Review: What Is Relativity? by Jeffrey Bennett

What Is Relativity?It’s not you, book, it’s me. (I should start out by saying that I’ve had a very long history of not liking physics, which is kind of ironic since I have an engineering background.) But really, if I were a normal non-physics-hating person, I would’ve really liked What Is Relativity? for Bennett’s ability to explain abstract concepts in a fun and simple way. I loved the first half of this book, but by the end, the physics concepts and the repetitiveness of the thought experiments overpowered Bennett’s humorous narrative, and I was unable to enjoy the book in its entirety. I would still recommend it though, especially for people who are curious about the concepts of relativity and don’t know where to start.


You’ve probably heard of terms like “relativity”, “black holes”, and “light years” at some point in your life, but do you really know what they mean? Bennett, a science educator with a Ph.D. in Astrophysics, takes you on a trip to the nearest black hole while providing a plethora of thought experiments to explain Einstein’s special and general theories of relativity, as well as the implications of relativity.


A book that starts out by guiding you through the process of building a spacecraft to visit a black hole is a book done right. (If you’ve played Spore, you’d be super excited for this part of the book!) Bennett’s thought experiments are entertaining and engaging, and really made physics fun and understandable. These thought experiments involve colleagues falling into black holes, racing against light (and losing by just a little!), Star Trek and Star Wars references, and many other memorable situations. Bennett’s narrative is full of dry humor, and if I had a high school physics teacher like him, I think I would’ve enjoyed physics more. Right before aiming directly at a black hole by accident, he says this:

After traveling 250 trillion kilometers from Earth, you’d have to be the unluckiest person in history to be aimed directly at the black hole by accident.

However, the thought experiments did get repetitive and tiring after a while. Maybe the physics just got a bit too much for me, or maybe I got space-sick, but reading about Jeff (Bennett) and Al (Einstein) being up in space for a long time ended up making me dizzy and nauseous.

On a different note, the diagrams included in What Is Relativity? are very cute and informative. Bennett should start writing textbooks (oh wait, he has!) because, really, these figures and his explanations made me understand gravitational redshift and the equivalence principle, which is no mean feat. I can’t say that I still remember what they mean, but hey, I did in the moment. Other interesting facts I do remember from this book are that black holes don’t suck, time runs slower in stronger gravity, and Einstein started his career by imagining himself riding on a beam of light.

Another aspect of the book that I really enjoyed are the analogies. Take Bennett’s raisin cake analogy for the expansion of the universe, for example:

If you lived in a raisin inside an expanding raisin cake, you would observe all other raisins to be moving away from you, with more distant raisins moving faster. In the same way, the fact that we observe more distant galaxies to be moving away from us at higher speeds implies that we live in an expanding universe.

So there’s definitely a lot of good stuff in this book. Unfortunately, I could only love half of the book before my physics-hating tendencies kicked in. There are concepts that I still couldn’t understand after reading through a thought experiment multiple times, and there are parts I skimmed through.


This is a book I really, really wish I could’ve liked more. I think What Is Relativity? would be a great book for people who have had no physics background (or aren’t completely ruined for physics because they had a bad high school physics teacher) or for people who want to learn more about relativity in an interesting way. Bennett’s humorous narrative, entertaining examples, and clear figures make physics seem fun and interesting, and this is a great example of effective science communication.


6 thoughts on “Review: What Is Relativity? by Jeffrey Bennett

  1. Whoooooa I never thought someone would even come close to persuading me to read a sciencey book, but you did a good job! Still didn’t quite push me over the edge, but close! Very close! 😀

    • LOL, if this is what happens when I review a book I kind of sort of didn’t like, wait till I review a sciencey book that I love! (The book-pushing will come!)

  2. It’s too bad you ran out of steam for enjoying this by the end, but I think it’s great you were able to highlight the positive things about it anyway. I don’t think I liked it enough to ever read it again, but I also thought it was very well done and would have been a huge improvement over my high school physics class too 🙂

    • Thanks, Katie! I’m trying to keep my New Year’s resolution of finding positive things about all the books I read (unless I really hated them). 😛 But yes, high school physics could’ve been so much fun with a book like this! Same with all the other subjects… I feel like school was only fun in primary school when they actually tried to make learning fun, and over the years students are just expected to memorize or gain a love for the material themselves.

  3. Although you did not enjoy this book, I’m real glad you discussed the good parts 🙂 Although I love physics and chemistry, I find it very tedious to read all those thick textbooks (I’d rather solve those word problems). I wish these books existed before so I can humor myself and try to learn in the process. You know what, I’m going to give this book a try 🙂

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