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On September 17th, 1998 the Ithaca Journal ran its first "Ask A Scientist!" article in which Professor Neil Ashcroft , who was then the director of CCMR, answered the question "What is Jupiter made of?" Since then, we have received over 1,000 questions from students and adults from all over the world. Select questions are answered weekly and published in the Ithaca Journal and on our web site. "Ask A Scientist!" reaches more than 21,000 Central New York residents through the Ithaca Journal and countless others around the world throught the "Ask a Scientist!" web site.

Across disciplines and across the state, from Nobel Prize winning scientist David Lee to notable science education advocate Bill Nye, researchers and scientists have been called on to respond to these questions. For more than seven years, kids - and a few adults - have been submitting their queries to find out the answer to life's everyday questions.

Previous Week's Question Published: 8 January, 2004 Next Week's Question
Green vegetables are an example of edible fluorescents
Question
Are there any nontoxic ingestible fluorescent materials?

Question
There are lots of edible fluorescent materials! A fluorescent material absorbs light of one color and then emits (or gives off) light of a second color. Since the energy to create the emitted light must come from the absorbed light, the emitted light must have less energy than the absorbed light. Because of this, it is possible to absorb blue light (high energy) and emit red light (low energy); however, the reverse is impossible. Red light cannot be converted to blue light (unless high powered lasers are involved, but that is a different story.)

Perhaps the most common edible fluorescent molecule is chlorophyll - the molecule that makes spinach and grass green. Chlorophyll absorbs blue and red light very efficiently (which explains the deep green color of spinach), and emits very red, almost invisible, light.

Does this mean that chlorophyll containing plants, such as spinach, are also fluorescent? The answer is both yes and no. During the day, plants absorb light and use the light energy to manufacture sugar. This process is known as photosynthesis. Since the plant uses the absorbed light very quickly, almost none of the absorbed energy is available for fluorescence. Under these conditions, plants are not fluorescent. At night, the photosynthetic machinery is "turned off." If the plant is exposed to a short flash of blue light at night, a burst of fluorescence will be observed. (Unfortunately, this effect is too small to be seen by eye.)

Since there are edible fluorescent materials, are there also edible lasers? This burning scientific question was tackled by Arthur Schawlow, one of the inventors of the laser, and his students in 1970. To make their laser, they mixed sodium fluorescein, the dye used by ophthalmologists in some eye exams, with Knox gelatin. Under bright ultraviolet light (black light), "intense green beams emerged" from the gelatin. As a grad student, I was told that Prof. Schawlow then ate the new laser; however, I think this part of the story is apocryphal!

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