Slashdot Mirror
Physicists Measure Gravity With Record Precision (gizmodo.com)
An anonymous reader quotes a report from Gizmodo: A team of scientists in China are reporting that they have now performed the most precise measurement of gravity's strength yet by measuring G, the Newtonian or universal gravitational constant. G relates the gravitational attraction between two objects to their masses and the distance between them. The new measurement is important both for high-powered atomic clocks as well as the study of the universe, earth science, or any kind of science that relies on gravity in some way. The values measured by the team "have the smallest uncertainties reported until now," according to the paper published in Nature.
In the new study, scientists performed two independent calculations of G using a pair of pendulums in a vacuum, one pendulum setup for each test. Each pendulum swings back and forth between a pair of massive objects whose positions can be adjusted. The pendulums measure the force of gravity in two ways. First, they measure the difference between how quickly the pendulum swings to the "near," or parallel position, versus the "far," or horizontal position. They also measure how the direction of the pendulum's swing changes based on the pull of the test masses. The researchers ended up measuring 6.674184 and 6.674484 hundred billionths (10-11) for the time-of-swinging and angular acceleration methods, respectively. These measures were both very precise, but are still different from one another for unknown reasons. This might have had something to do with the string used for the pendulum. The paper's reviewer, Stephan Schlamminger from the National Institute of Standards and Technology, wrote in a commentary: "Li et al. carried out their experiments with great care and gave a detailed description of their work. The study is an example of excellent craftsmanship in precision measurements. However, the true value of G remains unclear. Various determinations of G that have been made over the past 40 years have a wide spread of values. Although some of the individual relative uncertainties are of the order of 10 parts per million, the difference between the smallest and largest values is about 500 parts per million."
In the new study, scientists performed two independent calculations of G using a pair of pendulums in a vacuum, one pendulum setup for each test. Each pendulum swings back and forth between a pair of massive objects whose positions can be adjusted. The pendulums measure the force of gravity in two ways. First, they measure the difference between how quickly the pendulum swings to the "near," or parallel position, versus the "far," or horizontal position. They also measure how the direction of the pendulum's swing changes based on the pull of the test masses. The researchers ended up measuring 6.674184 and 6.674484 hundred billionths (10-11) for the time-of-swinging and angular acceleration methods, respectively. These measures were both very precise, but are still different from one another for unknown reasons. This might have had something to do with the string used for the pendulum. The paper's reviewer, Stephan Schlamminger from the National Institute of Standards and Technology, wrote in a commentary: "Li et al. carried out their experiments with great care and gave a detailed description of their work. The study is an example of excellent craftsmanship in precision measurements. However, the true value of G remains unclear. Various determinations of G that have been made over the past 40 years have a wide spread of values. Although some of the individual relative uncertainties are of the order of 10 parts per million, the difference between the smallest and largest values is about 500 parts per million."
Seriously. Low density analog information stored by scratching a fragile material and readable only with special equipment. Records are terrible and our future will be better without them.
This is pure G whizzardry!
105f here at 5 pm... later,, folks gathered on the beach to watch the sunset being sprayed over... some still call this 'weather',, around 65f now... truth+mercy=justice,, in the moms we trust..
Gravity is inside of an object. Itâ(TM)s the objects desire to move downward, it is not a force that pulls an object downward
Fake news, gravity doesn't exist, it's just electromagnetic forces being confused as something else. If the electron exists as we believe, it is what causes everything to exist. Side note, vacuums are not real.
I win! What do I win? 1 G?
105f here at 5 pm... later,, folks gathered on the beach to watch the sunset being sprayed over... some still call this 'weather',, around 65f now... truth+mercy=justice,, in the moms we trust..
^ This is your brain on drugs ...
They are still copying, they didn't invent G.
America #1 America #1
Would it be too much to ask that the bragged about more accurate value is actually mentioned in the summary?
Whenever "A team of scientists in China" appears LIES FOLLOW
Nothing from China can be trusted.
Simple question,
Why does gravity scale with mass? It's awfully coincidental isn't it?
That a property of matter (QUANTITY) scales with a force (GRAVITY). The more stuff, the stronger the gravity.
And when the two depart, we decide its no longer matter (e.g. PHOTON), create a new energy type (ELECTROMAGNETIC) and do complicated workarounds to explain how it still bends under gravity.
What if... the property of 'matter' (mass) isn't the measure of the quantity of stuff, its the net effect of the way the stuff is organized and the quantity of stuff. A photon is just a different organization of the stuff of matter it came from. An organization with a lower binding force than when it was a particle, and thus a lower 'gravity. What if there is only one energy, a derivative of binding force, not mass.
You might be inclined not to question the relationship between matter and gravity, but you should. A photon must be the same stuff as the matter it came from, so mass as a measure of the quantity of that stuff needs to be re-examined.
Wouldn't the motion of the pendulum in vacuum be retarded by friction with the ether?
These measures were both very precise, but are still different from one another for unknown reasons.
Also, precision is not accuracy.
Rough English translation: "Those who measure measure crap". Doing good measurements is difficult and you learn a lot refining your methods. You may also find effects you did not expect. That is why Physicists actually highly respect those that seem to do nothing than refine some measurement. It is effort well spent.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
But where is the anti-Trump angle? How is slashdot going to get their ad impressions without the 30th Trump argument since Saturday?
Goddamn guys. I have been here for nearly 20 years following the slide into obscurity and only in the last couple days have learned firsthand why people shitpost before they leave.
It's constant anger, irrationality, denial or warping of reality to suit preference over and over and over. So much so that when a story comes up without the nonsensical hatred, it's striking.
Why do any of us still go to this site aside from habit? There is no value here.
Trumpity Trump.
China steals everything and got away with it.
This time, the embolden China has stolen GRAVITY from poor Uncle Sam.
Paging Donald Trump --- Better do something, NOW !!
I know that proverb as well, but the first two "mist"s have to be written "misst":
http://canoo.net/inflection/messen:V:haben
It's actually quite interesting how the force required to accelerate one kilogram at 9.8m/s^2 is the same force required to keep it stationary under standard earth gravity whose free fall acceleration is (9.8m/s^2). The idea that they could be identical and indistinguishable is a significant part of what led Einstein to develop relativity. It seems simple, on one hand due the same force being applied, but to realize a theory relating accelerating reference frames would then also be a working theory of gravity was revolutionary. Its always bothered me that the majority of constants, like big G, must be measured and not derived, perhaps with enough precision measurement and enough eyes on it someone or some group will find a way to derive them with a unified theory. Until then, minor discrepancies can be quite interesting and provide valuable insight.
What is a high-powered atomic clocks? Why does it need power if it works on radioactive decay? And how does more power help for these kinds of clocks?
There seems to be some confusion over them. Since they're impacted by G and since you need them to measure G, they're an important part of the story.
https://www.newscientist.com/a...
https://www.sciencealert.com/p...
Basically, they work off state changes. Caesium atoms that generated pulses of radiation as they changed energy level, the wobble of aluminium atoms, the motion in a quantum gas of strontium.
They do not, and never have, work(ed) from radioactive decay.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
They dropped a Golden Delicious, because the old variant Newton used is difficult to find.
Pi is 3.
|burtosis said: Its always bothered me that the majority of constants, like big G, must be measured and not derived...
Hypotheses non fingo
I have not as yet been able to discover the reason for these properties of gravity from phenomena, and I do not feign hypotheses. For whatever is not deduced from the phenomena must be called a hypothesis; and hypotheses, whether metaphysical or physical, or based on occult qualities, or mechanical, have no place in experimental philosophy. In this philosophy particular propositions are inferred from the phenomena, and afterwards rendered general by induction.
His critics went so far as to suggest his calculation for G was based on occult numerology because Newton was likely a savant and inexhaustibly explored patterns of all types and kinds.
Would were! Should is! Could be! And live a hundred times three.
Although some of the individual relative uncertainties are of the order of 10 parts per million, the difference between the smallest and largest values is about 500 parts per million."
Do any of these experiments keep running for a long period of time? Years for example, continually taking measurements.
I am not suggesting that G does change, but to just assume it is a constant could be a gap in our complete understanding of the concept.
politicians are like babies' nappies: they should both be changed regularly and for the same reasons
So Newton managed to get his name used for the unit of force, Joule for energy, etc. They at most one unit each. Until Planck comes along and somehow gets his name stamped on units for length, mass, time and according wikipedia pretty much all the others too. The man's a branding genius!
It is not difficult to find a cutting of the apple variety that inspired Newton.
The real problem for commercial growers, however, is that the darned thing keeps dropping its apples . . .
what a farce, we measured something there are differences can't be explained lets call it hmmm let me think I need a letter hmmm how about G its really accurate and validates a "theory". Use your higher mind this is all nonsense.
While graviton fields are conservative, they are not uniform at all. The discrepancy can be easily explained by the existence of nearby massive objects that are not creating a completely uniform, symmetric field with respect to the experiment.
I would think the presence of the Sun or Moon could easily sway the readings on the order of 10^-12 in such an experiment.
Except that this is really a bit of a crap measurement so far. The large discrepancy between the two measured values means that neither can be trusted with much accuracy. If you take the difference between the two values as due to an unknown systematic error, which seems likely, then the uncertainty you get (500 ppm) is MUCH larger than the currently quoted uncertainty on G which is 46 ppm.
While the individual measurements may be very precise the clear systematic difference between the two means that neither is very accurate. Until they identify and fix the source of this systematic difference the measurement is worse than the one we currently have.
Photons do have mass and both cause gravity and are affected by gravity.
Photons do not have a mass. If they did then the EM force would be short range like the weak force (whose bosons do have mass).
Photons don't come from matter unless antimatter is involved.
Have a look up in the sky (provided you are not in the UK or Seattle). See that bright shiny thing there? That's the sun. Notice how it is emitting photons? There is no antimatter involved. It emits photons because it is really hot, just like old incandescent light bulbs (they did not use antimatter either!).
Five hundred parts per million. Hundred billionths. Ten parts per million.
In the following years, researchers would invent a clear and compact way of representing these numbers.
If you can't explain why pendulums swing differently during a solar eclipse, you're not done.
For this reason, God sends them a powerful delusion so that they will believe the lie.
Energeian Planes!
Well, given that most of the experiments prepared to measure it never discovered anything (including the most ambitious one in 1999)... it's difficult to explain something for what you do not have measurements, for what we know it's not happening at all.
It is out there if you look for it, especially if you read French.
Or, you can see it, in the anomalous red and blurred inner edges of the moon during the solar eclipse.
https://www.nasa.gov/feature/goddard/2018/how-scientists-predicted-corona-s-appearance-during-aug-21-2017-total-solar-eclipse
https://vimeo.com/230976895
The powerful delusion can be further detected in the seasonal changing of sunlight, particularly the winter sunlight. You find it when you realize the lie in the widespread belief that the 'tilt' or 'angle' of the sun is the reason for the change. When you realize the word planet comes from the same old greek root for planes.
Only photons at rest have no mass....All photons we know of have energy and thus mass.
You cannot have both! Mass is a Lorentz invariant i.e. it is exactly the same in all inertial reference frames. If a photon at rest has no mass then it must have zero mass at any energy. Just because a particle has energy does not mean it has any mass because the energy can be kinetic energy instead of mass-energy. Mass is literally the energy of the particle when it is a rest and, as you point out, a photon at rest would have no energy and hence no mass.
According to Bloomberg, citing people with knowledge of the deal, Google purchased "a stockpile of Mastercard transactions" that allowed Google advertisers to see whether the ads they ran online led to a sale at a physical store in the U.S. This arrangement was never shared with the public. From the report:
Well, "Doh!", it took me about 3 minutes once I'd downloaded the paper (using my OpenAthens login via my professional body) to establish that in one of the two experiments (time-of-swing) they used a fused silica "piece of string", and in the other (angular-acceleration-feedback) they used a tungsten "piece of string". There were other treatments (e.g. a conductive germanium-bismuth coating on the silica fibres to reduce noise from stray electric charge on the suspension fibre.
That such a vital part of the experimental forms differs is ... well, it's an obvious target to change when addressing the question of "why do the values from the two machines and methods differ?" I'd need to do more than a 3 minute scan of the paper (and Extended Data) to try to work out why they chose these two designs, but I think that'd be a damned good place to start.
I note that their "Quality" factor for their silica fibres is higher than for their tungsten fibres. So they must have damned good reasons for using the tungsten. Also, Cavendish (who developed this method - it's good to see a 1798 paper being referenced 220 years later) used fused silica suspensory wires, again suggesting there is a damned good reason to use Tungsten in one of the apparati .
Gizmodo - a "piece of string"? Really. Is this the level of popular science reporting in the US? I'm so glad I don't waste reading time on it. In fact, I think the only time I see it mentioned is here.
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"