Say you need to tell someone over the phone how long something is in your room. It’s easy: You take a ruler, measure the thing, and read the number to the person on the other end of the line. Scientists and much of the world use the metric system for this sort of thing.

This all sounds very precise, but how does anyone know how long a meter is?

Initially, the definition of a meter was tied to the Earth’s circumference. In the 1790s, the French defined it as exactly one ten-millionth of the distance from the equator to the North Pole. That’s about as objective as it gets, but is almost entirely useless in daily life: A tailor cannot triangulate the globe every time they need to cut a piece of fabric.

To make this whole measuring thing more practical, expeditions spent several years surveying the Earth, did the math, and forged a literal metal bar to represent that distance. For over a century, that was the “meter”: a platinum-iridium bar locked in a vault in France. If your wooden ruler matched the metal bar in Paris, you had a meter.

But a metal bar isn’t perfect either. It can expand in heat, contract in cold, and sustain microscopic scratches. As industrial technology and global communications demanded a higher degree of uniformity, the definition of a meter had to change again. First, it was pegged to the radiation emitted by krypton-86 atoms. Today, it is tied to the speed of light. A meter is officially the distance light travels in a vacuum, or exactly 1/299,792,458 of a second.

Practically speaking, these definitions are once again not super useful for everyday people. If a tailor needs to measure something, they will simply buy a tape measure at the hardware store. But when they do, they are participating in a massive, invisible chain of trust. The tailor trusts the hardware store, the store trusts the factory, the factory trusts the national laboratory’s calibration, and the laboratory aligns its equipment with the physical constants of the universe.

At the very foundation of this social chain of trust is a long history of human institutions having to agree on where the ruler starts, and where it ends. Which brings us to the surprisingly difficult question: How do we agree on anything?

Humans in a room

When addressing a complex problem, we might assume people will naturally gravitate toward the most accurate or efficient solution. But in reality, we rarely settle on an option solely because it is the “truest.”

Instead, as game theorist Thomas Schelling observed, humans are quite desperate for coordination. We land on an agreement, fundamentally, because the cognitive and social costs of disagreeing are too high. And to do so, we look for focal points, or a default answer that stands out just enough for people to expect everyone else to think of that answer. (For example, if you ask someone in North America to name a fruit, did they say “apple”?)

Once that agreement is locked in, a psychological shift happens: the very human habit of treating our abstractions as though they were a natural feature of the world. The sociologists Peter Berger and Thomas Luckmann called this “reification.” Once a decision is made, it’s water under the bridge. Our “objective reality” today is a bunch of these coordination problems. Once we solve one, we no longer need to think about it.

The invention of “now”

Time is humanity’s ultimate coordination problem. We tend to experience it as an absolute—a universal metronome ticking steadily in the background. But for most of human history, time was intensely local. Before the 19th century, it was “noon” whenever the sun reached its highest point overhead in your specific town. If you traveled from New York to Boston, you had to adjust your pocket watch upon arrival. There was no need for perfect synchronization because we just couldn’t travel fast enough to make the 12-minute difference matter.

Then came the railroad, moving people and goods across large distances on complex schedules. You cannot run a continental railway system when every station operates on its own local solar time, so standardized time emerged. But how did we end up with Greenwich Mean Time, and not Your-Hometown Mean Time? When delegates from 25 nations met in 1884 to base global time zones around the Greenwich meridian, that decision was a matter of geopolitical power as much as it was a matter of astronomy.

Even today, we treat time and the calendar as facts, but they regularly yield to economic convenience. This is why the International Date Line doesn’t drop straight down from the North Pole to the South Pole; instead, it zig-zags around political alliances. In 2011, the nation of Samoa literally erased Friday, December 30th, from their calendar, shifting their entire country across the Date Line because being a day behind their biggest trading partners—Australia and New Zealand—was bad for business.

In their research on how categories shape society, the scholars Geoffrey Bowker and Susan Leigh Star observed that every successful infrastructure becomes invisible. We only notice systems when they break down

Standardized time is a perfect example of invisible infrastructure. The irony is that only a few decades after the world’s governments decided to synchronize everybody’s clocks and create a universal, objective “now,” Albert Einstein proved that a universal “now” doesn’t actually exist: time is entirely relative, bending and stretching depending on speed and gravity. But by that point, people didn’t even blink—at the scale of human movement, Newtonian mechanics worked just fine, and the social infrastructure was already too valuable to abandon. And so, we keep using our clocks like there’s no tomorrow.