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Pallas is a large planet full of vast oceans and islands. Humans have terraformed the planet so the soil and water are fine. The issue I am running into is growing food (there is no livestock, this is a world without meat) with a slow rotation (75 days (24 hour periods) of "day" (as in the sun is up) followed by 75 days (24 hour periods) of "night" (as in darkness/ the sun is no out)). It is orbiting around a red dwarf sun. I've worked through every other aspect (how they'll stay warm/ the climate differences between night and day, Earth and Pallas, et cetera). I just need to know what crops could grow/ how I can feed the humans living on this planet.

So how can I feed the people on a planet with a slow rotation?

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If this planet, much like Earth, rotates at an angle (the axis of the rotation is not perpendicular to the plane of its orbit around the sun), then there will be differences in daylight length at different places.

Thus, while at the equator it will always be a 75/75 cycle, as you get closer to the poles the numbers will greatly differ, with seasons of extended daylight followed by times with more darkness. Much like seasonal sunrise/sunset times on earth, with the extremes of polar night and midnight sun.

This depends highly on the time it takes for the planet to rotate around the star (on Earth that is 365 days, a year).

So, given a long enough year, you can grow food in the Northern Hemisphere during the 'Summer' and then eat food from the South during the 'Winter'.

illustration

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  • $\begingroup$ This doesn't make a lot of sense as I'm reading it? Summer and winter are a lot less important than day and night, when the full day from midnight to midnight is 3600 hours, or ~1800 hours of daylight and ~1800 hours of night. It won't matter what time of year it is once the sun sets. North or south hemisphere it's going to be dark and cold. $\endgroup$ – AndyD273 Sep 25 '17 at 21:21
  • $\begingroup$ On a side note, for a larger red dwarf like Lacaille 8760, the habitable zone is ~0.3 AU, which is inside of the orbit of Mercury. Mercury has a year that is 88 Earth days long. Being on a closer orbit this planet may have a year that is only slightly longer than it's day, meaning that even if you set up farms on the poles you might not get much more growing time. $\endgroup$ – AndyD273 Sep 25 '17 at 21:29
  • $\begingroup$ @AndyD273, on Earth, a day is 24 hours. And in the equator, this means 12 hours of daylight and 12 hours of night. But, if you live at, say, Stockholm, you'll notice that at winter the sun sets at 15:00, and at 23:00 in the summer (you still have 12 hours on average). The opposite is true for Melbourne. On this planet a 'day' is 150 'Earth days', so in Stockholm it'll be 120 days during the summer (and opposite in Melbourne). A 'year' is a rotation around the star, if its 150 Earth days - days in one Hemisphere will always be longer. If it's 100 - you will have an irregular pattern, and so on $\endgroup$ – Laetus Sep 25 '17 at 21:45
  • $\begingroup$ I'm pretty sad I can't give points for "coolest thing I learned in this thread." $\endgroup$ – A.G. Weyland Sep 26 '17 at 0:53
  • $\begingroup$ @Laetus Sure the days will be longer during the summer, which will definitely stretch out the growing season, possibly long enough to plant crops with longer growth times outdoors, but you won't be farming the south during the northern winter if it's night time, even if the night is relatively shorter. This planets day will probably be a lot longer than its year, since it will likely have a shorter year than Mercury if it is inside the habitable zone. $\endgroup$ – AndyD273 Sep 26 '17 at 14:28
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Most normal field crops take longer than 75 days to mature.

The USDA has a handbook with usual planting and harvesting times(pdf).

These might be different on a planet with such a long day, but more likely you'd have to do selective breeding or genetic modification to make them mature faster for planting in fields; Plant at first light, harvest before dark. It might be doable.

But for the best option, Greenhouse setups would be the most practical.
There are farms set up in old night clubs in New Jersey that use LEDs to grow fresh produce for stores year round locally, instead of having to ship them in from far away. They grow them hydroponically on racks so that you get a lot of plant density, and because you control the whole process you don't really have to spray for bugs, so you can cut out pesticides and make organic farming a lot easier/cheaper.

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  • $\begingroup$ After much consideration, I think greenhouses are the best route, for sure. $\endgroup$ – A.G. Weyland Sep 26 '17 at 0:52
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Quinoa and Amaranth are South American grains that both yield crops in a matter of weeks in friendly, to them, climates. A lot of other species are going to need greenhouses and artificial light to extend the growing season and also because of the spectrum shift from Sol to a Red Dwarf. The biggest issue is really going to be the relentlessly daylight, you've going to have to have a very serious breeding/engineering program to get a plant that handles having no day/night cycle.

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Yeah in that case indoor is probably the most feasible option supposing you can supply sufficient energy and water to support it. If you want something flavorful that would take a bit more math though, it could be feasible to have massive mobile greenhouse arrays that travel across the planet just quickly enough to always be in the daylight zone.

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Interior hydroponic grow ops with full spectrum lighting will work anywhere regardless of external light conditions.

If that isn't your style greenhouses will provide a warm environment for anything with a 75 day or less growing season.

They'll probably be enough twilight in your planet's 150 day day that the growing period can be extended beyond just the 75 days of full sunlight.

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