Kimberly Arcand - Magnitude: The Scale of the Universe

We were thrilled to be able to work on our Magnitude book with editor Becky Koh and the rest of the team at Black Dog & Leventhal Publishers, following the wonderful experience with our previous book together, Light. We are also thankful for both our current agent, Laura Biagi of the Jean V. Naggar Literary Agency, and Elizabeth Evans, who has moved on to other pursuits.

With a project like this, it is incredibly helpful to have additional knowledgeable people to review the material along the way. We are deeply grateful for the role that Adrienne Gauthier played, checking and double-checking the research we conducted and making sure the facts and figures in this book were as accurate as possible. We are also indebted to our longtime friends and coworkers Wallace Tucker and Peter Edmonds from the Chandra X-ray Center, who used their scientific expertise as well as their intuition for whats interesting to help guide us. We could not ask for better colleagues.

On a personal note, Megan would once again like to thank Kristin, Anders, Jorja, Iver, and Stella for being patient, supportive, and lovingno matter how many times they hear the same refrain about needing to get work done on the book. She would also like to add a nod to Rainy and Jody, two Great Danes who were excellent canine coworkers during the writing of this book.

Kim must again thank her family for their patience throughout the process of the books creation and dissemination. Much love and gratitude belongs to her husband, John, and her children, Jackson and Clara. The sheer scale of their love and support goes beyond the magnitude of this book (pun intended). She also dearly thanks her amazing mom, her dad, and the rest of her family and friends, and yes, even her dog too, for being such amazing cheerleaders.

Finally, a huge thank-you to our readers. Your support and continued interest keeps us motivated to write more, write better, and cover new areas. We hope you find this book appealingon a grand scale.

We want to take you on a journey

to explore some of the lightest and heaviest, fastest and slowest, hottest and coldest, largest and smallest, loudest and quietest phenomena in the Universe.

It can be difficult for us to conceptualize the magnitude of such phenomena at both the largest and smallest ends of the spectrum, because these sizes, speeds, masses, and quantities are so far outside the realm of our own experience. The notion of the tiniest particle within the structure of an atom or the vastness of a black hole at the center of a galaxy is impossible for us to truly fathom. But, while the concept of magnitude can be challenging, its not insurmountable. Understanding magnitude in the extreme just requires the right tools: not hammers and screwdrivers, but rather the intellectual tools that allow us to explore these concepts in a clear way. Thats where the language of science comes in.

In a world such as ours, it would be impossible to cover every example or aspect of magnitude. Also, we couldnt possibly include or define every type of unit that magnitude is measured in, but, thankfully, the Internet is full of helpful conversion calculators if you take a look. We hope, however, that you enjoy our selection of what we think are some of the most interesting ways to picture the scale of our Universe.

In everyday language, orders of magnitude connotes the idea of the expansion of size in some significant way. In science, there is a more precise definition.

Scientifically speaking, an order of magnitude of a number usually refers to the approximate value of that number, measured in powers of tenin other words, where that number sits on a scale that measures ones, tens, hundreds, etc. So 10 and 20 are the same order of magnitude, but 100 is one order of magnitude larger. Between 10 and 1,000, there are two orders of magnitude, and so on.

Lets think of this another way. If you recall a number line from school, it looks something like this:

Each step you take on this number line involves the change of one (move to the right to add one to your value, or subtract one if you move to the left).

With orders of magnitude, the math is a bit different. Instead of adding (or subtracting) a set amount for every step you take on the number line, you multiply (or divide) by a prescribed amount. It looks something like this:

This is powerful. On the first number line, we went up by a value of 5 in 5 steps. Simple enough. But in the second number line, we moved up by a value of 100,000 in the same number of steps. We need this turbocharged way of changing values in order to depict the awesome range of magnitudes, both large and small, that well be exploring in our known Universe.