What? Why? How?

1. Why do the stars twinkle at night?

It's the atmospheric refraction due to which the starlight gets bent towards the normal when it passes through the dense atmosphere. Since the density of the atmosphere is not the same everywhere so the extent of refraction keeps on changing. Stars being far away from the earth look like point sized objects and as the path of light coming from them keeps on changing so their apparent position also keeps on fluctuating due to which the stars sometimes appear brighter and at times fainter. This phenomenon makes the stars look like they are twinkling.

 

2. Why do we shiver when we are nervous?

It's because when we come across a new or unexpected situation which we haven't faced before, our adrenaline gland responds by pumping adrenaline hormone into our bloodstream to respond to that situation. Our body shakes because our mind is contemplating as to how to handle the sudden unexpected situation; whether to stand ground or run away. This action triggered by adrenaline glands is called the fight or flight reaction.

3. Why do the fans have curved blades?

Fans have curved blades to increase the air circulation. The curved blades move the air faster towards one side of the spinning blades thereby increasing the air pressure on that side. This difference in air pressure makes the air move downwards.

4. Why are raindrops spherical in shape?

Raindrops take up the spherical shape due to the surface tension of water which is caused due to the tendency of water molecules to stick together. The spherical shape is having the least possible surface area due to which it can resist any of the external force in the atmosphere.