Doubling Time

Half of all research papers ever published in astrophysics have appeared in the past fifteen years.

Of all the sdences cultivated by mankind, astronomy is acknowledged to be, and undoubtedly is, the most sublime, the most interesting, and the most useful. For, by knowledge derived from this science, not only the bulk oft he Earth is discovered ... but our very faculties are enlarged with the grandeur of the ideas it conveys, our minds exalted above the low contracted prejudices of the vulgar.

Astronomy Explained Upon Sir Isaac Newton's Principles

--James Ferguson, 1757

I couldn't agree more.

James Ferguson was rejoicing in the insights to the universe that one could derive from the Principia, Sir Isaac Newton's seminal work published seventy years earlier. This masterpiece established a foundation for both physics and mathematics that made possible the birth of the Industrial Revolution and the modern era of cosmic discovery.

By any measure, we are living in the golden age of astronomy. The rate at which research papers are being published is the highest ever. The number of astrophysicists in the world is 50 percent greater than just a decade ago. And the power of the world's telescopes--now gathering all wavelengths of light--has allowed astronomers to see more objects at greater distances than ever before. Not a week goes by that a newspaper headline doesn't reveal a newly discovered fact or feature of the universe--and no greater nightmare disturbs the sleep of a textbook author. Decades ago, new editions of astronomy textbooks came out more often than necessary, just to short-circuit the lucrative market for used books. Now the release of new editions could be justified almost monthly, simply to keep pace with discoveries in the field.

But let's stop and think for a moment. How often do experts ever write "We hardly know anything about anything" or "Gee, I wish we weren't living in such backward times"? It seems whenever we humans talk about our knowledge of the natural world, we wax poetic about how far we've come and how much we know. Apart from Thomas Edison's famous party-pooping remark "We don't know one millionth of one percent about anything," praise for the depth and breadth of contemporary knowledge is the rule rather than the exception. The preface to Chris Impey and William K. Hartman's Universe Revealed, a college textbook published last year, agrees:

   Astronomy is the oldest science, but it is also tremendously active right
   now. Discoveries are being made by large new telescopes on high
   mountaintops and by sophisticated new observatories in space.

The preface to The System of the Stars, a treatise on the known universe written 110 years ago by the prolific astronomy popularizer Agnes M. Clerke, makes the same case. She was sure that she was living in the golden age of discovery:

   Now, in the history of the human intellect, there is no more astonishing
   chapter than that concerned with the sidereal researches of the last
   quarter of a century.

Thirty-five years earlier, in 1855, Elias Loomis mused with similar emotion in the preface to his highly acclaimed Introduction to Practical Astronomy:

   The rapid advance in the cultivation of Practical Astronomy which has
   recently been made in the United States is one of the most encouraging
   features of the age.

One could analyze, decade by decade, the political, social, economic, and cultural forces that promoted cosmic discovery, but astronomy was not uniquely favored. It was simply one of many fields enjoying an explosive growth of knowledge, as noted by the editor David A. Wells in his preface to the 1852 Annual of Scientific Discovery:

   The progress of invention and discovery, of improvement and application, is
   so rapid, unceasing and continuous, that it would require a volume many
   times the size of the present to record, even in a summary manner, all that
   transpires of scientific interest in the course of a single year.

Wells was convinced he knew why:

   One fact must be apparent to all, that is, that the number of persons now
   engaged in contributing to the advance of every department of natural and
   physical science is greater than at any former period. The evidence of this
   is to be found in the ... greatly increased publication and circulation of
   scientific books and journals.

When a field of research grows exponentially in a generation, that generation perceives itself as living in a special time. A quantitative analysis reveals this as well. Recently, while browsing the stacks of Princeton University's astrophysics library, I paused by the wall of shelves containing the Astrophysical Journal, which has been around since the birth of modern astrophysics and is the leading research journal in the field. Since all the issues were on display, from the first volume in 1895 to the most recent publication, the halfway point in this record of research (at the middle of the wall) was easy to find. Taking into account the changing length and width of the Journal's average page over the years, the halfway point fell among the journals dated fifteen years ago.