An Infinity of Worlds: Cosmic Inflation and the Beginning of the Universe

by Will Kinney

What happened before the primordial fire of the Big a theory about the ultimate origin of the universe.

In the beginning was the Big an unimaginably hot fire almost fourteen billion years ago in which the first elements were forged. The physical theory of the hot nascent universe—the Big Bang—was one of the most consequential developments in twentieth-century science. And yet it leaves many questions Why is the universe so big? Why is it so old? What is the origin of structure in the cosmos? In An Infinity of Worlds , physicist Will Kinney explains a more recent theory that may hold the answers to these questions and even explain the ultimate origins of the cosmic inflation, before the primordial fire of the Big Bang.

Kinney argues that cosmic inflation is a transformational idea in cosmology, changing our picture of the basic structure of the cosmos and raising unavoidable questions about what we mean by a scientific theory. He explains that inflation is a remarkable unification of inner space and outer space, in which the physics of the very large (the cosmos) meets the physics of the very small (elementary particles and fields), closing in a full circle at the first moment of time. With quantum uncertainty its fundamental feature, this new picture of cosmic origins introduces the possibility that the origin of the universe was of a quantum nature.

Kinney considers the consequences of eternal cosmic inflation. Can we come to terms with the possibility that our entire observable universe is one of infinitely many, forever hidden from our view?

Genres: Science, Physics, Nonfiction, Space, Astronomy, Audiobook, Education

256 pages, Hardcover

First published April 1, 2022

About the author

Will Kinney is a Professor of Physics at the University at Buffalo, the State University of New York, studying the physics of the early universe.

Reviews

[Claudia · Rating 3 out of 5]

"God is infinite, so His universe must be too.... He is glorified not in one, but in countless suns; not in a single earth, a single world, but in a thousand thousand, I say in an infinity of worlds." Giordano Bruno

First book I read in detail about the early universe and its formation. I've always wondered what was before Big Bang but it looks like scientists are still wondering too. A lot has been discovered but way much more remains unanswered, and probably will remain so forever.

It was a fascinating and intriguing read, especially the theory about the multiverse. Up until chapter 6 it was quite easy to read, but afterwards it almost lost me: I'm no physicist and all those equations accompanying explanations of various principles where over my head.

The writing is smooth but overall it sounds like a course in higher physics. You have to have more than basic knowledge to grasp everything in this book. I still recommend it you are interested in the subject.

>>> ARC received thanks to  MIT Press  via NetGalley <<<

[Brian Clegg · Rating 3 out of 5]

There is something rather odd about this book on cosmic inflation. Will Kinney assumes a considerable amount of foreknowledge in the reader - for example, he uses electron volts as a unit of energy without unpacking the concept and throws in everything from 'the unification of strong and electroweak forces' to 'the Hawking radiation of black holes' as if these are topics with which the reader will be comfortably familiar, no explanation needed. The problem with this is, if you know that much, you are probably pretty clued in on the basics of cosmic inflation too, so I'm not sure who the target reader of this book is. This is not helped by a series of light cone-based diagrams that convey nothing much at all.

Inflation is a strange subject. It's a patch to fix the Big Bang theory so it can cope with the way that the universe is unexpectedly homogenous and flat (in the sense of (not) curved space), a patch that has limited evidence to back it up. Kinney emphasises where inflation makes confirmed predictions, but also notes that it has its failings - it's the kind of topic where speculation tends to be piled on speculation. An Infinity of Worlds does quite a good job of explaining the nature of inflation, but, as tends to be the case in books on this topic, it is less successful on making symmetry breaking and eternal inflation accessible and comprehensible.

Kinney sometimes throws aspects of current theory into the mix without justifying them. So, for example, a lot of the early discussion in the book is based on the cosmological principle without saying why we should assume the cosmological principle holds. It's just given as a sort of cosmological axiom. The book is also strangely selective in what it questions. We read in the preface that Kinney 'has chosen to give short shrift to theories of modified gravity…' - but it seems odd to treat dark matter in this way when the whole basis of the book - inflation - is described as 'a highly speculative idea'. The degree to which dark matter is also speculative and only partly matches observation, yet is built into the assumptions, really ought to have been included.

Overall, then, some interesting content, but An Infinity of Worlds is unlikely to satisfy either the beginner wanting to understand inflation from scratch, or someone who has already read widely and wants a more hands-dirty exploration of inflation's nuts, bolts, context and failings.

[Tariq · Rating 4 out of 5]

As an undergraduate going into a masters focussing on this topic in particular. I feel somewhat qualified to review this book.

Firstly, the first 5 chapters were a slog even for me. I don’t know what it was about the writing style but he kept losing me. One of the pitfalls of this book is he introduces terms and acronyms without explanation. He wants to treat the reader like an intelligent enthusiast but misses the mark by simply assuming rather than going through the trouble of explaining, and when he does he dedicates a sentence or two then assumes it will stick in your head. Secondly, and this is just my personal take, I did not care for the evidence he provided for inflation. This is not to say I did not enjoy reading about how the predictions inflation makes were corroborated by experiment, but it could have done without the acronyms for all the experiments historically performed since no further detail was provided on how it collected the data (which I assume is because that would be beyond the scope of the book).

So why 4 stars? Well I feel like the last three chapters were so incredibly strong that they tied everything together. He balanced perfectly the knife-edge between science and philosophy, something many famous science communicators fail at. Staying true to empiricism and taking an unbiased approach to the evidence in the summary. Acknowledging the boundaries of science with a healthy skepticism at what is achievable given the history of our countless failures to estimate the impossible. I left the book feeling a wider appreciation for the pursuit of science, for the boundaries of the theory and asking myself how we could ever probe the beginning, all while gleaning new information (albeit low-resolution information) of the the theory of inflation. His use of analogies and the continuity of these analogies as he adds complexity is wonderful and allows you to keep track of the mechanisms he is explaining. In the final chapters he explains these more than once which I welcome as it keeps me engaged and more likely to understand the concept.

The chapters still fall prey to some of the mistakes in previous chapters, however it is far more forgivable in this case as it would take an entire book to attempt to explain in laymen terms string theory, quantum gravity, topological defects etc. I think he did as well as could have been done with the last 80 pages.

Overall, I would recommend this book to anyone who has previously read laymen’s books on the topics of black holes, string theory, or quantum gravity. Or for any aspiring (or current) physicist that wants to get a more honest feel for physics (specifically precision cosmology) while maintaining the wonderment that accompanies many of these books today.

[Christopher · Rating 4 out of 5]

There are so many physics books that are either too baby level (with more than half the text a requisite history of cosmology in microcosm) or too technical. This one strikes a nice balance between the two and is for the amateur and hobbyist who has started to break out into more advanced concepts. This is how I wish more book is the genre were like.

I am still, however, a skeptic on multiverse theory. But the author acknowledges that this is the only universe we can work with and so doesn't get lost in that. What we get is a case for inflation's centrality in the evolution of the cosmos and its role in the geometry of spacetime.

[Philemon - · Rating 4 out of 5]

This looks to be a very good account of inflation theory. Unfortunately, even though written in clear words and not formulas, it proved a bit too technical for me. I'm glad to have it, though, and hope to get back to it before too long after I've read more elsewhere.

[Anthony · Rating 3 out of 5]

This book was a rollercoaster and at 200 pages, took me longer than I anticipated to get through. The beginning of this was a full 5 stars - walking the reader through the standard cosmology and standard model of physics in such an easy and compelling manner that I wanted to have him as a teacher. This really demonstrated to me how powerful a science writer Dr. Kinney is, and I even began to recommend this book to others. An Infinity of Worlds is also a new book, so he has had a chance to incorporate some of the last 'pre-Webb' insights on the science of the big bang.

However, after the honeymoon phase of the first 100 pages, the book began to morph from an easy to read and insightful update on cosmology to a more math heavy piece that failed to separate the technical discussions from the intuitive explanations that help me grasp the most important pieces of every scientific theory I read about. I'm not opposed to math - considering the science and physics reading I do, it comes with the territory; however, I have come to rely on a strong intuitive description of what it is the math is supposed to explain in order to fully process the content as a non scientist. Many authors do this by putting the technical description in a shaded box, or limiting it to descriptions underneath illustrations. Other authors, such as John Gribbin, give a full qualitative description of the concepts and then proceed to show how the math behind the concepts works.

Dr. Kinney begins with the math and makes you hunt in between calculus formulas to find the textual descriptions of what is going on, and in many cases these descriptions are incomplete. I'm not sure why this happens either, given he covers relatively complex scientific concepts very elegantly in the first 100 pages without this reliance on calculus in what is supposed to be a popular science book.

Despite this challenge, I did expand my mental model of the early universe and I feel much more confident explaining inflation and how it relates to the big bang or 'the hot part' of the big bang phenomenon. I also understand much more intuitively how classical and quantum gravity fit in to primordial cosmology and also cause many problems, a strong argument for all the focus on finding a theory of quantum gravity. And perhaps most interestingly, Kinney introduced me to the concept of superhorizon primordial waves - taking away even the possibility of ever observing and testing theories that go beyond the final 80 doublings of the inflationary period of the beginning of our universe. It sounds like there are not only things we don't know today, but there are things that we will never be able to know about the beginning of our universe, since they are beyond our cosmic horizon.

So maybe 3 stars is a little harsh, but given that 5 stars in my rating paradigm denotes a book that changes me thoroughly after reading it, and 4 stars is a superb and excellent book, this one was less than that. I'd do a 3.5 or even 3.75 if that was available, but I can't round up to 4 for this one.

[Alex Nagler · Rating 4 out of 5]

A thorough astrophysics primer, going from the simple to the incredible complex over the course of the book. The diagrams are very, very beneficial in explaining the concepts, detailing the discussed concepts in easier to comprehend ways.

[Frank · Rating 3 out of 5]

An Infinity of Worlds is a dense and thorough, though not long, overview of inflation, the scientific theory that the "Big Bang" was caused by the sudden expansion of the nascent universe by immense scales. Kinney, a physicist who has been intimately involved in the study of inflationary theories (there is more than one version), further shows that inflation almost inevitably leads not to just one universe, but a whole multiverse filled with infinitely many universes like, and unlike, ours.

This not a book, perhaps, for the reader who is a novice to cosmology, though it is well and clearly written. It is admirably thorough, but does get technical in a number of places, and does contain the dreaded equations. I admit that my eyes glazed over at times. But that is not Kinney’s fault, or takes away the worth of the book. Its intended audience simply is not quite “general”; though an advanced degree might not be necessary to understand it, some prior familiarity with the concepts is definitely useful.

[Doctor Moss · Rating 4 out of 5]

I started studying astronomy and cosmology as an undergraduate student a very long time ago. I remember an open-ended final exam in my cosmology class in which we had to answer one question — describe the first 3 seconds of the universe. That would take many volumes now.

Kinney divides the first second of the universe into six different eras, bounded on the later end by the birth of the first atoms and at the earlier end by “The Planck Era,” the first 10 to the minus 43 seconds in which physics fails us. The Planck Era is the era of quantum gravity, for which we have speculations but no accepted theory.

I wanted to read the book in order to fill in my fuzzy understanding of those earliest eras. A lot in the field has changed since I first studied those first (nano) moments, and I’ve tried to keep up, but it ain’t easy. For that matter, my understanding of the universe’s history before the origin of the cosmic background radiation, our best source of data for understanding the big bang, is sketchy at best. And that era is far more expansive than nanoseconds — that’s the first 300,000 years (give or take).

Kinney’s book helps, but not as much as I’d hoped.

Let’s start with the good.

This is an astrophysicist talking in the present tense about the questions that he’s actively researching. It butts up against the limits of scientific knowledge, both the limits of today’s theories and the ultimately unfathomable.

As such, and as Kinney kind of reluctantly admits, we come as much to a philosophical as a scientific endpoint. What can we say about the unobservable?

The unobservable pokes holes in any hope for complete understanding on both the scale of the very early universe, at energies unimaginably beyond anything we can recreate in particle labs, and at a much more macro scale, as the expansion of the universe has long ago carried regions of the physical universe well beyond our “cosmic horizon” — the limits imposed by distance and the finite speed of light.

Kinney neatly develops a set of three fundamental problems with our understanding of the earliest eras of the universe:
- its remarkable homogeneity in terms of density and temperature, given that that homogeneity stretches across regions of the universe that cannot be causally related to one another (due to the universe’s expansion rate exceeding the speed of light)
- its complementary inhomogeneity, the very small scale clumping of the early universe that is responsible for the structure we see today — galaxies, clusters of galaxies, and the even larger-scale web-like structures that crisscross all of the observable universe
- its flatness, that is, a lack of any discoverable spatial curvature to the universe as a whole.

That set of problems sets up the main body of the positive theoretical discussions in the book, inflation theory. Cosmic inflation — an extremely rapid period of expansion, during a tiny fraction of that first second.

Inflation is a conjecture, not a “proven” theory. But it’s our best current conjecture for dealing with those three problems that Kinney articulates.

Much of the book is taken up with Kinney’s discussion of exactly how inflation theory solves those problems, and what problems it poses on its own. Inflation theory is a genuine scientific theory, in so far as it does yield predictions that can be tested. Not all can be tested, but so far so good.

It’s also not the end of the story. The details of inflation theory lead to questions about what caused it, what ended it, dimensionality, multiverses, primordial gravitational waves, . . . . , some of which are explorable and others that may not be.

Not all of Kinney’s explanations are easy to follow. This is both to be expected and disappointing at the same time. Kinney is a working scientist, not always the best kind of person to explain complex physics to general audiences. There are jumps and gaps, and I found myself going back to re-read and to consult other sources to try to fill in.

If you haven’t read Alan Guth’s book, The Inflationary Universe, I recommend reading it even before reading Kinney’s book. Guth is the originator of inflation theory, and his book is his own story of its invention and of why something like inflation theory is necessary.

Did Kinney’s book scratch my itch? Somewhat. And maybe that’s all you can ask for with the state of current cosmology, at least in a book for a general audience. No, you aren’t going to understand everything you want to understand about inflation — I don’t. But I’ve advanced my confusions and questions.

[David N. · Rating 5 out of 5]

If you want to understand how cosmologists today answer the question of why the universe looks the way it does, look no further than this book. It explores the theory and the data behind the theory of cosmic inflation, and while the concepts Kinney illuminates are difficult to grasp and very strange indeed, he makes them accessible through the brilliant use of analogies, diagrams, and examples. What I found most compelling is his discussion of how precise cosmological observations are strikingly in accord with the theory as elaborated by people like Alan Guth and others, including Kinney himself. He is also careful to distinguish what we know from what we don't know, the latter being quite a large part of the picture as it stands today - a lot more work to be done! A very important book for those of us who come to the subject without much specific background in the field.

[Michelle · Rating 4 out of 5]

I've read a fair number of basic books about the very early universe, which equipped me to read and understand (most of but not all of) this book, but I would not have been ready without that background! There was quite a bit of technical stuff in here, some of which was explained well and some that wasn't.

Having said that, having a book focused on inflation - an intriguing stage of the universe that is widely but not universally accepted as part of the Standard Model of Cosmology - was useful to me, and answered some key questions I had from other books while raising others that I desperately want answered.

Kinney goes on from the basic model of inflation to discussing the concept of eternal inflation and how it could create a multiverse, and then delves into some philosophical points about how even the multiverse isn't necessarily a solution for the anthropic principle.

[Dániel Darabos · Rating 4 out of 5]

I read it last year. I've heard "inflation" thrown around before, but never knew what it meant. I think this book does a perfect job of explaining it. It explains the foundations of cosmology that are generally accepted. It explains the observations that need a new explanation. It enumerates the proposed explanations and why inflation is the best. It covers testable predictions. And untestable possibilities, which are perhaps meaningless from a physics standpoint, but enjoyable to consider nonetheless.

All that is explained without maths. The author has a lecture series on YouTube that goes into the technicalities. But I certainly appreciated the simplified version!

[Andrea Wenger · Rating 4 out of 5]

This book focuses on cosmic inflation and other theories about the origin of the universe. The writing style is one of logical arguments rather than storytelling. For this reason, the book reads more like a textbook than like a book meant for a lay audience.

I did learn some things, but I'm going to have to read it again to get a full understanding of the concepts and arguments. Fortunately, the book is short, so rereading it won't be a chore. If you want to know more about the latest theories regarding the Big Bang and cosmic inflation, this book is worth a read.

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

[Todd Pinchevsky · Rating 3 out of 5]

Although I think Prof. Kinney referred to this book as a "popular science" book on a podcast recently, that's not what I found. Although not heavy in the math, it still seemed pretty technical to me (just a hobbyist). That being said, and as someone who has done a bit of self-study, it did clear up for me the concept of inflation (mostly). But it was a bit of a dry read. Just could have used some flourishes (which may just be to my personal liking - I enjoy armchair philosophy along with my physics).
Still, I felt I learned a lot about inflation, the Higgs field, symmetry/unstable and stable states, Mexican hats, and beer bubbles as an example of the multi-verse.

[Eric · Rating 4 out of 5]

In An Infinity of Worlds from MIT Press, physicist Will Kinney takes the reader on a deep dive into the theory of cosmic inflation, looking into the origins of the universe and what it may mean to be forever expanding. This book was a fantastic read, and I very much appreciate that Kinney sets the table early on in the book - he has no intention of tiptoeing through a light explanation of cosmic inflation but instead intends to challenge the reader to keep up with a detailed yet still very accessible journey through the topic. Well worth a read if you enjoy books covering topics in cosmology. Here’s to hoping that we see more books from Kinney in the future!

[Miss Katiebelle · Rating 5 out of 5]

In depth yet concise, this book certainly requires at least some knowledge of the physics and mathematics concepts involved, but for a book on this topic it shouldn't come as a surprise. With popular science books on cosmology you often end up with many many books painstakingly going over the basics to give a lay-reader an understanding of the theories, this one doesn't and is all the better for it. Thoroughly enjoyed this and the intellectual challenge.

[Anthony O'Connor · Rating 3 out of 5]

not a bad book

It starts well and it ends well. It’s just in the middle that it gets a bit scrambled up and impossible to follow. I am sure that author knows what he is saying.
There are a few basic take away points. Hot Big Bang. Inflation. Eternal inflation. It’s all pretty hard to understand. I don’t think a book of this type and size can say anything very useful beyond that. And it doesn’t.

[Leo W. · Rating 3 out of 5]

This book is billed as an 'accessible' treatment on inflation. I don't know that I'd consider it accessible; I audited the graduate curriculum in astronomy at a 'major research university' - including a graduate Cosmology course - and I still found it at times challenging. I learned a few things, though, and that's more than enough for me.

[ᛚᚨᚱᚲᚨ × ᚠᛖᚾᚱᛁᚱ (Semi hiatus) · Rating 4 out of 5]

As a space enthusiast, I couldn't help but to enjoy this book!
The author really knows his field, and he has no problem explaining both with words and illustrations the wonders of the universe.
I would still recommend it to anyone, but maybe especially to people whom has also read other books on the matter.

[Javier · Rating 5 out of 5]

This one is the “real thing”.

I loved the first 5-6 chapters and the approach taken by the author, not shying away from using some equations when necessary and relying on plenty of drawings and graphs to explain the key concepts instead of endless descriptions. The end is a bit dense, but understandably so.

One of the best books I have read and maybe the best one on cosmology.

[Adam · Rating 4 out of 5]

A solid read but only digestable for those with prior interest and exposure to cosmology. I would have liked some more diagrams explaining the concepts. I did learn quit a bit new about the theories of the early universe.

[Louis Lendi · Rating 3 out of 5]

Very thorough, but a lot went over my head. When I hit the halfway mark of the book, I also hit the halfway mark in my comprehension. I may try rereading in a year or so...

[Bruce R.Lasker · Rating 5 out of 5]

An objective view of inflationary cosmology

Material was mostly accessible to the educated non physicist. There still are a few equations and arguments that require explanation.

[Ian · Rating 3 out of 5]

Interesting, but does require familiarity with many of the concepts beforehand (i.e. not really suitable as a complete intoduction).

[Dave Dolan · Rating 5 out of 5]

Kinney is accessible, thorough, and entertaining.

[Forest Ormes · Rating 3 out of 5]

Kinney reviews the process behind unverse expansion, explaining along the way that multi-universes include distances so great we can not extend our measurements further. The expansion of space exponentially expands the universe. He explains this clearly. Curvature, flat univirse concepts get reviewed. I was handicapped by being restricted to an audio book. Thus, it was harder to backtrap and reintergrate scientific language.
My rating of two stars is based on Kinney's modest success at taking complex concepts and rendering them into a smooth, easily understood narration. With an audio book, this is exacerbated. At one point in chapter 3, the narrator speaks in almost incomprehensible scientific language. A physical book would have allowed retracing the terms, but even then it points to a failure. I have read numbers of books on astro-physics. The better authors render the subject easily accessible to an informed lay person. Kinney does not shine here.
I recommend the subject; mixed recommendation of the author.

[Jon Nadler · Rating 5 out of 5]

Describing the Big Bang is not an easy task. I know, for I used to try to teach it to undergrads in a not-for-science majors astronomy course. I think Prof. Kinney does a grand job of it.

[WorldconReader · Rating 3 out of 5]

The book "An Infinity of Worlds" by Dr. Will Kinney (Professor in the Department of Physics at the University at Buffalo, the State University of New York) uses quantum theory to explain the origin of the universe with an emphasis on the theory of inflation (expansion of the universe) in the first few seconds of the universe.

By choosing to read this book, I anticipated a review of traditional cosmology to brush up and learn a bit more about the field. I got much more than I anticipated. In addition to learning a few straight-forward tidbits about astrophysics, I was also exposed to a number of new quantum theories on the origins of the universe. I don't feel qualified to repeat anything about quantum physics, but regarding more traditional physics, I now finally understand why the phrase "light cone" is used. After reading about this many times before, I always thought the correct phrase should be "light sphere", but I now know that it is called a "light cone" because in a 3-d graph, one axis is time, and the other two represent space, hence the possible places that a photon could travel form a cone. (Rather than a snapshot I imagined a simple growing sphere of where a photon could be in 3-d space) The other thing I learned was that I too mistakenly thought that the Big Bang started out as an infinitely small point in space,

The author smoothly addressed several of my concerns within the text as I read it. For example, reading the first explanation of dark energy increasing as the universe expands, I paused to think about it for a moment, concluding that it seems very wrong. The very next sentence was: "If this seems to violate the conservation of energy, that's because it does." Later on in the book, I was wondering how the "cool" post inflation universe becomes the "hot" universe we expect at that point in history. There the author reassuringly wrote that "The details of this "reheating" process depend mostly on unknown physics." I say, "reassuringly" as much of the discussions of quantum mechanics are not clear to this reader, so each time I read that certain processes are not yet understood, it makes me feel better for not intuitively grasping either quantum mechanics or several chapters of this book. (Well, that and the oft heard quote: "If you think you understand quantum mechanics, you don't understand quantum mechanics".)

I definitely encourage readers that like astrophysics, cosmology, quantum mechanics, and learning new things to consider this book. For those of us without a graduate degree in quantum mechanics, I would suggest starting with the glossary and pondering Wikipedia for any items that are not immediately clear. The "Further Reading" section also has some excellent suggestions of other related books.

I would like to thank Dr. Will Kinney and the MIT Press for graciously providing a temporary electronic review copy of this book.

[Nirmalya Kajuri · Rating 5 out of 5]

Disclaimer: Will is a friend and (consequently) I own a signed copy.

An Infinity of Worlds is a masterclass in cosmology. Unlike most modern non fiction with lengthy personal stories and frequent author insertions, this book dispenses with the fluff and dives straight into the science.

The science in question is "cosmic inflation." Till the 1980s, cosmologists were convinced that the universe began its life as a hot, dense gas aka the "hot big bang" and slowly cooled down. They now believe that the hot big bang was not the start. There was even an earlier epoch where the universe ballooned up at a breakneck speed...aka cosmic inflation. The theory of cosmic inflation explains a lot about why the universe is the way it appears. It also typically leads to the existence of a Multiverse; multiple universes outside our own!

"An Infinity of Worlds" is the story of how cosmic inflation shaped our universe and beyond, told by one of the world's foremost experts on the subject. It is a worthy successor to Steven Weinberg's masterful but pre-inflation magnum opus "The First Three Minutes."

aIoW is lean at 200 pages but it covers a lot of ground. By the end, you will be brought up to speed on the state-of-the-art in modern cosmology. Being a physicist, I was worried that I might be bored because of my familiarity with much of the material, but it was far from the case. I gained a few new insights instead. What I liked most were the clarity of the expositions, the sparsity and the surprisingly high quality of the prose.

"An Infinity of Worlds" is the pop-sci equivalent of a cup of rich black coffee sans sugar or cream. Start your day with it!

[Tania · Rating 4 out of 5]

Cosmic inflation is a fascinating cosmological theory. A very interesting book. Just a little too technical.