52. What significant event after the Big Bang is related to the appearance of th

Question

52. What significant event after the Big Bang is related to the appearance of the CMB, and

when did that happen?

53. Was the CMB always radiating in the microwave part of the spectrum?

54. There are ___ planets in the Solar system.

55. What are the three conditions a body must satisfy to be called a planet?

56. Why was Pluto demoted from the planetary status?

57. What methods are used to discover planets around other stars?

58. An astronomer from a distant star is observing the Sun exactly in the plane of Jupiter

(so that Jupiter crosses the solar disk); plot schematically the brightness of the Sun he

would observe it during the 25 (Earth) years period.

59. Age of the Earth is approximately:

60. How do we measure the age of the Earth (i.e. the age of the oldest rocks)?

61. How does it compare with the age of the Universe?

62. Why the chemical composition of solar system implies it was formed from the

remnants of older stars?

63. When did the first single cell life form on Earth?

64. How did the free oxygen first appear in our atmosphere?

Explanation / Answer

52) The cosmic microwave background (CMB), is radiationthat fills the universe and can be detected in every direction. Microwaves are invisible to the naked eye so thay cannot be seenwithout instruments. It created shortly after the universe came into being in the Big Bang, the CMB represents the earliest radiation that can be detected.

53) No. The radiation originated in a time when the universe was much smaller, hotter, and denser.

54) 9 Planet -  Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.

But after 2006 pluto is not consider as a planet because,

American astronomer Clyde Tombaugh discovered Pluto in 1930. From 1930 until 2006, Pluto sat comfortably beyond Neptune as the ninth planet in our solar system.

In 2006, however, changes were made. The truth is, nothing about Plutochanged, but the definition of a planet did. Once these changes became official, Pluto no longer fit the definition of a planet.

According to new rules adopted by the International Astronomical Union, a celestial body must meet the following criteria in order to qualify as a planet:

Pluto follows the first two rules: It is round, and it orbits the sun. It does not, however, follow the third rule. It has not yet cleared the neighborhood of its orbit in space. Because it does not follow this rule, Pluto is no longer considered a planet.

55) In 2006, the International Astronomical Union (IAU), which has the final say on matters of astronomical nomenclature, voted on a formal definition of what makes a planet. (The official press release is here.) According to their decision a planet must satisfy the following three criteria:

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