第一天表达积累
1 be at rest
2 it followed that
3 work out all the laws that govern the universe by pure thought
4 to check by observation
6 So no one until Galileo bothered to see
7 the leaning tower of Pisa
8 do something equivalent
9 indicate
10 let go of a ball
11 a feather is slowed down by air resistance
12 to set it moving
13 This idea was first stated explicitly in
14 This states that the body will accelerate, or change its speed, at a rate that is proportional to the force.
15 According to Newton’s second law, these two effects will exactly cancel each other, so the acceleration will be the same in all cases.
16 Newton’s law of gravity also tells us that
17 This law predicts the orbits of the earth, the moon, and the planets with great accuracy.
18In particular, he thought that the earth was at rest.
19 One could equally well say that body A was at rest and body B was moving at constant speed with respect to body A, or that body B was at rest and body A was moving.
20 If one carried out experiments with moving bodies on the train, all Newton’s laws would still hold.
