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17 April 2014 12:48 pm ,
Vol. 344 ,
Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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ScienceShot: Trapped Electron Reveals Its Mass
19 February 2014 1:00 pm
The mass of an electron appears prominently in many of the fundamental laws that govern the subatomic realm, yet direct measurement has been complicated by the particle’s scrawny mass. Now, a team of physicists has overcome this challenge to produce 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 (created in an apparatus similar to the one pictured above). Inside the trap, the atom began oscillating in circles with a steady frequency. The team then shot the trapped atom with microwaves, causing the spin of the electron to flip up and down. By comparing the frequency of the atom's circular movements with the frequency of the spin-flipping microwaves, the team used quantum electrodynamics equations to derive the mass of the electron compared with a proton. The team's new measurement is 13 times more precise than previous efforts, with an uncertainty of just 0.03 parts per billion, the researchers report online today in Nature. 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.