Would Two Identical Planets Opposite Each Other Coalesce Over Time?

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Discussion Overview

The discussion centers around the hypothetical scenario of two identical planets, positioned opposite each other across the sun, and whether they would coalesce over time. The scope includes theoretical considerations regarding planetary dynamics, gravitational influences, and the stability of orbits within the solar system.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that the two planets could eventually collide due to gravitational influences from other celestial bodies, suggesting that these influences would break the symmetry over time.
  • Others argue that while it is theoretically possible for the planets to coalesce, it is highly unlikely given the current dynamics of the solar system.
  • A participant notes that the solar system is not completely stable and could be disrupted by external large objects, although they later suggest that the likelihood of such events is negligible.
  • Another participant claims that if a second Earth existed, it would likely oscillate between trojan and horseshoe orbits with Earth, indicating that they would not come close enough to coalesce.
  • One participant questions why planets formed singularly if multiple identical planets could exist, referencing the accretion disc model of planet formation and suggesting that more objects should be present in Earth's orbit if this were the case.

Areas of Agreement / Disagreement

Participants express differing views on the likelihood of coalescence and the stability of the orbits of the two hypothetical planets. There is no consensus on whether they would eventually collide or remain in stable orbits.

Contextual Notes

Participants highlight the influence of other planets and external objects on the orbits of the hypothetical planets, but there are unresolved assumptions regarding the nature and magnitude of these influences.

pixel01
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Sometime ago, a guy asked about a scenario that if there were another Earth planet opposite to our Earth across the sun, could we identify it.
Now, my question is if the two finally would coalesce after some time?
 
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Is it possible that the two planets would finally colide because besides the sun, they also were influenced by other planets and these influences were not identical to the two. So the symmetry would be broken after sometime.
 
Yes, it's possible (though amazingly unikely!)

The solar system isn't completely stable, and could be messed up by something large coming from outside (or from the Oort cloud).
 
The odds of something large coming from outside the solar system are negligable. Oort Cloud objects are not massive enough to significantly disrupt anything.

If there were another Earth opposite our Earth it would spend its time jumping from trojan orbit to horseshoe orbit with Earth. They would not get very close to each other.
 
tony873004 said:
The odds of something large coming from outside the solar system are negligable. Oort Cloud objects are not massive enough to significantly disrupt anything.

If there were another Earth opposite our Earth it would spend its time jumping from trojan orbit to horseshoe orbit with Earth. They would not get very close to each other.

So why when the planets were formed, they were formed singularly. I means at the distance of Mercury, there is one Mercury, then one Venus, one Earth etc..
We know planets were formed from an accretion disc. If the 2 Earth could exist simultaneously, then there should have been many more smaller objects orbiting in the Earth's orbit now.
 

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