What if there were no wheels?

Wheels are round and they roll. Bikes, buses, trains and shopping carts all have wheels.

What if there were no wheels at all? How would we move heavy things?

Look around and you'll find wheels everywhere: on bikes, cars, buses, trains, skateboards, wheelchairs and suitcases. A wheel is a round frame that turns on a rod called an axle, and it makes it much easier to move heavy loads.

But wheels had to be invented, and for a very long time people lived without them. What if there were no wheels at all? In this thought experiment, Olly explores how people moved heavy things before wheels, when wheels first appeared, and what a day without them might be like.

Encyclopaedia Britannica defines a wheel as a circular frame, solid, partly solid or spoked, that turns on an axle. Its value is not only in transport: Britannica notes that because the wheel made controlled rotary motion possible, it was of decisive importance in machine design.

This thought experiment removes the wheel and asks three questions. How were heavy loads moved before wheels? What does the archaeological record say about when wheels appeared? And what might a wheel-less day look like? The last is reasoning, labeled as ideas.

Long ago, people moved heavy things on sledges. A sledge is like a big sled that slides along.

People may also have rolled heavy things on logs.

Before wheels, people dragged heavy loads on sledges, flat frames that slide along the ground. Britannica says the idea of the wheel may have come from using logs as rollers under heavy things.

Sliding something heavy takes a lot of pulling. Scientists at the University of Amsterdam found that the right amount of water on sand halves the pull needed to drag a sledge over it. A wall painting from ancient Egypt shows a person pouring water on the sand in front of a sledge carrying a huge statue.

Sledges and rollers predate the wheel. Britannica suggests wheeled transport may have come from log rollers, and a Sumerian pictograph from Erech dated about 3500 BCE shows a sledge fitted with wheels.

A 2014 study supervised by Daniel Bonn at the University of Amsterdam (Physical Review Letters) pulled a laboratory sledge over sand: with the right dampness, capillary bridges make the sand about twice as stiff, sand no longer piles up in front of the sledge, and the pulling force halves. A painting in the tomb of Djehutihotep shows a person pouring water in front of a sledge, so the researchers argue the Egyptians probably used the trick.

Imagine no bikes, no buses and no trains. No wheelchairs, no strollers, no carts.

Moving things might be much slower and harder work!

Imagine waking up in a world without wheels. No bikes, cars, buses or trains. No wheelchairs, strollers or suitcases that roll. Every heavy thing might have to be carried, dragged on a sledge or floated on water.

Wheels do jobs that aren't about rolling along the road, too. Britannica describes ancient potter's wheels and waterwheels for lifting water, and mills turned by animals, water and wind. Without wheels, all these might have needed very different inventions.

Removing the wheel would remove more than vehicles. Britannica records the potter's turntable in Mesopotamia by 3500 BCE, waterwheels that lifted irrigation water in pots tied to the rim, and medieval mills in which animal, water and wind power were all harnessed through wheels; later, rotating machines driven by steam engines were important in the Industrial Revolution.

What a wheel-less world would actually look like is reasoning, labeled as ideas: transport might rely on carrying, sledges, boats and animals, and machines might need other ways to produce continuous motion, which Britannica notes linear motion cannot provide without reversals.

Dragging a heavy box is hard. It rubs on the ground.

A wheel rolls instead of rubbing, so pulling is much easier.

When you drag something, it rubs against the ground the whole way. That rubbing, called friction, makes dragging hard work, which is why the Egyptians' trick of wetting the sand helped so much.

A wheel on an axle doesn't drag its load along the ground. It rolls, and Encyclopaedia Britannica notes that sliding friction is usually 100 to 1,000 times bigger than rolling friction. The turning happens at the axle, where it can be made smooth: Britannica describes later wheels with iron hubs turning on greased axles.

Dragging a load means overcoming sliding friction across the whole contact with the ground; the Amsterdam experiments showed how strongly that depends on the surface. A wheel rolls over the ground instead: Britannica's friction article notes that coefficients of sliding friction are generally 100 to 1,000 times those of rolling friction for the same materials, an advantage realized historically in the move from sledge to wheel. The hub still turns against its axle, but that small surface can be greased: Britannica notes later developments such as iron hubs turning on greased axles and iron tires shrunk onto the rim.

Ground matters for wheels too: the Slovenian experts who studied the Ljubljana wheel suggest that on rough ground the cart probably had only one axle.

The oldest wooden wheel ever found is more than 5,000 years old.

It was found in a marsh in Slovenia, in Europe.

In 2002, archaeologists found a wooden wheel buried in the Ljubljana Marshes in Slovenia. Tests showed it is between 5,100 and 5,350 years old, the oldest wooden wheel ever found.

It is made from two panels of ash wood, with a square hole in the middle for an oak axle. Because the hole is square, the wheel and axle turned together. Experts think it belonged to a two-wheeled cart. The City Museum of Ljubljana has put it on display.

Found in 2002 at a pile-dwelling site in the Ljubljana Marshes, the wheel was radiocarbon-dated to 5,100–5,350 years old, at least a century older than wheels from Switzerland and southern Germany previously thought the oldest (slovenia.si). It is made of two panels of ash from the same tree; the 120 cm oak axle is about as old.

The square hole means wheel and axle rotated together, and experts suggest a single-axle, two-wheeled cart. Britannica notes that the oldest known wheels were wooden disks of carved planks, and that spoked wheels appeared about 2000 BCE.