Bob,
I am glad to see you mention, what is in my opinion, the greatest bene=
fit of the present discussions. The natural human tendency is to 'gravitat=
e' toward those with whom we readily agree. That early-in-my-career tenden=
cy never motivated me to 'think outside the box' in the same way as my late=
r-in-career activities. To illustrate some of the benefits of 'cross-ferti=
lization' consider the following. One of the earliest of my experiments, a=
fter creating a fully differential capacitive sensor, was to try a differen=
t approach to measuring Newton's big G constant. If you will go to the fol=
lowing web page you will find an excellent discussion of the history of att=
empts to accurately measure this fundamental constant.
http://www.npl.washington.edu/eotwash/bigG
You will see documented there, by these world-class experimentalists, re=
asons for the monumental challenges faced by anyone trying to measure G wit=
h an accuracy to compare favorably with what has been accomplished with exp=
eriments focused on other of the constants of nature. Whereas many fundame=
ntal constants are known to parts that exceed 10 significant digits, when i=
t comes to G, values published by 'respected teams' have 'differed wildly' =
(agreements no better than 4 to 5 digits).
My first effort to measure G was met with dramatic and unexpected frustr=
ation, since I naively believed that previous difficulties must have result=
ed primarily from the use of inferior sensor choices. Just because my pate=
nted sensor might be better for some applications than was true of a previo=
us sensor type for the same experiment-does not mean that mine is for all e=
xperiments the better choice. To quote an old saying, "you can't make a si=
lk purse out of a sow's ear', even though the latter may be the better choi=
ce for some applications.
One of my long-time friends, Jim Faller, is a physics colleague whose c=
hoice of a radically different (free-fall) method allowed him to measure li=
ttle-g better than anybody else (exceeding a part per million). I wish tha=
t I could have also known personally his mentor at Princeton, whose influen=
ce on physics was of such broad extent. I highly recommend a look at the f=
ollowing web page (a biographical memoir).
http://www.princeton.edu/physics/about/history/memorable-members/robert-dic=
ke/
Dicke was responsible for a host of significant contributions to Physics . =
Newton used the simple pendulum to prove the equivalence principle (that =
inertial mass is the same as gravitational mass) to about a part per thousa=
nd. Dicke extended that proof to a part in 100 billion, by getting away f=
rom the torsion fiber method of the Eotvos balance, and doing something at =
least a hundred times better than what had been the 'standard' up to that p=
oint in time. Dicke's ideas were also responsible for what is now the wid=
espread use of synchronous detection electronic methods to dramatically imp=
rove measurements involving otherwise 'show stopping' noise (heart of the '=
lock-in amplifier').
We finally came to realize that material property limitations of the (v=
ery best known to man) torsion wires continue to be the 'achilles heel' for=
several 'fundamental' experiments. The 'Eotwash group' has pointed out (i=
n the web page reference above) how Japanese physicist Kuroda ".....recentl=
y pointed out that internal friction in the torsion fiber, which had previo=
usly been neglected, may have caused some of the problems in the existing m=
easurements." There is little question in my mind that their use of the=
expression 'may have influenced' is an understatement. My first experim=
ent was one involving a 'nearly simple though compound' pendulum having an =
axis of type with which seismologists can identify. The student-oriented =
"computerized Cavendish balance" that I later created uses a torsion wire i=
n the form of a very thin tungsten wire. My considerable experiments with =
both types strongly suggests that the 'achilles heel' has indeed been as Ku=
roda indicated (but not limited to just torsions wires; since axes are also=
afflicted by the complexities of internal friction).
Perhaps you will not be surprised to learn that Jim Faller (who has al=
so thought about springs) was naturally led to consider a serious measureme=
nt of big-G. He did famous previous experiments (known to seismologists) =
involving g-estimates around 9.8 m/s (but with many, many more digits than=
the 8 I've indicated as following the decimal point-numbers that change ac=
cording to location on our planet). Perhaps then the following of his rec=
ent comments to me should not be dismissed lightly (where his 'we' refers t=
o collaborator Sam Richmond):
My last physics adventure was a measurement of the Newtonian Constant of Gr=
avitation--big G--(PRL 105, 110801 (2010) Week ending 10 Sept. 2010) where =
we measured the (small!) gravitational deflection of a pendulum due to a 10=
00kgm source mass...and "got the wrong answer". Or at least that what CODA=
TA would have you believe...but I'm not at all so certain that this in fact=
the case. Harold Parks (postdoc) and I spent some 6 years --once we realiz=
ed that our answer did not agree with the "best" measurements done in the l=
ast 10 or so years --trying to figure out what we might have done wrong BUT=
we were simply unable to find any number-changing error source...so we jus=
t finally published."
We see from these examples, involving the brilliant contributions of var=
ious scientists throughout decades of careful experimentation, the very str=
ong evidence for important (debilitating) influence of internal friction on=
the noblest of efforts to try and better understand nature. Surely then, =
we should not then summarily dismiss the possibility that what has stymied =
others could also stymie our best efforts toward realization of a 'perfect'=
seismometer or of 'a perfect clock'. It is my heartfelt belief that co=
nsiderable benefit might be realized by our careful consideration of Bob's =
recommendations. As he has indicated, there is an extreme difference of op=
erational range of a clock, compared to that of a seismometer; so you may w=
ant to think of them ostensibly as vastly different instruments. So why sh=
ould we then pay attention to a careful look at both? Because in my opinio=
n it is what they have in common. Both are afflicted by, and thus their =
performance limitation derives ultimately from the same thing-the miniscule=
force changes of internal friction type that disrupt their dynamical prope=
rties. Physics is the premier science that you might believe to have alre=
ady provided a first principles, sound theoretical understanding of frictio=
n. I have said (and one of my encyclopedia articles dealing with the anhar=
monic oscillator supports the following view) that 'friction remains everyw=
here but in our understanding".
Randall
Bob,
I am glad to see you menti=
on, what is in my opinion, the greatest benefit of the present discussions.=
The natural human tendency is to ‘gravitate’ toward thos=
e with whom we readily agree. That early-in-my-career tendency never =
motivated me to ‘think outside the box’ in the same way as my l=
ater-in-career activities. To illustrate some of the benefits of R=
16;cross-fertilization’ consider the following. One of the earl=
iest of my experiments, after creating a fully differential capacitive sens=
or, was to try a different approach to measuring Newton’s big G const=
ant. If you will go to the following web page you will find an excell=
ent discussion of the history of attempts to accurately measure this fundam=
ental constant.
http://www.npl.washington.edu/eotwash=
/bigG
You will see docu=
mented there, by these world-class experimentalists, reasons for the monume=
ntal challenges faced by anyone trying to measure G with an accuracy to com=
pare favorably with what has been accomplished with experiments focused on =
other of the constants of nature. Whereas many fundamental constants =
are known to parts that exceed 10 significant digits, when it comes to G, v=
alues published by ‘respected teams’ have ‘differed wildl=
y’ (agreements no better than 4 to 5 digits).
My first effort to measure G was met with dr=
amatic and unexpected frustration, since I naively believed that previous d=
ifficulties must have resulted primarily from the use of inferior sensor ch=
oices. Just because my patented sensor might be better for some appli=
cations than was true of a previous sensor type for the same experimentR=
12;does not mean that mine is for all experiments the better choice. =
To quote an old saying, “you can’t make a silk purse out of a s=
ow’s ear’, even though the latter may be the better choice for =
some applications.
&n=
bsp; One of my long-time friends, Jim Faller, is a physics colleague w=
hose choice of a radically different (free-fall) method allowed him to meas=
ure little-g better than anybody else (exceeding a part per million). =
I wish that I could have also known personally his mentor at Princeton, wh=
ose influence on physics was of such broad extent. I highly recommend=
a look at the following web page (a biographical memoir).
http://www.princeton.edu/physics/about/=
history/memorable-members/robert-dicke/Dicke was responsible for a host of significant contributions to Physic=
s . Newton used the simple pendulum to prove the equivalence pr=
inciple (that inertial mass is the same as gravitational mass) to about a p=
art per thousand. Dicke extended that proof to a part in 100 billion,=
by getting away from the torsion fiber method of the Eotvos balance,=
and doing something at least a hundred times better than what had been the=
‘standard’ up to that point in time. Dicke’s=
ideas were also responsible for what is now the widespread use of synchron=
ous detection electronic methods to dramatically improve measurements invol=
ving otherwise ‘show stopping’ noise (heart of the ‘lock-=
in amplifier’).
=
; We finally came to realize that material property limitations =
of the (very best known to man) torsion wires continue to be the ‘ach=
illes heel’ for several ‘fundamental’ experiments. =
The ‘Eotwash group’ has pointed out (in the web page reference =
above) how Japanese physicist Kuroda “…..recently pointed out t=
hat internal friction in the torsion fiber, which had previously been negle=
cted, may have caused some of the problems in the existing measurements.=
221; There is little question in my mind that their=
use of the expression ‘may have influenced’ is an =
understatement. My first experiment was one involving a ‘nearly=
simple though compound’ pendulum having an axis of type with which s=
eismologists can identify. The student-oriented “computer=
ized Cavendish balance” that I later created uses a torsion wire in t=
he form of a very thin tungsten wire. My considerable experiments wit=
h both types strongly suggests that the ‘achilles heel’ has ind=
eed been as Kuroda indicated (but not limited to just torsions wires; since=
axes are also afflicted by the complexities of internal friction).
Perhaps you will not b=
e surprised to learn that Jim Faller (who has also thought about springs) w=
as naturally led to consider a serious measurement of big-G. He=
did famous previous experiments (known to seismologists) involving g-estim=
ates around 9.8 m/s (but with many, many more digits than the 8 IR=
17;ve indicated as following the decimal point—numbers that change ac=
cording to location on our planet). Perhaps then the following =
of his recent comments to me should not be dismissed lightly (where his =
216;we’ refers to collaborator Sam Richmond):
My last physics adventure was a measurement of the Newtonia=
n Constant of Gravitation--big G--(PRL 105, 110801 (2010) Week ending 10 Se=
pt. 2010) where we measured the (small!) gravitational deflection of a pend=
ulum due to a 1000kgm source mass...and "got the wrong answer".&n=
bsp; Or at least that what CODATA would have you believe...but I'm not at a=
ll so certain that this in fact the case. Harold Parks (postdoc) and I spen=
t some 6 years --once we realized that our answer did not agree with the &q=
uot;best" measurements done in the last 10 or so years --trying to fig=
ure out what we might have done wrong BUT we were simply unable to find any=
number-changing error source...so we just finally published.”
&nbs=
p; We see from these examples, involving the brilliant contributions =
of various scientists throughout decades of careful experimentation, the ve=
ry strong evidence for important (debilitating) influence of internal frict=
ion on the noblest of efforts to try and better understand nature. Su=
rely then, we should not then summarily dismiss the possibility that what h=
as stymied others could also stymie our best efforts toward realization of =
a ‘perfect’ seismometer or of ‘a perfect clock̵=
7;. It is my heartfelt belief that considerable benefit m=
ight be realized by our careful consideration of Bob’s recommendation=
s. As he has indicated, there is an extreme difference of operational=
range of a clock, compared to that of a seismometer; so you may want to th=
ink of them ostensibly as vastly different instruments. So why should=
we then pay attention to a careful look at both? Because in my opini=
on it is what they have in common. Both are afflicted by,=
and thus their performance limitation derives ultimately from the same thi=
ng—the miniscule force changes of internal friction type that disrupt=
their dynamical properties. Physics is the premier science tha=
t you might believe to have already provided a first principles, sound theo=
retical understanding of friction. I have said (and one of my encyclo=
pedia articles dealing with the anharmonic oscillator supports the followin=
g view) that ‘friction remains everywhere but in our understanding=
221;.
Randall
=