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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."
Your mama's so fat, she emits Hawking radiation.
Einstein agreed that gravity was not a force. He noticed that it was directly proportional to mass just like fictitious forces were.
As for the being inside an object and desire to move downward, those don't seem like testable hypotheses.
Correct, in the same sense that an object's desire to release phlogiston causes it to catch fire.
Not quite right. There are a few different models of gravity, but the most accepted is Einstein's interpretation, that what perceive as gravity is the warping of space-time caused by mass. In essence, the greater mass an object has the more the straight line paths of the universe curve inward towards it. An equally valid mathematical model (but less generally accepted interpretation), is that there is a fundamental field, much like the electromagnetic field, that has directions and imparts momentum where the direction and intensity is based on the presence of mass in an area.
Downward?
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.
They are, but c'mon, it's lifted from a Gizmodo article. Do you read Gizmodo for anything even remotely scientific?
In Nature it says...
We obtain G values of 6.674184×10^-11 and 6.674484×10^-11 cubic metres per kilogram per second squared, with relative standard uncertainties of 11.64 and 11.61 parts per million, respectively.
Thanks for this... my daughter has officially added this to her arsenal of mamma jokes that only a handful of people understand.
I will admit though, she already had :
"Your mamma's so fat that her spiritual guide refers to her aura as an event horizon"
I know that proverb as well, but the first two "mist"s have to be written "misst":
http://canoo.net/inflection/messen:V:haben
Einstein noticed the coincidence a long time ago.
Photons do have mass and both cause gravity and are affected by gravity.
Photons don't come from matter unless antimatter is involved. Usually photons are converted to or from kinetic energy (which also increases mass).
Most mass is already known to be kinetic energy or binding energy. Allegedly for a hydrogen atom only around 2% of the mass is rest mass and the remainder is due to kinetic energy or gluons.
A photon must be the same stuff as the matter it came from
Why? You can't tell people to question things, then turn around and immediately try to dictate physics by fiat with a "must" premise.
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.
It is a fascinating study in methods and thinking of the Trump trolls that in a story's comments section where there has not been one single mention of Trump, the very first mention of Trump is in a comment complaining about how there are nothing but Trump comments. Now, it's late here out West and maybe I'm too tired to notice that this is a bot's post, but for heaven's sake, if that's the case, the algorithm needs some adjustment.
And if the comment is sincere and by an actual human, your wish is my command, so:
Trump is so fat that gravity's going to pull him straight to prison. Now are you happy? See what you made me do? I'm not proud of it, but I feel a certain responsibility when someone makes a request for an anti-Trump angle.
You are welcome on my lawn.
How do you explain a helium balloon's desire to move upward?
Well, it's got Helium inside instead of gravity. Duh.
If any of these forces could explain gravity, it would be unified by now.
That's how we have the electroweak force. We do not have the electrogravitational force.
Gravity cannot be unified with the other forces with standard physics. We know this. It requires superstrings or other new physics. And even then nobody actually has a grand unified theory.
Anyone on Slashdot who claims otherwise had best produce the Nobel prize in physics and Fields medal in mathematics, because it's going to require just as many discoveries there.
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)
6.674184×10^-11 and 6.674484×10^-11
This kind of cryptic number stuff isn't suitable for a mainstream news site like this.
CLI paste? paste.pr0.tips!
It doesn't work off radioactive decay. It works off the spin of ultra-cooled atoms.
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)
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)
The problem is that quantum gravity and relativistic gravity can't be reconciled. Only one of these can be correct, at most. The other must be false. They cannot be reconciled.
If QM gravity is false, QM is false.
If relativistic gravity is false, relativity is false.
Both underlying theories have stood up to every test thrown at them, but one of them is wrong.
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)
That is true. If and only if QM is false. QM specifically prohibits any such interpretation, which causes a severe problem.
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)
Electrons exist. So do positions. So do all other leptons. This suggests gravitons also exist.
You cannot convert an electron into any other fundamental particle. They explain nothing other than themselves.
If a Grand Unified Theory exists, it will use quantum loops or membranes, not electrons.
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)
I dunno, Slashdot does a lot with cryptographic numbers. There are articles on them regularly. It's just some are ROT13ed into articles about something else.
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)
Think quantum gravity.
Gravity is the exchange of particles between two particles.
If you double the particles, you double the exchanges. Scaling.
Where's the shock?
If you prefer relativity, mass bends space. Space can be thought of as having elasticity, although that's not quite right.
Then it's just a matter of applying Hooke's Law. Double the mass, double the bending. Again, scaling.
I don't see coincidence, I see cause and effect.
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)
There is no ether.
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.
Tea is from China and Tea is the drink of the gods, second only to mead.
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)
The average friction has to be zero, because the quantum foam averages for any value over any scale to zero. The particles in it are a product of statistical noise.
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)
|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!
Electrons exist. So do positions. So do all other leptons.
Remember a world without autocorrect? Peppermint Farm remembers.
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 . . .
The problem is that quantum gravity and relativistic gravity can't be reconciled. Only one of these can be correct, at most. The other must be false. They cannot be reconciled.
If QM gravity is false, QM is false.
If relativistic gravity is false, relativity is false.
Both underlying theories have stood up to every test thrown at them, but one of them is wrong.
I don't think so. They may just be looking a different things and a "higher order" theory is needed to reconcile them. My example would be the wave vs. particle nature of light. They are both correct sort of, and both false, sort of.
6.674184×10^-11 and 6.674484×10^-11
This kind of cryptic number stuff isn't suitable for a mainstream news site like this.
Those are not as accurate as they are precise. If they were, they would be identical.
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.
If any of these forces could explain gravity, it would be unified by now.
That is simply not true. Gravity becomes as strong as the other forces are energies of 10^18 GeV (or about 100 million million times higher in energy than the LHC). We have literally no idea what physics goes on at that energy scale and it might well be possible that there is a single, unified force of which gravity is one aspect.
The incredible weakness of gravity (it is MUCH weaker than the weak force) means that we know almost nothing about its fundamental nature at the moment. We don't even have a working, testable theory yet.
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!).
Is this rambling available in English?
We used to have a Bill of Rights. Now, with the rights gone, all we have left is the bill.
Ether was decommissioned in 1897 due to budget cuts, don't worry.
We used to have a Bill of Rights. Now, with the rights gone, all we have left is the bill.
Your mama's so fat she doesn't emit Hawking radiation anymore.
Ezekiel 23:20
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.
Solved!
QM + R = G
-- Each tock of the Planck clock is a new world and here we are still life. --
Electrons exist, for some uncertain definition of existence.
I've been through the data and the answer is obvious: someone wrote a 1 instead of a 4 or possibly (following Heisenberg) vice versa.
Yo Mama' so fat, they have to use the Large Hadron Collider to measure the mass of her atoms.
-==- Buy a Mac and leave me alone!
I have no problem with a grand unified theory. I have a problem with it being based on the electron, which exhibits none of the behaviour you describe.
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)
In QM, gravity is transmitted by gravitons. It is key to the theory that all forces are handled by particle exchange.
There is no quantum gravity theory, per second, only the requirement of gravitons as a particle grouped with other leptons. This is part of the standard model. You will find gravitons in the particle zoo.
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)
Perhaps we should replace all Yo Mama' so fat with Trump is so fat or stupid jokes? /me runs and hides
Oh, I hit a nerve on some people I guess!
Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
They have mass, energy, spin, charge.
Now, how we define "exist" is a bit more ambiguous. I rather like the idea that the physical universe is emergent and a product of mathematics. "Exist" in this sense still means physical, it just means we have to be cautious if we examine closer than that.
I also like M-Theory, where electrons are the protrusion of a single membrane into 4D spacetime. Again, the electrons still physically exist, but individual electrons don't exist in isolation.
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)
Gravitons are not affected by the Higgs field, and gravitons wouldn't emit gravitons so can't be affected by gravity themselves.
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)
I have no problem with a grand unified theory. I have a problem with it being based on the electron, which exhibits none of the behaviour you describe.
I never said that a GUT should be based on an electron - although it had better include it along with all the other fundamental particles otherwise it is wrong. What I was pointing out is that your assertion that "If any of these forces could explain gravity, it would be unified by now." is wrong. It is entirely possible (even likely) that there is a unified force which could explain both these forces and gravity that we do yet know about.
Question: Does mass reside within space time, or does it displace it?
Could gravity be a pull, or a push? Perhaps gravity is nothing more than a manifestation of mass and space/time fighting for displacing each other. Of course, I'm not a physicist; hence my question.
Life is not for the lazy.
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.
It's what the naughty kids use when they try to catch the Ether Bunny.
In theory, they should be identical. Which is what makes the difference interesting.
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"
No, because that would make it's incoherence even more obvious.
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"
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"