Featured Research

from universities, journals, and other organizations

Converting Brownian motion into work: Classical thought experiment brought to life in granular gas

Date:
June 19, 2010
Source:
Stichting FOM
Summary:
Researchers have for the first time experimentally shown, almost a century later, an idea dating from 1912. In that year the physicist Smoluchowski devised a prototype for an engine at the molecular scale in which he thought he could ingeniously convert Brownian motion into work. The team of scientists have now successfully constructed this device at the much larger scale of a granular gas.

The thought experiment is brought to life in a granular gas: the experimental setup (left) and the device in operation (right).
Credit: Image courtesy of Stichting FOM

Researchers from the University of Twente, the University of Patras in Greece and the Foundation for Fundamental Research on Matter (FOM) have for the first time experimentally realized, almost a century later, an idea dating from 1912. In that year the physicist Smoluchowski devised a prototype for an engine at the molecular scale in which he thought he could ingeniously convert Brownian motion into work. The team of scientists has now successfully constructed this device at the much larger scale of a granular gas.

Moreover, they have shown that an intriguing exchange takes place between the vanes of the engine and the granular gas: once the vanes have started rotating, they in turn induce a rotating motion in the gas, a so-called convection roll. This reinforces the movement of the device and allows for a virtually continuous rotation. FOM PhD student Peter Eshuis and his colleagues published their results on June 16, 2010 online in the journal Physical Review Letters.

Molecular motors, such as those responsible for tensing and relaxing your muscles, move in a strange manner: they propel themselves forwards despite -- or thanks to -- a continuous bombardment of the randomly moving molecules in their surroundings. This random movement is called Brownian motion, and a well-constructed motor at the nanoscale actually makes use of this to generate a directed movement (and therefore work).

The device introduced by the physicist Marian Smoluchowski in 1912, as a thought experiment, is a classical example of such a motor. It consists of a series of vanes mounted on an axis, which are set in motion under the influence of the molecular bombardment. As this motion would take place in both rotational directions, Smoluchowski devised a second element, an asymmetrical cog. This would ensure that the axis could only rotate in a single direction and could therefore perform work, for example by pulling a small weight up. However, in 1963 Richard Feynman demonstrated that the second law of thermodynamics would prevent the device from working in a system that was in a state of thermal equilibrium, and with this, the thought experiment appeared to have been consigned to the waste bin.

Yet the objection formulated by Feynman does not apply to a system far removed from a thermal equilibrium, such as a granular gas. Researchers from the University of Twente, the University of Patras and FOM have now successfully demonstrated that Smoluchowski's thought experiment works superbly in this environment.

Brownian motion

Imagine that you are driving your car through a storm with hailstones as big as footballs. Every time that such a hailstone hits you, the impact propels you forwards, backwards or sideways, with the result that you stagger forwards across the road like a drunkard. A far-fetched example? Not on the molecular scale: there (due to the continual collisions with the surrounding molecules) all particles move in this manner, a phenomenon termed Brownian motion.

Granular gas

If a container filled with beads is vigorously vibrated on top of a shaking device, the beads move so fast that a gaseous state of rapidly moving beads arises. In many ways this state is similar to the molecular gaseous state. However, there exists one major difference with a molecular gas: when you stop shaking, the beads will lose their energy in a very short space of time and come to lie motionless on the bottom of the container. This happens because a bit of energy is lost in each collision between two beads. A constant supply of energy is therefore needed to maintain the granular gaseous state and this explains why this system remains far from thermal equilibrium.


Story Source:

The above story is based on materials provided by Stichting FOM. Note: Materials may be edited for content and length.


Journal Reference:

  1. Peter Eshuis, Ko van der Weele, Detlef Lohse and Devaraj van der Meer. Experimental Realization of a Rotational Ratchet in a Granular Gas. Phys. Rev. Lett., 104, 248001 (2010) DOI: 10.1103/PhysRevLett.104.248001

Cite This Page:

Stichting FOM. "Converting Brownian motion into work: Classical thought experiment brought to life in granular gas." ScienceDaily. ScienceDaily, 19 June 2010. <www.sciencedaily.com/releases/2010/06/100618103651.htm>.
Stichting FOM. (2010, June 19). Converting Brownian motion into work: Classical thought experiment brought to life in granular gas. ScienceDaily. Retrieved September 30, 2014 from www.sciencedaily.com/releases/2010/06/100618103651.htm
Stichting FOM. "Converting Brownian motion into work: Classical thought experiment brought to life in granular gas." ScienceDaily. www.sciencedaily.com/releases/2010/06/100618103651.htm (accessed September 30, 2014).

Share This



More Matter & Energy News

Tuesday, September 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Do Video Games Trump Brain Training For Cognitive Boosts?

Do Video Games Trump Brain Training For Cognitive Boosts?

Newsy (Sep. 29, 2014) — More and more studies are showing positive benefits to playing video games, but the jury is still out on brain training programs. Video provided by Newsy
Powered by NewsLook.com
CERN Celebrates 60 Years of Science

CERN Celebrates 60 Years of Science

Reuters - Business Video Online (Sep. 29, 2014) — CERN, the European Organisation for Nuclear Research, celebrates 60 years of bringing nations together through science. As Joanna Partridge reports from inside the famous science centre it's also planning to turn the Large Hadron Collider particle accelerator back on after an upgrade. Video provided by Reuters
Powered by NewsLook.com
This 'Invisibility Cloak' Is Simpler Than Most

This 'Invisibility Cloak' Is Simpler Than Most

Newsy (Sep. 28, 2014) — Researchers from the University of Rochester have created a type of invisibility cloak with simple focal lenses. Video provided by Newsy
Powered by NewsLook.com
New Corvette Can Secretly Record Convos And Get You Arrested

New Corvette Can Secretly Record Convos And Get You Arrested

Newsy (Sep. 28, 2014) — The 2015 Corvette features valet mode – which allows the owner to secretly record audio and video – but in many states that practice is illegal. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins