You don't have to understand it, you only have to google it - like wot I did!
The Odysseus lander "tipped over on touchdown".
https://www.bbc.co.uk/news/science-environment-68388695
The difference I see, is: The spinning bicycle wheel with masses induces an alternative gravity pull, while the Cavendish set up induces a static pull.
About the spinning wheel, it is said: "We demonstrate the detection of a 30 aN gravitational signal at 27 Hz." .
I presume they amplified this tiny signal with à narrow band amplifier centered at 27 Hz, an efficient way to reject much of the gravitational ambiant noise.
An "alternating gravity pull" would be a suitable interpretation of what the research paper describes as a "time dependent gravitational gradient".
The bicycle wheel must be in motion at the right frequency to create a gravitational resonance with the levitated particle (a tiny magnet), otherwise the generated electrical signal won’t be strong enough to be picked up.
I believe the ultimate idea is to scale down the rotating and levitated mass until the quantum world is reached on both sides.
The bicycle wheel must be in motion at the right frequency to create a gravitational resonance with the levitated particle (a tiny magnet), otherwise the generated electrical signal won’t be strong enough to be picked up.
I believe the ultimate idea is to scale down the rotating and levitated mass until the quantum world is reached on both sides.
I understand the wheel has regularly spaced quite large brass masses, it spins near the tiny mass under test. The tiny mass sees brass masses alternatively coming and leasing. It undergoes a 27 Hz alternating gravity force.
The work of art is not the lunar lander itself, but the 125 mini-sculptures of the Moon which it carried.
Called “Moon Phases,” they show 62 phases of the moon as seen from Earth, 62 phases visible from other viewpoints in space, and one lunar eclipse.
It would appear that you did not read the article attached to my post.
Quotes from the linked article:In the following article, there's mention of the three equally spaced brass masses on the rim of the electric wheel driving a "27 Hz mode".
https://www.science.org/doi/10.1126/sciadv.adk2949
The objective is for the brass masses to gravitationally drive the motion of a tiny particle which is magnetically levitated.
"We demonstrate the detection of a 30 aN gravitational signal at 27 Hz." - That's the conclusion!
However, to me, the experimental manipulations are no more than gobbledygook.
That's one simple statement buried down in the article that IMHO could have been earlier, in a concise description of the setup. From this I presume the wheel is rotating at 9 revolutions per second, but suspecting the complexities of these things, please don't quote me on that.
But earlier, there's this:
Which is it, 2.45kg or 2.4kg? Now that I would know how to detect the difference in the particle's movement, but I think I could put these masses on a scale and detect which figure is more accurate.
I've highlighted and underlined what I regard to be two typos in the above sentence taken from the INTRODUCTION section of the article.
https://www.science.org/doi/10.1126/sciadv.adk2949
The figures (2.45 and 30) in the RESULTS section will be the correct ones and are the figures reported elsewhere.
P.S. If you want to be picky, look at the force noise unit, which is stated as fN/√Hz in the RESULTS and not fN/Hz as above.
Sloppy work in that INTRODUCTION section or wot?
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The challenge is to extract a signal from noise.
"giving a coupling of 1030 aN with a force noise of 0.5 fN/Hz ."
Should be 0.5 fN/sqrt(Hz).
fN is 10^ -15 Newton. ( femto )
aN is 10^ -18 Newton. ( atto )
I do not understand what is this "coupling".
I undertand the wheel moving quite large masses, the levitating tiny masse, but I do not understand how they pick up some signal.
"giving a coupling of 1030 aN with a force noise of 0.5 fN/Hz ."
Should be 0.5 fN/sqrt(Hz).
fN is 10^ -15 Newton. ( femto )
aN is 10^ -18 Newton. ( atto )
I do not understand what is this "coupling".
I undertand the wheel moving quite large masses, the levitating tiny masse, but I do not understand how they pick up some signal.
Now that I look, the lack of square root symbol has something to do with the copy/paste operation. If you look at the article, the stuff after the words "with a force noise of" correctly has the square root symbol (and it acts like an image or something, it doesn't get selected as does the text around it), but if you copy/paste it to a text editor as I did, there's no square root. I offhand don't know who or what to blame for that.
Hmm, are you not following the current conversation and what this article is about? The signal picked up by the smaller mass is due to a change in (looking up the title of this thread) the force of gravity it "feels" due to the larger masses varying their distances to it.
Yes, I had found by performing the act that the fN/Hz in the INTRODUCTION section was a copy and paste from the fN/√Hz in the RESULTS section.
Yes, how the signal is extracted is a mystery to me until I find out what a SQUID is!
Quote from article: "The motional state of the particle is read out by means of superconducting quantum interference device (SQUID) detection."
I feel a google coming on! https://www.techopedia.com/definition/15029/superconducting-quantum-interference-device-squid
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Gleaning some knowledge of what a SQUID is means I can begin to make sense of this description from the article (which I've simplified).
The motion of the (magnetic) particle results in a change of flux through a pick-up loop which is detected using a SQUID coupled inductively to the pick-up loop.
But to be honest, by this point I have lost interest!
The motion of the (magnetic) particle results in a change of flux through a pick-up loop which is detected using a SQUID coupled inductively to the pick-up loop.
But to be honest, by this point I have lost interest!
Wait a minute though!
A SQUID contains a Josephson junction, something I mentioned earlier in the thread.
Brian Josephson predicted the quantum tunneling effect involving superconducting currents, for which he was awarded the Nobel Prize in Physics.
https://en.wikipedia.org/wiki/Josephson_effect
A SQUID contains a Josephson junction, something I mentioned earlier in the thread.
Brian Josephson predicted the quantum tunneling effect involving superconducting currents, for which he was awarded the Nobel Prize in Physics.
https://en.wikipedia.org/wiki/Josephson_effect
@benb We have à misunderstanding about "signal pick up”. I mean "sensor".
In the Cavendish experiment the force is picked up by a torsion balance. The sensor is a wire that receives à torsion from the gravity force.
I do not see what picks up the force in the 27 Hz gravity experiment; What is the sensor of the force ?
In the Cavendish experiment the force is picked up by a torsion balance. The sensor is a wire that receives à torsion from the gravity force.
I do not see what picks up the force in the 27 Hz gravity experiment; What is the sensor of the force ?
Oh, (seeing Galu's answer) THAT's what you were asking, how the near-infinitesimal movement is detected electrically, not what it is measuring. Sorry about that.
I hadn't even read the SQUID part, I had assumed it was the usual electromagnetic coil, but no doubt the signal would be way down in the noise of even the coil's wire resistance.
I hadn't even read the SQUID part, I had assumed it was the usual electromagnetic coil, but no doubt the signal would be way down in the noise of even the coil's wire resistance.
Signals. Noise. Electro-magnetic coils. Measuring the almost infinitessimal.
One has to hope the simple field effects of whizzing large lumps of conductive, albeit non-magnetic, metallic alloy around have been properly accounted for, especially in close proximity to the coils of the motor in the electric bike wheel.
Maybe I shouldn't try to rationalise high-end-institution physics into my garage-workshop brain!
One has to hope the simple field effects of whizzing large lumps of conductive, albeit non-magnetic, metallic alloy around have been properly accounted for, especially in close proximity to the coils of the motor in the electric bike wheel.
Maybe I shouldn't try to rationalise high-end-institution physics into my garage-workshop brain!