Knocking on Heaven's Door - Lisa Randall [166]
Size nevertheless plays a critical role in characterizing our observations—both of the current universe and its history over time, and this chapter explores both. In the second half, we’ll consider the evolution of the universe as a whole, from its tiny initial size to the vast structure we now observe. But first we’ll look out at the universe as it appears today in order to familiarize ourselves with some of the lengths that characterize what surrounds us. We’ll work our way up in scales to consider larger sizes and more distant objects—on Earth and in the cosmos—to get a feeling for the bigger types of structures that are out there to explore. This tour of large scales will be briefer than our earlier tour of matter’s interior. Despite the richness of structure in the universe, most of what we see can be explained with known physical laws—not fundamental, new ones. Star and galaxy formation rely on known laws of chemistry and electromagnetism—science rooted in the small scales we have already discussed. Gravity, however, now plays a critical role as well, and the best description will depend on the speed and density of the objects it is acting on, leading to varying theoretical descriptions in this case too.
TOUR OF THE UNIVERSE
The book and film Powers of Ten,67 one of the iconic tours of distance scales, starts and ends with a couple sitting in Grant Park in Chicago—as good a place to begin our journey as any. Let’s momentarily pause on (what we now know to be largely empty) solid ground to view the familiar lengths and sizes around us. After momentarily reflecting on their human scale of about a couple of meters’ height, let’s take leave of this comfortable resting place and ascend to greater heights and sizes. (Refer to Figure 70 for a sampling of the scales this chapter explores.)
[ FIGURE 70 ] A tour of large scales, and the length units that are used to describe them.
One of the more spectacular demonstrations of human response to height that I’ve seen occurred during a performance of Elizabeth Streb’s dance company. Her dancers (or “action engineers”) fall onto their stomachs from a rail raised higher and higher until the final dancer falls a full 30 feet. That is definitely beyond our comfort zone as the many gasps in the audience make abundantly clear. People shouldn’t fall from that height—certainly not onto their faces.
Though maybe not so dramatic, most tall buildings inspire strong reactions too, ranging from awe to alienation. One of the challenges architects face is to humanize structures that are so much bigger than we are. Buildings and structures vary in size and shape, but our response to them inevitably reflects our psychological and physiological attitudes toward size.
The world’s tallest man-made structure is Burj Khalifa in Dubai, United Arab Emirates, which stands 828 meters (2,717 ft.) tall. That is dauntingly high, but it’s largely empty and the movie Mission Impossible 4 probably won’t confer on it the same cultural status that King Kong gave to the Empire State Building. New York’s iconic 381-meter building stands at less than half the height of Burj Khalifa. However, to its credit, it has a much higher occupancy rate.
We live in a world surrounded by much larger natural entities, many of which inspire awe. In the vertical direction, Mt. Everest, at 8.8 kilometers, is the highest peak on Earth. Mt. Blanc, the tallest mountain in Europe (at least if you’re not from the country of Georgia), is only about half as high—but I was still pretty happy years ago when I made it to the summit—though my friend and I look pretty miserable in the photo we took at the top. At 11 kilometers deep, the Mariana Trench is the deepest known place in the ocean, and the lowest elevation of the Earth’s surface crust. This otherworldly trench was the director James Cameron’s destination once he had successfully conquered three-dimensional imagery with his successful movie Avatar.
Natural bodies spread on the Earth’s surface over far more extended regions. The Pacific Ocean, for example, is about