1. The reason why stars twinkle.
We see stars twinkling, not because of changes in the luminosity of the stars themselves, but because of the obstruction 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; its transparency varies depending on density. So when we look at the stars through it on the ground, we will see that the stars seem to be twinkling.
2. The reason why sunflowers always bloom toward the sun.
The stem below the sunflower disc contains a substance called auxin. This substance has the function of accelerating reproduction, but it is optically repulsive. Whenever it encounters light, it will run to the backlight side. Therefore, when the sun rises, the sunflower stems immediately hide to the backlight side, and it seems that the entire plant is bent toward the direction of the sun.
3. The reason why fireflies glow.
Fireflies can glow because they have luminescent devices at the end of their abdomens. The luminescent devices are filled with many phosphorus-containing luminescent substances and luminescent enzymes, allowing fireflies to emit flashes of light. The purpose of fireflies' light is not only for lighting, but also for courtship, warning, and trapping. This is also a tool for them to communicate. Different types of fireflies have different lighting methods, lighting frequencies and colors, and they use this to convey different messages.
4. The reason why squirrels have particularly big tails.
While the squirrel is jumping up and down the tree, its tail is doing a great job. It allows the squirrel to balance when jumping in the tree and avoid falling and being injured. In addition, this big tail can also play a protective role in winter, tightly surrounding the squirrel's body, which is both convenient and practical.
5. Reasons why leaves change color.
The reason why leaves change color is related to the chemical substance they contain - chlorophyll. When autumn comes, the days are shorter than in summer and the temperature is lower. The leaves stop producing chlorophyll, and the remaining nutrients are transported to the trunk and roots for storage. The leaves lack green chlorophyll, and at the same time, other chemical pigments appear, so we see more leaves in yellow, brown and other colors.