Whether it's constructing soaring towers or scaling colossal mountains, lofty pursuits are rarely rational. Yet this obsessive striving to reach the sky represents a unique aspect of the human spirit. From the world's tallest building to a continent's highest mountain to a flight to the edge of space, sky-high destinations just keep on getting higher. In the 21st century, one thing is certain: the only way is up. rcarroll@thenational.ae