신비한사전

On a summer afternoon, the first thing to reach its limit isn't the power plant, but the cables buried underground. The concern isn't that they'll break, but that they'll overheat. Cables generate heat as they transmit electricity, and there's no wind underground to cool them down. The real problem was the soil. When a cable heats up, the moisture in the surrounding soil is pushed away, creating a dry band. Dry soil has five times the thermal resistance. It's like the cable is creating its own insulation while trying to dissipate heat. So, instead of making the cables thicker, they replaced the soil.

The footsteps from upstairs aren't coming straight down through the floor, but rather traveling along the walls and then down. Most apartments in Korea are built with a wall-frame structure where the walls are the main supports, so the floors above and below are essentially one solid piece. That's why even if you make the floor slab thicker, the vibrations will still leak out sideways. This is why performance has been poor even after increasing the thickness from 130mm to 210mm over the past 20 years. So, newer apartments don't just make the floor thicker; they actually decouple it. The floor you're standing on right now isn't touching the ceiling of the apartment below you.

1. Platypus Male platypuses have a venomous spur hidden on their hind legs. Getting pricked by it reportedly causes excruciating pain that even morphine can't alleviate. 2. Slow Loris The only venomous primate on Earth. When threatened, they lick venom from glands, mix it with saliva, and bite with their sharp front teeth. 3. Blue Dragon Sea Slug (Glaucus atlanticus) Despite its pretty appearance, it has a habit of eating venomous Portuguese man o' wars and concentrating their stinging cells in high amounts along its body edges. 4. Pitohui A bird found in the New Guinea forests. It looks like an ordinary songbird, but it feeds on toxic beetles, accumulating the deadly neurotoxin batrachotoxin in its skin and feathers. 5. Striped Skunk With its black fur, white stripes, fluffy tail, and waddling gait, it's truly adorable. However, wild skunks are also major carriers of the rabies virus, which has a 100% mortality rate, making them even more dangerous than their infamous odor spray. Personally, the platypus shocked me.

Ganghwado wasn't always shaped like it is today. Originally, it was a collection of scattered islands, large and small, with tidal flats in between where the water ebbed and flowed twice a day. When the Goryeo court fled here to escape the Mongols, the need for arable land became urgent, and thus began the land reclamation that has continued for nearly 700 years. The method is interesting. Instead of filling the tidal flats with soil, they built dikes to block the seawater. Work was only done during the lowest tides, and the dikes were built in a curve, like a bow, so that the incoming tide wouldn't hit them head-on. The vast fields of Ganghwa today are lands reclaimed from the sea in this way.

A stone bridge over 500 years old remains intact in the Jungnangcheon Stream in Seongdong-gu, Seoul. This spot happens to be where the Jungnangcheon and Han River meet, a place where the currents become fierce during the monsoon season. Wooden bridges would be washed away with every major flood, and the initial construction of the stone bridge also stopped midway, unable to withstand the floods. When construction resumed after 55 years, the approach changed. Instead of making the pillars thicker, they were cut into a diamond shape to split the water currents to the sides. Furthermore, out of the four pillars erected horizontally, the middle two were intentionally made lower to concentrate the weight of the deck inwards. It's a bridge that lets the water flow past rather than fighting it.

At 40 meters underground in Gwanghwamun, Seoul, a tunnel is still being excavated. Once completed, this 2.3km long tunnel will be able to contain 122,000 tons of rainwater. This method was devised because the area beneath Gwanghwamun is already packed with subways, electrical lines, communication cables, and water mains. This approach has already been proven effective. The Sinwol Rainwater Tunnel, completed in 2020, successfully mitigated the record-breaking downpours in 2022. The Gwanghwamun Tunnel is currently under construction with a target completion date of 2030.

Beneath playgrounds in Seoul's parks lie empty concrete rooms. Normally vacant, these rooms fill up with water when it rains. There are 32 such rooms in Seoul alone, capable of holding a total of 350,000 tons of water. They say the real problem with urban flooding isn't the amount of rain, but its speed. The issue is when a day's worth of rain rushes into the sewer system in just 30 minutes. So, instead of draining water quickly, Seoul chose to temporarily hold it back.

Beneath a 58-story mixed-use building in Seoul's Konkuk University area, three rainwater-only tanks are buried. The dilemma of a water tank is that it must be kept empty to prevent floods, but filled to use water. This building found a very simple solution. They divided a 3,000-ton space into three 1,000-ton compartments by building walls. One compartment is kept empty, one is used daily, and one is reserved for emergencies. Thanks to this system, the building reuses 40,000 tons of rainwater annually.

There are as many as 580,000 holes on the streets of Seoul. This is the only way for rainwater on the road to enter the sewer system. However, if these holes get clogged with cigarette butts and fallen leaves, the alley will be flooded that very day. Even though the Seoul Metropolitan Government spends 24.7 billion won a year on cleaning, it's said that the drains get clogged again within a few days of being cleaned. In the end, the Seoul government tackled not the trash, but the smell. They erased the very reason why people had covered the storm drains themselves.

Some of the pavement blocks laid on Seoul's sidewalks are designed to absorb rainwater directly. The impermeable land in Seoul, which was 7.8% in 1962, has now expanded to nearly half of the city. Because the ground can't absorb water, rain rushes into the sewer system, while rivers, conversely, dry up completely. However, these permeable blocks get clogged after just a few years and stop absorbing water. So, instead of relying on these blocks, the Seoul Metropolitan Government is lowering the curbs along the roadside flowerbeds. The transition from a city that sheds rain to one that drinks it is quite fascinating.