We went to the moon using just Newton’s laws of motion and gravity. Newtonian dynamics we call it. So then we find out, “Well, this works because there’s certain regimes we’ve never tested it in.” Had we done so, we would show that it didn’t work: For example, at very high speeds, very high gravity, Newton’s laws fail. They just fail. You need Einstein’s laws of motion and gravity. Those would be his special theory of relativity and general theory of relativity. Now you invoke those and it works.
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DOWN AND UP
Isaac Newton and the DogWalk
Said gravity to water droplet ?
? I will force you down?
Said droplet to earth ?
?You may shudder with the fall?
Said earth to water
?I will spread you in my womb?
Said water to the roots
?I will move up inside you?
Said Time to Winter
?You are going down?
Said Time to Spring
?Time to come up?
Said tree to itself
?Time to grow up and bud?
Said bud to husk
?Release me so I can grow up?
Said gravity to husk
?You are going to fall down?
Said spider to the tree
?Hold my web, so I do not fall?
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Newton’s third law is: For every action, there is an equal and opposite reaction.