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Has our moon’s orbit shifted since its formation? Has there been eclipses on the Earth since last ~4 billion years? In other words, was there a time when Moon's orbit was at an inclination to Earth's orbit around the Sun that there were no eclipses? How would you find out such a phenomenon? Are there any paleontological or geological or astronomical data points which can provide insight here?

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    $\begingroup$ The moon did not exist from the beginning of the solar system. The moon was formed ~4.5 billion years ago, about 30–50 million years after the origin of the Solar System-sservi.nasa.gov/articles/… $\endgroup$ – Bob516 Apr 5 at 4:35
  • $\begingroup$ That’s important detail but inconsequential here. $\endgroup$ – sidharth chhabra Apr 5 at 8:35
  • $\begingroup$ I agree it does not answer the question, but it offers a better understanding of the history. That is why I left it as a comment and not an answer. $\endgroup$ – Bob516 Apr 5 at 13:21
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    $\begingroup$ @sidharthchhabra Why do you insist on wording the question with the phrase "since the beginning of the solar system" when that is inconsistent with the facts? $\endgroup$ – Bob516 Apr 5 at 15:15
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    $\begingroup$ @Bob516 you are right. I fixed that. $\endgroup$ – sidharth chhabra Apr 5 at 16:33
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It has increased in radius since the formation of the Earth-Moon system. There were eclipses since then. See Eclipse. enter image description here Hyperphysics

The only way you would not have (at least partial) eclipses is if the Moon's rotation were exactly synchronized so it never passed through the ecliptic plane near the favourable time.

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  • $\begingroup$ In the link you provided for eclipse there is no information about the past billions of years but only last 3000 years. $\endgroup$ – sidharth chhabra Apr 5 at 8:38
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    $\begingroup$ @sidharthchhabra That just explains the geometry of how eclipses happen. You will always get eclipses (at least partial) unless the year is miraculously some exact rational-number multiple of the month. $\endgroup$ – Keith McClary Apr 5 at 14:54
  • $\begingroup$ What is the evidence that there will certainly be eclipses? Can you please share some details behind your answer. If the inclination of the moon's orbit is more than say 30 degrees, would there still be eclipses? $\endgroup$ – sidharth chhabra Apr 5 at 16:37
  • $\begingroup$ Thank you Keith for putting in some more diagrams and information. In the illustration, moon's orbit has 5 degree tilt w.r.t ecliptic plane in left direction. Is it possible that moon's orbit was tilted at x degrees w.r.t ecliptic plane but in the direction of the Sun? In such a case, there won't be any eclipses. $\endgroup$ – sidharth chhabra Apr 5 at 18:00
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    $\begingroup$ @Keith Actually, the Moon's orbital plane precesses rather quickly, with a period of about 18.6 years, see en.wikipedia.org/wiki/Lunar_precession which also discusses the lunar apsidal and axial precession. But of course the lunar nodal precession does not undermine your argument about eclipses. $\endgroup$ – PM 2Ring Apr 5 at 23:25
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The distance between the Earth and the Moon increases by roughly 4 cm per year. So when it formed, it was much closer to Earth than it is now. This means that its angular diameter, as seen from Earth, used to be larger than that of the Sun. In the future, as the Moon keeps getting further away, its angular diameter will become smaller than that of the Sun, so during eclipses, the Sun will likely no longer be completely obscured.

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  • $\begingroup$ FWIW, it will take about 600 million years before the Moon will be too distant to cause total solar eclipses. $\endgroup$ – PM 2Ring Apr 5 at 23:28

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