My daughter gave me this book for Christmas and once again knocked it out of the ballpark. Based upon the books she has gifted me over the past few years I am pretty convinced that she knows my likes and tastes much better than I know myself.

My background includes a degree in physics, and spending some time as an astronomy teacher at Humboldt State University in Northern California. Being on the foggy, rainy coast of Northern California might not have been the best place to teach astronomy, or introduce students to our little observatory on Humboldt Hill, but it was a great place for me to play with such fascinating subjects. I didn’t follow my education to a PhD in physics, so my understanding of the more complex and mind boggling aspects of the field is best described as an informed/interested amateur. This book is written at exactly the correct level for someone such as myself (even if they don’t have a strong mathematics background). This is a great book for anyone interested in physics, generally keeping up with the “popular” accounts of advancements in physics, but not steeped in the extremely difficult mathematics that serves as the language of the field.

For me, Dr. Mack hit just the right blend of casual, lighthearted, and funny, while making extremely complex (and weird) cosmological considerations approachable by shining light on the subject without dumbing it down so much that the juicy parts are missed. I found myself balanced between wanting to race ahead in the book because it was so much fun, and slowing down to avoid missing nuggets of insight. I suppose I will have to go back and read it again because I just had too much fun reading it.

I have a desire to thank Dr. Mack for finally clearing up a confusion that I have been chewing on for almost 60 years – how can we just be seeing light after is has traveled for about 13 billion years from a point (singularity) where everything started out at the same place? It turns out to be easy; space expands faster than the speed of light! Things within space don’t go faster than the speed of light, but space itself expands faster than light once you get far enough away from the observer (and this applies to every point in space, not just us). This means that light that is far enough away can get here because space through which it travels is expanding faster than light can travel. However, since the expansion of space has slowed over the last few billion years to a leisurely pace that is less than the speed of light, that old light that was unable to come into our field of view has finally “caught up” and is now visible. It is coming through the edge of visibility (the event horizon) from the back side. (I told you things get kind of weird.) The thing that makes space grow like this is “Dark Energy” – and it accounts to something like 80% of the total energy/mass of the universe. It is also totally mysterious – a “pressure” causing space to expand. Sometimes it is called The Cosmological Constant (perhaps the same one that Einstein included in his equations and then spent the rest of his life trying to get rid of).

I have now replaced my question of how could light just be getting here from the beginning of the universe with another question, “What makes the universe expand?” So far nobody knows the answer to that question – but oddly enough I have been working on a project that is intended to get answers to that very question, the Vera C. Rubin Observatory and its amazing LSST telescope. It turns out that this project may well be one of the most important physics “tools” ever! I am blessed to have accidentally fallen into such an interesting project, after I had thought I was retired. So much for retirement!