Planetesimal Hypothesis Of Chamberlin & Moulton

         T.C.Chamberlin, a geologists, in collaboration with Forest  Ray Moulton, an astronomer postulated a new hypothesis called Planetesimal Hypothesis in 1905. It not only explains the origin of the earth, but, also throws light on the structure of the earth, the origin of its atmosphere, continents and also ocean basins.

The origin of the earth:

       The planetesimal hypothesis envisaged the origin of the solar system with the help of two heavenly bodies. According to Chamberlin initially there were  two heavenly  bodies in the universe ; Proto-sun and its companion star. The behaviour  and properties of the proto – sun were not like other stars. It was formed of very small particles which were  cold and solid  and circular in shape.  There was another star, termed as ‘Intruding  star’  of ‘companion star’  which was destined  to pass very close to proto-sun infinite number of  small particles were detached from the outer surface of the proto-sun  due to massive gravitational pull exerted by  the giant intruding star. Chamberlin termed these detached  small particles as planetesimals.
       Initially the detached particles or planetesiamls  were just like dust particles. The planetesimals were not uniform size rather a few planetesiamls around the proto- sun were of fairly big size. These larger planetesimals became nuclei for the formation of future possible planets. Gradually large planetesimals started attracting small planetesimals.  Thus, numerous small planetesimals  were accreted  to the nuclei of large planetesiamls  and ultimately these large planetesimals grew in the form of planets due to continuous accretion of infinite number of planetesimals. With the passage of time, the remaining proto- sun changed into the present day sun. The satellites of the planets were created due to the repetition of the same process and mechanisms.


The followings are a few major points on which his hypothesis was criticised and discarded by various scientists.

    1.   According to many astronomers the planetesimals would have so volatized due to excessive heat of friction  and collision at the time of their ejection from the ‘proto- sun’ that it would have been impossible for them to condense in the form of orbits around the ‘proto-sun’ without being defused  violently in the universe. Under these circumstances  the equation of accretion and aggregation of planetesimals around the ‘proto-sun’ in condensed form of planets does not arise.
    2.  According to the ‘planetesimal hypothesis’ by Chamberlin, the size of the planets were dependent upon ;
      • The amount of accretion and aggregation of planetesiamls around the nucleus.
      • Amount of planetesimals available in the particular orbit. And
      • The attractional force  of the so-called nucleus of the planets.
However, the planets of our present day solar system are arranged according to their size around the sun in a systematic  order.  But, chamberlin ‘s hypothesis, does not offer any explanation for this type of arrangement of the planets in our solar system.
  1. Why only nine planets were formed? Why not one more or one less? No answer offered by Chamberlin.
  2. The infinite space of the universe makes such a close encounter between the stars a  remote possibility.
  3. The planetesimal hypothesis does not explain the present higher amount of our solar system.
  4. There  is no explanation  in Chamberlin’s hypothesis about the planets of the outer circle which are of very low densities and are in gaseous state.


  • K.Siddhartha – “The Earth’s Dynamic Surface”
  • S.Singh – Geomorphology
  • Strahler & Strahler – Physical Geography
  • M.J.Shelby – Earth’s Changing Surface

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