President john kennedy and president ronald reagan both visited the berlin wall in order to?

President Ronald Reagan challenges Soviet Leader Mikhail Gorbachev to “tear down” the Berlin Wall, a symbol of the repressive Communist era in a divided Germany.

Newton 

july 5, 1687, isaac newton published work, in which he presented a coherent theory of gravity describes both falling objects on the ground as well as the movement of celestial bodies. english physicist relied on their proposed terms of dynamics and kepler's laws on the distance of the planet from the sun.