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Stopping In Thin Air

Imagine you're going very fast -- much faster than a race car. In fact, imagine you're going 100 or 200 times faster than a race car. When you reach your destination, you need to stop relatively quickly. How would you do it? It wouldn't take a rocket scientist to think of using the brakes. But, it might take a rocket scientist to skip the brakes, ...

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StoppingInThinAir
Biology

How Do They Grow Those Colossal Pumpkins?

Those enormous pumpkins that set records every fall are living proof that both genes and environment make living things what they are. Home gardeners out to break the 2002 record for the world's ... Continue reading

ColossalPumpkins
Physics

The Doppler Effect

As any object moves through the air, the air near the object is disturbed. The disturbances are transmitted through the air at a distinct speed called the speed of sound, because sound itself is just ... Continue reading

TheDopplerEffect
Geology

Is Earth Getting Fatter Around the Belt?

Besides being used for transmission of this email message to you, communication satellites are used for some neat science. By shooting a laser beam onto them and measuring how long it takes for light ... Continue reading

EarthBelt
Geology

Haleakala Crater

Modern geology indicates that the Hawaiian Islands are situated near the middle of the Pacific Plate, one of a dozen thin, rigid structures covering our planet like the cracked shell of an egg. Though ... Continue reading

HaleakalaCrater

Yes! We Have New Bananas

YesWeHaveNewBananasDid you know that a plant disease determined what banana variety is in your market? Bananas, which originated in Africa and are now grown in every tropical region, are perhaps the most popular fruit in the world. It is the most popular fruit in the U.S. even though we import nearly all of them. In addition to dessert bananas, the banana family also includes plantains, cooking bananas and abaca, a fiber plant called Manilla hemp. For many years the most popular banana sold in the United States was the variety 'Gros Michel', a preferred banana for shipping. However, 'Gros Michel' is very susceptible to Panama disease, a vascular wilt caused by a soil fungus, Fusarium oxysporum f. sp. cubense. It kills the banana plants by infecting the xylem (the water-conducting tissue) and destroying the plant's ability to distribute water and minerals to its tissues.

For a long time, banana growers moved their plantations to new fields to escape the disease, but as these new plantations became infected the growers eventually ran out of new ground. As a result many 'Gros Michel' plantings were converted to the more resistant 'Cavendish' varieties, even though in time these bananas also became diseased. So this disease has determined what banana you can buy.

Panama disease, also known as Fusarium wilt, is believed to have originated in Asia but gets it name from the damage it caused to banana plantations in Panama, as well as in other Central American countries, in the early 1900s. Bananas must be replanted after fruit production. They are not perennial trees. Since bananas are propagated vegetatively by suckers from the base of the plant, the fungus rapidly spread throughout banana growing areas. Once in the soil, the fungus can survive for many years and is spread further by machinery, contaminated soil and water, and by other physical means.