the elusive theory of everything a
theory that could resolve the most
fundamental roadblock in our
understanding of how the universe
behaves and tie everything neatly up
with string it's been 50 years since
string theory was first proposed a new
quirk calls into question not only
essential parts of the theory itself but
also our working understanding of the
universe let's start at the beginning we
have two primary ways to describe how
all the stuff in our universe behaves
one big and one small
the first is Einstein's theory of
general relativity which tells us how
gravity interacts with space and time to
form the world around us that's the big
then there's the small the standard
model which works on the quantum level
this says that all matter is made up of
building blocks called elementary
particles you can break us down into
molecules then into atoms then into
subatomic particles like electrons
neutrons and protons and smaller still
are those elementary particles divided
into two broad categories quarks and
leptons of which there are different
kinds okay
groovy the standard model works
mathematically in most cases but it only
incorporates three of the four
fundamental forces of our universe
there's the strong the weak and the
electromagnetic forces and then there's
gravity gravity is the odd one out the
ugly duckling of the standard model
because it doesn't fit each of the other
three forces has a carrier particle
photons carry the electromagnetic force
gluons carry the strong force and W and
Z bosons carry the weak force but we
haven't discovered a carrier particle
for gravity which we would call the
graviton if we could find it
this means the mathematical calculations
of the standard model and those that
underpin Einstein's theory of general
relativity don't match up with each
other if we could find some way that
they could work together we'd have a
theory of everything it's this
misalignment and a desire for unity that
gave birth to string theory so how does
string theory tie our ideas of the
universe together instead of picturing
elementary particles as a distinct
points string theory posits that all
elementary particles can be pictured
more like a vibrating string each
particle is technically the same string
it's just vibrating
in a different way the way that a string
on a musical instrument can play
different notes including that elusive
note gravity okay that sounds pretty
tempting but of course there are issues
the level on which we would be able to
observe strings vibrating is way outside
our current capabilities famous string
theorist Brian Greene says we need to
build a particle collider the size of
the galaxies to be able to directly
observe strings in action so since
observation is off the table
well how about math the math tells us
something pretty freaky the equations
that make string theory work require
that the universe has at least ten
dimensions we're only able to observe
four of these the three dimensions of
space with time as a commonly proposed
fourth dimension the extra dimensions
required by string theory is where
parallel universes start to come into
play since strings are so small the math
tells us that they would not just be
vibrating in the large dimensions we
know of but in other tiny dimensions too
if we know the shape of those tiny
dimensions we might be able to predict
and then observe properties of
elementary particles like their charge
or their spin that would be attributed
to those extra dimensions which would
mean that we're seeing evidence of the
other dimensions but the problem with
that is that once scientists tried
plugging in different potential shapes
for these extra dimensions they found
that most of them worked the more they
tried the more of them fit which meant
that they had way too many possibilities
to consider and they lost hope that
finding out the shape of the dimensions
could help us observe their existence
until someone proposed that perhaps
there wasn't just one right shape for
each of the extra dimensions but they're
all right in each of their own universes
meaning there are other universes
potentially over 10 to the 500 others
each ever so slightly different from our
own and yeah I'm still talking about
theoretical physics not science fiction
although it's a pretty thin line if you
ask me that's where we all were up until
a few weeks ago when controversial new
mathematical papers may have blown all
of this apart and this big upset
involves dark energy we think we've
observed that our universe is slowly
expanding
our explanation for this is dark energy
and there's lots of theories about what
it is and how it behaves to make the
universe expand but we don't have
anything nailed down on that front just
yet
these recent papers provide new evidence
that the math of string theory may
actually prohibit the existence of
alternate universes in which dark energy
is stable which means one of a couple of
things either string theory is wrong or
we're wrong about our universe maybe it
didn't explode in a Big Bang it's not
expanding and it'll eventually contract
in what some physicists call a Big
Crunch or maybe there's an entirely new
way of fitting the existence of dark
energy into our string theory
calculations that no one has tried yet
now string theorists are still divided
about these new claims many are not at
all convinced of the papers claims and
think that the existing theories work
just fine so while there are no hard
answers this latest work has sparked a
renewed urgency to understand dark
energy how it behaves and how it might
inform our theories about the behavior
of our universe and the potential
existence of others still with us
we know string theory often presents
more questions than answers but we want
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check out this video here on quantum
retro causality thanks for watching I'm
Aaron