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%...
  • 84.7k
129 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 ...
  • 41.9k
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 ...
  • 97.9k
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 ...
  • 28.8k
70 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 ...
  • 1,712
61 votes
Accepted

How would a Martian colony be able to celebrate Christmas?

Since Santa's death fortress is based on the North Pole of Neptune, he shouldn't have too much trouble making it to Mars. He and all of his reindeer are robotic, so they won't have any trouble ...
  • 45.8k
57 votes

Where in the solar system is the most viable place to put my colonists, after Mars and Luna?

The Asteroid belt. It has similar requirements for life-support systems as the moon. With the additional need perhaps for some areas with simulated gravity. It is next closest in terms of energy ...
  • 3,328
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 ...
51 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 ...
  • 37.4k
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 ...
  • 255k
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 ...
45 votes
Accepted

What happens if the sun disappears and then reappears some days later?

I'll start with Earth Earth is hurling through space at a speed of approximately $29.78 km/s$ If the sun were to disappear, the Earth would move in a straight line until the sun reappears. Since there ...
  • 5,545
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 ...
  • 2,827
40 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 ...
  • 3,130
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 ...
  • 901
38 votes

Where in the solar system is the most viable place to put my colonists, after Mars and Luna?

My choices: Ganymede and Callisto (and maybe Titan) This is perhaps a bit of a buzzkill, but I honestly would not recommend colonizing much in the solar system besides the Moon and Mars. Here's why I ...
  • 97.9k
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, ...
  • 294k
35 votes
Accepted

Blind spot in the Solar System

Get the ship as close to the sun as the ship can tolerate then maintain position between the sun and the earth. The sun is a strong gamma ray emitter. As long as the ship stays between the earth and ...
  • 52.4k
35 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,...
  • 77.8k
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 ...
  • 84.7k
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 ...
  • 39.8k
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 ...
  • 43.1k
30 votes
Accepted

What are the possibilities of a dwarf planet orbiting opposite Earth's orbit?

The point directly opposite Earth on the other side of the sun is called the L3 Lagrange point. It's not quite at the same distance from the sun as the Earth is, assuming that the body residing there ...
  • 45.8k
30 votes
Accepted

What would be the first thing humans would mine on Jupiter?

Skimming various gasses from the Jovian atmosphere or using superscience to extract metallic hydrogen from deep below the surface only taps a small amount of the potential resources available. Since ...
  • 97.1k
29 votes

How would a Martian colony be able to celebrate Christmas?

Fun question! I would expect at the start that Christmas would be celebrated when it happens back on Earth. As a species we'd all celebrate it at the same time (relatively). Meaning that Martians ...
  • 48.8k
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 ...
  • 6,706
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 (~...
  • 16.5k
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 ...
  • 497
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 ...
  • 294k

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