The temperature of the sun's surface is 5500 degrees, and the earth is all hot. Why is space cold?

We all know that almost all the energy of the earth comes from the sun. The surface of the sun has reached 5500 degrees and is 150 million kilometers away from the earth, but it can heat up the earth, then the question comes, why is space aCold?

Today, let's talk about this problem.

Where does the temperature of the sun come from?

In fact, we have to start with the sun. The sun is the largest celestial body in the solar system. This "large" is not only reflected in the volume of the sun, but also in its mass. It occupies the entire solar system 99.86% Quality.

Because of the huge mass of the sun, the temperature and pressure of the sun ’s core rise sharply under the influence of gravity, which can reach 15 million degrees and more than 2 million standard atmospheric pressures. This makes the sun not our common gaseous state,Solid or liquid. Because the electrons get enough energy, the electrons are free from the nucleus of the atomic nucleus. Therefore, the interior of the sun is actually a state where particles are scattered around, including electrons, nuclei, photons, etc. This state is also called by usIs plasma.

Under the blessing of the quantum tunneling effect and weak interaction, nuclear fusion reactions can occur between hydrogen nuclei and hydrogen nuclei to produce helium nuclei, and they occur slowly. This stage can last 10 billion years, not likeThe hydrogen bomb exploded like that.

In the process of nuclear fusion in the sun's core, for every 3 photons generated, 2 neutrinos will be generated, and the neutrinos will propagate directly. The earth will be penetrated by a large number of solar neutrinos at any moment.Ever.

Because the sun is in a plasma state, when photons are generated by the sun's core, the photons will need to bump to reach the surface of the sun due to the existence of electromagnetic interactions, and eventually run to the vast universe. From the sun's core to the surface of the sun, there areSome scientists estimate that it takes an average of 140,000 years, and it takes only 8 minutes and 20 seconds from the surface of the sun to the earth.

Is space absolutely zero?

You must know that the distance between the sun and the earth is more than 200 times the radius of the sun. The universe space over the entire distance between the sun and the earth is actually close to absolute zero, but not absolute zero. In preparation, the true temperature of space is close to2.72K, which is 2.72 degrees higher than absolute zero. Why is this the case?

We all know that the universe originated from a big bang. After the big bang, the temperature of the universe was extremely high. At the same time, the universe was expanding violently, and the temperature was falling as the space expanded.

The early universe was a bit similar to the state of the sun. It was a pot of particle soup. The photon was similar to the situation in the sun. There was no way to get trapped in this pot of particle soup. Later, as the temperature dropped to 2700 degreesThat is 380,000 years after the Big Bang. At this time, electrons and nuclei form the completed atomic structure, and photons also begin to travel through the universe. As the universe continues to expand, the universe continues to cool, and this temperature is actuallyResidual temperature during the Big Bang.

So far, this residual temperature has dropped to 2.72K, which is background radiation throughout the day. Therefore, we also call it cosmic microwave background radiation. Today, scientists can also observe it by various methods, and can also stepObserve the data step by step and iterate continuously.

Because of the existence of cosmic microwave background radiation, the temperature in space should be the temperature of the cosmic microwave background radiation. However, if you really take that thermometer, you will be disappointed because the thermometer will not show the number at all. That problemWhere on earth is it?

To understand this problem, we must first understand: what exactly is the temperature? Or, we should actually figure out: what exactly is the heat?

From a microscopic perspective, the essence of temperature is actually the intensity of the thermal movement of microscopic particles. We all know that everything is composed of particles. Particles are not actually arranged neatly. InsteadDisorganized in motion.

Scientists have discovered that the higher the temperature of an object, the more intense the thermal movement of the particles that make up the object as a whole.

However, there is a premise here, that is to show the temperature in the macro, in fact, it needs to be built on "enough number of particles." Without sufficient number of particles, the temperature will actually be difficult to show.

And space is really empty. According to the latest detection results of Planck satellites, the universe is flat on a large scale, and we can calculate the average density of the universe through cosmological theory. At present, the universe ’sThe average density is about 0.9 * 10 ^ -29g / cm ^ 3. The density of air must be 1.293g / cm ^ 3, which means that the difference between the two is 10 ^ 29, 29 orders of magnitude. How exaggerated is it??

This is probably the level of only one hydrogen atom in one cubic meter. Therefore, space is almost close to a vacuum state. Therefore, space can not reflect any temperature. In other words, if someone is unfortunately not wearing a spacesuitIn the case of exposure to space, he will not be frozen to death, but should be strangled.

How does the sun transmit "heat" to the earth?

Knowing this, we will understand that because space is close to a vacuum state, photons generated by the sun will basically not encounter any obstacles in the process of crossing the universe. When these photons are as low as the earth, the earthIt is a celestial body that is much denser than space and is composed of a large number of material particles. Therefore, the photons generated by the sun can be directly used by the earth and converted into the kinetic energy of the thermal motion of the particles.

When the earth's place is illuminated by the sun, the thermal movement of the particles becomes fierce, and the temperature in this place also becomes higher. Therefore, it is precisely because the density of matter in space is too low that the "light" of the sun canIt is directly transmitted to the earth, and the reason why the earth can be heated is that the earth has enough material particles.