What is time? A slice of a 4D universe.

February 27, 2010

Just read this article in Wired about time:

http://www.wired.com/wiredscience/2010/02/what-is-time/

Like every geek, it's a concept that's fascinated me. And like
everyone, I have no real clue. But here's my theory nonetheless:

Time is just a slice of a 4-dimensional universe.

Said another way, the universe is a four-dimensional, static block, and
any particular "point in time" is just a slice through the middle. Make
sense? No? Let me try to build it up.

Imagine a one-dimensional universe. There's up and down, but nothing
else. Just one dimension. If you're a dot in that universe, you can
move up, then back down, and that's it. However, the very notion of
"motion" implies time — at some time in the "future" you're in a
different position than a different point in the "past". So just like
up and down, time is also a dimension, with two directions: future and
past. So as a dot in a one-dimensional universe, you're actually moving
in two directions: up/down, and past/future.

Accordingly, this one-dimensional universe, if it can change, is
actually more accurately described as a two-dimensional universe.
There's up/down, and past/future. Two directions, and you're moving in
both.

This universe is easy to visualize: think of a heart monitor. Any
individual number (eg, heart voltage) is a one-dimensional universe. At
any point in time, it has a single value. But that value can change
over time. As such, you can easily plot it on paper up/down corresponds
to the heart voltage, left/right corresponds to time. Your
one-dimensional universe + time has been perfectly captured as a single
two-dimensional piece of paper.

So we've got this 2D representation of a 1D universe + time. But why
are we treating time as a special dimension? Why not just say we have a
2D printout of a 2D universe — one dimension being up/down, the other
dimension being time. The 2D universe is the *whole thing*. The only
reason we ever saw it as a 1D universe was because we were explicitly
ignoring the time dimension.

Indeed, the only way to see a heart monitor as anything other than a 2D
universe is to explicitly focus on one slice of the page and ignore the
others. We call that slice "time". And the fact that different slices
of the page map to different "times" is merely a matter of observation
— the paper itself doesn't change. The 2D universe itself is totally
stationary, fixed, static, and unchanging. Only our point of
observation changes; the only change is *us* changing what part we're
looking at.

For example, imagine you took another piece of paper, with a tall slice
cut through it, and laid it over the first. It would show a single
slice of time on that paper; it'd show the position of the dot at one
"point in time". Slide the paper from left to right and the point
appears to move — even though in fact the paper underneath it isn't
moving at all; only the viewpoint is moving.

So from this perspective, the change of time isn't an attribute of the
universe. It's an attribute of the *viewer*. The universe — in this
case, a 2D printout of a heart monitor — is totally unchanging. Only
our view of it changes.

Now let's add another dimension: let's do a stack of sheets of paper,
like a book. Each page is a 2D "slice" of a 3D universe (2D + time).
Each page has dots arranged in a particular way, and any page can have a
completely different arrangement of dots. To see how those dots "move"
we just flip our thumb through the book. Each dot appears to "move" up
and down, left and right, when in fact it's not the dots moving — its
our thumb moving, showing us one page at a time. It's our *attention*
moving, *experiencing* one page at a time. The first and last page will
never change; but our *experience* changes over "time". Once again, the
change of time is not an attribute of the book; it's an attribute of *us*.

And this has a natural correlation with 4D. Every moment of our current
universe is like a page in a big 4D book. This very moment is page 100;
a second ago was page 99, and a second from now will be 101. Those
pages are totally static — pages 1, 20, 99, and 100 are written. But
so are pages 101, 110, 10000, and 1000000. Our 4D universe (3D + time)
is totally static. The only reason it seems to change is because we're
only looking at one page "at a time".

At least, that's what I think.

So there are a few FAQ corollaries that come out of this:

– Is the universe deterministic? Yes. Every page in the future is a
direct consequence of the pages in the past. If you were to somehow
step outside the universe and look at the "page" corresponding to this
moment in time, you could completely and wholly predict the next or any
future page. I also expect you could predict every previous page.
Basically, if you were smart enough, with complete knowledge of the
current state (page) of the universe you should be able to predict any
past or future state.

– What about free will? Doesn't exist. Every action you will ever do
is pre-ordained and dictated by physics. You and everything you will
ever do is purely the consequence of actions that have come before you.
All those things you think you can take credit for? Sorry. Total
chance. But hey, all those things that went wrong, they're not your
fault either. We're all in it together, everybody a product of the past.

– Wait, seriously? Yes, seriously. Free will doesn't "exist" in the
sense that you can make some decision that isn't pre-determined by
physics. We're just characters in a book that's already been written.
But don't feel bad: though the book is written, we're all reading it
together. I have no idea what comes next chapter, and nor do you. So
it's still exciting to be alive! Free will ultimately doesn't matter
(to me, at least). It still *feels* like I'm deciding, discovering,
living, and experiencing. So why fret about the metaphysical details?

– If time is a dimension, why can't we look that way? Great question!
I've always wondered that. My best guess is because all those things we
perceive as dots — molecules, atoms, sub-atomic particles, etc — are
actually lines. And all those lines run mostly parallel, in the
direction of time. So our perception of time is to view things
perpendicular to time, because time is actually the least interesting of
the 4 dimensions. I mean, consider the room you're in now — the vast
majority of it isn't "moving". If you imagine every particle is
actually some long wire — with one end in the far past, one in the far
future, and you just seeing a tiny slice of it — that wire is totally
straight. It's super boring. Even those things that are moving are
moving pretty slow. Imagine you actually *could* look forward along
time — all you'd see are a series of nearly parallel wires extending
off into the future. It's not nearly as interesting to look that
direction as to look the other directions. Accordingly, I think we look
in the other 3 dimensions because time is boring (and there's no
evolutionary advantage to looking forward).

– What the hell are you talking about? It's hard to know. It's more of
a visual exercise — viewing the universe as a static, unchanging
four-dimensional block, and as us just being some razor-thin slice
moving through that block along the time axis. (But not really "moving"
— the part of me that existed a minute ago is still there, one minute
behind "me" right now. And all my future me's are up there waiting for
me, patiently. Consciousness being like some electric current running
along these time-aligned wires, interacting with the other currents
running along the wires nearby.)

– Ok, so this wire theory is crazy. Ya, but it creates some interesting
sub-theories. Like, isn't it strange how the perception of time changes
the faster you move? And how the perception of time in theory stops
when you're moving the speed of light? Maybe when you're moving the
"speed of light" in the three-dimensional space, *there's no more wire*
to move in the 4th dimension. You're essentially moving perpendicular
to the fourth dimension. Stick with me: the local universe around you
is like a bundle of wires, all woven tightly together. If you move
slowly together, your wire gradually weaves its way through the
super-bundle of the entire universe, eventually making it over to some
distant position. But to go faster, you need to bend your bundle at a
greater angle. To move super-fast, you need to actually bend your wires
at a 90 degree angle — meaning from everyone else's perspective, your
"wires" no longer move at all in the time dimension; they're *only*
moving in the other 3 dimensions. To them, you've disappeared. But
within your bundle, everything seems fine. The relative arrangement of
wires within your bundle seems normal — all the wires keep going
somewhere, and your conscionsness is traveling along those lines at some
constant speed. But your wires are no longer aligned with the time
axis, so your "local time" seems normal even though it's totally out of
whack with the "global time". Which means global time itself isn't
really a constant — it's just the direction that all the other wires
typically go, unless they're moving super fast in the other 3
dimensions.

– So is time a position relative to space, or relative to the wire? Ok,
my terminology is getting bad here: the "time" of any particle isn't
"absolute distance from the start of the universe", it's "distance from
the start of the universe *along that wire*". Imagine two wires, both
starting in the same place (the start of time), both perfectly straight
and parallel. Their "times" are aligned in that 1 hour in the future,
an equal amount of their "wire" has unrolled. But if one "moves"
relative to the other, it just means that the wire bends away from the
other in 3d space. The further it bends, the "faster" it's moving in 3d
space. And that speed comes *from* the time dimension. The fastest you
can possibly move in 3D space is to go perpendicular to time. So in
theory, if one atom/wire were to turn 90 degrees and run perpendicular
to the time dimension for a while, and then turn around and come back to
to its original position in 3d space, it could resume its previous
arrangement — except one "hour" of wire would have unfurled for the
first atom even though a ton more might have unfurled for the other.

– But what this really means is that the "time" dimension isn't actually
a special one in any way. It just happens to be the direction that most
of the universe's wires are aligned. Had they aligned in a different
direction, that would be the "time" dimension. But if a bundle of those
wires breaks off in a different direction, it "accelerates" in the 3
other directions while "decelerating" in the time direction. Within
that bundle everything seems totally normal — even though relative to
the other bundles it seems "wow, it's moving *really* fast in 3
dimensions and *really slow* in the fourth". I haven't really worked
out the math, but I wonder if this is at all consistent with relativity
theory.

– Isn't this called string theory? I have no idea — I don't know
anything about string theory so I can't say. I'm using "wires" as the
metaphor to differentiate my theory from that, until I'm shown they're
the same. But I think string theory is about strange vibrations. My
wires don't wiggle.

– But doesn't quantum theory say true randomness exists? I don't think
so. All I know is Einstein said "God doesn't roll dice." Yes, he was
an atheist (as am I), but I take it to mean he didn't believe in
subatomic randomness either. There have been a lot of things people
assumed were random, until we just figured out they weren't. I think
it's time to start assuming the opposite. Especially when most
pop-science theories of quantum randomness are really just scraping for
any possible way to justify an irrational, pseudo-scientific belief in
God, free will, self determination, etc.

Anyway. Gotta run. One thing I've determined is good wine doesn't
drink itself. Thank God.

-david

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