The Day We Found the Universe

"This book covers a lot of ground. It’s about early 20th-century astronomy, mostly in America, and Edwin Hubble and how he discovered the expanding universe. She also traces everything leading up to that discovery. There was a big debate in the 1920s about whether galaxies were just nebulae, and part of our own galaxy, or if they were actually completely separate, which is what they turned out to be. She describes this in her book, and I also mention it mine. There was a ‘Great Debate,’ as they called it, between Harlow Shapley and Heber Curtis about this issue. It was like a softer, less hostile version of the debate that I describe in my book . “I’m very drawn to books with strong narratives and strong characters” The thing that I like about this book is that she really humanizes all the scientists, and the research too. By doing that, she provides a fascinating insight into how the scientific process works. She shows how pioneering it all was at the time, because they just had basic tools. They had telescopes and spectrographs, but nowhere near what we have now. The fact that they were able to gather so much information and come to all these conclusions is a fascinating story. I love her writing, too. There’s a very humanistic quality to it, I would say. There’s a humor to it. It’s not dry at all. You always get the feeling she’s talking about real people who have real problems like the rest of us and yet they persevered and accomplished these amazing things. When you read a book sometimes, you think, ‘Wow, this is so good. I wish I’d written it.’ I had that feeling with this book. I knew I couldn’t write something as good, but at least I could try. The stories are different in a lot of ways, but it was an inspiration for Splinters of Infinity . A bit of both. Originally, I had the idea of doing a book on cosmic rays in general, and the history of cosmic ray research, which is a big subject. It’s been going on for over a century and is still ongoing. But I realized that was going to be a huge project that was going to take a long time. Then the pandemic hit, and everything closed down. I thought, ‘Well, if I’m going to do this, I need to scale it down somewhat.’ And the conflict between Robert Millikan (1868–1953) and Arthur Compton (1892–1962) turned out to be the perfect way into the subject. Just the idea of cosmic rays had a sort of romance and wonder to it. These mysterious things coming from outer space. A century ago, people were wondering, ‘What are these things?’ In many ways, it’s like the way we think about dark matter or dark energy now. We know there’s something there. We don’t quite understand it, but we know that it’s very important. That’s what cosmic rays were 100 years ago. A cosmic ray is basically a high energy particle coming from space. The term cosmic ray is really a misnomer because it implies it’s like a ray of light. This was the core of the argument between Millikan and Compton. Are they rays like photons or light, just energy waves? Or are they actually subatomic particles? They turned out to be particles, which—not to give any spoilers—was Compton’s argument. But when they were first discovered and publicized ‘cosmic ray’ was the term that somebody came up with. It’s been credited to Robert Millikan but other people say, ‘No, Millikan didn’t come up with that word, he was just the first one to really use it widely.’ Whoever coined it, it’s stuck all this time. They’re particles that are always coming in from all different directions and are passing through your body right now. They’re very high energy, but most of the time they don’t do anything. Once in a while they’ll flip a byte inside a chip in your computer, causing glitches. But that’s rare. We still don’t know exactly where they all come from. Which is another thing that drew me to this subject because after all this time, it’s still a mystery. At that time (not so much now), they were really thought to be the key to everything: ‘If we can figure this out, we will know the origins of the universe and its ultimate fate!’ There’s something to that, but it’s a lot more complicated, as we now know. I debated whether to start with that. I wanted something to get my readers into this and also to show the importance of the international nature of science, and how that can be deeply affected by other things going on, like the politics. I also thought that line that Pauli wrote in his letter—’Oh, my God, I had to shake hands with this guy’—was kind of funny. It was a big factor. World War One disrupted a lot of the relationships between scientists. The ideal is that science is a universal thing and doesn’t pay attention to national boundaries. Of course, it doesn’t work that way. From right after the war through the 1920s the Germans were kind of ostracized. Some of them had done war research, but it affected even those physicists who had nothing to do with it. The US also started to have scientists like Millikan and Compton, who were prominent, did important work, and won Nobel prizes . But Europe was still very important, because of quantum physics. You had Einstein , Niels Bohr and all those folks. I think it was in the 1930s that things really began to shift to the United States. We had the Great Depression , but we were still relatively unscathed from the war. We didn’t have Hitler or Mussolini. This is one of the reasons I liked The Physicists, which goes into a lot of detail on this."