8. Are the following statements about the text true or false?

1. Gravity is the dominant force. True

2. The Earth-Moon distance is 384,000 km, which is 2 light-seconds. false

3. The nearest star to us, other than the Sun, is Milky Way. false

4. The Milky Way is comprised of countless individual stars. true

5. The Sun orbits the galactic center approximately once every 200 million years. false

9. Match the first part of the sentence (1 –6) with the second part (a-f).

1. General relativity serves the foundation c

2. Cosmology deals especially with the search a

3. The nearest star is 10,000 times farther from us f

4. Thomas Wright suggested that the Milky Way was e

5. It has a bulging central d

6. They have fairly regular b

a for a theoretical framework.

b elliptical shapes.

c for modern cosmology.

d nucleus and spiral arms.

e a flat disc of stars.

f than the farthest planet.

10. Complete the sentences with words from the box.

Sun – Galaxy - mass – stars - orbit - discs

1. Our Sun seems to be just another star.

2. The total mass of all the stars in our Galaxy is very high.

3. Solar system orbit moves with respect to the center of the Galaxy.

4. The extragalactic objects are outside the Galaxy.

5. Circular discs like our Galaxy are faint.

6. We can see thousands of stars at a moonless night.

Unit seven text solids

In 350 B. C. a Greek mathematician named Euclid compiled out of the disorganized geometry of his day a set of rules concerning space and shapes that seemed so basic and true that no one changed it for two thousand years.

Under his guidance, geometry became an organized body of knowledge concerning the relations, properties, and measurements of lines, angles, surfaces and solids.

Even today, most textbooks on geometry follow the plan of Euclid's writings, often using his own diagrams, methods of proof, and ways of stating geometrical truths.

In our everyday lives we are constantly coming into contact with an endless variety of things, in our homes, in our journeys to and from school, at work, or at play - books, pencils, marbles and the list can be added to indefinitely. We can classify them in any way we please, by weight, by color, or by age, but in spite of the endless diversity of the objects we have listed, there is an important property that they all possess. Each takes up a certain amount of room or space.

Thus each page of our books is a solid, however thin the paper may be. The word solid as used here must not be confused with the word solid, which is used as opposed to liquid and gas.

Most solids are irregular in shape, e. g. a pebble in a stream, a cloud in the sky. Geometry deals with the shape, size, and position solids, which are regular in shape, e. g. a ball, a matchbox, a pencil.

The more common regular solids are: cube, cuboid or rectangular prism, triangular prism, square pyramid, cylinder, cone, sphere.

Solids are bounded by surfaces. These surfaces separate the solids from the surrounding space. Surfaces are of two kinds: plane and curved. The surfaces of a cube, rectangular prism, pyramids are plane surfaces, while the surface of a sphere is curved. A sheet of paper, e. g. a leaf of a book, may represent a surface, but even the thinnest sheet of paper will be a geometrical solid, since it has length, breadth, and thickness.

Surface intersected in lines are bounded by lines. Lines are either straight or curved.

Lines intersect in points. The meeting place of two edges is called a point (a vertex). The dot made on paper by a fine pencil point represents a point. No matter how fine the pencil point is, however, the dot is a geometrical solid since it has length, breadth, and thickness, and a point has no length, no breadth, and no thickness. A point indicates but has no size.