[seanc]

From the GNU coretutils doc [1]:

Our units of temporal measurement, from seconds on up to months, are so complicated, asymmetrical and disjunctive so as to make coherent mental reckoning in time all but impossible. Indeed, had some tyrannical god contrived to enslave our minds to time, to make it all but impossible for us to escape subjection to sodden routines and unpleasant surprises, he could hardly have done better than handing down our present system. It is like a set of trapezoidal building blocks, with no vertical or horizontal surfaces, like a language in which the simplest thought demands ornate constructions, useless particles and lengthy circumlocutions. Unlike the more successful patterns of language and science, which enable us to face experience boldly or at least level-headedly, our system of temporal calculation silently and persistently encourages our terror of time.

… It is as though architects had to measure length in feet, width in meters and height in ells; as though basic instruction manuals demanded a knowledge of five different languages. It is no wonder then that we often look into our own immediate past or future, last Tuesday or a week from Sunday, with feelings of helpless confusion. …

—Robert Grudin, Time and the Art of Living.

[1] https://www.gnu.org/software/coreutils/manual/html_node/Date...

[photochemsyn]

For even more fun, take a look at this excellent post on GPS, and in particular, the time problem:

https://ciechanow.ski/gps/#time

> "When it comes to the flow of time on those satellites, there are two important aspects related to Einstein’s theories of relativity. Special relativity states that a fast moving object experiences time dilation – its clocks slow down relative to a stationary observer. The lower the altitude the faster the satellite’s velocity and the bigger the time slowdown due to this effect. On the flip side, general relativity states that clocks run faster in lower gravitational field, so the higher the altitude, the bigger the speedup is."

> "Those effects are not even and depending on altitude one or the other dominates. In the demonstration below you can witness how the altitude of a satellite affects the dilation of time relative to Earth..."

There's also a nice if complex explanation of why your GPS receiever needs four satellite emitters to calculate the time bias of its clock.

[moring]

> Special relativity states that a fast moving object experiences time dilation – its clocks slow down relative to a stationary observer.

For more fun: A less known fact is that SR also states that from the POV of the satellite, the satellite is a stationary observer and the guy on earth is fast moving, therefore that observer's clock slows down relative to the satellite.

Yes, that's right: Each of them sees the other one's clock as slower.

IIRC It takes the fact that the satellite moves in an orbit, not in a straight line, to resolve which one is actually "slower" because up until then, the word "slower" isn't really meaningful at all.

[seanc]

What a find! That's a top notch GPS explanation; simple, detailed and great visualization of complex stuff. Thanks!

[alvarlagerlof]

Check out the rest of the site

[dwenzek]

Thank you for the link! I love this kind of comprehensive blog posts that open a door to a new world. It's worth the time to read those.