Chrohmie (@heychrohmie)

Two critical PHP flaws, rated 9.2 out of 10. Finland switched its government's public websites off, just in case. Here's what's underneath. Sources: php.net, NCSC-FI 37/2026, CERT-EU 2026-018, Yle 21 Oct 2026. Visual metaphors; stylised 3D animation. #PHP #CyberSecurity #HiddenEngineering #HowThingsWork #techtok

The gas under your street has no smell. So why does it smell like rotten eggs? If it's ever strong: get out, leave the switches and the doorbell alone, call from a neighbour's. Sources: 49 CFR 192.625, CT PURA, TSHA Handbook of Texas, HISTORY.com. 1937 scenes are a stylised reconstruction. #GasSafety #NaturalGas #HiddenEngineering #HowThingsWork #LearnOnTikTok

28 April 2025: Spain and Portugal went dark. Two countries, in seconds. How does a whole grid fall over at once? Source: ENTSO-E final report. Map simplified; reconstruction. #HiddenEngineering #PowerGrid #HowThingsWork #HeyChrohmie

These London houses have painted windows. Then you hear the rumbling. 23–24 Leinster Gardens, London. #HiddenInfrastructure #London #HowThingsWork #HeyChrohmie

A switch on the main line failed. The backup cable was already cut. Two separate failures held flights bound for five airports on 21 September 2026. What's the strangest reason your flight's been delayed? #HeyChrohmie #HiddenEngineering #Aviation #Infrastructure

Where does the rain on my street go? The hidden engineering of storm drains and combined sewers. In most of New York it goes down the same pipe as your toilet. A catch basin traps grit and trash, then it's off to the treatment plant, until a downpour, when it spills over a wall into the river. London built a 25 km super sewer to catch it. Next: how can one cut cable stop a whole airport? Sources: NYC DEP, US EPA, Tideway, Thames Water. #stormwater #civilengineering #howthingswork #hiddeninfrastructure #HeyChrohmie

How does the internet cross the ocean? The hidden engineering of undersea fibre-optic cables, and how Tonga's was fixed after the 2022 eruption. Cable ships lay it from huge coiled tanks, a sea plough buries it near shore, and out deep it lies on the bottom. Inside: copper for the repeaters and glass fibres about as thin as a hair. In 2022 an undersea eruption off Tonga broke its only subsea cable; a repair ship hooked up the broken ends and spliced in new cable. Next: where does the rain on my street go? Sources: TeleGeography, ICPC, UNEP-WCMC/ICPC, NOC/Durham University, AFP. #internet #submarinecable #civilengineering #howthingswork #HeyChrohmie

How do they build a tunnel under the sea? The hidden engineering of the Fehmarnbelt immersed tunnel, Denmark to Germany. A trench is dredged in the seabed, huge concrete elements are cast in a factory, sealed so they float, then sunk into place with ballast. The sea itself squeezes each joint shut. At 18 km it will be the world's longest immersed tunnel, and the train will cross in 7 minutes. Next: how does the internet cross the ocean? Sources: Femern A/S, Trelleborg. #tunnel #fehmarnbelt #civilengineering #howthingswork #HeyChrohmie

Why do roads suddenly cave in? The hidden engineering under your street. A road is built in layers, and the stiff top can span a hollow for a while. A burst water main can wash out the soil underneath, and water also washes soil into cracked sewers. Recently in Los Angeles, a van sank partway into one after a water main failed. In Yashio, Japan, in 2025, a corroded sewer pipe gave way and the road above caved in under a truck. Then: how crews find hollows with listening loggers and radar, and the signs to watch for on your own street. Next: how do they build a tunnel under the sea? Sources: ABC7 Los Angeles; City of Philadelphia; Caltrans Highway Design Manual; Minnesota DOT; Fort Worth Water; Hong Kong Highways Department; Bureau of Meteorology (Australia); nippon.com; Jiji Press; ASCE 2025 Report Card; NILIM (Japan); Institute of Water (UK); Asia Economy; City of Medford, Oregon; Inner West Council; Shoalhaven Water. #sinkhole #infrastructure #howthingswork #civilengineering #HeyChrohmie

Why are manhole covers round? And what's actually under one? One reason: a square lid can turn on its diagonal and fall through its own hole. A circle is the same width every way, so it can't. Then we go down the manhole to see the pipes under the street (water, gas and the sewer) and find out why some manholes in Manhattan, NYC, steam. What should I look under next? Ask me in the comments. Sources: Geometry Center, Solution #95 (Cover That Hole); Live Science, Why Are Manhole Covers Round?; Global Designing Cities Initiative, Global Street Design Guide (underground utilities); Con Edison, Steam Safety. #manholecover #infrastructure #howthingswork #civilengineering #HeyChrohmie