What are the sights in the sky such as the moon, the sun and constellations?

Scenes in the sky, such as the moon, the sun and constellations, are illusions. Because air refracts. When people observe that the sun and the moon have just risen, the thickness of the atmosphere they pass through is different from that of the sun and the moon in the future.

"Scenes in the sky" such as the moon, the sun and constellations always make people feel bigger when they are close to the horizon than when they rise high. If you take pictures of them or measure them with an astronomical telescope, it can be proved that no matter how high they rise or how close they are to the horizon, their size has not changed much.

Strictly speaking, due to the influence of atmospheric refraction near the horizon, the moon or the sun will be slightly flat, but the total area will be slightly smaller than that after rising to the sky. So "the moon on the horizon is bigger" should be an illusion.

The moon, sun, constellations and other scenes in the sky are as follows:

1, cloud. Cloud is a visible polymer floating in the air, which is condensed by small water droplets or small ice crystals liquefied by water vapor in the atmosphere when it is cold. The sun shines on the surface of the earth, and water evaporates to form water vapor. Once the water vapor is supersaturated, water molecules will gather around the dust (condensation nucleus) in the air, and the generated water droplets or ice crystals will scatter sunlight in all directions, thus creating the appearance of clouds.

2. Rainbow

When the sun shines on the water droplets in mid-air, the light is refracted and reflected, forming an arched colorful spectrum in the sky, which is red, orange, yellow, green, blue, indigo and purple in turn from the outer ring to the inner ring. In fact, rainbows have countless colors. For example, there are many subtle differences between red and orange, but for simplicity, only seven colors are used as the differences.