Long ago, in a dreamier era, space stations were imagined as portals to the heavens. In the 1968 movie "2001: A Space Odyssey," the huge structure twirled in orbit, aesthetically sublime, a relaxing way station for astronauts heading to the moon. It featured a Hilton and a Howard Johnson's.

The International Space Station (ISS) of the 21st century isn't quite as beautiful as that movie version, and it's not a gateway to anywhere else. It's a laboratory focused on scientific experiments. Usually there are six people aboard. When they leave, they go back home, down to Earth. Three came home Wednesday, landing in Kazakhstan.

The space station circles the planet at an altitude of about 400 km. Faint traces of atmosphere exert a drag on it, so the station must be boosted regularly to stay in orbit. In the grand scheme of things, the space station simply isn't very far away. The station has a phone number with a Houston area code.