Discussion:
Pulsars, clocks, and time nuts (Jim Palfreyman)
(too old to reply)
Tom Van Baak
2018-04-13 07:54:08 UTC
Permalink
Amazing news... 1.2.3.

1) Many of you know that pulsars are weird astronomical sources of periodic signals. Some are so accurate that they rival atomic clocks for stability! True, but I don't have a 100 foot antenna at home so I'll take their word for it. Plus, you have to account for a myriad of PhD-level corrections: from earth's rotation to general relativity. And, like quartz or rubidium clocks, pulsars drift (as they gradually slow down). Precision timing is not easy. If you poke around the web you can find numerous articles describing their detection and measurement and exploring their use as reference clocks, both here and potentially for deep-space timekeeping.

2) If you do a lot of clock measurement at home then you know the dark side of working with precision clocks. There are signal quality issues, measurement resolution issues, reference stability limitations, offset, drift, phase jumps, frequency jumps, missed or extra cycles, glitches, etc. For example, quartz oscillators (depending on make / model / luck) can exhibit frequency jumps; i.e., without warning they just change frequency without your permission. Ok, maybe not by a lot, but enough to notice; perhaps enough to cause trouble to any naive GPSDO PID algorithm that assumes steady state from the oscillator you thought was stable.

3) Now the exciting part! Fellow time-nut Jim Palfreyman studies pulsars. You've seen postings from him now and then over the years. It turns out Jim is the first person to catch a pulsar in the act of a frequency jump. After 3 years of continuous searching! This is really cool. Just amazing. You can't get more time nutty than this. And it just got published in Nature. It's a perfect never-give-up, i-eat-nanoseconds-for-breakfast, time nut thing to do. I am so impressed.

To quote Jim:

On December 12, 2016, at approximately 9:36pm at night, my phone
goes off with a text message telling me that Vela had glitched. The
automated process I had set up wasn't completely reliable - radio
frequency interference (RFI) had been known to set it off in error.

So sceptically I logged in, and ran the test again. It was genuine!
The excitement was incredible and I stayed up all night analysing the data.

What surfaced was quite surprising and not what was expected. Right
as the glitch occurred, the pulsar missed a beat. It didn't pulse.

Here is a very readable description of his discovery:

http://theconversation.com/captured-radio-telescope-records-a-rare-glitch-in-a-pulsars-regular-pulsing-beat-94815

And also the official Nature article with all the juicy, peer-reviewed details:

https://rdcu.be/LfP0

So congratulations to Jim. I will think of him next time my 10811A quartz oscillator does a frequency jump or next time my 60 Hz mains frequency monitor skips a cycle...

If you have comments or questions feel free to send them to Jim directly (see Cc: address). Perhaps he can summarize the questions and his answers in a posting to time-nuts soon.

/tvb

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Dana Whitlow
2018-04-13 13:38:30 UTC
Permalink
Tom's discussion about pulsars brought back some memories...

Many pulsars exhibit skipped pulses. And one curiosity that I didn't see
mentioned in Tom's discussion is that some pulsars even exhibit behavior
reminiscent of the "sawtooth jitter" so evident in the PPS outputs of most
GPS receivers. See figures 12-11 & 12-12 in "An Introduction to Radio
Astronomy" (2nd edition) by Burke and Graham-Smith. The first ed also
contains the basic plot (as figure 12-8 in this case), but whose explanation
is not as up-to-date).

For a deeper treatment of pulsars, also see
https://www.cv.nrao.edu/course/astr534/PDFnew.shtml
by Condon and Ransom (both of NRAO).

The above two references are the best Radio Astronomy tomes I've yet seen..

Pulsar timing has been (and still is) a very big deal in radio astronomy,
as it
is key to verification of certain points of Einstein's General Theory of
Relativity.

Here are two web sites in which audio recordings of various pulsar
sounds (made with larger radio telescopes) are presented.


(You may ignore the video part, even though it's "cute", but the
audio portion is a fine example of the pulse to pulse variations
exhibited by many pulsars, all wrapped up in one pulsar)

http://www.jb.man.ac.uk/pulsar/Education/Sounds/0329_stack.mp4
(I think this is the best overall site, giving quality recordings of a
fair number of different pulsars)

Dana
Post by Tom Van Baak
Amazing news... 1.2.3.
1) Many of you know that pulsars are weird astronomical sources of
periodic signals. Some are so accurate that they rival atomic clocks for
stability! True, but I don't have a 100 foot antenna at home so I'll take
their word for it. Plus, you have to account for a myriad of PhD-level
corrections: from earth's rotation to general relativity. And, like quartz
or rubidium clocks, pulsars drift (as they gradually slow down). Precision
timing is not easy. If you poke around the web you can find numerous
articles describing their detection and measurement and exploring their use
as reference clocks, both here and potentially for deep-space timekeeping.
2) If you do a lot of clock measurement at home then you know the dark
side of working with precision clocks. There are signal quality issues,
measurement resolution issues, reference stability limitations, offset,
drift, phase jumps, frequency jumps, missed or extra cycles, glitches, etc.
For example, quartz oscillators (depending on make / model / luck) can
exhibit frequency jumps; i.e., without warning they just change frequency
without your permission. Ok, maybe not by a lot, but enough to notice;
perhaps enough to cause trouble to any naive GPSDO PID algorithm that
assumes steady state from the oscillator you thought was stable.
3) Now the exciting part! Fellow time-nut Jim Palfreyman studies pulsars.
You've seen postings from him now and then over the years. It turns out Jim
is the first person to catch a pulsar in the act of a frequency jump. After
3 years of continuous searching! This is really cool. Just amazing. You
can't get more time nutty than this. And it just got published in Nature.
It's a perfect never-give-up, i-eat-nanoseconds-for-breakfast, time nut
thing to do. I am so impressed.
On December 12, 2016, at approximately 9:36pm at night, my phone
goes off with a text message telling me that Vela had glitched. The
automated process I had set up wasn't completely reliable - radio
frequency interference (RFI) had been known to set it off in error.
So sceptically I logged in, and ran the test again. It was genuine!
The excitement was incredible and I stayed up all night analysing the data.
What surfaced was quite surprising and not what was expected. Right
as the glitch occurred, the pulsar missed a beat. It didn't pulse.
http://theconversation.com/captured-radio-telescope-
records-a-rare-glitch-in-a-pulsars-regular-pulsing-beat-94815
https://rdcu.be/LfP0
So congratulations to Jim. I will think of him next time my 10811A quartz
oscillator does a frequency jump or next time my 60 Hz mains frequency
monitor skips a cycle...
If you have comments or questions feel free to send them to Jim directly
(see Cc: address). Perhaps he can summarize the questions and his answers
in a posting to time-nuts soon.
/tvb
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
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Bill Hawkins
2018-04-14 05:04:57 UTC
Permalink
It seems that pulsars are rotating stellar objects that have no reason
to change their rotation, except to decay.
Ruling out causes from the stellar object, one is left with things that
might be orbiting the object and their ability to absorb the pulse that
is aimed at us. One could move further out to the extremely low
probability that some interstellar object absorbed the pulse. This
doesn't explain the sawtooth, unless one of those orbiting bodies is
affecting the rotation rate of the pulsar, such as a binary star.

Disclaimer: I know very little about radio astronomy, but I've read a
lot of hard science fiction.

Bill Hawkins


-----Original Message-----
From: time-nuts [mailto:time-nuts-***@febo.com] On Behalf Of Dana
Whitlow
Sent: Friday, April 13, 2018 8:39 AM
To: Tom Van Baak; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Pulsars, clocks, and time nuts (Jim Palfreyman)

Tom's discussion about pulsars brought back some memories...

Many pulsars exhibit skipped pulses. And one curiosity that I didn't
see mentioned in Tom's discussion is that some pulsars even exhibit
behavior reminiscent of the "sawtooth jitter" so evident in the PPS
outputs of most GPS receivers. See figures 12-11 & 12-12 in "An
Introduction to Radio Astronomy" (2nd edition) by Burke and
Graham-Smith. The first ed also contains the basic plot (as figure 12-8
in this case), but whose explanation is not as up-to-date).

For a deeper treatment of pulsars, also see
https://www.cv.nrao.edu/course/astr534/PDFnew.shtml
by Condon and Ransom (both of NRAO).

The above two references are the best Radio Astronomy tomes I've yet
seen..

Pulsar timing has been (and still is) a very big deal in radio
astronomy, as it is key to verification of certain points of Einstein's
General Theory of Relativity.

Here are two web sites in which audio recordings of various pulsar
sounds (made with larger radio telescopes) are presented.

http://youtu.be/uHEVo-LkDrQ
(You may ignore the video part, even though it's "cute", but the audio
portion is a fine example of the pulse to pulse variations exhibited by
many pulsars, all wrapped up in one pulsar)

http://www.jb.man.ac.uk/pulsar/Education/Sounds/0329_stack.mp4
(I think this is the best overall site, giving quality recordings of a
fair number of different pulsars)

Dana
Post by Tom Van Baak
Amazing news... 1.2.3.
1) Many of you know that pulsars are weird astronomical sources of
periodic signals. Some are so accurate that they rival atomic clocks
for stability! True, but I don't have a 100 foot antenna at home so
I'll take their word for it. Plus, you have to account for a myriad of
PhD-level
corrections: from earth's rotation to general relativity. And, like
quartz or rubidium clocks, pulsars drift (as they gradually slow
down). Precision timing is not easy. If you poke around the web you
can find numerous articles describing their detection and measurement
and exploring their use as reference clocks, both here and potentially
for deep-space timekeeping.
Post by Tom Van Baak
2) If you do a lot of clock measurement at home then you know the dark
side of working with precision clocks. There are signal quality
issues, measurement resolution issues, reference stability
limitations, offset, drift, phase jumps, frequency jumps, missed or
extra cycles, glitches, etc.
Post by Tom Van Baak
For example, quartz oscillators (depending on make / model / luck) can
exhibit frequency jumps; i.e., without warning they just change
frequency without your permission. Ok, maybe not by a lot, but enough
to notice; perhaps enough to cause trouble to any naive GPSDO PID
algorithm that assumes steady state from the oscillator you thought
was stable.
Post by Tom Van Baak
3) Now the exciting part! Fellow time-nut Jim Palfreyman studies pulsars.
You've seen postings from him now and then over the years. It turns
out Jim is the first person to catch a pulsar in the act of a
frequency jump. After
3 years of continuous searching! This is really cool. Just amazing.
You can't get more time nutty than this. And it just got published in
Nature.
Post by Tom Van Baak
It's a perfect never-give-up, i-eat-nanoseconds-for-breakfast, time
nut thing to do. I am so impressed.
On December 12, 2016, at approximately 9:36pm at night, my phone
goes off with a text message telling me that Vela had glitched. The
automated process I had set up wasn't completely reliable - radio
frequency interference (RFI) had been known to set it off in error.
So sceptically I logged in, and ran the test again. It was
genuine!
Post by Tom Van Baak
The excitement was incredible and I stayed up all night analysing the data.
What surfaced was quite surprising and not what was expected. Right
as the glitch occurred, the pulsar missed a beat. It didn't pulse.
http://theconversation.com/captured-radio-telescope-
records-a-rare-glitch-in-a-pulsars-regular-pulsing-beat-94815
https://rdcu.be/LfP0
So congratulations to Jim. I will think of him next time my 10811A
quartz oscillator does a frequency jump or next time my 60 Hz mains
frequency monitor skips a cycle...
If you have comments or questions feel free to send them to Jim
directly (see Cc: address). Perhaps he can summarize the questions and
his answers in a posting to time-nuts soon.
/tvb
_______________________________________________
https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow
the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@febo.com To unsubscribe, go to
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and follow the instructions there.

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Dana Whitlow
2018-04-14 06:33:56 UTC
Permalink
According to my book, each magnetic pole of some pulsars is more
like a rotating circular array of sub-poles, where the direction of induced
radiation varies from sub-pole posetion to sub-pole position. And only a
small range of sub-pole positions out of the group happens to point in
the direction of the Earth.

A reason for a general slowdown is energy lost to the radiation. But
the glitches, in the case of the Vela pulsar at least, involve steps upward
in spin rate, although nowhere near enough to cancel the overall
slowing trend. The authors of "Introduction to Radio Astronomy" do a
much better job of explaining the sawtooth effect than my clumsy attempt.

Robert L. Forward, I suspect.

Dana
Post by Bill Hawkins
It seems that pulsars are rotating stellar objects that have no reason
to change their rotation, except to decay.
Ruling out causes from the stellar object, one is left with things that
might be orbiting the object and their ability to absorb the pulse that
is aimed at us. One could move further out to the extremely low
probability that some interstellar object absorbed the pulse. This
doesn't explain the sawtooth, unless one of those orbiting bodies is
affecting the rotation rate of the pulsar, such as a binary star.
Disclaimer: I know very little about radio astronomy, but I've read a
lot of hard science fiction.
Bill Hawkins
-----Original Message-----
Whitlow
Sent: Friday, April 13, 2018 8:39 AM
To: Tom Van Baak; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Pulsars, clocks, and time nuts (Jim Palfreyman)
Tom's discussion about pulsars brought back some memories...
Many pulsars exhibit skipped pulses. And one curiosity that I didn't
see mentioned in Tom's discussion is that some pulsars even exhibit
behavior reminiscent of the "sawtooth jitter" so evident in the PPS
outputs of most GPS receivers. See figures 12-11 & 12-12 in "An
Introduction to Radio Astronomy" (2nd edition) by Burke and
Graham-Smith. The first ed also contains the basic plot (as figure 12-8
in this case), but whose explanation is not as up-to-date).
For a deeper treatment of pulsars, also see
https://www.cv.nrao.edu/course/astr534/PDFnew.shtml
by Condon and Ransom (both of NRAO).
The above two references are the best Radio Astronomy tomes I've yet seen..
Pulsar timing has been (and still is) a very big deal in radio
astronomy, as it is key to verification of certain points of Einstein's
General Theory of Relativity.
Here are two web sites in which audio recordings of various pulsar
sounds (made with larger radio telescopes) are presented.
http://youtu.be/uHEVo-LkDrQ
(You may ignore the video part, even though it's "cute", but the audio
portion is a fine example of the pulse to pulse variations exhibited by
many pulsars, all wrapped up in one pulsar)
http://www.jb.man.ac.uk/pulsar/Education/Sounds/0329_stack.mp4
(I think this is the best overall site, giving quality recordings of a
fair number of different pulsars)
Dana
Post by Tom Van Baak
Amazing news... 1.2.3.
1) Many of you know that pulsars are weird astronomical sources of
periodic signals. Some are so accurate that they rival atomic clocks
for stability! True, but I don't have a 100 foot antenna at home so
I'll take their word for it. Plus, you have to account for a myriad of
PhD-level
corrections: from earth's rotation to general relativity. And, like
quartz or rubidium clocks, pulsars drift (as they gradually slow
down). Precision timing is not easy. If you poke around the web you
can find numerous articles describing their detection and measurement
and exploring their use as reference clocks, both here and potentially
for deep-space timekeeping.
Post by Tom Van Baak
2) If you do a lot of clock measurement at home then you know the dark
side of working with precision clocks. There are signal quality
issues, measurement resolution issues, reference stability
limitations, offset, drift, phase jumps, frequency jumps, missed or
extra cycles, glitches, etc.
Post by Tom Van Baak
For example, quartz oscillators (depending on make / model / luck) can
exhibit frequency jumps; i.e., without warning they just change
frequency without your permission. Ok, maybe not by a lot, but enough
to notice; perhaps enough to cause trouble to any naive GPSDO PID
algorithm that assumes steady state from the oscillator you thought
was stable.
Post by Tom Van Baak
3) Now the exciting part! Fellow time-nut Jim Palfreyman studies
pulsars.
Post by Tom Van Baak
You've seen postings from him now and then over the years. It turns
out Jim is the first person to catch a pulsar in the act of a
frequency jump. After
3 years of continuous searching! This is really cool. Just amazing.
You can't get more time nutty than this. And it just got published in
Nature.
Post by Tom Van Baak
It's a perfect never-give-up, i-eat-nanoseconds-for-breakfast, time
nut thing to do. I am so impressed.
On December 12, 2016, at approximately 9:36pm at night, my phone
goes off with a text message telling me that Vela had glitched.
The
Post by Tom Van Baak
automated process I had set up wasn't completely reliable - radio
frequency interference (RFI) had been known to set it off in
error.
Post by Tom Van Baak
So sceptically I logged in, and ran the test again. It was
genuine!
Post by Tom Van Baak
The excitement was incredible and I stayed up all night analysing the data.
What surfaced was quite surprising and not what was expected.
Right
Post by Tom Van Baak
as the glitch occurred, the pulsar missed a beat. It didn't pulse.
http://theconversation.com/captured-radio-telescope-
records-a-rare-glitch-in-a-pulsars-regular-pulsing-beat-94815
https://rdcu.be/LfP0
So congratulations to Jim. I will think of him next time my 10811A
quartz oscillator does a frequency jump or next time my 60 Hz mains
frequency monitor skips a cycle...
If you have comments or questions feel free to send them to Jim
directly (see Cc: address). Perhaps he can summarize the questions and
his answers in a posting to time-nuts soon.
/tvb
_______________________________________________
https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow
the instructions there.
_______________________________________________
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
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To unsubscribe, go to https://www.febo.com/cgi-bin/
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Achim Gratz
2018-04-14 10:37:41 UTC
Permalink
Post by Bill Hawkins
It seems that pulsars are rotating stellar objects that have no reason
to change their rotation, except to decay.
The whole point of that exercise was to determine which of the theories
that predict what the internal structure of a neutron star looks like is
more likely to be correct. Here's a not too long and not too dense (pun
intended) writeup:

https://arstechnica.com/science/2018/04/neutron-star-glitch-hints-at-superfluid-beneath-its-crust/
Post by Bill Hawkins
Ruling out causes from the stellar object,
You've taken a wrong turn right there. The timing variations that were
measured are (most likely) produced by the stellar object.


Regards,
Achim.
--
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

Waldorf MIDI Implementation & additional documentation:
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djl
2018-04-15 22:56:44 UTC
Permalink
Nice, Jim!!!
Post by Tom Van Baak
Amazing news... 1.2.3.
1) Many of you know that pulsars are weird astronomical sources of
periodic signals. Some are so accurate that they rival atomic clocks
for stability! True, but I don't have a 100 foot antenna at home so
I'll take their word for it. Plus, you have to account for a myriad of
PhD-level corrections: from earth's rotation to general relativity.
And, like quartz or rubidium clocks, pulsars drift (as they gradually
slow down). Precision timing is not easy. If you poke around the web
you can find numerous articles describing their detection and
measurement and exploring their use as reference clocks, both here and
potentially for deep-space timekeeping.
2) If you do a lot of clock measurement at home then you know the dark
side of working with precision clocks. There are signal quality
issues, measurement resolution issues, reference stability
limitations, offset, drift, phase jumps, frequency jumps, missed or
extra cycles, glitches, etc. For example, quartz oscillators
(depending on make / model / luck) can exhibit frequency jumps; i.e.,
without warning they just change frequency without your permission.
Ok, maybe not by a lot, but enough to notice; perhaps enough to cause
trouble to any naive GPSDO PID algorithm that assumes steady state
from the oscillator you thought was stable.
3) Now the exciting part! Fellow time-nut Jim Palfreyman studies
pulsars. You've seen postings from him now and then over the years. It
turns out Jim is the first person to catch a pulsar in the act of a
frequency jump. After 3 years of continuous searching! This is really
cool. Just amazing. You can't get more time nutty than this. And it
just got published in Nature. It's a perfect never-give-up,
i-eat-nanoseconds-for-breakfast, time nut thing to do. I am so
impressed.
On December 12, 2016, at approximately 9:36pm at night, my phone
goes off with a text message telling me that Vela had glitched. The
automated process I had set up wasn't completely reliable - radio
frequency interference (RFI) had been known to set it off in error.
So sceptically I logged in, and ran the test again. It was genuine!
The excitement was incredible and I stayed up all night analysing the data.
What surfaced was quite surprising and not what was expected. Right
as the glitch occurred, the pulsar missed a beat. It didn't pulse.
http://theconversation.com/captured-radio-telescope-records-a-rare-glitch-in-a-pulsars-regular-pulsing-beat-94815
https://rdcu.be/LfP0
So congratulations to Jim. I will think of him next time my 10811A
quartz oscillator does a frequency jump or next time my 60 Hz mains
frequency monitor skips a cycle...
If you have comments or questions feel free to send them to Jim
directly (see Cc: address). Perhaps he can summarize the questions and
his answers in a posting to time-nuts soon.
/tvb
_______________________________________________
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https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
--
Dr. Don Latham
PO Box 404, Frenchtown, MT, 59834
VOX: 406-626-4304

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