The Tidal Theory, also known as the Tidal Hypothesis, was proposed by James Jeans and Harold Jeffreys in the early 20th century. It attempted to explain the formation of the Earth and the Moon. However, it has been largely discredited by modern scientific understanding.

Here's how the Tidal Theory went:

* Close Encounter: It suggested that the Sun was much closer to a passing star in the early solar system. This star's gravity would have pulled out a tidal bulge of material from the Sun.

* Formation of a Filament: This pulled material would have formed a long, thin filament.

* Condensation and Separation: The filament would have eventually condensed, forming the Earth and Moon.

Why the Tidal Theory is Discredited:

* Energy Constraints: The amount of energy required for such a massive tidal event is astronomically high, and there's no evidence that such a close encounter ever occurred.

* Compositional Differences: The Earth and Moon have significantly different compositions, which the theory doesn't adequately explain.

* Angular Momentum: The theory struggles to account for the angular momentum of the Earth-Moon system.

Modern Theories:

The currently accepted theory for the formation of the Earth and Moon is the Giant Impact Hypothesis. This theory proposes that a Mars-sized object (called Theia) collided with the early Earth, creating a massive debris disk that eventually coalesced into the Moon. This theory has better explained the Earth and Moon's compositions, angular momentum, and other characteristics.

While the Tidal Theory was a pioneering attempt at explaining the origins of Earth and the Moon, it ultimately fell short due to its flaws. The Giant Impact Hypothesis, backed by substantial evidence and a more realistic scenario, is the dominant theory in modern planetary science.