Questions tagged [reality-check]

Asks if a given concept is realistic in a given context. Answers should say yes or no, with supporting info. Compare this with the science-based and hard-science tags. This tag should never be the only tag on a question, because this tag frames how a question should be answered, not the topic.

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57 votes
6 answers
13k views

Could two planets be tidally locked to each other so close they share their atmosphere?

Could two planets be tidally locked to each other at such a small distance from one another that they share their atmosphere, and material is floating around between the two?
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72 votes
17 answers
15k views

Stealth in Space: How realistic is it?

This has been considered other places on the net, but I thought it would be good for the hard-science challenge, since it is often an example of the subtle difference between soft and hard science. ...
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33 votes
8 answers
26k views

Anatomically Correct Angels

As part II of anatomically correct myths here we have the Angel. Angels appear in many cultures and are most commonly seen as simply winged humans. Is there a realistic way that angels could evolve? ...
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64 votes
6 answers
21k views

Other blood colors

Many people know that our blood is red because it is iron based. Many people also know that blood is blue or green if it is copper based. I'm wondering what color blood would be if it was let's say ...
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37 votes
11 answers
10k views

Would humans be able to derive nutrition from foodstuffs found on alien planets?

Suppose humans have developed the technology to travel between star systems. This might be some science-fiction method like warp drive, jump drive, peanut butter drive, hyperspace drive or whatever, ...
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34 votes
16 answers
13k views

Can airborne floating/flying islands be scientifically possible?

I'm sure that this has been asked before, but I need floating islands for a fiction story I'm writing. It takes place 5000 years after a catastrophic event (on a vaguely earth-like planet populated ...
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75 votes
6 answers
4k views

Are geographically typed planets realistic?

In many science fictions we see planets which are designated by a particular terrain type. For example, Dagobah is a swamp planet, Tatooine is a desert planet, and Kamino is an ocean world. However, ...
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267 votes
22 answers
53k views

What's the smallest change to physics required to allow magic?

Yesterday my 7-year-old daughter asked me: Why can't I do magic for real? I answered: because of the law of conservation of energy! And I briefly explained this law. Thus she grumbled, "a ...
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38 votes
13 answers
19k views

Could a creature evolve a biological "bulletproof vest"?

A variety of Earth species have hard, more or less rigid shells covering parts of or their entire bodies as a defense against predators. These work to a varying degree depending on the specific ...
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31 votes
11 answers
28k views

Can a nonspherical planet exist and can it be habitable?

In both fiction and non-fiction worlds, that attempt to keep a sense of realism, planets are spherical. Is it possible for a planet to not be shaped like a sphere? If such a planet is possible ...
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70 votes
15 answers
13k views

What would be left of a civilization founded in dinosaur times?

65 million years ago, a mass extinction event (likely caused by the Chicxulub Meteor) wiped out the dinosaurs, and their remains were hidden from us for millions of years. Humanity was not around ...
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9 votes
5 answers
2k views

Giving Tolkien Architecture a Reality Check: Dwarvish Kingdoms

Having escaped Isengard and left Rivendell, we are off to destroy the Ring. Our first stop--Khazad-dum, known contemporarily as "Moria". Being a Dwarvish kingdom, the problems I see with Moria are ...
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23 votes
4 answers
5k views

How does a society domesticate the hippo?

Hippo's are one of natures most efficient food > weight animals, making them perfect for food. Additionally they are arguably the most dangerous land mammal, meaning they are hard to domesticate, very ...
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126 votes
19 answers
40k views

Could a planet made completely of water exist?

In the Star Trek: Voyager episode "Thirty Days", there was a planet made completely out of water, which is the inspiration for this question. However, that planet was held together by an artificial ...
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37 votes
20 answers
8k views

How would people tell time if it was always day?

So, if I have a civilization that lives in a hollow planet, with a sun in the middle. How would they tell time? The sun always shines, and it is a Constant Spring/summertime weather. They have animals ...
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23 votes
5 answers
5k views

How would a civilization that has been living on a "cube" Earth differ from one on a "spherical" Earth?

Another question based off of this one here. Let's say on a cube styled Earth-like planet, there was a similar race to humans. If the differences in the planets were minimal (besides, you know, the ...
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54 votes
11 answers
23k views

For how long after an apocalypse would modern cars remain usable?

Imagine a "soft" kind of apocalypse - nothing like Earth being hit by an asteroid. In particular - 90% of human population have just disappeared (no matter why). So there are abandoned cities and ...
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27 votes
7 answers
7k views

Could life form in outer space?

All life we know of to date (presumably) formed on a rocky planet (more precisely: earth). Fiction has been written about life in more exotic locations. Though as far as I know, these lifeforms were ...
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24 votes
3 answers
4k views

What colour is the foliage if the sky is violet?

This question on Physics.SE asks whether other colors are possible for the sky. I would like my planet to be inhabitable by normal humans. It has 768 days and they are living in a temperate/...
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16 votes
8 answers
3k views

Is the Idea of a Collective Consciousness Realistic?

In how smart can I make ants, an idea was suggested, to instead of making each ant individually sapient, make the 'anthill' as a whole sapient; a kind of unconventional hive mind. Just as a familiar ...
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117 votes
11 answers
23k views

Could a Dwarven Civilization Exist?

Could a Dwarven society as described by Tolkien mythology actually work? Dwarves for the purposes of this question are short, stout, bearded men and women who live primarily underground. They have a ...
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13 votes
4 answers
2k views

How do I figure out my planet's biomes and weather?

I'm having trouble figuring out the various biomes for my planet. I have extensively read the post on "Creating a realistic world map - Currents, Precipitation and Climate". But to be honest, I'm hung ...
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41 votes
5 answers
11k views

How would multi-race humanoid evolution happen?

If we were to pull the following races out of a D&D players handbook and remove them from the setting/history of Faerun and look at them from a biological/non-magic perspective (no other planes of ...
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  • 32.5k
27 votes
8 answers
11k views

Anatomically Correct Griffins

As a series of anatomically correct myths, here we have the griffin. Is there a realistic way that griffins could evolve? Using Earth or near-Earth biology, how close could I get to the classic ...
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  • 55.2k
43 votes
15 answers
10k views

Is a jet dragon possible?

Are there any known laws of nature, which don't allow the existence of an animal with following characteristics? Can fly to the altitudes of modern airliners (around 10 000 meters or 32808 ft). One ...
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26 votes
6 answers
9k views

Maximum size of an exoskeletal creature

On a world I am building, I have a species of creatures that evolved from crustaceans. The problem is that while they have an exoskeleton, they also live on a world with the same gravity as Earth. I ...
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31 votes
5 answers
9k views

What would be the consequences for Earth if the moon disappeared?

Scenario: The Moon disappears slowly -- within 3 days. It is a result of natural causes and we don't have any control over this disaster. What will be the Major Effects On Earth and life on Earth?
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16 votes
12 answers
5k views

Why would humans be the dominant species?

Humans, in most fantasy stories including in my own, are the dominant species. Why is that? Firstly, I guess I should give every race in my story strengths and weaknesses. Humans (same as us) have ...
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  • 6,043
43 votes
12 answers
6k views

Multiple DNA, one creature

Suppose a species possessed different sets of DNA for different parts of its anatomy. I'm not suggesting one set for every function in the body; that would result in hundreds of thousands of unique ...
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2 votes
4 answers
940 views

Could my Wyverns exist?

A long time ago, Yi Qi diverged into three main groups: Cockatrices, Drakes, and Wyverns. Some characteristics of Wyverns include: They are tetrapods/quadrupeds They are covered with feathers The ...
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90 votes
20 answers
147k views

Possible distance travelled by horse over 6 weeks?

I always get very annoyed if a writer is sloppy with maps and travel-distances. E.g. "They left city Y and arrived in city X 5 days later." When you look at the supplied map Y and X are a 1600 ...
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20 votes
3 answers
3k views

Minimum brain size for consciousness?

In the limit, how small can a brain get and still host an identifiably human-like consciousness? Obviously, they can be smaller than an adult human's, since children (with smaller brain volumes) and ...
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32 votes
8 answers
6k views

Can we 'beam' energy from the moon?

Really can't believe I have to edit this in, but this question has no bearing on our current use and generation of nuclear energy on Earth. There are dangers to nuclear energy generation, or we would ...
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9 votes
4 answers
4k views

Anatomically correct Giants [duplicate]

What genetic traits would be needed to have a human that is "normal" in all aspects, but roughly 50 to 80 feet tall? This doesn't seem completely out of the realm of possibility considering some ...
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70 votes
21 answers
15k views

How do we tell if we're living in a virtual reality world?

Since I haven't found anything like this yet. I was reading a novel and it talked about how some people created a 'Artificial Virtual Reality World' where the denizens were Human Artificial ...
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  • 10k
26 votes
5 answers
21k views

Humanoids with digitigrade legs?

I've designed an alien race of bipedal humanoids with digitigrade legs. This race's advanced scientific progress means that they use traditionally human-associated technology, or similar (such as ...
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  • 3,527
35 votes
7 answers
5k views

I'm stranded on an alien planet. How can I tell what's good to eat?

Survivor, Season 435 (teaser trailer): The holocamera pans over the night sky, revealing an utterly unfamiliar set of constellations. A blur, familiar to viewers, starts to disturb the seeming peace ...
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28 votes
8 answers
10k views

How would societies be if created and populated only by young people?

I’m writing a post-apocalyptic RPG, but I have a problem when dealing with the reconstruction of the society. The apocalypse left alive only the young people up to 21 years of age. Even though the ...
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43 votes
5 answers
6k views

Could a humanesque creature derive all its nutrients from drinking blood?

Vampires are a very common creature in various fantasy stories, they drink blood and often human food poisons them. Forgetting for the time being the additional rumours/fiction such as sunlight, ...
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33 votes
25 answers
8k views

Aliens are on their way. What can cause them to not understand us?

This question continues the premise set in my previous question, but do not worry, I will try to tell the most important bits: There is intelligent alien race about 30 light years away from us. They ...
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44 votes
6 answers
6k views

How do I prevent my turtle from collapsing under its own gravity?

Suppose the universe contained a species of planet sized turtles1 that can travers at least interstellar space. How can I explain (without invoking magic) that these turtles are not spherical? If ...
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  • 5,535
23 votes
6 answers
3k views

Living Planet Possible?

Although a question about how large a living thing could be has been asked and answered, would a being such as Mogo from DC's Green Lantern series be possible? Mogo is the size of Earth roughly can ...
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16 votes
6 answers
4k views

What would a Collective Consciousness look like?

The idea of a collective consciousness (Or Anthill) is pretty simple: instead of cells you have small sentient animal that make up a larger creature. This is different from a hive mind in that the ...
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25 votes
8 answers
4k views

Could a city be built out of Balloons?

I would like to use this scenario in writing a book. Using only countless balloons that permanently hold hydrogen made from water could a city be built in the sky? Workers from the ground can raise ...
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3 votes
5 answers
3k views

Speeding up time?

Any ideas how an advanced alien race could speed up time in a specific region of space? I'm working on a storyline in which an alien race uses a time bubble to accelerate time so the construction of ...
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6 votes
4 answers
6k views

Is this concept for an LTA-gas' associated element lifecycle feasible?

Introduction: I've spent some fair amount of time thinking about inventing an element to make part of my world easier for me. In this case, it is an LTA gas which I gave the WIP name LAL-gas (Leichter ...
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  • 12k
16 votes
10 answers
7k views

Could humans alter the moon's orbit significantly with current technology?

A terrible virus has made most of the populations and government officials of the largest superpowers on Earth stark, raving mad, without depriving them of their intelligence. They have decided that ...
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98 votes
15 answers
30k views

If the Romans found one working steam engine would they have been able to copy and use it?

I Previously asked if the Romans could have built a steam engine to power a ship, which received a number of answers perhaps best summarised as “probably not but…”. Assuming the Romans couldn’t have ...
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28 votes
13 answers
14k views

How to avoid objects when traveling at greater than .75 light speed. or How Not to Go SPLAT?

After asking my question about seeing black holes in your path between the stars, I also wondered abut other more mundane objects. Black holes affect large areas of space so even if you didn't get '...
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  • 48.7k
35 votes
21 answers
7k views

How could a species survive on just luring in and eating humans?

In a question about mermaids, it was proposed that they might have evolved to look like humans to lure them in and prey on them. How could a creature survive on a diet of nothing but lured-in humans? ...
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