字幕表 動画を再生する 英語字幕をプリント It's AumSum Time. Why do we have moles? To enhance our beauty. Alright. Listen. Our skin has cells called melanocytes. They give our skin its color. However sometimes, these cells tend to grow in clusters, thus forming moles. Moles can be present at birth or can appear later in life. They are usually black or brown and can be flat or raised. Some moles may even disappear with age. Usually, moles are not cancerous. But doctors have come up with a rule called ABCDE rule. Which will help you indicate whether the mole is cancerous or not. A stands for asymmetric shape, B stands for border. C stands for color, D stands for diameter and E stands for evolution. Besides this, it is believed but there is no conclusive evidence that. Excess exposure to sun-light and genetics might play a role in the formation of moles. Why do we have 5 fingers? So that we can lick our hand 5 times. A theory suggests that we have 5 fingers because, together they make a perfect strong grip. Using them, we can operate small objects with great control and precision. Second theory suggests that 3 molecules called Bmp. Wnt and Sox9 are responsible for the five fingers, since in our embryonic stage. They mark out spaces specifically for these 5 fingers. Another theory is related the Limb law. Based on the length of the fingers. This law helps us calculate the number of fingers we should have. Now. Limb's law using its mathematical model comes up with the answer 9.42 fingers per hand. But we need fingers only on 1 side of the palm as other side is connected to an arm. Hence, the final answer comes out to be 4.78. That is, 5 fingers per hand. Why do we have different time zones? Because we have different watches. No. Our earth rotates on its own axis. Due to this rotation, different parts of the earth receive different amounts of sunlight. Thus causing morning, noon, evening and night. Now, if we had one time zone, then 12 pm would be noon at some places. But it would be night or evening at other places which would be inconvenient. Hence, scientists made different time zones according to the earth's rotation. With respect to the sun. But how? The earth makes one full 360 degrees rotation in 24 hours. This means in one hour, the earth moves by 15 degrees. Using this information, scientist divided the planet into 24 sections or time zones. Each section or region was about 15 degrees wide and had a specific standard time. This helped us know the proper time of the day in that part of the earth. Why do we have different skin colors? It is because of a pigment called melanin and ultraviolet radiation of the sun. Confused? Obviously. Alright. I will explain. Millions of years ago, people living near equator received a lot of sunlight. And ultraviolet radiation. Now, ultraviolet radiation is actually absorbed by our skin to produce Vitamin D. But excess radiation can damage our skin cells. Hence, the skin of these people produced more melanin to block the excess ultraviolet radiation. Thus, overtime, these people and their succeeding generations. Adapted to have a higher level of melanin in their skin, making their skin darker. However, people living away from equator received less sunlight and less ultraviolet radiation. Hence, in order to absorb sufficient ultraviolet radiation. And produce the essential Vitamin D. These people and their following generations adapted to have a lower level of melanin. Thus making their skin lighter.