The advances in photography during the past century have been a boon to inquisitive mankind. If astronomers were still dependent on the human eye for their knowledge of the universe, relatively slim would that knowledge be, even though telescopic lenses and mirrors were doing their frantic best to reach distant galaxies and unravel cosmic chemistry.

Indeed, without photography the elegant pictures of the universe in this book would not have been possible. We wonder wistfully if there may not be some yet unknown tool that could break through our barriers of ignorance as sensationally as the photographic processes did a century ago. Can it be that radio telescopes and photoelectron tubes are such implements?

There are so many unknowns and still more unknowables-unknowable to our present-day mental and sense-organ equipment. Where should we look for a breakthrough in the psychology of ani-mals, in the realm of completely new mathe-matics, in subelectronics? A wonderful prospect lies ahead for those who tackle the universe.

Some photographs record a million of the stars of our galaxy. Others, groping for the bounds of the uni-verse, uncover thousands of other galaxies. Ten times as many galaxies inhabit our ex-plorable space-time as there are men on this crowded planet. There are indeed galaxies enough for everybody!