Answer: Option [C]The correct answer is Earth. In the solar system, Earth is the fifth largest of the planets. The earth is a unique planet of the solar system because: Conditions favourable to support life are probably found only on the earth. The earth is neither too hot nor too cold.
Answer: Option [A]The correct answer is Nicolaus Copernicus. In 1543, Nicolaus Copernicus detailed his radical theory of the Universe in which the Earth, along with the other planets, rotated around the Sun. His theory took more than a century to become widely accepted.
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Answer: Option [D]The exact time taken by the earth for single rotation on its own axis is 23 hrs 56 minutes 4.09 sec. It's the time it takes for a distant star to return to the same position in the sky, and it differs from the solar day because the Earth revolves around the Sun as it rotates on its own axis; there is one more sidereal day than solar day each year. A sidereal day is approximately 23 hours, 56 minutes, 4.0916 seconds.
Answer: Option [A]The correct answer is Contracted star with intense gravitational pull. A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying.
Answer: Option [A]The correct answer is 1632. Galileo continued his study of astronomy and became more and more convinced that all planets revolved around the Sun. In 1632, he published a book that stated, among other things, that the heliocentric theory of Copernicus was correct.
