Essay on The Nebular Hypothesis of Immanuel Kant

E. Kant, the famous German philosopher, propounded the Nebular Hypothesis of the origin of the earth in 1755. Kant introduced the Newton’s law of gravitation in his hypothesis.

It was his assumption that the hard particles of supernaturally created primordial matter collided with each other by gravitation attraction. Because of collision heat and rotation generated.

Kant believed that the particles of the primordial matter were motionless and cold. But because of heat generated due to their collision a vast gaseous mass, which he called nebula, came into existence.

The nebula thus formed started rotating with such great rapidity that strong centrifugal force was produced about the equatorial plane. This caused the throwing off successive rings of the primordial matter.

Later on these rings condensed in planets. What remained of the original nebula became the sun.

The planets while spinning like the original nebula threw off rings which became their satellites. In this way the complete solar system, as it exists today, came into existence.

Kant’s hypothesis is regarded as dynamically unsound because he assumed that interaction between the particles of the same body could change the rate of rotation.

This assumption that rotation could be set up in the nebula by the collision of its particles is against the principle of the ‘conservation of angular momentum’.

It is to be noted that this principle asserts that no interaction between the different parts of a system will change its total amount of rotation; measured in terms of angular momentum, the total rotation remains the same for all time. Kant failed in his attempt to explain the rotation of the nebula.

It may be pointed out that Kant put forth his hypothesis when he was ignorant of the behaviour of the gases and the elements. It was after about two centuries that the knowledge about the gases and elements could be gained.

Criticism:

The main grounds on which Kant’s hypothesis has been criticized are the following:

(i) Kant’s assumption that interaction between the particles of the same body could change the rate of rotation is against the principle of the conservation of angular momentum.

(ii) Kant failed to explain the rotation of nebula, while Laplace assumed that there was a rotating nebula already in existence.

(iii) Another erroneous assumption of Kant was that as the size of the nebula increased, the speed of rotation also increased. This is also against the law referred to above. It is a well known fact the speed decreases with the increase in size, and vice versa.

(iv) Kant did not explain the source of energy which could bring about the random motion of the static and cold particles of the primordial matter.

Even though Kant based his hypothesis on Newtonian law of gravitation, he appears to have ignored Newton’s first law according to which a body remains at rest, or if in motion it remains in uniform motion with constant speed unless and until an external force is applied to it.

(v) Kants’ assumption that the generation of rotational motion in the nebula was the result of the collision of particles of primordial matter is against the mathematical laws. It is against the principle of the conservation of angular momentum.

(vi) Kant did not consider Saturn’s rings as a clue to his hypothesis, but his ‘theoretical successor’ Laplace did so.

Despite various objections raised against Kant’s gaseous hypothesis, it is worthwhile to remember that he was the first scientist who ventured to probe into the unknown and the unresolved puzzle of the origin of the earth.

He has been justly acknowledging the forerunner of the very similar and justly famous Nebular Hypothesis of Laplace (1796) which has dominated cosmogony until recent times.

It cannot be denied this field has more scope for speculations as regards the basis of the origin of the Solar system and the earth. Remember that with the discovery of more and more cosmic facts even the later discoveries were discredited at different times because of their inherent short comings.