39

POSIX time doesn't include leap seconds, and is not implemented the same way in every UNIX, so it routinely gets inconsistent for several seconds every couple of years. It is not a high-precision time scale, and there is little point correcting it for relativistic effects which are smaller than it can represent. GPS has to be corrected --- in particular, ...


30

No. Computer clocks are inaccurate. They rely on constant corrections to maintain the correct time. Since their inaccuracy is much bigger than the time speed difference between earth and the ISS, it really doesn't matter.


24

It doesn’t yet matter for most practical purposes. The slowdown from faster motion and speedup from a weaker gravitational field partly cancel out, and the net effect is that time on the ISS is only 0.0000000014% slower than time on Earth, so in its whole 22-year history it has lost about one hundredth of a second.


21

The approach taken by Voyager Golden Record is through use of pulsars. Unlike the insane exponents needed to utilize microscopic physical phenomena or planck time, pulsars operate on ~1 second timescale, which makes them quite convenient. A map specifiying location of Earth in relation to a number of pulsars identified through ratios between their ...


8

Our basic unit of time, the second, is officially defined in terms of physical phenomena, so our messages have to get that across. If the aliens and ourselves have a compatible understanding of mathematics, chemistry and physics, which we hope are universal, it's possible to construct a message which builds up the necessary vocabulary from first principles....


5

Computers on the ISS do not rely on UNIX/POSIX time, they rely on GPS time. Broadcast time is the time broadcast from ISS computers that is intended to be indicative of current time. The broadcast time message is with respect to the GPS time scale, not the Universal Time Coordinated (UTC) time scale. The time is accurate to ±1 s: Due to various reasons, ...


4

You can see this answer for the formulae. We would expect that Voyager 1's local time is faster than Earth time by about one part in one hundred million. I don't think that the Voyager oscillator is stable enough to measure that small of a difference. So we can't directly answer "is this true". However it would be a mind-blowing discovery throwing our most ...


4

One value for time is common for all species, the planck time. It depends only on mathemathical/physical concepts. But you will have to explain to them the powers of 10 as well because else you would have to draw something like 8*10^60 ticks on the calendar. (Age of the universe is 4.32 × 10^17s and planck time is 5.4 × 10^-44s)


3

One option nobody else mentioned is cosmic microwave background. If you can encode the current temperature of the universe in a way the receiving aliens understand, they will either have a record of its past development or at least a pretty good model. CMB is the same everywhere in the universe and since the fluctuations are very small and it's relatively ...


3

The only way you could travel at the speed of light, not assuming highly theoretical faster than light (FTL) travel which actually bends spacetime to shorten the distance between two points (highly simplifying here), is if you transfer consciousness as information about it into a distant neural network or any other physical medium later supporting its ...


3

I think you've misunderstood something; there's no generally accepted model for light-speed-or-faster travel, and so there's no generally accepted model for the passage of time in such a mode. There is a well-known time dilation effect for speeds near, but below, the speed of light ("relativistic speeds"); a complete explanation is both very long and beyond ...


3

Once you exceed lightspeed, external time would run backwards instead of forwards. This is where it all falls down. You're applying the laws of relativity to FTL travel, but the laws of relativity, specifically the Lorentz factors, don't make sense for velocities above the speed of light, $c$. Just look at the mathematics - the Lorentz Factor is given by ...


2

The distance (and time) shrink from the viewpoint of the fast-moving object, but not from the viewpoint of a stationary observer.


1

Time-keeping is a particularly interesting subject for me. There are multiple ways you can communicate a date, and some sort of system of keeping time to reference that to. Some constants in nature can be used to keep time outside our solar system where the relative motion of our planet to our sun become irrelevant. The challenge here is to help this life ...


1

Well, the speed of light is never going to change. That being the case, one method could be to use light years as a means to calculate time. 'x light years from now' could be the way to specify a relative date. You could also include how much time a second is (via a gap in the audio) and specify that 60 seconds make a minute and 60 minutes make an hour and ...


1

Can the Oberth effect cause space-time distortions? No, but the mass(es) used for the maneuver might. Note that the velocity of the spacecraft performing the maneuver might cause a slowing of it's time relative to an observer, but: At anything less than extreme speeds (a significant percent of the speed of light) it would be almost immeasurable. As far ...


1

You are a lot further down a gravity well when you are in the vicinity of a black hole. That alone can explain time dilation factors without even considering the extreme velocity that object must have in order to remain in orbit. Both factors help 'slow' the time.


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