Sir James Jeans, a British scientist, proposed his 'tidal hypothesis' to explain the origin of the earth in 1919, while Harold Jeffreys, another British scientist, suggested modifications to the 'tidal hypothesis' in 1929, making it more relevant and significant in the context of growing knowledge of the cosmogonic ideas of the first quarter of the twentieth century. The tidal hypothesis is a modern theory about the origins of the planet and solar system. In this article, you will read about the Tidal Hypothesis of Jeans and Jeffreys in detail for the IAS exam.

Assumptions of Tidal Hypothesis of Jeans and Jeffreys

• The sun and another invading star formed the solar system.
• The sun was once a massive incandescent gaseous mass of materials.
• Aside from the sun, there was another star in the universe known as an 'intruding star.' This intruding star was much bigger in size than the primitive sun.
• The sun was stationary and rotated on its axis. The ‘intruding star’ was moving along a path in such a way that it was destined to come nearer to the primitive sun.
• The intruding star's tidal force had a significant impact on the surface of the primitive sun.
• According to James Jeans, a massive amount of matter was ejected from the primitive sun as a result of the intruding star's massive gravitational force, which later became the building material for future planets.
• Everyone in the universe attracts every other body with a force that is directly proportional to the product of the two bodies' masses and inversely proportional to the square of the distance between them, according to Newton's law of universal gravitation.

Evolution of Filament

• According to James Jeans, the 'intruding star' was constantly moving closer to the primitive sun, exerting gaseous tidal force (gravitational pull) on its surface.
• As the 'intruding star' got closer to the 'primitive sun,' its gravitational attraction grew stronger, and the tidal force grew stronger as well.
• When the 'intruding star' got close enough to the 'primitive sun’, its gravitational pull reached its maximum, causing a massive cigar-shaped tide to form on the 'primitive sun's outer surface,' with a massive mass of matter ejected from the 'primitive sun' in the shape of a cigar.
• This cigar-shaped substance, which was much thicker in the middle and thinner and sharper at the ends, was dubbed “filament” by James Jeans.

Formation of Planets from the Filament

• According to James Jeans, the cooling and condensation of the filament's incandescent mass of gaseous matter resulted in the formation of eight planets in our solar system.
• After being separated from the sun, the filament began to cool. As the filament cooled, it began to shrink in size.
• The filament's contraction caused it to break into numerous fragments, each of which was condensed to become a new planet. Eight planets were formed as a result of this event.
• The filament of incandescent gaseous matter allowed for the formation of larger planets in the centre (such as Jupiter and Saturn) and smaller planets at the tapering extremities.
• Our sun was created from the remnants of the primitive sun. The sun's gravitational pull and tidal influence on the newly created planets caused the satellites to develop.
• When the amount of matter ejected from planets for the production of new satellites grew so low that its central gravitational force/attraction could no longer hold it together, the processes of satellite formation stopped.
• The size of the planet determined the rate of cooling of the ancient incandescent gaseous planets.
• The larger planets and satellites cooled slowly, whereas the smaller planets and satellites condensed to liquid and then solid forms in a short time. This could explain why larger planets have more satellites while smaller planets have fewer.
• Very small planets were cooled and condensed soon, so no matter could be ejected from their surface due to the tidal effect and thus no satellite could be formed. This is why Mercury, Venus and Pluto do not have any satellites.

Modification by Jeffreys

• In 1929, Harold Jeffreys, a British physicist, updated James Jeans' initial tidal hypothesis and presented his concept as the 'collision hypothesis.'
• Before the birth of our solar system, there were three stars in the universe, according to Jeffreys.
• The first was our primitive sun, the second was its 'companion star,' and the third was an 'intruding star' approaching the 'companion star.'
• As a result, the 'intruding star' collided with the 'compaion star.' Due to head-on collision the companion star was completely smashed and shattered, some shattered portions were scattered in the sky while remaining debris started revolving around the primitive sun.
• However, the impact of the collision and explosion allowed the intruding star to break free from the original sun's gravitational pull and gradually fade away from the cosmos.
• The planets of our solar system were formed from the companion star's debris.
• It should be noted that Jeffreys proposed changes to James Jeans' tidal theory with the goal of removing key fundamental flaws in the tidal hypothesis so that it could survive modern scientific critique.

Criticism of Tidal Hypothesis of Jeans and Jeffreys

• According to B. Levin, the universe is limitless in space and time, and the stars are so far apart that such a close encounter is unlikely.
• James Jeans did not explain the location or fate of the intruding star that triggered tidal, filament-like eruptions on the ancient sun's surface.
• On the basis of mathematical calculations, N.N. Parisky has demonstrated that the tidal hypothesis fails to explain the real distances between the sun and the planets in our current solar system.
• Our solar system's planets are mostly made up of high-atomic-weight elements, whereas the sun's constituent elements (from which the planets are assumed to have formed) are lighter atomic-weight elements, such as hydrogen and helium. The tidal hypothesis falls short of providing a credible explanation for such a strange occurrence.
• James Jeans was unable to explain the technique and mechanism by which materials ejected from the primitive sun condensed.

Conclusion

The tidal hypothesis, as proposed by James Jeans and modified by Harold Jeffreys, enjoyed a long period of popularity and wide acceptance until the end of the first half of the twentieth century, but the hypothesis was severely criticised on various grounds. Even Jeffreys admitted in Guttenberg (1951) that his modified version of the tidal hypothesis needed significant revisions and was incorrect in several places.

FAQs 

MCQs

1. What does the Tidal Hypothesis explain?

A. The origin of stars
B. The formation of galaxies
C. The origin of the solar system
D. The formation of black holes

2. According to the Tidal Hypothesis, what led to the formation of planets?

A. Collision between two stars
B. Gravitational pull from a passing star
C. Supernova explosion
D. Formation of a nebula

3. Which of the following is a limitation of the Tidal Hypothesis?

A. It cannot explain the distribution of planets
B. It does not explain the formation of moons
C. It does not account for the angular momentum of planets
D. It cannot explain the existence of asteroids

4. Which process is central to the Tidal Hypothesis?

A. Nuclear fusion
B. Planetary accretion
C. Gravitational interaction between stars
D. Magnetic reconnection

5. In the Tidal Hypothesis, what happens to the ejected material from the Sun?

A. It forms a new star
B. It dissipates into space
C. It cools and condenses into planets
D. It forms a black hole

GS Mains Questions and Model Answers

Q1: Discuss the Tidal Hypothesis as an explanation for the formation of the solar system. What are its strengths and limitations?

Answer: The Tidal Hypothesis, proposed by Jeans and Jeffreys, suggests that the solar system was formed due to the gravitational interaction between the Sun and a passing star. The tidal forces generated by this encounter caused the ejection of material from the Sun, which later condensed to form planets.
The strength of this hypothesis lies in its explanation of the distribution of planets and their orbits. However, it has several limitations, particularly in explaining how solid planets formed from the gaseous filaments and how planets acquired their angular momentum. Modern theories like the Nebular Hypothesis offer a more comprehensive explanation.

Q2: Evaluate the relevance of the Tidal Hypothesis in the context of modern astronomy.

Answer: While the Tidal Hypothesis provided an early framework for understanding the formation of the solar system, its relevance has diminished in light of more advanced theories such as the Nebular Hypothesis. The Tidal Hypothesis does not adequately explain the formation of solid planets or the distribution of angular momentum. Modern astronomical research has shown that planetary systems likely formed from the collapse of a protoplanetary disk, making the Tidal Hypothesis less applicable today. However, the hypothesis remains important as a historical stepping stone in the study of the solar system's origins.

Q3: Compare the Tidal Hypothesis with the Nebular Hypothesis in explaining the origin of the solar system.

Answer: The Tidal Hypothesis and the Nebular Hypothesis offer different explanations for the origin of the solar system. The Tidal Hypothesis suggests that a close encounter between the Sun and a passing star led to the formation of planets from material ejected from the Sun. In contrast, the Nebular Hypothesis posits that the solar system formed from the gradual collapse of a rotating cloud of gas and dust (the solar nebula).
The Nebular Hypothesis is widely accepted today as it explains the distribution of angular momentum, the formation of solid planets, and the presence of a protoplanetary disk, which the Tidal Hypothesis does not address. As a result, the Nebular Hypothesis is considered a more comprehensive model.

Previous Year Questions on Tidal Hypothesis

1. UPSC CSE Prelims 2019

Question: Which of the following theories explains the formation of the solar system through a close encounter between the Sun and another star?
A. Nebular Hypothesis
B. Big Bang Theory
C. Tidal Hypothesis
D. Steady State Theory

Answer: C

Explanation: The Tidal Hypothesis explains the formation of the solar system as a result of a close encounter between the Sun and another star, which led to the ejection of material from the Sun.

2. UPSC CSE Mains 2020 (GS Paper 1)

Question: Explain the Tidal Hypothesis of Jeans and Jeffreys and discuss its limitations in explaining the origin of the solar system.

Explanation: The Tidal Hypothesis, proposed by Jeans and Jeffreys, suggests that the solar system was formed due to the gravitational influence of a passing star, which caused tidal forces that pulled material from the Sun. This material later condensed into planets. However, the hypothesis faces several limitations, such as its inability to explain the angular momentum of the planets and the process of forming solid planets from gaseous filaments. Modern theories like the Nebular Hypothesis provide more accurate explanations for these phenomena, making the Tidal Hypothesis less relevant in contemporary astronomy.