Interesting popularization of knowledge: scientific common sense will make life more interesting!

Have you ever encountered this problem: some little things in everyday life always make people think about principles behind them? Today, I'll take you to expand your knowledge and see scientific principles behind these seemingly ordinary things in life!

№1 Why is it not painful to cut nails?

Nails are made of a dead substance called cutin, so you don't feel pain when you cut your nails. However, underneath nail is a layer of tissue called nail bed, which is full of nerves and blood vessels, so if you cut too deep, it can damage nail bed and cause pain.

No.2 Why do ice cubes sizzle when added to drinks?

When ice cubes are placed in a drink, temperature of drink rises rapidly, causing surface of ice cube to melt quickly. This causes air bubbles to form on surface of ice cube, which make a hissing sound when they burst.

#3. Why does rubbing hands get warm?

When we rub our hands, force of friction generates heat and at same time stimulates blood circulation in hands, allowing blood to flow faster and more heat to be removed. That's why when we rub our hands, we feel warm.

No.4 Why does cutting onions make people cry?

When you cut an onion, its cells rupture, releasing a compound called isothioacrylate. This substance stimulates lacrimal glands in our eyes, causing tears. So wearing glasses or putting onions in freezer for a while before slicing is a great way to reduce watery eyes.

#5. Why does a faucet make a sound when it leaks?

When a faucet leaks, drops of water constantly fall on sink or ground, causing vibration. These vibrations propagate into surrounding air, creating sound waves, and we hear tick-tock-tick sound.

No.6 Why do your eyes close when you sneeze?

Sneezing is a protective reflex in which foreign objects are quickly pushed out of nasal cavity. When we sneeze, facial muscles tighten, causing eyelids to close naturally. It is also a protective mechanism that prevents foreign objects from entering eye.

No.7 Why are airplane windows round?

Windows in airplanes are round, primarily to reduce stress concentration. When an airplane flies at high altitude, fuselage is under tremendous pressure. Round windows distribute this stress better, reducing metal fatigue and stress cracking.

These interesting sciences of knowledge allow us to learn more about some phenomena in life and look at them from a scientific point of view. I hope these popular science tips add fun and knowledge to everyone's life! If you have other interesting knowledge, welcome to leave a message to share, let's expand knowledge together, and use rationality to measure the development of things!