The Last POWER1 CPU on Mars Is Dead • Hacker News Board

Re: The Last POWER1 CPU on Mars Is Dead

#51

Post by matt4077 » Mon, Feb 25, 2019, 9:33 PM UTC

hackbinary wrote: post #48

JumpCrisscross wrote: post #9

Earlier quoted context omitted.

> Do we humans have plans in the pipeline for a universal time standard we can use wherever we are? This fundamentally cannot exist. Any "universal" system would drift for observers on different planets. Having different times in New York and New Delhi isn't the worst right now; doing a calendar look-up for the time on Mars isn't as neat. But given we won't have real-time communication, it isn't as big of a problem e…

I thought a second was a SI base unit: (from Wikipedia) The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency {\displaystyle \Delta \nu _{\text{Cs}}} {\displaystyle \Delta \nu _{\text{Cs}}}, the unperturbed ground-state hyperfine transition frequency of the caesium-133 atom, to be 9192631770 when expressed in the unit Hz, which is equal to s−1.

I believe they are referring to the relativistic drift experienced when comparing two observers moving with high relative speed.

Re: The Last POWER1 CPU on Mars Is Dead

#52

Post by jldugger » Mon, Feb 25, 2019, 9:34 PM UTC

hackbinary wrote: post #48

JumpCrisscross wrote: post #9

Earlier quoted context omitted.

> Do we humans have plans in the pipeline for a universal time standard we can use wherever we are? This fundamentally cannot exist. Any "universal" system would drift for observers on different planets. Having different times in New York and New Delhi isn't the worst right now; doing a calendar look-up for the time on Mars isn't as neat. But given we won't have real-time communication, it isn't as big of a problem e…

I thought a second was a SI base unit: (from Wikipedia) The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency {\displaystyle \Delta \nu _{\text{Cs}}} {\displaystyle \Delta \nu _{\text{Cs}}}, the unperturbed ground-state hyperfine transition frequency of the caesium-133 atom, to be 9192631770 when expressed in the unit Hz, which is equal to s−1.

This is true, but does not compensate for relativistic time dilation.

Re: The Last POWER1 CPU on Mars Is Dead

#53

Post by ramses0 » Mon, Feb 25, 2019, 9:35 PM UTC

yingw787 wrote: post #33

JumpCrisscross wrote: post #9

Earlier quoted context omitted.

> Do we humans have plans in the pipeline for a universal time standard we can use wherever we are? This fundamentally cannot exist. Any "universal" system would drift for observers on different planets. Having different times in New York and New Delhi isn't the worst right now; doing a calendar look-up for the time on Mars isn't as neat. But given we won't have real-time communication, it isn't as big of a problem e…

I know that system clock drift can be bounded to milliseconds using an atomic clock or GPS receiver, but I didn't know whether we could overcome synchronization difficulties when speed-of-light differences are significant. I thought we could package some coordinate reference system, directional travel metadata (I'm traveling 0.000002c this way), and current system clock time, and synchronize that way. Fantasy use cas…

If you ever get the chance go to the Royal Observatory in Greenwich, which has a great explanation of the difficulties (and values) associated with timekeeping:

https://en.wikipedia.org/wiki/Royal_Observatory,_Greenwich#O...

Re: The Last POWER1 CPU on Mars Is Dead

#54

Post by gonehome » Mon, Feb 25, 2019, 9:36 PM UTC

JumpCrisscross wrote: post #9

yingw787 wrote: post #5

Might be O/T, but I found it really interesting how they mention "5,352 Martian solar days". Do we humans have plans in the pipeline for a universal time standard we can use wherever we are? Something that is a little more useful than "seconds since UNIX epoch" but something a little less terrestrial than UTC? Or is time going to be based wherever we land or travel (e.g. divide up Mars into time zones upon colonizati…

> Do we humans have plans in the pipeline for a universal time standard we can use wherever we are? This fundamentally cannot exist. Any "universal" system would drift for observers on different planets. Having different times in New York and New Delhi isn't the worst right now; doing a calendar look-up for the time on Mars isn't as neat. But given we won't have real-time communication, it isn't as big of a problem e…

Somewhat comically J.C.R Licklider's first proposal for what became the internet was titled the Intergalactic Computer Network. He later said he did this because when the project is inevitably downsized it would at least cover the earth.

Interplanetary internet designs and peering are interesting problems to think about though.

https://en.wikipedia.org/wiki/Intergalactic_Computer_Network

Re: The Last POWER1 CPU on Mars Is Dead

#55

Post by walls » Mon, Feb 25, 2019, 9:46 PM UTC

DannyB2 wrote: post #40

yingw787 wrote: post #5

Might be O/T, but I found it really interesting how they mention "5,352 Martian solar days". Do we humans have plans in the pipeline for a universal time standard we can use wherever we are? Something that is a little more useful than "seconds since UNIX epoch" but something a little less terrestrial than UTC? Or is time going to be based wherever we land or travel (e.g. divide up Mars into time zones upon colonizati…

According to relativity, you cannot get two different observers to agree on any kind of universal time, or even the order in which two events occurred. Observer A says that event X happened before Y. Observer B says that event Y happened before X. And they're both right from their POV.

Would it be theoretically possible to have a time based on the universes rate of expansion?

Re: The Last POWER1 CPU on Mars Is Dead

#56

Post by marzell » Mon, Feb 25, 2019, 9:49 PM UTC

yingw787 wrote: post #5

Might be O/T, but I found it really interesting how they mention "5,352 Martian solar days". Do we humans have plans in the pipeline for a universal time standard we can use wherever we are? Something that is a little more useful than "seconds since UNIX epoch" but something a little less terrestrial than UTC? Or is time going to be based wherever we land or travel (e.g. divide up Mars into time zones upon colonizati…

Planck Seconds since the Birth of Jesus. Infallible. But seriously, since time is relative, you can only provide it with a reference included. i.e. Planck Seconds since x event (big bang/whatever) from the perspective of y. Similar to the notion of objective velocity... any object is stationary or moving only in reference to something else. Although I think we can get around that if we could get accurate measurements of quantum foam and determine if those foam bits all have velocity relative to each other.

Re: The Last POWER1 CPU on Mars Is Dead

#57

Post by Symmetry » Mon, Feb 25, 2019, 9:54 PM UTC

yingw787 wrote: post #43

DannyB2 wrote: post #40

Earlier quoted context omitted.

According to relativity, you cannot get two different observers to agree on any kind of universal time, or even the order in which two events occurred. Observer A says that event X happened before Y. Observer B says that event Y happened before X. And they're both right from their POV.

Hmm...would this only be relevant on the scale of nano/picoseconds, or seconds or higher granularity, given a frequent synchronization schedule?

The further apart the observers are and the larger their relative velocities the larger the effect is. There's nothing to stop the differential from being years in extreme cases.

Re: The Last POWER1 CPU on Mars Is Dead

#58

Post by mdavidn » Mon, Feb 25, 2019, 9:58 PM UTC

hackbinary wrote: post #48

JumpCrisscross wrote: post #9

Earlier quoted context omitted.

> Do we humans have plans in the pipeline for a universal time standard we can use wherever we are? This fundamentally cannot exist. Any "universal" system would drift for observers on different planets. Having different times in New York and New Delhi isn't the worst right now; doing a calendar look-up for the time on Mars isn't as neat. But given we won't have real-time communication, it isn't as big of a problem e…

I thought a second was a SI base unit: (from Wikipedia) The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency {\displaystyle \Delta \nu _{\text{Cs}}} {\displaystyle \Delta \nu _{\text{Cs}}}, the unperturbed ground-state hyperfine transition frequency of the caesium-133 atom, to be 9192631770 when expressed in the unit Hz, which is equal to s−1.

Yes, but that frequency depends on the caesium-133's frame of reference. In a deep gravity well or at "high" speed, caesium-133 emits at a lower frequency relative to caesium-133 in deep space moving at "low" speed.

Re: The Last POWER1 CPU on Mars Is Dead

#59

Post by etaoins » Mon, Feb 25, 2019, 10:01 PM UTC

yingw787 wrote: post #33

JumpCrisscross wrote: post #9

Earlier quoted context omitted.

> Do we humans have plans in the pipeline for a universal time standard we can use wherever we are? This fundamentally cannot exist. Any "universal" system would drift for observers on different planets. Having different times in New York and New Delhi isn't the worst right now; doing a calendar look-up for the time on Mars isn't as neat. But given we won't have real-time communication, it isn't as big of a problem e…

I know that system clock drift can be bounded to milliseconds using an atomic clock or GPS receiver, but I didn't know whether we could overcome synchronization difficulties when speed-of-light differences are significant. I thought we could package some coordinate reference system, directional travel metadata (I'm traveling 0.000002c this way), and current system clock time, and synchronize that way. Fantasy use cas…

There is Barycentric Coordinate Time which is the time from a hypothetical clock at rest at the centre of mass of the Solar System. This is easier to calculate across spacecraft than an Earth-centric time would be. However, because it's outside of Earth's gravity well it ticks slightly faster than Earth time.

Re: The Last POWER1 CPU on Mars Is Dead

#60

Post by AngryData » Mon, Feb 25, 2019, 10:01 PM UTC

DannyB2 wrote: post #40

yingw787 wrote: post #5

Might be O/T, but I found it really interesting how they mention "5,352 Martian solar days". Do we humans have plans in the pipeline for a universal time standard we can use wherever we are? Something that is a little more useful than "seconds since UNIX epoch" but something a little less terrestrial than UTC? Or is time going to be based wherever we land or travel (e.g. divide up Mars into time zones upon colonizati…

According to relativity, you cannot get two different observers to agree on any kind of universal time, or even the order in which two events occurred. Observer A says that event X happened before Y. Observer B says that event Y happened before X. And they're both right from their POV.

Couldn't you just pick a pulsar or something, all agree to take their measurements from X distance from pulsar, and use that as the standard? It would be time + location, making your local time depending on the distance and number of pulses from the 0 starting pointing. As long as you kept account of the number of pulses as you moved through space, you could use that as a standard, and whenever you met up somewhere else in the universe, you could base your time based on their observed number of pulses.

Im not sure pulsars are actually that precise and predictable to not require regular adjustments to equate local times, but it would provide a standard anybody could utilize as long as they could keep an eye on it.

Of course it would break down if someone broke light speed, either with wormholes or some unknown technology, but as long as you are below lightspeed then there shouldn't be any problems.