Knocking on Heaven's Door - Lisa Randall [11]
Even with the delay, I realized if I was going to talk to Mark at any length, I had to know where he stood on his film—which I was familiar with from the numerous people at my lectures who asked me off-the-wall questions based on what they had seen in it. Mark’s answer caught me by surprise. He had made a rather striking about-face. He confided that he had initially approached science with preconceived notions that he didn’t sufficiently question, but that he now viewed his previous thinking as more religious in nature. Mark ultimately concluded that what he had presented in his film was not science. Placing quantum mechanical phenomena at a human level was perhaps superficially satisfying to many of his film’s viewers, but that didn’t make it right.
Even if new theories require radically different assumptions—as was certainly the case with quantum mechanics—valid scientific arguments and experiments ultimately determined that they were true. It wasn’t magic. The scientific method, along with data and searches for economy and consistency, had told scientists how to extend their knowledge beyond what is intuitive at immediately accessible scales to very different ideas that apply to phenomena that are not.
The next section tells more about how the notion of scale systematically bridges different theoretical concepts and allows us to incorporate them into a coherent whole.
EFFECTIVE THEORIES
Our size happens to fall pretty much randomly close to the middle in terms of powers of ten when placed on a scale between the smallest imaginable length and the enormity of the universe.6 We are very big compared to the internal structure of matter and its minuscule components, while we are extremely tiny compared to stars, galaxies, and the universe’s expanse. The sizes that we most readily comprehend are simply the ones that are most accessible to us—through our five senses and through the most rudimentary measuring tools. We understand more distant scales through observations combined with logical deductions. The range of sizes might seem to involve increasingly abstract and hard-to-keep-track-of quantities as we move further from directly visible and accessible scales. But technology combined with theory allows us to establish the nature of matter over a vast stretch of lengths.
Known scientific theories apply over this huge range—spanning distances as small as the tiny objects explored by the Large Hadron Collider (LHC) up to the enormous length scales of galaxies and the cosmos. And for each possible size of objects or distance between them, different aspects of the laws of physics can become relevant. Physicists have to cope with the abundance of information that applies over this enormous span. Although the most basic laws of physics that apply to tiny lengths are ultimately responsible for those that are relevant to larger scales, they are not necessarily the most efficient means of making a calculation. When the extra substructure or underpinnings are irrelevant to a sufficiently precise answer, we want a more practical way to calculate and efficiently apply simpler rules.
One of the most important features of physics is that it tells us how to identify the range of scales relevant to any measurement or prediction—according to the precision we have at our disposal—and then calculate accordingly. The beauty of this way of looking at the world is that we can focus on the scales that are relevant to whatever we are interested in, identify the elements that operate at those scales, and discover and apply the rules