[katieHaylor (OP)]

David asks:

What method of time would you use in travelling through space? As a day, week, month or year would become meaningless. And how would this effect the body clock?

Any thoughts?

[alancalverd]

UTC applies everywhere and is essential for navigation, communication and extravehicular safety.

Not sure if it is still the case but astronauts used to wear ordinary aviator-style automatic mechanical wristwatches, Omega Speedmasters being preferred for lunar exploration. The designs and manufacturers for orbital work have varied from time to time, including some with 24-hour faces, but it's doubtful whether any electronic watch is reliable over an ambient range of  ± 80°C.

Installed equipment in the spacecraft will be in a temperature-controlled environment so quartz or atomic clocks are used for navigation, supply docking and experimental references. 

Loss of body clock rhythm is encountered on earth, in "jet lag", deep diving, and even some more "normal" working environments in the arctic winter that involve sleeping without reference to the sun. Hence the need for a standard timepiece and fairly rigorous shift rules.

[Bored chemist]

but it's doubtful whether any electronic watch is reliable over an ambient range of  ± 80°C.

Nor is my wrist.

[alancalverd]

True, but you wear the watch on the outside of your space suit, where things can get a bit extreme (hence the space suit). 

[Halc]

UTC works fine if you're in the vicinity of Earth where days and years are still very much meaningful, but in deep space, any clock will do. Alan points out that teams of humans working together need some sort of clock to synchronize work shifts and such, and a 7-day week still fills a psychological purpose.  It has no physical basis like the day, month, and year do.  In deep space, the day is probably a comfortable sleep/work cycle, and there is little reason to track something named a month or year, so you'd start to hear terms like kilo-day or something.

[Bored chemist]

People born on Earth  would still celebrate their birthdays.
Since it doesn't matter what system you use, why not stick with the one everyone is used to?

[evan_au]

The day on Mars (24 hours 37 minutes) is very close to a day on Earth (24 hours).

Given the huge advantages of working in daylight, it is certain that future Mars residents would adopt a Mars day. It is close enough to our natural circadian rhythm that people would adapt (even if older people needed a siesta to keep up).

But people in deep space (no days) or on the Moon (1 day=4 weeks) would probably stick to an Earth day, unless politics intervened.

UTC applies everywhere

Using results from Special Relativity: With the very limited speeds humans can achieve with chemical rockets, an atomic clock preset with UTC will give good time accuracy for a voyage beyond Pluto.

But if we were one day able to sustain 1g acceleration all the way to Alpha Centauri, you would need some fancy maths to keep it in step with a similar clock back on Earth, since time dilation becomes extreme at these speeds.

Using results from General Relativity: The extreme accuracy needed for GPS measurements means that GPS satellites have their atomic clocks preset to be 7 microseconds per day slower than their counterparts on Earth (before launch), so they will be in-step when they reach their final orbit.

See: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5253894/#Sec5title
PS: Ironically, when the first atomic clock was launched into orbit, some scientists and engineers still thought that Einsteins's relativity would have no measurable effect. It twas yet another case where Einstein came through with flying colors!

[evan_au]

For those space travelers remaining on Earth time, there will be political arguments about which timezone to use.
- Apollo astronauts used Houston time
- Russian cosmonauts used Moscow time.
- The ISS, as a joint international venture, uses UTC

You can be sure that there will be different timezones on the Moon if different nations create their own bases there.
- Joint bases may decide to use UTC
- If, in the distant future, Moon unity becomes more important than Earth heritage, we can expect arguments about which timezone to use (just as there were arguments about setting the zero longitude on Earth, from which UTC is measured).

At present, there are 8 timezones being used in Antarctica...
https://www.timeanddate.com/time/zone/antarctica
 

[alancalverd]

Fortunately everyday aviation and seafaring are above politics. UTC rules. I can't remember which trashy novel it came from , but I always recall the bit where a Mossad agent asked a Pentagon cipher clerk to send a message to Tel Aviv. Clerk said "Do you realise what time it is over there?"   to which he replied "It's 0300 Zulu everywhere."

I have no idea why idiot politicians get excited about time zones and stuff. The steam engine, penicillin, cricket, tennis, football (both codes), warm beer and zero longitude are just  gifts freely given by a civilised nation for everyone else to enjoy. The point of universal adoption of GMT (now UTC) was to prevent Brunel's trains from crashing into each other, so let's keep it that way.

[EvaH]

Asked and answered on this week's show! You can listen in here https://www.thenakedscientists.com/podcasts/question-week/how-would-you-measure-time-when-space

[strongernow]

David asks:

What method of time would you use in travelling through space? As a day, week, month or year would become meaningless. And how would this effect the body clock?

Any thoughts?

Really interesting question. Another one came to my mind:
If they don't measure time like on earth how do they know that they need to come back?