Photograph by Marco Grob for Time
TIME

Meet the Twins Unlocking the Secrets of Space

Photograph by Marco Grob for TIME

The Kelly twins--one in orbit and one on Earth--may help NASA unlock the secret of long-term space travel

When Scott Kelly calls home from the International Space Station (ISS) sometime next year, whoever answers the phone may simply hang up on him. The calls will be welcome, but the link can be lousy, with long, hissing silences breaking up the conversation. That’s what happens when you’re placing your call from at least 229 mi. (369 km) above the Earth while zipping along at 17,500 m.p.h. (28,164 kph) and your signal has to get bounced from satellites to ground antennas to relay stations like an around-the-horn triple play. “When someone answers, I have to say, ‘It’s the space station! Don’t hang up!'” says Kelly…

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