Naked Science Forum

On the Lighter Side => That CAN'T be true! => Topic started by: alright1234 on 20/04/2019 23:16:37

Title: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 20/04/2019 23:16:37
 Cavendish's experimental apparatus uses two lead spheres m1  = 158 kg and m2  = .73 kg separated by the distance of .21 m that detects a force of 1.74 x 10−7 N (≃ 2μg ) which is too small to measure in 1797 which nullifies Cavendish's experiment.

Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Kryptid on 21/04/2019 06:13:38
What is your evidence? Please provide a reputable source to back it up.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: evan_au on 21/04/2019 11:26:45
The experiment certainly needed to be well-shielded from outside interference, and the very tiny oscillations (5mm) had to be viewed from a distance with a telescope.

Difficult, yes; but which part of the experiment do you suggest is impossible?
And then why did more sensitive recent techniques confirm his results (after an arithmetic error was corrected...).
See: https://en.wikipedia.org/wiki/Cavendish_experiment#The_experiment
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alancalverd on 21/04/2019 12:49:45
Worth reading Cavendish's experimental method carefully. The torsion balance is a neat trick for applying or measuring very small forces, and in the event he only needed to measure a distance of about 4 mm, slightly complicated by the fact that the torsion rod was oscillating with a period of about 20 minutes, but no big deal in the 18th century when good telescopes and vernier scales were an everyday part of navigation equipment and there was no heavy traffic in the vicinity.

Cavendish was an experimental genius (as becomes all Peterhouse men) who also discovered hydrogen and used a null experiment to demonstrate the inverse square law of electrostatics.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 23/04/2019 14:59:03
Cavendish's experimental apparatus uses two lead spheres m1  = 158 kg and m2  = .73 kg separated by the distance of .21 m that detects a force of 1.74 x 10−7 N (≃ 2μg ) which is too small to measure in 1797 which nullifies Cavendish's experiment.


The problem seems to be that Cavendish was much cleverer than you.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 24/04/2019 20:53:03
What is your evidence? Please provide a reputable source to back it up.

The most accurate weight measurement devise in 1797 was a balance beam that has an measurement uncertainty of approximately 1 mg.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 24/04/2019 21:00:18
What is your evidence? Please provide a reputable source to back it up.

The most accurate weight measurement devise in 1797 was a balance beam that has an measurement uncertainty of approximately 1 mg.
Did you write that yourself?

It certainly isn't a reputable source.
You don't say where it's from.

In any event, clever people worked out that the 2g isn't a weight.
So what you wrote is irrelevant.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alancalverd on 24/04/2019 21:07:51
What is your evidence? Please provide a reputable source to back it up.

The most accurate weight measurement devise in 1797 was a balance beam that has an measurement uncertainty of approximately 1 mg.
Quite possibly, but Cavendish wasn't worried about milligram uncertainty of his test masses. Weighing dense metals to +/- 1% in the kilogram range certainly wasn't a problem. 
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 27/04/2019 00:00:13
In any event, clever people worked out that the 2g isn't a weight.

If 2g is not a weight (force) than what is it?
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 27/04/2019 00:01:26
If 2g is not a weight (force) than what is it?
Not all forces are weights.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 27/04/2019 00:17:54
To test Cavendish's experiment, Cavendish's .73 kg lead sphere is suspended using a thin titanium wire and place .01 mm from Cavendish's larger lead sphere (158 kg). A laser is used to detect the change in the angle of the wire that is suspending the .73 kg lead sphere (fig 32a,b). As the 158 kg lead sphere is slowly rolled away from the smaller .73 kg suspended lead sphere no measurable change in the angle of the wire is observed which nullifies Cavendish's experiment.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 27/04/2019 00:24:58
To test Cavendish's experiment, Cavendish's .73 kg lead sphere is suspended using a thin titanium wire and place .01 mm from Cavendish's larger lead sphere (158 kg). A laser is used to detect the change in the angle of the wire that is suspending the .73 kg lead sphere (fig 32a,b). As the 158 kg lead sphere is slowly rolled away from the smaller .73 kg suspended lead sphere no measurable change in the angle of the wire is observed which nullifies Cavendish's experiment.
Why did you post that meaningless dross?
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 27/04/2019 00:29:09
The experiment certainly needed to be well-shielded from outside interference, and the very tiny oscillations (5mm) had to be viewed from a distance with a telescope.

Difficult, yes; but which part of the experiment do you suggest is impossible?
And then why did more sensitive recent techniques confirm his results (after an arithmetic error was corrected...).
See: https://en.wikipedia.org/wiki/Cavendish_experiment#The_experiment

Cavendish did his experiment outdoors in a old brick outhouse without heating. The question is not if Cavendish experiment is valid now but in 1797 was it valid.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 27/04/2019 00:31:18
Cavendish did his experiment outdoors in a old brick outhouse
Which?
Outdoors, or in a building?

Do you realise that " without heating" removes thermal currents?
That's the best way to do it.
Did you not think that through?

Seriously, why are you even discussing this?
You clearly have no clue what you are on about.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 27/04/2019 00:38:18
in 1797 was it valid.
Yes.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 27/04/2019 02:29:28
In 1797, they could measure the force equivalent to a dust particle? Why do dust particle not stick to the side of a granite cliff.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 27/04/2019 11:51:56
In 1797, they could measure the force equivalent to a dust particle?
Yes. We know this because... Cavendish did it.
And just because you choose not to accept it, doesn't stop it being true.

Why do dust particle not stick to the side of a granite cliff.
I would assume that they do.
They certainly stick to the mirror in my bedroom.
I doubt the dust can tell the difference between one smooth silicate surface and another.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alancalverd on 27/04/2019 17:02:02
The force difference in the original Cavendish experiment was about 25 μg, not 2.

Cavendish actually set out to measure the mean density of the earth, following Maskeleyne's earlier measurement of the mean density of Schiehallion. So the precise measurement of small gravitational forces was a current matter of interest, not impossibility.

Given that the value of G calculated from Cavendish's results  is within 1% of the current consensus value, he was either incredibly lucky or an exceptional experimental scientist. In view of his discovery of hydrogen and the noble gases, and his proof of the inverse square law of electrostatics to better than 0.1%, I think the latter is the more probable.

What kind of idiot attempts to measure the angle of twist of a tungsten filament with a laser? The kind that thinks moving the large sphere will cause the small one to rotate. Gravity isn't like viscosity.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 27/04/2019 17:19:38
What kind of idiot attempts to measure the angle of twist of a tungsten filament with a laser?
The sort who thinks protons are not real
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 27/04/2019 21:43:38
Could a force (2 ug or so) equal to the weight of a single dust particle really twist and turn Cavendish's iron rod?
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 28/04/2019 09:39:44
Could a force (2 ug or so) equal to the weight of a single dust particle really twist and turn Cavendish's iron rod?
Of course it could.
Why would it not?
Someone clever enough to know what they are talking about could even calculate the angle it turns it through.
https://en.wikipedia.org/wiki/Torsion_constant
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 29/04/2019 19:16:57
Could a force (2 ug or so) equal to the weight of a single dust particle really twist and turn Cavendish's iron rod?
Of course it could.
Why would it not?
Someone clever enough to know what they are talking about could even calculate the angle it turns it through.
https://en.wikipedia.org/wiki/Torsion_constant

A force equivalent to a dust particle (2ug) probably would not twist and turn a string of dental floss.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 29/04/2019 19:22:00
A force equivalent to a dust particle (2ug) probably would not twist and turn a string of dental floss.
I gave you a reference earlier which lets you find out how far it would twist it (depending on other stuff like the length of the beam and the string + the stiffness of dental floss).

Why not calculate it?
(If you like, you can get a grown up to help you)

Just to help you out a bit, I weighed  5 metres of dental floss. It has an apparent mass of 0.42 grams.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 29/04/2019 19:32:36
I did this little thing to add to everything else. What do you think? I'm since working on it and will add some more as I am growing up.



Newton's gravity equation is applied to an astronaut with a mass of 50 kg in the space station that is 249 miles (400,727 m) from the surface of the earth. The distance r which represents the distance from the center of the earth to the space station is,


r = (earth's radius) + (height) = (6.371  x 106 m) + (.4  x 106 m) = 6.771  x 106 m.......................69


Using the distance for r (equ 70) in Newton's gravity equation forms,



F = (G m1 m2)/r2  = (6.7 10-11) x (50kg) x (6 x 1024kg) / (6.771  x 106m)2 ≃ 438.4 N or 44.7 kg.....................70


According to Newton's gravity equation, a 50 kg astronaut in the space station forms a 44.7 kg gravitational force pointed at the earth. The centripetal force CF is used to justify the weightlessness of an astronaut in the space station is calculated,


CF = mv2/r = (50 kg)(7672 m/s)2/ (6.771 x 106 m) = 437 N or 44.56 kg................................71


The gravitational and centripetal forces form an equilibrium that produces the massless astronaut yet when a force is applied to an astronaut outside the space space and the astronaut propagates at a velocity of 50 mph in the direction opposite to the angular velocity, the described astronaut does not propagate towards the earth which proves the gravitational and centripetal forces do not function for a 50 kg astronaut propagating around the earth. Also, the space stations is orbiting the earth at approximately 250 miles above the surface of the earth. The 450 ton space station cannot orbit the earth at a height of 1000 miles above the surface of the earth which proves the gravitational and centripetal forces do not function for the space station at the height of 1000 miles. In addition, the centripetal force for a 50 kg mass on the surface of the earth propagating around the Sun is calculated,


CF = mv2 /r = (50kg)(30,462 m/s)2 / (1.5 x 1011 m) = .31 N............................................................................72


At 12:00 am (midnight), the centripetal force produced by the 50 kg mass on the surface of the earth propagating around the Sun is .31 N pointed away from the earth which represents the decrease in the weight of the 50 kg mass yet at 12:00 am (noon) a .2908 N ( v = 29,648 m/s) centripetal force would be pointing in the direction of the earth that would represent a .6 N weight variation every 24 hours which are not experimentally observe and proves the centripetal force does not function for a 50 kg mass on the surface of the earth propagating around the Sun.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 29/04/2019 19:39:22
What do you think?
I think you should put it somewhere else and answer the question I asked in this thread.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 29/04/2019 19:42:44
a 50 kg astronaut in the space station forms a 44.7 kg gravitational force pointed at the earth.
No.
The Kg is not a unit of force.
when a force is applied to an astronaut outside the space space and the astronaut propagates
Google translate didn't help me with that.
Would you like to try again?
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 29/04/2019 22:06:15
What do you think?
I think you should put it somewhere else and answer the question I asked in this thread.

It is not physically possible to detect a 2ug force in 1797.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 29/04/2019 22:09:59
a 50 kg astronaut in the space station forms a 44.7 kg gravitational force pointed at the earth.
No.
The Kg is not a unit of force.
when a force is applied to an astronaut outside the space space and the astronaut propagates
Google translate didn't help me with that.
Would you like to try again?

The said astronaut is weightless and propagates in any direction when a force is applied yet according to the gravity theory using the centripetal force there is an equilibrium between Newton's gravitational force and the centripetal force which does not exist.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Kryptid on 29/04/2019 23:04:08
It is not physically possible to detect a 2ug force in 1797.

https://www.logicallyfallacious.com/tools/lp/Bo/LogicalFallacies/49/Argument-by-Repetition
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alancalverd on 29/04/2019 23:11:55
Ignoring the incorrect 2μg, it is incumbent on those who find Cavendish's experiment incredible, to explain why it yielded a value of G within 1% of the current best measurements.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: evan_au on 29/04/2019 23:52:41
Quote from: alright1234
he astronaut propagates at a velocity of 50 mph
For material things (like an astronaut or space station), it would be better to use "travels" rather than "propagates".

We use "propagate" for things like waves: ocean waves or electromagnetic waves. (I know, English is pretty random...)

Quote
the astronaut propagates at a velocity of 50 mph in the direction opposite to the angular velocity, the described astronaut does not propagate towards the earth
Let's put this in perspective:
- The ISS is travelling in a circular orbit at a little over 17,000 miles per hour.
- This example imagines an astronaut getting a kick of 50 miles per hour, relative to the spacecraft
- So the 50mph can almost be ignored - the astronaut is still travelling at 17,000 mph, and so the astronaut remains in orbit
- If you look at the astronaut's orbit in more detail:
- It starts at the same altitude as the spacecraft
- But the astronaut is now travelling at slightly less than orbital speed for a circular orbit, so the astronaut starts to drop towards the Earth
- She gains speed as she drops towards the Earth
- If you had a good telescope, and the astronaut had a bright light, you would see the astronaut "below" the spacecraft (closer to the Earth) and pulling ahead of the ISS
- When the astronaut arrives at the point opposite where she got her initial kick (around 45 minutes later, for Low-Earth Orbit), she will be lower than the original orbit, but faster than the original orbit.
- The astronaut will now be travelling slightly faster than orbital speed for a circular orbit, and will start to rise further from the Earth
- Around 45 minutes later, the astronaut will be back at the original altitude.

To summarise: With a 50 mph kick, the astronaut does travel closer to the Earth - but not by very much.
But they remain in an elliptical orbit (until atmospheric drag gets them down...)

...I am sure Kryptid or Halc could give you exact figures...
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Janus on 30/04/2019 01:35:44
Also, the space stations is orbiting the earth at approximately 250 miles above the surface of the earth. The 450 ton space station cannot orbit the earth at a height of 1000 miles above the surface of the earth which proves the gravitational and centripetal forces do not function for the space station at the height of 1000 miles.

In order to orbit at a 1000 mi altitude and  and maintain a circular orbit, the ISS would just need to have an orbital velocity of ~144,38 mph rather than the 17,256 mph speed it has now.  Even if you were to move the ISS up to that height with its present orbital speed, it will still orbit the Earth, it will just be an elliptical orbit which swings out to over 5100 mi in altitude during apogee.  The mass of the ISS (being very small compared to the Earth's) has no measurable effect on this.

A balance between gravity and centrifugal force is not how orbits are explained. And trying to think of this in these terms will only lead to confusion.*  Orbits are not maintained by some delicate balance between these two.  The only time you would get such a perfect balance is with a perfectly circular orbit, which do not occur in nature. 
The play between gravity and the velocity of a satellite is just not that stringent.  Its only when you decrease the velocity to the point where the orbit get so low at it low point that it grazes the planet, or you increase it to escape velocity ( ~41% greater than the circular orbit velocity), would you have  problems with maintaining an orbit.

*Nor is it the reason for an astronaut's "Weightlessness".  He feels weightless relative to the ISS because both are free to act in response to the pull of the same gravity and are following the same free fall trajectory.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 30/04/2019 18:43:47
It is not physically possible to detect a 2ug force in 1797.
Why not?
Aristotle knew how a long time earlier
"Give me the place to stand, and I shall move the earth."
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 03/05/2019 18:11:00
It is not physically possible to detect a 2ug force in 1797.
Why not?
Aristotle knew how a long time earlier
"Give me the place to stand, and I shall move the earth."

This is similar to the LIGO that is said to detect a 10^18 m mirror displacement and Weber's gravitational bar that measured a 1662 Hz GW.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 03/05/2019 19:04:38
It is not physically possible to detect a 2ug force in 1797.
Why not?
Aristotle knew how a long time earlier
"Give me the place to stand, and I shall move the earth."

This is similar to the LIGO that is said to detect a 10^18 m mirror displacement and Weber's gravitational bar that measured a 1662 Hz GW.
It is indeed similar.
It is correct and you don't believe it.

Why don't you actually do the maths and find out what the twist of the equipment would actually be?
Are you, by any chance, not actually competent?
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: evan_au on 03/05/2019 23:48:30
Quote from: alright123
Weber's gravitational bar that measured a 1662 Hz GW.
You should say "Weber claimed to have measured Gravitational waves".

It is now thought that he was mistaken; his 1960s equipment was not sensitive enough, had too narrow a frequency range, and was too subject to noise.
He claimed a rate of black hole mergers that were incompatible with estimates of how many black holes could be colliding.
https://en.wikipedia.org/wiki/Weber_bar#History

But this comment belongs more in the LIGO thread, because with 2015 technology, LIGO is sensitive enough to detect oscillating gravitational waves over a wide range of frequencies.

And this comment has nothing to do with whether Cavendish's equipment could detect static gravitational attraction in the 1700s.
Note that Cavendish was not measuring gravitational waves: that is an entirely different phenomena.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 04/05/2019 02:44:09
 I still look forward to alright1234 explaining how the actual maths (which is older  than Cavendish) is, in some sense, wrong
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: evan_au on 04/05/2019 04:11:47
Quote from: evan_au
Cavendish's equipment could detect static gravitational attraction in the 1700s.
Note that Cavendish was not measuring gravitational waves: that is an entirely different phenomena.
I think there might be confusion here about the difference between static fields and propagating waves?

We can clarify the difference between static and propagating gravitational fields by comparing the history of static and propagating electromagnetic fields.
- Static electricity was known from ancient times in the form of lightning - a force of nature that could not be controlled.
- Similarly, the Earth's static gravitational field was known from ancient times because a dropped rock falls down - a force of nature that could not be controlled
- Static Electric fields could be produced on-demand by the ancient Greeks by rubbing amber on cat fur, for example. Thales wrote about this in 600BC.
- Static magnetic fields could be harnessed for navigation by using magnetic minerals to form a compass. Early examples date back as early as 1000 BC
- Newton's theory of universal gravitation explaining static gravitational fields (and planetary orbits) was published in 1687.
- Propagating electromagnetic fields in the form of light were known to ancient humans, but this is built into our DNA; the theoretical mechanism was not known until Maxwell's equations in 1864.
- Propagating electromagnetic waves were first generated and detected in a controlled way by Hertz in 1887. That set off a series of inventions that eventually spanned the Atlantic with radio waves, and today allows communications with space probes beyond Pluto.
- Propagating gravitational waves were first theorised based on Einsteins's general Relativity in 1916. He didn't think they would be detectable.
- Propagating gravitational waves were first detected by LIGO in 2015. This has already set of a series of inventions to improve the sensitivity and range of detectors.
- At present, we have no idea if or when or how humans will ever be able to generate a gravitational wave which is strong enough for humans to detect.

Conclusion
Static electromagnetic and gravitational fields were known from prehistoric times.
- Controllable static electromagnetic fields dates back to 600-1000BC; Cavendish's experiments with static gravitational fields in 1797 was the first time they were generated and detected in a controlled fashion by humans.
- Propagating electromagnetic fields went from theory to generation and detection in 23 years.
- Propagating gravitational waves went from theory to detection in a century, and we have no idea when we will be able to generate them.

The reason for the slower development of technologies around gravitation is that gravitational fields are about 1040 times weaker than electromagnetic fields, so we can expect the equipment to be about 1040 times bigger and more powerful (as an extremely rough order of magnitude!)

See: https://en.wikipedia.org/wiki/History_of_electromagnetic_theory#Ancient_and_classical_history
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 05/05/2019 23:21:21
It is not physically possible to detect a 2ug force in 1797.
Why not?
Aristotle knew how a long time earlier
"Give me the place to stand, and I shall move the earth."

Show a a 2ug force is measured today in modern physics. Cav is directly measuring a 2ug force. I do not think that they can do it directly even today. Show a link if I am wrong.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 06/05/2019 09:05:32
Well, it's a matter of definition.
https://www.newscientist.com/article/dn21651-worlds-most-sensitive-scales-detect-a-yoctogram/
That's a millionth of a millionth of a millionth of a microgram.
So you are wrong by a factor of about 1000000000000000000
which is pretty wrong.

If you mean a traditional "weighing machine" then, for less than the price of  a good new car, you can buy one of these.
https://www.mt.com/gb/en/home/products/Laboratory_Weighing_Solutions/Micro_Ultra_Balances/XPR_MicroBalance.html

An off-the-peg lab microbalance which will resolve down to 0.1g

They aren't new.
When I started work in the late 80s we had a balance with that resolution.
It was an AD2Z. They  still pop up on eBay from time to time.
https://www.ebay.com/itm/Perkin-Elmer-AD2Z-Autobalance-/110888520605?_ul=AR
and, if you are interested, I have a copy of the manual.


Even a home made  balance can get you down into the microgram range.
https://erowid.org/archive/rhodium/chemistry/equipment/scale2.html


So the real question here is why don't you believe reality?
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Colin2B on 06/05/2019 17:31:14
It is not physically possible to detect a 2ug force in 1797.
Ignoring the incorrect 2μg, it is incumbent on those who find Cavendish's experiment incredible, to explain why it yielded a value of G within 1% of the current best measurements.

We often find people speculating on visiting aliens with advanced technology and whether we would be capable of understanding that technology. Here we have someone from 2019 incapable of understanding technology from 1797!
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 06/05/2019 17:39:18
Here we have someone from 2019 incapable of understanding technology from 1797!
I'm not sure if it's not that they can't understand but that they actively refuse to.
The OP has refused, consistently, to even try to do the maths which shows how it would work.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Colin2B on 06/05/2019 17:50:38
I'm not sure if it's not that they can't understand but that they actively refuse to.
The OP has refused, consistently, to even try to do the maths which shows how it would work.
Maybe he cant do the maths, or maybe he's trolling
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alancalverd on 06/05/2019 22:01:03
https://en.wikipedia.org/wiki/Cavendish_experiment  (https://en.wikipedia.org/wiki/Cavendish_experiment) gives a very succinct account of the arithmetic involved in deriving G from the angular displacement of an idealised torsion suspension. Since it involves square roots and Greek characters θ and π , it is obviously magic, not science, which is probably why the OP refuses to study it.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: evan_au on 06/05/2019 22:49:34
Quote from: alright1234
Show a a 2ug force is measured today in modern physics.
Without quite going to the spectacular lengths of using resonating carbon nanotubes to count the nucleons in an atom....

A more common technology is to use resonating silicon micromechanical structures (MEMS) to detect chemicals in the environment. The chemicals adhere to the end of the beam, and it changes its resonant frequency. And time/frequency is the unit we can measure with the greatest precision.

Using this technique, one team was able to measure changes in mass of an attogram (10-18 grams).
This is a millionth of a millionth of a microgram.

Silicon MEMS (https://en.wikipedia.org/wiki/Microelectromechanical_systems) is the technology already used in your smartphone as an accelerometer.

See: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5399360/
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 07/05/2019 04:33:01
 a standard analytical balance is 100 times less sensitive; i.e. it is limited in precision to 0.1 milligrams.

That being the case how did Cav measure a 2ug force?
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 07/05/2019 05:02:20
Here we have someone from 2019 incapable of understanding technology from 1797!
I'm not sure if it's not that they can't understand but that they actively refuse to.
The OP has refused, consistently, to even try to do the maths which shows how it would work.

What math are you talking about? The question is how did Cav measure a 2 ug force in 1797? This is not a math problem------ this is a physics problem.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 07/05/2019 07:32:48
How far should the beam have moved? is a maths problem.

Answer it.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 07/05/2019 07:38:01
How far should the beam have moved? is a maths problem.

Answer it.

What\? can you explain it to me?
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alancalverd on 07/05/2019 07:51:23
RTFM.
Cavendish wrote a very comprehensive account, which has allowed many people to replicate his experiment. The Wikipedia reference I gave earlier is more thorough than most undergraduate textbooks.
I think they have the Ladybird Book of Hard Sums in  the Harvard library, but it's probably a bit advanced for your friend.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 07/05/2019 19:19:20
How far should the beam have moved? is a maths problem.

Answer it.

Cav experiment is a physics experiment not a mathematical problem. Example, weighing the mass of a penny is a physics experimental problem not a mathematical problem. How would you weigh the mass of a penny to 2 ug in 1797? You would use a scale not a pen and parchment to do some mathematics.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 07/05/2019 19:28:20
How would you weigh the mass of a penny to 2 ug in 1797?
With the help of a time machine.
Obviously that would be tricky.

It would also be irrelevant.
Nobody is saying that he measured the mass or weight of anything to that precision.
So, stop posting straw men.

However, because I can do maths (and physics) I can calculate how far the beam of Cavendish's apparatus would move when acted on by a force of 2g at the end(s) of that beam.

You are tacitly claiming that the movement is too small to measure.
In reality, he measured it.

Why don't you address the issue once and  for all by actually doing the godforsaken maths and showing that the movement is too small to measure?
Are you not clever enough, or are you scared that it will show you are wrong?
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 07/05/2019 20:31:01
The fact that Cav is measuring a force of 2 ug has precedence before anything else.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 07/05/2019 20:34:49
The fact that Cav is measuring a force of 2 ug has precedence before anything else.
Yes, he measured a very small force.
He did it by applying that small force to the end of a long lever and using it to twist a long thin wire.
and then he measured the angle through which it twisted.

You seem to think that angle would be too small to measure.
Well, as I keep saying, why don't you calculate it?
That way we would all know if it is too small to measure.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 07/05/2019 20:36:26
Not physically possible in 1797. Admit it.  It does not matter what the angle is if the original force is impossible to measure in 1797.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 07/05/2019 20:42:25
Not physically possible in 1797. Admit it.  It does not matter what the angle is if the original force is impossible to measure in 1797.
Do you understand that the angle IS the measure of the force?
Do you simply not understand how the experiment worked at all?
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 07/05/2019 20:49:44
An angle represents a magnitude in degrees but a force is depicted in Newton or grams.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 07/05/2019 20:57:15
An angle represents a magnitude in degrees but a force is depicted in Newton or grams.
Yes, but if I want to measure a force- for example the weight of something, I can do so by applying the force to a spring and measuring how much the spring stretches.
So, what I measure is a length.
But that allows me (via a calibration) to calculate a force.

In the case of this experiment, rather than stretching a spring, they twisted it.
The angle it twists through is a measure of the force (strictly speaking, the torque).
The clever bit is that by twisting a vertical wire any effect of the Earth's gravity doesn't affect the measurement because that's downward, but the twist is sideways.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 07/05/2019 21:43:35
It is not physically possible to measure a 2ug force in 1797 no matter what method you use.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Kryptid on 07/05/2019 21:57:35
Not physically possible in 1797. Admit it.  It does not matter what the angle is if the original force is impossible to measure in 1797.
It is not physically possible to measure a 2ug force in 1797 no matter what method you use.

https://www.logicallyfallacious.com/tools/lp/Bo/LogicalFallacies/49/Argument-by-Repetition
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 07/05/2019 22:11:52
but it is true! I could reword differently every time too.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Kryptid on 07/05/2019 22:13:07
but it is true! I could reword differently every time too.

You need to actually provide evidence. Repeating the claim isn't evidence.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 07/05/2019 22:26:52
but it is true! I could reword differently every time too.

You need to actually provide evidence. Repeating the claim isn't evidence.


I did. The most actuate measure device in 1797 was a balance that has an uncertainty of 1 mg.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Kryptid on 07/05/2019 22:45:56
I did. The most actuate measure device in 1797 was a balance that has an uncertainty of 1 mg.

You need to go back and re-read the thread.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alancalverd on 07/05/2019 23:29:18
The art of politics is to repeat a lie until the electorate believes it. The downfall of politicians occurs when they believe their own propaganda.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 08/05/2019 07:20:02
It is not physically possible to measure a 2ug force in 1797 no matter what method you use.
Plainly false, because someone did it.
but it is true! I could reword differently every time too.

You need to actually provide evidence. Repeating the claim isn't evidence.


I did. The most actuate measure device in 1797 was a balance that has an uncertainty of 1 mg.
Nobody is saying he had a balance that could weigh 2g
I even explained how they avoided the issue of weight.
but it is true! I could reword differently every time too.
Rewording it won't help, because you are wrong.
but it is true! I could reword differently every time too.

You need to actually provide evidence. Repeating the claim isn't evidence.


I did. The most actuate measure device in 1797 was a balance that has an uncertainty of 1 mg.
That's absurd.
It's like saying the fastest carriage back then could only travel at 40 MPH so a bow couldn't fire and arrow  any faster than that.


It's a different process.
It has different limits.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Colin2B on 08/05/2019 08:58:13
It is not physically possible to measure a 2ug force in 1797 no matter what method you use.
The experiment and how the measurements were performed has been explained to you. Your argument that an angle cannot represent a force is fallacious as the mechanism is used in many early scales, angle also measures current in a galvanometer, and in a clock measures time.
It also appears you do not understand integration.
You have also posted unsubstantiated conspiracy theories that deny scientific observation.
We welcome debate on science subjects, but if you are unwilling to learn, or are unable to understand the replies to your posts we will ask you to limit your posting to The Lighter Side.
To give you time to consider your stance we will activate a temporary ban to start when you return from your honeymoon.
Congratulations on your marriage and we wish you every happiness.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 08/05/2019 19:55:29
I did. The most actuate measure device in 1797 was a balance that has an uncertainty of 1 mg.


You cannot possible twist a iron rod using a weight equal to a single particle of dust.

To get good a play a piano require repetitive practice.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 08/05/2019 20:15:34
Also, regarding the Sun gravitation force on the centripetal force would be negligible since using a micro balance the variable of a weight is not observed every 12 hours.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 08/05/2019 20:23:02
I did. The most actuate measure device in 1797 was a balance that has an uncertainty of 1 mg.


You cannot possible twist a iron rod using a weight equal to a single particle of dust.

To get good a play a piano require repetitive practice.

To get good at playing the piano you need to repeat doing the right thing.
Repeating mistakes doesn't help
"You cannot possible twist a iron rod using a weight equal to a single particle of dust. "
Nobody said you could, so that's something you shouldn't repeat.
And, of course, (per Aristotle) you could- if you used a long enough lever.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Kryptid on 08/05/2019 21:42:24
Also, regarding the Sun gravitation force on the centripetal force would be negligible since using a micro balance the variable of a weight is not observed every 12 hours.

Do you have a reputable source saying that such a variation does not occur?
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 08/05/2019 21:49:50
Also, regarding the Sun gravitation force on the centripetal force would be negligible since using a micro balance the variable of a weight is not observed every 12 hours.

Do you have a reputable source saying that such a variation does not occur?

Hey micro balances.

https://www.hogentogler.com/mettler-toledo/xpe56-microbalance.asp?gclid=CjwKCAjw_MnmBRAoEiwAPRRWW07vSKVNnqv-xVqMBj9H9gki6lYMLCzMct1XwUI-aIa9LBeGtXNEFRoCBXcQAvD_BwE
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Kryptid on 08/05/2019 21:57:05
Hey micro balances.

https://www.hogentogler.com/mettler-toledo/xpe56-microbalance.asp?gclid=CjwKCAjw_MnmBRAoEiwAPRRWW07vSKVNnqv-xVqMBj9H9gki6lYMLCzMct1XwUI-aIa9LBeGtXNEFRoCBXcQAvD_BwE

Please quote the part of that which says that the weight of objects placed on that balance do not vary throughout the day.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 08/05/2019 21:58:27
Hey micro balances.
Microbalances obtain really great stability by a simple trick.
They have a built in calibration weight and a system for using it, automatically, to recalibrate the balance  regularly.
So, if there was a variation over 12 hrs, they wouldn't see it. Again, it would be better if you knew what you were talking about.

None of that matters.
Cavendish did not build a balance.
Do you understand that?

He wasn't wearing anything in his lab.
He didn't build a balance.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 23/05/2019 00:27:18
How can you sit there an tell ME that it is possible to measure a 2 ug force in 1797? Newton's gravity equation is based on this erroneous and incredulous measurement. Shame.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Colin2B on 23/05/2019 08:45:04
How can you sit there an tell ME that it is possible to measure a 2 ug force in 1797? ........ Shame.
How can you sit there and tell us that you do not understand a piece of technology from 1797. Shame on you that you keep repeating false information.

We welcome intelligent debate, but mindlessly repeating false information is trolling.

It has been explained, repeatedly, how this experiment works, understanding it is not beyond the wit of secondary school pupils.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Kryptid on 23/05/2019 16:49:30
Newton's gravity equation is based on this erroneous and incredulous measurement.

His equation works.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 23/05/2019 19:25:46
How can you sit there an tell ME that it is possible to measure a 2 ug force in 1797?
In the same way that I can tell you it was possible for someone to climb Everest in 1953.
Someone did it.

How are you not understanding this?

Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alright1234 on 23/05/2019 23:32:51
Newton's gravity equation is based on this erroneous and incredulous measurement.

His equation works.

Does Newton's equations work to explain the halve circular path of the CSML to the moon?
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Kryptid on 24/05/2019 00:16:19
Does Newton's equations work to explain the halve circular path of the CSML to the moon?

Yes, because gravity pulls on objects that are in free fall. Objects in free fall are weightless. If you don't believe me, try weighing something on a scale while both the scale and object in question are falling in a vacuum. It won't work.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alancalverd on 24/05/2019 19:10:05
Newton's gravity equation is based on this erroneous and incredulous measurement. Shame.
Newton died 50 years before Cavendish's experiment. Always check the obvious before opening your mouth, lest people take you for a fool.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Colin2B on 26/05/2019 00:32:20
Always check the obvious before opening your mouth, lest people take you for a fool.
Too late for that  ;D
Poor soul, brain overheating, needs a sabbatical, lets give him one on us.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: jeffreyH on 26/05/2019 11:28:40
Newton's gravity equation is based on this erroneous and incredulous measurement. Shame.
Newton died 50 years before Cavendish's experiment. Always check the obvious before opening your mouth, lest people take you for a fool.

LOL. That.creased me up!
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: happy6666 on 31/07/2019 21:50:20
I think alright is right where Newton created Newton's equation and Cav supported Newton's equation with his experiment. However, if alright1234 is right than would he not be the greatest physics that ever lived even greater than Newton which I doubt but I could be wrong since didn't Einstein think that the planets revolved around the earth in 1905.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Kryptid on 31/07/2019 21:52:13
didn't Einstein think that the planets revolved around the earth in 1905.

No.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: happy6666 on 01/08/2019 00:02:37
How did Newton derive the constant G?
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: happy6666 on 01/08/2019 00:21:44
didn't Einstein think that the planets revolved around the earth in 1905.

No.

Is Einstein translational velocity constant or does it vary? If the translational velocity is constant then it can only occur with the earth at the center of the Universe. Golly I thought everyone new that. I learn that in high school. Gee I feel smart!!! I am cute too. He he he
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Kryptid on 01/08/2019 06:19:50
Is Einstein translational velocity constant or does it vary? If the translational velocity is constant then it can only occur with the earth at the center of the Universe. Golly I thought everyone new that. I learn that in high school. Gee I feel smart!!! I am cute too. He he he

Nothing about relativity requires Earth to be at the center of the Universe. It's the opposite, in fact: relativity says that there are no absolute reference frames and thus no absolute coordinates in space.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: Bored chemist on 01/08/2019 09:04:21
How did Newton derive the constant G?
I'm not sure he did.
You can do most of the orbital mechanics calculations by knowing that it is constant.
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: alancalverd on 01/08/2019 10:08:35
How did Newton derive the constant G?

Newton's equation F = GmM/r^2 solves Kepler's observed orbital motion of the planets, so in principle anyone who could measure or estimate F, M, m and r could derive a value for G.  The practical problem in the 1700s arose from not knowing the density of any other heavenly body, or having sufficiently sensitive apparatus to measure F for laboratory-sized bodies.

As it turned out, Maskeleyne's use of a  mountain and Cavendish's use of a torsion balance solved the problem by brilliant astronomical technique and engineering respectively, and came up with reasonably similar values.   
Title: Re: Is Cavendish's displacement of 2ug measurable?
Post by: evan_au on 01/08/2019 14:44:17
Quote from: happy6666 on Today at 00:02:37
How did Newton derive the constant G?
You can solve Newton's law of gravity if you measure the radius of the planetary orbits, know the mass of the Sun & Earth, can measure the force between the Sun and Planets and/or know "G".

In practise, Newton didn't know any of these parameters.

There was a transit of Venus across the face of the Sun in 1769 which was observed by astronomers in various places around the world; when the measurements were collated, this determined the size of the solar system and resolved one of the unknowns in Newton's law of gravitation.
- It also allowed determination of the speed of light, since it was observed that the transits of the moons of Jupiter occurred later when Jupiter was on the other side of the Sun from Earth, due to the finite speed of light...

Cavendish used known masses at known distances; he measured the force of attraction and then could solve for the remaining unknown: G.
- This knowledge could then be used to "weigh" the Sun and the Earth (and other bodies with moons).

See: https://en.wikipedia.org/wiki/1769_transit_of_Venus_observed_from_Tahiti