Posts Tagged ‘time’

Google Talk

25 Aug

I gave a tech talk at Google headquarters on the arrow of time, which was a lot of fun. Must be what all of Silicon Valley was like back in the boom days — pool tables, free food, volleyball, and lots of smart people everywhere. Rather than a lecture hall, the talks are held in a big lobby space where people are regularly walking through, so that passers-by can become intrigued and start listening. Also, it became clear during the questions that at least one Google employee is concerned about how to preserve intelligent life past the 10100 year mark when our universe will be nothing but empty space. Glad they’re thinking long-term!

Here is the talk, which is basically at a popular level, although I felt empowered to use the word “logarithm” without explanation. I’ve also tried to collect other talks by me onto one page, for those who just can’t get enough. (Hi, Mom!)


Scientists Measure Shortest Interval of Time Ever

29 Jul

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