J
John Fields
Guest
On Thu, 17 Jun 2010 21:34:48 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
It made sense to me, in that the first sentence was a quick pull on
your halter, and the second a rebuke of your claim that a magnetic
field (350kG is three hundred and fifty kilogauss, no?) has any effect
at all on the gravitation being measured.
Do you have any evidence to prove that a gravitational field is
affected by magnetism in other than a mundane way?
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
---On Thu, 17 Jun 2010 20:22:35 -0700,
"JosephKK"<quiettechblue@yahoo.com> wrote:
On Thu, 17 Jun 2010 08:40:07 -0700, John Larkin
jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
On Thu, 17 Jun 2010 06:41:25 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:
On Jun 17, 8:50 am, George Herold <gher...@teachspin.com> wrote:
On Jun 16, 11:38 pm, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 16 Jun 2010 19:52:34 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Jun 16, 10:17 pm, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 16 Jun 2010 22:03:46 -0400, Spehro Pefhany
speffS...@interlogDOTyou.knowwhat> wrote:
On Wed, 16 Jun 2010 17:23:13 -0700, the renowned John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 16 Jun 2010 16:54:42 -0700 (PDT), Richard Henry
pomer...@hotmail.com> wrote:
On Jun 16, 3:58 pm, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 16 Jun 2010 15:36:13 -0700 (PDT), Richard Henry
pomer...@hotmail.com> wrote:
On Jun 16, 12:53 pm, George Herold <gher...@teachspin.com> wrote:
On Jun 16, 2:31 pm, Archimedes' Lever <OneBigLe...@InfiniteSeries.Org
wrote:
On Wed, 16 Jun 2010 11:05:15 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
Cool, I have to scribble numbers on the paper though. 6400 feet is
about 2000m, the Earth is about 6E6 m in radius, Since we only want a
small change I can ignore the r^2 stuff and just multiple the ratio by
2. something like 4 parts out of 6,000. much smaller than the
divisions on your scale.
No you cannot. What makes you think that G decreases (or
increases)linearly?
Big G doesn't change at all. Little g (the force of gravity on the
Earths surface) will go as 1/r^2. For small changes in r the change
is approximately linear... first term in the taylor expansion if you
want to think of it that way. And it does go as 2*delta-R/Rearth
Not exactly. The mass of the Earth is not actually concentrated at a
single point.
Outside of a uniform spherical mass, g does behave as if all the mass
were concentrated at the center. The earth is non-homogenous, but
close enough. The short answer to my little problem is that the change
is about 1 part in 2000, too small to matter in the context of the
other measurement uncertainties.
If something is small enough, we engineers just write it off. A quick,
rough calculation is usually enough to decide if that's safe.
After all the profound word salads and hand-waving about forces and
masses and weights, it was fun to see if the lecturers could do a
simple high-school physics exercize.
John
Surveyors and navigators ignore the gravimetric variations at their
own peril.
Actually, delta-g may be less than 1:2000. After all, Truckee isn't
floating on air, it's sitting on rock. It's sort of, not quite, like
being on a planet that's one mile bigger in radius.
This is one I *can't* do in my head.
John
I've got access to a huge map of gravitational anomalies-- If I
remember, I'll take a gander at Truckee vs. San Francisco next time I
get a chance.
I guess the question is whether g at the top of a mountain is greater
or less than g at sea level. A zillion web sites say less, and use the
1/r^2 equation to demonstrate it, but that equation works if you're in
a balloon, not sitting on solid rock.
It depends on how spikey the mountain is.
John- Hide quoted text -
- Show quoted text -
Mountains are the light pieces of earth floating on the magma
underneath. Hey if we want to calculate the effect of the mountain...
well I'm a physicist... approximate the mountain as a sphere
I heard of this new'ish' gravimeter where they drop a corner cube
reflector as one arm of an interferometer and count fringes as it
drops... At least that's how I think it works.
George h.
Slick. You could digitize the photodiode signal and curve-fit the heck
out of it.
John- Hide quoted text -
- Show quoted text -
Yeah, I'll see if I can find a link. (I saw this at an APS trade
show.) I think the primary use is for miners mapping the local g
field to figure out where to dig.
George H.- Hide quoted text -
- Show quoted text -
http://principles.ou.edu/grav_ex/absolute.html
Pretty cool.
George H.
Neat. But at 350 kG, it must disturb the g field it's trying to
measure!
John
Oh come on JL. What you normally spout is tantamount to saying leverage
that distortion to your advantage.
If that sentence made any sense, I'd know if you were trying to insult
me or not.
It made sense to me, in that the first sentence was a quick pull on
your halter, and the second a rebuke of your claim that a magnetic
field (350kG is three hundred and fifty kilogauss, no?) has any effect
at all on the gravitation being measured.
Do you have any evidence to prove that a gravitational field is
affected by magnetism in other than a mundane way?