The International Space Station, or ISS, is a football-field-sized laboratory orbiting Earth about 400 kilometres up, travelling at roughly 28,000 kilometres per hour. It has been continuously occupied for more than two decades, hosting astronauts from many countries who live and work there for months at a time. It is both a science laboratory and a testbed for the technologies needed for longer missions to the Moon and Mars.

Life on the ISS is unlike life anywhere on Earth. Astronauts float rather than walk, sleep in sleeping bags attached to walls, and eat food from pouches and cans. Water is recycled with remarkable efficiency, including moisture from breath and sweat, because every kilogram launched to orbit is expensive. Exercise is mandatory, about two hours a day, to counteract muscle and bone loss in microgravity, using treadmills, cycles, and resistance machines specially adapted for space.

Daily life is highly scheduled. Astronauts follow a timetable of experiments, maintenance, exercise, and communication with mission control, with weekends offering a little more personal time. They grow plants, test materials, study how the human body changes in space, and observe Earth from the Cupola, a windowed module that offers one of the most spectacular views in human history. Even simple tasks, such as washing or using the toilet, require special equipment and training.

The science done on the ISS ranges from biology and medicine to physics and Earth observation. Microgravity lets researchers study processes that gravity masks on Earth, such as how fluids behave, how crystals grow, and how cells respond to space radiation. Results feed back into medicine, materials science, and our understanding of long-duration spaceflight, which is essential if humans are to spend months travelling to Mars.

The ISS is also a remarkable example of international cooperation. Modules from the United States, Russia, Europe, Japan, and Canada fit together into a single station, and crews train together for years before flight. That cooperation, maintained through political changes on Earth, shows that large, complex space projects benefit from shared effort, even when they are difficult to manage.

The ISS will not last forever. Plans call for its eventual controlled deorbit after its operational life, with commercial space stations and lunar missions taking over as the next step. Its legacy, however, will endure: a continuous human presence in orbit, thousands of experiments, and a generation of astronauts and engineers who learned to live and work in space.

For skywatchers, the ISS is also easy to spot. On clear evenings, it appears as a bright, fast-moving star crossing the sky, visible to the naked eye for a few minutes. Watching it pass is a simple reminder that, right now, people are living and working above us, circling Earth every 90 minutes.

You can spot the ISS without any equipment by checking a pass prediction site for your location, which lists the time, direction, and brightness of upcoming passes. On a clear evening, the station appears as a steady, bright point moving quickly across the sky, brighter than most stars and without blinking lights, unlike an aircraft. It is visible for a few minutes before it enters Earth's shadow and fades.

For a fun family activity, try watching a pass together and explaining that the bright point is a laboratory with people inside, travelling at 28,000 kilometres per hour. It turns an abstract space station into something tangible, and it often sparks questions about space, science, and what it is like to live without gravity.

In the end, the ISS proves that people can live and work in orbit for months, and that experience is the foundation for every longer journey beyond Earth.