Most of the planet's terrestrial surfaces are visually accessible through video cameras and satellite imagery, if not physically within reach. Even the approaches to Mount Everest are now littered with human debris. One can drive to Timbuktu, which for centuries was synonymous with inaccessibility.
In our quest to define and describe the world, we have crisscrossed the oceans and continents, compiling exhaustive knowledge about its life forms and features, and extended our physical reach through technology, which provides us instantaneous and pervasive access to information about seemingly everything.
When President Teddy Roosevelt posed for the cameras astride a massive steam shovel during construction of the Panama Canal in 1906, it was more than a simple photo op. Though the scene was clearly staged, it symbolized a crucial moment in American history.
Left to their own devices, epidemic diseases tend to follow the same basic process: A virus or bacteria infects a host, who typically becomes sick and in many cases dies. Along the way, the host infects others.
Poor laborers from all parts of Asia as well as Africa, the Americas and even Europe are transported by plane each day to wealthier nations where low-tier jobs are plentiful; sometimes the travelers board without even knowing their final destination.
Conflict photographers grapple with two worlds that are themselves often in conflict - the one where bombs fall and bullets fly, where adrenaline runs high, and the other, back home, which is comparatively secure, and where the big event of the day may involve selecting swatches of fabric for a new sofa.