Problem with G?

  • #1
Problem with G??

This tickled my fancy... anyone else heard anything like this before??

http://www.npl.washington.edu/eotwash/gconst.html [Broken]

Recently the value of G has been called into question by new measurements from respected research teams in Germany, New Zealand, and Russia. The new values disagree wildly. For example, a team from the German Institute of Standards led by W. Michaelis obtained a value for G that is 0.6% larger than the accepted value; a group from the University of Wuppertal in Germany led by Hinrich Meyer found a value that is 0.06% lower, and Mark Fitzgerald and collaborators at Measurement Standards Laboratory of New Zealand measured a value that is 0.1% lower. The Russian group found a curious space and time variation of G of up to 0.7% The collection of these new results suggests that the uncertainty in G could be much larger than originally thought. This controversy has spurred several efforts to make a more reliable measurement of G.
 
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Answers and Replies

  • #2
Is this just really new or just too far out there to comment on?
 
  • #3
62
0
G...

Just like any empirical constant (like 'little' g), G is the attempt of humans to fit a value to a quantity that has no real significance. G is just the empirical constant Newton needed to describe the effects of gravity. On a macro scale, knowing a 'constant' to within 1% is pretty damn good. Since Newton's equation for gravity is a macro scale equation, that's fine for me.

For example, when calculating the gravitational attraction between Sol and Earth, the masses of the bodies is less well known than 1%, so the error added in by G is marginal at best.
 
  • #4
selfAdjoint
Staff Emeritus
Gold Member
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Most of the constants of nature are known to much better precision than G, it has been notoriously difficult to measure accurately. It's not really a scandal, just a well-known difficulty. It doesn't affect the truth or falsity of any theories.
 
  • #5
Wouldn't it effect many of our accepted astronomical measurements though? I realize the formulas remain unchanged but the output seems like it might be significantly different.
 
  • #6
Chronos
Science Advisor
Gold Member
11,429
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Cosmological constraints on variation of G over time are much tighter than those established based on solar system experiments. Here is an example based on WMAP data:
"WMAP constraints on scalar-tensor cosmology and the variation of the gravitational constant"
http://arxiv.org/abs/astro-ph/0311274
 

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