Did you know that there are units of time even smaller than seconds? Although for practical reasons we do not make use of them in our daily lives, in the field of scientific research they use them frequently. For example, a centisecond would be equal to one hundredth of a second, that is, it would be 0.01 seconds. And the nanosecond is equal to one billionth of a second, 0.000 000 001 seconds. But the thing goes even further.
Attoseconds are much smaller units than our heads and experience can even lead us to understand or imagine. An attosecond is equivalent to a time interval of 0.000000000000000001 seconds, or what is the same, a millionth of a billionth of a second . In fact, the ratio of an attosecond to a second is similar to the ratio of a second to the age of the universe (about fifteen billion years).
Thanks to these units of measurement, in 2010 it was possible to measure the shortest period of time controllable so far, making use of light and its dual nature of particle and electromagnetic wave to achieve this. And it is that, being a wave, the light has a wavelength (the distance that the disturbance of a wave travels) and a wave frequency (the number of times that wave is repeated per unit of time), measured in Hertz (Hz). This, the frequency , is the key to achieve the mentioned temporal measurements.
In the non-visible light spectrum (that which the human eye is not capable of perceiving) cosmic rays, gamma rays, X-rays and ultraviolet have a high wave frequency (that is, a wave is repeated many times per unit of time ), reaching over 10 exahertz. Progressively, this frequency decreases as the spectrum travels through infrared, microwave or radio waves.
For this reason, observing the behavior of light, it has been possible to carry out this type of measurements of very, very small units of time, inaccessible through any other method. Specifically, through lasers, which can generate light pulses of up to 100 attoseconds. But scientists from the Max Born Institute for Nonlinear Optics and Short-Time Spectroscopy (MBI) in Berlin (Germany) came to demonstrate in a study published in the journal Nature in 2010 a time control with a residual uncertainty of only 12 attoseconds , which is the world record for the shortest controllable timescale ever measured.
In general, light is a very high frequency electromagnetic wave, but this time an ultrashort laser pulse was used and specific stabilization methods were employed for the position of the maximum phase of the light pulse. A correction that is based on the so-called acoustic-optical frequency shifter and that brings real advances for this kind of research in nature.
Koke, S., Grebing, C., Frei, H. et al. Direct frequency comb synthesis with arbitrary offset and shot-noise-limited phase noise. NaturePhoton 4, 462–465 (2010). Doi: 10.1038/nphoton.2010.91
