[Space] Adapting to long days and other implications of a generated system

[vicky_molokh]

Actually, why not give locals Low-Pressure Lungs. Instant solution.

[Diomedes]

Originally Posted by David Johnston2

It doesn't help that 80% hydrosphere means their sea level is comparitively high.

Actually, if the two planets are tidally locked, each planet will have a permanent tidal bulge facing its twin, and another on the far side, with relatively shallow seas in between.

[StevenH]

Originally Posted by Indigar

Hey all!

Since the apparent diameter of these planets from their companions' surface is about 10x the diameter of the moon, they're about 5 arcseconds wide. I believe that makes such an eclipse 5"/360 deg* 98hrs (day length) = about 15 minutes. This doesn't fit with your figure of 10 hours; have I miscalculated?
If I'm correct, these daily eclipses are not going to have a significant effect on day/night rythms, so we're back to a difficult-to-adapt-to 48 hrs each of day and (quite bright) night.

My number was a WAG based on feel more than actual mathematics. :-) But, as it turns out, I had forgotten that these two worlds are spinning around each other 7 times faster than the Earth/Moon system. So I was even more wrong than I had thought.

15 minutes is probably correct. A lunar eclipse can last up to 107 minutes, and when you divide that by 7 you end up with...15 minutes. (Kind of too bad, really, I kind of liked the "long night/short night" concept, but obviously it's just too wrong to work :-)

[Agemegos]

Originally Posted by Indigar

Also, how hard would it be for normal humans to adapt to the 98-hour (four-DAY) days on such a world? Humans would have arrived on this world from Earth in a Banestormish way about 2000 years ago.
How well would humans arriving from modern Earth be able to adapt?

Well, they'd need a siesta in the day and a waking period in the night. Or they can arrange a cycle with four sleeps per day. That's not a problem.

You have a bigger problem with daily temperature variation. The days will warm up more, and the nights cool down more. This will be uncomfortable to animal, dangerous to plants, and will drive strong diurnal winds (onshore and anabatic during the day, offshore and catabatic during the night). On the other hand slow rotation means low Coriolis forces, so cyclonic winds will be weaker.

Speaking of plants, the long day-night cycle will challenge the physiology of plants from Earth. The light half and the dark half of their respiratory cycle are adapted to a twelve-hour duration. I don't know how much trouble this will be.

Summary: in his classic Habitable Planets for Man, Stephen Dole assumed that the upper limit on the daylength for habitability by Man was 96 hours, because of diurnal temperature variation killing plants.

Incidentally, don't forget that because each planet is tide-locked to the other, each is in synchronous orbit about the other. That means that, seen from each planet the other holds a fixed position in the sky. That means that it is visible (always in the same place) from one half, and is never visible from the other.

[Anaraxes]

The inhabitants of one side of the planet have a pantheon of wandering gods associated with the visible planets, while dismissing as ludricrous heathen myth rumors of the monotheistic religion of the antipodes between the pair, with their one all-powerful god with a few attendants.

[Lord Carnifex]

I dimly recall a psych study involving locking a test subject in a habitat that lacked clocks or other discrete time measures. The subject was encouraged to follow whatever cycle was comfortable, with the aim of extending it if possible. I believe that they found subjects could adapt in time to a 32-hour awake, 16-hour asleep cycle.

In this situation, it sounds like the secondary is going to be a significant source of light, anyway. So probably the inhabitants of the system will develop thick window shades and a complex mechanism for charting time based on the movements of the primary, the secondary, and their eclipses by the partner. Day and night cycles may either become relatively meaningless or a source of religious ritual and mystic belief.

I don't imagine, even with a high partial pressure of O2 that the companion planet is going to be comfortable for long-term human habitation without significant magical or technological help. But I'm not sure that this is a bad thing. Maybe the companion is the home of the sorcerous elite, ruling over the lesser mundanes. Or maybe the companion is a place rarely or never visited, a location of myth and wonder. Ever since the Great Exodus, no one has gone there and lived to tell about it...

[Agemegos]

Originally Posted by Diomedes

Actually, if the two planets are tidally locked, each planet will have a permanent tidal bulge facing its twin, and another on the far side, with relatively shallow seas in between.

Nope. The water in the oceans will conform to the tidal bulge for the same reason the bulk of the planet does. You do recall that sea water is affected by the tides, don't you?

So the planets will be somewhat prolate (elongated) with their axes pointing at each other. But the pattern of land and water will be spread out all over their surfaces.

[Diomedes]

Originally Posted by Agemegos

Nope. The water in the oceans will conform to the tidal bulge for the same reason the bulk of the planet does. You do recall that sea water is affected by the tides, don't you?

So the planets will be somewhat prolate (elongated) with their axes pointing at each other. But the pattern of land and water will be spread out all over their surfaces.

That's what I meant; the oceans inline with the other planet will be at a permanent high tide. Any oceans on the orthogonal meridians will be shallower. And since the planets are larger and nearer to each other than the moon, they'll be very large tidal forces.

[Bruno]

Originally Posted by Agemegos

So the planets will be somewhat prolate (elongated) with their axes pointing at each other. But the pattern of land and water will be spread out all over their surfaces.

The water will deform more and faster than the planets main mass will, so it's still going to be deeper on the side of the planet facing the partner, shallower on the sides, and then deeper again (but not as deep) on the far side of the planet.

[thtraveller]

Originally Posted by Bruno

The water will deform more and faster than the planets main mass will, so it's still going to be deeper on the side of the planet facing the partner, shallower on the sides, and then deeper again (but not as deep) on the far side of the planet.

Relatively speaking. The depth is more to do with underlying geography - where the mountain ranges and the trenches are.