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I want to know what key invention would allow my civilization to travel down to and explore its world at sea level. This is similar to my previous question* but this time does not assume metals are in short supply so technology may develop as on our world.

This world is an alternate Earth. Similar size, mass and distance from its star as our Earth but with a much denser atmosphere. At sea level the pressure is around 3.2 bar, the temperature is around 50 degrees C and the humidity is 100%. At 5000m the pressure is around 2 bar, the temperature around 25 degrees C and the humidity ranges from 20-70%. The oxygen concentration in the atmosphere is around 15%.

The humans live on a very large plateau at 5000m and cannot descend to sea level unaided because of the high temperature and humidity. Assume that their technology progresses in a broadly similar fashion to ours. The humans there are physically just like us.

As this society develops from a primitive level to more modern technology what is likely to be the key invention that enables them to more fully explore their world? In cases where multiple answers are considered equivalent the answer using the earliest technology would be considered better.

*How can my fictional race of humans extend the area of their world they can explore?

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    $\begingroup$ Just a note, you may have heard before, but your world has many similarities to a Larry Niven creation, "Mt. Lookatthat on planet Plateau in the Tau Ceti system" larryniven.fandom.com/wiki/Plateau $\endgroup$
    – Gillgamesh
    Commented Sep 14, 2022 at 15:41
  • $\begingroup$ This is going to be a massively HUGE plateau, as it takes a critical number of humans to develop technology. Either that, or some evelutionary genetic fluke such that ALL humans are geniuses, not just a handful of the population. Also. I suspect the civiliation has already descended down in very deep mines, in order to extract resources. This link might be useful in understanding mining technology at such depths. mining-technology.com/analysis/… $\endgroup$ Commented Sep 14, 2022 at 16:27
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    $\begingroup$ VTC Too Story-Based. Nepene's answer underscores the fact that any number of inventions can be deemed necessary to achieve your stated goal and which one is "key" depends entirely on the circumstances of your story (there won't be just one, violating the help center's rule about answers having equal value). Further, please delete your final sentence. You're allowed one and only one question per post. How to achieve the invention is a different question altogether. $\endgroup$
    – JBH
    Commented Sep 14, 2022 at 16:35
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    $\begingroup$ @JBH I was attempting to specify the conditions so as to remove any discussions over the details of the environment. There may be problems however I do not think that they depend entirely on the circumstances of the story. I have removed the second question and modified what an ideal answer would contain (earliest technology = better $\endgroup$
    – Slarty
    Commented Sep 14, 2022 at 17:22
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    $\begingroup$ @Tortliena I had imagined the geography as variable to allow for a range of possibilities. Perhaps one side of the plateau drops off a cliff whilst the other side is a more gentle slope down to the hot lands below. Over a few dozen miles or more the vegetation would grade through temperate regions to tropical forest, rain forest, and then to some alien super rain forest. There would be rivers in places and perhaps some scree or rock slopes free from vegetation. As the area is so large the rock type can be variable if that helps. They could slowly clear the forest with suitable cooling. $\endgroup$
    – Slarty
    Commented Sep 14, 2022 at 21:16

8 Answers 8

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Refrigeration:

Out of all of the problems on your world, the heat and humidity are the largest. So with the invention of refrigeration, you should be able to counter these twin problems.

The first refrigeration systems were invented in 1854, and once you can cool your people off, they can survive. The other effects of this environment will be pretty severe, but with this primary problem solved, the others can be manageable.

Airships:

After this, aircraft will be the next big step. Powered airships were first built in 1852, and I suspect there will be huge pressure (pun intended) to build better ones fast. The La France, a fairly practical one, was built in 1884. I suspect that lighter-than-air ships will be huge. First, there will be no roads, challenging walking, and no harbors at sea level to build ships in to travel. Secondly, you will be wanting your people to be able to live in a lower-pressure environment (which the airship can rapidly climb to) as much as possible. Thirdly, in an airship, your people linger over areas of interest and use VTOL. Finally, airships of all kinds will likely be sealed to keep out the heat, and an enclosed environment will allow to control the partial pressure of the gasses inside (alleviating the worst side-effects of this environment).

You may even have tethered flying bases over strategic resources, allowing explorers and workers to live comfortably while surviving journeys to the surface, similar to those proposed for Venus.

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Digging.

Underground is gonna be the average temperature of the world, winter and night included, so it's gonna be a fair bit cooler. As such, humans will get very good at digging.

This means they can pop out for short incursions outside and then go back inside to get more water or refuel. This is just going to advance with technology.

Eugenics

Some people are much more heat resistant than others, and extensive training can make you more heat resistant. You can slowly breed and train heat resistance among a small dedicated group.

This is going to progress pretty slowly, with people with better genetics forming noble houses due to their superior genetics. It's gonna go much faster once they get a better understanding of genetics, and DNA sequencing.

Ice production

It takes a massive amount of energy to melt ice. This cools you down a lot. To extend outside time, many would rely on ice. You can make it underground, collect it from rare places, or make it with cooling chemicals. There used to be a massive trade in this, and in your world this would also happen. People would carry ice around with them to provide cooling when going outside to hunt or gather rare resources.

Refrigerated vehicles

This is gonna be the game changer. When you're high tech enough you can design vehicles which keep their occupants cool. With this you can go anywhere. Expect early development of mechanized suits and other things and a lot of experimentation on cooled vehicles.

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    $\begingroup$ The problem with a mine at lower levels would be the effort required to dig a mine in such an environment in the first place. I don't think any amount of acclimatization will work at 50 degrees C and 100% relative humidity. The temperature of a human body will rapidly increase to lethal levels. Ice might provide a small extension in the area of possible exploration so +1, refrigerated vehicles certainly would $\endgroup$
    – Slarty
    Commented Sep 14, 2022 at 17:30
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    $\begingroup$ Unfortunately, unless your conditions in the past were much colder, underground temperatures are pretty local as well. If there's a cool season, people would travel then. If not, underground will be hot, too. en.wikipedia.org/wiki/Geothermal_gradient $\endgroup$
    – DWKraus
    Commented Sep 14, 2022 at 20:46
  • $\begingroup$ You can dig a mine from the locations that are cool to the locations that are hot, or dig at night. And no, underground conditions aren't local and your wiki article is mostly about deep under the earth. architectmagazine.com/technology/going-underground_o Underground stuff is much more massive and dense than air, so it has a much higher heat capacity. It takes a long time to heat and cool it, so it has an average temperature of about what the surface is year round. $\endgroup$
    – Nepene Nep
    Commented Sep 14, 2022 at 23:06
  • $\begingroup$ Underground conditions aren't seasonal. They match the mean local temperature for that region until you dig deeper down and things get hotter. An underground shelter will only help if the cook-you-to-death summer is balanced by a freeze-you-to-death winter that brings the average down. Otherwise, you'll still have to actively cool it. $\endgroup$
    – BlockStop
    Commented Sep 15, 2022 at 14:27
  • $\begingroup$ I was saying to just dig to get under the ground, not saying to dig a kilometer deep where you get geothermal effects. $\endgroup$
    – Nepene Nep
    Commented Sep 15, 2022 at 16:29
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One large issue core body heat, and not being able to use sweat and evaporation to keep the body cool. The other is how long the surface of the body can withstand the heat. As a rule of thumb a hot water at 120 degrees F creates a serious burn in about 5 min. 130 degrees about 30 seconds. So the burn response is very non linear.

I think for the humans on the plateau to explore the hot humid wetlands, the biggest innovation would be a suit that protects the skin and provides cooling.

How to do that would depend on the technology level…

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    $\begingroup$ The more primitive the technology the better. A modified spacesuit with hitec cooling should be easily doable, but I wondered if a more primitive technology might work. What about some sort of torso covering hollow "pack" containing a low boiling point substance like alcohol, ether or even pentane. The boiling could absorb a lot of energy via latent heat in replacement of sweating, although it might need a short flue to keep the fumes a few feet above head level. I would have thought it might enable a few hours duration, but would need a cool space to retreat to and would be wasteful. $\endgroup$
    – Slarty
    Commented Sep 14, 2022 at 21:41
  • $\begingroup$ Nitpick: you can't decide if something is linear or not from two datapoints. $\endgroup$ Commented Sep 15, 2022 at 7:34
  • $\begingroup$ @ Jens Fair enough. This is more complete if you want to plot it. From googling...Most adults will suffer third-degree burns if exposed to 150 degree water for two seconds. Burns will also occur with a six-second exposure to 140 degree water or with a thirty second exposure to 130 degree water. Even if the temperature is 120 degrees, a five minute exposure could result in third-degree burns. I guess the human pain threshold is supposed to be around 106 to 108 F. Cell start to die around 110 F? and hot water heaters are set at 120 F to kill bacteria. $\endgroup$
    – UVphoton
    Commented Sep 15, 2022 at 13:03
  • $\begingroup$ @Slarty Maybe 1880s to 1930's tech? Walking around drives bellows in the shows to push a cool layer of air around the inside of the suit or a fan forcing air through tubes embedded in ice and recirculating that air. You would leave a trail of liquid behind you, but the latent heat of fusion is pretty large. The human body is about 100 watts, so relatively small heat load. So the real problem is heat conduction from the outside and burning the body. So if you could keep the contact points to the body cool that might work. $\endgroup$
    – UVphoton
    Commented Sep 15, 2022 at 14:44
  • $\begingroup$ @UVphoton Hot liquids transfer more heat far more quickly than hot gases. Here is a bizarre tale submitted in a comment on my previous question – a man and dog survived in a room with an air temperature of 126 degrees C whilst steak and egg cooked on a tin tray next to them – in very dry conditions the human and dog bodies were able to reject enough heat through sweating to survive an hour. Had there been much in the way of humidity they would have died quickly (can’t find the original ref but here’s the gist: royalsocietypublishing.org/doi/10.1098/rsnr.2018.0060 $\endgroup$
    – Slarty
    Commented Sep 15, 2022 at 17:05
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I think this is much harder than other answers suggest.

As written in DWKraus answer the first step would be airships. This can happen around 1800 to 1850 in Earth technology. These would not actually descend to the hot humid places but just stay up at approximately the height of the plateau and fly over the world. This gives you an idea of the general geography but not really anything else.

To actually enter the hot humid places you would need active cooling. A body suit might be possible with around 1900 technology but at best for a few hours. You can only walk in it, so you can only explore a couple kilometers away from your plateau. A wheeled vehicle won't be able to go through the wild, presumably this is a dense jungle, so this doesn't really help.

A flying vehicle with active cooling and support for some active cooling body suits might be around 1950 techs either as an airship or a helicopter. This would work for research exploration missions, similary to submarines on earth.

Establishing a semi-permanent research base is around current human technology. Any resource extraction would be completely uneconomical unless there is some supervaluable unobtainium to be found. A settlement is way into future tech.

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Pumps.

One of the great advantages of exploring your world at sea level is, by definition, the sea. It's right there.

In our world these are known as Sea Water Air Conditioning (SWAC) systems, and there's not really too much to them in principle -- pump up some very cold water from the benthic depths, and away you go.

Getting down there in the first place might be a bit of a hassle, or it might be as easy as falling (and falling, and falling) off a log.

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The Thermos

People have suggested refrigeration. A small fridge plant could certainly be portable, not so much for a large one. But if your insulation R value is good enough, small is fine.

I propose vehicles or buildings with evacuated steel cell walls (or super high R value materials, but vacuum seems easier with low technology).

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With that level of humidity, one can take into account the presence of large rivers. The river water would be cool enough during its flowing, so the initial exploration will be done by creating "colonies" downstream. Colonies would be cooled by the colder water from the rivers, maybe carried like for water mills. Basically, waterproof ship technology is needed (so you could create a room mainly surrounded by water). Within limits, you could create the equivalent of aqueducts to bring cold water to other places. The activity would be indoor during the day.

The second phase would need some kind of motorized pumps to cool the ships with river water, and would allow exploration both during day and night, in any kind of river or ocean (as long as the water temperature is cold enough, so not all the way). The ships will be semi-submersible (i.e. the main part of the ship will be underwater for thermal protection).

If there is a significant ocean, more exploration could be done by submersibles - that is, assuming that the underwater temperature is cold enough (on Earth, deep water temperature is around 4 degrees Celsius).

However, useful submersible ships require good metalworking technology and some kind of power source with enough "range". Based on our development on Earth, I assume electric plus batteries are "out" so that leaves some kind of thermal engine (wood plus steam probably, if coal and/or crude oil are not available). But thermal engine improvement will probably lead to cooling systems, so in the end the solution will be air-conditioned vehicles.

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  • $\begingroup$ A very good answer thx. Yes rivers would exist and starting in the higher ground would be relatively cool and the mass of relatively dense liquid would take a long time to be warmed by the relatively thin surrounding air. So rivers would likely be very important to exploration of the lower levels, probably from a fairly primitive level. But travel might be one way until a reliable propulsive system was developed (steam?) Just perhaps if there was a river with a shallow enough gradient, wind might be used, but it would be a bit hit or miss. $\endgroup$
    – Slarty
    Commented Sep 21, 2022 at 17:43
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Polymers

Virtually any climate, pressure controlled environment will require materials with properties that are obtainable with polymers.

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  • $\begingroup$ I can see that polymer materials would be very handy, but are they essential? What would be wrong with using steel or even pitch covered wood to build an airtight environment in a boat for instance? The most important aspect is exclusion of humid air and dehumidification, it shouldn't need to withstand much pressure. $\endgroup$
    – Slarty
    Commented Sep 22, 2022 at 17:30
  • $\begingroup$ To your example, watertight and air tight are not one and the same. But to my reasoning, I think if you consider the properties of any reasonable mechanism for conveyance into the specified environment that would provide reasonable chance for survival as well as ability to make observation required to meet the criteria of fully exploring their world, then unwind that to various sub components and mechanisms, and their sub components and mechanisms, etc., you would be hard pressed to create the end product without polymers. $\endgroup$
    – Mac
    Commented Sep 23, 2022 at 18:48
  • $\begingroup$ Perhaps, although I'm not entirely convinced. What about submarines and tanks from the first world war? Bakelite was only invented in 1907 and I doubt there was much if any plastic used in those craft. $\endgroup$
    – Slarty
    Commented Sep 23, 2022 at 22:51
  • $\begingroup$ Don't conflate polymers and plastic. Rubber, which was likely used in your examples, is classified as a polymer. It's based on a naturally occurring polymer, but it's refinement into useable rubber could be considered an invention, or technological advance. $\endgroup$
    – Mac
    Commented Sep 26, 2022 at 12:54

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