The following is excerpted with permission from The Knowledge: How to Rebuild Our World from Scratch, by Lewis Dartnell. Available from Penguin Press, a member of Penguin Group (USA), LLC, a Penguin Random House Co. Copyright © Lewis Dartnell, 2014.
Photography is a wonderful technique—a way of harnessing light to record an image, capturing an instant in time and preserving it for eternity. A holiday picture can trigger vivid reminiscences even decades later, but a photograph records the visual world with far greater fidelity than memory can ever offer. Yet beyond drunken party snapshots, family portraits, or breathtaking landscapes, the incomparable value of photography over the past two hundred years has been in presenting what the eye cannot see. It represents a key enabling technology across numerous fields of science, and will be vital in accelerating the reboot of society after a disaster. Photography allows investigators to record events and processes that are exceedingly faint or occur over timescales too rapid or too slow for us to perceive, or at wavelengths invisible to us. For example, photography offers extended exposure times to soak up feeble light over far longer periods than the human eye can offer, allowing astronomers to study a multitude of dim stars and resolve faint smudges into detailed galaxies and nebulae. Photographic emulsions are also sensitive to X-rays and so allow you to create medical images for examination of the body’s interior.

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