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What is the most precise physical measurement ever performed?
How are the 4 km arms of LIGO measured so accurately?What near-future measurement technique improvements will extend our physical knowledge?Oil drop experiment--How was the result so accurate?What limitations are there in measuring physical properties accurately?What is the difference between a measurement and an experiment?What physical properties can we measure most accurately?What do clocks measure?How can a Lego version of a Kibble balance measure the Planck constant?Experimental measurement of the radial excess
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Obviously some things, such as the speed of light in a vacuum, are defined to be a precise value. The kilogram was recently defined to have a specific value by fixing Plank's constant to $6.62607015cdot 10^−34fracm^2 kgs$.
In particular, in the case of the latter, we held off on defining this value until the two competing approaches for measuring the kilogram agreed with each other within the error bounds of their respective measurements.
Which leads me to wonder, what is the most precisely measured (not defined) value that the scientific community has measured. I am thinking in terms of relative error (uncertainty / value). Before we defined it, Plank's constant was measured to a relative error of $10^-9$. Have we measured anything with a lower relative error?
experimental-physics measurements
edited Aug 21 at 22:08
knzhou
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asked Aug 16 at 3:53
Cort AmmonCort Ammon
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add a comment |
$begingroup$
Obviously some things, such as the speed of light in a vacuum, are defined to be a precise value. The kilogram was recently defined to have a specific value by fixing Plank's constant to $6.62607015cdot 10^−34fracm^2 kgs$.
In particular, in the case of the latter, we held off on defining this value until the two competing approaches for measuring the kilogram agreed with each other within the error bounds of their respective measurements.
Which leads me to wonder, what is the most precisely measured (not defined) value that the scientific community has measured. I am thinking in terms of relative error (uncertainty / value). Before we defined it, Plank's constant was measured to a relative error of $10^-9$. Have we measured anything with a lower relative error?
experimental-physics measurements
edited Aug 21 at 22:08
knzhou
55.1k14 gold badges156 silver badges265 bronze badges
asked Aug 16 at 3:53
Cort AmmonCort Ammon
27.4k4 gold badges59 silver badges95 bronze badges
$endgroup$
11
$begingroup$
@Qmechanic Mind explaining why you felt this needed to be put on hold via a mod hammer, when there were clearly good answers coming forth, and everyone seems to agree upon what is meant? In fact, with 6 upvotes and 33 views, it seems people seem to feel this is a good question.
$endgroup$
– Cort Ammon
Aug 16 at 5:54
1
$begingroup$
Shouldn't the title refer to precision rather than accuracy?
$endgroup$
– Gremlin
Aug 16 at 13:02
5
$begingroup$
Discussion about this question on meta.
$endgroup$
– Emilio Pisanty
Aug 16 at 13:41
1
$begingroup$
@Gremlin Updated. You're right, I was lazy in my wording. "precision" is a better word choice
$endgroup$
– Cort Ammon
Aug 16 at 15:35
add a comment |
$begingroup$
Obviously some things, such as the speed of light in a vacuum, are defined to be a precise value. The kilogram was recently defined to have a specific value by fixing Plank's constant to $6.62607015cdot 10^−34fracm^2 kgs$.
In particular, in the case of the latter, we held off on defining this value until the two competing approaches for measuring the kilogram agreed with each other within the error bounds of their respective measurements.
Which leads me to wonder, what is the most precisely measured (not defined) value that the scientific community has measured. I am thinking in terms of relative error (uncertainty / value). Before we defined it, Plank's constant was measured to a relative error of $10^-9$. Have we measured anything with a lower relative error?
experimental-physics measurements
edited Aug 21 at 22:08
knzhou
55.1k14 gold badges156 silver badges265 bronze badges
asked Aug 16 at 3:53
Cort AmmonCort Ammon
27.4k4 gold badges59 silver badges95 bronze badges
$endgroup$
Obviously some things, such as the speed of light in a vacuum, are defined to be a precise value. The kilogram was recently defined to have a specific value by fixing Plank's constant to $6.62607015cdot 10^−34fracm^2 kgs$.
In particular, in the case of the latter, we held off on defining this value until the two competing approaches for measuring the kilogram agreed with each other within the error bounds of their respective measurements.
Which leads me to wonder, what is the most precisely measured (not defined) value that the scientific community has measured. I am thinking in terms of relative error (uncertainty / value). Before we defined it, Plank's constant was measured to a relative error of $10^-9$. Have we measured anything with a lower relative error?
experimental-physics measurements
experimental-physics measurements
edited Aug 21 at 22:08
knzhou
55.1k14 gold badges156 silver badges265 bronze badges
asked Aug 16 at 3:53
Cort AmmonCort Ammon
27.4k4 gold badges59 silver badges95 bronze badges
edited Aug 21 at 22:08
knzhou
55.1k14 gold badges156 silver badges265 bronze badges
asked Aug 16 at 3:53
Cort AmmonCort Ammon
27.4k4 gold badges59 silver badges95 bronze badges
edited Aug 21 at 22:08
knzhou
55.1k14 gold badges156 silver badges265 bronze badges
edited Aug 21 at 22:08
knzhou
55.1k14 gold badges156 silver badges265 bronze badges
edited Aug 21 at 22:08
knzhou
55.1k14 gold badges156 silver badges265 bronze badges
55.1k14 gold badges156 silver badges265 bronze badges
asked Aug 16 at 3:53
Cort AmmonCort Ammon
27.4k4 gold badges59 silver badges95 bronze badges
asked Aug 16 at 3:53
Cort AmmonCort Ammon
27.4k4 gold badges59 silver badges95 bronze badges
asked Aug 16 at 3:53
Cort AmmonCort Ammon
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27.4k4 gold badges59 silver badges95 bronze badges
11
$begingroup$
@Qmechanic Mind explaining why you felt this needed to be put on hold via a mod hammer, when there were clearly good answers coming forth, and everyone seems to agree upon what is meant? In fact, with 6 upvotes and 33 views, it seems people seem to feel this is a good question.
$endgroup$
– Cort Ammon
Aug 16 at 5:54
1
$begingroup$
Shouldn't the title refer to precision rather than accuracy?
$endgroup$
– Gremlin
Aug 16 at 13:02
5
$begingroup$
Discussion about this question on meta.
$endgroup$
– Emilio Pisanty
Aug 16 at 13:41
1
$begingroup$
@Gremlin Updated. You're right, I was lazy in my wording. "precision" is a better word choice
$endgroup$
– Cort Ammon
Aug 16 at 15:35
add a comment |
11
$begingroup$
@Qmechanic Mind explaining why you felt this needed to be put on hold via a mod hammer, when there were clearly good answers coming forth, and everyone seems to agree upon what is meant? In fact, with 6 upvotes and 33 views, it seems people seem to feel this is a good question.
$endgroup$
– Cort Ammon
Aug 16 at 5:54
1
$begingroup$
Shouldn't the title refer to precision rather than accuracy?
$endgroup$
– Gremlin
Aug 16 at 13:02
5
$begingroup$
Discussion about this question on meta.
$endgroup$
– Emilio Pisanty
Aug 16 at 13:41
1
$begingroup$
@Gremlin Updated. You're right, I was lazy in my wording. "precision" is a better word choice
$endgroup$
– Cort Ammon
Aug 16 at 15:35
11
11
$begingroup$
@Qmechanic Mind explaining why you felt this needed to be put on hold via a mod hammer, when there were clearly good answers coming forth, and everyone seems to agree upon what is meant? In fact, with 6 upvotes and 33 views, it seems people seem to feel this is a good question.
$endgroup$
– Cort Ammon
Aug 16 at 5:54
$begingroup$
@Qmechanic Mind explaining why you felt this needed to be put on hold via a mod hammer, when there were clearly good answers coming forth, and everyone seems to agree upon what is meant? In fact, with 6 upvotes and 33 views, it seems people seem to feel this is a good question.
$endgroup$
– Cort Ammon
Aug 16 at 5:54
1
1
$begingroup$
Shouldn't the title refer to precision rather than accuracy?
$endgroup$
– Gremlin
Aug 16 at 13:02
$begingroup$
Shouldn't the title refer to precision rather than accuracy?
$endgroup$
– Gremlin
Aug 16 at 13:02
5
5
$begingroup$
Discussion about this question on meta.
$endgroup$
– Emilio Pisanty
Aug 16 at 13:41
$begingroup$
Discussion about this question on meta.
$endgroup$
– Emilio Pisanty
Aug 16 at 13:41
1
1
$begingroup$
@Gremlin Updated. You're right, I was lazy in my wording. "precision" is a better word choice
$endgroup$
– Cort Ammon
Aug 16 at 15:35
$begingroup$
@Gremlin Updated. You're right, I was lazy in my wording. "precision" is a better word choice
$endgroup$
– Cort Ammon
Aug 16 at 15:35
add a comment |
6 Answers
6
active
oldest
votes
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The magnetic moment of the electron has been measured to a few parts in $10^13$. (Source) This provides an exquisite test of quantum electrodynamics, and calculating the relevant Feynman diagrams has been a Herculean effort over decades.
Note that the more precise tests cited in other answers are basically null results: no difference between gravitational and inertial mass; no difference in magnitude of charge between proton and electron; no mass of photon. So I believe the magnetic moment of the electron is the most precise measurement that is non-null and thus “interesting”.
edited Aug 16 at 7:13
PM 2Ring
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answered Aug 16 at 5:01
G. SmithG. Smith
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1
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Yeah that’s the answer I was looking for but somehow only found $alpha$.
$endgroup$
– ZeroTheHero
Aug 16 at 5:35
1
$begingroup$
While I'm not going to change the question to invalidate answers, your note is a good one that I'd edit in if I had a chance. While those null results are indeed interesting, I have the intuitive sense that it's easier to measure them with arbitrarily high precision. It is interesting, however, how few orders of magnitude separate this result from some of the equivalency tests listed in other answers.
$endgroup$
– Cort Ammon
Aug 16 at 16:18
4
$begingroup$
For full clarity, this isn't the most accurate or precise measurement known, and the fact that @CortAmmon has accepted this answer (when there are tighter uncertainties reported in other answers) is a good example of why this thread is problematic. If it comes to "non-null" results, though, this paper presents a measurement with considerably more precision than the one in this answer (but I'm not going to take the (pretty arrogant) tack that others here have taken in asserting that the first thing I found is "the" most precise experiment).
$endgroup$
– Emilio Pisanty
Aug 21 at 10:18
add a comment |
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Carrying the fame of being one of the most precisely verified propositions in physics, the ratio of the gravitational to inertial mass was verified to be unity within $1$ in $10^15$ by the MICROSCOPE satellite in $2017$. The earlier best precision was $5times10^-14$, obtained by Baessler, et al. in $1999$.
References:
https://en.wikipedia.org/wiki/MICROSCOPE_(satellite)- https://en.wikipedia.org/wiki/Equivalence_principle#Tests_of_the_weak_equivalence_principle
answered Aug 16 at 4:13
Dvij MankadDvij Mankad
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A few more candidates:
- The quantized Hall resistance is a great and surprising example, since it's an emergent property of rather complicated, "dirty" systems. As stated here (2013) one can measure the resistance to one part in $3 times 10^10$. For this reason this effect is now used to define the Ohm.
- Equivalence principle tests using torsion balances reached precisions of about one part in $10^11$ in $1964$, see here. Another existing answer gives a more precise result from a more modern experiment. These can be thought of as either verifying the equality of gravitational and inertial mass, or placing bounds on the strength of long-range fifth forces.
- The electrical neutrality of bulk matter follows because the electron and proton have exactly opposite charges. Treating the charge of the electron as given, tests of neutrality effectively measure the charge of the proton, with one experiment achieving a sensitivity of one part in $10^21$ in $1973$. Arguments from cosmology can be used to set much larger bounds, though they require more assumptions.
answered Aug 16 at 4:31
knzhouknzhou
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Can you suggest me some reference where I can look up how the Equivalence Principle tests can be interpreted as putting bounds on a long-range fifth force?
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– Dvij Mankad
Aug 16 at 4:59
1
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Another example: Earth-Moon distance measured with a laser. Distance about 3e10 cm, measured with a few cm accuracy I think. Should investigate more to be sure.
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– thermomagnetic condensed boson
Aug 16 at 8:47
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Electrical neutrality of bulk matter: That only proves the equality of the charges if the number of electrons and protons in bulk matter is the same - but if the charge on the electron was 1.1 times that on the proton, I would expect bulk matter to have about 10% more electrons and still be neutral.
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– Martin Bonner
Aug 16 at 13:03
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Update: the ohm is now defined in terms of the elementary charge
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– gen-z ready to perish
Aug 21 at 6:11
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@gen-z Not particularly - in actual metrological practice, it's rather more accurate to say that the coulomb is defined in terms of the ohm.
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– Emilio Pisanty
Aug 21 at 10:20
add a comment |
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A good candidate is the measurement of the fine structure constant $alpha$. This wiki article on precision tests of QED states that:
The agreement found this way is to within ten parts in a billion ($10^−8$), based on the comparison of the electron anomalous magnetic dipole moment and the Rydberg constant from atom recoil measurements...
There is also an upper bound on the mass of the photon, which is in the range of $10^-27eV/c^2$ although that's an upper bound rather than a measurement since the expected value is $0$.
answered Aug 16 at 4:01
ZeroTheHeroZeroTheHero
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1
$begingroup$
The ratio of the gravitational to inertial mass was verified to be unity within $1$ in $10^15$ in $2017$ by the MICROSCOPE satellite: en.wikipedia.org/wiki/MICROSCOPE_(satellite)
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– Dvij Mankad
Aug 16 at 4:04
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@DvijMankad this ought to be an answer then...
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– ZeroTheHero
Aug 16 at 4:07
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I think it could be added as a possible answer but I am not sure if there exist more precise measurements in particle physics, maybe some electroweak precision measurements?
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– Dvij Mankad
Aug 16 at 4:08
1
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@DvijMankad I do believe the only way a question like this can be answered on StackExchange is to put forth the best answer an individual may know, and the best answer will get upvoted. (And I highly doubt a good answer will be downvoted just because somebody finds a better answer)
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– Cort Ammon
Aug 16 at 4:10
1
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@CortAmmon Makes sense. Done! :-)
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– Dvij Mankad
Aug 16 at 4:13
|
show 1 more comment
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To answer the question from a different angle, LIGO has measured gravitational waves several times over the last few years. To do so they have to observe a distortion in a 4km arm, in the order of $10^-18$m. In other words, it has to detect a fractional imprecision in its length of ~$2.5 * 10^-23$. That's pretty accurate.
answered Aug 16 at 12:49
WittierDinosaurWittierDinosaur
191 bronze badge
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LIGO is extremely sensitive, but pretty inaccurate, its calibration has an uncertainty of a few percent.
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– Bas Swinckels
Aug 16 at 13:05
1
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Thank you for the answer! What Bas Swinckles mentions is something I was trying to avoid when crafting the criteria of the question. The 4km long arm is not what LIGO actually measures, but rather the 10^-18m number is what is being measured. LIGO was one heck of a feat, but I was trying to avoid high-sensitivity/low-accuracy measurements because we can always come up with a "higher" value by comparing it against something bigger.
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– Cort Ammon
Aug 16 at 15:22
add a comment |
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Another quantity that is well known is the frequency of the 21 cm line of Hydrogen hyperfine splitting that has been measured to about 13 significant figures, 1420405751.7667±0.0009 Hz. Unlike the electron magnetic moment, mentioned in another answer, the QED calculation for hyperfine splitting is not as accurate. This calculation also depends on other fundamental constants, including electron/proton mass ratio and proton magnetic moment. which are not known to equivalent precision.
answered Aug 16 at 15:45
amateurAstroamateurAstro
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6 Answers
6
active
oldest
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6 Answers
6
active
oldest
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active
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active
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$begingroup$
The magnetic moment of the electron has been measured to a few parts in $10^13$. (Source) This provides an exquisite test of quantum electrodynamics, and calculating the relevant Feynman diagrams has been a Herculean effort over decades.
Note that the more precise tests cited in other answers are basically null results: no difference between gravitational and inertial mass; no difference in magnitude of charge between proton and electron; no mass of photon. So I believe the magnetic moment of the electron is the most precise measurement that is non-null and thus “interesting”.
edited Aug 16 at 7:13
PM 2Ring
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answered Aug 16 at 5:01
G. SmithG. Smith
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$endgroup$
1
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Yeah that’s the answer I was looking for but somehow only found $alpha$.
$endgroup$
– ZeroTheHero
Aug 16 at 5:35
1
$begingroup$
While I'm not going to change the question to invalidate answers, your note is a good one that I'd edit in if I had a chance. While those null results are indeed interesting, I have the intuitive sense that it's easier to measure them with arbitrarily high precision. It is interesting, however, how few orders of magnitude separate this result from some of the equivalency tests listed in other answers.
$endgroup$
– Cort Ammon
Aug 16 at 16:18
4
$begingroup$
For full clarity, this isn't the most accurate or precise measurement known, and the fact that @CortAmmon has accepted this answer (when there are tighter uncertainties reported in other answers) is a good example of why this thread is problematic. If it comes to "non-null" results, though, this paper presents a measurement with considerably more precision than the one in this answer (but I'm not going to take the (pretty arrogant) tack that others here have taken in asserting that the first thing I found is "the" most precise experiment).
$endgroup$
– Emilio Pisanty
Aug 21 at 10:18
add a comment |
$begingroup$
The magnetic moment of the electron has been measured to a few parts in $10^13$. (Source) This provides an exquisite test of quantum electrodynamics, and calculating the relevant Feynman diagrams has been a Herculean effort over decades.
Note that the more precise tests cited in other answers are basically null results: no difference between gravitational and inertial mass; no difference in magnitude of charge between proton and electron; no mass of photon. So I believe the magnetic moment of the electron is the most precise measurement that is non-null and thus “interesting”.
edited Aug 16 at 7:13
PM 2Ring
4,1332 gold badges13 silver badges29 bronze badges
answered Aug 16 at 5:01
G. SmithG. Smith
21k1 gold badge37 silver badges68 bronze badges
$endgroup$
1
$begingroup$
Yeah that’s the answer I was looking for but somehow only found $alpha$.
$endgroup$
– ZeroTheHero
Aug 16 at 5:35
1
$begingroup$
While I'm not going to change the question to invalidate answers, your note is a good one that I'd edit in if I had a chance. While those null results are indeed interesting, I have the intuitive sense that it's easier to measure them with arbitrarily high precision. It is interesting, however, how few orders of magnitude separate this result from some of the equivalency tests listed in other answers.
$endgroup$
– Cort Ammon
Aug 16 at 16:18
4
$begingroup$
For full clarity, this isn't the most accurate or precise measurement known, and the fact that @CortAmmon has accepted this answer (when there are tighter uncertainties reported in other answers) is a good example of why this thread is problematic. If it comes to "non-null" results, though, this paper presents a measurement with considerably more precision than the one in this answer (but I'm not going to take the (pretty arrogant) tack that others here have taken in asserting that the first thing I found is "the" most precise experiment).
$endgroup$
– Emilio Pisanty
Aug 21 at 10:18
add a comment |
$begingroup$
The magnetic moment of the electron has been measured to a few parts in $10^13$. (Source) This provides an exquisite test of quantum electrodynamics, and calculating the relevant Feynman diagrams has been a Herculean effort over decades.
Note that the more precise tests cited in other answers are basically null results: no difference between gravitational and inertial mass; no difference in magnitude of charge between proton and electron; no mass of photon. So I believe the magnetic moment of the electron is the most precise measurement that is non-null and thus “interesting”.
edited Aug 16 at 7:13
PM 2Ring
4,1332 gold badges13 silver badges29 bronze badges
answered Aug 16 at 5:01
G. SmithG. Smith
21k1 gold badge37 silver badges68 bronze badges
$endgroup$
The magnetic moment of the electron has been measured to a few parts in $10^13$. (Source) This provides an exquisite test of quantum electrodynamics, and calculating the relevant Feynman diagrams has been a Herculean effort over decades.
Note that the more precise tests cited in other answers are basically null results: no difference between gravitational and inertial mass; no difference in magnitude of charge between proton and electron; no mass of photon. So I believe the magnetic moment of the electron is the most precise measurement that is non-null and thus “interesting”.
edited Aug 16 at 7:13
PM 2Ring
4,1332 gold badges13 silver badges29 bronze badges
answered Aug 16 at 5:01
G. SmithG. Smith
21k1 gold badge37 silver badges68 bronze badges
edited Aug 16 at 7:13
PM 2Ring
4,1332 gold badges13 silver badges29 bronze badges
edited Aug 16 at 7:13
PM 2Ring
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edited Aug 16 at 7:13
PM 2Ring
4,1332 gold badges13 silver badges29 bronze badges
4,1332 gold badges13 silver badges29 bronze badges
answered Aug 16 at 5:01
G. SmithG. Smith
21k1 gold badge37 silver badges68 bronze badges
answered Aug 16 at 5:01
G. SmithG. Smith
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answered Aug 16 at 5:01
G. SmithG. Smith
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21k1 gold badge37 silver badges68 bronze badges
1
$begingroup$
Yeah that’s the answer I was looking for but somehow only found $alpha$.
$endgroup$
– ZeroTheHero
Aug 16 at 5:35
1
$begingroup$
While I'm not going to change the question to invalidate answers, your note is a good one that I'd edit in if I had a chance. While those null results are indeed interesting, I have the intuitive sense that it's easier to measure them with arbitrarily high precision. It is interesting, however, how few orders of magnitude separate this result from some of the equivalency tests listed in other answers.
$endgroup$
– Cort Ammon
Aug 16 at 16:18
4
$begingroup$
For full clarity, this isn't the most accurate or precise measurement known, and the fact that @CortAmmon has accepted this answer (when there are tighter uncertainties reported in other answers) is a good example of why this thread is problematic. If it comes to "non-null" results, though, this paper presents a measurement with considerably more precision than the one in this answer (but I'm not going to take the (pretty arrogant) tack that others here have taken in asserting that the first thing I found is "the" most precise experiment).
$endgroup$
– Emilio Pisanty
Aug 21 at 10:18
add a comment |
1
$begingroup$
Yeah that’s the answer I was looking for but somehow only found $alpha$.
$endgroup$
– ZeroTheHero
Aug 16 at 5:35
1
$begingroup$
While I'm not going to change the question to invalidate answers, your note is a good one that I'd edit in if I had a chance. While those null results are indeed interesting, I have the intuitive sense that it's easier to measure them with arbitrarily high precision. It is interesting, however, how few orders of magnitude separate this result from some of the equivalency tests listed in other answers.
$endgroup$
– Cort Ammon
Aug 16 at 16:18
4
$begingroup$
For full clarity, this isn't the most accurate or precise measurement known, and the fact that @CortAmmon has accepted this answer (when there are tighter uncertainties reported in other answers) is a good example of why this thread is problematic. If it comes to "non-null" results, though, this paper presents a measurement with considerably more precision than the one in this answer (but I'm not going to take the (pretty arrogant) tack that others here have taken in asserting that the first thing I found is "the" most precise experiment).
$endgroup$
– Emilio Pisanty
Aug 21 at 10:18
1
1
$begingroup$
Yeah that’s the answer I was looking for but somehow only found $alpha$.
$endgroup$
– ZeroTheHero
Aug 16 at 5:35
$begingroup$
Yeah that’s the answer I was looking for but somehow only found $alpha$.
$endgroup$
– ZeroTheHero
Aug 16 at 5:35
1
1
$begingroup$
While I'm not going to change the question to invalidate answers, your note is a good one that I'd edit in if I had a chance. While those null results are indeed interesting, I have the intuitive sense that it's easier to measure them with arbitrarily high precision. It is interesting, however, how few orders of magnitude separate this result from some of the equivalency tests listed in other answers.
$endgroup$
– Cort Ammon
Aug 16 at 16:18
$begingroup$
While I'm not going to change the question to invalidate answers, your note is a good one that I'd edit in if I had a chance. While those null results are indeed interesting, I have the intuitive sense that it's easier to measure them with arbitrarily high precision. It is interesting, however, how few orders of magnitude separate this result from some of the equivalency tests listed in other answers.
$endgroup$
– Cort Ammon
Aug 16 at 16:18
4
4
$begingroup$
For full clarity, this isn't the most accurate or precise measurement known, and the fact that @CortAmmon has accepted this answer (when there are tighter uncertainties reported in other answers) is a good example of why this thread is problematic. If it comes to "non-null" results, though, this paper presents a measurement with considerably more precision than the one in this answer (but I'm not going to take the (pretty arrogant) tack that others here have taken in asserting that the first thing I found is "the" most precise experiment).
$endgroup$
– Emilio Pisanty
Aug 21 at 10:18
$begingroup$
For full clarity, this isn't the most accurate or precise measurement known, and the fact that @CortAmmon has accepted this answer (when there are tighter uncertainties reported in other answers) is a good example of why this thread is problematic. If it comes to "non-null" results, though, this paper presents a measurement with considerably more precision than the one in this answer (but I'm not going to take the (pretty arrogant) tack that others here have taken in asserting that the first thing I found is "the" most precise experiment).
$endgroup$
– Emilio Pisanty
Aug 21 at 10:18
add a comment |
$begingroup$
Carrying the fame of being one of the most precisely verified propositions in physics, the ratio of the gravitational to inertial mass was verified to be unity within $1$ in $10^15$ by the MICROSCOPE satellite in $2017$. The earlier best precision was $5times10^-14$, obtained by Baessler, et al. in $1999$.
References:
https://en.wikipedia.org/wiki/MICROSCOPE_(satellite)- https://en.wikipedia.org/wiki/Equivalence_principle#Tests_of_the_weak_equivalence_principle
answered Aug 16 at 4:13
Dvij MankadDvij Mankad
6,8154 gold badges29 silver badges80 bronze badges
$endgroup$
add a comment |
$begingroup$
Carrying the fame of being one of the most precisely verified propositions in physics, the ratio of the gravitational to inertial mass was verified to be unity within $1$ in $10^15$ by the MICROSCOPE satellite in $2017$. The earlier best precision was $5times10^-14$, obtained by Baessler, et al. in $1999$.
References:
https://en.wikipedia.org/wiki/MICROSCOPE_(satellite)- https://en.wikipedia.org/wiki/Equivalence_principle#Tests_of_the_weak_equivalence_principle
answered Aug 16 at 4:13
Dvij MankadDvij Mankad
6,8154 gold badges29 silver badges80 bronze badges
$endgroup$
add a comment |
$begingroup$
Carrying the fame of being one of the most precisely verified propositions in physics, the ratio of the gravitational to inertial mass was verified to be unity within $1$ in $10^15$ by the MICROSCOPE satellite in $2017$. The earlier best precision was $5times10^-14$, obtained by Baessler, et al. in $1999$.
References:
https://en.wikipedia.org/wiki/MICROSCOPE_(satellite)- https://en.wikipedia.org/wiki/Equivalence_principle#Tests_of_the_weak_equivalence_principle
answered Aug 16 at 4:13
Dvij MankadDvij Mankad
6,8154 gold badges29 silver badges80 bronze badges
$endgroup$
Carrying the fame of being one of the most precisely verified propositions in physics, the ratio of the gravitational to inertial mass was verified to be unity within $1$ in $10^15$ by the MICROSCOPE satellite in $2017$. The earlier best precision was $5times10^-14$, obtained by Baessler, et al. in $1999$.
References:
https://en.wikipedia.org/wiki/MICROSCOPE_(satellite)- https://en.wikipedia.org/wiki/Equivalence_principle#Tests_of_the_weak_equivalence_principle
answered Aug 16 at 4:13
Dvij MankadDvij Mankad
6,8154 gold badges29 silver badges80 bronze badges
edited Aug 16 at 4:21
answered Aug 16 at 4:13
Dvij MankadDvij Mankad
6,8154 gold badges29 silver badges80 bronze badges
answered Aug 16 at 4:13
Dvij MankadDvij Mankad
6,8154 gold badges29 silver badges80 bronze badges
answered Aug 16 at 4:13
Dvij MankadDvij Mankad
6,8154 gold badges29 silver badges80 bronze badges
6,8154 gold badges29 silver badges80 bronze badges
add a comment |
add a comment |
$begingroup$
A few more candidates:
- The quantized Hall resistance is a great and surprising example, since it's an emergent property of rather complicated, "dirty" systems. As stated here (2013) one can measure the resistance to one part in $3 times 10^10$. For this reason this effect is now used to define the Ohm.
- Equivalence principle tests using torsion balances reached precisions of about one part in $10^11$ in $1964$, see here. Another existing answer gives a more precise result from a more modern experiment. These can be thought of as either verifying the equality of gravitational and inertial mass, or placing bounds on the strength of long-range fifth forces.
- The electrical neutrality of bulk matter follows because the electron and proton have exactly opposite charges. Treating the charge of the electron as given, tests of neutrality effectively measure the charge of the proton, with one experiment achieving a sensitivity of one part in $10^21$ in $1973$. Arguments from cosmology can be used to set much larger bounds, though they require more assumptions.
answered Aug 16 at 4:31
knzhouknzhou
55.1k14 gold badges156 silver badges265 bronze badges
$endgroup$
$begingroup$
Can you suggest me some reference where I can look up how the Equivalence Principle tests can be interpreted as putting bounds on a long-range fifth force?
$endgroup$
– Dvij Mankad
Aug 16 at 4:59
1
$begingroup$
Another example: Earth-Moon distance measured with a laser. Distance about 3e10 cm, measured with a few cm accuracy I think. Should investigate more to be sure.
$endgroup$
– thermomagnetic condensed boson
Aug 16 at 8:47
$begingroup$
Electrical neutrality of bulk matter: That only proves the equality of the charges if the number of electrons and protons in bulk matter is the same - but if the charge on the electron was 1.1 times that on the proton, I would expect bulk matter to have about 10% more electrons and still be neutral.
$endgroup$
– Martin Bonner
Aug 16 at 13:03
$begingroup$
Update: the ohm is now defined in terms of the elementary charge
$endgroup$
– gen-z ready to perish
Aug 21 at 6:11
$begingroup$
@gen-z Not particularly - in actual metrological practice, it's rather more accurate to say that the coulomb is defined in terms of the ohm.
$endgroup$
– Emilio Pisanty
Aug 21 at 10:20
add a comment |
$begingroup$
A few more candidates:
- The quantized Hall resistance is a great and surprising example, since it's an emergent property of rather complicated, "dirty" systems. As stated here (2013) one can measure the resistance to one part in $3 times 10^10$. For this reason this effect is now used to define the Ohm.
- Equivalence principle tests using torsion balances reached precisions of about one part in $10^11$ in $1964$, see here. Another existing answer gives a more precise result from a more modern experiment. These can be thought of as either verifying the equality of gravitational and inertial mass, or placing bounds on the strength of long-range fifth forces.
- The electrical neutrality of bulk matter follows because the electron and proton have exactly opposite charges. Treating the charge of the electron as given, tests of neutrality effectively measure the charge of the proton, with one experiment achieving a sensitivity of one part in $10^21$ in $1973$. Arguments from cosmology can be used to set much larger bounds, though they require more assumptions.
answered Aug 16 at 4:31
knzhouknzhou
55.1k14 gold badges156 silver badges265 bronze badges
$endgroup$
$begingroup$
Can you suggest me some reference where I can look up how the Equivalence Principle tests can be interpreted as putting bounds on a long-range fifth force?
$endgroup$
– Dvij Mankad
Aug 16 at 4:59
1
$begingroup$
Another example: Earth-Moon distance measured with a laser. Distance about 3e10 cm, measured with a few cm accuracy I think. Should investigate more to be sure.
$endgroup$
– thermomagnetic condensed boson
Aug 16 at 8:47
$begingroup$
Electrical neutrality of bulk matter: That only proves the equality of the charges if the number of electrons and protons in bulk matter is the same - but if the charge on the electron was 1.1 times that on the proton, I would expect bulk matter to have about 10% more electrons and still be neutral.
$endgroup$
– Martin Bonner
Aug 16 at 13:03
$begingroup$
Update: the ohm is now defined in terms of the elementary charge
$endgroup$
– gen-z ready to perish
Aug 21 at 6:11
$begingroup$
@gen-z Not particularly - in actual metrological practice, it's rather more accurate to say that the coulomb is defined in terms of the ohm.
$endgroup$
– Emilio Pisanty
Aug 21 at 10:20
add a comment |
$begingroup$
A few more candidates:
- The quantized Hall resistance is a great and surprising example, since it's an emergent property of rather complicated, "dirty" systems. As stated here (2013) one can measure the resistance to one part in $3 times 10^10$. For this reason this effect is now used to define the Ohm.
- Equivalence principle tests using torsion balances reached precisions of about one part in $10^11$ in $1964$, see here. Another existing answer gives a more precise result from a more modern experiment. These can be thought of as either verifying the equality of gravitational and inertial mass, or placing bounds on the strength of long-range fifth forces.
- The electrical neutrality of bulk matter follows because the electron and proton have exactly opposite charges. Treating the charge of the electron as given, tests of neutrality effectively measure the charge of the proton, with one experiment achieving a sensitivity of one part in $10^21$ in $1973$. Arguments from cosmology can be used to set much larger bounds, though they require more assumptions.
answered Aug 16 at 4:31
knzhouknzhou
55.1k14 gold badges156 silver badges265 bronze badges
$endgroup$
A few more candidates:
- The quantized Hall resistance is a great and surprising example, since it's an emergent property of rather complicated, "dirty" systems. As stated here (2013) one can measure the resistance to one part in $3 times 10^10$. For this reason this effect is now used to define the Ohm.
- Equivalence principle tests using torsion balances reached precisions of about one part in $10^11$ in $1964$, see here. Another existing answer gives a more precise result from a more modern experiment. These can be thought of as either verifying the equality of gravitational and inertial mass, or placing bounds on the strength of long-range fifth forces.
- The electrical neutrality of bulk matter follows because the electron and proton have exactly opposite charges. Treating the charge of the electron as given, tests of neutrality effectively measure the charge of the proton, with one experiment achieving a sensitivity of one part in $10^21$ in $1973$. Arguments from cosmology can be used to set much larger bounds, though they require more assumptions.
answered Aug 16 at 4:31
knzhouknzhou
55.1k14 gold badges156 silver badges265 bronze badges
edited Aug 16 at 4:36
answered Aug 16 at 4:31
knzhouknzhou
55.1k14 gold badges156 silver badges265 bronze badges
answered Aug 16 at 4:31
knzhouknzhou
55.1k14 gold badges156 silver badges265 bronze badges
answered Aug 16 at 4:31
knzhouknzhou
55.1k14 gold badges156 silver badges265 bronze badges
55.1k14 gold badges156 silver badges265 bronze badges
$begingroup$
Can you suggest me some reference where I can look up how the Equivalence Principle tests can be interpreted as putting bounds on a long-range fifth force?
$endgroup$
– Dvij Mankad
Aug 16 at 4:59
1
$begingroup$
Another example: Earth-Moon distance measured with a laser. Distance about 3e10 cm, measured with a few cm accuracy I think. Should investigate more to be sure.
$endgroup$
– thermomagnetic condensed boson
Aug 16 at 8:47
$begingroup$
Electrical neutrality of bulk matter: That only proves the equality of the charges if the number of electrons and protons in bulk matter is the same - but if the charge on the electron was 1.1 times that on the proton, I would expect bulk matter to have about 10% more electrons and still be neutral.
$endgroup$
– Martin Bonner
Aug 16 at 13:03
$begingroup$
Update: the ohm is now defined in terms of the elementary charge
$endgroup$
– gen-z ready to perish
Aug 21 at 6:11
$begingroup$
@gen-z Not particularly - in actual metrological practice, it's rather more accurate to say that the coulomb is defined in terms of the ohm.
$endgroup$
– Emilio Pisanty
Aug 21 at 10:20
add a comment |
$begingroup$
Can you suggest me some reference where I can look up how the Equivalence Principle tests can be interpreted as putting bounds on a long-range fifth force?
$endgroup$
– Dvij Mankad
Aug 16 at 4:59
1
$begingroup$
Another example: Earth-Moon distance measured with a laser. Distance about 3e10 cm, measured with a few cm accuracy I think. Should investigate more to be sure.
$endgroup$
– thermomagnetic condensed boson
Aug 16 at 8:47
$begingroup$
Electrical neutrality of bulk matter: That only proves the equality of the charges if the number of electrons and protons in bulk matter is the same - but if the charge on the electron was 1.1 times that on the proton, I would expect bulk matter to have about 10% more electrons and still be neutral.
$endgroup$
– Martin Bonner
Aug 16 at 13:03
$begingroup$
Update: the ohm is now defined in terms of the elementary charge
$endgroup$
– gen-z ready to perish
Aug 21 at 6:11
$begingroup$
@gen-z Not particularly - in actual metrological practice, it's rather more accurate to say that the coulomb is defined in terms of the ohm.
$endgroup$
– Emilio Pisanty
Aug 21 at 10:20
$begingroup$
Can you suggest me some reference where I can look up how the Equivalence Principle tests can be interpreted as putting bounds on a long-range fifth force?
$endgroup$
– Dvij Mankad
Aug 16 at 4:59
$begingroup$
Can you suggest me some reference where I can look up how the Equivalence Principle tests can be interpreted as putting bounds on a long-range fifth force?
$endgroup$
– Dvij Mankad
Aug 16 at 4:59
1
1
$begingroup$
Another example: Earth-Moon distance measured with a laser. Distance about 3e10 cm, measured with a few cm accuracy I think. Should investigate more to be sure.
$endgroup$
– thermomagnetic condensed boson
Aug 16 at 8:47
$begingroup$
Another example: Earth-Moon distance measured with a laser. Distance about 3e10 cm, measured with a few cm accuracy I think. Should investigate more to be sure.
$endgroup$
– thermomagnetic condensed boson
Aug 16 at 8:47
$begingroup$
Electrical neutrality of bulk matter: That only proves the equality of the charges if the number of electrons and protons in bulk matter is the same - but if the charge on the electron was 1.1 times that on the proton, I would expect bulk matter to have about 10% more electrons and still be neutral.
$endgroup$
– Martin Bonner
Aug 16 at 13:03
$begingroup$
Electrical neutrality of bulk matter: That only proves the equality of the charges if the number of electrons and protons in bulk matter is the same - but if the charge on the electron was 1.1 times that on the proton, I would expect bulk matter to have about 10% more electrons and still be neutral.
$endgroup$
– Martin Bonner
Aug 16 at 13:03
$begingroup$
Update: the ohm is now defined in terms of the elementary charge
$endgroup$
– gen-z ready to perish
Aug 21 at 6:11
$begingroup$
Update: the ohm is now defined in terms of the elementary charge
$endgroup$
– gen-z ready to perish
Aug 21 at 6:11
$begingroup$
@gen-z Not particularly - in actual metrological practice, it's rather more accurate to say that the coulomb is defined in terms of the ohm.
$endgroup$
– Emilio Pisanty
Aug 21 at 10:20
$begingroup$
@gen-z Not particularly - in actual metrological practice, it's rather more accurate to say that the coulomb is defined in terms of the ohm.
$endgroup$
– Emilio Pisanty
Aug 21 at 10:20
add a comment |
$begingroup$
A good candidate is the measurement of the fine structure constant $alpha$. This wiki article on precision tests of QED states that:
The agreement found this way is to within ten parts in a billion ($10^−8$), based on the comparison of the electron anomalous magnetic dipole moment and the Rydberg constant from atom recoil measurements...
There is also an upper bound on the mass of the photon, which is in the range of $10^-27eV/c^2$ although that's an upper bound rather than a measurement since the expected value is $0$.
answered Aug 16 at 4:01
ZeroTheHeroZeroTheHero
22.7k5 gold badges34 silver badges69 bronze badges
$endgroup$
1
$begingroup$
The ratio of the gravitational to inertial mass was verified to be unity within $1$ in $10^15$ in $2017$ by the MICROSCOPE satellite: en.wikipedia.org/wiki/MICROSCOPE_(satellite)
$endgroup$
– Dvij Mankad
Aug 16 at 4:04
$begingroup$
@DvijMankad this ought to be an answer then...
$endgroup$
– ZeroTheHero
Aug 16 at 4:07
$begingroup$
I think it could be added as a possible answer but I am not sure if there exist more precise measurements in particle physics, maybe some electroweak precision measurements?
$endgroup$
– Dvij Mankad
Aug 16 at 4:08
1
$begingroup$
@DvijMankad I do believe the only way a question like this can be answered on StackExchange is to put forth the best answer an individual may know, and the best answer will get upvoted. (And I highly doubt a good answer will be downvoted just because somebody finds a better answer)
$endgroup$
– Cort Ammon
Aug 16 at 4:10
1
$begingroup$
@CortAmmon Makes sense. Done! :-)
$endgroup$
– Dvij Mankad
Aug 16 at 4:13
|
show 1 more comment
$begingroup$
A good candidate is the measurement of the fine structure constant $alpha$. This wiki article on precision tests of QED states that:
The agreement found this way is to within ten parts in a billion ($10^−8$), based on the comparison of the electron anomalous magnetic dipole moment and the Rydberg constant from atom recoil measurements...
There is also an upper bound on the mass of the photon, which is in the range of $10^-27eV/c^2$ although that's an upper bound rather than a measurement since the expected value is $0$.
answered Aug 16 at 4:01
ZeroTheHeroZeroTheHero
22.7k5 gold badges34 silver badges69 bronze badges
$endgroup$
1
$begingroup$
The ratio of the gravitational to inertial mass was verified to be unity within $1$ in $10^15$ in $2017$ by the MICROSCOPE satellite: en.wikipedia.org/wiki/MICROSCOPE_(satellite)
$endgroup$
– Dvij Mankad
Aug 16 at 4:04
$begingroup$
@DvijMankad this ought to be an answer then...
$endgroup$
– ZeroTheHero
Aug 16 at 4:07
$begingroup$
I think it could be added as a possible answer but I am not sure if there exist more precise measurements in particle physics, maybe some electroweak precision measurements?
$endgroup$
– Dvij Mankad
Aug 16 at 4:08
1
$begingroup$
@DvijMankad I do believe the only way a question like this can be answered on StackExchange is to put forth the best answer an individual may know, and the best answer will get upvoted. (And I highly doubt a good answer will be downvoted just because somebody finds a better answer)
$endgroup$
– Cort Ammon
Aug 16 at 4:10
1
$begingroup$
@CortAmmon Makes sense. Done! :-)
$endgroup$
– Dvij Mankad
Aug 16 at 4:13
|
show 1 more comment
$begingroup$
A good candidate is the measurement of the fine structure constant $alpha$. This wiki article on precision tests of QED states that:
The agreement found this way is to within ten parts in a billion ($10^−8$), based on the comparison of the electron anomalous magnetic dipole moment and the Rydberg constant from atom recoil measurements...
There is also an upper bound on the mass of the photon, which is in the range of $10^-27eV/c^2$ although that's an upper bound rather than a measurement since the expected value is $0$.
answered Aug 16 at 4:01
ZeroTheHeroZeroTheHero
22.7k5 gold badges34 silver badges69 bronze badges
$endgroup$
A good candidate is the measurement of the fine structure constant $alpha$. This wiki article on precision tests of QED states that:
The agreement found this way is to within ten parts in a billion ($10^−8$), based on the comparison of the electron anomalous magnetic dipole moment and the Rydberg constant from atom recoil measurements...
There is also an upper bound on the mass of the photon, which is in the range of $10^-27eV/c^2$ although that's an upper bound rather than a measurement since the expected value is $0$.
answered Aug 16 at 4:01
ZeroTheHeroZeroTheHero
22.7k5 gold badges34 silver badges69 bronze badges
edited Aug 16 at 4:06
answered Aug 16 at 4:01
ZeroTheHeroZeroTheHero
22.7k5 gold badges34 silver badges69 bronze badges
answered Aug 16 at 4:01
ZeroTheHeroZeroTheHero
22.7k5 gold badges34 silver badges69 bronze badges
answered Aug 16 at 4:01
ZeroTheHeroZeroTheHero
22.7k5 gold badges34 silver badges69 bronze badges
22.7k5 gold badges34 silver badges69 bronze badges
1
$begingroup$
The ratio of the gravitational to inertial mass was verified to be unity within $1$ in $10^15$ in $2017$ by the MICROSCOPE satellite: en.wikipedia.org/wiki/MICROSCOPE_(satellite)
$endgroup$
– Dvij Mankad
Aug 16 at 4:04
$begingroup$
@DvijMankad this ought to be an answer then...
$endgroup$
– ZeroTheHero
Aug 16 at 4:07
$begingroup$
I think it could be added as a possible answer but I am not sure if there exist more precise measurements in particle physics, maybe some electroweak precision measurements?
$endgroup$
– Dvij Mankad
Aug 16 at 4:08
1
$begingroup$
@DvijMankad I do believe the only way a question like this can be answered on StackExchange is to put forth the best answer an individual may know, and the best answer will get upvoted. (And I highly doubt a good answer will be downvoted just because somebody finds a better answer)
$endgroup$
– Cort Ammon
Aug 16 at 4:10
1
$begingroup$
@CortAmmon Makes sense. Done! :-)
$endgroup$
– Dvij Mankad
Aug 16 at 4:13
|
show 1 more comment
1
$begingroup$
The ratio of the gravitational to inertial mass was verified to be unity within $1$ in $10^15$ in $2017$ by the MICROSCOPE satellite: en.wikipedia.org/wiki/MICROSCOPE_(satellite)
$endgroup$
– Dvij Mankad
Aug 16 at 4:04
$begingroup$
@DvijMankad this ought to be an answer then...
$endgroup$
– ZeroTheHero
Aug 16 at 4:07
$begingroup$
I think it could be added as a possible answer but I am not sure if there exist more precise measurements in particle physics, maybe some electroweak precision measurements?
$endgroup$
– Dvij Mankad
Aug 16 at 4:08
1
$begingroup$
@DvijMankad I do believe the only way a question like this can be answered on StackExchange is to put forth the best answer an individual may know, and the best answer will get upvoted. (And I highly doubt a good answer will be downvoted just because somebody finds a better answer)
$endgroup$
– Cort Ammon
Aug 16 at 4:10
1
$begingroup$
@CortAmmon Makes sense. Done! :-)
$endgroup$
– Dvij Mankad
Aug 16 at 4:13
1
1
$begingroup$
The ratio of the gravitational to inertial mass was verified to be unity within $1$ in $10^15$ in $2017$ by the MICROSCOPE satellite: en.wikipedia.org/wiki/MICROSCOPE_(satellite)
$endgroup$
– Dvij Mankad
Aug 16 at 4:04
$begingroup$
The ratio of the gravitational to inertial mass was verified to be unity within $1$ in $10^15$ in $2017$ by the MICROSCOPE satellite: en.wikipedia.org/wiki/MICROSCOPE_(satellite)
$endgroup$
– Dvij Mankad
Aug 16 at 4:04
$begingroup$
@DvijMankad this ought to be an answer then...
$endgroup$
– ZeroTheHero
Aug 16 at 4:07
$begingroup$
@DvijMankad this ought to be an answer then...
$endgroup$
– ZeroTheHero
Aug 16 at 4:07
$begingroup$
I think it could be added as a possible answer but I am not sure if there exist more precise measurements in particle physics, maybe some electroweak precision measurements?
$endgroup$
– Dvij Mankad
Aug 16 at 4:08
$begingroup$
I think it could be added as a possible answer but I am not sure if there exist more precise measurements in particle physics, maybe some electroweak precision measurements?
$endgroup$
– Dvij Mankad
Aug 16 at 4:08
1
1
$begingroup$
@DvijMankad I do believe the only way a question like this can be answered on StackExchange is to put forth the best answer an individual may know, and the best answer will get upvoted. (And I highly doubt a good answer will be downvoted just because somebody finds a better answer)
$endgroup$
– Cort Ammon
Aug 16 at 4:10
$begingroup$
@DvijMankad I do believe the only way a question like this can be answered on StackExchange is to put forth the best answer an individual may know, and the best answer will get upvoted. (And I highly doubt a good answer will be downvoted just because somebody finds a better answer)
$endgroup$
– Cort Ammon
Aug 16 at 4:10
1
1
$begingroup$
@CortAmmon Makes sense. Done! :-)
$endgroup$
– Dvij Mankad
Aug 16 at 4:13
$begingroup$
@CortAmmon Makes sense. Done! :-)
$endgroup$
– Dvij Mankad
Aug 16 at 4:13
|
show 1 more comment
$begingroup$
To answer the question from a different angle, LIGO has measured gravitational waves several times over the last few years. To do so they have to observe a distortion in a 4km arm, in the order of $10^-18$m. In other words, it has to detect a fractional imprecision in its length of ~$2.5 * 10^-23$. That's pretty accurate.
answered Aug 16 at 12:49
WittierDinosaurWittierDinosaur
191 bronze badge
$endgroup$
2
$begingroup$
LIGO is extremely sensitive, but pretty inaccurate, its calibration has an uncertainty of a few percent.
$endgroup$
– Bas Swinckels
Aug 16 at 13:05
1
$begingroup$
Thank you for the answer! What Bas Swinckles mentions is something I was trying to avoid when crafting the criteria of the question. The 4km long arm is not what LIGO actually measures, but rather the 10^-18m number is what is being measured. LIGO was one heck of a feat, but I was trying to avoid high-sensitivity/low-accuracy measurements because we can always come up with a "higher" value by comparing it against something bigger.
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– Cort Ammon
Aug 16 at 15:22
add a comment |
$begingroup$
To answer the question from a different angle, LIGO has measured gravitational waves several times over the last few years. To do so they have to observe a distortion in a 4km arm, in the order of $10^-18$m. In other words, it has to detect a fractional imprecision in its length of ~$2.5 * 10^-23$. That's pretty accurate.
answered Aug 16 at 12:49
WittierDinosaurWittierDinosaur
191 bronze badge
$endgroup$
2
$begingroup$
LIGO is extremely sensitive, but pretty inaccurate, its calibration has an uncertainty of a few percent.
$endgroup$
– Bas Swinckels
Aug 16 at 13:05
1
$begingroup$
Thank you for the answer! What Bas Swinckles mentions is something I was trying to avoid when crafting the criteria of the question. The 4km long arm is not what LIGO actually measures, but rather the 10^-18m number is what is being measured. LIGO was one heck of a feat, but I was trying to avoid high-sensitivity/low-accuracy measurements because we can always come up with a "higher" value by comparing it against something bigger.
$endgroup$
– Cort Ammon
Aug 16 at 15:22
add a comment |
$begingroup$
To answer the question from a different angle, LIGO has measured gravitational waves several times over the last few years. To do so they have to observe a distortion in a 4km arm, in the order of $10^-18$m. In other words, it has to detect a fractional imprecision in its length of ~$2.5 * 10^-23$. That's pretty accurate.
answered Aug 16 at 12:49
WittierDinosaurWittierDinosaur
191 bronze badge
$endgroup$
To answer the question from a different angle, LIGO has measured gravitational waves several times over the last few years. To do so they have to observe a distortion in a 4km arm, in the order of $10^-18$m. In other words, it has to detect a fractional imprecision in its length of ~$2.5 * 10^-23$. That's pretty accurate.
answered Aug 16 at 12:49
WittierDinosaurWittierDinosaur
191 bronze badge
answered Aug 16 at 12:49
WittierDinosaurWittierDinosaur
191 bronze badge
answered Aug 16 at 12:49
WittierDinosaurWittierDinosaur
191 bronze badge
answered Aug 16 at 12:49
WittierDinosaurWittierDinosaur
191 bronze badge
191 bronze badge
2
$begingroup$
LIGO is extremely sensitive, but pretty inaccurate, its calibration has an uncertainty of a few percent.
$endgroup$
– Bas Swinckels
Aug 16 at 13:05
1
$begingroup$
Thank you for the answer! What Bas Swinckles mentions is something I was trying to avoid when crafting the criteria of the question. The 4km long arm is not what LIGO actually measures, but rather the 10^-18m number is what is being measured. LIGO was one heck of a feat, but I was trying to avoid high-sensitivity/low-accuracy measurements because we can always come up with a "higher" value by comparing it against something bigger.
$endgroup$
– Cort Ammon
Aug 16 at 15:22
add a comment |
2
$begingroup$
LIGO is extremely sensitive, but pretty inaccurate, its calibration has an uncertainty of a few percent.
$endgroup$
– Bas Swinckels
Aug 16 at 13:05
1
$begingroup$
Thank you for the answer! What Bas Swinckles mentions is something I was trying to avoid when crafting the criteria of the question. The 4km long arm is not what LIGO actually measures, but rather the 10^-18m number is what is being measured. LIGO was one heck of a feat, but I was trying to avoid high-sensitivity/low-accuracy measurements because we can always come up with a "higher" value by comparing it against something bigger.
$endgroup$
– Cort Ammon
Aug 16 at 15:22
2
2
$begingroup$
LIGO is extremely sensitive, but pretty inaccurate, its calibration has an uncertainty of a few percent.
$endgroup$
– Bas Swinckels
Aug 16 at 13:05
$begingroup$
LIGO is extremely sensitive, but pretty inaccurate, its calibration has an uncertainty of a few percent.
$endgroup$
– Bas Swinckels
Aug 16 at 13:05
1
1
$begingroup$
Thank you for the answer! What Bas Swinckles mentions is something I was trying to avoid when crafting the criteria of the question. The 4km long arm is not what LIGO actually measures, but rather the 10^-18m number is what is being measured. LIGO was one heck of a feat, but I was trying to avoid high-sensitivity/low-accuracy measurements because we can always come up with a "higher" value by comparing it against something bigger.
$endgroup$
– Cort Ammon
Aug 16 at 15:22
$begingroup$
Thank you for the answer! What Bas Swinckles mentions is something I was trying to avoid when crafting the criteria of the question. The 4km long arm is not what LIGO actually measures, but rather the 10^-18m number is what is being measured. LIGO was one heck of a feat, but I was trying to avoid high-sensitivity/low-accuracy measurements because we can always come up with a "higher" value by comparing it against something bigger.
$endgroup$
– Cort Ammon
Aug 16 at 15:22
add a comment |
$begingroup$
Another quantity that is well known is the frequency of the 21 cm line of Hydrogen hyperfine splitting that has been measured to about 13 significant figures, 1420405751.7667±0.0009 Hz. Unlike the electron magnetic moment, mentioned in another answer, the QED calculation for hyperfine splitting is not as accurate. This calculation also depends on other fundamental constants, including electron/proton mass ratio and proton magnetic moment. which are not known to equivalent precision.
answered Aug 16 at 15:45
amateurAstroamateurAstro
5091 gold badge1 silver badge7 bronze badges
$endgroup$
add a comment |
$begingroup$
Another quantity that is well known is the frequency of the 21 cm line of Hydrogen hyperfine splitting that has been measured to about 13 significant figures, 1420405751.7667±0.0009 Hz. Unlike the electron magnetic moment, mentioned in another answer, the QED calculation for hyperfine splitting is not as accurate. This calculation also depends on other fundamental constants, including electron/proton mass ratio and proton magnetic moment. which are not known to equivalent precision.
answered Aug 16 at 15:45
amateurAstroamateurAstro
5091 gold badge1 silver badge7 bronze badges
$endgroup$
add a comment |
$begingroup$
Another quantity that is well known is the frequency of the 21 cm line of Hydrogen hyperfine splitting that has been measured to about 13 significant figures, 1420405751.7667±0.0009 Hz. Unlike the electron magnetic moment, mentioned in another answer, the QED calculation for hyperfine splitting is not as accurate. This calculation also depends on other fundamental constants, including electron/proton mass ratio and proton magnetic moment. which are not known to equivalent precision.
answered Aug 16 at 15:45
amateurAstroamateurAstro
5091 gold badge1 silver badge7 bronze badges
$endgroup$
Another quantity that is well known is the frequency of the 21 cm line of Hydrogen hyperfine splitting that has been measured to about 13 significant figures, 1420405751.7667±0.0009 Hz. Unlike the electron magnetic moment, mentioned in another answer, the QED calculation for hyperfine splitting is not as accurate. This calculation also depends on other fundamental constants, including electron/proton mass ratio and proton magnetic moment. which are not known to equivalent precision.
answered Aug 16 at 15:45
amateurAstroamateurAstro
5091 gold badge1 silver badge7 bronze badges
answered Aug 16 at 15:45
amateurAstroamateurAstro
5091 gold badge1 silver badge7 bronze badges
answered Aug 16 at 15:45
amateurAstroamateurAstro
5091 gold badge1 silver badge7 bronze badges
answered Aug 16 at 15:45
amateurAstroamateurAstro
5091 gold badge1 silver badge7 bronze badges
5091 gold badge1 silver badge7 bronze badges
add a comment |
add a comment |
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@Qmechanic Mind explaining why you felt this needed to be put on hold via a mod hammer, when there were clearly good answers coming forth, and everyone seems to agree upon what is meant? In fact, with 6 upvotes and 33 views, it seems people seem to feel this is a good question.
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– Cort Ammon
Aug 16 at 5:54
1
$begingroup$
Shouldn't the title refer to precision rather than accuracy?
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– Gremlin
Aug 16 at 13:02
5
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Discussion about this question on meta.
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– Emilio Pisanty
Aug 16 at 13:41
1
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@Gremlin Updated. You're right, I was lazy in my wording. "precision" is a better word choice
$endgroup$
– Cort Ammon
Aug 16 at 15:35