E
ven 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 vanishinglythe 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?”, page 39). 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.
Joshua HowgegoHOW DID REALITY
GET STARTED?>1 February 2020 | New Scientist | 37