What Is Starlink? A Plain-English Guide

Starlink is a satellite internet service built and operated by SpaceX. You put a flat, self-aiming dish outside, it locks onto satellites passing overhead, and you get a broadband connection almost anywhere with a clear view of the sky — no cables in the ground, no phone line, no local ISP required.

That description would have fit satellite internet in 2005 too. What changed is the orbit. Every design decision that makes Starlink feel different traces back to one number: altitude.

The problem Starlink was built to solve

Traditional satellite internet uses geostationary satellites. A geostationary orbit sits 35,786 km above the equator, and at exactly that altitude a satellite circles the Earth once every 24 hours — the same rate the planet turns beneath it. From the ground the satellite appears to hang motionless in the sky, which is enormously convenient: point a dish at it once, bolt the dish down, and you never have to move it again.

The convenience costs you distance. Your data has to climb 35,786 km to the satellite, come back down 35,786 km to a ground station, and then repeat the trip in reverse for the reply. Light does not travel instantly. Even at 300,000 km per second, that round trip alone burns roughly half a second before anything on the far end has even started thinking about your request.

Half a second does not sound like much until you try to use it. Web pages open with a lurch. Video calls turn into people talking over each other. Anything interactive — a game, a remote desktop, a voice assistant — is unusable. Geostationary internet was fine for one-way streaming and email, and painful for almost everything else.

Latency is a distance problem before it is a bandwidth problem. You can add capacity to a geostationary satellite; you cannot move it closer.

Why low Earth orbit changes everything

Starlink satellites orbit at roughly 550 km — about 1.5% of geostationary altitude. The round trip that used to take half a second now takes a few milliseconds of actual flight time, and real-world Starlink latency lands in the 25–60 ms range depending on where you are and how busy the network is. That is not quite fibre, but it is squarely inside the range where video calls, gaming and remote work feel normal.

There is a second, less obvious benefit. Radio signals weaken with the square of distance, so a satellite 65 times closer is dramatically easier to talk to. That is why a Starlink dish is a flat panel the size of a laptop rather than the multi-metre parabolic dishes that geostationary links once needed, and why it can run on a household power outlet.

Why it takes thousands of satellites

Low orbit gives you speed and costs you coverage. A satellite at 550 km only has line of sight to a circle of ground a few hundred kilometres across, and it is moving at about 7.6 km per second — roughly 27,000 km/h. From where you are standing, a Starlink satellite crosses from horizon to horizon in a handful of minutes and then it is gone.

So a single satellite is useless for a permanent connection. To keep one satellite overhead at all times, everywhere people live, you need a whole constellation flying in overlapping paths. SpaceX has launched over 12,000 Starlink satellites to date, with several thousand active at any moment, arranged into orbital shells at different altitudes and inclinations so their coverage areas tile the globe.

In practice your dish is not talking to one satellite for very long. It tracks the best available satellite, and every few minutes the network hands your connection to the next one coming over the horizon — the same idea as a mobile phone moving between cell towers, except the towers are the things doing the moving.

• Orbit height: roughly 540–570 km for the main operational shells
• Orbital period: about 90–95 minutes for one lap of the planet
• Ground speed: roughly 7.6 km/s, or a horizon-to-horizon pass in a few minutes
• Handover: your link moves between satellites continuously, without dropping

What is actually on board a Starlink satellite

A Starlink satellite is deliberately unglamorous. It is a flat slab designed to stack like a deck of cards inside a rocket fairing, because packing efficiency is what makes launching thousands of them affordable. A single solar array unfolds from one edge after deployment.

The working parts are phased-array antennas for the user links, a second set for the gateway links down to SpaceX ground stations, a krypton or argon Hall-effect ion thruster for raising and maintaining orbit, star trackers and GPS for knowing where it is, and — on every satellite built since the v1.5 generation — optical laser terminals for talking directly to neighbouring satellites.

Phased arrays matter more than they sound. Instead of physically swivelling a dish, a phased array steers its beam electronically by shifting the timing of signals across many small antenna elements. That is how a satellite moving at 27,000 km/h can hold a beam on your roof, and how your dish can follow it without visibly moving.

How your data reaches the rest of the internet

There are two paths. The simple one: your dish sends data up to the satellite overhead, and that satellite relays it straight back down to a SpaceX ground station within its footprint, which is connected to the normal terrestrial internet. This is a bent-pipe relay, and it works wherever a ground station is reasonably nearby.

The interesting one: if there is no ground station in range — mid-ocean, deep in the Amazon, over Antarctica — the satellite passes your data sideways to a neighbouring satellite over a laser link, and the constellation relays it across space until it reaches a satellite that can see a ground station. Those optical links run at very high rates and, because light moves faster through vacuum than through glass fibre, a long path across the constellation can occasionally beat the equivalent undersea cable route.

What Starlink is good at, and what it is not

Starlink is genuinely excellent at one thing: delivering usable broadband to places terrestrial infrastructure has not reached and probably never will. Rural properties, boats, remote research stations, disaster zones where the ground network is gone, aircraft, and any situation where the alternative is nothing.

It is not a replacement for good fibre. Fibre is cheaper per megabit, lower latency, unaffected by weather, and does not share capacity with everyone else in your region. Starlink's throughput varies with how many subscribers are under the same satellites, heavy rain or wet snow attenuates the signal, and the dish needs a genuinely clear view of the sky — a single tall tree in the wrong place will produce brief dropouts every time a satellite passes behind it.

• Strong fit: rural and remote homes, marine and aviation, mobile and temporary sites, emergency response
• Weak fit: dense cities already served by fibre, sites with heavily obstructed sky, applications needing guaranteed fixed latency

Track the constellation yourself

Every satellite in orbit broadcasts a predictable path, and the orbital elements describing those paths are published openly. That is what this site is built on: the 3D globe on the home page plots every active Starlink satellite from its latest published elements and advances them in your browser in real time.

If you want the practical version of that, the pass pages tell you when a Starlink satellite will be visible from your own city tonight, which direction to face, and how high it will climb. The coverage view answers the other question — how many are above your horizon at this exact moment.