158
votes
Accepted
This sword is forged from meteorite iron - but how is that any good?
Kamacite and Taenite
Kamacite and Taenite are both Iron-Nickel alloys found (on Earth) only in meteorites. Kamacite's composition is in the 90:10 to 95:5 Fe:Ni range. Taenite's composition is from 20%...
- 85.8k
130
votes
Accepted
How could a planet have a sky without stars at night?
Dust cloud.
The star may be residing in a dust cloud with no other stars nearby. This interstellar dust will create a faint nighttime glow, and can be thick enough that no other star's light can be ...
- 42.3k
109
votes
Accepted
What could make a star green?
Give it a circumstellar cloud of oxygen.
Some planetary nebulae, such as NGC 6826, appear green because of ionized oxygen.
Image in the public domain. Yes, this is a true-color image.
I see no reason ...
- 102k
76
votes
Accepted
What's the largest body in the solar system that you could destroy without endangering humanity?
Ganymede
No matter which one you go for, blowing up a planet is going to make a lot of shrapnel. An asteroid of several miles long is an extinction-level event, and you've just thrown millions of ...
- 29.2k
71
votes
How could a planet have a sky without stars at night?
Perhaps their planet is on the inside of a giant Dyson sphere that was created by an ancient civilization.
This would be a vast solid shell that surrounds their entire solar system, the inside of ...
- 1,722
56
votes
How do you non-catastrophically reduce the mass of the Sun by half?
C. Must not create any phenomena that would have devastating consequences on life on the planets (i.e.: no radiation, excessive heat, energy surges) except for the diminishing of the Sun's current ...
- 142k
52
votes
How could a planet have a sky without stars at night?
One possibility is for the surface of the planet to be covered in highly luminous matter. Perhaps all the surface is an interconnected network of bioluminescent life.
There is no moon (assumed ...
- 41.2k
50
votes
Accepted
Could two planets follow the same orbit and never "see" each other?
I assumed, based on the limited knowledge I have on the subject, that all star systems have ellipsoidal orbits (the star being in one of the two focal points) just like our own
You are right, this is ...
- 301k
46
votes
Plausible reason for Earth not be able to get updates about terraforming on Mars?
Switch planets.
Venus has a permanent, thick, global layer of clouds that covers it. We cannot observe its surface from the Earth. Even satellites can only peek at its surface through radar. The only ...
- 142k
40
votes
Accepted
Why might a valued mineral be only found on one planet?
Organic
Your mineral could have been deposited millions of years ago by a specific type of organism, class of organisms, or type of biome. For instance, you might have a forest that produces lots of ...
- 2,837
39
votes
This sword is forged from meteorite iron - but how is that any good?
Don't make space iron better. Make all other iron worse.
Read up on Low Background Steel. Have all of earth's iron contaminated with something, and less useful than we think of iron being.
At some ...
- 3,120
39
votes
How do you non-catastrophically reduce the mass of the Sun by half?
Wormhole
[A,C,D,E,F,G] A traversalable wormhole would be an excellent mechanism to remove mass from the sun. A wormhole is consistent with general relativity while avoiding all of the pitfalls of ...
- 911
38
votes
How could a planet have a sky without stars at night?
It is never night.
https://www.tripsavvy.com/midnight-sun-in-scandinavia-1626397
Your people live on the north pole of a tidally locked planet. Like the countries near the north pole on our planet, ...
- 306k
36
votes
What could make a star green?
Phil Plait of the Bad Astronomy fame:
Why are there no green stars: "The fault lies not in the stars (well, not entirely), but within ourselves".
Followup: Green objects in space: "So,...
- 98k
34
votes
Could two planets follow the same orbit and never "see" each other?
Circular orbits are not practically possible
From Astronomy.SE, there are a variety of reasons why orbits are not circular. There is relativity, there is planetary flexing with gravity, there is ...
- 85.8k
31
votes
Accepted
What are the main problems with beaming light from the Sun to Saturn?
The problem is that "focused" does not really mean "concentrated"
Everyone that has ever played with a magnifying glass "know" that you can take the light from the Sun and turn it into an infinitely ...
- 44k
31
votes
How short can Milankovitch Cycles be on a world with a stable orbit?
Don't. Please just don't.
I have no idea how short such a cycle can be, but I can tell straight away that the idea of people capable of interstellar travel and colonization of new worlds not noticing ...
- 43.3k
31
votes
Permanent Full moon via "Magic"
The moon orbits the L2 Lagrange point. L2 orbits conserve energy and momentum, but they are not stable equilibria; over large periods of time they will always evolve into eccentric elliptical orbits. ...
- 11.2k
29
votes
Accepted
Initial conditions for a fluorine hellscape
Here goes nothing
Firstly, fluorine is not particularly abundant in the universe so you need a large source in order to get an atmosphere of it. Additionally, fluorine is easily consumed in stellar ...
- 6,756
28
votes
How difficult would it be to turn the Asteroid Belt into a single body? What's the best method?
How difficult would it be? Unfortunately, your timeline is too tight for any of the easy options to work.
The mass in the asteroid belt is highly concentrated. Between them, Ceres (~30%), Vesta (~...
- 17.9k
27
votes
Plausible reason for Earth not be able to get updates about terraforming on Mars?
One problem: I want the results of the terraforming to be something of a surprise to the arrivals. That requires that there be something that keeps Earth from getting broadcasts from the Martian ...
- 507
27
votes
How could a planet have a sky without stars at night?
The laziest answer is to just wait a while. If you wait an incomprehensibly-long while, eventually the expansion of the universe will move all currently near-by light generating bodies outside of our ...
- 279
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
27
votes
Accepted
Trying to survive a passing neutron star by burrowing deep in the planet's crust?
I think they'll be okay.
Let's start by figuring out what we're up against. Neutron stars can produce high-energy radiation through two means: thermal and non-thermal emission. Thermal emission is ...
- 102k
26
votes
Accepted
Stable ringworld interactivity with other solar system objects
TL;DR: Yes, helical motion around a ringworld is possible. However, it is far from uniform at larger distances (≥ 0.04 AU).
Summary of results:
For a toroidal ringworld with mass
$M_R = 3 M_\text{...
- 1,076
25
votes
Accepted
How would an advanced civilization have constant communication between planets?
I am going to assume that by constant, you really mean constant as opposed to instantaneous. In other words, we are still bound by the speed of light propagation delay. We are also bound by the laws ...
- 29k
25
votes
What could cause the Earth to be so endangered that mankind needs to relocate to another system?
I need something that isn't too far fetched
Should be able to manage this without exploding the Sun or igniting Jupiter, just rely on nutcase humans.
Nuclear and biological war within the Earth and ...
- 28.4k
24
votes
How would interplanetary stock-exchanges work?
They don't work.
You should ask a simpler question first. Why, when everything is conducted electronically, do all the stock brokers still accumulate around the exchanges?
The answer as you have ...
- 118k
24
votes
Can a planet have a day that's always longer than night?
You can have a binary star, and the planet in a Trojan position in the same orbit as the smaller of the two stars.
Basically, the two stars describe one side of an equilateral triangle, and the ...
- 55.9k
Only top scored, non community-wiki answers of a minimum length are eligible