Who best to tell the story of radio astronomy than a pioneering figure like Sir Francis Graham-Smith? In Unseen Cosmos: The Universe in Radio, Graham-Smith covers nearly a century of radio, starting with Karl Jansky’s investigation of background noise for Bell Telephone Laboratories in 1932. Jansky’s rotating directional antenna pointed to the center of the Milky Way as the source of the noise and these were the first radio waves observed from space.
But Jansky didn’t ignite an immediate revolution; his publications in journals went almost unnoticed by astronomers. “When I started research in 1946,” says Graham-Smith, “it was not at all obvious that radio would have any substantial contribution to make to our understanding of the Universe on any scale, except perhaps there might be something to be learnt about the Sun from its outbursts of radio emissions associated with sunspots and flares.”
Unseen Cosmos: The Universe in Radio by Francis Graham-Smith
Oxford University Press, 2013
246 pages (Kindle)
Source: Personal Library
“There was no conception that radio could contribute to cosmology,” he continues, “although…it now provides the most fundamental observations of the early Universe and its evolution.”
Over 30 years after Jansky, while using another antenna built by Bell Labs, Arno Penzias and Robert Wilson went on to discover the Cosmic Microwave Background (CMB), the oldest light in the universe. The significance of what Jansky had stumbled upon was now understood to be a window into the microwaves (the afterglow) predicted to exist as the result of the Big Bang. Since those days, radio astronomy has revealed a universe invisible to optical telescopes and entirely unknown to our ancestors.
“Radio draws the attention of astronomers to objects which would be impossible or very difficult to discover by optical means,” writes Graham-Smith, “objects such as pulsars and quasars, which are the seat of some of the most energetic processes in the Universe. And…because the low frequencies of radio waves lend themselves to sophisticated processes which are not available to the high frequencies inherent in light…”
The electromagentic spectrum—which also includes infra-red, visible light, ultraviolet, X-rays, and gamma-rays—holds a host of information about the beginnings of the universe. What is truly amazing is that out of the entirety of human history, we are only now, with the advent of radio astronomy, getting a glimpse into this past approximately 14 billion years in the making.
All-sky map of the CMB, created from 9 years of WMAP data: Image Source: Wikicommons
A short while back, as I was searching for a few good books covering the history of radio astronomy for a current writing project, Unseen Cosmos caught my attention. It is a clearly-written, college level text, and a pleasure to read. Graham-Smith engages the significance of research from COBE and WMAP, but ends the book looking to the future of astronomy, including the next generation of research coming from LOFAR, ALMA, and SKA.
When one visits a Dark Sky Park and stares at the Milky Way or Andromeda, it might be hard to remember that the universe is engulfed in light beyond that which our eyes evolved to see. But there are those who spend their days exploring that incredible invisible world, and if you’re interested in knowing more about it, then Unseen Cosmos is a good place to start.