Expanded UTC Page

Hello:

I have recently expanded the Coordinated Universal Time (UTC) page on my web
site (http://www.spacearchive.info/utc.htm).

I would appreciate it if you would carefully read the page for technical
accuracy and send me your comments.

Regards,

Brian W.

JRS: In article , dated Sun, 2 Apr 2006
21:43:21 remote, seen in news:sci.astro.amateur, Paul Schlyter
posted :

You seem to consider UTC, UT and GMT merely as synonyms for the same
time scale. That's not the case - you can consider them the same only
if DUTC (= UTC-UT) is insignificant. DUTC can be up to 0.9 seconds large,
positive or negative.

GMT is obsolete and can be ambiguous, and should therefore be avoided.

It is the legal time in the UK, AIUI, even though the time signals are
UTC. It is used in the English versions of EU documentation.

--
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The principles which keep the Earth rotating at 15 degrees per hour and
exactly 24 hours/360 degrees in total cannot change ,they cannot be
made obsolete nor can the Earth's terrestial longitudes and the
association between rotation at 15 degrees per hour be severed from
each other.

Too dumb to know that the pre-Copernican Equiation of Time principles
which fix natural noon to the 24 hour clock day transfer to its
heliocentric adaption to axial rotation at 15 degrees per hour and 24
hours/360 degrees in total,there is nothing easier ,more enjoyable or
more productive than the original Equation of Time principles which
straddle pre-Copernican and heliocentric astronomy.

Oh I know,you adhere to your calendrically driven clockwork system
based on an annual orbit of 3 years of 365 days and 1 year of 366 days
that keep the stars returning every night in 23 hours 56 min 04 sec.

I love the maneuvering of the 17th century guys in their attempt to
find longitude at sea using the celestial sphere/calendar system but I
would not build astronomical concepts on that homocentric standpoint.

Doctors ?,there are no doctors in astronomy or timekeeping but there
are plenty of phonies who are not capable of doing the neccessary
astronomical forensics to correct the 17th century misjudgements and
misconduct.A few here show potential for real astronomy,the rest are
either harmless astrophotographers or idiotic theorists who are
turning into a nuisance.

JRS: In article , dated Tue, 4 Apr 2006
06:42:58 remote, seen in news:sci.astro.amateur, Paul Schlyter
posted :
In article ,
Dr John Stockton wrote:
JRS: In article , dated Sun, 2 Apr 2006
21:43:21 remote, seen in news:sci.astro.amateur, Paul Schlyter
posted :

You seem to consider UTC, UT and GMT merely as synonyms for the same
time scale. That's not the case - you can consider them the same only
if DUTC (= UTC-UT) is insignificant. DUTC can be up to 0.9 seconds large,
positive or negative.

GMT is obsolete and can be ambiguous, and should therefore be avoided.

It is the legal time in the UK,

...and Pi was legally defined as exactly 3 in a US state some time in
the 1800's ..... g

Are you sure of your facts there? I've heard that they are commonly
exaggerated.

Let's forget about the legal stuff here, and instead focus on the
scientific and technically correct stuff.


AIUI, even though the time signals are UTC. It is used in the English
versions of EU documentation.

True, GMT is often used in everyday langugage, as well as in some
formal legal language. But lawyers and judges aren't scientists or
technicians.

And he wanted technically correct terms, not legal terms. The term
GMT does lack a precise definition: does it refer to UTC, UT0 or UT1?
Does the difference between them matter?

There's an important difference in that anyone reading UTC should allow
for the possibility of 23:59:60 (and of no 23:59:59), which does not
occur in GMT.

Almost all computer software uses a time scale which behaves digitally
like GMT and unlike UTC. In most computers the internal scale wanders, I
suspect, from linear by more than the difference between UT0 UT1 & UT2,
so the precise definition does not matter in practice.

If he describes only UTC, no problem. But if GMT is referred to, the
legal use should be described as well as the astronomical one. It was,
and is, used by many more people. astronomers should acknowledge that
they are a special case.

Over our history GMT has been used in different ways - sometimes even
starting at Greenwich Noon !!!!

Without worrying about the exact second, did the jump occur at UTC
1925.0, GMAT 1924.999999, or some other time?


--
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On Tue, 04 Apr 2006 06:42:58 GMT, (Paul Schlyter) wrote:

...and Pi was legally defined as exactly 3 in a US state some time in
the 1800's ..... g

Point taken, but this is actually not true. An ignorant legislator made
such a proposal, but it never carried. No such law ever existed.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Do you freaks ever notice that 86 400 leap seconds are added after
every 1460 days and further adjustments are added every few centuries
to keep you calendrically driven clockwork system ticking over.

The genuises who figured out local leap second adjustments can only
highlight their stupidity even though they aim for the opposite.

Too stupid to know why axial rotation to the stellar background in 23
hours 56 min 04 sec is not an intelligent way to consider axial
rotation as an isolated motion for it creates these stupid sidereal
notions for the Earth's motions.

JRS: In article , dated Wed, 5 Apr 2006
06:43:07 remote, seen in news:sci.astro.amateur, Paul Schlyter
posted :
In article ,
Dr John Stockton wrote:

There's an important difference in that anyone reading UTC should allow
for the possibility of 23:59:60 (and of no 23:59:59), which does not
occur in GMT.

Depends on how you define GMT. Nowadays GMT is used as a synonym for UTC, and
if you use such a definition, then 23:59:60 appears in GMT as well, just like
in any other time zone: EST, CET, .... etc.

Some may consider it as a synonym; others only as an approximation.
Lest you be misinterpreted, 23:59:60 itself only occurs in the central
time zone (i.e. the one containing Greenwich) and in anywhere in the
next zone West that has civil time based on UTC (rather than GMT) and
has Summer Time. And in UTC.


Doesn't the legal use of GMT ignore leap seconds?

Not really; in GMT, they do not exist, so cannot be ignored.


Btw does the legal use of time ever require a precision of 1 second or
better?

I doubt whether the formal legal use admits of any uncertainty in time.

The London Congestion Charge, for example, needs exact defined timing;
and it also needs a definition of which parts of a vehicle must be in
the Zone for the vehicle to be charged.


Without worrying about the exact second, did the jump occur at UTC
1925.0, GMAT 1924.999999, or some other time?

It certainly didn't occur at "UTC 1925.0" (whatever that means...) since
the UTC time scale wasn't officially introduced until 1972, and wasn't
even used experimentally until around 1957.

Proleptically UTC 1925.0. One might alternatively ask at which GMT time
were well-behaved GMT and astronomers' GMT first equal.


--
© John Stockton, Surrey, UK. Turnpike v4.00 MIME. ©
Web URL:http://www.merlyn.demon.co.uk/ - w. FAQish topics, links, acronyms
PAS EXE etc : URL:http://www.merlyn.demon.co.uk/programs/ - see 00index.htm
Dates - miscdate.htm moredate.htm js-dates.htm pas-time.htm critdate.htm etc.

On Mon, 3 Apr 2006 19:57:38 +0100, Dr John Stockton
wrote, in part:
JRS: In article , dated Sun, 2 Apr 2006
21:43:21 remote, seen in news:sci.astro.amateur, Paul Schlyter
posted :

GMT is obsolete and can be ambiguous, and should therefore be avoided.

It is the legal time in the UK, AIUI, even though the time signals are
UTC. It is used in the English versions of EU documentation.

I thought they switched over to French time in order to save energy.

John Savard
http://www.quadibloc.com/index.html
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On Tue, 4 Apr 2006 22:20:36 +0100, Dr John Stockton
wrote, in part:
JRS: In article , dated Tue, 4 Apr 2006
06:42:58 remote, seen in news:sci.astro.amateur, Paul Schlyter
posted :

...and Pi was legally defined as exactly 3 in a US state some time in
the 1800's ..... g

Are you sure of your facts there? I've heard that they are commonly
exaggerated.

What actually happened was that the Indiana legislature *almost* passed
legislation acknowledging the truth of a circle-squarer's value for Pi,
in order to avoid paying royalties when they updated their school
textbooks to incorporate this new "discovery".

John Savard
http://www.quadibloc.com/index.html
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JRS: In article , dated Fri, 7 Apr 2006
10:13:23 remote, seen in news:sci.astro.amateur, Paul Schlyter
posted :
In article ,
Dr John Stockton wrote:
JRS: In article , dated Wed, 5 Apr 2006
06:43:07 remote, seen in news:sci.astro.amateur, Paul Schlyter
posted :

Doesn't the legal use of GMT ignore leap seconds?

Not really; in GMT, they do not exist, so cannot be ignored.

Since the current definition of GMT is so fuzzy, one cannot conclude
whether GMT has leap seconds or not.

Before, let us say, 1900, there was no thought of leap seconds. GMT was
made the legal time in the UK before 1900. Therefore, GMT was created
without leap seconds. Parliament has not legislated any change;
therefore, GMT still has no leap seconds.

Btw does the legal use of time ever require a precision of 1 second or
better?

I doubt whether the formal legal use admits of any uncertainty in time.

The London Congestion Charge, for example, needs exact defined timing;
and it also needs a definition of which parts of a vehicle must be in
the Zone for the vehicle to be charged.

The policemen out in the field will be forced to handle these
uncertainties though.

For the purpose, they will not, because AIUI they do not exist.

They'll probably add some safety margin, so that
they are really sure the time is before, or after, some legal limit
before bringing someone to court.

No, modern technology is used. If an image captured within the relevant
operating hours shows a vehicle entering or leaving the zone, the charge
is payable. The timing can easily be made to contribute no significant
uncertainty. There's no timing difficulty with those found in the zone
but not entering or leaving within operating hours.


Without worrying about the exact second, did the jump occur at UTC
1925.0, GMAT 1924.999999, or some other time?

It certainly didn't occur at "UTC 1925.0" (whatever that means...) since
the UTC time scale wasn't officially introduced until 1972, and wasn't
even used experimentally until around 1957.

Proleptically UTC 1925.0. One might alternatively ask at which GMT time
were well-behaved GMT and astronomers' GMT first equal.

Perhaps you can supply us with a full list of leap seconds back to 1925 or
perhaps even earlier in this proleptic UTC ? g

Well, I did start with "Without worrying about the exact second,".

You're still not answering the question of when the 12-hour change in
Astronomers' Greenwich Mean Time occurred - perhaps that would best be
done by stating, in Astronomers' Time, the omitted interval. I'm only
guessing when I suppose that GMAT 1924-12-31 started at midday in
Greenwich and finished at midnight.

All I know about the timing of the change in the RN day is that the
edict was issued before Trafalgar, but was apparently not implemented at
Trafalgar.

--
© John Stockton, Surrey, UK. Turnpike v4.00 MIME. ©
Web URL:http://www.merlyn.demon.co.uk/ - w. FAQish topics, links, acronyms
PAS EXE etc : URL:http://www.merlyn.demon.co.uk/programs/ - see 00index.htm
Dates - miscdate.htm moredate.htm js-dates.htm pas-time.htm critdate.htm etc.