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When we one day become a space faring civilization we will probably stop using the gregorian calendar because why would you use that on say Mars? But there rea
by jezze 6y ago
When we one day become a space faring civilization we will probably stop using the gregorian calendar because why would you use that on say Mars?
But there really is no reason to get rid of the unix timestamp as a measure of time and this measure may stay around for a long time. This may mean that people in the future might consider 1970 as year zero where modern civilization began.
- Juliate 6y agoOr some other significant event in the eye of this civilization.
- NGC404 6y agoNext iteration of unix-time should include the concept of local time in context of relativty if we are going to travel or communicate over significant distances.
- remram 6y agoYou mean that from a remote place or fast-moving ship, the time on Earth would appear to go at a different speed? So local time would not just have a constant offset?
- komali2 6y agoYea, but if we're going to use a "number of seconds since ..." Type system like Unix time, SOMEONE has to be the origin point, so I don't think this is a knock against Unix time.
- kazagistar 6y agoIts unfortunate to use an accelerating reference (earth rotating sun, sun rotating galaxy, galaxy intermixing with andromeda) because it requires you to awkwardly keep track of the astronomy of earth for timekeeping. Instead, you would want a standardized reference time frame, say, "unix time assuming earth in 1970 never experienced any acceleratiom or dilation" and then everyone, including earth people, would track their acceleration and dilation offsets to be able to compare time when meeting or convert signal timestamps from any source back to their local time.
- ncmncm 6y agoQuasar time plus position, motion vector, and acceleration vector should be a good enough reference for anybody.
- remram 6y agoYou can't do math on that directly though. You'd still need to convert them to a common reference frame for comparison.
- remram 6y agoYou would want some global reference time, and that could be a number of seconds passing on Earth. However locally you can't work with a clock that doesn't tick at a constant rate (if seconds on your spaceship go twice as fast, the crew can work with that; if the rate changes day-to-day as you accelerate, that's a problem). In addition, you will probably want clocks that run at a given perceived speed, to time physical processes that take the same time everywhere (e.g. so your cookie recipe saying "bake for 600 seconds" work without translation).
- JdeBP 6y agoWell we already have to keep track of the size and shape of Earth. Go and read the SI Brochure from the BIPM. Local measurements by atomic clocks on Earth have to be weighted according to how far they are from a reference surface of equal gravitational potential. There's a publication named Circular T that comes out every 5 days. You don't need science fiction for this. * https://www.bipm.org/en/bipm-services/timescales/time-ftp/Circular-T.html https://www.bipm.org/en/bipm-services/timescales/time-ftp/Ci...
- daveFNbuck 6y agoIf time is moving at a different speed, it wouldn't just be a constant offset. You'd also need a multiplier. Think of two cars moving at different speeds on a road. They don't stay the same distance apart.
- linkdd 6y agoEinstein: There is no such thing as an absolute time Programmer: Hold my beer
- delecti 6y agoMore like: Programmer: Next iteration of unix-time should include the concept of local time in context of relativity if we are going to travel or communicate over significant distances. Einstein: Hold my beer
- SahAssar 6y agoHow? And what would be the place/value measured against? And would all "timekeepers" need to get signals from that place to get their offset? If so would we need to take lensing from gravitation into account? How do you even measure a global value when the local perspective by definition changes the value?
- shantara 6y agoIn "Deepness in the Sky" a spaceship's computer is still running on Unix time many thousands years into the future. It is generally believed that the calendar starts with the first Moon landing, and only the main character as a "programmer-archeologist" discovers a small difference between it and true Unix time 0.
- divbzero 6y agoLittle is known about “Unix” but it is believed he or she was a charismatic spiritual leader who brought hope, healing, and comfort to countless humans on Earth and inspired numerous disciples including “BSD”, “Linux”, and “System V”.
- throw0101a 6y ago> Little is known about “Unix” but […] As opposed to eunuchs.
- ithkuil 6y agoWell, isn't Unix a castrated Multics?
- gerikson 6y ago"A Deepness..." also used SI multiples of seconds to denote something approximating 24 hours, a week, a month etc.
- fanf2 6y agoA megasecond is a useful quantity: it's a bit less than 12 days. I mentally approximate it to a fortnight, partly because of the VMS bootloader which used microfortnights as an approximation for seconds https://en.wikipedia.org/wiki/List_of_unusual_units_of_measurement#Microfortnight https://en.wikipedia.org/wiki/List_of_unusual_units_of_measu... Another handy time_t approximation is that a year is about 2^25 seconds, or 32 megaseconds.
- 6y ago
- BoppreH 6y agoThere is a very good reason to eventually abandon it: leap seconds. Unix time goes back one second whenever there is a leap second on Earth. It's extremely weird and IMHO completely ruins the purpose of a timestamp, but it's a compromise for backwards compatibility, since Unix time was created before leap seconds. This hack ensures that the number of seconds in a day remains fixed, an assumption of many systems at the time.
- JdeBP 6y agoLeap seconds were introduced in 1972. The time_t that you are thinking of was invented somewhere around 1974, according to Unix historians. Ironically, your kernel measures TAI time perfectly happily if unmolested, as that always ticks once for every SI second (ignoring oscillator drift). No slewing. No smearing. No stepping.
- iso1210 6y agoWhy would someone on Mars, or an asteroid, or orbiting venus, care about leap seconds on earth? Number of seconds since a given time seems fine until we're travelling significantly outside of a common reference plane.
- beagle3 6y agoThat’s exactly why op said we should abandon Unix time. The “who cares about leap seconds” standards is called TAI, and the difference between TAI and Unix time changes every time a leap second is introduced. Unix time decrees every day has exactly 86400 seconds. But the introduction of leap seconds means that While most days have 86400, some earth days have 86401 seconds and potentially there could also be days with 86399 TAI makes sense everywhere, Unix time only on earth.
- BoppreH 6y agoBecause that's not how Unix time is defined. The leap second hack is hardcoded into it: Unix time is [...] the number of seconds that have elapsed since the Unix epoch, minus leap seconds. - Wikipedia If you are on Mars you'll have to update your computer time every ~6 months when Earth release a new table of leap seconds caused by e.g. earthquakes.
- tgsovlerkhgsel 6y agoWith Earth's day length becoming irrelevant, the 24 hour clock becomes irrelevant too, and the length of the sleep cycle may shift. We could eventually arrive at stardates with one starday being 100000 seconds. Of course, that would be just as arbitrary as simply keeping the 24 hours of 60 minutes each.
- withinboredom 6y agoHumans have a remarkable circadian rhythm that does a pretty good job at defining a day as “24 hours.”
- inglor_cz 6y agoThere were experiments with forced desynchronization of human circadian rhythms. http://www.chronobiology.ch/wp-content/uploads/publications/2007_02.pdf http://www.chronobiology.ch/wp-content/uploads/publications/... They were very limited, though. We do not really know what would happen on a spaceship that changed its day to 100 000 seconds and subjected the crew to this cycle for months or years. Given how adaptable people usually are to external influences, I would guess that some adaptation would take place.
- tgsovlerkhgsel 6y agoTo my knowledge, once you take the sun away, it tends to drift more towards 25 or 26 hours. And that's in humans who experienced the externally imposed 24 hour cycle for decades before participating in a short experiment, not potential spacefarers born onboard of stations or ships.
- peter303 6y agoThe galactic GPS would be based quasars, e.g. far away galaxies, that would pretty much appear the same positions anywhere in the Milky Way. Quasar spins are gradually slowing down. So you could tell how many light years you are from the quasar by the observed spin rates. In addition, you can determine epoch time from knowing position a spin decay rates. Carl Sagan put a quasar GPS on a golden plaque on both Voyager probes, so future intelligences could tell where and when the Voyagers came from.
- canofbars 6y agoWont there be issues using the same time on different planets since time speed is not constant?