The Biggest Ideas in the Universe_ Space, Time and Motion

295 Pages·9.869 MB·English

by  Sean Carroll

Praise for Sean Carroll
‘As a ten-year-old physics enthusiast, I would have loved The Biggest Ideas
in the Universe. With this book, Sean Carroll rejects traditional elitism in
physics and welcomes in anyone who knows only a little algebra but wants
to understand the whole universe.’
Chanda Prescod-Weinstein, author of The Disordered Cosmos: A Journey
into Dark Matter, Spacetime, and Dreams Deferred
‘Sean Carroll is a wizard of empathy. In this short book, the first of three on
The Biggest Ideas in the Universe, he anticipates what’s always confused
you about physics and then gently guides you to enlightenment… and
ultimately, to newfound wonder.’
Steven Strogatz, author of The Joy of X and Infinite Powers
‘No-nonsense, not-dumbed-down explanations of basic laws of the universe
that reward close attention.’
Kirkus
‘Sean Carroll’s greatest gift isn’t that he’s an expert on the fundamentals of
physics, which he is, but that he never speaks down to his reader. He
assumes that anyone, even the uninitiated, can learn to understand the
formulae that underlie complicated concepts like space and time. It is a
pleasure to read his work, a greater pleasure still to get a world-class
education from such a witty, thoughtful teacher.’
Annalee Newitz, author of The Future of Another Timeline
‘Carroll has the remarkable ability of putting the reader utterly at ease with
his lucid and addictive prose.’
Jim Al-Khalili
‘Sean Carroll is a fantastically erudite and entertaining writer.’
Elizabeth Kolbert
ALSO BY SEAN CARROLL
Something Deeply Hidden
The Big Picture
The Particle at the End of the Universe
From Eternity to Here

To Jennifer
CONTENTS
Introduction
ONE Conservation
TWO Change
THREE Dynamics
FOUR Space
FIVE Time
SIX Spacetime
SEVEN Geometry
EIGHT Gravity
NINE Black Holes
Appendices
Appendix A: Functions, Derivatives, and Integrals
Appendix B: Connections and Curvature
Index
INTRODUCTION
My dream is to live in a world where most people have informed views and
passionate opinions about modern physics. Where you knock off after a
hard day at work, head down to the pub with friends, and argue over your
favorite dark-matter candidate, or competing interpretations of quantum
mechanics. A world where, as kids are running around at a birthday party,
one parent says, “I don’t see why anyone thinks there should be new
particles near the electroweak scale,” and another immediately replies,
“Then how in the world are you going to address the hierarchy problem?”
People have opinions, after all, about supply-side economics or critical race
theory. Why not inflationary cosmology and superstring theory?
That’s not quite the world in which we live. Even more than most other
academic disciplines, physics is a field by and for specialists. Practitioners
talk to one another in a highly specialized jargon, one that is dominated by
mathematical concepts most people have never heard of, much less
mastered. There are sensible reasons why this is the case, but it doesn’t
have to be this way. The situation is due in large part to the ways in which
physicists tend to share their knowledge with the rest of the world.
If you are a non-expert interested in learning about modern physics, you
have basically two options. One is to remain at a popular level of
explanation, where you can learn about some of the relevant concepts
without digging into the technical or mathematical details. You can read
books, go to lectures, watch videos, listen to podcasts. The good news is
that we do have a vibrant ecosystem of such resources, and it’s possible to
learn quite a bit, albeit in a somewhat haphazard way. But at the end, you
know you’re not getting the real stuff. What you get are images and
metaphors, rough translations of the underlying mathematical essence into
ordinary language. You can go an impressive distance down this route, but
something vital will always be missing.
The other route is to become a physics student. That could be literally at
a university, or by assembling the right textbooks and online resources.
Along the way you will need to become proficient at quite a bit of
mathematics: calculus and differential equations most importantly, but also
aspects of vector analysis, complex numbers, linear algebra, and more. The
journey will be rewarding, but frustratingly slow. It typically takes at least a
year of introductory courses before a student ever hears about relativity or
quantum mechanics. And most physics students can get an undergraduate
degree—or even go all the way to obtain a PhD—without learning about
particle physics, black holes, or cosmology. Those goodies are reserved
only for specialists in particular subfields.
The gap between learning physics as an interested amateur, relying on
metaphors and murky translations, and becoming a credentialed expert,
comfortable with pushing around equations of intimidating complexity, is
wide but not unpassable. Just because I don’t want to be a professional race-
car driver doesn’t mean I shouldn’t be allowed to drive at all. Surely there is
a way to engage with some of the authentic essence of modern physics—
even if that means looking at a few equations—without slogging through
years of a standard curriculum.
You’ve come to the right place!
The Biggest Ideas in the Universe is dedicated to the idea that it is
possible to learn about modern physics for real, equations and all, even if
you are more amateur than professional and have every intention of staying
that way. It is meant for people who have no more mathematical experience
than high school algebra, but are willing to look at an equation and think
about what it means. If you’re willing to do that bit of thinking, a new
world opens up.