| Consider the following statements of Laplace's hypothesis regarding the origin of earth |
| 1. There was a huge hot gaseous nebula in the space |
| 2. From the beginning, this hot nebula was rotating oh its axis |
| 3. The nebula was continuously cooling down due to loss of heat from its outer surface |
| 4. One ring was separated from the nebula and it further divided into nine rings cooled and condensed to form planets. Select the correct answer from the codes given below: |
A) 1 and 2
B) 3 and 4
C) 2 and 3
D) All the above
Correct Answer: D
Solution :
[d] The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System. It suggests that the Solar System formed from nebulous material. There is evidence that parts of the nebular hypothesis were first proposed in 1734 by Emanuel Swedenborg. Immanuel Kant, who was familiar with Swedenborg's work, developed the theory further in 1755, when Kant published his Universal Natural History and Theory of the Heavens, wherein he argued that gaseous clouds, nebulae, slowly rotate, gradually collapse and flatten due to gravity, eventually forming stars and planets. A similar model was developed independently and proposed in 1796 by Pierre-Simon Laplace in his Exposition du systeme du monde. He envisioned that the Sun originally had an extended hot atmosphere throughout the volume of the Solar System. His theory featured a contracting and cooling protosolar cloud?the protosolar nebula. As this cooled and contracted, it flattened and spun more rapidly, throwing off (or shedding) a series of gaseous rings of material; and according to him, the planets condensed from this material. His model was similar to Kant's, except more detailed and on a smaller scale. 'While the Laplacian nebular model dominated in the 19th century, it encountered a number of difficulties. The main problem was angular momentum distribution between the Sun and planets. The planets have 99% of the angular momentum, and this fact could not be explained by the nebular model. As a result, this theory of planet formation was largely abandoned at the beginning of the 20th century.
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