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Website Of Francis Redfern
Professor of Physics, Emeritus

Sound Science Bite: August 19. The Old Man and the Sea

There is a puzzle about how some microorganisms in the ocean manage to get the nutrients they need. Take the bacterium Prochlorococcus marina for example. This photosynthetic microbe is responsible for producing about 25% of the oxygen released to the atmosphere – not an insignificant contribution to life on the planet. The problem: It needs to absorb 400 million molecules of ammonium ions a day to get the nitrogen necessary to divide and reproduce, but the volume of seawater that holds that many ions is hundreds of millions of times its size. Even if it were to swim at a rapid pace for a microorganism, it would never be able to encounter that many ions.

Enter Einstein. He proved the existence of atoms and molecules to the satisfaction of the majority of scientists by studying Brownian motion. Although he didn't discover this motion (three guesses for the name of the person who did and the last two don't count), he was able to characterize it statistically to show that it could be explained by the existence of molecules. Brownian motion involves how dust particles seen under a microscope can be jiggled and moved around by collisions with molecules. Dust particles are small enough that they normally get more collisions from one direction than from another.

An article in the 2017 August 18 issue of the journal Science by Jonathan Zehr, Joshua Weitz, and Ian Joint points out that this motion solves the problem of how microbes like P. marina can get the nitrogen they need. By being jostled around by molecular collisions, these little guys can encounter four times the amount of ammonium ions necessary for reproduction. Brownian motion is important for other microbial life in the ocean also. As Zeir, Weitz, and Joint write, "[Brownian motion] alone can fuel the growth and reproductivity of abundant, free-living unicellular microorganisms in the open ocean." (Note: Einstein wasn't old but actually quite young when he published his work on Brownian motion.)

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Science News from the American Association for the Advancement of Science

I-10, On Road To Big Bend

Thrust Fault On Us 90

Grapevine Hills

South Rim Trail - Intruded Sediments

South Rim - Igneous Intrusions

Boot Canyon

Boquillas Canyon Fault

Fossil Near Hot Springs

Volcanic Rock In Tuff Canyon

Rio Grande Terraces

Burro Mesa Pouroff

Inside A Thrust Fault At Dog Canyon

Faulted Fold At Persimmon Gap

Lava Flow Over Alluvium, Rancherias Canyon

Sitting On A Dike By A Fault Scarp- Lost Mine Trail

Native American Petroglyphs - Chimneys

Oak Creek Pouroff - Only Water Outlet From The Basin

Carousel Mountain - Dodson Trail

Del Rio Clay On Santa Elena Limestone - Ernst Tinaja

Calcite Crystals - Near Mule Ear Peaks

On Mesa De Anguila

Pliocene-Miocene Contact - Estufa Canyon

"Hitchcock Rock" - Blue Creek Canyon

Outcrop - Telephone Canyon

Septarian Concretions - Banta Shut-In

Tornillo Graben

Cattail Falls

Giant Dagger at Devils Den

Mule Ear Peaks

Thrust Fault Drag Folds - Strawhouse Trail

Dike Swarm Radiating from Dominguez Mountain