Editorial
Reality: ineffable, but impossible to forsake
New Scientist 01 October 2012. Magazine issue 2884.
Do we make reality, or does it make us?
Probe the existence of the universe's supposed building blocks
- quarks, electrons, neutrinos and the rest -
and you eventually end up back in your own mind.
Alternatively, discount everything human
and settle for "a world without us"
- a reality that might also be unknowable by us
(see "Reality: The bedrock of it all").
These options are as viscerally unsettling
as they are intellectually challenging.
Other possibilities
- that we live inside a video game,
say, or a hologram -
are hardly any more comfortable.
But forsaking the notion of reality is not an option, either.
Quantum mechanics may be ineffable,
but it still makes electronics work.
Wars may not "exist", but they still kill people.
The wonder of the human condition
is that to us, quarks are real.
And so is compassion.
When you woke up this morning,
you found the world largely as you left it.
You were still you;
the room in which you awoke
was the same one you went to sleep in.
The outside world had not been rearranged.
History was unchanged
and the future remained unknowable.
In other words, you woke up to reality.
But what is reality?
The more we probe it,
the harder it becomes to comprehend.
In the eight articles on this page we take a tour
of our fundamental understanding of the world around us,
starting with an attempt to define reality and ending
with the idea that whatever reality is, it isn’t what it seems.
Hold on to your hats.
• DEFINITION
Reality: The definition
New Scientist 01 October 2012
by Jan Westerhoff
Magazine issue 2884.
Even trying to define what we mean
by "reality" is fraught with difficulty
What do we actually mean by reality?
A straightforward answer
is that it means everything
that appears to our five senses
- everything that we can
see, smell, touch and so forth.
Yet this answer ignores
such problematic entities as electrons,
the recession and the number 5,
which we cannot sense
but which are very real.
It also ignores phantom limbs and illusory smells.
Both can appear vividly real,
but we would like to say
that these are not part of reality.
We could tweak the definition
by equating reality with what appears
to a sufficiently large group of people,
thereby ruling out subjective hallucinations.
Unfortunately there are also
hallucinations experienced by large groups,
such as a mass delusion known as koro,
mainly observed in South-East Asia,
which involves the belief
that one's genitals are shrinking back into one's body.
Just because sufficiently many people
believe in something does not make it real.
Another possible mark of reality
we could focus on is the resistance it puts up:
as the science fiction writer Philip K. Dick put it,
reality is that which, if you
stop believing in it, does not go away.
Things we just make up
yield to our wishes and desires,
but reality is stubborn.
Just because I believe there is a jam doughnut
in front of me doesn't mean there really is one.
But again, this definition is problematic.
Things that we do not want to regard as real
can be stubborn too, as anyone
who has ever been trapped in a nightmare knows.
And some things that are real,
such as stock markets,
are not covered by this definition
because if everyone stopped believing in them,
they would cease to exist.
There are two definitions of reality
that are much more successful.
The first equates reality
with a world without us,
a world untouched
by human desires and intentions.
By this definition,
a lot of things we usually regard as real
- languages, wars, the financial crisis -
are nothing of the sort.
Still, it is the most solid one so far
because it removes
human subjectivity from the picture.
The second equates reality
with the most fundamental things
that everything else depends on.
In the material world,
molecules depend
on their constituent atoms,
atoms on electrons and a nucleus,
which in turn depends
on protons and neutrons, and so on.
In this hierarchy,
every level depends
on the one below it,
so we might define reality
as made up of whatever entities
stand at the bottom
of the chain of dependence,
and thus depend on nothing else.
This definition
is even more restrictive
than "the world without us"
since things like Mount Everest
would not count as part of reality;
reality is confined to the unknown foundation
on which the entire world depends.
Even so, when we investigate
whether something is real or not,
these final two definitions
are what we should have in mind.
________________________________
Jan Westerhoff is a philosopher
at the University of Durham
and the University of London's School
of Oriental and African Studies,
both in the UK, and author of
Reality: A very short introduction
(Oxford University Press, 2011)
• STANDARD MODEL OF PARTICLE PHYSICS
Reality: The bedrock of it all
New Scientist 01 October 2012
by Valerie Jamieson
Magazine issue 2884.
Can we explain reality purely in terms of matter and energy?
Is anything real?
The question seems to invite only one answer:
of course it is. If in doubt, try kicking a rock.
Leaving aside the question
of whether your senses can be trusted,
what are you actually kicking?
When it boils down to it, not a lot.
Science needs remarkably
few ingredients to account for a rock:
a handful of different particles,
the forces that govern their interactions,
plus some rules laid down by quantum mechanics.
This seems like a solid take on reality,
but it quickly starts to feel insubstantial.
If you take a rock apart,
you'll find that its basic constituent is atoms
- perhaps 1000 trillion trillion of them,
depending on the rock's size.
Atoms, of course,
are composed of smaller subatomic particles,
namely protons and neutrons
- themselves built of quarks - and electrons.
Otherwise, though,
atoms (and hence rocks)
are mostly empty space.
If an atom were scaled up
so that its nucleus
was the size of the Earth,
the distance to its closest electrons
would be 2.5 times the distance
between the Earth and the sun.
In between is nothing at all.
If so much of reality
is built on emptiness,
then what gives rocks
and other objects
their form and bulk?
Physics has no problem
answering this question: electrons.
Quantum rules dictate
that no two electrons
can occupy the same quantum state.
The upshot of this is that,
no matter how hard you try,
you cannot cram two atoms
together into the same space.
"Electrons do all the work
when it comes
to the structure of matter
we see all around us,"
says physicist Sean Carroll
at the California Institute of Technology in Pasadena.
That's not to say the nucleus is redundant.
Most of the mass of an atom
comes from protons and neutrons
and the force binding them together,
which is carried by particles called gluons.
And that, essentially, is that.
Electrons, quarks
(mostly of the up and down variety)
and gluons account for most
of the ordinary stuff around us.
But not all.
Other basic constituents of reality exist too
- 17 in total, which together comprise
the standard model of particle physics.
The model also accounts for the mirror world
of antimatter with a complementary set of antiparticles.
Some pieces of the standard model are commonplace,
such as photons of light and the various neutrinos
streaming through us from the sun and other sources.
Others, though, do not seem
to be part of everyday reality,
including the top and bottom quarks
and the heavy, electron-like tau particle.
"On the face of it, they don't play a role,"
says Paul Davies of Arizona State University in Templeton.
"Deep down, though, they may all link up."
That's because the standard model
is more than a roll call of particles.
Its foundations lie
in symmetry and group theory,
one example of the mysterious connections
between reality and mathematics
(see "Reality: Is everything made of numbers?").
The standard model is arguably
even stranger for what it doesn't include.
It has nothing to say
about the invisible dark matter
than seems to make up
most of the matter in the universe.
Nor does it account for dark energy.
These are serious omissions
when you consider that dark matter
and dark energy together comprise
about 96 per cent of the universe.
It is also totally unclear
how the standard model
relates to phenomena
that seem to be real,
such as time and gravity.
So the standard model
is at best a fuzzy approximation,
encompassing some, but not all,
of what seems to comprise physical reality,
plus bits and pieces that do not.
Most physicists would agree
that the standard model
is in serious need of an overhaul.
It may be the best model
we have of reality,
but it is far from the whole story.
________________________________
Valerie Jamieson
is New Scientist's features editor
• MATTER
Reality: Is matter real?
New Scientist 26 September 2012 by Jan Westerhoff
Magazine issue 2884.
It's relatively easy to demonstrate
what physical reality isn't.
It is much harder to work out what it is
Nothing seems more real
than the world of everyday objects,
but things are not as they seem.
A set of relatively simple experiments
reveals enormous holes is our
intuitive understanding of physical reality.
Trying to explain what goes on
leads to some very peculiar
and often highly surprising
theories of the world around us.
Here is a simple example.
Take an ordinary desk lamp,
a few pieces of cardboard
with holes of decreasing sizes,
and some sort of projection screen
such as a white wall.
If you put a piece of cardboard
between the lamp and the wall,
you will see a bright patch
where the light passes
through the hole in the cardboard.
If you now replace the cardboard
with pieces containing
smaller and smaller holes,
the patch too will diminish in size.
Once we get below a certain size, however,
the pattern on the wall changes
from a small dot to a series
of concentric dark and light rings,
rather like an archery target.
This is the "Airy pattern"
- a characteristic sign of a wave
being forced through a hole.
In itself, this is not very surprising.
After all, we know that light is a wave,
so it should display wave-like behaviour.
But now consider what happens
if we change the set-up of the experiment a bit.
Instead of a lamp, we use
a device that shoots out electrons,
like that found in old-fashioned TV sets;
instead of the wall, we use
a plate of glass coated with a phosphor
that lights up when an electron strikes it.
We can therefore use this screen
to track the places where the electrons hit.
The results are similar: with sufficiently
small holes we get an Airy pattern.
This now seems peculiar:
electrons are particles located
at precise points and cannot be split.
Yet they are behaving like waves
that can smear out across space, are divisible,
and merge into one another when they meet.
Perhaps it is not that strange after all.
Water consists of molecules,
yet it behaves like a wave.
The Airy pattern may just emerge
when enough particles come together,
whether they are water molecules or electrons.
A simple variant of the experiments
shows, however, that this cannot be right.
Suppose we reduce
the output of the electron gun
to one particle each minute.
The Airy pattern is gone,
and all we see
is a small flash every minute.
Let's leave this set-up to run for a while,
recording each small flash as it occurs.
Afterwards, we map the locations
of all the thousands of flashes.
Surprisingly, we do not end up
with a random arrangement of dots,
but with the Airy pattern again.
This result is extremely strange.
No individual electron
can know where all the earlier
and later electrons are going to hit,
so they cannot communicate
with each other to create the bullseye pattern.
Rather, each electron
must have travelled
like a wave through the hole
to produce the characteristic pattern,
then changed back into a particle
to produce the point on the screen.
This, of course, is the famous
wave-particle duality of quantum mechanics.
This strange behaviour is shared
by any sufficiently small piece of matter,
including electrons, neutrons, photons
and other elementary particles, but not just by these.
Similar effects have been observed
for objects that are large enough in principle
to be seen under a microscope, such as buckyballs.
In order to explain the peculiar behaviour of such objects,
physicists associate a wave function with each of them.
Despite the fact that these waves
have the usual properties of more familiar waves
such as sound or water waves, including amplitude
(how far up or down it deviates from the rest state),
phase (at what point in a cycle the wave is),
and interference (so that "up" and "down" phases
of waves meeting each other cancel out),
what they are waves in is not at all transparent.
Einstein aptly spoke of a "phantom field" as their medium.
For a wave in an ordinary medium such as water,
we can calculate its energy at any one point
by taking the square of its amplitude.
Wave functions, however, carry no energy.
Instead, the square of their amplitude
at any given point gives us the probability
of observing the particle if a detector
such as the phosphor-coated screen is placed there.
Clearly, the point where an object switches
from being a probability wave,
with its potential existence smeared out across space,
and becomes an actual, spatially localised object
is crucially important to understanding whether matter is real.
What exactly happens when the wave function collapses
- when among the countless possibilities where the particle
could be at any moment, one is chosen, while all the others are rejected?
First of all, we have to ask ourselves
when this choice is made.
In the example described above,
it seems to happen just before
the flash on the phosphor screen.
At this moment,
a measurement of the electron's position
was made by a piece of phosphor
glowing as the particle struck it,
so there must have been an electron there,
and not just a probability wave.
But assume we cannot be
in the lab to observe the experiment,
so we point a camera at the phosphor screen
and have the result sent via a satellite link
to a computer on our desktop.
In this case, the flash of light
emitted from the phosphor screen
has to travel to the camera recording it,
and the process is repeated: like the electrons,
light also travels as a wave and arrives as a particle.
What reason is there to believe
that the switch from probability wave
to particle actually occurred
on the phosphor screen, and not in the camera?
At first, it seemed as if the phosphor screen
was the measuring instrument,
and the electron was the thing being measured.
But now the measuring device is the camera
and the phosphor screen is part of what is measured.
Given that any physical object
transmitting the measurement
we can add on to this sequence
- the camera, the computer,
our eyes, our brain
- is made up of particles
with the same properties as the electron,
how can we determine any particular step
at which to place the cut between
what is measured and what is doing the measuring?
This ever-expanding chain
is called the von Neumann chain,
after the physicist and mathematician John von Neumann.
One of his Princeton University colleagues,
Eugene Wigner, made a suggestion
as to where to make the cut.
As we follow the von Neumann chain upwards,
the first entity we encounter that is not made up
in any straightforward fashion out of pieces of matter
is the consciousness of the observer.
We might therefore want to say
that when consciousness enters the picture,
the wave function collapses
and the probability wave turns into a particle.
The idea that consciousness
brings everyday reality into existence
is, of course, deeply strange; perhaps
it is little wonder that it is a minority viewpoint.
There is another way of interpreting
the measurement problem
that does not involve consciousness
- though it has peculiar ramifications of its own.
But for now let's explore
Wigner's idea in more depth.
If a conscious observer
does not collapse the wave function,
curious consequences follow.
As more and more objects
get sucked into the vortex
of von Neumann's chain
by changing from being
a measuring instrument
to being part of what is measured,
the "spread-out" structure
of the probability wave
becomes a property of these objects too.
The "superposed" nature of the electron
- its ability to be at various places at once -
now also affects the measuring instruments.
It has been verified experimentally
that not just the unobservably small,
but objects large enough
to be seen under a microscope,
such as a 60-micrometre-long metal strip,
can exhibit such superposition behaviour.
Of course, we can't look through a microscope
and see the metal strip being at two places at once,
as this would immediately collapse the wave function.
Yet it is clear that the indeterminacy
we found at the atomic level
can spread to the macro level.
Yet if we accept that the wave function must collapse
as soon as consciousness enters the measurement,
the consequences are even more curious.
If we decide to break off the chain at this point,
it follows that, according to one of our definitions
of reality, matter cannot be regarded as real.
If consciousness is required
to turn ghostly probability waves
into things that are more or less
like the objects we meet in everyday life,
how can we say that matter
is what would be there anyway,
whether or not human minds were around?
But perhaps this is a bit too hasty.
Even if we agree with the idea
that consciousness is required to break the chain,
all that follows is that the dynamic attributes
of matter such as position, momentum
and spin orientation are mind-dependent.
It does not follow that its static attributes,
including mass and charge, are dependent on in this.
The static attributes are there whether we look or not.
Nevertheless, we have to ask ourselves
whether redefining matter
as "a set of static attributes"
preserves enough of its content
to allow us to regard matter as real.
In a world without minds,
there would still be attributes
such as mass and charge,
but things would not be
at any particular location
or travel in any particular direction.
Such a world has virtually
nothing in common
with the world as it appears to us.
Werner Heisenberg observed that:
"the ontology of materialism
rested upon the illusion
that the kind of existence,
the direct 'actuality' of the world around us,
can be extrapolated into the atomic range.
This extrapolation, however,
is impossible... Atoms are not things."
It seems that the best
we are going to get at this point
is the claim that some things
are there independent of whether we,
as human observers, are there,
even though they
might have very little to do
with our ordinary understanding of matter.
Does our understanding
of the reality of matter
change if we choose
the other strong definition of reality
- not by what is there anyway,
but by what provides
the foundation for everything else
(see "Reality: The definition")?
In order to answer this question,
we have to look at the key
scientific notion of a reductive explanation.
Much of the power of scientific theories
derives from the insight that we can
use a theory that applies to a certain set
of objects to explain the behaviour
of a quite different set of objects.
We therefore don't need
a separate set of laws and principles
to explain the second set.
A good example
is the way in which theories
from physics and chemistry,
dealing with inanimate matter,
can be used to explain biological processes.
There is no need to postulate
a special physics or a special chemistry
to explain an organism's metabolism,
how it procreates, how its genetic information
is passed on, or how it ages and dies.
The behaviour of the cells
that make up the organism
can be accounted for
in terms of the nucleus,
mitochondria and other subcellular entities,
which can in turn be explained in terms
of chemical reactions
based on the behaviour of molecules
and the atoms that compose them.
For this reason,
explanations of biological processes
can be said to be reducible
to chemical and ultimately to physical ones.
If we pursue a reductive explanation
for the phenomena around us,
a first step is to reduce statements
about the medium-sized goods that surround us
- bricks, brains, bees, bills and bacteria -
to statements about fundamental material objects,
such as molecules.
We then realise
everything about these things
can be explained in terms
of their constituents, namely their atoms.
Atoms, of course,
have parts as well,
and we are now well on our way
through the realm
of ever smaller subatomic particles,
perhaps (if string theory is correct)
all the way down
to vibrating strings of pure energy.
So far we have not reached
the most fundamental objects.
In fact, there is not even an agreement
that there are any such objects.
Yet this is no reason to stop
our reductionist explanation here,
since we can always understand
the most basic physical objects
in terms of where they are in space and time.
Instead of talking about a certain particle
that exists at such-and-such a place
for such-and-such a period of time,
we can simply reduce this
to talk about a certain region in space
that is occupied between two different times.
We can go even more fundamental.
If we take an arbitrary fixed point in space,
and a stable unit of spatial distance,
we can specify any other point
in space by three coordinates.
These simply tell us
to go so many units up or down,
so many units left or right,
and so many units back or forth.
We can do the same with points in time.
We now have a way
of expressing points in space-time
as sets of four numbers, x, y, z and t,
where x, y, and z represent
the three spatial dimensions
and t the time dimension.
In this way, reality
can be boiled down to numbers.
And this opens the door
to something yet more fundamental.
Mathematicians have found
a way of reducing numbers
to something even more basic: sets.
To do this, they replace
the number 0 with the empty set,
the number 1 with the set
that contains just the empty set, and so on
(see "Reality: Is everything made of numbers?").
All the properties of numbers
also hold for all these ersatz numbers
made from sets.
It seems as if we have now reduced
all of the material world around us to an array of sets.
For this reason, it is important to know
what these mathematical objects called sets really are.
There are two views
of mathematical objects
that are important in this context.
First, there is the view
of them as "Platonic" objects.
This means that mathematical objects
are unlike all other objects we encounter.
They are not made of matter,
they do not exist in space or time,
do not change, cannot be created or destroyed,
and could not have failed to exist.
According to the Platonic understanding,
mathematical objects exist in a "third realm",
distinct from the world of matter, on the one hand,
and the world of mental entities, such as
perceptions, thoughts and feelings, on the other.
Second, we can
understand mathematical objects
as fundamentally mental in nature.
They are of the same kind as the other things
that pass through our mind:
thoughts and plans, concepts and ideas.
They are not wholly subjective;
other people can have
the very same mathematical object
in their minds as we have in ours,
so that when we both talk
about the Pythagorean theorem,
we are talking about the same thing.
Still, they do not exist
except in the minds in which they occur.
Either of these understandings leads to a curious result.
If the bottom level of the world consists of sets,
and if sets are not material
but are instead some Platonic entities,
material objects have completely disappeared
from view and cannot be real in the sense
of constituting a fundamental basis of all existence.
If we follow scientific reductionism all the way down,
we end up with stuff that certainly
does not look like tiny pebbles or billiard balls,
not even like strings vibrating in a multidimensional space,
but more like what pure mathematics deals with.
Of course, the Platonistic view of mathematical objects
is hardly uncontroversial, and many people
find it hard to get any clear idea of how objects
could exist outside of space and time.
But if we take mathematical objects
to be mental in nature,
we end up with an even stranger scenario.
The scientific reductionist sets out
to reduce the human mind
to the activity of the brain,
the brain to an assembly of interacting cells,
the cells to molecules, the molecules to atoms,
the atoms to subatomic particles,
the subatomic particles
to collections of space-time points,
the collections of space-time points
to sets of numbers,
and the sets of numbers to pure sets.
But at the very end of this reduction,
we now seem to loop right back
to where we came from: to the mental entities.
We encounter a similar curious loop
in the most influential way
of understanding quantum mechanics,
the Copenhagen interpretation.
Unlike Wigner's consciousness-based interpretation,
this does not assume the wave function collapses
when a conscious mind observes the outcome of some experiment.
Instead, it happens when the system to be measured
(the electron) interacts with the measuring device (the phosphor screen).
For this reason, it has to be assumed
that the phosphor screen
will not itself exhibit
the peculiar quantum behaviour
shown by the electron.
In the Copenhagen interpretation, then,
things and processes describable
in terms of familiar classical concepts
are the foundation of any physical interpretation.
And this is where the circularity comes in.
We analyse the everyday world
of medium-sized material things
in terms of smaller and smaller constituents
until we deal with parts that are so small
that quantum effects become relevant for describing them.
But when it comes to spelling out
what is really going on
when a wave function collapses
into an electron hitting a phosphor screen,
we don't ground our explanation
in some yet more minute micro-level structures;
we ground it in terms of readings
made by non-quantum material things.
What this means
is that instead of going further down,
we instead jump right back up to the level
of concrete phenomena of sensory perception,
namely measuring devices
such as phosphor screens and cameras.
Once more, we are in a situation
where we cannot say that the world
of quantum objects is fundamental.
Nor can we say that the world of measuring devices
is fundamental since these devices are themselves
nothing but large conglomerations of quantum objects.
We therefore have a circle of things
depending on each other, even though,
unlike in the previous case,
mental objects are no longer part of this circle.
As a result, neither the phosphor screen
nor the minute electron can be regarded as real
in any fundamental sense, since neither
constitutes a class of objects
that everything depends on.
What we thought
we should take to be
the most fundamental turns out
to involve essentially what
we regarded as the least fundamental.
In our search for foundations,
we have gone round in a circle, from the mind,
via various components of matter, back to the mind -
or, in the case of the Copenhagen interpretation,
from the macroscopic to the microscopic,
and then back to the macroscopic.
But this just means that nothing is fundamental,
in the same way there is no first or last stop
on London Underground's Circle Line.
The moral to draw from the reductionist scenario
seems to be that either what is fundamental
is not material, or that nothing at all is fundamental.
__________________________________________________
Jan Westerhoff is a philosopher at the University of Durham
and the University of London's School of Oriental and African Studies,
both in the UK, and author of
Reality: A very short introduction (Oxford University Press, 2011)
• MATHEMATICS
Reality: Is everything made of numbers?
New Scientist 26 September 2012 by Amanda Gefter
Magazine issue 2884
Dig deep enough into the fabric of reality
and you eventually hit a seam of pure mathematics
When Albert Einstein finally completed
his general theory of relativity in 1916,
he looked down at the equations
and discovered an unexpected message:
the universe is expanding.
Einstein didn't believe
the physical universe could shrink or grow,
so he ignored what the equations were telling him.
Thirteen years later, Edwin Hubble
found clear evidence of the universe's expansion.
Einstein had missed the opportunity to make
the most dramatic scientific prediction in history.
How did Einstein's equations
"know" that the universe
was expanding when he did not?
If mathematics
is nothing more than a language
we use to describe the world,
an invention of the human brain,
how can it possibly churn out
anything beyond what we put in?
"It is difficult to avoid the impression
that a miracle confronts us here,"
wrote physicist Eugene Wigner
in his classic 1960 paper
"The unreasonable effectiveness
of mathematics in the natural sciences"
(Communications on Pure
and Applied Mathematics, vol 13, p 1).
The prescience of mathematics
seems no less miraculous today.
At the Large Hadron Collider at CERN,
near Geneva, Switzerland, physicists recently
observed the fingerprints of a particle
that was arguably discovered 48 years ago
lurking in the equations of particle physics.
How is it possible that mathematics
"knows" about Higgs particles
or any other feature of physical reality?
"Maybe it's because math is reality,"
says physicist Brian Greene
of Columbia University, New York.
Perhaps if we dig deep enough,
we would find that physical objects
like tables and chairs are ultimately
not made of particles or strings, but of numbers.
"These are very difficult issues,"
says philosopher of science James Ladyman
of the University of Bristol, UK,
"but it might be less misleading
to say that the universe is made
of maths than to say it is made of matter."
Difficult indeed.
What does it mean
to say that the universe
is "made of mathematics"?
An obvious starting point
is to ask what mathematics is made of.
The late physicist John Wheeler
said that the "basis of all mathematics is 0 = 0".
All mathematical structures
can be derived from something
called "the empty set",
the set that contains no elements.
Say this set corresponds to zero;
you can then define the number 1
as the set that contains only the empty set,
2 as the set containing the sets
corresponding to 0 and 1, and so on.
Keep nesting the nothingness
like invisible Russian dolls
and eventually all of mathematics appears.
Mathematician Ian Stewart
of the University of Warwick, UK,
calls this "the dreadful secret of mathematics:
it's all based on nothing"
(New Scientist, 19 November 2011, p 44).
Reality may come down to mathematics,
but mathematics comes down to nothing at all.
That may be the ultimate clue to existence
- after all, a universe made of nothing
doesn't require an explanation.
Indeed, mathematical structures
don't seem to require a physical origin at all.
"A dodecahedron was never created,"
says Max Tegmark of the
Massachusetts Institute of Technology.
"To be created, something first
has to not exist in space or time and then exist."
A dodecahedron doesn't exist
in space or time at all, he says
- it exists independently of them.
"Space and time themselves
are contained within
larger mathematical structures," he adds.
These structures just exist;
they can't be created or destroyed.
That raises a big question:
why is the universe only made
of some of the available mathematics?
"There's a lot of math out there," Greene says.
"Today only a tiny sliver of
it has a realisation in the physical world.
Pull any math book off the shelf
and most of the equations in it
don't correspond to any
physical object or physical process."
It is true that seemingly arcane
and unphysical mathematics
does, sometimes, turn out
to correspond to the real world.
Imaginary numbers, for instance,
were once considered
totally deserving of their name,
but are now used to describe
the behaviour of elementary particles;
non-Euclidean geometry
eventually showed up as gravity.
Even so, these phenomena
represent a tiny slice
of all the mathematics out there.
Not so fast, says Tegmark.
"I believe that physical existence
and mathematical existence are the same,
so any structure that exists mathematically
is also real," he says.
So what about the mathematics
our universe doesn't use?
"Other mathematical structures
correspond to other universes," Tegmark says.
He calls this the "level 4 multiverse",
and it is far stranger than the multiverses
that cosmologists often discuss.
Their common-or-garden multiverses
are governed by the same basic
mathematical rules as our universe,
but Tegmark's level 4 multiverse
operates with completely different mathematics.
All of this sounds bizarre,
but the hypothesis that physical reality
is fundamentally mathematical has passed every test.
"If physics hits a roadblock
at which point it turns out
that it's impossible to proceed,
we might find that nature
can't be captured mathematically," Tegmark says.
"But it's really remarkable
that that hasn't happened.
Galileo said that the book of nature
was written in the language of mathematics
- and that was 400 years ago."
If reality isn't, at bottom,
mathematics, what is it?
"Maybe someday
we'll encounter an alien civilisation
and we'll show them
what we've discovered
about the universe," Greene says.
"They'll say, 'Ah, math. We tried that.
It only takes you so far. Here's the real thing.'
What would that be?
It's hard to imagine.
Our understanding
of fundamental reality
is at an early stage."
______________
Amanda Gefter is a writer
and New Scientist consultant
based in Boston, Massachusetts
• INFORMATION THEORY
Reality: A universe of information
New Scientist 26 September 2012
by Michael Brooks
Magazine issue 2884.
What we call reality might actually be the output
of a program running on a cosmos-sized quantum computer
Whatever kind of reality you think
you're living in, you're probably wrong.
The universe is a computer,
and everything that goes on in it
can be explained
in terms of information processing.
The connection
between reality and computing
may not be immediately obvious,
but strip away the layers
and that is exactly
what some researchers think we find.
We think of the world
as made up of particles
held together by forces, for instance,
but quantum theory tells us that t
hese are just a mess of fields
we can only properly describe
by invoking the mathematics of quantum physics.
That's where the computer comes in,
at least if you think of it in conceptual terms
as something that processes information
rather than as a boxy machine on your desk.
"Quantum physics is almost phrased
in terms of information processing,"
says Vlatko Vedral of the University of Oxford.
"It's suggestive that you will find
information processing at the root of everything."
Information certainly has a special place in quantum theory.
The famous uncertainty principle
- which states that you can't simultaneously
know the momentum and position of a particle -
comes down to information.
As does entanglement,
where quantum objects
share properties and exchange information
irrespective of the physical distance between them.
In fact, every process in the universe
can be reduced to interactions
between particles that produce binary answers:
yes or no, here or there, up or down.
That means nature,
at its most fundamental level,
is simply the flipping of binary digits
or bits, just like a computer.
The result of the myriad bit flips
is manifest in what we perceive
as the ongoing arrangement,
rearrangement and interaction of atoms
- in other words, reality.
According to Ed Fredkin
of the Massachusetts Institute of Technology,
if we could dig into this process
we would find that the universe
follows just one law,
a single information-processing rule
that is all you need to build a cosmos.
In Fredkin's view,
this would be some form
of "if - then" procedure;
the kind of rule used
in traditional computing
to manipulate the bits
held by transistors on a chip
and operate the logic gates,
but this time applied
to the bits of the universe.
Vedral and others think
it's a little more complex than that.
Because we can reduce everything in the universe
to entities that follow the laws of quantum physics,
the universe must be a quantum computer
rather than the classical type we are familiar with.
One of the attractions of this idea
is that it can supply an answer to the question
"why is there something rather than nothing?".
The randomness inherent
in quantum mechanics
means that quantum information
- and by extension, a universe -
can spontaneously come into being, Vedral says.
For all these theoretical ideas,
proving that the universe
is a quantum computer is a difficult task.
Even so, there is one observation
that supports the idea that the universe
is fundamentally composed of information.
In 2008, the GEO 600 gravitational wave detector
in Hannover, Germany, picked up an anomalous
signal suggesting that space-time is pixellated.
This is exactly what would be expected
in a "holographic" universe,
where 3D reality is actually a projection
of information encoded
on the two-dimensional surface
of the boundary of the universe
(New Scientist, 17 January 2009, p 24).
This bizarre idea arose
from an argument over black holes.
One of the fundamental tenets of physics
is that information cannot be destroyed,
but a black hole appears to violate this
by swallowing things that contain information
then gradually evaporating away.
What happens to that information
was the subject of a long debate
between Stephen Hawking
and several of his peers.
In the end, Hawking lost the debate,
conceding that the information
is imprinted on the event horizon
that defines the black hole's boundary
and escapes as the black hole evaporates.
This led theoretical physicists
Leonard Susskind and Gerard't Hooft
to propose that the entire universe
could also hold information at its boundary
- with the consequence that our reality
could be the projection of that information
into the space within the boundary.
If this conjecture is true, reality
is like the image of Princess Leia
projected by R2D2 in Star Wars: a hologram.
________________________
Michael Brooks is a writer
and New Scientist consultant based in Sussex, UK
• CONSCIOUSNESS
Reality: How does consciousness fit in?
New Scientist 26 September 2012 by Michael Brooks
Magazine issue 2884.
Some theories hold that reality
and consciousness are one and the same.
Is the universe really all inside your head
Descartes might
have been onto something
with "I think therefore I am",
but surely "I think therefore you are"
is going a bit far?
Not for some
of the brightest minds
of 20th-century physics
as they wrestled mightily
with the strange implications
of the quantum world.
According to prevailing wisdom,
a quantum particle
such as an electron or photon
can only be properly described
as a mathematical entity
known as a wave function.
Wave functions can exist
as "superpositions"
of many states at once.
A photon, for instance,
can circulate in two different directions
around an optical fibre;
or an electron can simultaneously
spin clockwise and anticlockwise
or be in two positions at once.
When any attempt is made to observe
these simultaneous existences, however,
something odd happens: we see only one.
How do many possibilities become one physical reality?
This is the central question in quantum mechanics,
and has spawned a plethora of proposals, or interpretations.
The most popular is the Copenhagen interpretation,
which says nothing is real until it is observed, or measured.
Observing a wave function causes the superposition to collapse.
However, Copenhagen says nothing
about what exactly constitutes an observation.
John von Neumann broke this silence
and suggested that observation
is the action of a conscious mind.
It's an idea also put forward by Max Planck,
the founder of quantum theory, who said in 1931,
"I regard consciousness as fundamental.
I regard matter as derivative from consciousness."
That argument relies on the view
that there is something
special about consciousness,
especially human consciousness.
Von Neumann argued that everything in the universe
that is subject to the laws of quantum physics
creates one vast quantum superposition.
But the conscious mind is somehow different.
It is thus able to select out
one of the quantum possibilities on offer,
making it real - to that mind, at least.
Henry Stapp of the Lawrence
Berkeley National Laboratory in California
is one of the few physicists that still subscribe to this notion:
we are "participating observers" whose minds
cause the collapse of superpositions, he says.
Before human consciousness appeared,
there existed a multiverse of potential universes, Stapp says.
The emergence of a conscious mind
in one of these potential universes, ours,
gives it a special status: reality.
There are many objectors.
One problem is that
many of the phenomena
involved are poorly understood.
"There's a big question in philosophy
about whether consciousness actually exists,"
says Matthew Donald, a philosopher
of physics at the University of Cambridge.
"When you add on quantum mechanics it all gets a bit confused."
Donald prefers an interpretation
that is arguably even more bizarre: "many minds".
This idea - related to the "many worlds"
interpretation of quantum theory,
which has each outcome of a quantum decision
happen in a different universe -
argues that an individual
observing a quantum system
sees all the many states,
but each in a different mind.
These minds all arise
from the physical substance of the brain,
and share a past and a future,
but cannot communicate
with each other about the present.
Though it sounds hard to swallow,
this and other approaches
to understanding the role of the mind
in our perception of reality
are all worthy of attention, Donald reckons.
"I take them very seriously," he says.
___________________
Michael Brooks is a consultant for New Scientist,
and author of The Secret Anarchy of Science (Profile/Overlook)
• EPISTEMOLOGY
Reality: How can we know it exists?
New Scientist 01 October 2012 by Mike Holderness
Magazine issue 2884.
Proving whether or not reality
is an illusion is surprisingly difficult
Philophers are not being rude
when they describe the approach
most of us take as naive realism.
After all, when they cross the street
on the way to work,
they tend to accept implicitly
- as we all do - that there is
an external reality that exists
independently of our observations of it.
But at work, they have to ask:
if there is, how can we know?
In other words,
the question "what exists?" reduces,
for what in philosophy
passes for practical purposes,
to questions such as
"what do we mean by 'know'?"
Plato had a go at it
2400 years ago,
defining "knowledge"
as "justified true belief".
But testing the justification
or the truth of beliefs
traces back to our perceptions,
and we know these can deceive us.
Two millennia later,
René Descartes decided to work out
what he was sure he knew.
Legend has it that he climbed
into a large stove to do so
in warmth and solitude.
He emerged declaring
that the only thing he knew
was that there was something
that was doubting everything.
The logical conclusion
of Descartes's doubt is solipsism,
the conviction that one's
own consciousness is all there is.
It's an idea that is difficult to refute.
Samuel Johnson's notoriously bluff riposte
to the questioning of the reality of objects
- "I refute it thus!", kicking a stone -
holds no philosophical water.
As Descartes pointed out a century earlier,
it is impossible to know we are not dreaming.
Nor has anyone
had much luck making sense of dualism
- the idea that mind and matter are distinct.
One response is that there is only matter,
making the mind an illusion
that arises from neurons doing their thing.
The opposite position is "panpsychism",
which attributes mental properties to all matter.
As the astrophysicist Arthur Eddington
expressed it in 1928:
"the stuff of the world is mind-stuff...
not altogether foreign
to the feelings in our consciousness".
Quite separately, rigorous logicians
such as Harvard's Willard Van Orman Quine
abandoned the search for a foundation of reality
and took "coherentist" positions.
Let go of the notion
of a pyramid of knowledge,
they argued: think instead
of a raft built out of our beliefs,
a seaweedy web
of statements about perceptions
and statements about statements,
not "grounded" in anything
but hanging together
and solid enough to set sail upon.
Or even, possibly, to be a universe.
This idea is circular, and it's cheating,
say critics of a more foundationist bent.
It leads back to the suspicion
that there actually is no reality
independent of our observations.
But if there is - how can we know?
_______________________
Mike Holderness is a writer based in London
• SIMULATION
Reality: The future
New Scientist 01 October 2012 by Richard Webb
Magazine issue 2884.
It’s possible
+we live in fundamental reality.
Future beings almost certainly won't
Before cursing the indolence of today's youth,
absorbed in the ever-more intricate virtual realities
of video games rather than scrumping
the ripe fruits of real reality outside, consider this.
Perhaps they are actually
immersing themselves in our future
- or even our present.
The story of our recent technological development
has been one of ever-increasing computational power.
At some future time we are unlikely
to be content with constructing
tightly circumscribed game worlds.
We will surely begin to simulate everything,
including the evolutionary history that led to where we are.
Flicking the switch on such a world simulation
could have fundamental ramifications
for our concept of reality,
according to philosopher Nick Bostrom
of the University of Oxford.
If we can do it, that makes
it likely it has been done before.
In fact, given the amount
of computing power
advanced civilisations
are likely to have at their fingertips,
it will probably have been done
a vast number of times.
So switching on our own simulation
will tell us that we are almost undoubtedly
in someone else's already.
"We would have to think
we are one of the simulated people,
rather than one of the rare,
exceptional non-simulated people," says Bostrom.
Probably, anyway.
There has to be a basement level
of reality somewhere, in which
the "master" simulation exists.
It is possible that we live in that reality.
Depending on its laws of physics,
the basement's computing resources
are likely to be finite.
And those resources must support
not only the master simulation,
but any simulations people
in that simulation decide to create
- perhaps limiting their number,
and thus increasing
the chances that ours is the base reality.
Either way,
our ability to check our own status,
and that of the fundamental
physical laws we discover, is limited.
If we are in the basement,
we have nowhere to drill down to,
and if we aren't, whether we can
depends on the rules put in place
by those who built the simulation.
So even if we do end up constructing
what could be reality for someone else,
we'll probably never know for sure
where we ourselves stand.
Who's to say video games are the lesser reality?
_____________________
Richard Webb
is a New Scientist feature editor
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