Alan Huffman

Historically, war journalists have embedded themselves with one side, which means the greatest threat comes from the clearly delineated enemy of that side.

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.

Like so much in Singapore, admission to the Marina Bay's casino is hierarchical: Free for anyone with an international passport, costly for locals, off-limits to migrant workers altogether.

Aside from its parks and nature areas, Singapore is intensively developed, and due to the shortage of land, is building up, down and on manmade islands and landfills.

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.

Life feels more vivid in a conflict zone. It is clear what matters, and who you can count on, for what.

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.

Right up until the late 18th century, when the first weighted lines were used to probe the ocean depths, many people believed the seas were bottomless - the watery equivalent of infinite outer space.

Historically, maritime travelers had to pass around the entire mass of North and South America, including the bottom tip, the tempestuous Cape Horn, which was littered with shipwrecks.

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.

Without an adequate response, an epidemic can develop into a pandemic, which generally means it has spread to more than one continent.

Without effective human intervention, epidemics and pandemics typically end only when the virus or bacteria has infected every available host and all have either died or become immune to the disease.

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.

Anyone who was alive during the outbreak of the bubonic plague in the 14th century experienced something terrifyingly close to the widespread death and chaos of an apocalyptic event.

Long-distance train conversations are unlike the perfunctory exchanges one normally associates with strangers, or the truncated, cut-to-the-chase kind that sometimes take place between seatmates on a plane.

My own experience with trains dates to long-ago childhood trips with my family in Mississippi to see my grandmother off at the station in Jackson, bound for Memphis.

Based on German prototypes, green walls and roofs are a natural idea in Singapore's tropical environment, where mosses, ferns, philodendrons, orchids and other epiphytes literally grow on trees.

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.

The slow pace of trains in the U.S. can be maddening, particularly during delays on rail sidings for an hour or more to enable freight trains - which have the right-of-way - to pass.

The Singaporean government, which represents legal migrant workers in employment disputes and claims of exploitation, requires that they stay in the country until the disputes are settled. If they leave, their claims are closed.