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The Endless Pathways of Discovery

Floyd E. Bloom

Last month, Science selected the opportunities presented by research on embryonic stem cells as the latest of our Breakthroughs of the Year (Science, 17 December 1999, pp. 2238 and 2267). That discovery, like all scientific research, was possible only because of the previously accumulated body of scientific information, hypotheses, and tools of observation. Our annual selections of Breakthroughs are intended to draw attention to significant scientific achievement. But knowing that any annual retrospective is both temporally and substantively shortsighted, Science begins with this issue a "Pathways of Discovery" series as part of our yearlong special coverage of the transition into the next millennium.

For the remainder of 2000, the second issue of each month will include an essay portraying the pathways of discovery in exciting areas of investigation ranging from quantum physics to cosmology and from genomics to atmospheric sciences. For each topic covered, all of them coordinated by Contributing Editor Ivan Amato, distinguished scientists will review what they see as the major past heuristic accomplishments along the intellectual pathway they presently traverse, and they'll imagine the downstream terrain of that pathway through extrapolation from discoveries unfolding now.

The opening essay of this series, by Stephen Jay Gould (p. 253), is a provocative approach to the question of what distinguishes the scientific way of knowing about the world and what it is about that way of knowing that is all too human. Gould sees a false dichotomy in today's "science wars" between scientist-realists and humanist-relativists who question whether scientific truth has any special standing among other claims of truth. His assessments will prepare readers of subsequent essays for the mix of rational and nonrational influences that continually shape the ever more-revealing worldview scientists have been building.

To help lay out our year of Pathways essays, in this issue we have assembled a graphical timeline of major past events and agents of discovery. The points along the way were drawn from initial selections by Science's editors and then refined and vetted with the help of historians of science (the editors retain credit for any errors, omissions, or overemphases). From this overarching timeline of discovery, an at least arguable origin for each of the 11 essay topics to follow can be seen (p. 230). Each essay will include a more focused timeline depicting pathways of discoveries germane to the topic. In addition, through collaboration with the Encyclopedia Britannica, their Web site ( will enrich each month's essay with links to unique historical and other informational resources.

These timelines serve as convenient simplifications of the spectacular and progressive accumulation of insight and understanding scientists have achieved. A more detailed visual metaphor of this progress would look like an intricate circulatory system with multiple ever-finer branchings that often interconnect with other parts of the nexus. Science has indeed become a process of continuous specialization, yet each new capillary of investigation contributes to the overall understanding. As some of our essays will show, like that on genomics by Eric Lander and Robert Weinberg slated for March, each new branch of science can open wondrous new opportunities while posing societal challenges that will require vigilance and insightful management.

The unavoidable consequence of focusing on the pathways we have chosen to highlight in this series is the obligatory omission of the many, many other important pathways of discovery that deserved equal recognition in our homage to the past. Recognizing that a truly comprehensive portrayal of science's leading edges was beyond our resources, we opted for some themes that have figured prominently in our pages over the past decade as examples of the flows of ideas and technologies within and between the various pathways of science.

For this editor, the most remarkable conclusion to emerge from this exercise was the realization* that in the millennium we are about to leave, humanity's knowledge of its place in the universe has moved from St. Thomas Aquinas's view that knowledge was of two types--that which man could know and that which was "higher than man's knowledge" and not to be sought through reason--to the belief begun with Newton's Principia that our universe and all within it are indeed knowable. We eagerly await readers' views of our Pathways.

*A. Lightman, New York Times Magazine, 19 September 1999, p. 94.

Pathways of Discovery

To help readers negotiate Science magazine's yearlong series, Pathways of Discovery, we compiled this timeline. It leaves out far more than it includes, but we hope it--along with Stephen Jay Gould's provocative essay on page 253 and this issue's editorial by Science Editor-in-Chief Floyd Bloom--will give readers an idea of what to expect from this series. A schedule of the essay topics appear below.

1 "Science Wars" [Summary] [Full Text] January
2 Planetary Sciences February
3 Genomics March
4 Infectious Diseases April
5 Materials Science May
6 Cloning/Stem Cells June
7 Communications July
8 Quantum Physics August
9 The Cell Cycle September
10 Atmospheric Sciences October
11 Neuroscience November
12 Astrophysics/Cosmology December

Along the timeline, colored numbers and arrows mark points of departure. These are moments in the history of science where the pathways of discovery associated with each of the 12 topical essays in the series might have begun to unfold.

Prior to 600 B.C.
Prescientific Era
Phenomena explained within contexts of magic, religion, and experience.
6th Century B.C.
Greek philosophers begin constructing natural and rational explanations for phenomena.
582-500 B.C.
Recognizes connection between mathematics and nature.
"All is number."
5th to 4th Centuries B.C
Leucippus and Democritus
Articulate the earliest known version of atomism.
427-347 B.C.
Emphasizes the value of theory.
384-322 B.C.
Supports logic and common sense in the observation and classification of natural phenomena. His writings become a cornerstone of Western thinking for nearly 2000 years.
3rd to 2nd Centuries B.C.
Writes The Elements, one of the earliest logically built texts using axioms and logical deduction for geometric proofs.
Birth of alchemy
287-212 B.C.
Recognizes how theory can lead to technological insight.
Summarizes his geocentric astronomy, which reigns until Copernicus (1543).
Writes text on anatomy that is preeminent until Vesalius (1543).
Symbol for "zero" created in India
Mayan and Hindu skywatchers make astronomical observations for agricultural and religious purposes.
Oxford University is founded and becomes model for other European universities.
13th Century
Mechanical clocks proliferate
William of Ockham
Touts simplicity in explanation as a virtue.
Synchronization of clocks in Paris, an emblematic moment in the history of standardization.
Johannes Gutenberg
Demonstrates movable type printing press in Germany.
His anti-authoritarianism helps the West break loose from scholastic dogma.
Andreas Vesalius
Publishes De Corporis Humani Fabrica, displacing Galen as the authority on anatomy.
Nicolaus Copernicus
Publishes De Revolutionibus Orbium Coelestium, displacing geocentric (Ptolemaic) system with heliocentric system.
Tycho Brahe
Increases accuracy of astronomical observation.
Zacharias Janssen
Builds first microscope.
William Gilbert
Publishes De Magnete, in which he postulates that Earth behaves as a huge magnet.
Hans Lippershey
Manufactures first telescopes; originally used for military purposes.
Johannes Kepler
Publishes Astronomia Nova, in which he defines first two laws of planetary motion.
Galileo Galilei
With one of the first telescopes, he makes extensive astronomical observations; publishes Siderius Nuncius.
Francis Bacon
Publishes Novum Organum, in which he espouses careful observation and inductive reasoning as a basis of scientific study.
"I have taken all knowledge to be my province."
William Harvey
Publishes Exercitatio anatomica de motu cordis et sanguinis in animalibus, by which he establishes the basic geometry of the circulatory system.
René Descartes
His Discours de la Methode combines skepticism, algebra, and geometry into the powerful mathematical method of analysis.
Evangelista Torricelli
Invents the barometer.
"We live submerged at the bottom of an ocean of the element air."
Royal Society in England is legally chartered
Robert Boyle
Publishes The Sceptical Chymist, helping to establish a more modern basis for chemistry.
Anton van Leeuwenhoek
Uses simple microscope to magnify the world up to 200 times. In pond water, he sees tiny living organisms. A pathway to microbiology opens.
John Ray
Starts publishing a three- volume classification of 18,600 different plant species.
Isaac Newton
Publishes his Principia Mathematica, in which he lays out mathematically the laws of motion, universal gravitation, and the scientific method in general.
Edmund Halley
Predicts that a comet will return in 1758. When it does, it serves as a powerful demonstration of science's ability to understand the world.
Daniel Fahrenheit
Invents mercury thermometer and standardizes it with ice and boiling water.
Lady Mary Wortley Montagu
Introduces early technique of immunization.
Carolus Linnaeus
Publishes Systema Naturae, thereby greatly pushing forward systematic study and rules of classification of theliving kingdom.
Benjamin Franklin
Shows lightning to be an electrical discharge.
Halley's Comet returns
Kaspar Wolff
Shows that specialized organs develop out of unspecialized tissue, a pathway to developmental biology.
Antoine Lavoisier
Raises practice of making quantitative measurement in chemical studies to a level that earns him eternal credit as the father of modern chemistry.
Luigi Galvani
Observes connection between electricity and muscle action.
James Hutton
Publishes Theory of Earth, arguing for a picture of gradual, steady terrestrial changes that became known as uniformitarianism.
Metric system developed
... kilometer, meter, millimeter ...
James Hutton
Publishes Theory of Earth, arguing for a picture of gradual, steady terrestrial changes that became known as uniformitarianism.
Edward Jenner
Develops technique he called vaccination; the science of immunology begins.
Georges Cuvier
Publishes first work of comparative anatomy that would support the later evolutionists; his later work with fossils would found the field of paleontology.
Alessandro Volta
Invents the electric battery, thereby opening the way to several new sciences--including electrochemistry--and technologies.
John Dalton
Publishes New System of Chemical Philosophy, refining idea of atoms and how they combine.
Jean-Baptiste de Lamarck
Publishes Zoological Philosophy, in which he proposes that evolution occurs by the inheritance of traits acquired during lifetime.
1820 Hans Christian Oersted
Discovers connection between electricity and magnetism, that is, the basic principle of electromagnetism.
Friedrich Wöhler
Synthesizes an organic compound, urea, in the laboratory, thereby breaking down categorical distinction between life and nonlife.
Charles Lyell
Publishes first volume of The Principles of Geology.
Louis Agassiz
Argues for the existence of an ice age in the past.
Matthias Schleiden and Theodor Schwann
Develop cell theory -- that living things are made of cells.
"The elementary parts of all tissues are formed of cells in an analogous, though very diversified manner, so that it may be asserted that there is one universal principle of development for the elementary parts of organisms, however different, and that this principle is the formation of cells."
James Joule
Develops the concept of conservation of energy.
First electric telegraph
William Ferrel
Publishes Essay on the Winds and Currents of the Ocean, a pivotal work in the history of meteorology.
Charles Darwin
Publishes The Origin of Species.
Gregor Mendel
Publishes work containing his famous laws of heredity.
Henry Sorby
Emphasizes how material properties depend upon their internal microscopic structure.
Dmitri Mendeleev
Publishes his Periodic Table of the Chemical Elements.
Camillo Golgi
Uses techniques to lay bare the cellular anatomy of the brain.
Wilhelm Röntgen
Discovers x-rays.
Marie Curie
She and husband Pierre clarify concept of radioactivity as an atomic property.
J. J. Thomson
Discovers the electron.
Max Planck
Quantum science is born.
Albert Einstein
Develops Special Theory of Relativity; later (in 1916) publishes General Theory of Relativity.
Alfred Wegener
Proposes the continental drift theory.
Quantum mechanics emerges
Georges Lemaître
Introduces big bang theory.
Edwin Hubble
Successfully argues that the universe is expanding.
Linus Pauling
Updates chemistry with ideas of quantum mechanics.
Hans Spemann
Proposes the concept of cloning.
Birth of nuclear technology
William Shockley, Walter Brattain, and John Bardeen
Invent the transistor.
James Watson and Francis Crick
Publish the structure of DNA.
"It has not escaped our notice that the specific pairings we have postulated immediately suggests a possible copying mechanism for the genetic material."
Harry Hess, Dan McKenzie, Jason Morgan, and J. Tuzo Wilson
Develop theory of tectonic plates.
Soviets launch Sputnik.
Murray Gell-Mann
Postulates the existence of quarks.
Rachel Carson
Publishes Silent Spring, linking pesticide use to ecological ills.
The U.S. Department of Defense's Advanced Research Projects Agency creates ARPAnet, the precursor to the Internet and the World Wide Web.
Hamilton Smith and Daniel Nathans
Develop first recombinant DNA techniques.
The Standard Model of particle physics emerges
First commercial microprocessor manufactured.
Acquired immunodeficiency syndrome (AIDS) recognized.
Kary Mullis
Develops polymerase chain reaction (PCR).
Ozone hole discovered over Antarctica.
Human Genome Project begins.
World Wide Web demonstrated at
Bose-Einstein condensate created in laboratory.
Ian Wilmut and Keith Campbell
Clone a sheep from adult cells.

All-Too-Human Science

Pathways of discovery are only smooth and linear when the nuanced and tortuous history of science is brutally edited to fit into a finite space. The items to the right represent the countless twists, turns, ironies, contradictions, tragedies, and other unkempt historical details that have synthesized into the far more complex and multitextured reality of the scientific adventure.

4th century B.C.: Aristotle rejects the atomism of Leucippus and Democritus in favor of the five-element material system -- earth, air, fire, water, and ether. Atomism doesn't surface seriously for 2000 years. Meanwhile, the four-element philosophy spurs alchemical thought and practice. The power of authority often still poses obstacles to new ideas.

9th to 15th centuries: The flow of science and technology is mostly into Europe from Islam and China. Among the innovations diffusing westward: paper, chemical technology, glassmaking, the compass, shipbuilding, and gunpowder. In the 15th century, the centers of science and technology begin shifting to the West.

1543: Copernicus helps begin the scientific revolution with his heliocentric theory of the universe. Yet he retains the perfect circularity of orbits demanded by Platonic idealism and Ptolemaic astronomy. His work embodies both a radicalism that unlocks new knowledge and a conservatism. These together account for much of the progressive nature of scientific knowledge.

1633: The Holy Inquisition threatens Galileo Galilei with torture unless he renounces heliocentrism. He acquiesces but is confined to house arrest for the rest of his life for previously defying Church authority by publicly promoting the theory. The Galileo affair has since represented -- in the most dramatic fashion -- the tension between scientific and religious authority.

17th century: Even as Isaac Newton ascends to become an icon of the scientific revolution, he devotes 1 million words and countless hours of his intellect to the practice of alchemy. The ability of the human mind to simultaneously entertain contrary belief systems is a perennial source of wonder.

c1900: Shortly after Röntgen discovered x-rays, the French physicist, René Blondlot, claimed discovery of what he called "N-rays." Other scientists confirmed his observations. Papers were published. Trouble was, N-rays didn't exist. This episode has become a classic case of "pathological science" in which self-deception, wishful thinking, and selective use and negligence of data can lead scientists astray.

1926: Alfred Wegener's theory of continental drift submerges due to the lack of support from his peers (to say the least). Forty years later, moving continents were established as scientific fact. The critical attitude always has been central to the scientific process, but it also can lead to the premature rejection of good ideas. This episode also is testimony to the faith among scientists that the truth will come out.

World War II: Often known as "the physicists' war," WWII demonstrated tight links between science, technology, and national security. Synthetic rubber, radar, proximity fuses, and the fission bomb all emerged from the most extensive government-supported R&D program in history. After the war, this new R&D infrastructure evolved into its present form.

1953: Without Rosalind Franklin's crystallographic data of DNA, James Watson and Francis Crick wouldn't have determined that molecule's structure when they did. The two of them and Franklin's senior co-worker, Maurice Wilkins, shared a Nobel Prize for the discovery. Franklin never received official credit for her contribution, and her role was written out of early historical accounts. Franklin represents the struggle for professional parity that women have waged, and continue to wage, in the scientific community.

The 20th century--The Janus Face of Science

Science has never been a value-free enterprise, and its double-edgedness expressed itself with a sobering regularity this century. Before there was "better living through chemistry," there were clouds of death-dealing chlorine on the Western Front of World War I. The next World War and the Cold War ushered in the awesome power of nuclear fission and fusion and a new kind of apocalyptic angst. Then came Rachel Carson. She alerted the world to global-scale ecological threats that can come with wide-scale environmental releases of synthetic chemicals. Her point was reiterated in the 1970s and 1980s when industrial activity and products were linked to planet-altering threats like ozone holes and global warming. Now, the growing ability to understand and manipulate our own genetic foundations opens up almost utopian medical possibilities. But that gleamy-eyed future only comes with the threat of unnerving compromises ranging from genetics-based job discrimination to the possibility of literally bumbling with the genetic constitutions of all generations that follow this one. Science has entangled itself within the most important values there are, and that brings with it unprecedented responsibilities for scientists of the next millennium.

Acknowledgments: Guidance for this graphic came from many books and other documents, as well as from the following historians: Robert Friedel, Naomi Oreskes, Steven Dick, Garland Allen, Spencer Weart, Sara Schechner, and James Fleming. The editors reserve credit for any remaining errors of fact or interpretation.

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The Pathways Timeline
Jay M. Pasachoff, Astronomer , Field Memorial Professor of Astronomy; Chair, Astronomy Department; Director, Hopkins Observatory,
SCIENCE Online, 26 Jan 2000 [Response]
The Pathways Timeline
Seymour S. Cohen, American Cancer Society Research professor, emeritus
SCIENCE Online, 26 Jan 2000 [Response]
Cuvier and fossil human ancestors
Carol I. Mason, Adjunct Professor of Anthropology , Lawrence University
SCIENCE Online, 2 Feb 2000 [Response]
Stumbling along the Pathway
Michael L. Perdue, Ph.D., Microbiologist, , USDA, Athens, GA
SCIENCE Online, 2 Feb 2000 [Response]
Plate tectonics - wrong people, wrong time
Naomi Oreskes, Associate Professor, History Department , University of California, San Diego
SCIENCE Online, 2 Feb 2000 [Response]
Sins of omission
E.T. McMullen , Department of History, Georgia Southern University, Statesboro, GA
SCIENCE Online, 2 Feb 2000 [Response]
Pathways timeline
Humphrey Sassoon , 1561 St. Luke Road, Woodstock, VA 22664
SCIENCE Online, 10 Feb 2000 [Response]
Pathways timeline
Ivan Tolstoy , Knockvennie, Castle Douglas DG7 3PA, Scotland
SCIENCE Online, 10 Feb 2000 [Response]
A Bit of Humility
Daniel Jungkuntz, Reverend , Peninsula Pastoral Counseling Center, Newport News, VA 23606
SCIENCE Online, 10 Feb 2000 [Response]
Missing Michael Faraday
Ajoy Baksi , Department of Geology and Geophysics, Lousiana State University, Baton Rouge, LA 70803
SCIENCE Online, 17 Feb 2000 [Response]
"Science" and Mathematics
Michael D. Graham, Associate Professor of Chemical Engineering , University of Wisconsin, Madison, WI 53706-1691
SCIENCE Online, 17 Mar 2000 [Response]

Related articles in Science:

Deconstructing the "Science Wars" by Reconstructing an Old Mold .
Stephen Jay Gould
Science 2000 287: 253-261. (in Pathways of Discovery) [Summary] [Full Text]

Timeline Travails.
Don Ihde; and Ivan Amato
Science 2000 287: 803. (in Letters) [Full Text]

We Aren't Worth a Mention?.
Robert W. Kates
Science 2000 287: 973. (in Letters) [Full Text]

Limits to Our Knowledge.
Walter Makous
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Volume 287, Number 5451 Issue of 14 Jan 2000, p 229
©2000 by The American Association for the Advancement of Science.

Copyright © 2000 by the American Association for the Advancement of Science.