alpha2cen Posted November 7, 2011 Share Posted November 7, 2011 We know the gravity well. Then, Is the gravitational constant always constant? Is the present gravitational constant same as that of 10 million years ago ? Link to comment Share on other sites More sharing options...
swansont Posted November 7, 2011 Share Posted November 7, 2011 Currently G is changing no faster than about a part in 10^12 per year http://arxiv.org/pdf/gr-qc/0411113 (ArXiv copy of a PRL) I don't know if you can determine G from remote measurements (which would be old measurements by virtue of d =ct), because we assume the value to deduce the masses. The papers I can find all measure G-dot. Link to comment Share on other sites More sharing options...
Oldman Posted December 8, 2011 Share Posted December 8, 2011 Why G is changing --albeit very slowy? Can general relativity live with changing G? Link to comment Share on other sites More sharing options...
swansont Posted December 8, 2011 Share Posted December 8, 2011 Why G is changing --albeit very slowy? Can general relativity live with changing G? Nobody has claimed that it is (in the papers I found). The results are consistent with zero and place an upper bound on how fast it could be changing, which is a function of the experimental accuracy and precision. A claim that G was changing would require that zero be statistically excluded. Link to comment Share on other sites More sharing options...
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