We see the stars shining, not because the luminosity of the stars has changed, but because of the occlusion of the atmosphere. The atmosphere is between us and the stars. When starlight passes through the atmosphere, it will be affected by the density and thickness of the atmosphere. The atmosphere is not absolutely transparent, and its transparency will change according to its density. So when we look at the stars through it on the ground, we will see that the stars seem to be flashing.
2. The reason why sunflowers always bloom towards the sun.
The stem under the sunflower disk contains a substance called auxin. This substance has the function of accelerating replication, but it is anti-optical, and it will run to the backlight side whenever it encounters light. So when the sun rises, the stem of the sunflower immediately hides to the side of the backlight, as if the whole plant is bent in the direction of the sun.
3. The reason why fireflies shine.
Fireflies emit light because there is a luminous body at the end of their abdomen, which is filled with a lot of phosphorus-containing luminescent substances and luminescent enzymes, so that fireflies can emit flashing light. The purpose of fireflies is not only lighting, but also courtship, vigilance and trapping. This is also a communication tool for them. Different kinds of fireflies emit light in different ways, frequencies and colors, so they can convey different information.
4. The reason why the squirrel's tail is so big.
When the squirrel jumps around the tree, its tail plays a great role. It can keep balance when the squirrel jumps to the tree to avoid falling and being injured. In addition, this big tail can play a more protective role in winter, tightly surrounding the squirrel's body, which is convenient and practical.
5. The reason why leaves change color.
The reason why leaves change color is related to the chemical substance chlorophyll. When autumn comes, the days are shorter and the temperature is lower than that in summer, so the leaves stop producing chlorophyll, and the remaining nutrients are transported to the trunk and roots for storage. Leaves lack green chlorophyll and other chemical pigments appear at the same time, so we often see yellow and brown leaves.