Scientists Calculate Most Precise Measurement of Electron's Mass

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."

So what's the mass then?

[Anonymous Coward]

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

Re:So what's the mass then?

[Anonymous Coward]

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?

[jmv]

Actually, the mass of a hydrogen atom isn't equal to the sum mass of the proton and that of the electron. There's a 13.6 eV binding energy (good 'ol E-mc^2) that needs to be taken into account. Considering that the 511 eV rest mass of the electron and the fact that we're taking about measurements that are supposed to be accurate to less than 1 part per billion, then the binding energy is pretty significant. I suspect there are other effects that also need to be taken into account.

Re:So what's the mass then?

[jmv]

Sorry, I meant to say 511 *keV* for the rest mass of the electron.

Re:

[AlabamaCajun]

LOL, 511eV, desktop particle physics?

Re:

[Sockatume]

This needs to be emphasised: laymen frequently don't really get just how equivalent the mass-energy equivalence is, that they're literally the same quantity. This is why sci-fi characters shouldn't (for example) convert their alien invasion fleet into energy and store it in a tiny cube and put it in their pocket; it still has all of its original mass-energy.

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[cellocgw]

This is why sci-fi characters shouldn't (for example) convert their alien invasion fleet into energy and store it in a tiny cube and put it in their pocket; it still has all of its original mass-energy.

Oh you silly 3-dimensioner! The tiny cube is merely the 3D representation of a portal into 9-D space where the invasion fleet is stored. The mass of the cube itself is less than 50TeV (I made that number up)

Re:

[AlabamaCajun]

To that effect, considering energy I would like to see results at high and a low energy states to determine if the added energy affects the weight. Photons are particles that are the energy carriers used to upstate the electron. Does this change also increase the weight electron or the atom?

Re:

[jmv]

Consider this, if an electron were to transition from "really far" down to the first energy level of the hydrogen atom, then the photon emitted would have an energy of 13.6 eV, and the mass of the resulting hydrogen atom would be 13.6 eV less than the sum of the original masses.

Re:So what's the mass then?

[fishybell]

1

The unit is SE, for Standard Electron

Re:So what's the mass then?

[davester666]

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

Re:

[Anonymous Coward]

I don't know where the parent poster got that number, but that is way too many digits, even considering the new precision the recent experiment added. As in, that is nearly 3 times as many digits as the error bars in the paper would suggest. They gave the measurement in two forms, the mass of the electron in atomic mass units: m_e = 0.000548579909067(14)(9)(2), and as the ratio of the proton mass to electron mass: m_p/m_e = 1836.15267377(17).

I find myself wondering...

[CrimsonAvenger]

...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...

[Baloroth]

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:

[oodaloop]

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:

[TrollstonButterbeans]

I think it is very accurate that your comment was rated Offtopic precisely because this article isn't about the value of PI.

Re:

[Workaphobia]

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?

DOI not found.

[MurukeshM]

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.

[Baloroth]

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:

[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.

[fahrbot-bot]

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...

[ackthpt]

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

Re:

[jones_supa]

Yeah, the Beta is morphing from a "complete trainwreck" to just a "garbage can". ;)

Now, I wish the full article summaries were shown in the front page.

Re:

[Soulskill]

If you switch the view to Classic using this dropdown menu [imgur.com], you should see full summaries rather than truncated ones.

I'm still arguing to get it changed/fixed for the default view.

Re:

[jones_supa]

Excellent, thanks!

Re:

[AlabamaCajun]

Wet farts have more electron weight than dry ones. Can we just ask that this beta sh!t be optional so that we can get on with life. Make the new one function like the new one and let users choose a color base. I like the dark because I can read is better with out all the white page burning out my retina.

I have a more precise measurement.

[PSXer]

It is exactly 1 electron mass.

Re:

[wonkey_monkey]

Is that an African electron or a European electron?

Re:

[dltaylor]

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

Calculate?

[pahles]

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.

[DoctorNathaniel]

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?

[bluefoxlucid]

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

[lkcl]

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