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HERO OF UNIVERSE

 


 Newton law says, every object in the universe attract every other object by gravitational force.  Scientist Cavendish proved that two lead balls attract each other using torsion balance experiment.  He also measured the universal gravitational constant G using that experiment.  The gravitational force is the weakest one but a long range force. 

      Gravitational force is responsible for the formation of galaxies, stars and planets.  It keeps planets revolving around the sun and satellites around the planets.

      On launching, a rocket must reach the speed of 11.2 km/sec.  Then only it can pierce out of earth's gravitational field(escape velocity).  Even if the speed is slightly less, it will fall back to the earth due to gravity.

      Once out of the gravitational field, everything start to float.  Astronaut can sleep in any position since there is no gravity and consequently there is no up and down.  But they have to strap themselves to the walls of the space station otherwise they will drift during the sleep.  On earth, gravity keeps us and other objects firm on the ground.

      The value of G is 6.673*10^-11 N m^2 Kg^-2.  Actually, it is the gravitational force between two one kg masses separated by a distance of 1 m.  We can write this force also as 0.00000000006673N.  So this force is negligible and unmeasurable.  But even the force exerted by the earth on an apple is 1 newton.  G is called universal constant because it is applicable universally.  G helped as to calculate the mass of the earth as given below
.
M = g*R^2/G
M - mass of the earth.
R- radius of the earth.
G - gravitational constant
g- acceleration due to gravity.
Answer M= 5.972*10^24 Kg

      Gravitational force plays the role 'in the ball stroked by the cricket bat' and also 'in the motion of comets around the sun'.  

      Ocean tides are caused by the moon's gravitational pull.

      It is proved that the path of the light coming from the stars is altered by the sun's gravity.  The celestial object black hole is massive dead star with enormous gravity.  So it sucks in everything including light.
   So gravitational force is the evergreen hero of the universe
.
Science Update:  Wireless tech based on infrared rays offers 40 GBps download speed.
                       
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