4 Theories of Origin of Earth – Part – 1 YouTube Lecture Handouts
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Origin of Earth
Gaseous Mass Theory – Kant
Nebular Theory – Laplace
PLANETESIMAL Theory – Chamberlin & MOULTON
| Nebular Hypothesis | Planetesimal Hypothesis |
| Hot & gaseous nebula from which number of rings were formed & separated due to centrifugal force. | Cold nebula (sun) from which mass was ejected due to attraction of an intruding star. |
| Rings became planets due to condensation & consolidation of hot & gaseous mass of the nebula. | Small planetesimals accreted & aggregated with the nuclei of big planetesimals to form planets. |
| Planets & satellites were originally hot & large & gradually cooled & grew smaller. | Planets & satellites were originally cold & small & gradually heated & became larger. |
| Outer most planets were formed first & others at later periods. | Planets & satellites were formed at the same time. |
| Earth always had an atmosphere. | Initially earth was without an atmosphere. |
Tidal Theory – Jeans and Jeffreys
| Tidal Hypothesis | Planetesimal Hypothesis |
| Molten hot mass of sun was ejected by the gravitational pull of the intruding star | Cold mass of sun was ejected by the attraction pull of the intruding star |
| Planets were formed by the cigar shaped filaments resulting in planets larger in the center & smaller towards the ends | Ejected cold mass of sun was scattered & planets formed without any defined sequence in their size & arrangement |
| Planets & satellites originally were hot & gradually cooled down | Planets & satellites were originally cold & gradually heated with collision of planetesimals around their nuclei |
| It says that the molten hot mass of sun was ejected by the gravitational pull of the intruding star | It says that cold mass of sun was ejected by the attraction pull of the intruding star |
✍ Manishika