I’m working on a story about a world where there is no axial tilt to the planet. It also has two moons, one like ours, another so close that it can only be seen from the southern hemisphere (much like Phobos on Mars, I believe–there’s also an atronomical term for this but damn me if I can remember it.) As a side note, it also rotates opposite Earth.
At any rate–I was wondering what the world would be like with no tilt. Obviously, there would be no seasons, so the various degrees of latitude would correspond to perpetual seasons–i.e, constant summer near the center of the earth, constant winter near the poles. How would this effect weather patterns? Since sunlight would hit the planet at a constant rate, would storms be predictable? Would they come though in a consistent pattern? What other issues would this create?
Atronomical?
Astronomical, I meant.
If there was no axial tilt there would be much less difference in temperature as you travelled north or south. The days would be the same length everywhere, but near the poles the sun would remain near the horizon most of the time and at the poles it would never get dark, the sun would circle the horizon over the course of a day.
I don’t see how that is possible. There’s no orbit that keeps it above the southern hemisphere permanently, because the plane of the orbit must pass through the center of the planet. Either it’s above the equator all the time, or it spends some time above the northern hemisphere and some time above the south.
I’m also skeptical that with such an enormous moon like ours, the orbit of the second smaller moon would be stable.
I have no idea about climate changes, sorry. But if the orbit of the planet was not perfectly circular, there may be a seasonal change after all caused by the changing distance from the sun.
I’m wondering if life could (so easily) develop on such a planet; tidal slosh would still be present, but seasonal temperature variation etc may also have been a factor here on earth.
Certainly organisms might well be quite different as a result of not needing to adapt to changing seasons.
My guess is that weather patterns would still be chaotic.
I mean chaotic in the mathematical sense - small changes to input parameters would result in large changes over time, but within a certain the range of possible states (weather extremes).
You would still have Hadley cells , still have air currents due to differential surface heating, and changes in air temps due to changing ocean surface temps. So there would still be weather systems like fronts. There is even feedback in the system - cloud cover affects surface heating, which affects many other things, including cloud cover.
I don’t think that weather systems would not be much more predictable than Earth’s, either. Seasonal change is relatively long term and doesn’t seem to be an important factor in how smaller systems move.
Storm strength: A major factor in storms is the mixing of air masses with different temperatures, like arctic air moving into tropical air. And a major mover of air masses are the jet streams. I think your world would still have jet streams so you would still get fronts and associated storms.
You could still get hurricanes - they don’t result from mixing of two different air masses.
BUT, don’t let that stop you if it’s important for your story. Just say that the fundamental factors that govern the development of weather patterns have a lot of negative feedback. That would dampen out the big variations and give you a smaller range of ‘extreme’ variations. For instance: sunny -> cloudy -> light to moderate showers -> sunny again. On a cycle that varied from 3 to 4 days.
Oh yeah, and trees would be different.
And animals would evolve to be very sensitive to temperature variation. Well, maybe not. Some animals might have to travel to find mates, follow prey, greener pastures, etc. They could experience a range of temps that way. But there might prefer to travel more east-west than north-south.
And if human tribes travelled mostly east-west you could have less interaction between tribes, possibly leading to developing into different species.
Nt = no text
You can’t have the moon only visible from the southern hemisphere. But I’m thinking if you put in in a polar orbit with a period slightly shorter than day (by 1/Y where Y is the year in days) you may be able to have it only visible from the eastern or western hemisphere. That would be even weirder, no?
My guess is that weather patterns would still be chaotic.
I mean chaotic in the mathematical sense - small changes to input parameters would result in large changes over time, but within a certain the range of possible states (weather extremes).
You would still have Hadley cells , still have air currents due to differential surface heating, and changes in air temps due to changing ocean surface temps. So there would still be weather systems like fronts. There is even feedback in the system - cloud cover affects surface heating, which affects many other things, including cloud cover.
I’m guessing that the systems would not be much more predictable than Earth’s. Seasonal change is relatively long term and doesn’t seem to be an important factor in how fronts move.
Storm strength: A major factor in storms is the mixing of air masses with different temperatures, like arctic air moving into tropical air. And a major mover of air masses are the jet streams. I think your world would still have jet streams and you would still get fronts and associated storms.
You could still get hurricanes - they don’t result from mixing of two different air masses.
BUT, don’t let that stop you if it’s important for your story. Just say that the fundamental factors that govern the development of weather patterns have a lot of negative feedback. That would dampen out the big variations and give you a smaller range of ‘extreme’ variations. For instance: sunny -> cloudy -> light to moderate showers -> sunny again. On a cycle that varied from 3 to 4 days.
Oh yeah, and trees would be different.
And animals would evolve to be very sensitive to temperature variation. Well, maybe not. Some animals might have to travel to find mates, follow prey, greener pastures, etc. They could experience a range of temps that way. But there might prefer to travel more east-west than north-south.
And if human tribes travelled mostly east-west you could have less interaction between tribes, possibly leading to developing into different species.
Most importantly, your favorite fruits and vegetables would never be out of season.
This is fairly obvious… but with no tilt the day would be exactly 12 hrs. long and night would be exactly 12 hrs. long. everywhere but the poles. At the Earth’s distance and orbital shape, there would be a problem of baking the equator as the sun would be directly overhead and freezing the poles as they would “never” get sunlight a degree or two beyond the limb (only slightly above the horizon due to atmospheric effects). This would mean that the temperature variation would, barring perturbative damping in the atmosphere, be greater than on earth. Of course, the dominant local weather pattern is only generally determined by the climatic temperature variation, and so given a more chaotic climate (as described above) you might more of a contribution of atmospheric damping and therefore temperature variations might not be as varied as I posit.
Even though it doesn’t exactly answer your question, a good place to check is the book What if the Moon Didn’t Exist?, by Neil F. Comins. He looks at a number of scenarios. One of the chapters is titled “What if the Earth Were Tilted Like Uranus?” and in it he talks about some of the issues you’re concerned with, although from a different angle, literally.