On 6/7/19 3:32 PM, Michael Wouters wrote:
As promised, here's one pertinent paper, about using cryogenic
sapphire oscillators at mm-wavelengths ( 1 mm = 300 GHz ).
https://arxiv.org/pdf/1106.0021.pdf
It's not the one I was looking for but it's a useful entry point.
One interesting number is that
As promised, here's one pertinent paper, about using cryogenic
sapphire oscillators at mm-wavelengths ( 1 mm = 300 GHz ).
https://arxiv.org/pdf/1106.0021.pdf
It's not the one I was looking for but it's a useful entry point.
One interesting number is that at one mm, the coherence time is
limited to
On 6/6/19 2:17 PM, Michael Wouters wrote:
My radio astronomer colleagues tell me that there is about a 20 minute
limit to VLBI observing runs because of atmospheric instability so this
limits improvements to be had from better clocks. My recollection is that a
maser is still sufficient out to
Hi
….. a…. but what about modeling the atmosphere? I believe you will find
that that is
(at least to some degree) limited by the clocks involved.
Bob
> On Jun 6, 2019, at 5:17 PM, Michael Wouters wrote:
>
> My radio astronomer colleagues tell me that there is about a 20 minute
> limit
My radio astronomer colleagues tell me that there is about a 20 minute
limit to VLBI observing runs because of atmospheric instability so this
limits improvements to be had from better clocks. My recollection is that a
maser is still sufficient out to 100 GHz. There is a paper about this that
I
Regarding Dana's remarks on VLBI, consider the recent black hole image released
by the Event Horizon Telescope.Measurements were taken at 230 GHz, and they
would like to begin measurements at 345 GHz.Hydrogen masers were used at
each telescope.I am no expert, but I strongly
"Some people build giant laser interferometers, other people build large-scale
particle accelerators, still other people build elaborate clocks. They are all
looking for the same thing: a conversation with Mother Nature that begins with,
"Hmm, that's funny," and ends in a Nobel acceptance
This thread reminds me of a few things, firstly, nuclear fusion:
On Wed, Jun 5, 2019 at 1:00 AM jimlux wrote:
>
> 30 odd years ago, I heard a speech from a guy at AT who said that by
> definition, you cannot predict technology that will result in a
> revolution ahead of time.
>The cost of a
This topic reminds me of my first job at NPL Teddington back in the late
60's when Prof Essen was my boss's boss.
Frequency standards, length standards, etc, etc.
Happy days, an amazing place to work, an amazing library, and one hell
of a start for a 16yo for a career in electronic and
Being thoughtfully non-dismissive.
Personally, I subscribe to the school of "We don't don't need it yet, but ..."
in the belief that things like insanely accurate clocks will lead to greater sources of
excitement later on.
And I am reminded that :
1. A guy with one clock knows what time it
Will Kimber wrote:
>
> The thing with TIME is that its measurement is a abstract concept. Most
> other "standards" have a physical representation.
The metre is derived from the second and the speed of light using
interferometry. The kg is derived from the metre and the second and the
planck
> As to your analogy, it is valid only if and to the extent that NIST-F2 has
> practical applications. That is what I am asking about.
The important thing about devices like NIST-F2 is not that they are better
than any other clocks, it's that they are still imperfect. The researchers
are
On 6/4/19 3:21 PM, Poul-Henning Kamp wrote:
In message
, "William H. Fite" writes:
What I am asking is not the validity of the quest for better timing
but rather its tangible applications.
Tangible for who ?
For the average pedestrian there are no *current* tangible applications
On 6/4/19 3:05 PM, Hal Murray wrote:
Are we developing these incredible devices just to push boundaries? Or do
they have some practical purpose?
I don't know of any current projects that need a significantly better clock,
but that's the sort of thing that wouldn't get a lot of publicity -
In answer to the question about radio astronomers, consider VLBI (Very Long
Baseline Interferometry).
VLBI is a mapping (imaging) process in which signals are *simultaneously*
received from
a small sky region of interest by a collection of radio telescopes
scattered about the world.
In order for
If I can stir the pot a bit.
What other standards are measured to the same degree of accuracy? i.e.
ppb or better.
The thing with TIME is that its measurement is a abstract concept. Most
other "standards" have a physical representation.
Cheers,
Will
On 5/06/19 10:21 AM, Poul-Henning Kamp
The article cited below gives some examples of what Optical Lattice
Clocks (OLC) would be useful for:
https://ieeexplore.ieee.org/document/6905489
Rick N6RK
On 6/4/2019 9:43 AM, William H. Fite wrote:
What useful purpose, if any, is served by the continuing evolution of
clocks like NIST-F2
That's an excellent point, Bob. We have friends who have friends who are
involved with the long baseline interferometry (LIGO) lab in Louisiana. I
will inquire and, if they have any relevant information I will pass it
along to you.
Thanks for your reply.
On Tuesday, June 4, 2019, Bob kb8tq
I appreciate your point, one that I have emphasized to my graduate students
many times over 30 years of teaching. Of course you are entirely correct.
On Tuesday, June 4, 2019, Kevin Birth wrote:
> When a clock is represented as only losing a second in billions of years
> that is a statement
In message
, "William H. Fite" writes:
>What I am asking is not the validity of the quest for better timing
>but rather its tangible applications.
Tangible for who ?
For the average pedestrian there are no *current* tangible applications
where cesium level time-keeping isn't plenty.
In answer to your question, there are practical things that can be done
with an optical or electron microscope that cannot be done with unaided
vision. What I am asking is not the validity of the quest for better timing
but rather its tangible applications. Note that I did not say or even
suggest
You will have an answer if you can answer the question:
"Why is an optical microscope needed when unaided vision is good enough?"
My PhD is in high energy particle physics ca 1966.
This is not intended to be 'Dismissive and/or snarky'.
Your statement "Dismissive and/or snarky replies will be
Hi
One very basic thing that precision clocks allow you to dig deeper into is
gravity. A gravity wave passing between two clocks should show up as a time
ripple.
Bob
> On Jun 4, 2019, at 12:43 PM, William H. Fite wrote:
>
> Warning: Potentially heretical material below
>
> Let me begin by
Warning: Potentially heretical material below
Let me begin by saying I am neither an engineer nor a time expert. My PhD
is in statistics and my spouse's PhD is in theoretical computer science,
working on quantum computer algorithms. Neither of us claims any special
expertise when it comes to time
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