Gravitation constant G can vary 0.1% in 6 years

[acsinuk]

The article in physics.org http://phys.org/news/2015-04-gravitational-constant-vary.html indicates that even G varies and this can be because the length of our day can also vary which can also vary the atomic decay rates. But if our planets rotation varies 0.1% then our time varies as well.

So is the speed of light constant or is it related to magnetic spin time of our solar sun?

[Strange]

The article in physics.org http://phys.org/news/2015-04-gravitational-constant-vary.html

 

"404 Error - The Page Cannot be Found"

 

http://phys.org/news/2015-04-gravitational-constant-vary.html

 

indicates that even G varies and this can be because the length of our day can also vary

 

May be related to the variation of length of day.

 

which can also vary the atomic decay rates.

 

Where does it say that?

 

But if our planets rotation varies 0.1% then our time varies as well.

 

We no longer use the rotation of the Earth as a reference for time.

 

So is the speed of light constant or is it related to magnetic spin time of our solar sun?

 

It is a constant, unrelated to the rotation of the Earth.

But it is an interesting article.

[swansont]

"they cautiously suggest that the "least unlikely" explanation may involve circulating currents in the Earth's core. The changing currents may modify Earth's rotational inertia, affecting LOD, and be accompanied by density variations, affecting G."

 

Uncompensated-for density variations will affect the measurement of G, but not G itself. They state that properly elsewhere in the article — they are not proposing that G itself varies.

 

I also question the "almost perfect correlation" claim, when there are three notable outliers (two of which are almost perfectly anti-correlated)

[Strange]

 

Uncompensated-for density variations will affect the measurement of G, but not G itself

 

I noticed that too. I put it down to sloppy writing.

[fiveworlds]

The article in physics.org http://phys.org/news/2015-04-gravitational-constant-vary.html indicates that even G varies and this can be because the length of our day can also vary which can also vary the atomic decay rates. But if our planets rotation varies 0.1% then our time varies as well.

So is the speed of light constant or is it related to magnetic spin time of our solar sun?

 

 

I actually saw the lecture on facebook. He takes the absolute piss because he has a load of old physics books and preety much everything has changed over time. He also said that the speed of light has dropped by 20 metres per second.

Edited August 18, 2015 by fiveworlds

[swansont]

 

I actually saw the lecture on facebook. He takes the absolute piss because he has a load of old physics books and preety much everything has changed over time. He also said that the speed of light has dropped by 20 metres per second.

 

Who has claimed this?

[fiveworlds]

Who has claimed this?

 

Had to find it his name is Rupert Sheldrake this is the video

 

[Strange]

How can you confuse that crank with real science?

[John Cuthber]

Someone would have noticed. I'd cite this as probably the world's most famous piece of equipment that would have demonstrated such a change if it had taken place.

https://en.wikipedia.org/wiki/Big_Ben#Clock

[swansont]

Had to find it his name is Rupert Sheldrake this is the video

 

 

And? How much credibility do you assign to a random crank on youtube?

[acsinuk]

Ruperts TED was interesting because what we want from physicists is facts not assumptions and averages. BTW the variation in G according to the original article is percent 10^-4 which is really tiny.

However, the Essen clock is claimed by some to be one second in 300 years accurate which is a totally unrealistic claim if in fact the time base of our planet rotation changes, for whatever reason, or which could be due to a change in the suns velocity around the magnetic hub at the centre of our galaxy. Either of these events would change time and constant G.

Edited August 20, 2015 by acsinuk

[swansont]

Ruperts TED was interesting because what we want from physicists is facts not assumptions and averages. BTW the variation in G according to the original article is percent 10^-4 which is really tiny.

However, the Essen clock is claimed by some to be one second in 300 years accurate which is a totally unrealistic claim if in fact the time base of our planet rotation changes, for whatever reason, or which could be due to a change in the suns velocity around the magnetic hub at the centre of our galaxy. Either of these events would change time and constant G.

 

Our time has not been based on planet rotation for several decades now, something Strange pointed out in post #2. And by modern standards the Essen clock is pretty lousy at 1 sec in 300 years. That's only a part in 10^10. The best modern clocks (specifically, my clocks) are about 6 orders of magnitude better in timekeeping.

 

Nothing about these effect would change time or G. There's nothing in the article that suggest G is changing; what is discussed is that the measurement (or some kinds of measurement) appears to be changing.

[acsinuk]

What we need is better data. If we have several labs in different countries all checking G daily at the same time then we will be able compare the results and see any variations that occur.

[swansont]

What we need is better data. If we have several labs in different countries all checking G daily at the same time then we will be able compare the results and see any variations that occur.

 

Nobody would pay for that, and I'm not even sure you can do a daily measurement at the precision they report.

[John Cuthber]

They used to.

These were used in astronomical observatories round the world and we would have noticed if they didn't agree.

 

https://en.wikipedia.org/wiki/Shortt-Synchronome_clock

[swansont]

They used to.

These were used in astronomical observatories round the world and we would have noticed if they didn't agree.

 

https://en.wikipedia.org/wiki/Shortt-Synchronome_clock

How were these measuring G?

 

Edit: and I doubt we would have noticed if they didn't agree by small amounts. The ways of comparing distant clocks was limited back when Shortt and Riefler clocks were state-of-the-art.

[fiveworlds]

And? How much credibility do you assign to a random crank on youtube?

 

None they could be anyone.I suppose it depends on who they were. If it were barack obama I might read it

[Strange]

They used to.

These were used in astronomical observatories round the world and we would have noticed if they didn't agree.

 

https://en.wikipedia.org/wiki/Shortt-Synchronome_clock

 

Even if they were affected by changing G, they would all be affected in the same way and so no one would notice.

[John Cuthber]

How were these measuring G?

 

By relying on g.

 

0.1% isn't a small amount;

 

If,on the other hand it's claimed that the effect wound be undetectable because all means toe measure time would s be affected in the same way , then it' not clear that this is science.

 

I'm amused to be discussing this with someone who keeps a tally of time to 14 digits or so as " the day job"

.

[swansont]

By relying on g.

 

0.1% isn't a small amount;

 

If,on the other hand it's claimed that the effect wound be undetectable because all means toe measure time would s be affected in the same way , then it' not clear that this is science.

 

I'm amused to be discussing this with someone who keeps a tally of time to 14 digits or so as " the day job"

.

g can vary without G varying, via changes in the mass distribution and r. The spatial variation of g was the reason why the meter wasn't defined by a pendulum. But g varies through the course of the day (and has longer period variations as well) even in a fixed location.

 

You can use a pendulum to measure G itself, by moving known test masses around nearby. (I saw a set up in Andrea De Marchi's lab years ago http://iopscience.iop.org/0026-1394/46/1/015/) But that requires a lot of statistics, so it's probably not going to be done in a day.

[John Cuthber]

The spatial variation of g is big, but, once you build an observatory and bolt a clock to the wall, the temporal variation in g is small.

If the pendulum clock keeps track with the rotation of the earth (as measured by the apparent motion of the stars) then the clock must be keeping good time.

If either g or G varied then the clocks wouldn't work and people would notice.

[swansont]

The spatial variation of g is big, but, once you build an observatory and bolt a clock to the wall, the temporal variation in g is small.

If the pendulum clock keeps track with the rotation of the earth (as measured by the apparent motion of the stars) then the clock must be keeping good time.

If either g or G varied then the clocks wouldn't work and people would notice.

 

People did notice. They reset their clocks, just like people used to do until technology came along and did it automatically.

 

But if g changed slightly, all of the clocks would be affected. What if your clock was running a little slow and it was offset by the earth's tidal slowdown? You'd never know. And, of course we didn't notice that until relatively recently.

 

0.3 second per year is about 1 x 10^-8 stability. But that's only a millisecond per day. Are you going to notice that change in rotation on a daily basis?

 

https://books.google.com/books?id=AIAjKi5RaBQC&pg=PA15&lpg=PA15&dq=original+clock+measurement+earth+slowing+down&source=bl&ots=WWgOOcQlne&sig=EJ09627YGSxJs_BET9fpGc4mS-k&hl=en&sa=X&ved=0CDgQ6AEwBGoVChMInfbu3MW9xwIVhtk-Ch1Urgia#v=onepage&q=original%20clock%20measurement%20earth%20slowing%20down&f=false

 

This implies that the changes were observed over longer times, but that such variations were observed when atomic clocks were introduced. That there are fluctuations and variations is why mean solar time was used.

[John Cuthber]

Once again, I raise the big Ben clock as evidence

https://en.wikipedia.org/wiki/Big_Ben#Clock

". On top of the pendulum is a small stack of old penny coins; these are to adjust the time of the clock. Adding a coin has the effect of minutely lifting the position of the pendulum's centre of mass, reducing the effective length of the pendulum rod and hence increasing the rate at which the pendulum swings. Adding or removing a penny will change the clock's speed by 0.4 seconds per day"

if the error over the century and a half or so is of the order of a "small pile" of coins added to a 300kg, 4 metre pendulum then it's not 0.1% in any 6 year period.

 

And your question "0.3 second per year is about 1 x 10^-8 stability. But that's only a millisecond per day. Are you going to notice that change in rotation on a daily basis?" misses the point.

Nobody would notice it on a daily basis, but that wasn't the topic. They would notice an error of 11 minutes at the end of six years.

Obviously, if they kept "tweaking" the clocks so they ran in synch with the stars then they wouldn't spot it (unless they kept a record of how much they needed to tweak it - and I bet they would have).

But the point of the Shortt clock was that you didn't keep tweaking it because you didn't need to.

They ran to about a second a year. They were the first clocks that told the world that the earth's rotation wasn't constant.

They were accurate enough to show up an error of 0.1% in 6 years easily.

Edited August 23, 2015 by John Cuthber

[Strange]

John, rather than talking about clocks and things, why not address the science in the OP?

[swansont]

And your question "0.3 second per year is about 1 x 10^-8 stability. But that's only a millisecond per day. Are you going to notice that change in rotation on a daily basis?" misses the point.

Nobody would notice it on a daily basis, but that wasn't the topic.

 

No, that was exactly the topic. (emphasis added)

 

What we need is better data. If we have several labs in different countries all checking G daily at the same time then we will be able compare the results and see any variations that occur.

 

It's not even doing it with a day's worth of data, acsinuk is suggesting an instantaneous measurement, which is a non-starter.