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Monday, April 11, 2005; Page A10

Galileo's Debt to the Poet

Galileo Galilee, the Italian physicist, astronomer and mathematician, may have unintentionally cribbed one of his greatest insights from a countryman who had been dead 300 years: the poet Dante Alighieri.

The description of Dante's descent from the seventh to the eighth circle of hell in "The Divine Comedy" involves the poet being transported on the wings of the monster Geryon. In a translation by Henry Wadsworth Longfellow, Dante describes the sensation of not knowing whether he was at rest or in motion after losing visual points of reference: "Onward he goeth, swimming slowly, slowly / Wheels and descends, but I perceive it only / By wind upon my face and from below."

The poet Dante, above, described a feeling that later became the basis for Galileo's theory of invariance.

In an unusual paper published last week in Nature, Leonardo Ricci of the University of Trento in Italy said Dante's description was identical to Galileo's observation that travelers on a ship often cannot tell without visual cues whether they are at rest or in motion.

Galileo backed up his observation with experiments to come up with his theory of invariance, which suggests the laws of physics remain unchanged by changes in velocity -- a principle whose limits become apparent only near the speed of light.

-- Shankar Vedantam

Algae Toxin Is Widespread

Algae that produce a toxin that may be linked to brain diseases such as Alzheimer's and Parkinson's are far more common than had been thought, researchers have found.

Scientists have known that some species of blue-green algae emit a toxin known as BMAA, which has been found in the brains of Alzheimer's patients in Canada and in people in Guam who died from a similar brain disease. That has led some researchers to speculate that the toxin may play a role in diseases such as Alzheimer's, Parkinson's and Lou Gehrig's.

Although the theory remains unproven, Paul Alan Cox of the National Tropical Botanical Garden in Kalaheo, Hawaii, and colleagues tried to assess how widespread the toxin is. The researchers found that samples from all five of the major types of blue-green algae, also known as cyanobacteria, produce BMAA, including 95 percent of the 30 varieties they studied from around the world.

Because cyanobacteria are among the most common organisms on Earth, the findings indicate that more research should be done to determine what role they may be playing in disease. The number of "blooms" of the organisms is expected to increase with global warming, the researchers noted.

"It may be now prudent to monitor BMAA concentrations in drinking waters contaminated by cyanobacteria blooms," they wrote in the April 5 Proceedings of the National Academy of Sciences.

"BMAA concentrations should also be monitored within invertebrates, fish, or grazing animals used for human consumption that either directly consume cyanobacteria or forage on plants or prey that may have accumulated cyanobacteria-produced BMAA."

-- Rob Stein

Sea Tour of Mayan Saltworks

What did the Mayans do in the days before Morton's?

Living far inland in what is now Mexico, Belize and Guatemala -- an area largely devoid of salt deposits -- the advanced civilization was in need of large supplies of sea salt. Until recently, however, scientists had discovered just four small saltworks on the Caribbean coast that appear to have been in the business of providing the precious commodity to the inland population.

Now an anthropologist at Louisiana State University has discovered 41 additional saltworks -- all a few feet underwater off the southeastern coast of the Yucatan peninsula, and all apparently geared toward supplying the interior with the crucial nutrient.

Knowing that sea level had risen several feet since the Late Classic Mayan period (600 to 900 A.D.), Heather McKillop and her colleagues methodically snorkeled the crystal-clear waters of Punta Ycacos Lagoon off Belize -- tough work, but someone had to do it. They watched for the telltale signs of a saltwater evaporation industry, such as bits of pottery, charcoal fire hearths, and wooden structures likely to be preserved in the oxygen-depleted peat of the shoreline mangrove stands.

They found plenty. The remains of the largest structure included 112 wooden posts that outline a building of more than 2,000 square feet with a variety of salt-making artifacts. Also discovered: a well-preserved, full-size canoe paddle, evidence of how the salt was transported upriver to the interior. McKillop reported the findings in last week's early online edition of the Proceedings of the National Academy of Sciences.

-- Rick Weiss

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