Geography. Козлова Е.П. - 29 стр.

    There exist several hypotheses of the origin of the Solar System, there are two of
them:
    The “catastrophic” theory. This held that the planets were formed of material torn
away from the sun by the action of another star, either by collision or by tidal
phenomena. This star may have been one which its proper motion brought into the
neighbourhood of the sun or it might have been a “companion”, assuming the sun to
have once been a double star, like many binary systems in the universe.
    The nebular theory. This theory suggested that the sun was originally surrounded
by a mass of gas extending beyond the limits of the present solar system. This nebula
resulted either from the evolution of the sun, or from the capture by the sun of a cloud
of interstellar matter, which, condensing, separated from it and gradually
agglomerated to form the planets. Our solar system seems to have developed
according to this latter pattern.

6.5 Say whether the following statements are true or false

1. Galaxy is a great star system.
2. Our own galaxy, the Milky Way, is classified as an elliptical galaxy.
3. Seventeen galaxies of a supergalaxy are concentrated within a radius of about one
   million kilometeres.
4. The Solar System consists of the sun, its nine planets and a variety of smaller
   bodies.
5. The sun’s temperature is equal at its surface and at its core.
6. The sun is almost entirely solid.
7. Of all nine planets Pluto is closest to the sun.
8. Asteroids are small masses of solid particles, held loosely together.
9. There exist several hypotheses of the origin of the Solar System.

6.6 Fill in the blanks with the suitable words from the text

1. Of all nine planets Mercury is ………. to the sun .……... by Venus, Earth, Mars,
   ..…….., Saturn, Uranus, Neptune and Pluto in that order.
2. The ………. planets are closer together and the ………. ones are farther apart.
3. The planets ………. around their axes and ………. around the sun in elliptical
   ………. determined by the force of ………. .
4. The ………. diameter of ………. is about 7 billion miles.
5. As to the ………. of the Solar System there exist several hypotheses.
6. The ………. theory suggested that the planets are formed of material torn away
   from ………. by the action of another star.

6.7 Ask questions to which these sentences are the answers

1. The Universe as we view it today is made up of at least a billion aggregations of
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