I am somewhat incredulous at the notion that the Julian measurement of time is accurate and convenient enough to satisfy the needs of many outside the civilian community, namely those involved with physics, astronomy, military technology, etc.
A Google search, although feebely initiated, turned up squat.
Logic would lead me to believe that a metric time scale would be better suited to a higher degree of accuracy, unconstrained to convention, and easily converted back to our bad Julian selves.
Yet all I can find regarding conversions are linked back to seconds, minutes, hours, etc. I realize there are milliseconds and the like. What baffels me is that a base unit wouldn’t exist besides the conventional “second”.
No, the base unit of time is the second. It’s a perfectly reasonalbe measurement.
One thing that may be throwing you off are the larger time units of minutes and hours and days and years. These time units are strictly derivative and today are defined in terms of seconds (as opposed to the other way around). The second is defined independent of the Earth’s rotation as the rate today since the rotation rate of the earth isn’t consistent. Here is the definition of a second from NIST:
The second is a metric unit, one of the seven fundamental units that form the basis of the whole SI (Système Internationale) units system. (See here - they are the metre, the kilogram, the second, the ampere, the kelvin, the mole and the candela).
So, any “derived” SI unit (eg the joule) can be expressed in terms of those seven base units (eg, J = Nm = m[sup]2[/sup]kgs[sup]-2[/sup]).
I don’t think any 10-based system of marking time is used.
The length of the day is tied to the rotation of the earth and that period can theoretically be divided up into any number of subdividions.
I think in all scientific work the second is used, irrespective of the units of distance mass etc., so it is the time unit in all cases. Engineers used to use minutes in some cases but I’ve been retired for 22 years now so I don’t know it that is still the case. I suspect not.
The second is now defined by the natural vibration frequency of certain atoms in atomic clocks. Because of vagaries in the rotation of the earth those clocks have to be reset by adding or maybe removing a second now and then. However, that doesn’t change the length of the second. It merely changes the number of seconds in the day on which the resetting is done.
The measurement of time is a complicated subject and I remember a heated argument on either this board or another on the subject.
I beg to differ with you. While the second has been redefined using atomic vibration, it was orginally defined as 1/86400 of a day. It was adopted by the metric system, but was not designed as part of the metric system See cite:
Try to think of it in terms that the modern “metric” (actually, SI) “second” is not the same thing as 1/86400th of your day, but a defined SI unit that just happens to be damn close to it and is named the same.
Right now even the meter is defined in function of the second and c (the speed of light constant). Strictly, in SI all time measurements are in seconds. Velocity in SI is meters/second, NOT Kilometers/hour. The Big Bang was something like 10[sup]18[/sup] seconds ago, not however many billyuns and billyuns of years.
SI however does not preclude us from going ahead and use manageable units for a particular context.
I’ll repeat again - there is no reason why a “metric” unit has to be decimal in nature. The second “just is” the base unit of time, the same as the kilogram “just is” the base unit of mass (the kilogram admittedly was chosen to be approximately equal to the mass of a cubic decimetre of water, so there is a decimal rationale behind it). Time is a bit different because the Earth doesn’t cooperate by , say, revolving on its own axis 100 times in the time it takes to orbit the sun, with the Moon orbiting the earth 10 times in the same duration.
Not sure who you were disagreeing with - could have been me as I perhaps wasn’t clear. The second is a metric unit, but you’re right of course that it wasn’t designed as one - it predates the SI system by centuries. What I meant was that the SI system was designed around the second, so there is no need for any “other” form of measurement for scientists to use.
In more modern times, we have the swatch “internet time” promotion.
(Not to be confused with other usage of “internet time”, a term which appears, at least in some circles and in the RFE’s to refer to the “seconds since 1970” thing I’ve always called “bintime”, “systime” or “seconds since epoch” - http://www.ce.ufl.edu/~chiep/metric.html )
And I meant RFC’s - proofread! A bunch of posts arrived while I was posting the first time, too, I see, in particular another note about the French Revolutionary system.
I think you’re confusing precise measurement of time with tracking of days. I’m not saying the two are unrelated but God/accident of physics/great post stealing hamster in the sky didn’t see fit to give our planet a rotation/revolution ratio that works out to a nice non-prime with ten as one of its factors. You might also note that we haven’t used the Julian calender since Pope Gregory fixed Easter.
Padeye’s nailed down the problem: However we may define a “second,” our fundamental units of time are really the day and the year, and God has seen fit to set the number of days in a year at approximately 365.25
While my question has been answered, I apologize if I was initially vague.
Simply put, I’m surprised that a recently defined, accurately measurable length of time has not become the norm for the scientific and other communities.
For example, the vibration of quartz has been used as a reasonable standard but it’s always tied back to vibrations per second.
Why not have the duration of a single vibration as a defined term and measure events in that length?
Why not something akin to "This event lasted for 20 vibrations (wiggles) of a quartz crystal, or 20 “quibbles”?
Why not have the duration of a single vibration as a defined term and measure events in that length?
Because there’s nothing to be gained from doing so. We have a universally accepted, well-understood way to measure time already. What’s the point in trying to change it?
Because that is introducing more complication, for no gain.
We know intuitively how long a second is, and a second has been defined unambiguously in terms of atomic vibrations. (9,192,631,770 cycles of vibration in a cesium atom, as noted).
So quoting time intervals in seconds is just as unambiguous as quoteing them in “quibbles” (or whatever), and has the added benefit that everybody knows how long a second is.
You may find it interesting that the meter is defined in terms of the second, and that the gram is defined in terms of the meter. If we redefined the time unit for SI, we’d probably redefine the distance and mass units as well.