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## Scientists Calculate Most Precise Measurement of Electron's Mass59

Posted by samzenpus
from the step-on-the-scale dept.
sciencehabit writes "A team of physicists has produced the most precise electron mass measurement ever made. Instead of trying to measure the mass directly, the researchers bound a single electron to a bare carbon nucleus and placed the resulting atom in a uniform electromagnetic field called a Penning trap. The team's new measurement is 13 times more precise than previous efforts, with an uncertainty of just 0.03 parts per billion. The group's precise result will help physicists more accurately calculate the fine-structure constant, an important value in tests of the standard model of particle physics, which shapes our understanding of the basic building blocks of the universe."
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## Scientists Calculate Most Precise Measurement of Electron's Mass

• #### So what's the mass then? (Score:1)

by Anonymous Coward

TFA didn't post it, I'm curious what the actual measurement is.

• #### Re:So what's the mass then? (Score:5, Informative)

by Anonymous Coward on Wednesday February 19, 2014 @09:27PM (#46292137)
They determined the electron mass compared to that of a proton, so it depends on how accurate the proton mass has been determined.
• #### Re:So what's the mass then? (Score:4, Funny)

<(moc.liamtoh) (ta) (llebyhsif)> on Thursday February 20, 2014 @12:12AM (#46292713) Homepage Journal

1

The unit is SE, for Standard Electron

• #### Re:So what's the mass then? (Score:4, Funny)

on Thursday February 20, 2014 @12:40AM (#46292797) Journal

They have to run the test again. One of the researchers was looking at the electron when they took the measurement.

• #### I find myself wondering... (Score:2, Offtopic)

...if the authors of TFA and TFS are aware that there's a difference between "precise" and "accurate".

TFA seems to be trying to use "precise" to mean "both precise and accurate", TFS just summarizes TFA without noticing that there's a distinction to be made.

DO remember that there IS a difference:

3.14159 is much more precise than 3.14.

But if the actual value is 3.141, then 3.14 is more accurate than 3.14159.

And I'm betting that at least one /. entity is going to focus like a laser on 3.14159 being an ap

• #### Re:I find myself wondering... (Score:5, Insightful)

on Wednesday February 19, 2014 @09:46PM (#46292229)

I'm puzzled where you're seeing the confusion. TFA uses the term "precise" precisely (heh) as it is meant to be used: it tells you the uncertainty (known uncertainty, obviously, though you can throw in a "fudge factor" to account for unknown factors) in the measurement. It's not really possible to tell if the measurement is *accurate* except by comparing it to other measurements made by other teams, but given the higher level of precision in this experiment, that comparison is mostly useless (I'm assuming their data with error lies within the data with error of other measurements. If it didn't, that might end being much bigger news).

• #### Re: (Score:2)

It's just odd to hear only of precision. I can precisely tell you that the time is 9:14:12 on August 18 1912 BC. That's not even remotely accurate, but damn is it precise!

• #### Re: (Score:2)

Precision without accuracy is meaningless, hence the "significant digits" we were all taught in science class. Mentioning accuracy when bragging about precision would be redundant. Why split hairs?

I'm getting a DOI not found for the paper from TFS, the DOI being 10.1038/nature13026.
Does anyone know the correct identifier?

• #### Re:DOI not found. (Score:5, Informative)

on Wednesday February 19, 2014 @09:50PM (#46292247)

DOIs can take a few hours/days or so to start working in some cases, if the results were recently announced. While Slashdot covering recent news would be surprising, it's not totally unheard of.

• #### Re: (Score:1)

by Anonymous Coward

Here [nature.com] is a link using Nature's own DOI resolver and here [nature.com] is one to the final paper.

• #### Re:DOI not found. (Score:5, Funny)

on Thursday February 20, 2014 @01:01AM (#46292839)

I'm getting a DOI not found for the paper from TFS, the DOI being 10.1038/nature13026.
Does anyone know the correct identifier?

So, the DOI is precise and you're asking if it's accurate? :-)

• #### Rough measure... (Score:5, Funny)

on Wednesday February 19, 2014 @09:46PM (#46292221) Homepage Journal

...Slightly larger than a particle of commons sense, which is in such short supply these days.

• #### I have a more precise measurement. (Score:2)

It is exactly 1 electron mass.

• #### Re: (Score:3)

Is that an African electron or a European electron?

• #### Re: (Score:2)

Is that rest mass (to which GP SHOULD HAVE referred), or while migrating (with, or without, coconut)?

• #### Calculate? (Score:3)

on Thursday February 20, 2014 @02:35AM (#46293005)
How do you calculate a measurement? Or is it just me, not speaking English on a daily basis, getting in the way?
• #### Yeah, bad title. (Score:2)

You don't 'calculate' a measurement. Measurements often require some mathematics, but it's the incorrect verb. Calculations are theoretical.

• #### Can't we just change the fine structure constant? (Score:3)

on Thursday February 20, 2014 @08:42AM (#46294035) Journal
You'd only have to collapse the universe and then influence it at roughly the moment when it cooled down enough that photons had less mass than protons.
• #### link between mass value and avogadro's constant (Score:1)

well... this is puzzling. i tried converting the value reported to MeV and accidentally divided by the atomic units constant 9.109 382 91 x 10-31 instead. what i got shocked the hell out of me: 1000x avogadro's constant. according to reports here http://phys.org/news/2014-02-p... [phys.org] the value is 0.000548579909067 atomic mass units. if however you divide that by the atomic unit of mass reported here http://physics.nist.gov/cgi-bi... [nist.gov]|search_for=atomic+mass+unit you get, to 6 decimal places, avogadro's const

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