The photos taken from the moon are all non-luminous substances. How did the moonlight come from?

As we all know, not long ago, Chang 'e IV, which landed on the back of the moon, took photos of the moon and sent them back to Earth through the Queqiao relay satellite. As can be seen from the photo, there is no light source on the surface of the moon. But on earth, we can see the shining moon, which is the same as the principle that we can see things during the day on earth.

The moon's surface is made of rocks and dust, and it doesn't shine itself, just like the earth. So the phase of the moon we see is the part of the moon that reflects sunlight. Starting from the new moon, the phase change order of a lunar month is: new moon, first quarter moon, hope moon and last quarter moon. In the lunar month, the time from the new moon is called the monthly order, such as 14 days. Before and after the new moon, the sunshine surface of the moon seen from the earth is crescent-shaped, and half a moon wheel can be seen when it is bent, while before and after the moon, the sunshine part of the moon is convex. The first quarter moon is different from the last quarter moon because when it bends, it is located in the western half of its moon wheel when viewed from the earth, and when it bends, it is located in the eastern half.

As the moon moves a long distance from west to east in the starry sky every day, its shape is constantly changing. This is the phase change of the moon, called the moon phase. In astronomy, the moon phase refers to the part of the moon that is illuminated by the sun as seen from the earth. The sun is a star. When the sun shines on the moon, the uneven surface of the moon becomes diffuse reflection, so that people can see the bright moon instead of the moon itself.

We can see objects because visible light brings the information of objects into our eyes and the brain can perceive them. Except for the light source, other objects themselves do not emit visible light. However, an object can reflect light from a light source. Therefore, when the sun shines on an object or the moon, the surface of the object or the moon will reflect visible light. If our eyes can receive these visible light, we can see these objects. Whether it's the moonlight of the earth at night or the glare of Chang 'e IV on the back of the moon, it's the sunlight reflected from the surface of the moon.

In physics, the concept of light is very broad, which is a general term for electromagnetic waves of various wavelengths. Humans can only see some bands of electromagnetic waves, which are called visible light. In addition, there are electromagnetic waves shorter or longer than visible light, all of which are invisible light, for example, radio waves for communication and X-rays for medical imaging.

It should be noted that neither the surface of the moon nor the objects on the earth will emit light, and the light here refers to visible light. In fact, everything can shine, but light is invisible to the naked eye. Human and animal bodies also radiate light, mainly infrared rays with a longer wavelength than visible light. Using this principle, an infrared night vision device can be made, and people or animals can be seen even at night without visible light.

In addition, due to different wavelengths, some substances have different blocking abilities to visible light and infrared light. Black garbage belt can block visible light, but it can't block infrared light. Planets, such as solid planets and gas planets, have no thermonuclear reaction, so they don't emit light. Nebulae are composed of gas and dust, some of which emit light and some of which do not. If the emission nebula is bright, there are usually a large number of stars in or near such a nebula. These stars may or may not have been born from these nebulae. But all the substances in these nebulae are excited by the intense radiation of these stars and emit colored light. The main component of this nebula is hydrogen, and the light emitted by hydrogen is red when it is excited, so the nebula we see is usually red. ?