The history of science fiction is littered with tropes involving other dimensions, from
the subspace communications and worm holes of star trek, which also happen to be coupled
with warp drives working on a completely different concept of faster than light travel to Dr.
Who navigating the Tardis through what presumably is transdimensional space, these tropes provide
an easy means to go from point A to point B in space and time relatively effortlessly.
This makes for great stories, but they actually do stem from a legitimate question within
science.
Are there other dimensions that we can’t currently perceive?
This is a fundamental question, actually one of the most fundamental you could ask about
the universe.
And it’s one where there are truly fundamental disagreements within the scientific community.
One thing most of them do agree on is this.
There are three dimensions that we can perceive.
Length, width and height.
This is our 3d world and everything we do in life is defined with interacting with these
dimensions.
But behaving suspiciously like a dimension is also time, so it typically gets counted
as a fourth dimension in which we’re relentlessly moving forward but the rate at which we do
that can change.
That’s time dilation and relativity.
In different frames of reference, you can move through time at different apparent rates.
But there are further questions, if you reverse time, it’s symmetrical and moves backwards
like a rewind button, but there’s no really good reason why, which is usually termed the
arrow of time.
But as Stephen Hawking pointed out, what if there is a vertical or imaginary form of time
moving sideways, and did that relate to the big bang.
Was time itself moving sideways before the great singularity.
Are there other dimensions of time?
Physics has not fleshed those ideas out well.
Part of the problem of course is how do you measure it.
The big bang seems to have been an eraser that doesn’t give you a way to peer into
what happened before it.
If time had been standing up, going about it’s business, tripped and assumed a horizontal
position moving from left to right instead of up or down and that in turn formed a 1
dimensional singularity that exploded in to at least three dimensions while time still
wallows helplessly on the ground is simply not measurable.
That which is not measurable, is typically ignored in science.
And there are other questions, does time truly exist?
After all, if you return a group of atoms to a previous state and configuration, then
you’re just effectively reversed time for all intents and purposes.
Or in a universe where nothing ever happens, an infinitely unchanging landscape of equally
distant hydrogen atoms that just goes on forever, then does time even exist?
In such a situation, time itself becomes unmeasurable.
In some sense it still exists, but it might as well not, and that’s often how we view
whatever happened before the big bang.
Widening out, this is not so much the case for asking if there are other dimensions of
space and time.
One of our most speculative and difficult to impossible to test theories is string theory.
And this particular theory, with all of its different flavors which makes exploring it
like standing in a well-stocked ice cream parlor, which as a diabetic is dismaying as
none are sugar free, is why measurement is all important.
If you can’t measure something, hypothesize all you like, you’re not likely to ever
prove it.
So how do you know if something is real if you can’t prove it.
Such is the dilemma of theoretical physics.
String theory however does make predictions about other dimensions, most commonly nine
or ten dimensions of space, one dimension of time for a ten or eleven dimensional universe.
But there are variants where it’s an indefinite number of dimensions.
Or, it may as well be that there are no other dimensions, and what you see is what you get
with the universe.
We just don’t know.
But maybe there are hints in nature that suggest the existence of other dimensions, tantalizing
clues like all too sparse chunks of chocolate suspended in the ice cream.
Wish as we might that there were more, but no dice.
Before we get into the possibilities of other dimensions, it pays to define just what a
dimension actually means in science.
In science fiction, it can be envisioned as a whole realm, where you can be like the Q
from Trek, and play Twilight Zone games in a universe within a universe.
But that’s not really how it works, rather the whole idea of dimensions comes down to
a simple point of view.
A dimension in its purest form is just a set of directions, length, width, height, or you
can express it as X, Y and Z, or forward backward up, down, right and left.
Adding in time, it’s forward and past, but the aforementioned Stephen Hawking added more
attributes to it as though it were a full dimension as we know it.
It may have those attributes, but it doesn’t seem to let you navigate it other than move
some flavor of forward through it.
Something about the universe governs this, you can move east toward the vanilla ice cream,
but never west, meaning you can’t ever go back to mint.
Oddly though, you can still see it, after all, looking into deep space shows us the
past as the universe once was.
So the reality of other dimensions is sort of boring in that sense.
It’s fertile ground for imagining possibilities because what’s actually possible is such
an unknown, sure you can invoke upper dimensions as a way to effortlessly ply the cosmos and
go wherever you want to defeat the vast distances, but what you don’t know is if an upper dimension
actually allows that.
It’s equally probable that it simply doesn’t.
You can’t know without measurement, and that eludes us.
All we have are theories, and those theories do not necessarily paint the same picture
as science fiction does.
But ideas like string theory do make predictions, so we can at least play with what other dimensions
might be like.
But murky territory it is indeed and may well reflect nothing close to reality.
In string theory, if it’s actually how the universe works, the dimensions have specific
roles.
So think of it like this, a straight line existing only as length.
Add a dimension and you get a square.
Add a third dimension and you get a cube.
You could say that time is the fourth dimension, with the cube moving forward through it.
There ends what we can readily perceive.
Dimensions five and six, at least in superstring theory, the world would look only slightly
different.
Seeing it would give a baseline for trying to measure the other dimensions by looking
at the differences between our world, and dimension five.
Go to six, and you might see a plane of all possible universes stretching from a single
point, the big bang.
This opens up the possibility that backwards time travel becomes possible if you can harness
the fifth and sixth dimensions.
Or there may be a prohibition on it we don’t know about in those dimensions.
But those dimensions are still tied to the initial condition, the big bang.
In dimension seven, this falls apart and you have access to all possible universes including
those that do not start with the big bang.
So in five and six you get all possible worlds that stretch back to the big bang, in seven
you get all possible worlds that stretch to the beginning of time, whatever or whenever
that was.
The eighth dimension is where these possibilities stretch to infinity.
In nine, it’s all possibilities including all possible variants all of the laws of physics,
and ten covers all possibilities of everything including everything.
At that point, you’ll see Gandalf fighting a dragon that likes frozen treats, but in
that world fire doesn’t get extinguished by ice cream.
And there may be yet more dimensions after that, but physicists simply can’t envision
what they would be like.
For string theory to actually be the case however, these dimensions are absolutely necessary.
Which may mean it’s off base.
More, these dimensions have to be somewhere, and there likewise has to be a reason we can’t
currently see them, though they may have been more evident during the big bang.
This is the idea that the other dimensions have curled up and are somehow compacted,
but there’s also the idea that we live on some sort of three dimensional subset of the
universe or multiverse at large, which stems from Brane theory.
While wild stuff to imagine, none of it may exist at all.
Observations of the gravitational waves emanating from neutron star mergers seems to contradict
the idea of other dimensions.
The reason is that if those dimensions exist as we envision them, the gravitational waves
could be expected to weaken over distance traveled in a characteristic way as the gravitational
energy bleeds off into the other dimensions.
That would be required to explain the accelerating expansion of the universe in string theory.
Observationally, this does not appear to be the case, but with a caveat, it only covers
large dimensions.
Curled up or very tiny ones are not eliminated by this, and do not knock string theory out.
At the same time however, there may actually be indicators of other dimensions that we
are aware of.
One of these is dark matter.
It’s possible that the reason we have no idea what it is other than our measurements
of its gravity is because it’s simply matter in another dimension that cannot interact
any other way with the matter of our dimensions other than through its gravitational effects,
which smear across perhaps all dimensions which is why it’s so notoriously weak.
Another question is the geometry of the universe itself.
There are a number of options there that might define the shape of the universe, though current
observations point to a flat geometry for the universe.
Well, geometry into what?
Another dimension?
No one knows.
Yet another are wormholes, what do you go through when you travel through one?
If anything at all, or if wormholes can even exist.
We just know that they are consistent with relativity.
Yet another is spooky action at a distance, quantum entanglement.
How does a change in state happen between two potentially very distantly located particles
halfway across the universe from each other?
Another dimension might be the answer.
But ultimately, it goes back to measurability.
Do other dimensions even matter if you have no way to ever prove them.
Do they really offer the chance for navigation through time and other universes, the answer
is, we may never know.
It may not be possible in our universe to ever answer the question, and we, and everyone
else that may be in the universe, may forever be stuck in the dimensions we know and the
universe we see does not contain anything that would allow us to really know.
But I leave you with this question, since we know so little, what if the nature of other
dimensions and their interactions with each other is dynamic rather than set.
If something, say a manifestation of dark matter under the right conditions could be
perceived in other ways beyond just gravity.
Here the universe goes very wonky, to say the least.
But imagine for a moment if you saw it.
Would you see it as an object, or would your brain paint in some interpretation for lack
of a reference point in its normal experience as though it were seeing an optical illusion?
In short, would you see something transient and inexplicable, and would anyone believe
you if you told them?
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently hungry for ice cream,
but recognizing the cruel realities of the universe.
My favorite flavor is probably mint chocolate made with real sugar, which lies in the past,
and I can’t ever go back to it, given that I have traveled to the parallel sugar free
universe.
Sad indeed and be sure to check out my books at your favorite online book retailer and
subscribe to my channels for regular, in-depth explorations into the interesting, weird and
unknown aspects of this confusing universe in which we live.