Nebular Hypothesis PDF

Nebular Hypothesis Proposed by Immanuel Kant and Pierre- Simon Laplace in the 18th century. The nebular hypothesis, also known as the protoplanetary disk model, is a scientific theory that describes the formation of the solar system. It proposes that the Sun, planets, and other celesti...

Nebular Hypothesis Proposed by Immanuel Kant and Pierre- Simon Laplace in the 18th century. The nebular hypothesis, also known as the protoplanetary disk model, is a scientific theory that describes the formation of the solar system. It proposes that the Sun, planets, and other celestial bodies formed from a rotating cloud of gas and dust called a nebula.  Nebular Hypothesis According a massive molecular to the cloud nebular composed hypothesis, mostly of hydrogen and helium, along with trace amounts of heavier elements, began to collapse under its own gravity. As the cloud contracted, it started to spin faster and flatten into a spinning disk shape due to conservation of angular momentum. The central region of the disk, known as the protosun, became increasingly dense and hot. Eventually, nuclear fusion was ignited in the core, leading to the birth of the Sun. The remaining material in the disk consisted of gas, dust, and small solid particles known as planetesimals.  Nebular Hypothesis Over time, these planetesimals began to collide and merge through a process called accretion, gradually growing in size. Through further collisions and gravitational interactions, larger bodies called protoplanets formed. These protoplanets eventually underwent further growth and differentiation to become the planets of the solar system. In the case of Earth, it went through a process of differentiation, with denser materials sinking to the core and lighter materials accumulating in the mantle and crust. The process of differentiation also generated heat, leading to the development of a molten interior.  Nebular Hypothesis Objections 1. The planet possess 98% of the rotational energy of the solar system, whereas the sun has about 99.87% of the mass. 2. The heavy elements in the earth can originate only at temperatures far higher than those prevailing on the sun. 3. Some of the satellites revolve in a retrograde (backward) direction, and one of them revolves faster than its planet rotates.