Nanoparticle trapped with laser light temporarily violates the second law of thermodynamics

[n2doc]

Objects with sizes in the nanometer range, such as the molecular building blocks of living cells or nanotechnological devices, are continuously exposed to random collisions with surrounding molecules. In such fluctuating environments the fundamental laws of thermodynamics that govern our macroscopic world need to be rewritten. An international team of researchers from Barcelona, Zurich and Vienna found that a nanoparticle trapped with laser light temporarily violates the famous second law of thermodynamics, something that is impossible on human time and length scale.

They report about their results in the latest issue of the prestigious scientific journal Nature Nanotechnology.

Surprises at the nanoscale
Watching a movie played in reverse often makes us laugh because unexpected and mysterious things seem to happen: glass shards lying on the floor slowly start to move towards each other, magically assemble and suddenly an intact glass jumps on the table where it gently gets to a halt. Or snow starts to from a water puddle in the sun, steadily growing until an entire snowman appears as if molded by an invisible hand. When we see such scenes, we immediately realize that according to our everyday experience something is out of the ordinary. Indeed, there are many processes in nature that can never be reversed. The physical law that captures this behavior is the celebrated second law of thermodynamics, which posits that the entropy of a system – a measure for the disorder of a system – never decreases spontaneously, thus favoring disorder (high entropy) over order (low entropy).

However, when we zoom into the microscopic world of atoms and molecules, this law softens up and looses its absolute strictness. Indeed, at the nanoscale the second law can be fleetingly violated. On rare occasions, one may observe events that never happen on the macroscopic scale such as, for example heat transfer from cold to hot which is unheard of in our daily lives. Although on average the second law of thermodynamics remains valid even in nanoscale systems, scientists are intrigued by these rare events and are investigating the meaning of irreversibility at the nanoscale.

more

http://phys.org/news/2014-03-nanoparticle-laser-temporarily-violates-law.html#ajTabs

[phantom power]

1. This doesn't seem too surprising. The 2nd Law is driven by probabiity.

In macroscopic systems, the weight of probability is so laughably in favor increasing entropy that a spontaneous reversal simply isn't ever observed. At nano-scale, the systems are a lot smaller. The probability of a reversal is larger, as there are many, many fewer elements in the system.

[Chathamization]

2. Fluctuation theorems have been around for some time

and follow naturally from the statistical mechanics interpretation of the second law. It also always bothers me when entropy is referred to as disorder.

[DetlefK]

3. Gay-Lussac's Gedankenexperiment with finite number of particles.

Put very short: Of your system only contains a finite number of particles, it's possible that all the air goes back into the balloon by adding up random movements.