Aug 21 2017

Solar Eclipse and Coincidence

solar-eclipse-2017Today there will be a total solar eclipse making its way all across the continental US, from Oregon to South Carolina. Unfortunately I could not logistically travel to see it first hand. I’ll have to wait for 2024, when another total solar eclipse will hit America, making a trail from Texas through upstate New York. Here in CT we will get 75% coverage, which will be cool but nothing (from what I hear) like seeing totality.

Eclipses are one of the testaments to the power of science. We can predict them with incredible accuracy, because we have worked out in tiny detail how planetary orbits work. We can make careful observation and combine that with accurate theories about how the universe works and mathematics to make calculations, and predict these celestial events far into the future.

Some people, however, choose to see the eclipse as a testament to the existence of God. I first heard this argument when I was in college – a friend of mine who was also a fundamentalist Christian essentially ridiculed me for thinking that eclipses were just coincidence. The hand of God was clearly at work.

Eric Metaxas, who has a history of seeing God in the details of reality (as I have discussed before), has also unsurprisingly seized upon this argument. He writes:

What might be the odds of this just happening randomly? Almost all the planets in our solar system have no moons or many moons (Jupiter has 60) of incredibly varying sizes. So this sort of thing doesn’t happen anywhere else in our solar system. But our planet has just one moon that happens to be just the right size and just the right distance from Earth.

I found the precision necessary for all of this unbelievable. The more I thought about it, the more I knew that there was no way this could be a mere coincidence. It seemed almost planned. In fact, it seemed utterly planned, as all things of such precision must be.

Must it? It is an amazing coincidence that the apparent size of the moon and the sun as viewed from Earth overlap. The size of both vary over time. The apparent size of the sun varies by 3.3% and the moon by 10% because the orbits of the earth and moon are slightly elliptical. So they are not precisely the same size – their variability overlaps.

The apparent size of the moon has also been changing over historical time. The moon was once much closer to the Earth. It moves away from the Earth by 3.8 centimeters per year due to tidal forces which also have locked the moon’s rotation to the Earth, and will one day lock the Earth’s rotation to the moon. So we happen to be living in a window of about 100 million years where their apparent sizes overlap.

The fact that the sun and moon are in the same plane is not a coincidence at all. That is how solar systems develop. Most of the objects in the solar system are in roughly the same plane.

So it is actually not that much of a coincidence. Many planets have large moons like our own. If we think about 100 million years vs a 10 billion year lifespan of our solar system, that is 1/100 or 1%. That is small but not that small. Further, we are much more likely to be living in the middle of our sun’s lifespan, not at the very beginning or end, so the actual odds are greater than 1% of us falling within that window.

Metaxas is also committing the Texas Sharpshooter fallacy. There are many astronomical details of the universe, if we consider the size, position, orbits, and arrangements of all the bodies in our solar system. We could have had multiple moons that eclipse each other. We can also consider the apparent position of stars as viewed from Earth. We could also have had naked-eye viewable phenomena, like nebula, satellite galaxies, or globular clusters. Our sun may have been outside the plane of our galaxy, with a view of the spiral disk face-on.

Therefore, we cannot consider only the odds of having a moon and living in a window in which that moon eclipses our sun. We have to consider the odds of there being any astronomical coincidence – any at all. Metaxas is deciding after the fact that this one coincidence is evidence of God, but he could have said that about any cosmic coincidence (and he does). There is no reason a priori to conclude that eclipses specifically are evidence of divine tinkering.

So – what are the odds that, from the perspective of earth, there would be some (any) astronomical coincidence? It’s impossible to calculate such odds. But the fact that a 1% or so coincidence does exist hardly requires postulating divine interference, and certainly is not proof of God.

When you experience the eclipse today (if you are in its path) rejoice about the predictive power of our science. And be safe – everyone probably knows this now, but it is worth repeating. Don’t look at the sun at anytime during the eclipse. The exposed part of the sun can still damage your retina. If you are using lenses, make sure they are approved and actually work.

Happy eclipse day.

35 responses so far

35 thoughts on “Solar Eclipse and Coincidence”

  1. Ian Wardell says:

    “Many planets have large moons like our own”.

    Do you mean a large moon relative to the planet like the Earth-Moon? Name these planets and moons please.

  2. Nareed says:

    Totality is unlike anything else we ever experience. If we divide the time of day into dawn, day, dusk and night, you need to add another time of day: totality.

    Not to mention it’s the only time you can see the Sun’s atmosphere (Corona), and the only time when you’re likely to see Mercury and Venus share the sky with other planets.

    I’m aiming for the 2024 Eclipse as well. I was in the path of totality in 1991 and it was awesome.

    On the topic of views from various planets and moons just in our Solar system, Earth may also be unique in that its inhabitants cannot see any satellite other than their own with the naked eye. Our Moon is large enough to be easily visible, at times, from at least Mercury, Venus and Mars (in the latter as a morning/evening star only).

  3. Ian – no, that is not what I meant, and not what I wrote. I only stated that there are other moons of similar size to our own in the solar system, indicating that the existence of the moon itself is not unique or necessarily unlikely.

  4. BillyJoe7 says:

    So why did god do that? Was he just showing off?

  5. Ian Wardell says:

    Steven Novella said:
    “[T]he existence of the moon itself is not unique or necessarily unlikely”.

    This is certainly not my impression. Compared to any other planet-moon systems, the moon is very large and very close to the Earth. Indeed, in order to to explain the moon, I think it is hypothesized that a planet the size of Mars slammed into the Earth! This seems somewhat unlikely and contrived.

    It also has been argued that were it not for the existence of such a large moon close to the Earth, then life may have never began on the Earth. Moreover, if it is very rare to have such a large moon relative to the planet, and such a large moon is necessary for life to arise, this in turns suggests that life in the Universe will be very rare. And Earth-like planets that we can colonise will be very rare too (not that we could ever get to them anyway).

  6. jwadamson says:

    There are moons capable of causing total eclipses on Earth, Jupiter, Saturn, Uranus and Neptune (also Pluto). That doesn’t make it seem that rare (can’t land gas giants though). Five of 8 (or 6 of 9)

    Really just Mercury, Mars, and Venus lack sufficient satellites.

    Relative sizing of moon to parent does not affect ability of eclipse, just absolute size and distance of moon vs absolute size/distance of sun.

  7. Ian – we simply don’t know. We have no surveys of other solar systems, including their moons, to know how likely the Earth-moon pair is. We cannot extrapolate from just our system, way too little information.

    It is also not true that life requires us to have a moon like we do. Existing life might, but of course life evolved on Earth and is adapted to Earth, which includes the influences of the moon. Life on Earth would be different without the moon, no doubt.

    Again – too little data to make any statements about probability.

  8. JimV says:

    Off the top of my head, Pluto and Charon are two large, semi-spherical objects which rotate around each other in our solar system, of similar size ratio to the Earth and its Moon.

    Also, there is at least one other moon in our solar system which closely matches the Sun’s apparent size as it would be viewed from the moon’s planet, and causes eclipses as they would be seen from that planet. I read this years ago in some science magazine. I think the planet was either Jupiter or Saturn (from which the Sun has a small apparent size, so a small moon works).

    It probably is unusual in this universe to find other planets suited to the types of life found here, which depend on things like liquid water and tides – but then evolution has had a long time to adapt life to those conditions. A form of life which used liquid methane would probably be much more suited to this universe, in terms of available habitat. Anyway, wherever life is found, it will be adapted to whatever conditions are found there, no matter how unique they are, according to the principles of evolution.

    “It’s unusual and I don’t understand how or why it occurred, so God must have done it,” is more like giving up than a useful explanation. (I like to call it the “God ate my homework” explanation.) It leaves the “why” and “how” unanswered, in practical terms.

    Newton is said to have wondered why most of the large objects in the solar system (known at the time) were in the same plane. They had tennis then, but it wasn’t very common. Anyone who hits a wet tennis ball (with a tennis racket, using top-spin) can observe part of the explanation.

  9. michaelegnor says:


    You make an intetesting argument. You argue that eclipses are insufficient coincidences to infer God. You therefore argue that sufficient coincidence is possible (insufficient presupposes the possibility of sufficient).
    Anthropic fine-tuning arguments cite much more remarkable coincidences in the laws of physics. Are all of these insufficient, and if so, what would be sufficient?

  10. SteveA says:

    So the Lord is content to show off his divine majesty by giving us ‘nice’ eclipses? But not by doing anything useful, like eliminating leukaemia?

    What an asshole.

  11. Michael – Technically, saying that a 1% coincidence does not require invoking God does not mean a greater coincidence does. That is invalid logic. There are other concerns as well – mainly the sharpshooter fallacy. I would add that, it’s a big universe, and highly unlikely individual things will happen.

    With regard to the laws of physics, we don’t know what the real odds are that they are what they are. We don’t know that the laws are fine tuned for life, rather than life being fine tuned for the laws. There may be infinite universes out there, or the laws may need to be what they are for some reason.

    We simply don’t know enough to make any statements about probability when it comes to fundamental things like natural constants. Saying, therefore, that goddidit is a classic god-of-the-gaps argument.

  12. JustAnotherSkeptic says:

    To Michael’s point:

    “The amount of horrible disease present on the planet is not enough evidence to conclude that god doesn’t exist” which I think that Michael would agree with.

    does not imply that

    “There exists an amount of horribleness that would disprove god.”

    This is the equivalent leap that Michael has made concerning Steven’s point that “this coincidence is not evidence for god.”

  13. DisplayGeek says:

    Discussions like this always frustrate me in that we rarely discuss the much more likely possibility of habitable worlds in other star systems will be “moons” of smaller gas giants in the star’s habitable zone. Given that these “moons” will likely be orbiting their parent giant at a greater distance, the relative apparent size of the parent may be similar to that of the star (sun). In this manner, such sights may be far more common than is generally recognized.

    The true enigma of the Terra / Luna (the double planet system) is that they orbit each other nearly along the ecliptic. Except for bodies that are captured later (e.g. the asteroids now orbiting Mars), one would expect that they would orbit along the parent’s equator as happens with Jupiter and Saturn, as they form from the same local eddy of dust and gas. But Earth’s axis is tilted and precesses… yet the Moon, though it is clearly tidally locked to the earth, formed in such a manner that it orbits predominantly along the ecliptic. To me, this says that the model for their formation must explain this feature…

  14. michaelegnor says:


    Insufficient presupposes the possibility of sufficient. The logic is clear.

    Im not a fan of anthropic arguments. I think they are examples of Gods agency, but proof of His existence is in something much simpler: teleology in nature, which is the tendency for natural processes to hew to ends. That is Aquinas Fifth Way.

  15. As I just said, but perhaps was not explicit enough, the converse is not implied because there are other factors to consider. The coincidence, by itself, is not enough, but even if it were more impressive the argument still fails for other reasons, which I pointed out.

  16. jwadamson says:

    I’m honestly trying to work out if “Insufficient presupposed the possibility of sufficient” is valid. Take the statement “the Saturn V rocket has insufficient thrust to escape from inside the event horizon of a black-hole”, does this presuppose there is the possibility of something with sufficient thrust to do so?

  17. michaelegnor says:

    Insufficient implies the possibility of sufficient. If there is no possibility, there is no meaning to ‘insufficient’. Insufficient is modal, and it implies a range of possibility that extends to sufficient. Its like saying ‘not wet enough’ implies the possibility of ‘wet enough’.

    The proper word for the event horizon example is ‘can not’, which does not imply can. Can not is not modal- it is just a statement of fact.

  18. JustAnotherSkeptic says:

    Here is a demonstration where “insufficient presupposes the possibility of sufficient” is wrong:

    “The presence of horrible disease is not sufficient evidence to prove that god doesn’t exist.”

    This statement does not imply the possibility of sufficient evidence. I think Michael will agree with the statement above, but he probably won’t also conclude that the above statement says that there is a sufficient amount of disease that would definitively refute god’s existence.

  19. the black hole is not a good example. My point is that other factors are at work.

    A better analogy – I have insufficient money to afford a dragon egg, but even if I were wealthy I still couldn’t buy one because they don’t exist.

    The level of coincidence here is insufficient to even be interesting, but even if it were such GOTG arguments fail on other logical flaws.

  20. michaelegnor says:


    I agree that coincidences arent a strong proof of Gods existence. We dont know the ensemble of possibilities, so we dont know how unlikely the coincidence is.

    But the Teleological Proof of Gods existence is very strong.

  21. Pete A says:

    “[Egnor] The proper word for the event horizon example is ‘can not’, which does not imply can. Can not is not modal- it is just a statement of fact.”

    Are your sure? During my career (which was not within the USA) it was mandated that I clearly expressed whether I was talking about “does not” or “cannot”: “does not” clearly expresses the fact that it does not occur in reality / there is zero evidence that it has ever occurred in reality; whereas “cannot” clearly expresses the fact that it cannot occur in reality according to well-established current scientific and/or mathematical theories.

    E.g., “2×2 = 8 does not, and cannot, occur in linear scalar algebra” succinctly expresses both of these facts. Whereas “connot” implies only that it has been predicted to never occur, while saying nothing about the facts regarding whether or not it has occurred.

    See also:

    1) The words “insufficient” and “sufficient” are not modal verbs, they are a determiner and an adjective:

    2) Just because a word has an antonym in a dictionary does not imply that its antonym is valid within the specific context in which the author used the word: because very few people speak or write perfect up-to-date English — including Michael Egnor!

  22. bachfiend says:


    ‘But the Teleological Proof of Gods existence is very strong’. You forgot to put in the apostrophe. Did you mean “‘God’s’ or ‘Gods'”? How do you know that your creating god(s) weren’t actually evil and malicious instead of your loving God who put humans on an Earth with earthquakes and tsunamis, such as the Great Lisbon earthquake on All Saints Day in 1755, causing the cathedral to crush his believers while they were adoring him?

    It’s just the sharpshooter fallacy yet again.

    The Earth-Moon system is unusual for the solar system. We don’t know how unusual it is for the Universe, which is an enormous place with at least 10^22 stars in the visible Universe. We also don’t know how many of its properties are necessary for life, let alone intelligent life, to have developed, let alone persisted.

    The conditions on the Earth when life first originated, 3.8 billion years ago, weren’t the same as they are today. For a start, the Earth had only cooled down from the Hadean eon several hundred million years earlier.

    The conditions allowing life, including intelligent life, to persist today on Earth are many, including the presence of liquid water – which requires the existence of atmospheric greenhouse gases. At the Earth’s distance from the Sun, the Earth should be frozen over, with an average temperature of -18 degrees instead of 15 degrees (33 degrees of warming). And a relatively stable level of greenhouse gases, which requires the existence of liquid water and tectonic plate geology, which is part of the carbon cycle. When atmospheric CO2 levels increase, the Earth warms, there’s increased rain and increased weathering of rocks causing increased deposition of carbonate containing sedimentary rocks (reducing atmospheric CO2 levels), which are recycled into the crust by tectonic plate movements, and then volcanic activity eventually causes the CO2 to be released back into the atmosphere.

    What you regard as a necessary part of God’s plan, I regard as being a temporary set of settings allowing conditions to be as we know them currently to be. Conditions on Earth have varied greatly over time, including the ‘Snowball Earth’ 650 million years ago, when there were glaciers at sea level at the Equator. But not so greatly that there has been runaway conditions such as happened on Venus (with Venus’ albedo, it should be absorbing less solar radiation than the Earth, and be cooler, but it’s considerably hotter).

  23. Ian Wardell says:

    michaelegnor, you’ll probably be aware, but there’s a new book coming out soon by Edward Feser called:

    Five Proofs of the Existence of God

    I’ve pre-ordered it.

  24. bachfiend says:

    Ian (read my blog) Wardell,

    Feser’s latest book has already been released. It was released on August 18, 2017, but it sold out (his mom apparently bought all the copies printed). It’s only available as the direct to paperback ‘dead tree version’, not as a Kindle version to my disappointment (not).

    I won’t be buying it. Egnor is perfectly capable of giving a chewed over account of the ‘arguments’ such as they are.

  25. michaelegnor says:


    I look forward to Fesers new book.

  26. tmac57 says:

    Let’s be clear. If we discovered sometime in the near future that every planet in our solar system supported life, and then every planet in the nearest star system did as well (and so on), that all of that new found information would either be cited as ‘proof’ of god, or denied as being true by some portion of believers.
    You all have seen this game right? Every advancement of knowledge is either leveraged to their side or condemned as false.
    There is no possible set of circumstances that cannot be tweaked into supporting an ideology that is basically based on what boils down to ‘a feeling’ that it is true.

  27. bachfiend says:


    I wonder. I don’t think Christians would have too much in the way of problems if bacteria were found on Mars. I think that they’d have some problems if intelligent life was found on a planet orbiting, say, Tau Ceti just 12 light years from the Sun.

    Their sophisticated theologians (TM) would have to decide, in the absence of any data, whether the intelligent Tau Cetians are either God’s creations, with their own Jesus who sacrificed himself to himself in order to get absolution from their original sin, or creations of Satan and needing to be exterminated.

  28. bachfiend says:


    ‘I look forward to Fesers new book’.

    But apparently not to using apostrophes when appropriate in order to indicate possession.

  29. Gingerbaker says:

    “‘But the Teleological Proof of Gods existence is very strong’. ”

    It sure is – so strong that Socrates used it to prove the existence of Zeus. Convincing, yes?

  30. Pete A says:


    I’m honestly trying to work out if “Insufficient presupposed the possibility of sufficient” is valid. Take the statement “the Saturn V rocket has insufficient thrust to escape from inside the event horizon of a black-hole”, does this presuppose there is the possibility of something with sufficient thrust to do so?

    The statement about the Saturn V rocket is the conclusion of an argument of which we do not know its premises. It is, I think, reasonable to infer that the premises included an estimate of the thrust that would be required to escape from inside the event horizon of a black hole.

    The word “insufficient” is clearly inferring “not enough”, “less than the amount required”, “inadequate”. E.g. The thrust of the Saturn V rocket is not enough to escape from inside the event horizon of a black-hole. The unstated premises of the argument being along the lines of:

    P1. The thrust required to escape the event horizon of a black hole is T.
    P2. The thrust of the Saturn V rocket is R.
    P3. R is less than T.
    C. Therefore, the Saturn V rocket has insufficient thrust to escape from inside the event horizon of a black hole.

    The words “insufficient” and “sufficient” are adjectives and determiners. In the above argument, the word “insufficient” (therefore its antonym “sufficient”) is referring to thrust T.

    So, “Insufficient presupposed the possibility of sufficient” is valid when the two words are being used correctly as determiners.

    Now let’s examine the final clause of your comment: “…, does this presuppose there is the possibility of something with sufficient thrust to do so?”. For this, let’s firstly examine propositional logic of the form “If P then Q”:
    the “If P” clause is the antecedent and
    the “then Q” clause is the consequent.

    This tells us four things (because there are four possible states of PQ):
    1. when the antecedent P is true, the consequent Q must also be true;
    2. when the consequent Q is false, the antecedent P must also be false;
    3. when P is false, Q can be true for reasons other than P being the only logical cause;
    4. when Q is true, it cannot inform us as to whether or not P is true: see Item 3.

    Misuse of 3 & 4 results in the formal fallacies:
    3. “Not P, therefore not Q” is the formal fallacy denying the antecedent;
    4. “Q, therefore P” is the formal fallacy affirming the consequent.

    We’ve established that the thrust of the Saturn V rocket is less than the determiner thrust, T, which would be required for the rocket to escape from the event horizon of a black hole. Let’s put this into the form “If P then Q”:

    P = “If the rocket thrust is less than T”
    Q = “then it will not be able to escape the event horizon of a black hole”
    P is true and Q is true, which is valid.

    Now let’s make P false and examine the counter-claim: “Well, Pete’s penta-turbo Saturn V exceeds thrust T therefore it would be able to escape the event horizon of a black hole.”

    This counter-claim contains the formal fallacy denying the antecedent (Items 3. above): Not P, therefore not Q. There are, of course, other practical reasons why my rocket, despite it having sufficient thrust, would be unable to escape the event horizon of a black hole: Q can indeed remain true when P changes from true to false.

    Applying this to your final clause “…, does this presuppose there is the possibility of something with sufficient thrust to do so?” — the logically valid answer is: No, it does not.

    NB: Neither does it logically preclude the possibility of something with sufficient thrust to do so. E.g., Hawking radiation aka Hawking-Zel’dovich radiation.

  31. Donna B. says:

    I’m really tired of the argument about whether God or gods exist or not. Does it matter? If he/she/it does exist, it’s obvious he/she/it created at least this universe, us, everyone, and everything else in it so the arguments are about what we don’t yet know and understand. If he/she/it does not exist… what exactly changes? We still don’t yet know and understand. (After having worked in journalism and publishing for some time, I’m just going to laugh at anyone who quotes any of the multiple versions of the Bible. Great stories there, perhaps even some history, but proofs? No.)

    As long as your religious beliefs don’t require you to kill, shun, or convert anyone and/or everyone else, I really don’t care. Go for it. And don’t worry about my soul or happiness now or in the future. Oh wait… most religions do require one or more of those, don’t they? Then, just sod off and leave me alone. If I decide to worship a god, it will be one who prefers universes with awesome eclipses for our enjoyment rather than threats of terror if we don’t do/believe whatever.

    I was fortunate to view the totality in SC this year. And there is nothing like it. Incredible, awesome, WOW… no superlative is quite superlative enough. We were extra excited because clouds and rain earlier in the day had us all convinced we’d have to be happy with good company, food, and drink without the view. “God” loved us and let us see it although apparently hated the people a 1/2 mile east of us. Perhaps it was our offering (er, I mean devouring) of homemade moon pies?

    We did remove the lenses during the totality as there was almost nothing visible through them. I’m seeing my ophthalmologist later this week and I’ll ask him if we did a major no-no. Not that it can be changed now.

  32. BillyJoe7 says:


    “I’m really tired of the argument about whether God or gods exist or not. Does it matter?”

    It depends on which God or god you’re talking about.
    If you’re talking about a deistic god then, no, it makes not a scrap of difference.
    If you’re talking about a personal/interventionist god then it makes a heap of difference.

    “As long as your religious beliefs don’t require you to kill, shun, or convert anyone and/or everyone else, I really don’t care”

    So there’s your answer.
    Almost all believers believe in a personal/interventionist god.
    And some fundamentalists try to restrict your freedom by imposing their views politically.
    Some fundamentalists even think it is their duty to kill you in certain circumstances.

  33. Donna B. says:


    ” “As long as your religious beliefs don’t require you to kill, shun, or convert anyone and/or everyone else, I really don’t care”

    So there’s your answer.”

    Quote out of context much? The following sentence reads “Oh wait… most religions do require one or more of those, don’t they?”

    Feel free to believe that sentence after that one includes you.

  34. bachfiend says:


    It’s perfectly safe, and strongly recommended, to look at the sun during, and only during, totality in a total solar eclipse. It’s not safe to look at the sun when part of the disc isn’t covered by the moon.

    I’m glad you enjoyed the total solar eclipse. I saw one in Novosibirsk in 2008, and it was fantastic. Totality with a cloud free sky is better – you also get to see the stars. And planets. In the middle of the day.

    I’m thinking about going to the total solar eclipse in Greenland in 2026. I wonder if the aurora borealis would be visible during totality, which would be an extraordinary experience (seeing the sun’s corona and stars at the same time is amazing enough).

    I’ll decide closer to the year, researching what the usual weather/cloud cover is like in Greenland around the time of year of the eclipse.

    The next best one for me is the one in Western Australia in the Kimberley on July 22, 2028, with totality lasting an incredible 5 minutes. And Northern Australia is usually cloud free in July and August.

  35. BillyJoe7 says:


    Apologies, maybe I misread you.

    But it puzzled me that you asked a question which seemed to imply that you think arguments about the existence or non-existence of gods don’t matter:

    “I’m really tired of the argument about whether God or gods exist or not. Does it matter?”

    But that the rest of your comment seems to indicate that you think that it does matter.
    Anyway, no big deal.

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