Why Do We Exist?: The Nine Realms of Universe that Make You Possible

by Hakeem Oluseyi, Nils Johnson-Shelton

A boundary-breaking astrophysicist reimagines the universe—and our place within it—in this audacious journey through the Nine Realms of the cosmos.

The universe gave rise to stars and cells, minds and memories, purpose and pain. But it doesn’t care about us. It follows its own rules. And now, according to Dr. Hakeem Oluseyi, we finally understand enough about those rules to ask the big questions like we mean Why do we exist? Are we alone? How did we get here? What comes next? And—perhaps most urgently—is there reason to hope?

Heck yeah, there is!

Dr. Oluseyi is no ordinary scientist. A former street kid turned world-renowned cosmologist, he realized something the story of existence can be told as a passage through nine interwoven realms—each revealing a new layer of cosmic truth.

There’s the Middle Realm, where we live; the Realm of Life, where organisms flourish across the vastness of space; the Cosmological Realm, where galaxies dance and collide; the Dark Realm, dominated by unseen energy and invisible forces; the Quantum Realm, where reality defies intuition; the Temporal Realm, where time begins, flows, and perhaps ends; the Multiverse Realm, where our universe may be one among many; the Realm Beyond Horizons, where observation breaks down; and the Realm of Imagination, where insight, curiosity, and creativity shape our understanding of it all.

In Why Do We Exist?, Dr. Oluseyi cracks open these realms with clarity, humor, and radical honesty, bridging cutting-edge physics, personal narrative, and philosophy. The result is a blueprint for understanding reality itself and a surprising case for human potential in an indifferent cosmos.

This isn’t just a science book. It’s a survival manual for the universally curious.

Genres: Science, Nonfiction, Audiobook, Physics, Philosophy, Astronomy

256 pages, Hardcover

Published April 21, 2026

Reviews

[Kalyan]

One of the finest audiobooks I have listened to in a long time and easily one of my favorites. The author Hakeem Oluseyi has a very good voice and the modulation is excellent throughout. Listening to it felt very close to listening to Morgan Freeman narrate a documentary. It just had that kind of warmth and authority to it.
The book covers the story of existence through nine interwoven realms of the universe and it does so in a way that is logical, systematic and genuinely interesting. Starting from the Middle Realm where we live all the way to the Realm of Imagination, each realm peels back a new layer of cosmic truth. The book bridges cutting edge physics, personal narrative and philosophy in a way that never feels overwhelming or dry. It has a lot of information packed into it and yet it never felt like a textbook. It felt more like a conversation with someone who really knows their stuff and genuinely wants you to understand it too.
I want to relisten to this book maybe 2 or 3 more times because there is just so much in it that I feel like I picked up a lot but there is still more to absorb. I would highly recommend this to anyone who is interested in astronomy, cosmology or science in general. Even if you are just curious about the big questions like why do we exist, are we alone, how did we get here, this book will give you a lot to think about.
I even felt like checking out the hard copy from my local library and reading it over cups of coffee. It is that kind of book. A documentary worthy read that leaves you inspired and curious. I really liked it.

[Marcus Lee]

I did not know who Dr. Oluseyi was before reading this great little book but after reading a little bit about him, I was delighted to learn that we are the same age, both graduated from Mississippi high schools in 1985, went to college 20 miles from each other and we both read comic books during those early 80s! Dr. O, I like to think we would have been friends if we had met in the late 80s. I majored in math and minored in physics at Millaps College while you were at Tougaloo. Our paths may have even crossed in Jackson at some point.

This book was a lot like Neil DeGrasse Tyson’s Astrophysics For People in a Hurry. A great companion volume. Loved the last chapter on the realm of imagination especially.

I’ve already downloaded Dr. O’s 2021 memoir to listen to soon.

[Crisis]

Impulse library grab. Delightful. Accessible overview of the history (and a bit of the future?) of physics. Optimistic. Almost zero footnotes.

[John Hall]

wonderful. unbelievable, amazing!

Simply mesmerising. What a story! The story of us. Of how we came to be. Could not put it down.

[Jim Gise]

Oluseyi zips through cosmology, particle physics, and cosmic evolution with infectious curiosity - blending equations, astrophysical insight, and philosophical riffs to nerd out about existence. Enchanting!

[Philemon -]

In 2015, John Horgan wrote a book called The End of Science, arguing that physics had created a valid map of how the universe works and that little may remain besides filling in and correcting details. Horgan impressively buttressed this somewhat depressing thesis by interviewing the likes of Lynn Margulis, Roger Penrose, Francis Crick, Richard Dawkins, Freeman Dyson, Murray Gell-Mann, Stephen Jay Gould, Stephen Hawking, Thomas Kuhn, Chris Langton, Karl Popper, Stephen Weinberg, and E.O. Wilson.

This absorbing new book by astrophysicist Hakeem Oluseyi will convince you otherwise. Ranging through particle physics, quantum physics, astrophysics, and cosmology, Oluseyi rakes up huge questions everywhere he looks. The result is largely chaotic and sense-resistant. The reader risks gulping down too much too fast. But it is all fascinating.

Oluseyi does extremely well in three areas: 1) How a universe might unroll after a Big Bang, with special focus on the first few millionths of a second. His exposition seems more freshly informed than Steven Weinbberg's The First Three Minutes (1993); 2) The life cycle of stars. His description is a thermodynamic tour-de-force.; and 3) How life needs to take billions of years to emerge. In all respects this book provides the biggest and most comprehensive (though, mercifully, not the most detailed) delineation I've encountered. There are no equations or overly abstruse technical language. On the other hand, this book is not for youngsters or newbies; it assumes a fairly high level of familiarity with the material, if not actual former study.

One star is deducted from the rating for the misleading title. There are no answers to Why, or even How, questions. What the author offers is awe -- particularly in terms of scale -- and honest, subject-dictated confusion. Ours may not be a universe that wants to be understood by the likes of us.

I was a bit disappointed by his skimpy discussion of fine tuning and the multiverse. The author is better at sharing enthusiasm for what he knows well from lab experience, a bit less engaged when having to dive into pure speculation. But that seems fair enough.

Oluyesi seems very authoritatively up-to-date on recent and current developments.

[Andrea Wenger]

This book asks big questions about humanity's purpose, origins, and future. It explores existence through nine interwoven realms: from our familiar Middle Realm to the Quantum and Cosmological Realms, which follow their own rules. The author blends physics, personal stories, and philosophy to offer a clear, humorous, and honest blueprint for understanding reality and finding hope in an indifferent cosmos.

This is the kind of popular science book I love. It's written in a conversational style, making it easy to understand for non-scientists. The tone is friendly and fun. The science seems up-to-date, and I enjoy the author's perspective on how the universe works. The book feels very down-to-earth (lol) and sensible, rather than sensational and speculative. While a lot of information is covered in a relatively short book, it never feels dense. It's exciting and a pleasure to read.

Thanks, NetGalley, for the ARC I received. This is my honest and voluntary review.

[Joda Swisher]

Hakeem Oluseyi has done something remarkable with Why Do We Exist? The Nine Realms of the Universe That Make You Possible. Astrophysics can easily feel overwhelming, but Hakeem brings a rare warmth and approachability to the subject that makes complex cosmic concepts feel seamless, engaging, and deeply personal.

​Breaking down the grand tapestry of our universe into nine distinct realms gives the book a fantastic structure. The narrative flows naturally from the microscopic scales of physics to the vastness of the cosmos, all while keeping the human element front and center. It’s equal parts mind-bending science and an inspiring reflection on how incredible it is that we’re here at all.

​I’m fortunate enough to know Hakeem personally, and reading this feels just like sitting down for a conversation with him—brilliant, passionate, down-to-earth, and endlessly curious. Whether you’re a lifelong space enthusiast or just starting to look up at the stars, this is an absolute must-read.

[Andrea]

This was a clear and fascinating explanation of some current theories in astrophysics. The author has a great narrator voice and is able to explain complex ideas with humor and clarity. I felt like the last chapter, for me, was just personal speculation. While the author obviously wants you to read the entire book from start to finish, I found it was easier to keep engaged and worked well to skip around a bit. So many good popular physics and astrophysics books coming out right now and this one was excellent but not the one I would begin with. Also, read the author’s previous book which is a memoir of growing up poor and Black in the US.

[Alex Shrugged]

I loved the author on the Science Channel "How the Universe Works" so I was looking forward to reading this book. I was not disappointed.

Aside from the expected walk through science history, astronomy, physics and cosmology which I have read in similar books on this subject, I loved listening to his autobiographical notes along the way. I wanted to know more about him. He always seemed so enthusiastic on TV. He narrated the audiobook with equal enthusiasm.

I think I'd like to listen to this audiobook again real soon.

[Remo]

Good book, goes in depth into a lot of physics. I listened to the audiobook, narrated by the author, and he was good, but I wish I’d read the book instead. Too much covered, too much I wanted to go back to and re-read and think about. It covers all the way from subatomic particles up to the entire universe, and possibility of multiverses.

[Brandon Gryder]

I was mostly able to follow this. Excellent book that encompasses the smallest to the largest, the quantum to the cosmological. Anything that was not understood or did not hit home were not the author’s fault and fall squarely on my own shoulders.

[B Dog]

4.5

[Nathan]

Interesting listen. It gives a sense of awe for the universe, the earth, and for life.

[Caleb Haws]

4 stars, I listened to this. The author really helped engage me in the topic even though it is a complex one. I want to reread this because Im sure there is lots I missed.

[Andrea Marquez]

This is something you’ll like if your looking for it. Science heavy but it balances out with the authors personality.

[Sharath Reddy]

Best popular science book for cosmology I have read in a long time (maybe ever). Clear descriptions and explanations. Really impressive