The Collision Hypothesis proposed by Harold Jeffreys involved the collision and movement of three stars.

Introduction:
The Collision Hypothesis, proposed by English mathematician and geophysicist Harold Jeffreys in 1929, suggests that the movement and collision of three stars could lead to the formation of binary star systems. This hypothesis was put forward as a possible explanation for the presence of binary stars in the universe.

Explanation:
The Collision Hypothesis proposes that three stars, not just two, are involved in the formation of binary star systems. According to this hypothesis, the process begins with three stars in a gravitational system. Due to the gravitational interactions between the stars, their paths may converge, resulting in a close encounter or collision.

Three-Body Problem:
The movement of three celestial bodies interacting through gravity is complex and is known as the three-body problem. The three-body problem is notoriously difficult to solve analytically, as the interactions between the bodies create chaotic and unpredictable movements. Therefore, numerical simulations and computational methods are often used to study such systems.

Binary Star Formation:
In the context of the Collision Hypothesis, the collision or close encounter of three stars can lead to the formation of a binary star system. During the interaction, one star might be ejected from the system due to the strong gravitational forces involved. The remaining two stars, having lost some energy and angular momentum during the collision, can settle into a stable orbit around each other, forming a binary star system.

Supporting Evidence:
There is observational evidence that supports the Collision Hypothesis. For example, studies have shown that binary star systems are more common in star clusters, where close encounters and collisions between stars are more likely to occur. Additionally, simulations and computer models have reproduced the formation of binary star systems through three-body interactions, providing further support for the Collision Hypothesis.

Conclusion:
In conclusion, the Collision Hypothesis proposed by Harold Jeffreys suggests that the movement and collision of three stars can result in the formation of binary star systems. This hypothesis provides a possible explanation for the prevalence of binary stars in the universe. The complex nature of three-body interactions and the supporting observational and computational evidence contribute to the credibility of the Collision Hypothesis.