The 



Toughest * 

 Glue On 

 Planet 



UNIVERSE (Continued from page 29) 



Extra Thick. Extra Stick. 



New Gorilla Tape sticks to thin] 

 ordinary tapes simply 



Mmm 



PICTURE CREDITS Cover and pp. 32-33: 

 Benjamin Edwards/Courtesy of Greenberg 

 VanDoren Gallery; pp. 4-5: ©Theo Allots; 

 p. 10: Jonny Hawkins; p. 14 (top) Greg Sword; 

 p. 14 (bottom) illustration by Mauricio Anton; 

 p. 15 (top): The British Library/Topham- 

 HIP/The Image Works; p. 15 (bottom): Joris 

 Koene and Cathy Levesque; pl6 (top): Joe 

 McDonald/Animals Animals/Earth Scenes; 

 p. 16 (bottom): Jan Hevelius 17th century; 

 p. 18 illustration by Christos Magganas; pp. 

 30-31: illustrations by Emily S Damstra; 

 pp.34-35: illustrations by Flying Chilli Ltd; 

 pp.36, 37, 53, and 57: illustrations by Ian 

 Worpole; p.38: Reprinted with permission 

 from Al Seckel, The Great Book of Optical Il- 

 lusions, Firefly Books, 2002; pp.48-49: pho- 

 tographs courtesy the author; pp.50-51: illus- 

 trations by Alan Baker; p.55: Jay H. Matternes 

 © 1991; p.56: illustrations by Viktor Deak, 

 after John G. Fleagle, Primate Adaptation and 

 Evolution; p.58: ©Mark A. Klmgler/CMNH; 

 p.59: illustration by Laura Hartman Maestro; 

 p.60 (top): Lynn Mc Bride/The Nature Con- 

 servancy; p.60 (bottom): John Karges/The 

 Nature Conservancy; p.61 (left): Tom Vezo; 

 p. 61 (right) map by Joe LeMonnier; p.62: 

 Steven Haddock; p.63: © Ah Atay / Im- 

 ages&Stories; p.70: NASA-JPL; p.75: F. Espe- 

 nak, NASA's GSFC; p.80: photograph cour- 

 tesy the author 



But perhaps the most far-reaching and 

 successful solution to the most funda- 

 mental and persistent problem en- 

 countered by the space sciences — de- 

 tecting the bucket of light — has been 

 the charge-coupled device, or CCD. 



A CCD is a light sensor made of a 

 tiny silicon chip, subdivided into a grid 

 of hundreds of thousands or even mil- 

 lions of extremely sensitive "picture el- 

 ements" — a term shortened in 1969 to 

 "pixel." Each pixel is like a little well, 

 holding a cache of electrons. Nearly 

 every time a photon hits a pixel, an elec- 

 tron gets kicked up out of the well, 

 where it waits to be counted. At the end 

 of each exposure, hardware and soft- 

 ware associated with the CCD do just 

 that. Counting and remembering all 

 the electrons from each well yields a grid 

 of: numbers that captures the brightness 

 ot the object, region by region. 



The efficiency of today's best CCDs 

 exceeds 90 percent: for every hundred 

 photons that land on the CCD, at least 

 ninety get recorded. By comparison, 

 the emulsions on the best photo- 

 graphic plates register no more than 

 one in a hundred photons. In other 

 words, a one-hour exposure for a CCD 

 is the equivalent, in detection sensitiv- 

 ity, to a hundred hours of exposure for 

 a photographic plate. And unless 

 you're at or near Earth's poles, nights 

 don't last that long. 



The CCD has transformed astro- 

 physics. If you can detect 90 percent 

 of the available light, why worry about 

 the rest? And if you attach a relatively 

 inexpensive CCD to a backyard tele- 

 scope, you can wield as much detec- 

 tion power as astrophysicists did thirty 

 years ago, equipped with some of the 

 best telescopes in the world. 



Another virtue of the CCD is that 

 the picture is born digital, making it a 

 cinch to work with the data. Say your 

 picture looks almost uniformly gray; 

 maybe the number of electrons per 

 pixel covers the narrow range from 990 

 to 1,010. But maybe some important 

 science can be gleaned from those vari- 

 ations. So, for the display screen, you 

 assign black to 990 and white to 1 ,010, 



and you lay the entire gray scale be- 

 tween those two extremes. Suddenly 

 995 looks very different from 1,000. 

 What was previously a nearly uniform 

 image now has bright and dark spots 

 popping out everywhere. And if your 

 data happen to measure temperature, 

 and you assign colors to the gray 

 scale — say, blue for coldest and red for 

 warmest — you might even end up 

 with an image that resembles the un- 

 precedentedly detailed portrait of the 

 cosmic microwave background made 

 in 2003. 



During the twentieth century the 

 astrophysicist's toolbox grew ex- 

 ponentially. Telescopes and detectors 

 now tune to every band of light across 

 the electromagnetic spectrum, from 

 radio waves through gamma rays. Mul- 

 tiple telescopes, arrayed across dozens 

 and, in some cases, thousands of miles, 

 are electronically linked to make an in- 

 terferometer that mimics the resolu- 

 tion of a single telescope as wide as the 

 array itself. 



Other telescopes orbit high above 

 Earth's turbulent atmosphere. The 

 exorbitant cost of putting them there 

 has prompted the growth of ground- 

 based adaptive optics: systems of sen- 

 sors that continuously monitor at- 

 mospheric turbulence and feed their 

 data to telescopes that can actively 

 compensate for changing conditions. 

 The cnspness of the resulting images 

 rivals that of images from spaceborne 

 telescopes. 



Sky watchers, no longer constrained 

 by the narrow vistas of a world with- 

 out spyglasses, now delight in one 

 where countless outsize telescopes, on 

 Earth and in the heavens, leave no cos- 

 mic vista unobserved. 



Astrophysicist Neil deGrasse Tyson is 

 the director of the Hayden Planetarium at the 

 American Museum of Natural History. His 

 Natural History essay "In the Beginning" 

 (September 2003) won the 2005 Science 

 Writing Award from the American Institute 

 of Physics. An anthology of his Natural His- 

 tory essays will be published in 2006 by 

 WW Norton. 



NAIUKAI HISIORY March 2006 



