Before them people believed Aristotle, who said that the natural state of a body was to be at rest and that it moved only if driven by a force or impulse.

be at rest: 静止；休息；安眠  

反义词：move

impluse: N-VAR An impulseis a sudden desire to do something. 冲动 ; a reason or aim that causes a particular kind of activity or behaviour推动力 e.g. It is the passions which provide the main impulse of music.

force: N-VAR In physics, a force is the pulling or pushing effect that something has on something else.(物理学中的) 力  e.g. ...the Earth's gravitational force.

这是分为外力和内力？

The story is almost certainly untrue, but Galileo did do something equivalent: he rolled balls of different weights down a smooth slope.

untrue: ADJ If a statement or idea isuntrue, it is false and not based on facts. 不真实的; 没有事实根据的 e.g. The allegations were completely untrue.

近义词: impossible, unreal

同根词: untruth N.  untruthful ADJ If someone is untruthful or if they say untruthful things, they are dishonest and say things that they know are not true. (人、话语)不真实的

lead weight: 铅坠；吊锤

In Galileo’s experiments, as a body rolled down the slope it was always acted on by the same force (its weight), and the effect was to make it constantly speed up.

act on: have an effect起作用 [I]to have an effect or use 起作用 e.g. Disinfectants act on bacteria in two main ways.

近意替换：drive, pull

This states that the body will accelerate, or change its speed, at a rate that is proportional to the force.

proportional: ADJ If one amount is proportional to another, the two amounts increase and decrease at the same rate so there is always the same relationship between them. (与…) 成比例的  e.g. Loss of weight is directly proportional to the rate at which the disease is progressing.

For example, the acceleration is twice as great if the force is twice as great.

twice as great: 两倍大  great: ADJ Great means large in amount or degree. (数量或程度) 大的  e.g. Benjamin Britten did not live to a great age.

The acceleration is also smaller the greater the mass (or quantity of matter) of the body.

为什么没有than？

According to Newton’s second law, these two effects will exactly cancel each other, so the acceleration will be the same in all cases.

力相互抵消，用cancel

elliptical：ADJSomething that iselliptical has the shape of an ellipse. 椭圆形的

If one carried out experiments with moving bodies on the train, all Newton’s laws would still hold.

hold: V-I If an argument or theory holds, it is true or valid, even after close examination. (论点、理论等) 站得住脚 e.g. Today, most people think that argument no longer holds.

For instance, playing Ping-Pong on the train, one would find that the ball obeyed Newton’s laws just like a ball on a table by the track.

符合规律用obey，违反可以用against

“I refute it thus!”

refute: V-TI f you refute an argument or accusation, you say that it is not true. 否认  e.g. Isabelle is quick to refute any suggestion of intellectual snobbery.

Maxwell’s equations predicted that there could be wavelike disturbances in the combined electromagnetic field, and that these would travel at a fixed speed, like ripples on a pond.

disturbance: N-UNCOUNT Disturbance means upsetting or disorganizing something which was previously in a calm and well-ordered state.  e.g. Successful breeding requires quiet, peaceful conditions with as little disturbance as possible.

infrared: ADJ Infrared radiation is similar to light but has a longer wavelength, so we cannot see it without special equipment.   e.g. This information is encrypted within the Smartpen and then sent out through aninfraredtransmitter.

Visible light has a wavelength of between only forty and eighty millionths of a centimeter.

millionths: FRACTION Amillionth of something is one of a million equal parts of it. 百万分之一的 e.g. The bomb must explode within less than a millionth of a second

ether: the space through which radio waves or computer signals travel以太，能媒

The fundamental postulate of the theory of relativity, as it was called, was that the laws of science should be the same for all freely moving observers, no matter what their speed.

postulate: something believed to be true, on which an argument or scientific discussion is based  e.g. the basic postulates of Marxism

Any observer can work out precisely what time and position any other observer will assign to an event, provided he knows the other observer’s relative velocity.

provided: CONJ If you say that something will happenprovidedorprovided thatsomething else happens, you mean that the first thing will happen only if the second thing also happens. 如果…才会…  e.g. The other banks are going to be very eager to help, provided that they see that he has a specific plan. 连词后面接句子

velocity: [C,U]technicalthe speed of something that is moving in a particular direction

cesium: 铯金属铯

platinum: a silver-grey metal that does not change colour or lose its brightness, and is used in making expensive jewellery and in indus-try. It is a chemical element: symbol Pt铂

We must accept that time is not completely separate from and independent of space, but is combined with it to form an object called space-time.

For instance, one can say that a point in a room is seven feet from one wall, three feet from another, and five feet above the floor.

在一个坐标系里描述三维空间的说法。同一平面用be x feet from sth, 高度用above 

instead, they follow the nearest thing to a straight path in a curved space, which is called a geodesic.

geodesic： Nthe shortest line between two points on a curved or plane surface 短程线 (Also called geodesic line)

elongated: ADJ If something is elongated, it is very long and thin, often in an unnatural way. 过于细长的  e.g. The light from my candle threw his elongated shadow on the walls.

This proof of a German theory by British scientists was hailed as a great act of reconciliation between the two countries after the war.

reconciliation: a situation in which two people, countries etc become friendly with each other again after quarrelling  e.g. The leadership announced a programme of national reconciliation

The situation, however, is quite different in the general theory of relativity. Space and time are now dynamic quantities: when a body moves, or a force acts, it affects the curvature of space and time – and in turn the structure of space-time affects the way in which bodies move and forces act.

curvature: the state of being curved, or the degree to which something is curved

原文来自 A Brief History of Time: CHAPTER 2——SPACE AND TIME