How to create temperature gradient E-W rather than N-S?

[Triplicate]

A few days ago, I had a dream, the only part of which I can remember is a map.

The projection didn't make sense. It was rectangular, and latitude and longitude lines were all straight. However, features in polar regions weren't distorted.

I believe it was a sword and planet setting. The terrrain resembled Mars, with a mix of fluid-created landforms and craters. Some surface water, though not nearly as much as Earth or indeed most terraformed Mars concepts.

Most of the eastern hemisphere was one country. I know this was the "good" of at least "neutral" country, the default origin of the heroes for a story on this planet. The western hemisphere had many smaller countries. These would be the "exotic" foreign settings for the heroes to travel to.

I don't remember how I could tell climate from the map (as I recall, countries were color-coded, leaving no room for naturalistic colors), but the predominant temperature gradient was east-west, not north-south. The eastern hemisphere was overall much colder than the west. I recall that I liked this climate division: arctic-like climate wasn't something "other", it was the default/reference point.

Is it possible to build a world like this?

Tidal lock to the star is too extreme. I want both hemispheres to be inhabitable by humans. Also, there must be day and night everywhere.

I remember a concept from an astronomy book I have. A brown dwarf could plausibly have a moon?planet? as large as Earth, and it would probably be tidally locked. The near side would be warmer.

Not good enough; there's still a perpetual night side.

Try a star/brown dwarf binary with the world in question orbiting the brown dwarf. Now the far side gets light, with a "day" length determined by its orbit about the brown dwarf. This could be rather short. The Galilean moons have periods from 1.77 to 16.7 days, and a moon(?) close to the much more massive brown dwarf would orbit faster.

I suppose the question is whether I can construct a combination of star mass, binary separation, brown dwarf mass, and orbital distance suitable to create the climate I want. And then there's the question of exactly how hot and cold I want the "west pole" and "east pole" to be.

[jbgibson]

Do you care if the world as mapped is all there is? You could get the straight lat/Lon on the inside of a ring world, only a reasonable e-w would be manymany times the n-s dimension. If e doesnt have to wrap back around to w then most of your ring could be off-map with any number of reasons for warmer/cooler zones.Unless it was a habitat rather than a 50-80 million mile ribbon... A cylinder with the star outside can be a more reasonable 2:1-ish proportion. Say the habitat was different reflectivities on one side than the other for more or less heat coming up from beneath.

[atpollard]

A world with a 90 degree inclination would have some interesting day/night/season patterns.

[ManOfSteel]

Elevation and latitude would be some key points to consider. For instance, the many countries of the western hemisphere are mainly near the equator and nowhere on any of them are there mountains higher than 5,000 feet. The land is low and the terrain is dark, which absorbs and retains heat. There is a huge mountain range that runs north/south along the westernmost coast which creates a massive rain shadow so that everything to the east of it is desert. There's little land north or south of the tropics (if the world is tilted at all on its axis). The many countries have convoluted coastlines, providing lots of inlets and bays that can provide hot, humid, swampy environments. Main rivers skirt the interior of the continents further contributing to their vast inland deserts.

The eastern hemisphere is made of two large land masses, each one located at the poles and extending maybe thirty degrees from the north pole and the same from the south pole. The areas of both land masses that are closest to the equator feature the tallest mountains in the world, in fact most or all of the land that is not in the arctic regions is well above 14,000 to 20,000 feet above sea level. At this altitude, the snow never melts, not even in the summer, and often the only land that can be cultivated is on high plateaus where the inhabitants can often look down on the clouds. There is no warm current like the gulf stream, therefore the warmest areas (those at 60 degrees north and 60 degrees south) have a climate which, at its best, would be much like the mountains, (not the populated lowland coasts) of Scandinavia.

[Triplicate]

Do you care if the world as mapped is all there is? You could get the straight lat/Lon on the inside of a ring world, only a reasonable e-w would be manymany times the n-s dimension.

I recall trying hard to determine whether this map was the entire world. At first, I couldn't tell the scale, because many things about terrain are fractal. But the climate variation suggested a large-scale map. And, in retrospect, the size of mountain ranges. It's entirely possible the polar regions were truncated, as on many Mercator maps.
An artificial world doesn't fit the setting/style I had in mind.

A world with a 90 degree inclination would have some interesting day/night/season patterns.

I've never spent a lot of time thinking about this, but...
As I see it, a world with a high inclination would indeed have extreme seasons. However, it would still have one pole toward the sun at one time and the other at another time. I don't see why it would have a large difference from one hemisphere to another.

Elevation and latitude would be some key points to consider. For instance, the many countries of the western hemisphere are mainly near the equator and nowhere on any of them are there mountains higher than 5,000 feet. .... There's little land north or south of the tropics

Problem with those ideas: This world was something like 90% land. The specific feature I'm trying to replicate is the east being much colder than the west at the same latitude.
I hadn't really thought about using altitude to change climate.

[atpollard]

The specific feature I'm trying to replicate is the east being much colder than the west at the same latitude.

I don’t think that this is possible without approaching tidal lock. If the world rotates on a North-South axis in anything approaching 24 hours, the East and West will alternate day/night too rapidly to have a significant difference in temperature … the atmosphere will conduct heat and moderate the temperatures in horizontal bands.

A very slow rotation – like a 700 hour day – will allow the east or west hemisphere to experience a one week, all daylight summer, a one week slow sunset fall, a one week, all night winter and a one week slow sunrise spring.

With respect to the 90 degree inclination, the world rotates on a polar east-west axis (with north-south being defined by the celestial plane of the sun and planets). Assuming 24 hour rotation day and 365 day revolution year … The East polar hemisphere will experience 3 months of Tropical/Desert no sunset Summer, followed by 3 months of temperate sunrise-sunset fall, followed by 3 months of Arctic darkness Winter, followed by 3 months of temperate sunrise-sunset spring. During the Spring and Fall, the East and West Hemispheres will diverge towards opposite seasons as your map indicates (without the eternal day/night of tidal lock).

To heat only one side of a rotating sphere involves a minor heat source orbiting in a nearly geo-stationary orbit … a micro-sun orbiting over the east hemisphere. The micro-sun would need to advance slowly around the globe to move the ‘seasons’ east-west, otherwise one hemisphere gets perpetual summer and the other perpetual winter. I think that this starts to move from sci-fi into fantasy (not a criticism, just an observation) ... but Ptolemy would approve.

[ManOfSteel]

90% land, huh? That would be interesting. The planet then would lack the moderating influence that oceans and ocean currents have on land masses. The air would be much drier. In fact, the whole planet would be a near desert. River systems would be dramatically decreased. Yet you could still do a lot towards reaching your goal if you kept altitude in mind. In fact, you could make a fair amount of the western hemisphere below sea level, preferably inland areas to protect it from flooding from the small seas and lakes. The eastern hemisphere would be very high above sea level. Think of the Andes in Ecuador and Peru. Even at the equator, they're frozen. The summit of Mt. Kilimanjaro come to mind too.

[amberroberts09]

A few days ago, I had a dream, the only part of which I can remember is a map.

The projection didn't make sense. It was rectangular, and latitude and longitude lines were all straight. However, features in polar regions weren't distorted.

I believe it was a sword and planet setting. The terrrain resembled Mars, with a mix of fluid-created landforms and craters. Some surface water, though not nearly as much as Earth or indeed most terraformed Mars concepts.

Most of the eastern hemisphere was one country. I know this was the "good" of at least "neutral" country, the default origin of the heroes for a story on this planet. The western hemisphere had many smaller countries. These would be the "exotic" foreign settings for the heroes to travel to.

I don't remember how I could tell climate from the map (as I recall, countries were color-coded, leaving no room for naturalistic colors), but the predominant temperature gradient was east-west, not north-south. The eastern hemisphere was overall much colder than the west. I recall that I liked this climate division: arctic-like climate wasn't something "other", it was the default/reference point.

Is it possible to build a world like this?

Tidal lock to the star is too extreme. I want both hemispheres to be inhabitable by humans. Also, there must be day and night everywhere.

I remember a concept from an astronomy book I have. A brown dwarf could plausibly have a moon?planet? as large as Earth, and it would probably be tidally locked. The near side would be warmer.

Not good enough; there's still a perpetual night side.

Try a star/brown dwarf binary with the world in question orbiting the brown dwarf. Now the far side gets light, with a "day" length determined by its orbit about the brown dwarf. This could be rather short. The Galilean moons have periods from 1.77 to 16.7 days, and a moon(?) close to the much more massive brown dwarf would orbit faster.

I suppose the question is whether I can construct a combination of star mass, binary separation, brown dwarf mass, and orbital distance suitable to create the climate I want. And then there's the question of exactly how hot and cold I want the "west pole" and "east pole" to be.

So are you making the map do you start making it...

[atpollard]

I stand corrected.
A DRAMATIC difference in altitude between hemispheres could influence the apparent season. The thinner crust on the hot/low hemisphere might increase geothermal warming in that area, increasing the temperature difference.

[Triplicate]

To heat only one side of a rotating sphere involves a minor heat source orbiting in a nearly geo-stationary orbit … a micro-sun orbiting over the east hemisphere. The micro-sun would need to advance slowly around the globe to move the ‘seasons’ east-west, otherwise one hemisphere gets perpetual summer and the other perpetual winter.

Which is basically what I had in mind with the brown dwarf/star combination. The whole point is to have one hemisphere in perpetual "summer" and the other in "winter".

At first, I was thinking this might be a fairly common type of planet in the galaxy. Hoping there might even be a known star system with suitable parameters, I found this instead:
https://en.wikipedia.org/wiki/Brown-dwarf_desert
Brown dwarfs are rare in close orbits around stars. The exceptions are where the star is a red dwarf.
That is, systems where the same planet could receive significant heating from both are unlikely.