8 Suns for 9 days, for one day is spent with none

[vicky_molokh]

Greetings, all!

I'm slowly making up stuff for a fantasy settings, and one of the ideas I had that over the course the 9-day week, each day the world has a different sun rise and set. (The world is flat-ish if it matters.) And one of the ideas was that one of the days doesn't have a sun, i.e. that there is no visible daytime on that weekday. I'm guessing plants would need to compensate with somewhat higher efficiency and storage. But what other consequences I might be missing from such a setup?

If it matters, the other suns provide sufficient light, and are each linked to an elemental/environmental theme:

• Green Plains - Yellow Gentle Sun;
• Frozen Wastes - Pale Cold Sun;
• Mountains - Grey Iron Sun;
• Sea - Blue Rainbringing Sun;
• Jungle - Cyan Windbringing Sun;
• Misty Swamps - Violet Clouded Sun;
• Woodlands - Green Blooming Sun;
• Deserts - Red Scorching Sun;
• Darklands - no sun.

Thanks in advance!

[Anthony]

Well, unless the darksun produces heat it's going to get pretty cold -- 36 hours of darkness will produce up to around three times the temperature drop of 12 hours of darkness (details will depend on the environment; humid areas will generally have less temperature drop).

You could just alter the cycle to allow for that, of course. I might be tempted by:

• Frozen Wastes - Pale Cold Sun;
• Mountains - Grey Iron Sun;
• Sea - Blue Rainbringing Sun;
• Misty Swamps - Violet Clouded Sun;
• Green Plains - Yellow Gentle Sun;
• Woodlands - Green Blooming Sun;
• Jungle - Cyan Windbringing Sun;
• Deserts - Red Scorching Sun;
• Darklands - no sun.

[ericthered]

The Dark-day will very important for smugglers and armies. A smuggler who needs to run a blockade will have an extra advantage on that day. Just about anyone who wants things done secretly will appreciate a full 36 hours.

[Flyndaran]

Originally Posted by Anthony

Well, unless the darksun produces heat it's going to get pretty cold -- 36 hours of darkness will produce up to around three times the temperature drop of 12 hours of darkness (details will depend on the environment; humid areas will generally have less temperature drop).
...

Is it really that linear? I've been burned before assuming anything involving astronomy is that straightforward.

And I assume you mean absolute humidity rather than the relative that dictates the percentage we get in a weather report.

[Flyndaran]

Originally Posted by ericthered

The Dark-day will very important for smugglers and armies. A smuggler who needs to run a blockade will have an extra advantage on that day. Just about anyone who wants things done secretly will appreciate a full 36 hours.

Nocturnal predators would use it as a big hunt day.
I imagine poor herders hate that long dark.
Lots more animals would need to have at least some form of deep sleep, torpor, and/or minimal stores.

[Anthony]

Originally Posted by Flyndaran

Is it really that linear?

There's a reason I said 'up to 3'. It will often be less, but it's still going to be substantially more than the normal diurnal variation.

[Peter Knutsen]

Originally Posted by vicky_molokh

I'm guessing plants would need to compensate with somewhat higher efficiency and storage.

Not really. Unlike mobile lifeforms, plants almost don't have a "rest metabolism". You need at least close to a million calories per day just to stay alive, even if confined to a bed (only half as much as you'd need if you were out and about). Much of that is due to your large energy-hungry brain, but you also have a lot of muscles that must be kept alive even when they're inactive. Even hibernating mammals burn a lot of energy.

Plants don't have that. No or at least very few and tiny muscles, etc. That enables them to live even in very unfavourable enviroments where they grow very, very slowly. The only problem is if they get out-competed (literally over-shadowered, thus starved of sunlight) by other plants that are better adapted to those enviroments.

But if the enviroment is equally sucky for all plants, meaning that none of the plants have evolved to be better at photosynthesis efficiency or energy storage (and I'm not very sure that the later is possible, although the former is), then it it makes no difference. They just all grow slower.

And with only 11% of days being sunless, there's not really any strong evolutionary pressure to adapt.

So that's really a non-issue, I'd say.

[Peter Knutsen]

Originally Posted by Flyndaran

And I assume you mean absolute humidity rather than the relative that dictates the percentage we get in a weather report.

It's not about air humidity at all, as far as I know.

Rather, bodies of water retain thermal energy much more efficiently than soil or stone, because the heat capacity of water is several times greater (1 kcal/kg vs something like 0.1 or 0.2 kcal/kg). That's why geographers talk about "coastal climate" vs "continental climate"

The other "humidity" issue is cloud cover. If there are clouds above, in the night, they slow the heat loss, in that they act as a blanket, keeping in most of the thermal energy (I'm imagining that they reflect the infrared light). During the day, clouds tend to work the opposite way, slowing the temperature rise or even negating it, as the sunlight can't get through the cloud cover to heat the soil and the water.

[Flyndaran]

Absolute humidity is how much water is in the air, and as you say, water holds heat far better than many other substances.
Cloud cover is all a part of overall albedo or how much "light" a surface reflects.

It is important to remember that deserts are defined by rainfall not whether there's boat loads of water in the air. Some parts of the Atacama don't get rain ever, yet because of offshore currents gets a regular dense fog. They really are developing methods of "moisture farming" vaguely like something a certain whiny Starwalker may work on.

[ericthered]

Originally Posted by Peter Knutsen

It's not about air humidity at all, as far as I know.

Rather, bodies of water retain thermal energy much more efficiently than soil or stone, because the heat capacity of water is several times greater (1 kcal/kg vs something like 0.1 or 0.2 kcal/kg). That's why geographers talk about "coastal climate" vs "continental climate"

The relative air humidity does play into it though-- its a direct result of the interaction between the body of water and the air, and how arid the region is is also a good barometer of how wildly the temperature will swing.

Of course, the lower the humidity in the air, the less the absolute temperature actually matters, and you have a weird interaction between actual temperature vs rate of heat loss.