Enlarging Planetary Orbits: Evidence of the Solar System's Evolution?

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Discussion Overview

The discussion centers on the potential enlargement of planetary orbits over time and whether planets are moving further from the Sun. It explores both observational evidence and theoretical considerations regarding orbital changes in the solar system.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions if there is evidence for the enlargement of planetary orbits and whether planets are moving further from the Sun.
  • Another participant notes that orbits change their semi-major axis frequently due to gravitational influences, mentioning a long-term outward trend as the Sun loses mass, but emphasizes that short-term variations dominate observable changes.
  • A participant references evidence of significant orbital changes during the early years of the solar system, linking to a NASA article.
  • Additional information is provided regarding two tables that show how orbital elements change over different time periods, highlighting that the Earth's orbit increases on average over a shorter time scale but decreases over a longer time scale.

Areas of Agreement / Disagreement

Participants present multiple competing views regarding the nature and evidence of orbital changes, and the discussion remains unresolved with no consensus reached.

Contextual Notes

Participants reference specific time periods and data sources, indicating that the discussion is influenced by the limitations of available observational data and the complexities of gravitational interactions.

Sanborn Chase
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Is there any evidence of the enlargement of planetary orbits over time? Are the planets moving further from the sun?
 
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The orbits change their semi-major axis all the time, in both directions, based on the gravitational influence of other objects. There is a long-term trend outwards as the Sun loses mass, but over timescales we can observe this is completely drowned by the short-term variations.
 
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Thanks for your response, mfb. It's a great help.
 
To add to mfb's reply, here are two tables which give how orbital elements change with time.
The first is over the time period of 1800AD-2050AD:
https://ssd.jpl.nasa.gov/txt/p_elem_t1.txt

and the second for the time period of 3000BC-3000AD
https://ssd.jpl.nasa.gov/txt/p_elem_t2.txt

Note that in the first column (a), which gives the average orbital distance in AU and the change in AU per century, the Earth's orbit (EM bary), increases on average over the shorter time scale, but decreases on average over the longer time scale.
 
Thanks, Guys.
 

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