Re: JMT Clock and Molad Calculator

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Re: JMT Clock and Molad Calculator

Moongazer
Hello Karl Palmen and Calendar people,
 
Karl writes:
 
> I'd like to be able to switch between JMT Clock and Night/Day clock on one page.
 
There are reasons for keeping them on separate pages, one being that the JMT Clock is primarily of use to those with an interest in the Jewish Calendar, whereas the Night/Day Clock has a much broader appeal.
 
However, I have changed the destination on one of the hyperlinks so that on each one's page there is now a direct link to the other. On the JMT Clock page, click the link "Civil Time," and on the Night/Day Clock page, click the link "JMT Clock." Both links are in the explanatory text alongside the clock to its right. You can have each clock page open in its own browser tab and then tab from one to the other. Because the structure containing the clock is identical in both pages, if both pages are scrolled to the top, and you tab back and forth like that, quickly, it will create a visual effect like that of a blink-comparitor, as if the one clock is alternating in type. Try it.
 
> The Molad Calculator needs to show the month and year
 
It does that now, but, at present, it only shows two (pre-set) moladot : Press the Tohu button for the calendar's epochal molad, and, if you press the "Current" button, it shows the molad of Heshvan, 5778. That is just a temporary measure because I haven't written the calendar code yet, but in both cases, it shows the year and month name.
 
> I expect Moongazer is working on this.
 
Quite so, but I anticipate that it will take some time. I have written all the essential code many years ago in PowerBasic, so I just need to port it to Javascript. Even so, I expect it to take a while. BTW, my old Basic calendar code is now publicly available on my Jewish calendar website, where it is the first item in the downloads section. The routines are copiously commented and include much explanatory material. Even if you have no use for the code, it is worth a look at least at the custom modulo function included there and the comments on it. Here is the link:
 
tiny.cc/jewishcalendar
 
>>>>
Also the ability to go forward of back by a fixed number of months would be great, especially to show the small change of 23 parts (1 minute 16 2/3 seconds) that occurs after 49 months or the minimum change of 1 part that occurs after 3383 months.
<<<<
 
I was intrigued by this information, so I did the maths and found that, after a period of 49 months, the molad advances by 4d, 23h, 1057p (i.e. 23 parts short of 5 days). After 3383 months, it advances by 4d, 23h, 1079p (i.e. 1 part short of 5 days). Once you take into account the advance of nearly 5 days, plus the fact that neither of those two intervals is a multiple of Metonic cycles, these two phenomena did not animate me nearly as much as they did at first.
 
However, there is a another such phenomenon that I think is worthy of attention. It is much more striking and much better known. Its renown is due to the fact that it has led several famous Jewish authorities astray. After 247 years (13 Metonic cycles), the molad advances by 6d, 23h, 175p (i.e. 905 parts short of a whole week), so, effectively, the molad value regresses by 905 parts. This actually creates a tendency for the calendar to repeat itself after 247 years. That period became known as the Iggul (cycle) of Rabbi Nachshon (who served as Gaon from 881 to 889). He discovered this tendency and mistook it for a perfect repetition. Another famous authority, Jacob ben Asher ("the Rosh"), circa 1300, was also led astray by this "discovery" of Rabbi Nachshon.
 
As presently designed, the available navigation intervals in my molad calculator are: 1 month, 1 year, and 1, 13, 100 and 1000M (Metonic cycles). The reason I included 13M is precisely in order to let people explore this so-called cycle of Rabbi Nachshon and investigate how consistent it is. If people would like to also explore other similar phenomena like the two mentioned here by Karl and would find it convenient to set their own interval of any multiple of months for that purpose, I could possibly redesign the calculator to allow that. It will make the program logic more complex, but it would be worth doing it if people think that would be useful.
 
> It's probably the Nabble interface you are using which is messing up URLs.
 
I'm now posting by email via the listserv, so let's see if that makes a difference:
Here are the URLs again (though with the h t t p prefix stripped from the shortened URLs)
 
Night/Day Clock:   Reachable via   tiny.cc/night-day-clock   or:

JMT Clock and Molad Calculator:   Reachable via    tiny.cc/jmt-clock   or:
http://moongazer.x10.mx/website/march/jmt-clock/
 
 
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Re: [SUSPICIOUS MESSAGE] Re: JMT Clock and Molad Calculator

Karl Palmen

Dear Moongazer and Calendar People

 

Thank you Moongazer for your reply.

 

I’ll reply just to

I was intrigued by this information, so I did the maths and found that, after a period of 49 months, the molad advances by 4d, 23h, 1057p (i.e. 23 parts short of 5 days). After 3383 months, it advances by 4d, 23h, 1079p (i.e. 1 part short of 5 days). Once you take into account the advance of nearly 5 days, plus the fact that neither of those two intervals is a multiple of Metonic cycles, these two phenomena did not animate me nearly as much as they did at first.

 

However, there is a another such phenomenon that I think is worthy of attention. It is much more striking and much better known. Its renown is due to the fact that it has led several famous Jewish authorities astray. After 247 years (13 Metonic cycles), the molad advances by 6d, 23h, 175p (i.e. 905 parts short of a whole week), so, effectively, the molad value regresses by 905 parts. This actually creates a tendency for the calendar to repeat itself after 247 years. That period became known as the Iggul (cycle) of Rabbi Nachshon (who served as Gaon from 881 to 889). He discovered this tendency and mistook it for a perfect repetition. Another famous authority, Jacob ben Asher ("the Rosh"), circa 1300, was also led astray by this "discovery" of Rabbi Nachshon.

 

I found that subtracting the 3383 months from three 25920-month cycles of the molad, one gets an interval in which the molad moves later by just one part, when measured in a week rather than a day, but this 74,377-month period (just under 6013.5 years) .  

 

Any period a multiple of 235 months and so 19 years must have a molad shift a multiple of 5 parts, because 5 is the highest common divisor of 235 & 25920. One could find a period that is multiple of 235 months, which changes the molad by just 5 parts, but that would be even longer and well beyond any realistic lifetime of the calendar under present rules, but it could be used to find shorter cycles with small molad change.

 

Another way of finding such cycles is to start with the 247 years of -905 parts and one other that need not be so accurate.  I found 95 years, which moves the molad 14,305 parts earlier.

Sixteen 247-year cycles move the molad 14,480 parts earlier. The difference is just 175 parts.

 

And so (16*13 – 5) = 203 Metonic cycles = 3857 years moves the molad earlier by 175 parts.

 

 

Also, I’d be wary of using words such as advance and regress for the molad time, they could be construed with opposite meaning. I’d prefer later and earlier.

 

Karl

 

16(13(03

 

 

 

From: East Carolina University Calendar discussion List [mailto:[hidden email]] On Behalf Of Moongazer
Sent: 23 August 2017 15:53
To: [hidden email]
Subject: [SUSPICIOUS MESSAGE] Re: JMT Clock and Molad Calculator

 

Hello Karl Palmen and Calendar people,

 

Karl writes:

 

> I'd like to be able to switch between JMT Clock and Night/Day clock on one page.

 

There are reasons for keeping them on separate pages, one being that the JMT Clock is primarily of use to those with an interest in the Jewish Calendar, whereas the Night/Day Clock has a much broader appeal.

 

However, I have changed the destination on one of the hyperlinks so that on each one's page there is now a direct link to the other. On the JMT Clock page, click the link "Civil Time," and on the Night/Day Clock page, click the link "JMT Clock." Both links are in the explanatory text alongside the clock to its right. You can have each clock page open in its own browser tab and then tab from one to the other. Because the structure containing the clock is identical in both pages, if both pages are scrolled to the top, and you tab back and forth like that, quickly, it will create a visual effect like that of a blink-comparitor, as if the one clock is alternating in type. Try it.

 

> The Molad Calculator needs to show the month and year

 

It does that now, but, at present, it only shows two (pre-set) moladot : Press the Tohu button for the calendar's epochal molad, and, if you press the "Current" button, it shows the molad of Heshvan, 5778. That is just a temporary measure because I haven't written the calendar code yet, but in both cases, it shows the year and month name.

 

> I expect Moongazer is working on this.

 

Quite so, but I anticipate that it will take some time. I have written all the essential code many years ago in PowerBasic, so I just need to port it to Javascript. Even so, I expect it to take a while. BTW, my old Basic calendar code is now publicly available on my Jewish calendar website, where it is the first item in the downloads section. The routines are copiously commented and include much explanatory material. Even if you have no use for the code, it is worth a look at least at the custom modulo function included there and the comments on it. Here is the link:

 

tiny.cc/jewishcalendar

 

>>>> 

Also the ability to go forward of back by a fixed number of months would be great, especially to show the small change of 23 parts (1 minute 16 2/3 seconds) that occurs after 49 months or the minimum change of 1 part that occurs after 3383 months.

<<<< 

 

I was intrigued by this information, so I did the maths and found that, after a period of 49 months, the molad advances by 4d, 23h, 1057p (i.e. 23 parts short of 5 days). After 3383 months, it advances by 4d, 23h, 1079p (i.e. 1 part short of 5 days). Once you take into account the advance of nearly 5 days, plus the fact that neither of those two intervals is a multiple of Metonic cycles, these two phenomena did not animate me nearly as much as they did at first.

 

However, there is a another such phenomenon that I think is worthy of attention. It is much more striking and much better known. Its renown is due to the fact that it has led several famous Jewish authorities astray. After 247 years (13 Metonic cycles), the molad advances by 6d, 23h, 175p (i.e. 905 parts short of a whole week), so, effectively, the molad value regresses by 905 parts. This actually creates a tendency for the calendar to repeat itself after 247 years. That period became known as the Iggul (cycle) of Rabbi Nachshon (who served as Gaon from 881 to 889). He discovered this tendency and mistook it for a perfect repetition. Another famous authority, Jacob ben Asher ("the Rosh"), circa 1300, was also led astray by this "discovery" of Rabbi Nachshon.

 

As presently designed, the available navigation intervals in my molad calculator are: 1 month, 1 year, and 1, 13, 100 and 1000M (Metonic cycles). The reason I included 13M is precisely in order to let people explore this so-called cycle of Rabbi Nachshon and investigate how consistent it is. If people would like to also explore other similar phenomena like the two mentioned here by Karl and would find it convenient to set their own interval of any multiple of months for that purpose, I could possibly redesign the calculator to allow that. It will make the program logic more complex, but it would be worth doing it if people think that would be useful.

 

> It's probably the Nabble interface you are using which is messing up URLs.

 

I'm now posting by email via the listserv, so let's see if that makes a difference:

Here are the URLs again (though with the h t t p prefix stripped from the shortened URLs)

 

Night/Day Clock:   Reachable via   tiny.cc/night-day-clock   or:

 

 

 


View this message in context: Re: JMT Clock and Molad Calculator
Sent from the Calndr-L mailing list archive at Nabble.com.

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Re: [SUSPICIOUS MESSAGE] Re: JMT Clock and Molad Calculator

Karl Palmen

Dear Moongazer and Calendar People

 

If one subtracts one 247-year cycle from a 3857-year cycle, one gets a 3610-year cycle which delays the molad by 905 - 175 = 730 parts. Furthermore, this cycle is made up of ten lots of nineteen 19-year cycles.

 

No cycle shorter than this is better than the 247-year cycle. I confirmed this by checking that the numbers of Metonic cycles and Leap Weeks in both the 95-year and 247-year cycles form a determinant whose absolute value is 1.

 

95 years:  5 Metonic Cycles  17 Leap Weeks

247 years: 13 Metonic Cycles 44 Leap Weeks

 

13*17 – 5*44 = 1

 

Hence these two cycles form a pair of mixer cycles, so that every other cycle is made up of an integer mix of them.

 

Karl

 

16(13(03

 

From: Palmen, Karl (STFC,RAL,ISIS)
Sent: 24 August 2017 13:07
To: 'East Carolina University Calendar discussion List'
Subject: RE: [SUSPICIOUS MESSAGE] Re: JMT Clock and Molad Calculator

 

Dear Moongazer and Calendar People

 

Thank you Moongazer for your reply.

 

I’ll reply just to

I was intrigued by this information, so I did the maths and found that, after a period of 49 months, the molad advances by 4d, 23h, 1057p (i.e. 23 parts short of 5 days). After 3383 months, it advances by 4d, 23h, 1079p (i.e. 1 part short of 5 days). Once you take into account the advance of nearly 5 days, plus the fact that neither of those two intervals is a multiple of Metonic cycles, these two phenomena did not animate me nearly as much as they did at first.

 

However, there is a another such phenomenon that I think is worthy of attention. It is much more striking and much better known. Its renown is due to the fact that it has led several famous Jewish authorities astray. After 247 years (13 Metonic cycles), the molad advances by 6d, 23h, 175p (i.e. 905 parts short of a whole week), so, effectively, the molad value regresses by 905 parts. This actually creates a tendency for the calendar to repeat itself after 247 years. That period became known as the Iggul (cycle) of Rabbi Nachshon (who served as Gaon from 881 to 889). He discovered this tendency and mistook it for a perfect repetition. Another famous authority, Jacob ben Asher ("the Rosh"), circa 1300, was also led astray by this "discovery" of Rabbi Nachshon.

 

I found that subtracting the 3383 months from three 25920-month cycles of the molad, one gets an interval in which the molad moves later by just one part, when measured in a week rather than a day, but this 74,377-month period (just under 6013.5 years) .  

 

Any period a multiple of 235 months and so 19 years must have a molad shift a multiple of 5 parts, because 5 is the highest common divisor of 235 & 25920. One could find a period that is multiple of 235 months, which changes the molad by just 5 parts, but that would be even longer and well beyond any realistic lifetime of the calendar under present rules, but it could be used to find shorter cycles with small molad change.

 

Another way of finding such cycles is to start with the 247 years of -905 parts and one other that need not be so accurate.  I found 95 years, which moves the molad 14,305 parts earlier.

Sixteen 247-year cycles move the molad 14,480 parts earlier. The difference is just 175 parts.

 

And so (16*13 – 5) = 203 Metonic cycles = 3857 years moves the molad earlier by 175 parts.

 

 

Also, I’d be wary of using words such as advance and regress for the molad time, they could be construed with opposite meaning. I’d prefer later and earlier.

 

Karl

 

16(13(03