lows, therefore, that there must be extra dark matter present in clusters of galaxies.* So, the only way we can detect dark matter would be by its effect on bright matter.
The main candidates of dark matter would be remnants left over from the early stages of the universe. One possibility is elementary particles. There are several hypothetical candidates, particles which we think might exist but we haven’t actually detected them yet. But the most promising case is a particle for which we have good evidence, the neutrino. The neutrino was thought to have no mass of its own, but observations have suggested that the neutrino may have a small mass. *If this is confirmed and is found to be of right value, neutrinos would provide enough mass to bring the density of the universe up to the critical value.*
Vocabulary Notes
1 to estimate – to calculate
2 to add up – if you add up several numbers, you calculate their total 3 to add in – if you add in something, you include it as a part of
something else
4 the total – the number that you get when you add a series of figures together
5 enormous – very large
6 presumably – most probably
7 to require – to need
8 extra – additional
9 a remnant – a small part that was left of what was destroyed
10 promising – perspective
11 to confirm – to prove
POST-READING TASK (to be done in writing)
I. Put in the prepositions.
1.We can try to estimate the average density … the universe … observations.
2.One piece … evidence … dark matter comes …the spiral galaxies.
3.These are enormous pan-shaped collections … stars and gas.
4.They are rotating … the centres.
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5.Another piece … evidence … dark matter comes … clusters of galaxies.
6.Galaxies are not uniformly distributed … space.
7.Clusters … galaxies range … a few galaxies … millions.
8.We can measure the speed … which the individual galaxies are moving.
II. Study grammar point III and do an exercise. Change the sentences according to the model:
S + (is believed; is supposed; is expected; is considered; is known; is proved) + to V
1.The universe must contain some matter which we cannot observe directly.
2.One piece of evidence comes from spiral galaxies.
3.Spiral galaxies are enormous pancake-shaped collections of stars and gas.
4.Another piece of evidence for dark matter comes from clusters of galaxies.
5.The speeds at which individual galaxies are moving are so high that the clusters would fly apart unless they were held together by gravitational attraction.
6.The mass required is considerably greater than the masses of all the galaxies.
7.The main candidates of dark matter are elementary particles.
8.The neutrino is the most promising candidate.
III. A paragraph is a micro text. Cut down each paragraph of the passage to the topical sentence and write a summary.
IV. Do you have any information about the dark matter which is not given in the passage? Write a paragraph.
CLASS EXERCISES
Exercise 1 (do it yourself)
Make up simple sentences using the below words and expressions. Follow the passage.
1.to contain dark matter
2.to observe dark matter directly
3.an enormous pan-shaped collection of stars and gas
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4.to rotate about its centre
5.to be uniformly distributed throughout space
6.to be gathered together in clusters
7.to range from to
8.to detect dark matter
9.to suggest
10.to bring up to
Exercise 2
Sharing ideas (in groups)
1 How can we estimate the average density of the universe?
2.Where do the pieces of evidence of dark matter come from?
3.What is a spiral galaxy?
4.How do astronomers account for the fact that the spiral galaxies do not fall apart as they rotate?
5.How are galaxies distributed throughout space?
6.How many galaxies are there in a cluster?
7.What mechanism collects stars in clusters?
8.At what speed are individual galaxies moving in these clusters?
9.Why do the clusters not fall apart?
10.What is the proportion between the mass of all the galaxies and the mass required for the galaxies to form clusters?
11.Why do astronomers call extra matter ‘dark matter’?
UNIT 7
BLACK HOLES
“Turn to Stephen Hawking if you would look outward, to the ends of the universe”
Independent on Sunday
PRE-READING TASK Study some grammar points. I. N + to Vo; N + to be V3
An infinitive after a noun characterizes it and expresses an action which must be done or could be done in the future.
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Study the sentences.
1.The universe is a puzzle to be guessed.
2.This is a much more difficult question to answer.
3.Because my father was a scientific researcher, I felt that scientific research was a natural thing to do when one grew up.
II. Active and Passive
A verb has two categories: tense (past, present and future) and voice (active and passive). There are two infinitives:
active to V and passive to be + V3.
On the basis of an active infinitive we form active sentences and use active when it is important who or what does the action.
On the basis of a passive infinitive we form passive sentences and prefer passive when it is not important who or what does the action.
In passive sentences we use be (is, are, was, were, has been, will be etc) + V3.
Study the sentences.
1.In the 1930s quantum mechanics was applied with great success to systems such as atoms or molecules, which have only a finite number of degrees of freedom.
2.The problem has been overcome.
3.The interactions are divided into four categories and are represented by integer-spin fields.
Note: In passive sentences modal verbs are followed by be + V3
Study the sentences.
1.I want to discuss the possibility that the goal of theoretical physics might be achieved in the not-too-distant future.
2.The values of these quantities cannot be predicted by our theories. Instead, they have to be chosen to agree with observations.
III. Would
a.Would is used to talk about the natural course and behavior of things and events as a result of some action. It is the less definite form of will.
Study the sentence.
If the electrons are in orbit around the nucleus, electromagnetic waves would carry away energy and would cause the electrons to spiral into the nucleus.
b.We also use would, if we imagine the situation. We can also use could = would be able to
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Study the sentence.
In this state the electron couldn’t radiate energy in the form of electromagnetic waves because there would be no lower energy state.
IV We use that (those) to refer to a thing (things) that has been mentioned before.
Study the sentences.
1.The key physical properties of Mars are remarkably similar to those of Earth.
2.The Mar’s axis is tilted to a similar degree as that of Earth.
3.The difference between the classical physics and the modern one is that between logical and illogical physics.
Give Russian correspondence:
as (in the process), eventually (finally), both ….. and, an effect (an influence), then (in this case), until, a few (some), so (thus, therefore, hence), fails to V (is unable to V)
Study the passage.
As far as I know, the first person to discuss black holes was a Cambridge man called John Mitchell, who wrote a paper about them in 1783. His idea was this. Suppose you fire a cannon-ball vertically upwards from the surface of the earth. As it goes up, it will be slowed down by the effect of gravity. Eventually, it will stop going up and will fall back to the earth. If it started with more than a certain critical speed, however, it would never stop rising but would continue to move away. This critical speed is called the escape velocity. It is about 7 miles a second for the earth, and about 100 miles a second for the sun. These velocities are greater than the speed of a real cannon-ball, but they are much smaller than the velocity of light, which is 186,000 miles a second. This means that gravity does not have much effect on light; light can escape without difficulty from the earth or the sun. However, Mitchell reasoned that it would be possible to have a star that was both massive and small in size so that its escape velocity would be greater than that of light. We would not be able to see such a star because light from its surface would not reach us; it would be dragged back by the star’s gravitational field. However, we might be able to detect the presence of the star by the effect that its gravitational field would have on nearby matter.
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