The space between the sun and the earth is so cold, why can the sun get hot when it shines on the earth?

So far, how far the sun is from the ground is mainly a guess. According to the temperature throughout the year, the sun is in spring (high), summer (low), autumn (high) and winter (high). The sun moves north and south on the earth, with moderate spring and autumn, north in summer and south in winter, and the sun moves regularly, but sometimes it is long in summer and short in winter.

The movement of solar energy in space requires conditions, that is, the specific gravity of the same unit area is lighter than air, or buoyancy appears in the air after acceleration. If the specific gravity of the sun in the same unit area is lighter than the air, then the movement of the sun in the air will encounter resistance, and the sun will move quite slowly, so it is not true that the sun in the same unit area is lighter than the air. So the sun is accelerating.

Is the sun off or not? Is the sun burning or not? If the sun is burning, there is waste and waste gas after burning, and the sun becomes smaller after burning. So far, no organization has confirmed that there is waste and waste gas after burning, and the sun has not become smaller. Since the sun doesn't burn, there is a possibility that the sun will be blocked. If the sun is closed, then the sun is transparent, because the light emitted by the closed environment can only be transparent. Modern science has not answered what indestructible material the solar shell is. If the sun burns in a closed environment, and there is exhaust gas in the closed environment, which affects transparency, the sun is still as bright as ever, so the sun does not burn in a closed environment. After the above assumptions, it is completely confirmed that the sun does not burn. Most likely, the sun is a transparent power device that emits light and heat indefinitely.

Modern science has not confirmed how high space is. From the point of view of spring, summer, autumn and winter, the sun is far from the earth, so it does not run in the highest space. It is also illuminated by the sun in the high sky above the sun. When the sun shines a certain distance above the sky, the solar heat energy gradually decreases. In the morning or evening, it is far from the ground, and the temperature is lower in the morning or evening. At noon, it is higher because the sunlight is closer to the ground.

Why is the temperature low when the sky is near the sun? And the ground is far from the sun but the temperature is high? This is because the composition of air contains not only water vapor, but also waste gas, which can be decomposed and dissociated, so there is no heat-insulating and heat-absorbing substance in the air, so the sunlight in the sky can't gather heat. On the other hand, the ground is different. It blocks the continuous penetration of sunlight. To put it bluntly, the ground is an endothermic substance. The longer the sun shines, the more heat the ground absorbs. Because the air is not insulated, the heat on the ground forms thermal diffusion. The area of heat diffusion is mainly determined by the sun. The more heat energy the sun irradiates, the lower the temperature of heat energy far away from the sun. Thermal diffusion is left and right, so thermal diffusion is limited.

The most fundamental reason lies in the atmosphere! The essence of temperature is the embodiment of the movement intensity of microscopic particles!

The more violent the movement of air molecules, the higher its temperature. And the sun shoots at the earth with various electromagnetic waves. The sunlight we usually see is only a tiny part of the electromagnetic waves sent by the sun to the earth.

The energy carrier of electromagnetic waves is photons. When photons from the sun hit air molecules on the earth, it will cause air molecules to absorb energy and intensify their movement, so the temperature will rise.

Of course, most of the solar radiation is absorbed by the earth's surface, and the electrons outside the nucleus that absorb sunlight on the earth's surface are in excited States, which will also radiate electromagnetic waves. So these electromagnetic energies are first absorbed by air molecules and then spread to outer space.

The surface of the earth is equivalent to the pot of a gas stove, and air is equivalent to the water in the pot. There are two ways to heat water at the same time.

First, sunlight directly irradiates air molecules, which intensifies the movement of microscopic particles and leads to an increase in temperature.

Second, the surface temperature is generally higher than the air temperature. Under the law of thermodynamics, a high-temperature object conducts temperature to a low-temperature problem. In fact, it is microscopic. The soil atoms on the ground radiate electromagnetic waves and then are absorbed by air molecules.

The reason why the sun shines into space is because most of the space is vacuum, and there is no matter in the empty space, so it can't absorb the electromagnetic waves emitted by the sun. If you take a random space in space, there are basically no other particles in this space except photons. Then photons cannot transfer their energy to other microscopic particles. Since there are no microscopic particles except photons, it is difficult to reflect the temperature. The temperature in space is also the intensity of photon movement in unit space, which is far less intense than that of air macromolecules.

For example, the moon, because there is no atmosphere, the sun shines directly on the surface of the moon, and its energy will not be dispersed into air molecules, but the surface of the moon will directly absorb this energy, resulting in the highest temperature reaching 160.

On the night of the moon, because there is no shielding of the atmosphere, the moon will directly radiate excess energy into outer space. The lowest temperature reaches-180.

The atmosphere is a buffer zone. When the surface temperature is high, it helps to absorb heat. At night, the atmosphere will keep some temperature, so that the ground temperature will not be too low.

The high temperature in summer is due to the direct sunlight in this area. This means that in a unit time, the sun shines more energy on this area, leading to abnormal movement of air molecules. Even at night, the violent movement of air molecules will not drop too low, resulting in hot nights in summer.

"Space is really empty" and "Space is really empty" is not a joke, the real situation is like this. To understand this problem, we should start with some basic properties of the universe.

According to the latest observation of Planck satellite, so far, the universe is flat with an accuracy of six thousandths. The "flatness" here is not on the flat ground as many people understand it, but that the universe is almost unbending on a large scale.

On this basis, scientists put forward a concept: the critical density of the universe. The so-called critical density of the universe means,

From this, we can get a formula about the critical density of the universe:

Actually, it doesn't matter if you don't know the formula. We only need to know that when the Hubble constant is above "h" and the value is 70 (km/s MPC), the corresponding critical density of the universe is P = 0.9 * 10-29 (g/cm 3). If all the substances in the universe are regarded as hydrogen atoms, the density is about 65438.

The Hubble constant H obtained from the cosmic microwave background radiation observed by Planck satellite is actually very close to 70, which means that the real density of the universe is very close to the state that there is only one hydrogen atom in a cubic meter. Therefore, space is actually very, very empty, almost close to vacuum.

Does space reflect temperature? According to the definition of temperature in classical physics:

Because of this space close to the "vacuum" state. So in fact, space can't obviously reflect the temperature, that is to say, if a person doesn't have a spacesuit in space, he won't freeze to death, but because the air pressure is too low, his body fluids will boil, or because the air pressure is too low, he will die of lung dysfunction (that is, suffocation). So the space is not too cold, but it is difficult to show the temperature.

Therefore, when sunlight passes through space, because the density of the universe is too low, the temperature is actually difficult to express. To put it bluntly, sunlight can flow smoothly in space and rarely hits molecules and atoms, which intensifies their thermal movement. There is no such thing as heating the sun.

Why can the sun transfer heat to the earth? Compared with the density of space, the material density of the earth is much larger. It is composed of a large number of molecules and atoms, which can absorb a lot of heat and make its own thermal movement intense.

Solar radiation will aggravate the molecular thermal movement of the earth, which is reflected in the macroscopic view that the earth is getting hotter and hotter. Moreover, this heat is not dissipated at once, but part of it is locked by the specific heat capacity of the earth through the atmosphere and water.

Of course, there are many ways of heating, such as thermal convection, thermal radiation and heat conduction. The main way for the sun to transfer heat from the earth is thermal radiation. When the earth distributes this heat to various places, it will use heat conduction and convection.

Not only that, because the earth has an atmosphere with sufficient thickness and reasonable composition, it can lock in some heat and will not let it dissipate quickly. Secondly, there is a lot of water on the surface of the earth. We all know that water has a large specific heat capacity, and water can also lock up a lot of heat. Based on these two factors, the temperature difference between day and night of the earth is not large.

In the solar system, the energy source of the earth is the sun. Without solar radiation, the earth might still turn, but life on the earth would be wiped out. The reason why this heat is not taken away during photon transmission is because the density of the universe is too low.

Finally, to sum up, temperature refers to the intensity of molecular thermal motion in the microscopic world. According to observation and theoretical calculation, the density of the universe is extremely low, one cubic meter is about the level of a hydrogen atom, so the temperature in space is not particularly low, but it can't reflect the temperature at all. Secondly, the density of the earth is much higher than that of space, and it is composed of a large number of molecules and atoms. So the earth has enough molecules and atoms to absorb solar radiation, which intensifies the thermal movement of its own molecules, which is also the reason why the earth can absorb solar radiation.