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 Post subject: OT: Leaping Forward
PostPosted: Tue Jun 30, 2015 5:06 pm 
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Just so y'all know, today is the longest day of the year. When the time reaches 23:59:59 UTC it will advance to 23:59:60 UTC and then go back to 00:00:00 UTC. This is because a leap second has to be applied to get clock time back in sync with sidereal time. So enjoy the extra sleep! :lol:

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Last edited by BigDumbDinosaur on Sun Jul 05, 2015 5:43 pm, edited 3 times in total.

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 Post subject: Re: Leaping Forward
PostPosted: Tue Jun 30, 2015 5:12 pm 
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And if the internet works in the morning, and civilisation hasn't collapsed, we'll chat on the other side.


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 Post subject: Re: Leaping Forward
PostPosted: Tue Jun 30, 2015 6:42 pm 
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And what do you do if you are sitting on the Greenwich Meridian or International Date Line?


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 Post subject: Re: Leaping Forward
PostPosted: Tue Jun 30, 2015 6:45 pm 
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You need to shift to the left a few hundred yards at midnight!


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 Post subject: Re: Leaping Forward
PostPosted: Tue Jun 30, 2015 6:51 pm 
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BigEd wrote:
You need to shift to the left a few hundred yards at midnight!

Wouldn't moving over a couple of feet be sufficient? :lol:

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 Post subject: Re: Leaping Forward
PostPosted: Tue Jun 30, 2015 6:54 pm 
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Well, I did the calculation, and surprised myself. The planet, it turns out, is pretty big. One second is a big leap!


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 Post subject: Re: Leaping Forward
PostPosted: Tue Jun 30, 2015 7:10 pm 
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BigEd wrote:
Well, I did the calculation, and surprised myself. The planet, it turns out, is pretty big. One second is a big leap!

It figures that Ed would have worked this out, since he's in Merry Olde England, which is bisected (sort of) by the Prime Meridian. :D Are you right on the meridian perchance?

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 Post subject: Re: Leaping Forward
PostPosted: Tue Jun 30, 2015 8:50 pm 
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No, I'm in the Western Hemisphere. Not too far away there's a public clock with three hands - an hour hand, a minute hand for local time, and a minute hand for Greenwich time (railway time)
http://wwp.greenwichmeantime.com/info/bristol-time.htm
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 Post subject: Re: Leaping Forward
PostPosted: Tue Jun 30, 2015 11:06 pm 
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BigEd wrote:
No, I'm in the Western Hemisphere. Not too far away there's a public clock with three hands - an hour hand, a minute hand for local time, and a minute hand for Greenwich time (railway time)

Ah yes, I recall reading about that clock. What would be funny would be installing something like it in a pub, with one minute hand set to the correct time and the other set to "bar time." That would definitely confuse the more inebriated souls.

The concept of the Bristol clock sort of mirrors common practice in the USA prior to the advent of Standard Time. Large railroad depots, especially in Chicago and New York, would have numerous clocks that were all synchronized to different railway time systems, since major railroads would synchronize their clocks to the time in a particular city. It had to have been a real nightmare for dispatchers who were trying to keep the trains on schedule, and no doubt was the impetus behind the adoption of Standard Time. Sunday November 18, 1883 is known in North American railroad history as the "day of two noons," as it was on that day that all Canadian and US railroads switched to Standard Time.

One of the interesting side-effects of the switch to Standard Time was a reduction in wrecks due to collisions. At the time, almost all North American railroads controlled track occupancy with timetable rules—block signaling was uncommon in those days. The problem, of course, was that prior to the adoption of Standard Time, 5 PM on the New York Central, which used New York City time, was not the same as 5 PM on the Pennsylvania Railroad, whose clocks were synced to the Allegheny Observatory in Pittsburgh. If, for example, a NYC train was to share or cross a track on which a Pennsy train was also running, keeping the trains separated was prone to error, especially if one of the trains wasn't on schedule. Given that many of those trains were run at high speeds due to the great distances, a scheduling error could result in a disastrous wreck—and there were plenty of them in those days. Once the railroads switched to Standard Time, scheduling meets was much more foolproof, and a lot fewer collisions took place.

Interestingly enough, the infamous wreck on the Illinois Central Railroad in which Casey Jones was killed was ultimately the result of scheduling and Jones' desire to keep his train on time. He rounded a curve at Vaughn, Mississippi at an estimated 80 miles per hour and rear-ended a freight (goods) train that was in the process of pulling into a siding to clear the mainline. The freight train was behind schedule and Jones arrived at Vaughn almost exactly on schedule. As he had not received an order at his previous stop advising him that the freight was behind schedule, he had no reason to reduce speed approaching Vaughn.

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Last edited by BigDumbDinosaur on Mon Sep 18, 2023 4:47 am, edited 1 time in total.

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 Post subject: Re: Leaping Forward
PostPosted: Wed Jul 01, 2015 5:36 am 
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Goodness me, time is difficult, but that's no good reason to be colliding trains at great speed! Thanks for the interesting info. There's a Babbage anecdote about a near-miss on the Great Western line, caused by the assumption (not his) that on a Sunday it would be safe to use the wrong line:
Quote:
I accordingly availed myself of the day on which, at that
time, scarcely a single train or engine would be in motion
upon it.

Upon one of these Sundays, which were, in fact, the only
really safe days, I had proposed to investigate the effect of
considerable additional weight. With this object, I had
ordered three waggons laden with thirty tons of iron to be
attached to my experimental carriage.

On my arrival at the terminus a few minutes before the
time appointed, my aide-de-camp informed me that we were
to travel on the north line. As this was an invasion of the
usual regulations, I inquired very minutely into the authority
on which it rested. Being satisfied on this point, I desired
him to order my train out immediately. He returned shortly
with the news that the fireman had neglected his duty, but that
the engine would be ready in less than a quarter of an hour.

A messenger arrived soon after to inform me that the
obstructions had been removed, and that I could now pass
upon the south, which was the proper line.

I was looking at the departure of the only Sunday train,
and conversing with the officer, who took much pains to
assure me that there was no danger on whichever line we
might travel; because, he observed, when that train had
departed, there can be no engine except our own on either line
until five o'clock in the evening.

Whilst we were conversing together, my ear, which had
become peculiarly sensitive to the distant sound of an engine,
told me that one was approaching. I mentioned it to my
railway official: he did not hear it, and said, "Sir, it is
impossible." — "Whether it is possible or impossible," I said, "an
engine is coming, and in a few minutes we shall see its steam."
The sound soon became evident to both, and our eyes were
anxiously directed to the expected quarter. The white cloud
of steam now faintly appeared in the distance; I soon
perceived the line it occupied, and then turned to watch my
companion's countenance. In a few moments more I saw it
slightly change, and he said, "it is, indeed, on the north
line."

Knowing that it would stop at the engine house, I ran as
fast I could to that spot. I found a single engine, from
which Brunel, covered with smoke and blacks, had just
descended. We shook hands, and I inquired what brought my
friend here in such a plight. Brunel told me that he had
posted from Bristol, to meet the only train at the furthest
point of the rail then open, but had missed it. "Fortunately,"
he said, I found this engine with its fire up, so I ordered it
out, and have driven it the whole way up at the rate of fifty
miles an hour."

I then told him that but for the merest accident I should
have met him on the same line at the rate of forty miles...
- Chapter XXV, Railways. "ESCAPES MEETING BRUNEL."

As for our leap second, my own laptop crashed - I'd hoped to record some successive timestamps. Amazon also had trouble, which they passed on to clients such as Instagram, Netflix, Pinterest. But this seems to have been a routing problem, not a leap second one.

Edit: but my fileserver did at least report the leap:
Code:
Clock: inserting leap second 23:59:60 UTC


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 Post subject: Re: Leaping Forward
PostPosted: Wed Jul 01, 2015 3:49 pm 
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BigEd wrote:
Goodness me, time is difficult, but that's no good reason to be colliding trains at great speed! Thanks for the interesting info. There's a Babbage anecdote about a near-miss on the Great Western line, caused by the assumption (not his) that on a Sunday it would be safe to use the wrong line...Chapter XXV, Railways. "ESCAPES MEETING BRUNEL."

The interesting aspect of Babbage's story is that it was about a scheduling error on a north-south line, on which time reckoning errors would be inherently less likely than on an east-west route. The latter routes, of course, are much more prevalent in much of North America, and even today, long stretches of such track are not signaled and hence vulnerable to "cornfield meets" of the sort that almost happened to Babbage's train. Naturally, modern dispatching practices and the availability of two-way radio have greatly reduced, but not eliminated, the risk of a cornfield meet.

BTW, your post about Babbage's near-miss highlights the fact that although many associate him with the early development of the computer, he was also involved with railway engineering and in fact, was the apparent inventor of what we would today call a dynamometer car. I say "apparent" because the written record on that isn't 100 percent clear, although Babbage's notes concerning track and locomotive testing seem to support the notion that he developed the ancestors of both the modern dynamometer car and track geometry car, the latter very important in the maintenance of high speed rail lines.

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Edit: but my fileserver did at least report the leap:
Code:
Clock: inserting leap second 23:59:60 UTC

My Linux box reported that as well, but the old SCO OpenServer box (now in its 15th year of operation!) said nary a peep. However, it is in sync with the Linux box, so it must have consulted NTP some time after midnight.

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 Post subject: Re: Leaping Forward
PostPosted: Wed Jul 01, 2015 4:00 pm 
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BigDumbDinosaur wrote:
BigEd wrote:
Goodness me, time is difficult, but that's no good reason to be colliding trains at great speed! Thanks for the interesting info. There's a Babbage anecdote about a near-miss on the Great Western line, caused by the assumption (not his) that on a Sunday it would be safe to use the wrong line...Chapter XXV, Railways. "ESCAPES MEETING BRUNEL."

The interesting aspect of Babbage's story is that it was about a scheduling error on a north-south line, on which time reckoning errors would be inherently less likely than on an east-west route.


Actually, no, the Great Western line is the major East West line in the southern UK. The north track would be inbound to London (where Babbage was) and the south track would be outbound to Bristol and (eventually) beyond - UK trains drive on the left. (We generally have paired tracks, which perhaps we can better afford because distances are not so great.)


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 Post subject: Re: Leaping Forward
PostPosted: Wed Jul 01, 2015 5:21 pm 
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BigEd wrote:
BigDumbDinosaur wrote:
BigEd wrote:
Goodness me, time is difficult, but that's no good reason to be colliding trains at great speed! Thanks for the interesting info. There's a Babbage anecdote about a near-miss on the Great Western line, caused by the assumption (not his) that on a Sunday it would be safe to use the wrong line...Chapter XXV, Railways. "ESCAPES MEETING BRUNEL."

The interesting aspect of Babbage's story is that it was about a scheduling error on a north-south line, on which time reckoning errors would be inherently less likely than on an east-west route.

Actually, no, the Great Western line is the major East West line in the southern UK. The north track would be inbound to London (where Babbage was) and the south track would be outbound to Bristol and (eventually) beyond...

Oops! Missed the part about it being the Great Western line! :oops:

Quote:
- UK trains drive on the left.

We have one line in the USA that also operates on the left: the old Chicago & Northwestern (C&NW) line, which was subsumed into the Union Pacific Railroad in the 1990s, but still uses left-hand running. Supposedly a 19th century British railway civil engineer was hired to survey and lay out the C&NW line, and he naturally adopted British practice. Another theory was that the principle American civil engineer on the project was left-handed...who knows for sure! :?:

Quote:
(We generally have paired tracks, which perhaps we can better afford because distances are not so great.)

It's amazing how much American and Canadian mainline right-of-way is single-tracked. A single-track Union Pacific mainline runs near to my home, and Amtrak operates bi-directional high speed (110 MPH) service on it. It is fully signaled, so that at least goes a long way toward avoiding cornfield meets.

As you say, distances in the UK aren't what they are here, so construction cost is a big factor. It was recently estimated that it costs around 1 million USD to build a mile of mainline track suitable for high speed operation (high speed by North American standards). Multiply that by the tens of thousands of mainline track miles and it quickly becomes clear why multiple tracks aren't widespread.

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 Post subject: Re: Leaping Forward
PostPosted: Wed Jul 01, 2015 7:21 pm 
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In Switzerland trains drive on the left as well :wink:


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 Post subject: Re: Leaping Forward
PostPosted: Wed Jul 01, 2015 7:46 pm 
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cbscpe wrote:
In Switzerland trains drive on the left as well :wink:

On which side of the roads do you drive?

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