52
votes
Accepted
Fantasy map that has minimal land at the equator. What does this mean for rainforests and the world as a whole?
Earth's rainforests are definitely not the lungs of world. Actually, they consume all (or most of) the oxygen they produce. The phytoplankton (seaweed and microscopical organisms) are the truly world'...
- 998
45
votes
Where would space habitats get their oxygen from?
According to this lovely image from NASA (article here), the source of onboard oxygen in current spacecraft is mainly water electrolysis. The hydrogen so produced is processed with carbon dioxide to ...
- 38.8k
37
votes
Accepted
A planet illuminated by a black hole?
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 ...
- 102k
36
votes
Keeping an "hot eyeball planet" wet
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 ...
- 301k
34
votes
Accepted
Extremely small planet to live on
Our known quantities are:
Radius of the body: 50 metres
Density of the body: same as Earth's, 5515 kilograms per cubic metre
This is enough to calculate the acceleration due to gravity on the ...
- 442
33
votes
Earth loses its sun as is sent hurtling through space in darkness. How do humans survive for the next 1,000 years?
If there is little or no warning, there is no chance of survival. However, with some preparation, it is feasible to survive deep underground - a few km would do.
The interior of the Earth is quite ...
- 16.4k
32
votes
What would cause plants to survive on the ground while restricting animals to the air?
Big Smelly Mangrove
Animals cannot come to the ground because there is no ground. Only an endless swamp with nothing to stand on.
The air is thick with CO2 from decomposition. It will not kill you ...
- 66.3k
28
votes
Accepted
What would the consequences be of a high number of solar systems being within close proximity to one another?
Your environment is quite similar to that in a globular cluster. At its densest, a globular cluster may see peak stellar number densities of $\sim1000$ stars per cubic parsec, which implies a mean ...
- 102k
27
votes
A Habitable Zone Within a Habitable Zone--Would that Make any Difference?
No habitable zones at all.
Consider a habitable zone. It receives enough radiation from its star (or star pair) such that water does not freeze or evaporate.
From OP "one habitable zone is deep ...
- 306k
26
votes
Accepted
Could a world with a extremely bright night sky exist?
If you don't want the light to come from a single source, presumably you need roughly uniform illumination across the night sky. One way to achieve that is with a reflection nebula, a cloud of dust ...
- 102k
24
votes
Is a solar system around a black hole possible?
Yes.
You can take binary or trinary star systems and swap one of the stars for a black hole and nothing changes in the orbital dynamics.
Depending on the layout of the solar system planets can orbit ...
- 77.3k
23
votes
Are Geologically Dead Planets Habitable?
I wouldn't expect long term habitability. A planet's magnetic field provides much of its shielding against stellar and cosmic radiation -- but the magnetic field is created by a "dynamo" action of ...
- 47.3k
23
votes
What would cause plants to survive on the ground while restricting animals to the air?
There is one type of animal that lives on the ground.
source
Your plants are myrmecophytes or the alien equivalent. The plant - insect alliance is so successful that all existing plants are allied ...
- 306k
22
votes
Keeping an "hot eyeball planet" wet
Librations. That is, the tidally locked planet is not in a perfectly circular orbit, and so the portion of the planet that is sun-facing is not constant. This is because the rate of rotation is (...
- 9,601
21
votes
Accepted
Where would space habitats get their oxygen from?
In both cases the shear volume of necessary oxygen (and other
elements used in human breathable air) would make it very
difficult or impossible to build such a habitat, no?
No, actually; I don't ...
- 809
20
votes
A planet illuminated by a black hole?
From Hawking radiation? No.
The Hawking radiation emitted is inversely proportional to the black hole's size. To make the black hole glow with enough light to be as bright as a star from Hawking ...
- 5,928
20
votes
Accepted
Why would Earth be long-term unsuitable for an advanced alien species that's already colonized it?
"It's the smell!"
-- Smith
I think the easiest answer is that there is something in Earth's biology that disagrees with them... something that can be "managed" with continuous medical intervention, ...
- 14.5k
19
votes
Accepted
How could you keep a rogue planet warm(ish)?
Rogue planets can be kept warm. The key points can be found in the Wikipedia entry on rogue planets.
Interstellar planets generate little heat nor are they heated by a star. In 1998, David J. ...
- 38.5k
19
votes
Accepted
What is the theoretical maximum number of habitable planets in one solar system?
This is based off the information found in the link provided by Juraj.
The answer is 2,862,106 earths in the goldilocks zone
How to get 2,862,106 earths in habitable orbits:
Rules, they have to all ...
- 34.9k
18
votes
Why would Earth be long-term unsuitable for an advanced alien species that's already colonized it?
The aliens are humans.
The aliens did do the calculations and they did find a habitable planet, 100,000 years ago. They are depleting their homeworld - here.
On arriving on Earth and settling ...
- 306k
17
votes
Extremely small planet to live on
First matter first: to have a body in a spherical shape, you need to exceed a certain radius, dictated by the material. Most likely with 50 meters you will have a potato shaped object.
Moreover, to ...
- 301k
17
votes
''Habitable'' planet close to a star
You're basically talking about Venus. Or, more accurately, Venus if it had started out with a lot less water and CO2. Less water and CO2 to start with mean you never get the runaway greenhouse effect ...
- 16.9k
17
votes
Accepted
Could bacteria survive on a star?
Some simple molecules can exist in stars - but not the right ones.
Contrary to popular belief, many different types of molecules can exist in stellar atmospheres, especially cool stars like red ...
- 102k
17
votes
Accepted
How do oceans in an O'Neill Cylinder replenish dissolved oxygen?
Centrifuges that separate blood spin at a high RPM simulating between 500 and 2000 times Earth gravity. So with your O'Neill Cylinders spinning at ~1G you will still have this problem (when it comes ...
- 105k
17
votes
A Habitable Zone Within a Habitable Zone--Would that Make any Difference?
The "Habitable zone" concept becomes "The collection of all habitable orbits"
The habitable zone is a simplification depicting 2 circles around a sun (or barycentre of N suns) ...
- 44.4k
17
votes
Accepted
Is a desert planet with a small habitable area possible?
How about a very deep rift valley?
The surface could have a thin atmosphere, and continuous illumination from a cloudless sky. It would be hot and dry in the day and freezing at night, and the air ...
- 12.6k
16
votes
Accepted
What kind of Gas Giant has a "safe zone" between the radiation from a star and the radiation from a gas giant planet?
First, it's important to discuss what radiation belts are and how they form. Radiation belts are formed by charged particles that are trapped by a planet's magnetic field and, due to the shape of that ...
- 38.8k
16
votes
Is a desert planet with a small habitable area possible?
Nile River
Have you seen a satellite photo of the Nile River? It is basically a small stretch of very green "forest", surrounded by very harsh deserts.
Your world could be very old, with ...
- 1,368
15
votes
Accepted
Is this atmospheric composition breathable, and what would it look like?
Nitrogen (N₂):
60.4% — 78.08% = −18.48% N₂ (↓22%)
Is used in the atmosphere to reduce the percentage of oxygen in the air (if O₂ is too much our atmosphere may burn out).
It haven't any very ...
- 8,905
15
votes
How could I scientifically explain a world where the surface is made out of pillars?
The closest feature we have on our planet that gets close to appear like this is the Giant's Causeway.
To obtain this you need to have magma intruding a rock, then cooling down to form the pillars, ...
- 301k
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