1. Newton's laws of motion
Newton's first law: whenever a body is not acted on by any force, it will keep on moving in a straight line at the same speed. 力是改变物体运动状态的原因，孤立质点保持静止或做匀速直线运动。
Newton's second law: the body will accelerate, or change its speed, at a rate that is proportional to the force. The acceleration is also smaller the greater the mass (or quantity of matter) of the body. 物体加速度的大小跟作用力成正比，跟物体的质量成反比。
Newton's third law: for every action there is an equal and opposite reaction. 相互作用的两个物体之间的作用力和反作用力总是大小相等，方向相反，作用在同一条直线上。
2. This law predicts the orbits of the earth, the moon, and the planets with great accuracy. If the law were that the gravitational attraction of a star went down faster or increased more rapidly with distance, the orbits of the planets would not be elliptical, they would either spiral in to the sun or escape from the sun.
the law指前文牛顿提出的行星之间的万有引力与距离的平方成反比的定律。这个定律极其精确地预言了地球、月球和其他行星的轨道，如果这定律变为行星的万有引力随距离减小的比这还快，则行星轨道不再是椭圆的，他们会以螺旋形的轨迹靠近太阳；如果万有引力减小的更慢，则行星可能脱离地球。
3. Aristotle believed in a preferred state of rest, which any body would take up if it were not driven by some force Or impulse.
preferred: 倾向的，更乐意接受的
take up：采取
亚里士多德坚信任何物体在不受外力或冲击的时候，将更乐意采取静止的状态。
4. He observed that the times at which the moons of Jupiter appeared to pass behind Jupiter were not evenly spaced, as one would expect if the moons went round Jupiter at a constant rate.
他观察到，木星的月球不是等时间间隔的从木星背后出现，这不同于如果月球以很定速度绕木星运动时人们所预料的那样。
5. Shorter wavelengths are known as microwaves (a few centimeters) or infrared (more than a ten-thousandth of a centimeter). Visible light has a wavelength of between only forty and eighty millionths of a centimeter. Even shorter wavelengths are known as ultraviolet, X rays, and gamma rays.
关于光谱（spectrum）：
波长>1m：无线电波（radio waves）
700nm<波长<1m : 红外线和微波（infrared and microwaves）
400nm<波长<700nm: 可见光（visible light）
波长<400nm：紫外线（ultraviolet），X射线，γ射线
6. "empty" space
真空
7. at right angles to that motion
在运动的垂直方向
8. a hitherto unknown clerk
以为迄当时为止还不知名的职员
hitherto:迄今，直到某时
9. theory of relativity
the laws of science should be the same for all freely moving observers, no matter what their speed. 不管观察者以何种速率做自由运动，科学定律都应该是一致的。
10. it has revolutionized our ideas of space and time.
它变革了我们队空间和时间的观念
11. It is a matter of common experience that...
我们通常的经验是……
12. One would not specify the position of the moon in terms of miles north and miles west of Piccadilly Circus and feet above sea level. Instead, one might describe it in terms of distance from the sun, distance from the plane of the orbits of the planets, and the angle between the line joining the moon to the sun and the line joining the sun to a nearby star such as Alpha Centauri.
人们不是按照在伦敦皮卡迪利广场以北和以西多少英里以及高于海平面多少英尺来确定月亮的位置，而是用其离开太阳、离开行星轨迹的距离以及月亮与太阳连线和太阳与邻近的一个恒星（比如比邻星）的连线夹角来描述。（这个例子是为了证明坐标系是可以变化的）
13. the diagonal line
对角线
diagonal matrix: 对角阵
14. If one stacks snapshots of the ripples at different times one above the other, the expanding circle of ripples will mark out a cone whose tip is at the place and time at which the stone hit the water.
如果将三维模型设想为二维的池塘水面加一维的时间，这些扩散的水波就组成了一个圆锥，其顶点就是石头击打水面的位置和时间。
15. the special theory of relativity
狭义相对论：the speed of light appears the same to all observers，describing what happens when things move at speeds close to the speed of light. 光速不变
16. the general theory of relativity
广义相对论:gravity is not a force like other forces, but is a consequence of the fact that space-time is not flat. bodies always follow straight lines in four-dimensional space-time, but they nevertheless appear to us to move along curved paths in our three-dimensional space.
17. hail
noun: a shout or call to attract attention
e.g. They answered the hail of the marooned boaters.
verb: to acclaim; approve enthusiastically歌颂
e.g. The crowds hailed the conquerors. They hailed the recent advances in medicine.
18. Their measurement had been sheer luck.
noun: a thin, diaphanous material, as chiffon or voile.透明薄纱
adj: transparently thin; diaphanous, as some fabrics;unmixed with anything else;
adv: clear; completely; quite
e.g. ran sheer into the thick of battle.
19. curvature
the act of curving or the state of being curved.弯曲，曲率
e.g. curvature of the spine.
20. notion
noun:
1. an opinion, view, or belief
e.g. That's his notion, not mine.
2. conception or idea
e.g. his notion of democracy.
3. a fanciful or foolish idea; whim
e.g. She had a notion to swim in the winter.
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