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(Phys Org2)   New measure of gravitational constant higher than expected, says physicist ready for lecture to end   (phys.org ) divider line
    More: Interesting, gravitational constant higher, gravitational constants, refraction, Newtonian, physicists, G's, electromagnetic forces, speeches  
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1460 clicks; posted to Geek » on 10 Sep 2013 at 9:25 AM (2 years ago)   |   Favorite    |   share:  Share on Twitter share via Email Share on Facebook   more»



34 Comments     (+0 »)
 
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2013-09-10 09:02:45 AM  
That's just Q messing around again.
 
ZAZ [TotalFark]
2013-09-10 09:13:19 AM  
G has dropped 21 parts per million in 12 years, giving the universe less than a million years to live. And here I thought we had billions until the big rip. It's been nice knowing (some of) you.
 
2013-09-10 09:39:43 AM  

ZAZ: G has dropped 21 parts per million in 12 years, giving the universe less than a million years to live. And here I thought we had billions until the big rip. It's been nice knowing (some of) you.


The Gravitrons are becoming lazy Democrats.
 
2013-09-10 09:40:26 AM  

ZAZ: G has dropped 21 parts per million in 12 years, giving the universe less than a million years to live. And here I thought we had billions until the big rip. It's been nice knowing (some of) you.


Luckily for us, your momma's so fat and sticky she'll hold it all together.
 
2013-09-10 10:03:23 AM  
Heavy balls must be uncomfortable.

Now to the serious part.  Apparently they don't know which measurement is more accurate, so I have to wonder how they would be able to determine which one is actually more accurate.  Also, would the slight difference actually affect some other parts of physics?
 
2013-09-10 10:12:18 AM  
I couldn't reach Marty McFly so here is Spiderman

img821.imageshack.us
 
2013-09-10 10:16:44 AM  

Pharque-it: ZAZ: G has dropped 21 parts per million in 12 years, giving the universe less than a million years to live. And here I thought we had billions until the big rip. It's been nice knowing (some of) you.

The Gravitrons are becoming lazy Democrats.


That's too bad. They used to be so bootstrappy.
 
2013-09-10 10:23:09 AM  
The Leon particle is getting larger, however.
 
2013-09-10 10:24:39 AM  

MadMattressMack: Pharque-it: ZAZ: G has dropped 21 parts per million in 12 years, giving the universe less than a million years to live. And here I thought we had billions until the big rip. It's been nice knowing (some of) you.

The Gravitrons are becoming lazy Democrats.

That's too bad. They used to be so bootstrappy.


Maybe they've lost their Charm-Quarks.
 
2013-09-10 10:30:23 AM  

ZAZ: G has dropped 21 parts per million in 12 years, giving the universe less than a million years to live. And here I thought we had billions until the big rip. It's been nice knowing (some of) you.


why is he being made to carry so many parts and is he cool with you calling him G, dawg?
 
ZAZ [TotalFark]
2013-09-10 10:38:00 AM  
Also, would the slight difference actually affect some other parts of physics?

Very slightly. For astronomical objects we measure the product GM rather than mass alone. A part per million change in G means a part per million change in the mass of a star or planet, which has a similarly small effect on models.

Changing G would also affect grand unification models of particle physics, but we don't have any testable models yet.
 
2013-09-10 10:40:24 AM  
Do they know why the gravitational constant is increasing? Does it have to do with global warming?
 
2013-09-10 10:44:14 AM  

UberDave: That's just Q messing around again.


At my house, a thin ribbon resting between heavy balls is called a "scrote seam".
 
2013-09-10 11:01:15 AM  
"Modern researchers use two main types of methods to try to measure G, the first is a more advanced way to do the same thing Cavendish did two centuries ago, using lasers instead of candle light-it's based on measuring the amount of torque applied to a thin ribbon set between heavy balls."

That sounds painful.
 
2013-09-10 11:16:24 AM  
Can someone sum up for us paste-eaters?
 
2013-09-10 11:23:32 AM  

AngryDragon: Can someone sum up for us paste-eaters?


Two tests exist. Two results are found. There is no clear indication of which test is the more accurate of the two, and the results vary significantly from earlier runs of the same test.

Obviously this points to a flawed test, but as gravitons can't be detected by our own senses, it's rather difficult to develop a less-flawed test.
 
ZAZ [TotalFark]
2013-09-10 11:27:25 AM  
There was a similar discrepancy in measures of the Hubble constant until the 1990s, with two clusters of measurements around 50 and 90 km/s/Mpc (or similar values). Eventually astronomers decided to split the difference.
 
2013-09-10 11:32:53 AM  

ZAZ: G has dropped 21 parts per million in 12 years, giving the universe less than a million years to live. And here I thought we had billions until the big rip. It's been nice knowing (some of) you.


"with 27PPM standard uncertainty "

Like statistical polling, the numbers are up, but they could be down.
 
2013-09-10 11:37:48 AM  

AngryDragon: Can someone sum up for us paste-eaters?


G is a fudge factor that's used to make math involving gravity work.

The attractive force between two objects is equal to the mass of the two objects divided by the distance (squared) between them.  The more mass, they objects have, the more force, the more distance, the less force there is.

It's just there to make the numbers line up.  If kilograms (what we measure mass in) were a little more than twice as large as they are (or more precisely were equal to the square root of G times the current definition of a Kilogram) then the gravitational equation F = G(M1*M2)/D2 wouldn't need G because G would be 1.
 
2013-09-10 12:16:26 PM  
Not really constant if it's changing.
 
2013-09-10 12:21:57 PM  
That's heavy.
 
2013-09-10 12:55:13 PM  
It just means gravity is leaking over from the other branes.
 
2013-09-10 12:59:16 PM  
So, in my limited knowledge, the experiment was to measure G instead of g? And they have a means to do that?
 
2013-09-10 01:57:32 PM  
Wouldn't it be funny if the gravitational constant was not really a constant?

Good times
 
2013-09-10 02:17:28 PM  

Mr. Eugenides: It's just there to make the numbers line up.  If kilograms (what we measure mass in) were a little more than twice as large as they are (or more precisely were equal to the square root of G times the current definition of a Kilogram) then the gravitational equation F = G(M1*M2)/D2 wouldn't need G because G would be 1.


Yeah...no.  That's like saying that if only we put all units of distance in terms of pi then we would no longer have to worry about its pesky irrational nature.  Or, more analogously, if we only measured charge in units of inverse square Coulomb constants, then we wouldn't have to worry about that pesky constant determining the magnitude of force between two charged particles.  That's all great except that the only way to actually do that is to know what that constant is to begin with in order to make the conversion.  So you would still have to measure ke, or in this case, G.

Or maybe I just got trolled, in which case, good job.

simplicimus: So, in my limited knowledge, the experiment was to measure G instead of g? And they have a means to do that?


Yes, and it is at once both incredibly simple and incredibly tedious.  The http://en.wikipedia.org/wiki/Cavendish_experiment is one way mentioned in the article and can be performed in an undergraduate physics lab.  The trouble is it is extremely sensitive.  You have to set it up somewhere that it will absolutely not be disturbed, because even walking within ten feet of it will be enough to throw off the measurement due to the influence of your own gravitational field.  I managed to complete it and get within 10% of the accepted value of G which suitibly impressed my professor who normally discouraged students from attempting it because it is so difficult to perform outside of a completely controlled environment.
 
2013-09-10 02:23:17 PM  

StrangeQ: due to the influence of your own gravitational field


You're calling me fat, aren't you?
 
2013-09-10 02:36:51 PM  

StrangeQ: Yes, and it is at once both incredibly simple and incredibly tedious.  The http://en.wikipedia.org/wiki/Cavendish_experiment is one way mentioned in the article and can be performed in an undergraduate physics lab.  The trouble is it is extremely sensitive.  You have to set it up somewhere that it will absolutely not be disturbed, because even walking within ten feet of it will be enough to throw off the measurement due to the influence of your own gravitational field.  I managed to complete it and get within 10% of the accepted value of G which suitibly impressed my professor who normally discouraged students from attempting it because it is so difficult to perform outside of a completely controlled environment.


So, do you compensate for g or is it not a variable in the experiment?
 
2013-09-10 03:02:45 PM  

StrangeQ: Mr. Eugenides: It's just there to make the numbers line up. If kilograms (what we measure mass in) were a little more than twice as large as they are (or more precisely were equal to the square root of G times the current definition of a Kilogram) then the gravitational equation F = G(M1*M2)/D2 wouldn't need G because G would be 1.

Yeah...no. That's like saying that if only we put all units of distance in terms of pi then we would no longer have to worry about its pesky irrational nature. Or, more analogously, if we only measured charge in units of inverse square Coulomb constants, then we wouldn't have to worry about that pesky constant determining the magnitude of force between two charged particles. That's all great except that the only way to actually do that is to know what that constant is to begin with in order to make the conversion. So you would still have to measure ke, or in this case, G.

Or maybe I just got trolled, in which case, good job.


http://en.wikipedia.org/wiki/Natural_units
 
2013-09-10 03:05:26 PM  
So, then, we are to conclude that the G-spot still eludes the grasp of physicists?
 
2013-09-10 03:22:33 PM  

simplicimus: StrangeQ: Yes, and it is at once both incredibly simple and incredibly tedious.  The http://en.wikipedia.org/wiki/Cavendish_experiment is one way mentioned in the article and can be performed in an undergraduate physics lab.  The trouble is it is extremely sensitive.  You have to set it up somewhere that it will absolutely not be disturbed, because even walking within ten feet of it will be enough to throw off the measurement due to the influence of your own gravitational field.  I managed to complete it and get within 10% of the accepted value of G which suitibly impressed my professor who normally discouraged students from attempting it because it is so difficult to perform outside of a completely controlled environment.

So, do you compensate for g or is it not a variable in the experiment?


It's not a variable.  The balance rotates in a plane parallel to earth's surface.  Making sure everything is perfectly level is an essential step in the setup of the experiment.

Mr. Eugenides: http://en.wikipedia.org/wiki/Natural_units

"While this has the advantage of simplicity, there is a potential disadvantage in terms of loss of clarity and understanding, as these constants are then omitted from mathematical expressions of physical laws."


The constants still exist, you're just playing with the math to make the algebra easier.  It's the same reason we would often use G = c = 1 when going through spacetime tensor manipulations.  But to get a result meaningful to everyday experience you have to put them back in.  I could tell you it is .00001 seconds to the store with the convention of c = 1, but without also knowing that c = 3*108 m/s you would have no way of translating that time into a distance.
 
2013-09-10 04:24:09 PM  
So just change it back.
i1.ytimg.com
 
2013-09-10 05:32:38 PM  
Hmmm... What if both measurements were correct, and G is NOT a constant at all?
 
2013-09-10 06:02:26 PM  
Got some weed from an O.G. and now I'm higher than expected.
 
2013-09-10 07:19:07 PM  

washington-babylon: Hmmm... What if both measurements were correct, and G is NOT a constant at all?


What if it's not Constant because the Milky Way is in a bubble? Forget the fark thread.
 
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