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We still don't have a more precise value for "Big G"

arstechnica.com

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Re: We still don't have a more precise value for "Big G"

#61

Post by BigTTYGothGF »

i_think_so wrote: post #40
dudisubekti wrote: post #11

Earlier quoted context omitted.

We can literally observe cosmic microwave background and it fits our prediction that the universe was denser and hotter. It is a scientific theory. You might be confusing the established big bang with the more speculative cosmic inflation model. They're very closely related.

> We can literally observe cosmic microwave background and it fits our prediction that the universe was denser and hotter. I can't observe that, because I don't have the gear. (Nor the time, budget, inclination nor training, for that matter. :-) But I am happy to admit the possibility that some of those observations, as reported in the literature, are correct. However, unlike a depressingly large percentage of my for…

> They intentionally misrepresented the data and hence the conclusions by an order of magnitude, which allowed them to delude the whole world for decades that "humans are 98.8% the same as chimps!"

Your second link doesn't work, but more broadly you and I both know that there are lots and lots of different ways to measure sequence similarity.

Re: We still don't have a more precise value for "Big G"

#62

Post by BigTTYGothGF »

i_think_so wrote: post #23
contact9879 wrote: post #9

Earlier quoted context omitted.

how is this at all related to TFA

Gravity experiments? Easier to do accurately in lower gravity environments, like away from the Earth? And we just so happen to have a nearly permanent laboratory in orbit, which was built and is maintained at tremendous taxpayer expense? I thought this would be obvious from TFA. I should have been more explicit.

> And we just so happen to have a nearly permanent laboratory in orbit, which was built and is maintained at tremendous taxpayer expense?

Resources are finite, and even though they're not fungible, which current ISS experiment would you replace for this?

Also: https://link.aps.org/accepted/10.1103/PhysRevD.100.062003 >>> LISA Pathfinder (LPF) [10] was a drag-free interfer- ometer located at the first Lagrange point in space be- tween the Earth and Sun. It measured the differential acceleration between two gold-platinum test masses sus- pended in drag free control. By the end of its lifetime, it had surpassed both its requirements and those of its full scale model LISA [11]. Given the success of the mission, and in coordination with other system tests, a handful of days near the end of the mission extension were allocated to performing a dedicated big G experiment for the first time in space. However, because Pathfinder was not de- signed to perform this sort of measurement, it was known that systematics such as absolute distances would limit the results to no better than 1 % relative uncertainty.

Re: We still don't have a more precise value for "Big G"

#63

Post by BigTTYGothGF »

kergonath wrote: post #38
dingdongditchme wrote: post #29

Earlier quoted context omitted.

This is what has always made it hard for me to go beyond the Newtonian physics. The only thing I know and use daily that relies on relativity is GPS and having looked into the equations on how it accounts for this it seemed to me that I could not discount that the equations account for some arbitrary consistent (or random) error, not relativity specifically. All experiments I have run never needed precision beyond Ne…

You could well live your whole life without needing anything more than Newtonian Physics. For most of us, relativity is a fun thought experiment. If you want to grapple with it, special relativity is the answer to "how can the speed of light be constant regardless of the speed of whoever is measuring it?" In his "vulgarisation" books, Einstein explains it with nothing more sophisticated than trains and stopwatches. G…

> You could well live your whole life without needing anything more than Newtonian Physics.

Or Aristotelian.

Re: We still don't have a more precise value for "Big G"

#64

Post by ricksunny »

alkonaut wrote: post #33
ricksunny wrote: post #27

Earlier quoted context omitted.

By ascertaining an approxiamte value of G , perhaps? After that, you know M_earth, and already knowing Earth’s geometry, one arrives at average density rho.

Oh so the earth density is merely the motivation for the experiment? I read it as the earth mass actually being used somewhere in the formulas within the setup itself which was what confused me. He uses his experiment to calculate G based only on the test masses and spring and then the _result_ of the calculation was just used as a final step to calculate the mass of the earth, and then from that the density?

Several years back when I first learned about the Cavendish experiment, I was indeed surprised that he was able to measure anything related to gravity without using a planetary-scale mass as one of experimental masses.

Re: We still don't have a more precise value for "Big G"

#65

Post by recursivecaveat »

ricksunny wrote: post #64
alkonaut wrote: post #33

Earlier quoted context omitted.

Oh so the earth density is merely the motivation for the experiment? I read it as the earth mass actually being used somewhere in the formulas within the setup itself which was what confused me. He uses his experiment to calculate G based only on the test masses and spring and then the _result_ of the calculation was just used as a final step to calculate the mass of the earth, and then from that the density?

Several years back when I first learned about the Cavendish experiment, I was indeed surprised that he was able to measure anything related to gravity without using a planetary-scale mass as one of experimental masses.

Clever experiments to measure tiny values are probably my favorite kind of science. Millikan found the charge of an electron by looking for a common integer multiple of charge in tiny oil droplets. Or LIGO measures gravitational waves by watching the interference pattern generated over time by two light beams taking different paths.

Re: We still don't have a more precise value for "Big G"

#66

Post by i_think_so »

mr_mitm wrote: post #39
i_think_so wrote: post #8

Earlier quoted context omitted.

It might also be nice if cosmologists stopped claiming their Big Bang "Theory" wasn't more accurately termed a mere Hypothesis. IIRC, 12 out of 13 predictions failing and necessitating "model" "tweaks" is not a fantastic track record for a Theory, which are supposed to robustly survive investigation.

What are the 13 predictions? Can you list them or provide a link to that list?

I didn't upload this and I haven't verified it. But it might be useful to reference.

https://archive.org/download/the-big-bang-never-happened

And this is briefer but more recent.

https://web.archive.org/web/20260321014458/https://www.lppfu...

I trust anyone sufficiently interested can manage to google further without my help.

Re: We still don't have a more precise value for "Big G"

#67

Post by vscode-rest »

kergonath wrote: post #35
vscode-rest wrote: post #4

I appreciate the scientists’ honesty. When asked about big G and time invariance, he says he just takes it on faith that it has been the same forever. If more people would admit their leaps I think the theistic schism would be far more shallow.

> he says he just takes it on faith that it has been the same forever It’s not faith, it’s a working assumption. There are in facts Physicists working on figuring out what would change if some fundamental constants changed with time. Our best measurements and understanding right now is that they do not. If we show tomorrow that it’s wrong, then we’ll build better theories and move on. There is absolutely no faith inv…

Did you watch the video?

Re: We still don't have a more precise value for "Big G"

#68

Post by bowsamic »

mattclarkdotnet wrote: post #59
bowsamic wrote: post #45

Earlier quoted context omitted.

It can resolve them though

Only by embracing solipsism, in which case why are you here debating things, since your entire truth is derivable from your existence alone with no other observations or interactions required?

Solipsism is wrong.

Re: We still don't have a more precise value for "Big G"

#69

Post by ricksunny »

alkonaut wrote: post #33
ricksunny wrote: post #27

Earlier quoted context omitted.

By ascertaining an approxiamte value of G , perhaps? After that, you know M_earth, and already knowing Earth’s geometry, one arrives at average density rho.

Oh so the earth density is merely the motivation for the experiment? I read it as the earth mass actually being used somewhere in the formulas within the setup itself which was what confused me. He uses his experiment to calculate G based only on the test masses and spring and then the _result_ of the calculation was just used as a final step to calculate the mass of the earth, and then from that the density?

Y’know, I went and looked at the current Wikipedia page for the Cavendish experiment. There’s apparently more nuance than my simple outline offers, particularly as G wasn’t treated as an isolated quantity till decades after his experiment.

Linking directly to section anchor: https://en.wikipedia.org/wiki/Cavendish_experiment#Reformula...

There is less description than I would like, but I am happy to have been made aware of the discrepancy at all.

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