Survivable geological events that can enable sudden viewing of a planet

[magnemoe]

3 minutes ago, Ultimate Steve said:

That was my lead idea, actually, I'm glad I'm not the only one who finds it reasonable!

For maximum effect don't have some fly into it, have them climb above the clouds seeing the planet in full.
The inside should be significantly lighter during the night because of planetshine but this could be explained with sunlight reflected from high level clouds over the sea. 
High attitude planes made that explanation impossible as they showed how the atmosphere thinned out as attitude increased so it should be no air so high it could reflect light at middle of night. 

[Terwin]

How about something ecological.

What is the plants of one world with a lot of humidity managed to win the 'height' war by using methane as a lifting gas such that there was persistent 'green-cover' over most of the planet at any given point in time?

('Bigger' plants would float higher due to surface/volume ratio, until they got too high to get enough water, at which point they would dry out, crack, and fall to the surface)

There may have been frustrating hints and tidbits from occasional gaps in the coverage, but nothing certain until (large volcanic eruption/damaging solar storm/other large scale event damages a large swath of plants  leaving a gap that happens to be well-placed to allow both sides to see each other)

(herbivores could either fly or eat fallen plant-matter with carnivores feeding on herbivores, etc)

 

[p1t1o]

Ok here's a hypothetical.

 

Is this at all possible?

 

1 planet has a moon.

Moons orbit is synchronised with the orbit of the 2nd planet, keeping it perfectly eclipsed all of the time.

This is not stable due to n-body considerations.

But perhaps it could be stable for civilisationally-significant periods of time?

It would only have to be in place between the invention of telescopes until the day you want the big reveal, maybe 500-1000 years?

 

Eventually this orbital arrangement will slowly fall out of synch, and at some point, somebody will notice that there is a planet up there! And soon after, civilisation.

Perhaps the planet is remembered or mytholigised from ancient/pre-history (the last time it was uneclipsed).

[kerbiloid]

1 hour ago, Terwin said:

What is the plants of one world with a lot of humidity managed to win the 'height'

https://en.wikipedia.org/wiki/Hothouse_(novel)