How big is space? That is a question man has been asking since the beginning of time. When your grandparents were in school, it was 36 that the Universe was very 37 perhaps only 5,000 light years 38. 500 years ago people considered that the Universe was only a little bit 39 than the Earth. In modern times with the 40 of technology we are finally starting to 41 the immense (无边的) size of the Universe, and it is much bigger than anyone 42 have ever imagined.

Scientists cannot stretch (伸展) a measuring tape from the Earth to a nearby star, so 43 do they know how far away they are? Scientists use something 44 Parallax (视差). Parallax means 45 that they look at how much the stars move in the sky 46 throughout the year as the Earth circles the Sun. This is not something 47 to you. In fact if you stretch out your hand in front of you and 48 your thumb, while 49 one eye, and then the other, your thumb will 50 to move back and forth. Stars do the 51 thing, but our eyes are too close to see the 52. However if we take a picture while on one side of Earth’s orbit, and then take another when we get to the 53 side of the orbit, then we have a large enough 54 that we can see the stars parallax, and 55 how far away they really are.

36. A. measured           B. said                 C. thought            D. proved

37. A. old                     B. big                   C. mysterious        D. small

38. A. over               B. across           C. through          D. outsides

39. A. bigger            B. smaller          C. heavier           D. nearer

40. A. popularity      B. power          C. energy          D. strength

41. A. grasp           B. control          C. imagine          D. feel

42. A. would          B. should         C. could           D. might

43. A. what             B. why             C. how            D. when

44. A. honored          B. called            C. considered       D. believed

45. A. actually         B. especially        C. generally        D. simply

46. A. in and out       B. back and forth   C. sooner or later         D. up and down

47. A. unacceptable           B. unfamiliar       C. unbelievable      D. unnatural

48. A. look at                B. shake                C. glare at         D. notice

49. A. covering        B. opening         C. controlling       D. hiding  

50. A. continue          B. happen         C. stop            D. appear  

51. A. common       B. different        C. strange         D. same

52. A. result            B. effect          C. difference        D. similarity

53. A. suitable           B. same           C. opposite        D. correct

54. A. distance                 B. length          C. height           D. width

55. A. realize           B. determine        C. recognize        D. decide

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