What Time is it in Space?

Answer 1

An interesting question. For my money, there is no time in space. Time is a human construct devised as a way to regulate our environment, and based on the astronomical accident of the rotation speed of the earth. If you think about it, was there time for Neanderthals? No. They hunted when it was light, they ate after the hunt and they slept when it was dark. But we don't live that way. We need to know what the time is so we can get to work at 8:30. The only reason we know it's 8:30 is that someone took the rotation of the earth and divided it into 24 periods it called hours. It doesn't quite revolve that conveniently; that's why we have extra time to tack on at leap years, but it's close enough. So now we have constructed time, we can have trains leave on time and pace themselves so they arrive at their destination at a prescribed time, and not just as fast as it can get there. Planes have a schedule, doctors have surgery schedules, schools have 8 40 minute periods in a school day. But where there are no people, there is no need for time. No doubt when we go to live on Mars, they will create time based on the Martian rotation; that way the day shift knows when to end and the night shift knows when to go to work, and the barman knows when it's time to close the bar. Time is totally artificial and based on the environment of those who live in it.

Answer 2

Because "clock time" on Earth depends upon the rotation of the planet, vehicles in space technically have no "time of day" to reference. Those orbiting Earth might be over a particular time zone for part of their flight, but cannot measure the same rate of time passage. So space flight utilizes a time system similar to aircraft schedules, which are all expressed in Universal Time or UTC (equivalent to GMT and military Z or Zulu time) to avoid discrepancies in flight, takeoff, and landing times. (These are converted to local time at individual locations.) Because of relativistic effects, the fast-moving space station's clocks will actually run ever-so-slightly more slowly than clocks on Earth, a discrepancy of about 4 seconds per year.