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173

A dragon with a full wingspan of 20000 km (folded to fit into a 10000 km resting area) and surface area of 44 million sqkm will have a terrible impact on the environment. Phase I In the first days of her awakening, as she shifts, freeing herself from the encumbrance of all the cities and forests and so forth that are littering her back, widespread but ...


91

Everyone on the Earth dies and the planet becomes a steaming molten mess circling the Sun. Eventually everything will calm down and life will restart. But why? Fill a bucket with water. Now remove 1 cup of water. The removal of the water causes a wave across the surface of the cup while the water redistributes to fill in the hole. The same basic thing ...


70

There are simply too many things on your plate Do you know how hard it is to make seasons change? How delicate the process is to make the souls ascend? You mispronounce one syllabe and grandpa ends in void. Like forever. And you want me to collect taxes? Write laws? Take care of the military? Meh. Nothing for me. And excuse me now. I need to meditate to ...


68

Yes Under the equivalence principle anything on the "back" of the planet that wasn't strapped down would be left behind if you accelerated at >1g. we ... assume the complete physical equivalence of a gravitational field and a corresponding acceleration of the reference system. — Einstein, 1907 That includes people, atmosphere, water, large chunks ...


60

Mount Kilimanjaro, despite being close to the Equator, has permanent glaciers on its top. This hints toward the solution to your problem: orography! While one hemisphere is mostly flat, with limited elevation and can enjoy the benefit of a warm climate, the other hemisphere is much more mountainous with most of its peaks above the snow line. The ...


55

It's physically possible. Put a spherical object in a geostationary orbit, make it rotate about its own axis at a rate suited to your own visibility/non-visibility requirements, and make a portion of it have very low albedo. Staying at a single point in the sky, the object will only be visible while the higher albedo portion is facing the planet and ...


53

If your tidally-locked planet captured a large moon, sort of like the one we have here on Earth, the tidal forces of the moon could be stronger than the tidal forces from the star. This would result in the planet gradually losing its tidal lock to the star in exchange for a tidal lock with the moon.


53

A planet in our very solar system has actually gone through such a shift! Venus currently has a 243-day long retrograde spin, but likely didn't always. The current theory says it started with the usual fast spin and underwent tidal locking normally. And it would have stopped there, but Venus's thick atmosphere generates thermally driven atmospheric tides ...


52

Binary star. If you have two sources of light, you will have 4 options for night and day: double star day, two single star days, and night. These will be predictable but for a complex orbit the ABday, Aday, B day, night pattern might take a very long time to repeat, and seem chaotic in the short to intermediate term. Additionally days will turn into ...


52

Gravity isn't going to let that happen I'm not the resident orbital mechanics specialist so I don't have specific figures in front of me but as I understand it, there's no way that two planets, both of Earth mass, are going to collide slowly. The reason for that is that they're going to be attracted to each other by gravity. Even if they could collide ...


51

As Raditz_35 points out in comments, mountains - even equatorial ones - are colder at higher altitudes. For instance, Mt. Kilimanjaro is only three degrees off the equator, but its summit is cold enough to host glaciers. But what you want isn't just one mountain, it's a whole ring of them, mostly along the equator. Enter Iapetus, the eighth moon of Saturn ...


48

Combine an significant axial tilt with a elliptical orbit. Axial tilt allows one hemisphere to be in winter while the other is in summer. Earth has approximately 23.44 degrees of tilt. Even in mid-summer the temperature at the south pole is far from tropical because the sun never rises above 23 degrees and sunlight is correspondingly dim. 45 degrees is too ...


46

Can anyone perform the rituals needed? Or do they need some set of magical abilities? If anyone can do it, then in being the one who does it has no true power. Just like we need farmers to produce our food, but everybody who is willing to learn the needed skills can do their job, so they can't take us all hostage. If you need to be born with some special ...


42

/Their lives are to be miserable./ I know a recipe for miserable. Flies everywhere. https://en.wikipedia.org/wiki/Black_fly The flies are a genetic modification attempt gone wrong. They are everywhere and they attack anything that moves, biting and chewing and drinking. They cause blindness and carry other diseases as well. Attempts to control them ...


42

It's very much a matter of what information they want to display in their primary 3d to 2d projection. The Mercator projection that everyone is so familiar with is simply designed so that lines of latitude are straight horizontal and any simple compass bearing is a straight line. This makes ocean navigation easier as the important factor was knowing how ...


41

I asked this same question, on the physics stack. The answer is that a body can have only one axis of rotation. Below pasted is the link to the question and the answer I picked. https://physics.stackexchange.com/questions/322200/how-many-different-axes-of-rotation-can-coexist Q: I have questions about rotation. There is a sphere in space. I can ...


41

Religion Some book considered holy and written long ago claims some deity created that specific planet, and then all sorts of creatures and finally humans on it. So the inhabitants of Eden think they have been expelled from the Garden of Earth, without ever realising that Earth is another planet.


39

Your desert glass pebbles are volcanic glass. In the US they are called Apache Tears. source These are unpolished, as found in the desert. When polished they are a very beautiful deep black and suitable for use in jewelry. Some of the round ones in this image ones look pretty close to that without polishing. https://en.wikipedia.org/wiki/Apache_tears ...


39

Bizarre real maps In our real world of the planet Earth, some traditional cultures created maps that for most people would look absolutely like alien objects and will not be recognized as being actually maps, still the are maps, and they are of practical use. Inuit wooden maps The Inuit people of Greenland used carved pieces of floatwood to depict the ...


38

This scenario is quite problematic for two main reasons: evaporation and peak wavelength. The black hole's lifetime is too short We can make a rough estimate of the properties of the Hawking radiation coming from the black hole. First, let's start with the luminosity. Since $L\propto M^{-2}$, where $L$ is luminosity and $M$ is the mass of the black hole, ...


38

why invade at all? Most structures of a civilisation are probably going to be on a surface. It is, after all, more difficult to build underground than on a surface. That means that most items of value can be simply blasted from above. But you might not want to blast them from orbit because these items might also be of value to you. You might want to avoid ...


37

What keeps my planet's water from irreversibly concentrating over time on the frigid wastes while the rest of the planet dries up? When ice piles up, it will exercise pressure. The closer to the terminator, the less the ice. As a consequence, pressure gradient will tend to push the ice sheet toward the terminator, where it will melt, returning water to the ...


36

You can do it with elevation. http://www.estarte.me/world-temperatures-map.html/world-temperatures-map-file-annual-average-temperature-jpg-wikimedia-commons Here is a map of average temperature on Earth. I have labeled the Andes and the Himalayas. They are high elevation areas and you can see they are substantially cooler than adjacent areas at the same ...


34

It doesn't seem to be possible using "normal" geology. You'd need a supervolcano to attain the required energies, and "piloting" one with the required precision doesn't look doable. You need to score a direct hit; getting in orbit isn't enough, since any station would have ACS thrusters and be able to both detect a coorbiting incoming missile, and avoid it. ...


34

I'm reminded strongly of Iapetus, a moon of Saturn that has a dramatic two-tone coloring. One hemisphere is quite light, while the other is dark. It almost looks like you dunked half of the moon in chocolate: Image credit: NASA/JPL-Caltech/Space Science Institute/Lunar and Planetary Institute. Public domain. Iapetus is tidally locked, meaning that one side ...


34

There are 3 types of natural glass: obsidian (volcanic glass), impactite (meteor glass), and fulgurite (lightning glass). Naturally round impactite is virtually unheard of. Impactite tends to have strong striations in the direction of impact that gives it more of a cleaved shape. It is also very rare for it to be transparent. Technically, a round ...


33

A black hole with a Schwarzschild radius of 4 feet would have a mass of 137.5 x Earth and the gravity to go along with it. Such a black hole would instantly liquefy the earth as it shreds it into an accretion disk and shoots gamma rays straight through the earth's poles. There would be approximately 0 seconds for a committee to consider the problem before ...


32

Time This is normally done with the application of a few hundred years, technological collapse and a migration of the population away from any physical artifacts of interplanetary travel. Technological collapse takes away all their records, even if they reinvent computers later they probably won't be able to read the old records. The technological collapse ...


31

It can only happen if the body has chaotic rotation: Chaotic rotation involves the irregular and unpredictable rotation of an astronomical body. Unlike Earth's rotation, a chaotic rotation may not have a fixed axis or period. Because of the conservation of angular momentum, chaotic rotation is not seen in objects that are spherically symmetric or well ...


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