How the planets get their spherical shape

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Discussion Overview

The discussion centers on how planets achieve their spherical shape, particularly in the context of their formation processes. Participants explore various theories related to planetary formation, including the roles of gravity, hydrostatic equilibrium, and the conditions under which planets form from stellar materials.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants suggest that gravity is the primary force that shapes planets into spheres, with one noting that once a protoplanet reaches a certain radius, gravity compresses it into a spherical form.
  • Others introduce the concept of hydrostatic equilibrium, stating that a sufficiently massive celestial body will assume a shape that balances gravitational forces and internal pressure, resulting in a spheroid.
  • There is a contention regarding the formation process of planets, with some asserting that planets form from a nebular hypothesis rather than a big explosion, while others question the necessity of an explosion in the formation process.
  • A participant recalls an experiment involving particles in a space station that formed into a spheroid shape, suggesting that this behavior is natural.
  • Another viewpoint posits that an initial explosion or shockwave could facilitate the formation of a condensate, which would then lead to gravitational attraction and subsequent planet formation, while also noting that planets are not perfect spheres due to their spin.

Areas of Agreement / Disagreement

Participants express differing views on the mechanisms behind planetary formation and the necessity of an explosion in this process. There is no consensus on whether planets form from explosions or through other processes like the nebular hypothesis.

Contextual Notes

Some claims depend on specific definitions of terms like "explosion" and "accretion," which may not be universally agreed upon. The discussion includes unresolved aspects of how gravitational forces interact with other factors in shaping celestial bodies.

lalu
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how the planets get in spherical shape if the they are formed by a big explosion ?
 
Astronomy news on Phys.org
Spheres of matter are the most stable shapes when pitted against the relentless force of gravity.

- Warren
 
lalu said:
how the planets get in spherical shape if the they are formed by a big explosion ?

and they weren't formed by a big explosion :)

google accretion disk and solar system formation

cheers
Dave
 
Planets get a spherical shape from gravity. Once a protoplanet (Baby Planet) reaches a certain radius, gravity crushes it into a spherical shape.
 
The key concept you're looking for is hydrostatic equilibrium. If a celestial body is massive enough, its gravity will cause it to assume the optimal shape which balances gravity and pressure. This is a spheroid.
 
If I remember correctly, there was an experiment with particles in the space station (wasn't it salt?) and the particles formed together in a spheroid shape.

It is natural.
 
I thought that planets needed an explosion (shockwave) to be formed out of nebulae... for example an explosion would allow a condensate (not like the boson ones) to be formed -as an origin of initial gravitational attraction- and thus the whole gas around would start "falling" into that and form the planet.
Due to the geometry of a sphere, it's the most favorable (energetically) shape to be formed... of course it's not a perfect sphere (for example the spin makes it more like an oval).
 

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