5
$\begingroup$

I want to create a world where it rains super hard to the point where it could kill someone but I also want it so that a person could live there without any sort of specialized equipment (Like a suit).

If I reduce the atmosphere then people wont be able to breathe and if I increase the gravity so that the rain falls faster then you wouldn’t be able to stand (plus that would also increase atmospheric pressure).

Edit: super hard (as in fast)

Improve this question
$\endgroup$
8
  • 3
    $\begingroup$ For reference, on Earth, BBC Science Focus Magazine says that "the terminal velocity of a raindrop depends on its size. The water droplets in clouds are only around 20 microns across and fall at only 1cm per second or so. This is normally balanced by updraughts, so the cloud stays in the sky. The droplets in a light shower are 100 times larger and fall at 6.5m/s or about 22.5km/h (14mph). The largest possible raindrops are 5mm across and hit the ground at 32km/h (20mph)." $\endgroup$
    – AlexP
    Commented Jan 7, 2023 at 0:29
  • 4
    $\begingroup$ I don't understand the apparent contradiction in your question : You tell your goal is to kill people with rain, but at the same time you want to have them live there without protection... What do you mean exactly? That in sunny or equivalent circumstances they can live? $\endgroup$
    – Tortliena - inactive
    Commented Jan 7, 2023 at 0:32
  • 3
    $\begingroup$ @Tortliena Well I’m writing a story so I can’t kill off characters the second they enter this place. I don’t want it to rain constantly so I want them to live when it’s not raining. $\endgroup$
    – Stevenjoy
    Commented Jan 7, 2023 at 0:57
  • $\begingroup$ @AlexP That’s a good idea. I’ll change the droplet size but maybe not too big because then it just wouldn’t look right. $\endgroup$
    – Stevenjoy
    Commented Jan 7, 2023 at 0:58
  • 2
    $\begingroup$ there is no combination of circumstance in which a human could survive in and rain will cause serous trauma. terminal velocity, surface tension, how rain has to form, and biological material strength are not that flexible. sometimes the only answer is handwavium $\endgroup$
    – John
    Commented Jan 7, 2023 at 1:54

2 Answers 2

Reset to default
14
$\begingroup$

Ice

To 'kill' someone with fast-moving water, you'd need something like a water-jet cutter to kill them by physical trauma. Sure, snow sure isn't going to kill someone that easily, but a half-meter-wide ice boulder falling out of the sky sure will.

Other than suffocating people with flooding from the torrential downpours, then I doubt you can kill people with rain.

Hail forms in strong thunderstorm clouds, particularly those with intense updrafts, high liquid-water content, great vertical extent, large water droplets, and where a good portion of the cloud layer is below freezing.

If you're going to have a fictional planet, then one with little tilt and large oceans could help to form planet-wide storms. It would probably help for it to be rather cold (on the far side of the habitable zone, or with less of a heat-trapping atmosphere).

Hail forms as precipitation in cumulonimbus clouds. As the droplets rise and the temperature goes below freezing, they become supercooled water and will freeze on contact with condensation nuclei.

A cross-section through a large hailstone shows an onion-like structure. This means that the hailstone is made of thick and translucent layers, alternating with layers that are thin, white and opaque.

Former theory suggested that hailstones were subjected to multiple descents and ascents, falling into a zone of humidity and refreezing as they were uplifted.

So you'd want a planet with perpetual cold thunderstorms. Quite the foreboding place!

Improve this answer
$\endgroup$
6
  • 3
    $\begingroup$ This is a thoughtful and detailed answer! One piece of advice: when quoting other sources, it's good to name them. $\endgroup$
    – Tom
    Commented Jan 7, 2023 at 2:51
  • 1
    $\begingroup$ @Tom Thanks! happy Neko noises* Next time I will, and for the OP, its wikipedia. $\endgroup$
    – Sam Kitsune
    Commented Jan 7, 2023 at 3:58
  • 3
    $\begingroup$ Nothing's stopping you from editing your question. It's even encouraged. $\endgroup$
    – JBH
    Commented Jan 7, 2023 at 4:43
  • 3
    $\begingroup$ From the same Wikipedia article: the largest officially measured hailstone had 7.9 in (20 cm) diameter. Much smaller ice pieces falling from the sky can kill you, especially if there's a shower of them. Of note: the weather doesn't have to be cold. In temperate zones, hailstorms are most common in the summer. $\endgroup$
    – Cloudberry
    Commented Jan 7, 2023 at 10:41
  • 1
    $\begingroup$ I've added a word-link to en.wikipedia.org/wiki/Hail . Feel free to undo my change if you don't like it. $\endgroup$
    – Goodies
    Commented Jan 7, 2023 at 11:50
5
$\begingroup$

there is no combination of circumstance in which a human could survive in and rain will cause serous trauma. terminal velocity, surface tension, how rain has to form, and biological material strength are not that flexible.

if you increase the gravity or make the air thicker, rain gets broken up even more by air resistance, so you only get smaller droplets.

if you make the atmosphere thinner to reduce air resistance, then it can't move enough water to make significant enough amounts of rain to get large droplets. at even at the bare minimum atmosphere low density pure oxygen, water still breaks up too fast to reach significantly higher kinetic energy.

Sometimes the only answer is handwavium

Improve this answer
$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .