What is Reality
This is one of two interesting articles on Reality published in the New Scientist of February 1st. I (there is no I anyway) consider Reality to be an illusion created by people (sathva in general) .
What is reality? Why we
still don't understand the world's true nature
It’s
the ultimate scientific quest – to understand everything that there is. But the
closer we get, the further away it seems. Can we ever get to grips with the
true nature of reality?
Physics
29 January 2020
Pantherius/Getty
We
humans have a bit of a problem with reality. We experience it all the time, but
struggle to define it, let alone understand it.
It
seems so solid and yet, when we examine it closely, it melts away like a
mirage. We don’t know when it began, how big it is, where it came from and
where it is going, and we certainly have no clue why it exists.
Nonetheless,
the desire to understand reality seems part of our nature, and we have come a
long way. What was once explained in terms of divine creation is now in the
purview of science. Over the past 200 years or so, we have peeled back the
layers of reality, even if we are still not entirely sure what we have
revealed.
If
anything, the mystery has only deepened. We are now at a point where it is
equally credible to claim that reality is entirely dependent on subjective
experience, or entirely independent of it. Reality has never felt so unreal.
Lets
delve into the latest ideas about reality, from our own everyday experience to
the fundamental physics that seeks to describe the true nature of the cosmos.
The ideas can be dizzying, but there is no greater intellectual challenge than
trying to grasp the meaning of everything.
What is reality? Find
out from some of the biggest brains in science at our Instant Expert event in
London
What is reality anyway?
IT IS
a big and bewildering concept, reality. An abstract way of saying “everything
that there is”. That is a lot to take in: space, time, matter, energy, forces,
consciousness, even abstract ideas. How to even start?
Nobel-prizewinning
physicist Richard Feynman once described the quest to understand reality as a
bit like watching a game of chess without knowing the rules. By observing the
game, we slowly get to grips with what the pieces are and how they are allowed
to move and interact.
By
roughly the middle of the 20th century, physicists thought they had at least
identified the fundamentals of the game: particles and quantum fields. The
particles made up the matter and energy around us, and the quantum fields were
responsible for forces, like electromagnetism, which governed how they
interact. The rules of the game were set by quantum theory.
This
standard model has broadly stood the test of time. The discovery of its final
missing piece, the Higgs
boson, was confirmation that
it is at least on the right track.
And
it arguably fulfils at least one philosophical definition of reality: what
exists and what does it do? According to philosopher of science Tim Maudlin of New York
University, if you have answered
both these questions, then you have essentially cracked the problem of reality.
But
the standard model is nowhere near a complete answer. It leaves out many things
that physicists are pretty sure are real even if they have yet to be
characterised, including dark matter and dark energy. And it can’t account for
the force that substantially defines our experience of reality, gravity.
Despite high hopes that the Large Hadron Collider would follow
the discovery of the Higgs with at least some hints about a more complete theory, none has
yet been forthcoming.
It
isn’t that we don’t understand gravity. General relativity elegantly paints it
as a consequence of the deformation of the fabric of space-time. The problem is
that quantum theory and general relativity don’t play by the same rules. If one
is chess, the other is backgammon. Quantum theory is predicated on reality
existing in tiny, indivisible chunks, relativity on it being smooth and
continuous. This means we can’t understand situations where both gravity and
quantum theory are in play, such as in black holes, the big bang, or tiny
particles in gravitational fields.
The
most pressing challenge for the study of reality today, then, is to find a way
of unifying quantum theory and relativity in one game. “Each of these pieces is
contradicted by the other,” says Carlo
Rovelli at Aix-Marseille
University in France. “So what’s needed is more than sticking the pieces together.
We are searching for a coherent way of thinking in light of what we know.”
“If
you want a theory of everything where it all fits, I see no hint that we’re
close – zero”
There
are options on the table, not least the one Rovelli has pioneered, loop quantum
gravity, which holds that space-time isn’t smooth but made of tiny loops. There
is also the old stalwart, string theory. This says all particles and forces are
points on one-dimensional strings that extend through seven or more invisible
extra dimensions. Both loop quantum gravity and string theory purport to solve
some of the incompatibilities between explanations of gravity and quantum
effects, but both also have
their problems. String theory in
particular can lead to some pretty outlandish interpretations of reality, such
as multiverses (see “Is reality the same everywhere?”) and the “holographic
principle”, which holds that
three-dimensional space is actually a kind of projection onto a two-dimensional
surface.
Where to find answers?
A
more recent avenue being explored by theoretical physicists is entanglement, a quantum phenomenon whereby two particles can
influence one another even when they are separated by huge distances. This
approach has recently shown that entanglement can define the geometry of space:
the stronger the entanglement, the more warped space is. Some physicists
suggest this means that space-time emerges from quantum mechanics. In which
case, quantum theory is the more fundamental description of reality, and should
be where we find answers to the questions of what exists and what it does.
A
successful unification of quantum theory and relativity would still be
glaringly incomplete, however, unless it also straightens out another must-have
feature of reality: time. In general relativity, time is central. Quantum
theory near enough ignores it. Neither can provide an explanation for why time
always appears to tick in
one direction.
It
may be that time isn’t a fundamental ingredient of reality at all, but what
physicists call an emergent phenomenon. One way to think about this is to
imagine warming your hands by a fire. Energetic molecules in the air are
bouncing against your skin, warming it up. But we don’t need to explain what’s
happening in terms of the particles: a rise in temperature adequately captures
the phenomenon. Temperature is a perfectly good way of thinking about an aspect
of reality as long as we don’t assume that it is a fundamental thing. The same
may apply to time, says theoretical physicist Claudia de Rham of Imperial
College London.
This
way of thinking may even lead to an entirely different perspective on reality.
Perhaps the reductionist approach, of drilling down ever deeper to seek even
more fundamental layers, has hit a limit. Some physicists say we need to stop
fixating on the elusive “true” nature of reality and focus on building a set of
models that describe the various physical phenomena we observe.
“What
we do is modelling,” says de Rham. “Our way to interpret what’s going on
doesn’t necessarily need to be what in reality happens.”
One
seldom considered question, however, is how exactly models ought to seek to
explain reality. Some, such as general relativity, take some known quantities
about nature – the position of a planet, say – and predict what will happen
next. Quantum theory takes a different philosophical approach, assigning
probabilities to future outcomes we might see.
But
these aren’t the only methods of explaining reality. Consider a much older
branch of physics: thermodynamics, the science of heat, work and power. It
doesn’t seek to describe the fundamental nature of things, but instead rules
what can and cannot happen. For example, it tells us that a scrambled egg cannot
be unscrambled and that energy cannot
be created or destroyed.
Some
physicists are now exploring whether a similar approach can help us make
headway. For example, constructor
theory starts from the idea
that the essence of reality is information, and then sets out what kinds of
things are possible and impossible. It is early days, but it has already made
predictions in circumstances that defeat other theories, such as the behaviour
of quantum particles in a gravitational field.
The next level
Where
does that leave us? Our understanding of the game is in a state of flux, but we
are making progress, even if it isn’t exactly what we hoped for. “If the
question is, do we have a chance to see the next clear level of understanding,
then, yeah, I think we can get it,” says Rovelli. Even this is unlikely to be
the last word, however. Rovelli thinks it will just reveal more holes in our
understanding. “If you want a theory of everything where it all fits, I see no
hint that we’re close – zero,” he says.
It
isn’t even clear that our brains are actually capable of comprehending reality
(see “Can we
perceive reality?”).
Chimpanzees are intelligent but could never grasp quantum theory, or see why it
is necessary. Similarly, there may be some fundamental limit to human cognition
that prevents us from getting the big picture – though maybe superintelligent
machines could one day do so.
From
a human perspective, a more fundamental description of reality only promises to
shift the true nature of reality yet further from our everyday experiences of
it – quite a feat, given the extent to which quantum theory and relativity have
already done so. “When I wake up in the morning, for sure, that’s my reality,”
says de Rham. “But there is definitely something more fundamental that I will
never be able to experience.” For all our efforts to pin it down, reality just
keeps on getting bigger and more bewildering.
How did reality get started?
Even
though we don’t fully understand what reality is – and may never do so – that
doesn’t stop us from asking where it came from. It will come as no surprise
that answering this question is far from easy. Just ask the people whose day
job it is. They don’t agree on much, except that it is a tough gig. “We are in
a difficult situation,” says Daniele Oriti at the Max Planck Institute for
Gravitational Physics in Germany. “We are fishes in the pond and trying to
infer the situation of our pond.”
The
conventional origin story of the pond is the big
bang. In this account, the universe simply popped into existence out of nothingness
13.8 billion years ago, triggering an expansion that has continued without
pause ever since. It is a picture that aligns well with the available evidence
– such as the ongoing expansion of the universe – but hasn’t yet been
definitively accepted.
Perhaps
that is no surprise given the unfathomable core of the big bang theory: how
nothingness can give rise to an entire universe. Another major stumbling block
is the moment just after the universe popped into existence, when its entirety
would have been concentrated into a point of infinite density and temperature.
“We do not have any theory that describes the universe at ultra-high
temperatures and ultra-high densities,” says Anna Ijjas, also at the Max Planck
Institute for Gravitational Physics. That means our knowledge of these first
few instants remains fundamentally incomplete.
Better
theories might yet fill these gaps. Or they might render them obsolete by
showing that there was no beginning for space and time. That is the explanation
Ijjas favours. She says that our universe’s beginning coincided with a previous
universe’s end. Think of it as an hourglass, with two halves connected by an
incredibly narrow neck. In this model, the universe would once have had a
radius of 10-25 centimetres, more than a billion times smaller
than the radius of an electron. That is vanishingly small, but infinitely
bigger than the nothingness required for the big bang.
This
hourglass model is known as the big
bounce, and it has dramatic
consequences for reality. Because theoretical calculations dictate that the
preceding universe must have been similar to our own, its origin must also be
similar. That means it, too, would have begun from the collapse of a preceding
universe, and so on throughout eternity. “In our model, space-time never
vanishes,” says Ijjas. In other words, reality has always existed and there was
no beginning.
That
seems difficult to imagine. “It’s somewhat counter-intuitive,” concedes Ijjas.
But the alternative – the total absence of reality before space and time came
into existence – is more difficult. “It’s infinitely more difficult,” she says.
What came before?
Oriti
favours another alternative. For him, the big bang represents not the birth of
the universe, but the moment the universe assumed its current form, with
intelligible properties such as space and time. He compares it to a phase
transition such as the moment steam condenses to liquid water. “All sorts of
notions that you apply as a fish in the water simply do not apply to a gas,” he
says.
Before
this phase transition, notions of space and time are meaningless, and reality
itself becomes fundamentally indescribable. Even the word “before” is inaccurate, says
Oriti. “The notion of time ceases to apply.” What’s more, because all phase
transitions are, at least in theory, reversible, the universe could return to
this timeless state again at some point in the future, presumably with dire consequences
for us. If “future” is even the right word.
This
inability to talk about reality in everyday terms seems incredibly frustrating.
“We get frustrated as well,” says Oriti. “I sympathise, but get used to it.”
Reality, it seems, is truly beyond words.
Is reality the same everywhere?
TRAVEL
anywhere in the known universe and, like Coca-Cola, the laws of
nature always taste the same. That is a basic tenet of physics called the cosmological
principle, which holds that our patch of the universe is a representative
sample of the rest.
This,
as far as we can tell, is true. Certainly in the bits of the universe that we
can see, the laws of physics are “uncannily the same”, says Richard Bower at
Durham University in the UK. But an important caveat here is “the bits we can
see”. What about those we can’t?
There
are bits of the universe that are out of sight. Forever. These aren’t the
exotic parallel universes conjured up by string theory or quantum mechanics,
but an unavoidable consequence of workaday cosmology. Because the universe is
expanding at breakneck speed yet the speed of light is finite, the outer
reaches of the universe have disappeared over the cosmic horizon, forever out
of contact as light from them could never reach us. The known universe inside
the horizon stretches about 46 billion light years in all directions. How much
there is beyond that isn’t
known, but it is possible
that there are places beyond the horizon where the laws of physics are
different.
One
reason for thinking this may be true is that our laws are bizarrely and
arbitrarily conducive to life. Cosmologists call this fine-tuning. If any of
the laws of physics were slightly different, we couldn’t exist. As just one
example, if the strong nuclear force, which holds protons and neutrons together
inside atoms, were slightly stronger, the sun would have exploded long before
life got started on Earth. There are many other examples of fine-tuning,
collectively known as the “Goldilocks paradox” because so many of the laws are
just right. And paradoxical it is. “There’s no explanation for why they are the
value they are,” says Bower. “You’ve just got to go, ‘That’s the way it is’.”
The
odds of a universe with the exact specifications that can sustain life are so
low that many physicists argue that there must be other places where the laws
are different. It just so happens that we live in a life-friendly patch of
universe because, well, it couldn’t be any other way.
And
that’s just in our universe. There are almost certainly others. Multiverses are
a consequence of many theories, including black hole physics and string theory.
Not all produce different laws of physics, but some do. String theory, for
instance, conjures up 10500 universes, all with different laws of physics.
Could
we ever know if any of this is true? The reality is that other universes, if
they exist, are probably forever inaccessible to us. “Multiverse theories must
in principle be taken quite seriously, but proposals to test them don’t get
very far,” says Simon Friederich at the University of Groningen in the
Netherlands.
For
now, we have to study what we can see. But there is an upside to this: it makes
reality tractable. “If there is just one universe, then we might have a good
chance of discovering basically everything about physics,” says Tim Blackwell
at Goldsmiths, University of London. Unfortunately, that would be like assuming
you understood all of biodiversity by cataloguing life on a small island.
Reality may well be different elsewhere, but the cosmos is too big for us to
know for sure.
Join six expert speakers for a mind-melting trip through the
science of reality at our live event in London on 28 March newscientist.com/events
Magazine
issue 3267 , published 1 February 2020