#brownian motion #diffusion #humans

Humans are superdiffusive

When tea is poured in a cup of hot water, we observe a phenomenon called diffusion: in the end particles of tea spread evenly throughout the mass of water and we enjoy our cup of tea. Diffusion occurs as a result of the second law of thermodynamics (increase of entropy) and can be modeled quantitatively using the diffusion equation (or heat equation). This is a funny equation, since it establishes that the velocity of spreading is infinite while the mean root square fluctuations of the position of the particles grows in time as ...

#curiosity #glaciers

Meet the glaciers

I have been on holidays during the last two weeks visiting Argentina. The picture above was taken on top of the Perito Moreno glacier, which is amazing. Most glaciers we found where blueish, including the icebergs found floating in the rivers. The reason for that is that the thicker the ice or snow layer is, the better red colors are absorbed by the layer and only the blue colors are reflected (see a more detailed explanation here). Ice in the freezer looks transparent or white because its thickness is small enough to make the absorption of the red colors negligible. ...

#curiosity

Folding paper

You can’t fold a paper more than seven or eight times. Don’t believe me? Then try it. Thinner paper? Longer paper? It doesn’t matter; you just can’t do it. I used to play this game with my friends which were always amazed and asked for an explanation. Is there any physical or mathematical constrain to do it? Nope: it is simply a matter of scale. If you have a paper of length L and you fold it, the length now is L/2. Do it again and it goes down to L/22. In general, if you fold it n times, the remaining length is ...

#email #marketing #response rate

Why I didn’t answer your email

In a recent Nature article, Albert-Lászlo Barabási and João Gama Oliveira, have found the perfect excuse for lazy people not answering some emails in their inbox: they analyzed the time response of emails and found that they follow a power law probability distribution of the form P(t) = 1/t. In particular this implies that not even the mean response time is finite. Hey! why should you then expect me to answer your emails within my lifetime period! The usual buzz after the publication in Nature reach other scientific and non-scientific publications. ...

#bibliometrics #h-index

A number to rank them all

UCSD physicist Jorge E. Hirsch has propose a quick-and-dirty way to measure quality of academic scientist’s output. His method is explained and studied in a paper to be published in the November 15 issue of PNAS. The idea is very simple and it is called the h-index. This number relies on the number of citations our papers have. In particular the h-index is the maximum number h that verifies the following: at least h of papers of an author have h citations each. The method to calculate the number is fast (via the Thomson ISI Web of Science database) and he claims can tell apart good professional careers from a lifetime of mediocre work skewed by one or two highly cite papers. Let’s run the numbers to see how some people in the statistical physics community does: ...