Hacker News Reader

> the surface area of a sphere at LEO is substantially larger than the surface area of the earth. I don't know the exact numbers, but I know it's a huge difference.

The surface area of the sphere is not much bigger, LEO starts a few hundred km up compared to the Earth's radius of thousands of km. Maybe 1.5x the surface area. But it expands in 3 dimensions: if the interesting part of LEO is 500km thick and a satellite takes up 10m of it from bottom to top, that's 50,000 concentric Earth-surfaces.

It's collisions that trigger a runaway Kessler syndrome. Collisions have happened before and they are a serious concern. Just ask the inhabitants of the space station, for example. Probability dictates that sooner or later, something or someone will run into you. I don't think Starlink is doing all that they can to safeguard their satellites, especially considering that managers were fired for not prioritizing quality over speed.

Then consider that orbital height expands the "surface area" of this satellite spread by an enormous amount....the surface area of a sphere at LEO is substantially larger than the surface area of the earth. I don't know the exact numbers, but I know it's a huge difference.

Surface area grows with the radius squared. Starlink are meant to be at (a max of) 1200km above the surface. Earth radius is 6371.

((6371 + 1200) / 6371)^2 = 1.41

There is 41% more surface area at their orbit than at sea level.

The problem is that these 11000 objects are moving among the existing ones. Some are nearly stationary on a geostationary orbit, while the LEO objects tend to zip around on wildly different orbits. So they are not sitting there, waiting to be found, but each object has a certain chance each orbit to hit some other object. These probabilities go up the more we put in orbit.

Bad explanation; the LEO and the Geostationary satellites will never ever bump into each other; they are in completely different orbits that never cross. Furthermore, we don't just randomly chuck these things into orbit without any thought or consideration. They do not 'have a certain chance each orbit' to hit something.

I think you're pretty much right, with the proviso that most satellites orbit in roughly the same plane.

> Imagine there are only 11,000 people on earth instead of 7 billion-- just the population of one small town, spread over all the oceans and all the continents.

But not evenly. There are certain orbits that most satellites try to stay in.

Consider that each person is as fast as Flash in the comics. And if two ever collide, each blood droplet just keeps going.