# Is the gravitational force G constant **URL:** \ **Category:** Factual Questions\ **Created:** [September 17, 2013, 12:30pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043 "2013-09-17T12:30:42Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [September 17, 2013, 5:19pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/21 "2013-09-17T17:19:05Z")
> [@deltasigma](#): > > I find this possibility intriguing. If you don’t, that’s fine. There’s intriguing and then there’s intriguing. If you read an issue of, say, _New Scientist_ you’ll find about seven of these articles. The first issue makes you go Wow! The next issue has seven more and you marvel at Science! Then the third issue has seven more and you start to wonder why these aren’t making the cover. After a year you notice that the same things that were overturned a year ago are being overturned again. After two years you realize that the proofs of experimental errors are also there, sometimes, in smaller type. And nothing major ever gets rewritten. That’s a layman’s perspective, though from someone who is fairly familiar with popular science writing. Every good experiment gets published. Some get hyped. But almost none of even the good experiments change anything fundamental. Look at the Large Hadron Collider. Years and years of searching for the Higgs and at the end they had a definite maybe. But in those years and years you could have read hundreds of articles, all with headline claims. My advice is to stop paying attention to the details. If everything were to change you’d hear about it. Science doesn’t stop being fascinating because individual experiments fail to upend well-established notions. But you’ll get disillusioned and jaded if you run in waving every paper and asking, “Is this IT?!” Science doesn’t work that way. And for a better explanation why, try [Notorious big G: The struggle to pin down gravity](http://www.newscientist.com/article/mg21028091.500-notorious-big-g-the-struggle-to-pin-down-gravity.html?full=true#.UjiN7D9Sh5Y). That’s the full article, from behind the paywall, so I’m not sure if you’ll see it. Here are some pertinent paragraphs. > [@](#): > > Not that it is easy to be sure the movements are down to gravity alone. “It’s about thinking of all the things the world can do to you to muck up your experiment,” says Parks. The pair set up the pendulums in a vacuum to avoid the effects of temperature changes and air resistance slowing the pendulums’ movements. They also floated the tungsten stacks on a thin layer of air to stop them vibrating unexpectedly. Even so, tiptoeing anywhere near the experiment was a no-no: the additional mass of a person would weigh down one side of the floor and nudge the apparatus ever so slightly. > > The problems didn’t stop at the doors of the lab. Next to, and towering over, the basement where the experiment was situated was a high-rise block. As the sun crept across the sky during the day, it warmed first one side of the tower and then the other, causing it to expand unevenly. The effect was to imperceptibly tilt the tower and everything attached to it, including Parks’s lab, first one way and then the other. > > Even that cruel trick was nothing compared to what was unmasked the day the fire alarm sounded. “There had been regular spikes in data taken during the day,” says Parks. “They just went quiet.” It turned out that a surge in current each time the elevator moved in the tower caused a slight change in the magnetisation of the pendulum bobs, moving them ever so slightly and skewing the results. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 17, 2013, 5:23pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/22 "2013-09-17T17:23:03Z")
> [@](#): > > Yeah, that’s what I figured. But even so, with Josephson junction devices, interferometers etc., it seems to me that we ought to be capable of sufficient precision that this shouldn’t be such an issue. But I’ll take your word for it. Thanks. Those things all help, but a chain is only as strong as its weakest link, and so too with experimental error. The existence of interferometers might mean that you can eliminate the position of the test masses as a source of significant error… But that just means that something else ends up being the dominant error source, instead. And once you’ve gotten some particular source of error down below the next-biggest source of error, further improvements in that piece of equipment no longer get you much benefit. It’s a game of whack-a-mole. ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [September 17, 2013, 5:24pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/23 "2013-09-17T17:24:08Z")
> [@deltasigma](#): > > I’m not “betting” on anything. I respect the people at Fermilab and pay attention when they point me to something. I find this possibility intriguing. If you don’t, that’s fine. I’ve already said it’s interesting but at this point I have no interest in investing much energy into getting excited about a result that is likely experimental error. I also really don’t get why you keep going on about it being referenced in the Fermilab newsletter. ---
**Author:** ![deltasigma](https://avatars.discourse-cdn.com/v4/letter/d/e5b9ba/32.png) [@deltasigma](https://boards.straightdope.com/u/deltasigma)\ **Post date:** [September 17, 2013, 5:29pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/24 "2013-09-17T17:29:05Z")
> [@Exapno\_Mapcase](#): > > There’s intriguing and then there’s intriguing. If you read an issue of, say, _New Scientist_ you’ll find about seven of these articles. The first issue makes you go Wow! The next issue has seven more and you marvel at Science! Then the third issue has seven more and you start to wonder why these aren’t making the cover. After a year you notice that the same things that were overturned a year ago are being overturned again. After two years you realize that the proofs of experimental errors are also there, sometimes, in smaller type. And nothing major ever gets rewritten. > > That’s a layman’s perspective, though from someone who is fairly familiar with popular science writing. Every good experiment gets published. Some get hyped. But almost none of even the good experiments change anything fundamental. Look at the Large Hadron Collider. Years and years of searching for the Higgs and at the end they had a definite maybe. But in those years and years you could have read hundreds of articles, all with headline claims. > > My advice is to stop paying attention to the details. If everything were to change you’d hear about it. Science doesn’t stop being fascinating because individual experiments fail to upend well-established notions. But you’ll get disillusioned and jaded if you run in waving every paper and asking, “Is this IT?!” Science doesn’t work that way. > > And for a better explanation why, try [Notorious big G: The struggle to pin down gravity](http://www.newscientist.com/article/mg21028091.500-notorious-big-g-the-struggle-to-pin-down-gravity.html?full=true#.UjiN7D9Sh5Y). That’s the full article, from behind the paywall, so I’m not sure if you’ll see it. Here are some pertinent paragraphs. I’m sure you’re trying to be helpful and I appreciate that, but I don’t appreciate the condescension. I’ve been following the popular science press for 30 years - which how long I’ve subscribed to Science News. So I’m quite familiar with science reporting - good science reporting. I’ve also subscribed to the Fermilab newsletter long enough to know that they don’t toss out popsci articles willy nilly. And btw, I also subscribe to New Scientist so I know that they do tend to plump things up to make them more appealing. But they also generally make an effort to give you the full picture as they do here. ---
**Author:** ![deltasigma](https://avatars.discourse-cdn.com/v4/letter/d/e5b9ba/32.png) [@deltasigma](https://boards.straightdope.com/u/deltasigma)\ **Post date:** [September 17, 2013, 5:30pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/25 "2013-09-17T17:30:06Z")
> [@Grey](#): > > I also really don’t get why you keep going on about it being referenced in the Fermilab newsletter. If you were familiar with Fermilab, you would. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 17, 2013, 5:36pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/26 "2013-09-17T17:36:11Z")
The fact that Fermilab is talking about it is a promising sign that it’s good science. But being good science is not the same thing as being right. ---
**Author:** ![deltasigma](https://avatars.discourse-cdn.com/v4/letter/d/e5b9ba/32.png) [@deltasigma](https://boards.straightdope.com/u/deltasigma)\ **Post date:** [September 17, 2013, 5:40pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/27 "2013-09-17T17:40:36Z")
> [@Chronos](#): > > The fact that Fermilab is talking about it is a promising sign that it’s good science. But being good science is not the same thing as being right. Jesus. I’m well aware of that. Have I said anything to indicate otherwise? Do you people think that maybe we can stick to the issues in future posts rather than any issues you have with me personally? That’s what the pit is for. ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [September 17, 2013, 5:41pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/28 "2013-09-17T17:41:56Z")
> [@deltasigma](#): > > If you were familiar with Fermilab, you would. My god you’re right. You know I hear they have a very powerful particle accelerator. That must count for a lot! Now, incase you missed it > [@Grey](#): > > Besides any article coming from the IBWM dealing with G is going to get mentioned in an institutional newsletter. I’m no more impressed that it’s mentioned in a Fermilab newsletter than I would be if it came from the UofT’s physic’s department. The topic is interesting, it comes from the IBWM and it deals with G. ---
**Author:** ![deltasigma](https://avatars.discourse-cdn.com/v4/letter/d/e5b9ba/32.png) [@deltasigma](https://boards.straightdope.com/u/deltasigma)\ **Post date:** [September 17, 2013, 5:43pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/29 "2013-09-17T17:43:30Z")
> [@Grey](#): > > My god you’re right. You know I hear they have a very powerful particle accelerator. That must count for a lot! > > Now, incase you missed it > > I’m no more impressed that it’s mentioned in a Fermilab newsletter than I would be if it came from the UofT’s physic’s department. The topic is interesting, it comes from the IBWM and it deals with G. If you have a problem with me, take it to the pit. I dare you. ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [September 17, 2013, 5:52pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/30 "2013-09-17T17:52:05Z")
> [@deltasigma](#): > > If you have a problem with me, take it to the pit. I dare you. Dare me?! Hahahahahahaaa…snif…wow. Look I would’ve flipped that around - you seem to be having problems with our answers. What exactly are you hoping for here? Your OP was basically a MPSIMS post and once we dig out your questions which apparently were buried in the article (as though we were to know your questions were in there) you come across as upset that we’re not nearly as impressed by this article as you are. ---
**Author:** ![deltasigma](https://avatars.discourse-cdn.com/v4/letter/d/e5b9ba/32.png) [@deltasigma](https://boards.straightdope.com/u/deltasigma)\ **Post date:** [September 17, 2013, 5:54pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/31 "2013-09-17T17:54:58Z")
reported. ---
**Author:** ![Asympotically\_fat](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Asympotically\_fat](https://boards.straightdope.com/u/Asympotically_fat)\ **Post date:** [September 17, 2013, 6:38pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/32 "2013-09-17T18:38:18Z")
Allowing G to vary is not in the realms of pseudoscience: Brans-Dicke theory replaces the (scalar) constant G with a scalar field. Brans-Dicke theory can recreate all predictions of general relativity, simply because GR is simply a special case of BDT. Of course though until there’s a solid reason to favour Brans-Dicke theory of the simpler general relativity, the simpler theory is more preferable. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [September 17, 2013, 6:41pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/33 "2013-09-17T18:41:35Z")
> [@deltasigma](#): > > I’ve been following the popular science press for 30 years - which how long I’ve subscribed to Science News. So I’m quite familiar with science reporting - good science reporting. And yet you appear to be totally unfamiliar with the difficulties of measuring the strength of gravity. And with why any anomalous report will instantly be branded experimental error. We’re responding to your words, which are all we have to work with. Your words say, hey, this must be super-important - it got published. You have a long posting history of doing so. And you are always annoyed when you are told otherwise. We have to assume there’s something you’re not getting. ---
**Author:** ![deltasigma](https://avatars.discourse-cdn.com/v4/letter/d/e5b9ba/32.png) [@deltasigma](https://boards.straightdope.com/u/deltasigma)\ **Post date:** [September 17, 2013, 6:48pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/34 "2013-09-17T18:48:03Z")
> [@Exapno\_Mapcase](#): > > And yet you appear to be totally unfamiliar with the difficulties of measuring the strength of gravity. And with why any anomalous report will instantly be branded experimental error. > > We’re responding to your words, which are all we have to work with. Your words say, hey, this must be super-important - it got published. You have a long posting history of doing so. And you are always annoyed when you are told otherwise. We have to assume there’s something you’re not getting. I read vast amounts of material covering subjects from molecular biology to economics to cosmology. I’m an admitted dilettante. If there weren’t gaps in my knowledge, it would be astounding. Your criticism however was directed at my apparent naivete. I hope you now stand corrected and can manage to stay on topic from now on. ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [September 17, 2013, 6:54pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/35 "2013-09-17T18:54:44Z")
I’m sure we are all suitably chastised. ---
**Author:** ![deltasigma](https://avatars.discourse-cdn.com/v4/letter/d/e5b9ba/32.png) [@deltasigma](https://boards.straightdope.com/u/deltasigma)\ **Post date:** [September 17, 2013, 6:55pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/36 "2013-09-17T18:55:36Z")
> [@Grey](#): > > I’m sure we are all suitably chastised. I’m happy to hear that.😛 ---
**Author:** ![Asympotically\_fat](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Asympotically\_fat](https://boards.straightdope.com/u/Asympotically_fat)\ **Post date:** [September 17, 2013, 6:58pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/37 "2013-09-17T18:58:20Z")
The problem with magazines like New Scientist is that they decontextualise results/discoveries by presenting them at their very highest when in reality their importance usually falls well short of this. ---
**Author:** ![deltasigma](https://avatars.discourse-cdn.com/v4/letter/d/e5b9ba/32.png) [@deltasigma](https://boards.straightdope.com/u/deltasigma)\ **Post date:** [September 17, 2013, 7:01pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/38 "2013-09-17T19:01:03Z")
> [@Asympotically\_fat](#): > > The problem with magazines like New Scientist is that they decontextualise results/discoveries by presenting them at their very highest when in reality their importance usually falls well short of this. Exactly. That’s why I posted this. To get context. But I’m not really getting any. I appreciate your comment before but as I said earlier, what I really want is background. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [September 17, 2013, 8:04pm UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/39 "2013-09-17T20:04:38Z")
**Moderator Note** This thread went a little off track for the bounds of GQ. Since it seems to be getting back on track on its own I’m not going to issue any warnings or anything at this time. This is just a friendly reminder to keep everything GQ appropriate. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 18, 2013, 1:04am UTC](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043/40 "2013-09-18T01:04:26Z")
> [@](#): > > Quoth **Asymptotically Fat** : > > Allowing G to vary is not in the realms of pseudoscience: Brans-Dicke theory replaces the (scalar) constant G with a scalar field. Brans-Dicke theory can recreate all predictions of general relativity, simply because GR is simply a special case of BDT. > > Of course though until there’s a solid reason to favour Brans-Dicke theory of the simpler general relativity, the simpler theory is more preferable. There are actually quite a few different alternate models of which GR is a special case. Most of them (including Brans-Dicke) can be encompassed in the [Paramaterized Post-Newtonian](http://en.wikipedia.org/wiki/Parameterized_post-Newtonian_formalism) formalism. [Previous page](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043.md?page=1) [Next page](https://boards.straightdope.com/t/is-the-gravitational-force-g-constant/669043.md?page=3)