The simplicity of immersed tube tunnels

The Channel Tunnel consists of an underwater network of over 200 kilometers in length

The passage beneath the English Channel between England and France includes three tunnels, crossover chambers, emergency passages, and air ducts. Burrowing teams in either country consistently checked their coordinates to ensure they would meet within two centimeters of each other.

How the underground maze below the Gaza Strip works

Hamas militants have constructed a web underneath the Gaza Strip filled with tunnels, residential areas, bunkers, and more. This article and illustrations explore the underground maze as detailed in photo and video evidence and witness accounts.

Manholes connect underground sewer and water drain pipes

Wherever a portion of sewer is connected to another, a manhole is built. These serve both as access points for maintenance and as connectors for the system. This video shows how crucial manholes are for proper sewer functioning.

Why are subway walls tiled?

In the early days of subway tunnels, architects needed to deal with dirt and moisture and make the cavernous stations less dank and dark. Ceramic tiles were easy to clean, and their glossy, bright finish helped illuminate the cave-like areas.

Essential pipes, sewers, and cables lie buried beneath New York City

The Department of Design and Construction offers a tour of its work sites, explaining the complex systems that exist underground. Gas, electrical, telecom pipes, and many others, sprawl out underneath the entire city, with dozens of maps that help workers know where they're placed. This layout is unusual compared to the rest of the country, where wires are often present and visible above ground.

Toronto's downtown has 18 miles of underground pedestrian tunnels

Known as the "Path," these tunnels have helped reduce pedestrian traffic on Toronto's busy downtown streets for over a century. They were first built by local business owners, prompting a network effect of add-on tunnels.

Explore the deepest parts of the ocean

The deeps of the Earth's oceans are some of the most extreme environments on the planet. Take a trip 36,000 feet to the deepest parts of the sea in this informative, 10-minute animated video.

Why water towers are built that way

Ingenuity and advanced engineering have allowed trains to overcome extreme landscapes

The Jungfrau Railway utilizes electric trains powered by hydroelectric energy to ascend the Swiss Alps, while Poland's Elbląg Canal hauls ships along cable-powered tracks driven by waterwheels. Germany's Wuppertal monorail navigates bends as it glides over a river valley, and New Mexico's Holloman High-Speed Test Track can achieve speeds of Mach 8.6 for rocket sleds.

The canal became the first use of lock-and-lake system at a massive scale

The system centered around Gatun Lake, the largest human-made reservoir at the time, and two massive concrete locks that helped raise the ships 85 feet from sea level to the lake surface. The excavation was also the largest earth-moving project at the time, moving 240 million cubic yards of soil.

Rain-catching tubes provide new hydropower source for tropical regions

An experiment in Singapore showed that charge separation could be established by rainwater flowing through narrow tubes. The separation, which creates a voltage, could be scaled up in regions of high rainfall to provide a clean energy source.

Wormholes, though unstable, would offer a theoretical shortcut through spacetime

These hypothetical distortions in the fabric of spacetime may connect vast distances across or even between universes. While science fiction often portrays them as traversable tunnels, the energy and matter required to keep a wormhole open defy current physical understanding.

Explore the animals that populate the depths of the ocean, from fish and coral in the first few hundred feet, all the way down to the bottom of the Mariana Trench.

Learn how to build your own vivarium

Creating a self-contained habitat for plants and microscopic animals requires a careful balance of organisms that maintain a cycle of water, nutrients, and other chemicals throughout. Bottlenecks in these cycles are mitigated through careful construction, such as incorporating a drainage layer to effectively manage water.

A photo gallery of underwater shipwrecks

Tobias Friedrich is a German scuba diver specializing in underwater photography. Check out this stunning gallery of shipwrecks as well as other galleries on conservation, sharks, and more.

Geothermal power can generate electricity and provide direct heating for homes

By drilling several kilometers through penetrable rock, wells can access highly pressurized groundwater warmed by thermal energy trapped beneath Earth's surface. This water can be turned into steam to create electricity in generators. Heating systems several meters deep can pump fluid underground before circulating it through buildings.

Explaining the engineering challenges of extracting metal-rich nodules from the seafloor

Proposed solutions for collecting these potato-shaped rocks involve lifting a slurry composed of them, organic debris, and water through several kilometers of flexible tubing to a ship on the surface, a process that is more difficult than pumping crude oil. One method would use compressed air, but this method is only 15% energy-efficient.

Oxygen and nutrients are circulated in tardigrade bodies through physical movement

Rather than having a circulatory system, oxygen is directly absorbed through their skin and spreads through a fluid called hemolymph as tardigrades crawl. When molting to grow, they shed their outer skin and stylets—sharp mouth parts used to pierce prey—which are regrown in their salivary glands.

Before the invention of transistors, vacuum tubes made radio possible

Discovered by Thomas Edison, vacuum tubes allow electrical currents to travel through empty space. Later modified into a diode—keeping current flowing in only one direction—vacuum tubes allowed electronics to turn alternating current into direct current.

The Boring Company was created by Elon Musk in 2017

While it started out as a subsidiary of SpaceX, the Boring Company became an independent entity in 2018. Musk started it with the aim of helping reduce city traffic via underground tunnels.

The most advanced 'bunker-buster' bomb can penetrate 200 feet below soil or concrete

The GBU-57 Massive Ordnance Penetrator is delivered exclusively by the B-2 Spirit stealth bomber, which carries only two at a time. Using GPS-guided fins and a steel alloy casing, it burrows 200 feet underground before detonating.

In 1963, a basement renovation in Turkey revealed a passageway to a hidden, multilevel underground city that once housed as many as 20,000 people

View the transition from laminar to turbulent flow

Using a dye released in the water, streamlines, which are parallel to one another and consistent at low flow velocities, become visible. As the water moves more quickly, viscosity cannot suppress the velocity change, and streamlines become chaotic, creating turbulence.

View examples of rift valleys, the product of surface divergent boundaries

At these boundaries, tectonic plates move apart, stretching and thinning Earth’s crust as long valleys are formed from smaller, interconnected valleys and troughs. Ongoing rifting and erosion can further sink the valley, becoming a rift lake if volcanic activity becomes inactive.

Scale models show the intricacy of WWI trench warfare

Every inch of these models of WWI soldiers in the trenches is crafted with amazing details, right down to the real-life letters written to home.

In 1915, workers recovered a submarine-like vessel from the Chicago River, prompting fears of German espionage

Explore a gallery of O'Neill cylinder space settlements

The structures consist of a pair of cylinders with a total enclosed land area of 500 square miles and can house several million people. Each is approximately 20 miles long, 4 miles in diameter, and contains three mirrors that open and close to form a day-night cycle inside.

The Foolkiller: The mysterious submarine at the bottom of the Chicago River

In November 1915, a submarine was found at the bottom of the Chicago River. It had been there for at least 10 years, was 40 feet long, and contained the remains of a man and his dog. To this day, no one knows who built it.

Massive 3D printers have been used to build homes by stacking layers of 'concrete toothpaste,' a fire-resistant material that effectively insulates against outside noise.

Stanford built a Google Maps for the Roman Empire, revealing how much it cost to travel in the ancient world

Planarian flatworms are small, aquatic worms with exceptional regenerative capabilities. When cut, the worms can regenerate multiple bodies in a matter of weeks.

Pure water does not conduct electricity because this flow of energy requires the movement of charged particles, and water is a neutral molecule.

For centuries, Niagara Falls has been a magnet for daredevils seeking to conquer one of nature's most powerful wonders, with its 200-foot drop and water rushing at 32 feet per second with 280 tons of force.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

According to the physics of black holes, our 4D reality may be a hologram—a projection of information coded on a 2D surface on the edge of the universe.

Power lines are dotted with large, brightly colored balls to improve the visibility of these thin wires to helicopters and small planes and help prevent potential crashes.

Explore what it's like inside a patient isolation unit, used in situations such as treating a patient or suspected patient with Ebola.

Watch how algorithms can be designed to train themselves and self-improve without human input, to the point where the optimized code is too complex for programmers to understand.

How fusion—which releases energy when two lighter atoms combine to form a heavier atom—differs from fission

Dorothy's famous entrance into Oz in 'The Wizard of Oz' relied on analog tricks, including a body double and sepia-toned paint, as much as it did on technology

To reduce wrinkles in clothing, research recommends gentle wash cycles with more water and tumble drying with smaller loads and longer times.

Children are now three times more likely to say they want to be a YouTuber when they grow up than an astronaut, with some even attending 'YouTube camps' that teach kids how to create content for the platform.

Take a 3D tour of the Hajj, Islam's annual pilgrimage to Mecca, undertaken by more than 1.5 million Muslims each year.

The American Society of Civil Engineers' infrastructure report card gave the US a C in 2025, its highest grade since the project launched in 1998.

Volcanoes 'die' when their supply of magma runs out, if they are shifted away from their underlying magma reservoir, or if they get clogged by collapsing or their magma cooling back into rock.

The use of fungi to detoxify land and water—a process known as mycoremediation—has been used to clean up natural resources affected by the 2025 California wildfires.

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

While the first exchange-traded fund (a 'basket' of different assets that can be bought and sold on a stock exchange) in the US only launched in 1993, the global ETF market has grown to more than $10T in the short time since.

SpongeBob exemplifies Aristotle's philosophy for living well because he understands that happiness doesn't come from external factors like money, recognition, or power.

Gerrymandering works through two techniques: cracking opposing voters across districts to dilute their power, and packing them into a few to waste their votes in lopsided majorities.