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At the end of June this year, those who do this sort of thing will add an extra second to the world’s official clocks to keep us on the right track.
This gets a bit detailed — which is where the fun is! — but in short it goes like this. We have two systems to measure time: our everyday one which is based on the rotation of the Earth, and a fancy-schmancy scientific and precise one based on vibrations of atoms. The two systems aren’t quite in synch, though, since the Earth counts a day as a tiny bit longer than the atomic clocks say it is. So every now and again, to get them back together, we add a leap second on to the atomic clocks. That holds them back for one second, and then things are lined up once again.
This has to be done every two or three years, so why not just adjust the length of a day or year or something? The detailed explanation is at Bad Astronomy. Link
German scientists hit electrons with light and then measured how they soon they moved. The delay between the bombardment and the movement of those electrons is the shortest interval of time ever measured, which is 20 attoseconds. An attosecond is one quintillionth of a second.
When light is absorbed by atoms, the electrons become excited. If the light particles, so-called photons, carry sufficient energy, the electrons can be ejected from the atom. This effect is known as photoemission and was explained by Einstein more than hundred years ago. Until now, it has been assumed that the electron start moving out of the atom immediately after the impact of the photon. This point in time can be detected and has so far been considered as coincident with the arrival time of the light pulse, i.e. with “time zero” in the interaction of light with matter.
The scientists tested the assumption, and this is what happened:
Their measurements revealed that electrons from different atomic orbitals, although excited simultaneously, leave the atom with a small but measurable time delay of about twenty attoseconds.
In the comments, provide practical illustrations of the shortest intervals of time.
Link via Popular Science | Photo: Thorsten Naeser / Max-Planck-Institute of Quantum Optics
John Madden of GeekDad relates the story of how the ‘smoot’ became a measurement of distance:
Way back in 1958, the MIT chapter of the Lambda Chi Alpha fraternity used pledge Oliver R. Smoot to measure the Harvard Bridge in Massachusetts, coining the smoot as a unit of measurement in the process – one smoot equaling five feet, seven inches. Smoot (the man) lay down on the bridge, his position was marked, and he moved on (or was moved on – eventually he so tired from the movement that his frat brothers carried him), until the bridge was established as being 364.4 smoots, plus or minus an ear, in length. Appropriately, Smoot would later become chairman of the American National Standards Institute.
Madden then passes on ten more recent forms of measurement, including some of his own devising. These include the milliwheaton (number of Twitter followers), the Warhol (fame duration), and the Emmet (power). The latter comes from the movie Back to the Future:
1 Emmet = 1.21 Gigawatts, or the amount of power required to operated the flux capacitor in a modified DeLorean DMC-12. GeekDad note – when describing the Emmet, it’s pronounced ‘Jigga’ watt. There was briefly some debate as to whether this should be called a ‘lloyd’ or a docbrown’, But for simplicity (and to honour the character rather than the actor – though don’t get me wrong, Christopher Lloyd rocks) I’ve gone for ‘Emmet’.
In the comments, propose Neatorama-themed measurements.
Link | Images: MIT and Universal Studios, respectively
