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Offline Rama Set

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Re: Cavendish experiment
« Reply #220 on: May 12, 2021, 11:39:26 AM »
The Cavendish experiment is not the only test of gravity, so his awareness of the imprecision of the Cavendish Experiment isn't evidence that "gravity is merely a belief".

He is aware that he can't measure gravity. Refer to the previous quotations.

He is talking about the Cavendish Experiment and it's pretty clear in the broader context that it was a matter of unsatisfactory precision.  This position is supported by the comments of other astrophysicists, as I showed you earlier.  He was not talking about the observation and measurement of gravity broadly, so your interpretation is untenable.
Th*rk is the worst person on this website.

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Offline Iceman

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Re: Cavendish experiment
« Reply #221 on: May 12, 2021, 11:52:26 AM »
...Terence Quinn is a British physicist who spent many years studying gravity and was emeritus director of the International Bureau of Weights and Measures. If he says it, it's golden.

Okay great, he said this in a nature piece:
"Who needs a more accurate numerical value of G (the current recommended value is 6.67408 ± 0.00031 × 10−11 kg−1 m3 s−2)? The short answer is, nobody, for the moment..."

https://www.nature.com/articles/nphys3651?proof=t


 I guess were done here?

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Offline Tom Bishop

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Re: Cavendish experiment
« Reply #222 on: May 12, 2021, 12:01:44 PM »
...Terence Quinn is a British physicist who spent many years studying gravity and was emeritus director of the International Bureau of Weights and Measures. If he says it, it's golden.

Okay great, he said this in a nature piece:
"Who needs a more accurate numerical value of G (the current recommended value is 6.67408 ± 0.00031 × 10−11 kg−1 m3 s−2)? The short answer is, nobody, for the moment..."

https://www.nature.com/articles/nphys3651?proof=t


 I guess were done here?

Here is his quote:

"Who needs a more accurate numerical value of G (the current recommended value6 is 6.67408 ± 0.00031 × 10−11 kg−1 m3 s−2)? The short answer is, nobody, for the moment, but being apparently unable to converge on a value for G undermines our confidence in the metrology of small forces. Although it is true that the orbits of the planets depend on the product of G and the mass of the Sun — the structures of all astrophysical objects are determined by the balance of gravity and other forces produced by, for example, gas, photon or degeneracy pressure — ab initio models of the Sun are still an order of magnitude away from predicting a value of G at a level comparable with laboratory determinations. We do not need a value of G to test for departures from the inverse square law or the equivalence principle. There is as yet no prospect of a theory of quantum gravity that would predict a value for G that could be tested by experiment."

The part you cut out after "nobody for the moment..." says that this value undermines their science in the metrology of small forces. He clearly suggests the recommended range is invalid and questionable there, rather than your suggestion that he is supporting it wholeheartedly. This is another point against you.

Trivializing the need for G doesn't directly address the matter of whether he thinks that he measured it. He is talking about the practical purpose for the such a measurement, in non-cavendish situations and measurements. He is correct that G is not needed for the equivalence principle tests. That's something else, showing that gravity does not depart on various ranges and situations from the concept that the Earth is accelerating upwards. The EP tests are highly and accurately verified.

Quinn's "we should be able to measure gravity" statement says that he cannot measure gravity in the Cavendish Experiment. In the quote you referenced we see a statement that the recommended range undermines their science in the metrology of small forces, showing that he is certainly not endorsing it. You're right. We are done here. We have talked about this for pages and you are still unable to substantiate your argument.
« Last Edit: May 12, 2021, 04:55:23 PM by Tom Bishop »

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Offline Iceman

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Re: Cavendish experiment
« Reply #223 on: May 12, 2021, 01:04:48 PM »
Yes that's great, the more quotes we can get from Dr. Quinn the better :) hes smarter than all of us on the matter!

"Could these unresolved discrepancies in G hide some new physics? This seems unlikely. I believe undiscovered systematic errors in all or some of these new experiments is the answer — G is difficult to measure but it should not be too difficult!"
- from the nature piece linked above

Now someone else's turn!

Re: Cavendish experiment
« Reply #224 on: May 12, 2021, 05:05:13 PM »
Now someone else's turn!
Go on then. I don't think this has any quotes from him, but it's an interesting article about the multiple ways they have of measuring gravity:

https://www.nature.com/articles/35050187?foxtrotcallback=true

For such a weak force it's impressive how accurate they can get the value of G and multiple methods of measuring it show that it can't be coincidence. It will be interesting to see if some of the newer experiments which claim a smaller error margin can do better still.
"On a very clear and chilly day it is possible to see Lighthouse Beach from Lovers Point and vice versa...Upon looking into the telescope I can see children running in and out of the water, splashing and playing. I can see people sun bathing at the shore
- An excerpt from the account of the Bishop Experiment. My emphasis

Re: Cavendish experiment
« Reply #225 on: May 15, 2021, 06:00:32 AM »

He clearly suggests the recommended range is invalid and questionable there, rather than your suggestion that he is supporting it wholeheartedly. This is another point against you.


How do you get to the conclusion that "he clearly suggests the recommended range is invalid and questionable there"? He simply does not say that. He does not mention the range at all in this quote. What he only talks about is our ability to measure small forces. He always talks about being able to take accurate measurements rather than measurements in general.

This is a another article from Quinn:

https://www.nature.com/articles/35050187?foxtrotcallback=true

It starts with "Newton's constant, G, which governs the strength of the gravitational attraction between two masses, is difficult to measure accurately".
He does not even question the existence of gravity as he takes it for granted both in this latest link and in the part from the other article that you quoted.

You can accept what he says or reject it, but you cannot use him as a reference for the notion that gravity does not exist.