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In this similar question the answer says that because of relativity e=mc^2 a hot object has greater mass/energy therefore has greater gravity than a cold object.

But:

In Experiment on the Relationship between Gravity and Temperature they use the Cavendish method to show definitively that "the higher the temperature of the object, the smaller the absolute value of gravity and vice versa".

In physics we always say that a theory cannot hold once experimental proof to the contrary is given. So how do we rectify these two conflicting ideas?

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The paper you cite does not meet the standards of a scientific work, because:

  • they do not consider the experimental errors (precision),
  • they do not mention that their experimental findings are in an enormous conflict with many other older measurements.

Their main findings are that the 13°C bodies attract 3.5-times more than when their temperature is 23°C! The only reasonable conclusion is that they spoiled the measurement by a fatal experimental error.

Other indications (not proofs) of a low-quality work that can be found in this paper:

  • it ignores the existence of the general theory of relativity,
  • it is not written in sentences,
  • it is published in "International Journal of Physics" which is issued by a predatory (according to this blacklist) publisher sciepub.com.
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  • $\begingroup$ Have you seen tests done that prove against this paper? $\endgroup$
    – foolishmuse
    Commented Oct 16, 2022 at 20:56
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    $\begingroup$ @foolishmuse Do you not find the idea that a $10^\circ$ C increase in temperature corresponds to a factor $3.5$ decrease in $G$ at all suspicious? Especially in light of the fact that two of the "cold" trials differ in temperature by $3$ C but apparently correspond to exactly the same value of $G$? $\endgroup$
    – J. Murray
    Commented Oct 16, 2022 at 21:09
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    $\begingroup$ @foolishmuse Think about putting a pot of water on the stove, do you find it plausible that its weight decreases by a factor $3.5$ when it goes from $10^\circ$ C to $20^\circ$ C? $\endgroup$
    – J. Murray
    Commented Oct 16, 2022 at 21:11
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    $\begingroup$ @foolishmuse As a general comment, it is not and has never been the standard of the scientific method that every proposal is considered valid until disproven with a designed experiment. Your initial claim, "In physics we always say that a theory cannot hold once experimental proof to the contrary is given," while having some grain of truth, is a severe oversimplification. $\endgroup$
    – Rococo
    Commented Oct 16, 2022 at 21:53
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    $\begingroup$ Thanks all. A good lesson to be a little more discerning when looking at unusual papers. $\endgroup$
    – foolishmuse
    Commented Oct 16, 2022 at 23:41
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In physics we always say that a theory cannot hold once experimental proof to the contrary is given. So how do we rectify these two conflicting ideas?

Science is not so binary or linear as that. There is a lot of conflicting information, false starts, mistakes, and experimental uncertainties. Replication is important, as is credibility and experimental care.

A better model for scientific progress is Bayesian inference. New evidence shifts our belief in a theory based both on the strength of the prior evidence and on the strength of the new evidence.

In this case the prior evidence supporting general relativity is exceptionally strong. GR has been verified with a wide variety of different tests using different technologies and testing, performed by the most expert labs, and published in the most reputable journals. Therefore it will take similarly exceptionally strong evidence to refute it.

This particular experiment is published in a journal with no reputation (not even listed by typical indexing services), by a group I have never heard of, with no corroborating follow-up experiments, no confirmation by other technologies, and with many opportunities for experimental mistakes. This experiment is rather weak evidence. It should be considered and slightly reduce our posterior credence in GR. But it is certainly nowhere near strong enough to refute GR entirely by itself.

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