# Why is there no upper limit for high temperature, but absolute zero for low temperature?

2020-10-14 | Science Beauty Boy Original |

High temperature also has an upper limit. It is the initial temperature of the universe and the temperature that gave birth to the universe. Although absolute zero is the limit of low temperature, it is only a theoretical value and can never be reached. Let’s talk about what happened below:

What is absolute zero

Pour hot water into cold water, the cold water will become hot, which is called temperature change, that is, the hot water transfers part of its heat to the cold water. Let's do an experiment and drop the ink in the cold water and hot water.

Picture: hot water on the left high temperature, normal temperature water on the right low temperature.

After the hot water dripped into the ink in the experiment, the ink spreads faster, which means that the higher temperature water molecules in the beaker move faster. Temperature is a physical quantity that expresses the degree of cold and heat of the substance, but its essence is descriptionThe average kinetic energy of matter.

Simple understanding: the car is parked in front of you, and there is no threat to you at all, but if it is driving on the highway, it has high energy, which is kinetic energy.

When the molecular speed is zero, there is no kinetic energy, then the substance reaches the lowest temperature of 0K K, thermodynamic temperature unit Kelvin, that is, absolute zero, which is converted to -273.15 degrees Celsius.

Absolute zero cannot be reached

The cold Pluto, far away from the sun, can reach a minimum temperature of -248 degrees. The background temperature of space is -270.3 degrees, about 3K. When the universe was born, the temperature was extremely high, and it exploded and expanded rapidly, just likeIt is a bomb exploding, the core is hot, and as the energy spreads outward, it is released from a small space to a larger space, and the temperature gradually becomes cold.

Today, 13.8 billion years after the Big Bang, the residual temperature in the universe has cooled to 3k, which is called cosmic microwave background radiation in astronomy energy is radiated outward in the form of electromagnetic waves.

The "Bumorang Nebula" 5000 light-years away from the earth, the "polar regions" formed naturally in the universe, has a minimum temperature of -272 degrees, which is two degrees lower than the cosmic background and one degree higher than absolute zero. This is abnormal.For example, the room temperature is 20 degrees, and the water standing in the house cannot be lower than 20 degrees.

The Bumojan Nebula is a nebula formed by gas molecules expelled by a star that has evolved to the end at 164km/s. Scientists have analyzed that the space is close to a vacuum, so heat transfer is slow. The nebula will be in a vacuum under the action of internal pressure.Medium expansion. Just like the process of an explosion: the gas expands adiabatically, the volume increases, the temperature will drop, so the temperature is lower than the background temperature.

The highest record created in the laboratory is 0.5*10^-7K, but it cannot reach 0k. Because absolute zero means absolutely still, everything is relative, if you don’t move, the earth is also moving, soYou can't detect it.

In quantum mechanics, the uncertainty principle describes that you cannot measure the position and momentum of a particle at the same time. Absolute stillness means that the velocity is zero and the momentum is zero. Obviously it is impossible to exist. Therefore, absolute zero can be infinitely close.But it can never be achieved, because the basic particles that make up matter have to maintain quantum properties.

The highest temperature exists in the universe

Since motion determines the temperature, if the molecular speed is infinitely fast and the kinetic energy is infinite, the temperature can not be infinite? Since it is a substance, it must abide by the basic laws of matter, and the speed of matter has a limit.

The "Special Theory of Relativity" describes that the spread of information and energy cannot exceed the speed of light. Matter with a non-zero static mass cannot reach the speed of light and can only approach infinitely, so the temperature also has an upper limit.

In addition, everything in the universe originated from the initial hot energy eruption, so the highest temperature is to compress the entire universe back, the temperature that it had when it was extremely dense and was about to blow out.

Planck temperature

The shorter the wavelength and the greater the energy of the electromagnetic waves radiated by objects, the higher the radiation temperature. In the theory of black body radiation, physicist Planck discovered that the energy is not continuous, but one by one.Each smallest unit that cannot be divided is called quantum.

The appearance of quantum means that time and space are not continuous uncertainty principle, wave-particle duality, so Planck calculated the smallest scale of space "Planck length", and the smallest scale of time "Planck length""Gram time", and the electromagnetic wave light released during the Planck time after the Big Bang began is the first hottest energy in the universe. The wavelength of the electromagnetic wave is the Planck length and the radiation temperature is the Planck temperature., It is the highest temperature of the universe, the value is 1.41 x 10^32 K 141 billion billion billion K, unless there is another big bang, it will not reach the highest temperature of the universe.

The core temperature of the sun is about 20 million degrees Celsius. The highest human record is the European Nuclear Research Center. The "mini big bang" created by the Large Hadron Collider reached 10^13k 10 trillion K.One hundred billionth of the Runck temperature.

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