Pi approximation games

Actually I think there is a size lump of silicon, that is sufficiently big that at a given temperature, the number of silicon atoms in that lump varies based on the uncertainty principle. Virtual silicon atoms appear/disappear out of the vacuum all the time. (Trust me, as a EE I know this.) There is no counting the exact number of silicon nucleii in a large lump.

Steve

(snip, I wrote)

As I understand it, there are two paths. One defines Avogadro's number, the other hbar.

I went to a talk by someone from NIST not so long ago. After hearing about the silicon sphere, I thought about using it for a Cavendish type aparatus for determining G. Given that its mass, size, and mass distribution is known more accurately than usual for most objects, one should be able to very accurately measure the force. It might be, though, that the mass (density) isn't high enough, and maybe germanium should be used instead.

Otherwise, you have to get down to about the 1e-15 range to replace the time standard. Standards at 1e-16 are on the way.

Story I heard recently from a NIST person was that they have a clock that one can lift up 30cm (about 1 foot) and measure the gravitational (general relativity) time dilation.

I don't know about that one, but if they make a mass standard based on h, it will be hard to measure the variation.

-- glen

that's two different ways of defining the kilogram. but if you toss in other constants that are presently measured, you can fix both N_A and hbar. (not saying it all would be good.)

ir irridium. but i dunno how they would count the atoms.

nonetheless, it's because a Cavendish-like apparatus still measures G relatively poorly, that i don't ever in my lifetime expect units to get defined in terms of such a machine. but i *would* expect the watt-balance to become part of the unit standard (and replace the IPK).

if only we knew the mass of the Earth to a high degree of accuracy.

doesn't stop some folks from pushing "varying c" theories. of course they need to revert the definition of the meter to something pre-1960 to even speak of such.

L8r,

--

r b-j                  rbj@audioimagination.com

"Imagination is more important than knowledge."

What did he/she teach?

History? drama? civics? languages? phys.ed?

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

Neither have I.

Interestingly, the command line switch to start Octave for best Matlab compatibility is --braindead.

Octave script to calculate pi to the limit of its precision by integrating a circle:

1; output_precision (20) function y=f(x) y = sqrt (1 - x^2); endfunction [v, ier, nfun, err] = quad ("f", 0, 1); v*4

I first did that 30-something years ago on an HP41 programmable calculator. It took many more lines, including the numerical integrator, and took over an hour to run ;-)

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

True.

Absolutely.

As has been noted already, this discussion is pretty pedantic. All I am really saying is that the theoretical "true" values - that you can never measure, even if they can be said to exist at all - are irrational. In particular, I am saying that you can't call them "rational" nor "integer", unless of course your units are defined to make them rational.

...

You are almost right. The possibility exists that a pair of irrational numbers have a rational ratio. Sqrt(8)/sqtrt(2) is an example.

...

Jerry

--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

Hence the qualifying term "unrelated". These two number are related.

Steve

Numbers obtained by measurement rather than counting necessarily describe a range. There is an infinite count of numbers within that range. If you must describe measurements in terms of "rational" and "irrational", the correct description is "both".

Jerry

--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

If the numbers are unrelated, then the probability is /really/ small - it is infinitesimal.

Thanks Tim, (I've cross posted just for fun) for bombing out my usenet with this thread. I can't believe this was the one which was better than any troll post!

Mark DeArman

number

This is the first time i have seen virtual particles extended to complete nuclei with associated mass rather than the usual boson and lepton = virtual particles.

?-)

Cool. You heard it from me first. If the lump of silicon is large enough, this should happen.

Someone who is actually a physicist can tell you how large. :--)

Steve

Wow. And given a whale big enough, do whole cells pop in and out of existence?

--
Saludos.
Ignacio G.T.