Solar System Formation and Big Bang Theory Explained

Solar System Theory

The Sun and the planets revolve in elliptical orbits. The planets are categorized into:

• Inner planets: Small, dense, and rocky with impact craters.
• Outer planets: Large, gaseous, and lighter.

Nebular Theory and Planetesimal Formation

The solar system began as a cloud of dust and gas. Gravitational collapse created a central mass and a rotating disc. The protosun formed at the center, eventually triggering nuclear fusion to become a star.

Formation of Protoplanets

Within the gas and dust disk, particles collided and fused to form granules, then clusters, and finally planetesimals. Through continuous collisions, these planetesimals merged to form protoplanets, clearing their respective orbital zones.

Formation of the Earth

The terrestrial protoplanet formed from the union of inner planetesimals containing silicates, iron, and volatile elements. Differentiation of densities occurred while the Earth was molten; iron sank to the core (the Iron Catastrophe), while gases escaped to form the atmosphere through degassing. Subsequent cooling led to the condensation of water vapor, forming the oceans.

Origin of the Moon

There are three primary theories regarding the Moon's origin:

• Sister Theory: Formed simultaneously with Earth in the same orbital zone.
• Capture Theory: Formed elsewhere and was later captured by Earth's gravity.
• Giant Impact Hypothesis: A planet collided with Earth, and the resulting debris cloud formed the Moon.

The Big Bang Theory

At time zero, all mass and energy were concentrated at a point of infinite density. Inflation triggered rapid expansion, followed by the creation of subatomic particles. Primordial synthesis produced the first Hydrogen and Helium atoms, eventually leading to the cosmic background radiation.

Galactic Evolution and Universe Fate

Galaxies formed from Hydrogen and Helium, while heavier elements like Carbon and Iron were forged in supernovae and dispersed throughout the universe. The ultimate fate of the universe depends on its density:

• Closed Universe: If density is greater than critical, it will eventually collapse.
• Open Universe: If density is less than critical, expansion will accelerate.
• Flat Universe: If density equals critical, expansion remains constant.