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.

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.

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.

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.