TELL ME WHY?

Why Do Wet Fabric Appear Darker?

        When fabric gets wet, light coming towards it refracts within the water, carrying the light  through the material instead of reflecting it back to your eye. Since  more of the light goes through the material, less of the light is reflected back to the eye, making the wet fabric appear darker.

 Why Sound Cannot Be Heard In Space?

               Like Light, sound travels in waves. White light travels through vacuum, but sound cannot. Sound energy moves through vibration. Part of the instrument making the noise vibrates (moves backward and forward quickly). This in turn pushes against the air, causing the air molecules to collide, thus transferring the sound energy from molecule to molecule away from its source, until it reaches our ears. Sound needs matter to travel. But space is silent. So there are no molecules for the sound waves to vibrate.

Why Does A Rocket Have Stages? 

             A rocket needs enormous power to escape from Earth's gravity. The velocity required to achieve this is called the escape velocity ( about 29,000 mph/ 49,000 kph). The rocket's power comes from burning liquid hydrogen and oxygen. Each stage of a rocket is a fuel tank, which is jettisoned when its fuel is used up. After all, carrying on empty fuel tank will only use up more fuel. Only the top stage of the rocket, called the payload, makes the whole journey and brings the crew back to Earth.

Why Do We Find It Difficult To Breathe At The Top Of A Mountain? 
            

              Most of the gases in our planet's atmosphere are concentrated fairly close to sea level. The higher you go, the lesser the gases. That is why people talk about the air "becoming thinner" at high altitudes. There is less oxygen, making it difficult to breathe. Mountaineers usually wear oxygen masks as they approach the summits of the world's highest mountains.