Physistri

We know that if a body is moving or at rest, therefore their are atleast four forces working on it. And this is only reason why airplane stay in air ? Same here,  four forces keep an airplane in the sky. They are lift, weight, thrust and drag.Lift pushes the airplane up. The way air moves around the wings gives the airplane lift. The shape of the wings helps with lift, too.Weight is the force that pulls the airplane toward Earth. Airplanes are built so that their weight is spread from front to back. This keeps the airplane balanced.Thrust is the force that moves the airplane forward. Engines give thrust to airplanes. Sometimes an engine turns a propeller. Sometimes it is a jet engine. It doesn't matter as long as air keeps going over the wings.Drag slows the airplane. You can feel drag when you walk against a strong wind. Airplanes are designed to let air pass around them with less drag. An airplane flies when all four forces work together. But, most airplanes need one more thing: ...

As we know that the ancients thought that the moon produced its own light. After many researches, now we know that the light coming from the moon is the sunlight reflected by its surface that acts somehow like a mirror but a bad one.Since it reflects only 12% of sunlight . We see reflected light only. 

As we know that moon does not have it's own light. It reflects the light of sun. So, the shape of the moon depends on the part that is lighted from the sun.Since Earth, sound and the moon are connected. It's 265.25 days for earth to rotate the sun and 27.32 days for moon to orbit earth.But we only see half of the moon(one face)which is always illuminated by the sun.The proportion of the illuminated part visible to us varies from 0% (new moon) to 100% (full moon). Related Questions :- Why moon has no atmosphere ? why does moon shine ?

Moon has no atmosphere because of it's  escape  velocity. The escape velocity of moon is very less as compare to earth and other planets. Ex:- Escape velocity of moon is 2.3 km/s whereas the escape velocity of hydrogen is 5 km/s which is approx two times of moon's escape velocity. As we know hydrogen is the smallest element. Therefore, the molecules (hydrogen and others) will escape from the moon and therefore moon cannot hold an atmosphere.                      Related Questions :-                Why does moon changes it's shape every night ? why does moon shine ?