This question asks what would happen to the solar system if the sun vanished for about three days, the mass and energy of the sun simply ceasing to exist. This answer (as of this question, anyway) notes that for the most part, the solar system will remain unchanged.

If Ragnarök has already happened, and the sun has already been eaten and replaced, is it possible to use the current eccentricity, positions, and speeds of the various planets in our solar system to determine how long ago that occurred?

As for an explanation of why this is in World Building rather than Physics: The events in Ragnarök result in sentient life on Earth being effectively wiped out; after the cataclysmic event, only two people remain, and civilization restarts through them and their children. There would be no written history of the event, and oral tradition is unreliable at best. There may not even be any archaeological evidence. However, the physics would remain, and "proving" that the sun vanished for three days is a pretty good step towards building a magical, unknown history into a normal, mundane world - through science, no less!

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    $\begingroup$ This is an interesting question but how is it about world building? $\endgroup$
    – James
    Oct 15, 2014 at 19:26
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    $\begingroup$ How is this offtopic for Physics? $\endgroup$
    – Telastyn
    Oct 15, 2014 at 20:02
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    $\begingroup$ How exactly did the sun vanish? Especially, did the mass remain in place? $\endgroup$
    – celtschk
    Oct 15, 2014 at 20:57
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    $\begingroup$ For current eccentricity, positions, and speeds of the various planets to be relevant wouldn't we need some type of pre-ragnarok measurements to help us account for the loss of the sun for 3 days? $\endgroup$
    – Culyx
    Oct 15, 2014 at 21:10
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    $\begingroup$ See also: worldbuilding.stackexchange.com/questions/2703/… $\endgroup$
    – Tim B
    Oct 16, 2014 at 12:11

3 Answers 3


The simple answer is no, we would never know. Not unless there are records from that time we could refer back to or we can use FTL travel to go far enough away that we can look back and see.

The resulting orbits afterwards are stable and we have no way of knowing that they were not always that way. Additionally anything that is odd in orbital configurations can be far more readily explained by something like a rogue planet passing through the system and disrupting things than the sun disappearing.

Essentially there are no tracks in space so we have no way of knowing that something odd happened at a certain point unless we have measurements both before and after that odd thing happened.

The only way it might be possible is if there were records from the pre-ragnarok civilization that were discovered and included precise details of the orbital tracks of the planets.

Comparisons between those records and now might make it possible to work out that the sun disappeared and how long it was gone for but it would take advanced astronomical and mathematical knowledge and detailed records from before.

  • $\begingroup$ "The resulting orbits afterwards are stable". Really? A span of three days without the Sun's gravity would kick the eccentricities of the planets up. Particularly the inner ones. Which would break any resonances previously in place. $\endgroup$
    – Urhixidur
    Oct 16, 2014 at 17:05

I'll give a try, but screw physics, I'm using Geology to look for it.

The heliosphere (or heliomagneticsphere, both terms hated by spell check apparently) is the suns magnetic field as our solar system travels through the galaxy. Ions travelling around 99% the speed of light or faster dominate this interstellar space (space between stars). This heliosphere deflects the majority of the particles coming at us, some possessing energy with an upper limit of 5J (which is an exceedingly silly amount of energy on an atomic level, being hit by 30 of these atoms is the same force most of us exert when we jump as high as we can) .

I would have to venture that the removal of the sun for 3 days would allow these particles free access to earth...at this speed and with this energy, the effects to life on Earth would be beyond catastrophic. Quite literally Ragnarok would only need to be the sun being devoured as the resulting impact from interstellar solar winds would destroy our atmosphere, almost all life on earth, and quite likely scar the planet.

Proof of Ragnarok should be discoverable in our geological record or ice cores as a massive earth altering event.

  • $\begingroup$ Darn it, I was going to say ice cores! $\endgroup$
    – HDE 226868
    Nov 26, 2014 at 23:46
  • $\begingroup$ @HDE226868 My second thought that should be detectable in icecores was the new daughter sun might not be born in the same phase as it's now eaten parent star was in. A drastic shift in solar activity could also represent this Ragnarok process. I should go back to the 'how to destroy humanity' question and put "eat the sun - ragnarok answer" $\endgroup$
    – Twelfth
    Nov 26, 2014 at 23:49
  • $\begingroup$ I had had the same thought about the daughter sun, but ArmanX said that the daughter was identical to the parent, so I threw that one out. $\endgroup$
    – HDE 226868
    Nov 26, 2014 at 23:50

Yes, but you'd have to get lucky.

If you want to use celestial bodies, you're best bet would be to study the effects of something that closely interacts with the Sun. Really, this rules out much of the solar system. Even Mercury, the closest planet to the Sun, is 46 million kilometers away from the Sun - at its closest approach! The difficulty here is that almost all the bodies in the solar system have orbits with small eccentricities, and are pretty far from the Sun. Fortunately, there are exceptions.

Comets have fairly eccentric orbits, so they're an interesting choice. They can closely interact with a body and then zoom off somewhere else, and we can study the effects that other body had on them based on orbital perturbations. For this, we can look at sungrazing comets. I think these are the coolest bodies in the solar system, partly because of their crazy orbits but also because "sungrazing" has a nice ring to it.

Sungrazing comets swing out from the far reaches of the solar system, coming in extremely close to the Sun - sometimes only a few thousand kilometers away! Think about it - that's one one-thousandth the distance between Mercury and the Sun! How does this help us? Well, think about what happens to these comets when they pass the Sun:

  • They may undergo orbital perturbations
  • They develop a long tail and related features (although this happens with all comets, this can be fairly prominent on sungrazers)

If the Sun disappeared for three days while a sungrazing comet (let's say a Kreutz sungrazer, because these ones come really close) was near the Sun, the comet wouldn't interact with the Sun. It would continue on its merry way in space. Our best shot at figuring out that the Sun wasn't there for three days would be to trace back the orbits of these comets using a simulator. It would be very hard to accurately model the orbits, but if the comet went straight through the location the Sun was supposed to be in, was otherwise not perturbed, we would know that something odd had happened.


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