And now for something completely different. The hairs of the polar bear are transparent light pipes that direct ultraviolet light to its skin -- which.

And now for something completely different

The hairs of the polar bear are transparent light pipes that direct ultraviolet light to its skin -- which is guess what color? Black! So what’s white and black and warm all over? A polar bear under the arctic sun.

Paul G. Hewitt, Conceptual Physics, 6th Edition, 1989, p. 501

Polar bear fiber optics,twenty years later:

Fuzzy Wuzzy wasn’t photonic,

was he?Daniel W. Koon

Department of PhysicsSt. Lawrence University

Special thanks to:Reid Hutchins, SLU ‘98Michael Owen, SLU GeologyCatherine Jahncke, SLU PhysicsKaren Johnson, SLU PhysicsJohn Scott Foster, Seneca Park Zoo, Rochester, NYCraig Bohren, Penn StateDavid Lavigne, Guelph, Ontario

Wherever Nils goes, his bear is sure to follow. Nils Are Øritsland found this three-month old cub in early spring, tamed it, and named it Douglas before discovering it was a female. Polar bear cubs are born hairless, blind, and weighing about half a pound. Alaskan Eskimos call them ah tik tok, meaning “those that go down to the sea”.

“Polar Bear: Lonely Nomad of the North”, National Geographic 139:4, 574 (April 1971).

“Dr. Langley invented the bolometerA curious sort of thermometer

It can measure the heatFrom a polar bear’s seat

At a distance of half a kilometer.”

Unknown, Applied Optics 19 (3), 403 (1980).

Lavigne, D. M. and Øritsland, N. A., "Black Polar Bears", Nature 251, 218-9 (1974).

Lavigne, D. M. and Øritsland, N. A., "Black Polar Bears", Nature 251, 218-9 (1974).

Factoid #1

Seals, polar bears, NATO Arctic camouflage paint all appear highly reflecting (“white”) in the visible, but poorly reflecting (“black”) in the ultraviolet.

For more of the history of this factoid, see, for example, D. W. Koon, “The power of the polar myth”, New Scientist, April 25, 1998, p. 50.

The fiber-optic myth. I:The engineers

Who? R. E. Grojean, J. A. Sousa, M. C. Henry

What? Measured reflectivity, studied individual polar bear hairs

When? Mid 1970’sWhere? Northeastern University and the US

Army Research and Development Lab, Natick, MA

Why? To understand how the polar bear pelt changes reflectivity so dramatically in going from the visible to the UV

Reflectance of polar bear and seal pelts

Grojean, R. E.; Sousa, J. A.; and Henry, M. C., “Utilization of solar radiation by polar animals: an optical model for pelts”, Appl. Opt. 19, 339 (1980).

Structure of a polar bear hair

Grojean, R. E.; Sousa, J. A.; and Henry, M. C., “Utilization of solar radiation by polar animals: an optical model for pelts”, Appl. Opt. 19, 339 (1980).

Hairs of polar bear (top), pig (bottom)

Tributsch, H., Glosowsky, H., Küppers, U., and Wetzel, H., “Light collection and sensing through the polar bear pelt”, Sol. Energy Mater. 21, 219 (1990).

Factoid #2Polar bear hairs are not white, but transparent: light can be transmitted across the width of a single hair.

“The efficiency of transmission of solar radiation to the skin must be particularly high for the UV, since the pelts appear black when viewed in the UV while the hairs themselves appear quite transparent.”

Conclusion: The hairs guide UV to the skin.

The relevant scientific literature:

Grojean, R. E., Sousa, J. A., and Henry, M. C., “Utilization of solar radiation by polar animals: an optical model for pelts”, Appl. Opt. 19, 339 (1980).

Bohren, Craig F. and Sardie, Joseph M., “Utilization of solar radiation by polar animals: an optical model for pelts; an alternative explanation”, Appl. Opt. 20, 1894 (1981).

Grojean, R. E., Sousa, J. A., and Henry, M. C., “Utilization of solar radiation by polar animals: an optical model for pelts; authors’ reply to an alternative explanation”, Appl. Opt. 20, 1896 (1981).

Tributsch, H., Glosowsky, H., Küppers, U., and Wetzel, H., “Light collection and sensing through the polar bear pelt”, Sol. Energy Mater. 21, 219 (1990).

Koon, Daniel W., "Is polar bear hair fiber optic?", Applied Optics 37, 3198 (1998).

Objections to the fiber optic theory:

The Arctic is poor in UV, and when the bears most need it, even less is available.

How does light entering the fibers from random directions get launched down the hair?

How does the light “know” to travel toward the skin rather than away from it?

Why is UV guided fiber-optically down the hair, but visible light is not?

Keratin, a protein that makes up all hair, is known to be strongly absorbing in the UV, but relatively transparent in the visible.

Absorption in various amino acids

“Biophysical Chemistry: Principles, Techniques & Applications”, Alan G. Marshall (John Wiley & Sons, NY: 1978), p. 399

Some of the popular literature:

Time Magazine, Dec. 4, 1978.Natural History, Oct. 1981.Science News, March 8, 1986.“Arctic Dreams”, Barry Lopez, 1986.Christian Science Monitor, Dec. 1, 1987.Scientific American, March 1988.National Public Radio’s “All Things Considered”, March

5, 1995.Polar bear exhibit, New England Science Center,

Worcester, MA.

For the bibliography to end all bibliographies, go to http://it.stlawu.edu/~koon/mar_ref.html.

Examples from the popular literature

Time Magazine, Dec. 4, 1978. See http://it.stlawu.edu/ ~koon/polar.html for more references.

More popular literature,closer to home

"Polar bears ... have a thick coat of hollow hair that traps any solar heat, allowing absorption of the heat into their black skin."

The Alaska Zoo (Anchorage), http://www.alaskazoo.com/polar_bears.htm

The fiber-optic myth. II:The 95% solution

"[Grojean, Gregory Kowalski and Charles DiMarzio] have discovered that the shaggy fur of polar bears is 95 percent efficient in converting the sun's ultraviolet rays into usable heat." Grow, Glenn S., "Warming up to polar bears' solar secrets", The Christian Science Monitor, Dec. 1, 1987, p. 19.

"Through thermal balance equations, Grojean calculated that the bears trap 90 percent of ultraviolet light and 17 percent from the entire solar spectrum. The figures were confirmed by an Irish Arctic research team in the early '80s." Croke, Vicki, "Solar Polar Bears? Two Boston Scientists Think So.", Boston Globe, June 4, 1990, p. 41.

"[T]he hair...collects heat...[H ]airs change 95% of the sun's rays to heat." Brown, Gary, "The Great Bear Almanac" (Lyons & Burford: New York, 1993), p. 68.

The fiber-optic myth. II:The 95% solution

This 95% figure is never directly claimed in the technical literature

Unless you count this....

“A rudimentary calculation of the amount of solar energy available (i.e., not reflected) for heating, based on the measured reflection coefficient of the pelt, indicates a avalue of 0.324 cal/cm2-min compared with 0.307 cal/cm2-min measured at the skin by Oritsland.” (Grojean et al., Appl. Opt. 19, 339 (1980).)

The fiber-optic myth. III:Saved by fluorescence?

Tributsch, H., Glosowsky, H., Küppers, U., and Wetzel, H., “Light collection and sensing through the polar bear pelt”, Sol. Energy Mater. 21, 219 (1990).

The fiber-optic myth. IV:Medical applications

"Polar-bear fur: good for more than rugs", Chronicle of Higher Education, March 17, 1995.

“Aristotle maintained that women have fewer teeth than men; although he was twice married, it never occurred to him to verify this statement by examining his wives’ mouths.”

Bertrand Russell

“Mrs. Aristotle’s mouth”:The tabletop version

Length of hair Output light15mm Dim, red10mm Brighter, golden7mm Brighter still, yellow

Hair courtesy of John Scott Foster, Seneca Park Zoo,Rochester, NY

Attenuation spectrum, polar bear

FOUL(UP):A Fiber-Optic Ursine Link (Universal Prototype)

for telecommunications

D. W. Koon and C. L. Jahncke, Physics Dept., St. Lawrence University

ABSTRACT: We have constructed what we believe is the first prototype of a fiber-optic link to use the hair of an Arctic mammal. The potential advantages of ursine fiber technology over conventional technology are discussed.

http:// it.stlawu.edu/~physics/clj/foulup.html

FOUL(UP): experimental setup

Laser

Microscope objective

Ursine fiber-optic link

Silicon-diode sensor

Laser power supply

http://it.stlawu.edu/~physics/clj/foulup.html

FOUL(UP): output signal

Filtered output of the sensor for a laser signal modulated at 102kHz.

Specs: 4mm length of hair3mW, 650nm laser input3% output at 102kHz

http://it.stlawu.edu/~physics/clj/foulup.html

Conclusions:

Polar bear hair is a lousy optical fiber in the visible and even worse in the UV: if “fiber optics” explained the black appearance of polar bears in the UV, then it would “explain” the bears into being black in the visible as well.

Publishing in the popular media is a dangerous business. You are as likely to spread ignorance as wisdom.

Not even peer review can stop bad science.

Public outreach needs to include teaching the public to be skeptical of what we say.