There is a line in space you cannot see. Below it, the sky above your head slowly repairs itself: a dead satellite is dragged down by the thin edge of the atmosphere and burns away. Above it, one collision scatters fragments that hit more satellites, which shatter into more fragments — debris multiplying on its own, even if we never launch again.

A NASA scientist, Donald Kessler, described this line in 1978. This year the European Space Agency reported that across several of the busiest orbits, we have quietly crossed it. This is not really a story about space — it is a story about what we all share but nobody owns.

The European Space Agency found the chance of a collision in low Earth orbit rose twenty percent in one year. We can track more than forty thousand objects; the fragments too small to track, but big enough to destroy a spacecraft, pass 1.2 million. A marble-sized piece travels at ~28,000 km/h — about ten times a rifle bullet — and hits with the energy of a small car into a wall.

In the busiest lane, 600–900 km up, alerts that two objects are about to pass dangerously close now arrive five to ten times as often as a decade ago.

Orbit has a natural cleaning service: a whisper of atmosphere reaches hundreds of kilometres up and gently drags things down. Below a certain crowding, debris is swept away about as fast as it piles up. Kessler's insight was that above a certain density that balance flips — collisions generate fragments faster than the atmosphere can remove them, and every fragment is a new bullet.

Once you are above the line, you need add nothing for the problem to grow. A 2025 study estimates the hardware already up there crosses that tipping point across almost every altitude from 500 to 1,000 km. The debris we already have is enough.

Graze one more cow and you get the whole cow; the cost — less grass — spreads thin across the village, so you barely feel your share. Every herder reasons the same way, and the pasture is stripped bare. Orbit is that pasture. You get your satellite's full value, while the risk you add spreads across every operator who will ever fly that altitude.

And under the 1967 Outer Space Treaty, no country can claim orbit — so no one can charge for crowding it, and no market signals that a lane is full. The price of the risk is invisibly small: about a tenth of one percent of satellite value a year. This is no single company's fault; much of the worst debris is decades-old rocket stages with no owner left.

Price it: charge a fee per satellite-year that rises as an orbit fills. A 2020 National Academy of Sciences model found a fee reaching ~$235,000/satellite/year by 2040 would more than quadruple the industry's value ($0.6T → ~$3T) — but only if everyone charges it, or launches flee to an orbital tax haven.

Own it: like radio-spectrum licences or tradable fishing quotas, cap and trade orbital slots — but the 1967 treaty blocks ownership, so it must be a right to use, agreed worldwide.

Clean it: 5-year deorbit rules and ~€100M removal missions help — yet cleanup alone recovers under 10% of lost value, a cleaner orbit invites more launches, and someone must pay to remove ownerless stages.

Nothing dramatic marked the moment we crossed the line — no explosion, just a twenty-percent rise in a technical report, a slow shift from a place that cleans itself to one that slowly breaks itself. Every fix — a fee, a market, a cleanup crew — hits the same wall: orbit belongs to everyone, so it belongs to no one, and the whole world must agree before any of them can work.

We have solved shared problems before, but usually when the fear was vivid and the fix was cheap. Orbit offers neither. The real question is whether we can act on a threat we cannot see — before the cascade decides for us.