Lesson 40 Waves
What false impression does an ocean wave convey to the observer?
Waves are the children of the struggle between ocean and atmosphere, the ongoing signatures of infinity. Rays from the sun excite and energize the atmosphere of the earth, awakening it to flow, to movement, to rhythm, to life. The wind then speaks the message of the sun to the sea and the sea transmits it on through waves-an ancient, exquisite, powerful message.
These ocean waves are among the earth's most complicated natural phenomena. The basic features include a crest (the highest point of the wave), a trough(the lowest point), a height(the vertical distance from the trough to the crest), a wave length (the horizontal distance between two waves crests), and a period (which is the time it takes a wave crest to travel one wave length).
Although an ocean wave give the impression of a wall of water moving in your direction, in actuality waves move through the water leaving the water about where it was. If the water moving with the wave, the ocean and everything on it would be racing into the shore with obviously catastrophic results.
An ocean wave passing through deep water causes a partical on the surface to move in a roughly circular orbit, drawing a partical first toward the advancing wave, then up into the wave, then forward with it and then--as the wave leaves the partical behind--back to its starting point again.
From both maturity to death, a wave is subject to the same laws as any other 'living' thing. For a time it assumes a miraculous individuality that, in the end, is reabsorbed into the great ocean of life.
The undulating waves ofthe open sea are genearated by three natual causes: wind, earth movements or themors, and the gravitational pull of the moon and the sun. Once waves have been generated, gravity is the force that drives them in a continual attempt to restore the ocean surface to a flat plain.
signature
infinity
signatures of infinity
ray
energize
rhythm
transmit
equisite
phenomena
crest
trough
vertical
horizontal
actuality
catastrophic
particle
maturity
undulate
tremor
gravitational
Lesson 41 Training elephants
At what point does the training of a captive wild elephant begin?
Two main techniques have been used for training elephants, which we may call respectively the tough and the gentle. The former method simply consists of setting an elephant to work and beating him until he does what is expected of him. Apart from any moral considerations this is a stupid method of tranining, for it pruduces a resentful animal who at a later stage may well turn man-killer. The gentle method requires more patience in the early stages, but produces a cheerful, good tempered elephant who will give many years of loyal service.
The first essential in elephant training is to assign to the animal a single mahout who will be entired responsible for the job. Elephants like to have one master just as dogs do, and are capable of a considerable degree of personal affection. There are even stories of half-trained elephant calves who have refused to feed and pined to death when by some unavoidable circumstance they have been deprived of their own trainer. Such extreme cases must probably be taken with a grain of salt, but they do underline the general principlethat the relationship between elephant and mahout is the key to sucessful training.
The most economical age to capture an elephant for training is between fifteen and twenty years, for it is then almost ready to undertake heavy work and can begin earn its keep straight away. But animals in this age do not easily become subservient to man, and a very firm hand must be employed in the early stages. The captive elephant, still roped to a tree, plunges and screams every time a man approaches, and for several days will probably refuse all food through anger and fear. Sometimes a tame elephant is tethered nearby to give the wild one confidence, and in most cases the captive gradually quietens down and begins to accept its food. The next stage is to get the elephant to the training estabishment, a ticklish business which is achieved with the aid of two tame elephants roped to the captive on either side.
When several elephants are being trained at one time, it is customary for the new arrival to be placed between the stalls of two captives whose training is already well advanced. It is then left completely undisturbed with plenty of food and water so that it can adsorb the atmospher of its new home and see that nothing particularty alarming is happening to its companions. When is is eating normally, its own training begins. The trainer stands in front of the elephant holding a long stick with a sharp metal point. Two assistants, mounted on tame elephants, control the captive from either side, while others rub their hand over his skin to the accompaniment of a monotonous and soothing chant. This is supposed to induce pleasurable sensations in the elephant, and its effects are reinforced by the use of endearing epithets, such as 'ho! my son', or 'ho! my mother', or'my mother', according to the age and sex of the captive. The elephant is not immediately susceptible to such blandishments, however, and usually lashes fiercely with its trunk in all directions. These movements are controlled by the trainer with the metal-pointed stick, and the trunk eventually becomes so sore that the elephants curls it up and seldomafterwards uses it for offensive purpose.
technique
tough
resentful
assign
mahout
calf
pine
underline
keep
subservient
plunge
tame
tether
ticklish
alarming
accompaniment
soothe
reinforce
endearning
epithet
susceptible
blandishment
lash
curl
自己学啊？好妈妈
Lesson 42 Recording an earthquake
What does a pen have to do to record on paper the vibrations generated by an earthquake?
An earthquake comes like a thief in the night, without warning. It was necessary, therefore, to invent instruments that neither slumbered nor slept. Some devices were quite simple. One, for instance, consisted of rods of various lengths and thickness which would stand up on end like ninepins. When a shock came, it shook the rigid table upon which these stood. If it were gentle, only the more unstable rods fell. If it were severe, they all fell. Thus the rods, by falling, and by the direction in which they fell, recorded for the slumbering scientist the strength of a shock that was too weak to waken him, and the direction from which it came.
Morning, here i am!
But instruments far more delicate than that were needed if any really serious advance was to be made. The ideal to be aimed at was to devise an instrument that could record with a pen on papaer, the movements of the ground of the table as the quake passed by. while i write my pen moves, but the paper keeps still. With practice, no doubt, I could in time learn to write by holding the pen still while the paper moved. That sounds a silly suggestion, but that was precisely the idea adopted in some of the early instruments( seismometer) for recording earthquake waves.
But when table, penholder and paper are all moving, how is it possible to write legibly? The key to a solution of that problem lay in every observation. Why does a person standing in a bus or a train tend to fall when a sudden start is made? It is because his feet move on, but his head stays still. A simple experiment will help us a little further. Tie a heavy weight at the end of a long piece of string.With the hand held high in the air, hold the string so that the weight nearly touches the ground. Now move the hand to and fro and around but not up and down. It will be found that the weight moves but slightly or not at all. Image a pen attached to the weight in such a way that its point rests on upon a piece of paper on the floor.Imagine an earthquake shock shaking the floor,the paper, you and your hand. In the midst of all this movement, the weight and the pen would be still. But as the paper moved from side to side under the pen point, its movement would be recorded in ink upon the surface. It was upon this principle that the first instruments were made, but the paper was wrapped round a drum which rotated slowly. As long as all was still, the pen drew a streight line, but while the drum was being shaken, the line that the pen was drawing wriggled from side to side. The apparatus thus described.
The apparatus thus described, however, records only the horizontal component of the wave movement, which is, in fact, much more complicated.If we could actually see the path described by a particle, such as a sand grain in the rock, it would be more like that of a bluebottle buzzing round the room; it would be up and down, to and fro and from side to side. Instruments have been devised and can be so placed that all three elements can be recorded in different graphs.
When the instrument is situated at more than 700 miles from the earthquake center, the graphic record shows three waves arriving on after the other at short intervals. The first records the arrival of longitudinal vibrations. The second record marks the arrival of transverse vibrations which travel more slowly and arrive several minutes after the first. These two have travelled through the earth. It was from the study of these that so much was learnt about the interior of the earth. The third, or main wave, is the slowest and has travelled round the earth through the surface rocks.
slumber
ninepin
rigid
delicate
seismometer
penholder
legibly
drum
wriggle
bluebottle
graph
graphic
longitudinal
transverse
Lesson 43Are there atrangers in space?
What does the 'uniquely rational way' for us to communicate with other intelligent beings in space depend on?
We must conclude from the work of those who have studied the origin of life, that given a panet only approximately like our own, life is almost certain to start. Of all the planets in our own solar system, we are now pretty certain the Earth is the only one on which life can survive. Mars is too dry and poor in oxygen, Venus for too hot, and so is Mercury, and the outer planets have temperatures near absolute zero and hydrogen-dominated atmospheres.
But other suns, stars as the astronomers call them, are bound to have planets like our own, and as the number of stars in our own Milky Way alone, and then there are three thousand million other MilkyWays, or galaxies, in the universe. So the number of stars that we know exist is now estimated at about 300 M M M.
Although perhaps only 1 per cend of the life that has started somewhere will develop into highly complex and intelligent patterns, so vast is the number of planets, that intelligent life is bound to be a natural part of the universe.
If there are so certain that other intelligent life exists in the universe, why have we had no visitors from out space yet? First of all, they may have come to this planet of ours thousands or millions of years ago, and found out then prevailing primitive state compeletely uninteresting to their own advanced knowledge.
Professor Ronald Bracewell, a leading American radio astronomer, argued in Nature that such a superior civilization, on a visit to our own solar system, may have left an automatic messenger behind to await the possible awakening of an advanced civilization. Such a messenger, receiving our radio and television signals, might well re-transmit them back to its home planet, although what impression any other civilization would thus get from us is best left unsaid.
But here we come up against the most difficult of all obstacles to contact with people on other planets --the astronomical distances which seperate us. As a reasonable guess, they might, on an average, be 100 light years away. (A light year is the distance which light travels at 186,000 miles per second in one year, namely 6 million million miles.) Radio waves also travel at the speed of light, and assuming such an automatic messenger picked up our first broadcasts of the 1920's, the message to its home planet is barely halfway there. Similarly, our own present primitive chemical rockets, though good enough to orbit men, have no chance of transporting us to the nearest other star, four light years away, let alone distances of tens or hundreds of light years.