Dear readers

Does anyone know at how short a distance it is possible to measure gravity?

I think I once read that 0.1mm was the limit, as other forces start to
dominate here. Can that be true?

Love,
Louise

Louise Johnson wrote:
Dear readers

Does anyone know at how short a distance it is possible to measure gravity?

I think I once read that 0.1mm was the limit, as other forces start to
dominate here. Can that be true?


Any point source which spreads its influence equally in all
directions without a limit to its range will obey the inverse square
law.
http://hyperphysics.phy-astr.gsu.edu...orces/isq.html


Sue...


Love,
Louise

Louise Johnson wrote:
Dear readers

Does anyone know at how short a distance it is possible to measure gravity?

I think I once read that 0.1mm was the limit, as other forces start to
dominate here. Can that be true?

It's very tricky to measure gravity below that distance, though the
goal of the EotWash group in Washington is to get down to 50 microns
or so. You might look at http://www.npl.washington.edu/eotwash/ for
more, including some discussion of experimental difficulties and
current limits.

Steve Carlip

wrote in message
...
| Louise Johnson wrote:
| Dear readers
|
| Does anyone know at how short a distance it is possible to measure
gravity?
|
| I think I once read that 0.1mm was the limit, as other forces start
to
| dominate here. Can that be true?
|
| It's very tricky to measure gravity below that distance, though the
| goal of the EotWash group in Washington is to get down to 50 microns
| or so. You might look at http://www.npl.washington.edu/eotwash/ for
| more, including some discussion of experimental difficulties and
| current limits.
|
| Steve Carlip

Which goes to show us that there is still a tremendous gap in our
experimental knowledge.

FrediFizzx

wrote:
Louise Johnson wrote:
Dear readers

Does anyone know at how short a distance it is possible to measure gravity?

I think I once read that 0.1mm was the limit, as other forces start to
dominate here. Can that be true?

It's very tricky to measure gravity below that distance, though the
goal of the EotWash group in Washington is to get down to 50 microns
or so. You might look at http://www.npl.washington.edu/eotwash/ for
more, including some discussion of experimental difficulties and
current limits.

.... or some might opine that gravity is already being measured
on a molecular scale.
==============
By grabbing each end of the rope and pulling it taut, he
can move the actin molecule precisely where he wants it. He is
gradually refining his ability to place the actin next to exactly
one myosin head to measure the force of its tug.

Muscle physiologists expect that force to be roughly 3 trillionths
of an ounce - not an easy pull to measure with a conventional
scale. Fortunately, laser traps provide a way to measure forces
like this, as well.

The electric field of the laser tends to hold the bead in the dead
center of the beam. Pulling the bead away from the center of
the laser beam requires force, and the farther it's pulled away,
the greater the force.

Finer can detect these tiny motions - as little as 1/1,000 of the
bead's diameter - by shining a light on the bead and measuring
changes in the way the bead deflects the light beam.
http://www.stanford.edu/dept/news/pr...01Arc2142.html

... Nesvizhevsky and co-workers used an intense horizontal
beam of ultra-cold neutrons from the reactor at the Institute
Laue-Langevin in Grenoble. By directing the beam slightly upwards
and allowing the neutrons to fall onto a mirror, also positioned
horizontally, the researchers were able to effectively hold the
neutrons in a gravitational potential well. Having bounced off the
mirror, the small kinetic energy due to the vertical
velocity of the neutrons was exactly balanced by the force of gravity
at varying heights above the mirror. The neutrons' lack of charge
and long lifetime minimized the effect of forces other than gravity.

http://physicsweb.org/articles/news/6/1/9

========

Sue...






Steve Carlip