Look out of your window. What do you see?
When we look around us, we're confronted with the world that we live in. We
accept it as real, take it for granted, don't worry about it. It's there,
it was there yesterday, and it will be there tomorrow.
Right?
Well, not quite. The world that you see today is a different one than the one you saw yesterday, and also a different one than the one you will see tomorrow. The changes are not dramatic, so it's easy to overlook them. But they are real. Today, now, this moment, will be gone forever by the time you finish reading this sentence. Reading this sentence has changed you forever, in a way. You have changed from someone who doesn't know the contents of the sentence into someone who does. An insignificant, even trivial, difference. But a difference nonetheless.
Consider, for example, the world of a small child. Let's say it consists of a home, parents, perhaps brothers or sisters, playmates, toys, food, etc. It's a limited world, but more than enough for a young child. Foreign countries, the layout of the solar system, or the finer details about sub-atomic physics are not a part of it. Time is defined as 'when something happens': time to eat, time to sleep, time to be taken somewhere. 'Yesterday' or 'next week' are not an issue to a newborn. Space is defined at 'where something happens': outdoors, at home, in the playroom, at Grandmother's. That is all, and the child doesn't worry about it.
When the child grows up, that world expands. It starts to include other
places, other people, school, etc. The child learns about parts of
the world it has not seen yet: other places, other countries, other
continents.
Time also expands, and the concepts of past, present and future are added.
At school, the child is encouraged to tell what it did during summer
vacation, and is taught about history and the past. There will also be
plans for the future, like wanting to become a police officer or to join
the fire brigade.
Later still, the child may grow up and learn about mathematics, or
chemistry, or physics. What used to be just a circle now becomes a body
defined by center coordinates, radius and circumference. What used to be
sugar now becomes a compound of carbon, oxygen and hydrogen in a certain
configuration. What used to be a rock tossed through a window now becomes a
body subject to the laws of mechanics.
Or the child might start studying psychology, and be amazed to learn what
is behind the seemingly illogical behavior of people. It might study
economy, and learn how the actions of nations on the international stage
are dictated by supply and demand. It might study any other discipline and
be amazed at how logical and transparent a formerly incomprehensible
phenomenon really is.
So, as we learn, our understanding of the things that surround us change
as well. But we reason that things are as we see them. In
other words, if we learn more about reality, the way we expect it to behave
changes accordingly. For example, with only the laws of Newton and Kepler
in mind we might make a prediction about, say, the orbit of a planet. We
find that the actual orbit of the planet matches the prediction, and we
declare that we understand why it behaves the way it does.
Einstein's Theory of General Relativity, however, adds a new dimension,
predicting that mass will warp space, thereby influencing the behavior of
moving bodies. The orbit of Mercury, that had been inconsistent with the
laws of mechanics so far, now turns out to match the orbit predicted by the
new theory.
Newton and his contemporaries would never have dreamed that space was
curved. To them, space was space, a well-known set of three dimensions, in
which a set of rules could be used to describe motion. To us, however,
space is curved by the presence of mass, and we include that
'new' aspect of space in the set of rules that we use to describe it.
In 1884, Edwin A. Abbott published his famous 'Flatland'. Flatland
is a two-dimensional world, where length and width are the only spacial
properties. Height is non-existent; the height of Flatland is zero (so that
it, in a way, can not exist within three-dimensional space: a sheet of
paper with a thickness of zero does not exist).
Flatland is inhabited by two-dimensional creatures. They move around in
their two-dimensional space (picture this as geometric figures moving
around on a sheet of paper) and are restricted by the limits of that space.
You can effectively 'lock up' a Flatlander by drawing a circle around him
(or her, as the case may be). The Flatlander can not 'step over' the line,
because 'over' is a three-dimensional concept that involves height, and
height is not a part of the Flatlander's universe. He doesn't even know what
it is. He doesn't even realize that there could ever be such a thing as
height.
Now imagine that a three-dimensional creature (you, I, your neighbor) watches Flatland from our three-dimensional space. We might have trouble understanding why the Flatlander cannot escape from his confinement just by stepping over the line around it. We might reason that his confinement is only an illusion, that what is an impenetrable wall to the Flatlander is only a thin line to us, and a line with a height of zero at that. Reality is different to us than it is to the Flatlander. Our points of view are different, the limits imposed upon us by our frame of reference are different.
Now magine a sphere, a three-dimensional object, that passes through the
two-dimensional plane that is Flatland. To us, it's just a sphere that
moves through the vertical, like a soap bubble rising up through the
air.
To the Flatlander it will be a different, and probably unsettling,
experience. A point will appear out of nowhere, and rapidly expand into a
circle. The circle will reach a maximum size, then shrink again into a dot,
and vanish without leaving a trace. Any Flatlander who is witness to such an
astonishing event will have serious trouble explaining what he saw to the
other Flatlanders. There's a high risk that he will be locked up in an
institution for the insane, or worse.
Now suppose that a Flatlander has a sudden flash of insight. Suppose that he suddenly realizes that, by postulating a third dimension, he is able to explain what happened. His brilliant concept also enables him to understand other enigmas. He envisions how two cubes could be stacked on top of each other, so that, from a two-dimensional point of view, the two objects can be in the same place. (After all, they cover the same surface on the two-dimensional plane.) He also envisions how one could travel through the third dimension, from one point in Flatland to another without having to pass any of the points in-between, and undetected by the Flatlanders. Maybe he even toys with the idea that what he sees as a square or a circle is in fact the two-dimensional aspect of something quite different, like a cube or a sphere. He might think of himself as the two- dimensional aspect of a higher-dimensional being.
Make no mistake: postulating a third dimension is quite a feat for a
Flatlander, because it involves a dimension at a straight angle to reality.
Also, this is a very difficult concept to explain to the other Flatlanders.
The others will be reluctant to accept his hypothesis, since 'everyone can
clearly see' that there is no such thing as a third dimension. Besides,
having evolved in a two-dimensional frame of reference, the Flatlander mind
is unable to visualize what a third dimension would look like.
The scientific community of Flatland considers the concept interesting, but
no more than that. If that hypothesis holds water, they reason, then
testing it will lead to a theory, and that theory might then be used to
describe how such events will occur in the future. If the predictions are
accurate, the theory can be assumed to be correct. So they sit and wait
until our poor Flatlander comes up with experiments to test his hypothesis.
Until he does, they will have none of it. That it is beyond a Flatlander
to venture into the third dimension and to experiment with it does not
impress them very much. After all, only a crackpot would come up with a
hypothesis that goes beyond the limits of Flatlander observation.
Good question. The Flatland concept is, of course, an analogy to our
three-dimensional reality. And it's easy to see how it affects us by lifting
it from the two-dimensional frame of reference to the three-dimensional.
Just think of our universe, our reality, as a three-dimensional version of
Flatland, with three-dimensional objects (cubes, spheres, cones, polygons,
and any possible combination thereof) moving around in three-dimensional
space.
(Also bear in mind that the Flatland analogy only deals with spacial
restrictions. But the concept applies to all limits of observation, be it
spacial, temporal or otherwise.)
"Everthing you've learned in school as 'obvious' becomes less and less obvious as you begin to study the universe. For example, there are no solids in the universe. There's not even a suggestion of a solid. There is no absolute continuum. There are no surfaces. There are no straight lines."
-- R. Buckminster Fuller
What if there is more then just the three-dimensional space that we
perceive? What if our reality is, so to speak, a 'subset' of a set of
'higher' (i.e. more than three) dimensions?
What about phenomena that occur in this three-dimensional space, that
baffle any observer, defy any rational explanation, and go against our
common sense of what is possible and what is not?
Yes, what about them? We face the same problem here as our visionary Flatlander did: we postulate something that is, inherently, beyond the limits of observation. We come up with a hypothesis that can't be tested by conventional methods, and that can't be developed into a real theory, because the events that such a theory would describe are beyond our ability to observe, not to mention our control. We have, in essence, asked ourselves a question that can not be answered with the traditional scientific method.
There are several courses of action open to us. For example:
Without getting too existential, it is easy to see that two observers
can experience the same reality in different ways. The sphere that passes
through the plane of Flatland would look different to a Flatlander than it
would to a human observer. Yet it is the same sphere.
Our hypothetical visionary Flatlander could also be said to change his own
reality, or rather to create an extension to his own reality. By learning
about the third dimension, he no longer sees his reality as a
two-dimensional plane, but as a two-dimensional aspect, a subset if you
will, of a higher-dimensional space. To him, the universe isn't what it used
to be. Reality has changed, and, accordingly, his position therein
has changed.
Is reality indeed a subjective experience? You tell me. We assume, for
practical purposes, that what we see is in fact true. If I meet a friend, I
assume that he is real, instead of being a product of my overexcited
imagination. But I have no way to be 100% sure of that. I don't worry about
it, since the question can not be answered, and doubts about my reality
would leave me unable to function. But if we take a really critical look at
reality, there is no way to be absolutely sure that what we see is in fact
real and not an illusion.
Fortunately, this sophomore philosophy isn't that important in everyday
life. Something is real or it isn't, and if it's an illusion it's a very
good one, that can be treated as real for all practical purposes. But if we
want to explore the limits of reality, we need to question ourselves: how
do we know that something is real? Do we know that something is real? And
if it isn't, does it make a difference?
Philosophers have pondered these questions, and more, for centuries. They
have failed to come up with decisive answers. In the mean time, we draw our
own conclusions about our own subjective realities. If we don't like them,
we change them. In a way, we create our own realities, and largely without
realizing it. Learning, growing up, participating in religion or science,
changing ourselves by new experiences, or gaining new skills, insights and
knowledge are all part of this process.
Descartes had a point with his "Cogito ergo sum": I
think, therefore I am. But it doesn't end there. I think, therefore
reality is. I think differently, therefore reality is different.
As I change, my world changes accordingly. I don't know about yours, I can
only speak for myself, but mine does.