Many pendulum clocks are capable of well under 1 ppm accuracy, which is better than many quartz oscillators. Here is a tour of clock precision by orders of magnitude: http://leapsecond.com/ten/ Here is a world record…
That's correct. On NT/Alpha context switching was done in ntos\ke\alpha\ctxsw.s, which was regular kernel mode assembler code. A PAL call was made but it simply set the new Teb and Pdr; two or three lines of code. I've…
The original volt-nuts mailing list pretty much faded away as the members use the eevblog forum now. See the Metrology section. The time-nuts mailing list is still very active, now in its 23rd year. More info at the…
That's the price -- when new. But most "time nuts" buy their atomic clocks well used on eBay or local surplus sales at a massive discount. For example the most recent H-maser on the hobbyist market went for just a few…
Author of the web site (leapsecond.com) here if you have any questions. I don't know how the title of the HN post was chosen. The actual title of the web page is "GPS, UTC, and TAI Clocks". The page is a javascript…
> Blockbuster had a chance to buy Netflix in the early 2000's for $50,000,000. Ah, an example of the Butterfly Effect: then we'd have a billion references to FAABG on the web instead of FAANG.
Previously (and posted 64000/89 days ago): https://news.ycombinator.com/item?id=24929726
TAI and UTC are based on the SI second. The SI second is specifically defined in terms of cesium atoms at no temperature, no velocity, and no elevation (aka, on the geoid). Consequently TAI and UTC are immune from…
The original pi/spigot work was done by Rabinowitz & Wagon [1]. See also the very readable works by Jeremy Gibbons [2] [3]. [1] https://en.wikipedia.org/wiki/Spigot_algorithm [2]…
You can grep the web for Dik's original version. The 3-line homage version I linked contains both his full name and the name of the algorithm used: "spigot" (as in spew, faucet), which itself contains the letters PI. In…
With a nod to fellow pi-hound Dik T Winter, three equal lines of C give 32k digits of pi: http://leapsecond.com/tools/pi3.c
> LF is line feed, thus new line. LF is line feed, thus next line. The CR is to readjust the write head back to the starting position. A line feed alone is not a new line because some or most of the line is already used…
Only a positive leap second is “over in a second”. A negative leap second is essentially “over before it starts”. This asymmetry is an opportunity for code to implement UTC incorrectly. Another issue is that a positive…
DCF77 has a leap second warning bit. PTB says it is up to the user to know if it positive or negative. If a clock blindly assumes it is a positive leap that’s an error in the design of the clock. This is not ideal.…
True, but note the GPS data transmission rate is only 50 bps; yes, just 50 bits per second. The signal is so week and so slow that after headers and error correction you get less than 4 bytes of data per second. When…
Don't worry. This happened once before in 2003 [1]. UTC has provisions for positive or negative leap seconds; that works fine. GPS runs without the hassle of leap seconds; that works fine too. GPS users often want to…
As a patient hobbyist collector I try to buy one of each. My goal was to learn the history and theory of each one, explore the magnificent design, measure the actual timing accuracy, read as many old books or articles…
Yes, 500 pounds of gear sounds about right. I was aware that the car was slightly heavier than usual and drove accordingly. There was no hurry; it was not a race, just a leisurely weekend trip, about 2.5 hours in the…
Look for any vintage caesium clock made by National, Varian, Hewlett-Packard / Agilent / Symmetricom / Microsemi / Microchip, FEI, FTS / Austron / DATUM, Oscilloquartz, and maybe others. None of them are a restricted…
I anticipated that, so I had relativity books and physics magazines with pictures of Einstein on the front seat just in case we got stopped and the officer wanted a quick lesson in the fun of measuring time dilation. It…
If you have experience with analog and digital electronics it's not very hard. Atomic clocks were part of Hewlett-Packard's glory days and in that era the user got full documentation, schematics, theory,…
Cesium atomic clocks are not radioactive, nor are they based on radioactive decay. The isotope used for cesium beam atomic clocks is natural and stable Cs-133. The clock is based on an ultra-precise energy transition…
Yes, the original Mt Rainier experiment in 2005 caught the attention of Stephen Hawking and I was asked to repeat the experiment for his PBS/BBC TV series in 2016. It was mid-winter up here in PNW so we used Mt Lemmon…
Thanks, DanG. Author here. I happen to be reading HN right now if anyone has questions about cesium clocks or using them to demonstrate relativistic effects. This is just a DIY hobby of mine.
About 70 lbs (30 kg), so not difficult to lift or carry with two hands. But it took a real man (my brother-in-law, construction worker) to hold it outstretched like you see in the photo.
Many pendulum clocks are capable of well under 1 ppm accuracy, which is better than many quartz oscillators. Here is a tour of clock precision by orders of magnitude: http://leapsecond.com/ten/ Here is a world record…
That's correct. On NT/Alpha context switching was done in ntos\ke\alpha\ctxsw.s, which was regular kernel mode assembler code. A PAL call was made but it simply set the new Teb and Pdr; two or three lines of code. I've…
The original volt-nuts mailing list pretty much faded away as the members use the eevblog forum now. See the Metrology section. The time-nuts mailing list is still very active, now in its 23rd year. More info at the…
That's the price -- when new. But most "time nuts" buy their atomic clocks well used on eBay or local surplus sales at a massive discount. For example the most recent H-maser on the hobbyist market went for just a few…
Author of the web site (leapsecond.com) here if you have any questions. I don't know how the title of the HN post was chosen. The actual title of the web page is "GPS, UTC, and TAI Clocks". The page is a javascript…
> Blockbuster had a chance to buy Netflix in the early 2000's for $50,000,000. Ah, an example of the Butterfly Effect: then we'd have a billion references to FAABG on the web instead of FAANG.
Previously (and posted 64000/89 days ago): https://news.ycombinator.com/item?id=24929726
TAI and UTC are based on the SI second. The SI second is specifically defined in terms of cesium atoms at no temperature, no velocity, and no elevation (aka, on the geoid). Consequently TAI and UTC are immune from…
The original pi/spigot work was done by Rabinowitz & Wagon [1]. See also the very readable works by Jeremy Gibbons [2] [3]. [1] https://en.wikipedia.org/wiki/Spigot_algorithm [2]…
You can grep the web for Dik's original version. The 3-line homage version I linked contains both his full name and the name of the algorithm used: "spigot" (as in spew, faucet), which itself contains the letters PI. In…
With a nod to fellow pi-hound Dik T Winter, three equal lines of C give 32k digits of pi: http://leapsecond.com/tools/pi3.c
> LF is line feed, thus new line. LF is line feed, thus next line. The CR is to readjust the write head back to the starting position. A line feed alone is not a new line because some or most of the line is already used…
Only a positive leap second is “over in a second”. A negative leap second is essentially “over before it starts”. This asymmetry is an opportunity for code to implement UTC incorrectly. Another issue is that a positive…
DCF77 has a leap second warning bit. PTB says it is up to the user to know if it positive or negative. If a clock blindly assumes it is a positive leap that’s an error in the design of the clock. This is not ideal.…
True, but note the GPS data transmission rate is only 50 bps; yes, just 50 bits per second. The signal is so week and so slow that after headers and error correction you get less than 4 bytes of data per second. When…
Don't worry. This happened once before in 2003 [1]. UTC has provisions for positive or negative leap seconds; that works fine. GPS runs without the hassle of leap seconds; that works fine too. GPS users often want to…
As a patient hobbyist collector I try to buy one of each. My goal was to learn the history and theory of each one, explore the magnificent design, measure the actual timing accuracy, read as many old books or articles…
Yes, 500 pounds of gear sounds about right. I was aware that the car was slightly heavier than usual and drove accordingly. There was no hurry; it was not a race, just a leisurely weekend trip, about 2.5 hours in the…
Look for any vintage caesium clock made by National, Varian, Hewlett-Packard / Agilent / Symmetricom / Microsemi / Microchip, FEI, FTS / Austron / DATUM, Oscilloquartz, and maybe others. None of them are a restricted…
I anticipated that, so I had relativity books and physics magazines with pictures of Einstein on the front seat just in case we got stopped and the officer wanted a quick lesson in the fun of measuring time dilation. It…
If you have experience with analog and digital electronics it's not very hard. Atomic clocks were part of Hewlett-Packard's glory days and in that era the user got full documentation, schematics, theory,…
Cesium atomic clocks are not radioactive, nor are they based on radioactive decay. The isotope used for cesium beam atomic clocks is natural and stable Cs-133. The clock is based on an ultra-precise energy transition…
Yes, the original Mt Rainier experiment in 2005 caught the attention of Stephen Hawking and I was asked to repeat the experiment for his PBS/BBC TV series in 2016. It was mid-winter up here in PNW so we used Mt Lemmon…
Thanks, DanG. Author here. I happen to be reading HN right now if anyone has questions about cesium clocks or using them to demonstrate relativistic effects. This is just a DIY hobby of mine.
About 70 lbs (30 kg), so not difficult to lift or carry with two hands. But it took a real man (my brother-in-law, construction worker) to hold it outstretched like you see in the photo.