and particles. Indeed, in the century-long debate, neither of these two views can completely prove that the other is wrong. It is better to "take the essence and discard the dross" and then cleverly combine them to come up with a correct theory.

In summary, the different perceptions of light by the public are the main reason for the change in its "form". Of course, all this is achieved in theory. If you really want to do this experiment in reality, there is no way. First of all, absolute zero cannot be reached. Secondly, even if there is a way to reach this temperature, the form of light will be affected by other factors and cannot remain stable. Therefore, this experiment can only be imagined. This is like a game without a referee. Even if you win, it may be judged invalid for some reason.

However, this does not stop us from trying to explore and discover more interesting things. You can imagine that in addition to the common stick and wave shapes, there are many other interesting shapes waiting for our discovery. In fact, when scientists explore the wonderful world of absolute zero in depth, they find many amazing sights. For example, in an ultra-low temperature environment, those invisible gases will turn into a "magic fluid". These wonderful discoveries make us believe that there are still many unknowns in this world waiting for us to explore and discover.

Wonders of the ultra-low temperature world

Gases are ubiquitous in our lives, but are often overlooked. Just like air, we breathe it every day, but we cannot describe its "appearance", we only know that it surrounds us all the time. However, when scientists continue to lower the temperature in their experiments, these invisible gases begin to show their forms, like a "magic mirror". Take air as an example, when the temperature drops to more than minus 190 degrees Celsius, the air will turn into a light blue liquid. What's even more amazing is that if you break off a flower and put it in liquid air, it will turn into a "glass flower" and its texture will become hard and brittle.

Of course, if the temperature continues to drop, the state of the gas will change again. Take oxygen as an example. At a temperature close to absolute zero, oxygen will become like "granules" and its color will also change to white. These changes in gases are already amazing.

Next, let's talk about the changes of metals in ultra-low temperature environments. The mercury in the thermometer becomes extremely hard and cannot flow in a low temperature environment. This means that the "mercury thermometer" we usually use cannot measure ultra-low temperatures. Steel, which is usually very strong in real life, becomes fragile in a low temperature environment. In real life, it is difficult for people to break stainless steel appliances at home, and they will not break even if their appearance changes. But in an ultra-low temperature environment, stainless steel products become as fragile as ceramic bowls, and they will "break" with a slight touch.

We have discovered many amazing things in the process of exploring absolute zero. Although absolute zero is still a theoretical limit, through its exploration and research, we can have a deeper understanding of the nature and laws of the world. With the advancement of science and technology, our exploration of the value of -273.15℃ is becoming more and more in-depth. (Picture from the Internet)

Author | Kiwi

Graduated from Lincoln University, New Zealand, with a major in finance. Has a strong interest in popular science knowledge and has published popular science articles in many popular science journals. Focuses on facts and actively explores cutting-edge technology.