In the same manner that the joy that the flavor
of McDonald’s Szechuan Sauce brings food
lovers set them on adventure to find it’s
secret recipe, scientists are also looking
for the recipe that can tell us how the universe
really works that can be as simple as elegant
as a single equation.
Today, let’s go on an adventure to explore
one of the top candidates that may finally
describe everything in one mathematical expression,
string theory.
String theory is definitely one of the most
popular theories in Physics that are widely
overused in pop culture today.
I think everybody would agree that the most
popular example of this is the CBS show The
Big Bang Theory.
It is impossible to miss hearing about it
in a lot of episodes, since it’s what Sheldon
Cooper, one of the main protagonists of the
show, is dedicating all of his energy on.
A lot of the popular names of scientific communicators
nowadays definitely have talked about this
at some point, like Neil de Grasse Tyson,
Bill Nye, the two Brians, Brian Cox and Brian
Greene.
All of which are names that are looked up
to in the scientific community.
And we can’t blame him since this is really
remarkably one of the most controversial and
daring theories of physics in the current
date.
Are you not sold yet as to how extremely important
this theory is?
Okay, sure.
Let me tell you a bit more.
According to Dr. Michio Kaku, a well-known
popularizer of science and highly revered
theoretical physicist, string theory can answer
a lot of questions about our very own universe:
what events occurred at the edge of time and
space, precisely “before” the Big Bang,
what exactly can we expect inside a black
hole, and even the possibility of travelling
instantly in space up to parallel universes
through what we call wormholes.
I think you can imagine how much of the current
trends of sci-fi proliferated because of these
ideas existing.
Honestly, if this doesn’t get you extremely
excited about this topic, I don’t know what
will.
But assuming you already are interested, let’s
take a deep dive on what exactly this theory
is, shall we?
Or at least let’s try to accomplish that,
since even the scientists who study this theory
are also still struggling to fully understand
every aspect of it..
The story of string theory began when physicists
desired for the most simplified explanation
for everything in the universe.
These scientists always have this thing of
wanting to compress explanations into something
as neat and as simple as possible.
Specifically, they were aiming to find a single
line of equation which can be used to describe
every phenomena in the universe: how a bird
flies in the sky, how planetary motion comes
about, how electricity works…
It would certainly be something astonishing
if only we could describe this into one line
of Math, doesn’t it?
Back in the early days of modern physics,
there were five fundamental forces of nature
were known: electricity, caused by the motion
of electrons; magnetism, which describes an
innate physical phenomena of objects; the
weak nuclear force, responsible for nuclear
decay; the strong nuclear force, or the force
holding together the nucleons in an atom,
keeping them from breaking apart due to the
repulsive force of the electrostatic force.
The earliest success at unifying these forces
was done by James Clerk Maxwell, when he laid
down the equations that define the interrelationship
between electricity and magnetism.
According to his study, an electrical current
can induce magnetism, and vice versa.
The resulting theory was called electromagnetism.
Fast forward to the early 20th century and
the quest takes us to the two of the most
well-known theories in physics nowadays: the
theory of general relativity, which best describes
the extremely large and massive; and quantum
mechanics, describing the extremely light
and small.
Both of which had some, if not most involvement
by physics superstar, Albert Einstein, by
the way.
Quantum mechanics reveals that every particle
has a dual nature: everything has both a wave-like
and a particle-like property.
However, this is not completely pretty, as
in this approach, the best we can come up
with are probability expressions of particles.
But it does accomplish the task of describing
subatomic particles and how they interact
with the highest accuracy, despite this incapacity.
But before you label this theory as bananas,
it is important to know that it is not entirely
the scientists fault.
What quantum mechanics also reveals is that
when we try to observe particles in the quantum
scale, this observation has a consequential
effect.
You might be thinking “how did we come to
that?
I thought we were doing so well?”
Well, as finite beings, we are limited by
our own means of observation.
For us to actually observe something, we have
to experience it.
Usually, this experience entails seeing things
and recording what we see.
A pretty easy task, right?
Well, at some point, it stops being as simple
as that.
Take note that to be able to see stuff, we
need to have a light wave hit it, and then
have the light wave bounce and our eyes, at
which point our brains interpret the information.
When we are talking about subatomic particles,
these objects can get so small that effectively,
visible light won’t be able to “bounce”
on it so that we can effectively make an observation.
So let’s use a light with shorter wavelength,
right?
Not entirely.
Using this configuration results in an extremely
high-amount of energy that would affect the
position of the particle.
In a more compact terminology, this is known
as the Heisenberg uncertainty principle, which
states that we can never accurately have information
about both how fast an object is going and
where exactly it is located at a certain time.
This is what we state earlier that in the
quantum realm, the observer also affects what
he observes.
Are you still keeping up?
I know this is getting extremely tedious,
but I promise you this is going to get more
interesting, so please bear with me.
Now, let’s discuss what’s on the other
end of the spectrum, Einstein’s general
relativity.
Back in the days of classical mechanics, Newton
described gravity as some sort of “non-contact
force”, essentially a force affecting objects
without actually being in contact, or as he
puts it “an action at a distance”.
This is extremely controversial, since the
current understanding at that time was that
for energy to be transferred, to objects has
to directly come into contact.
But the math works, and upon observation,
this also works, so, it held up as a theory.
After 200 years, this theory was all good
until then came Albert Einstein, changing
everything from the ground up, and claiming
a different take on it.
In Einstein’s revision of the gravitational
theory, which he labelled as general relativity,
he completely revised the claim that gravity
is a non-contact force, and addressed the
problem in a different perspective.
In his theory, he stated that we are looking
at space all wrong.
The problem is that we are assuming time to
be the most constant quantity in the universe,
which as he described in quantum mechanics,
is not.
Instead of having just space, he claimed that
space and time is a single membrane at which
everything is bound to.
So if that’s the case.
What exactly is gravity?
To help you imagine, say for instance that
you stretch out a fabric, and then you put
something heavy in the middle, like a bowling
ball.
If you add marbles to it, which are way less
massive, then you expect the marbles to swirl
towards the center.
Relating this to gravity, the mass of heavy
objects in space-time causes it to effectively
become distorted.
This is what we experience as gravity.
If we take our Solar System to our analogy,
the Sun is the bowling ball, and the planets
are the marbles, spiraling about.
This solves the non-contact conflict, and
physics is bound again by its original laws
of order.
Now, we have two great theories that define
their respective realms with great precision:
for the cosmological, we have general relativity.
For the subatomic, we have quantum mechanics.
This is where the problem begins.
Quantum mechanics works with probabilities,
while general relativity works with definite
stuff.
If the goal was to unify the forces, this
is certainly not helping.
So how did physicists approach this problem?
One idea they thought was “maybe if we can
know what the most fundamental component of
nature is, we can find out how to unite these
forces.”
So, in the 1900’s, this is what they did.
They smash protons together and find out that
they are indeed composed of much smaller particles
which they called quarks.
Some quarks are responsible for the characteristics
of matter, such as mass, charge, and angular
momentum, while some are responsible for the
forces.
This theory unified the electromagnetic and
weak force into the electroweak theory.
Apparently, forces are merely somehow a particle
exchange, to oversimplify it.
This is more popularly known as the quantum
field theory, eventually giving rise to the
standard model.
If this is the case, then particle exchange
still needs a place to operate.
If it needs a place to operate, that interprets
to spacetime, and as described by Einstein,
if we were to assume spacetime to be non-dynamic,
that is to say, you can’t change its features,
then we’re going to be stuck in a loop!
We won’t be able to unite the two theories!
One testament to how important this unification
is is what it will tell us about the beginning
of the universe.
General relativity is great at describing
the extremely large and massive, while quantum
mechanics, the extremely small and lightweight.
At the temporal edge, or for lack of a better
terminology, at the “beginning” of the
universe, everything was so dense, that is
to say extremely small but extremely massive.
Literally everything in this universe is at
one single point in space.
Talk about a crowded space!
In cosmology, astronomers take a stab at this
problem by studying black holes, since these
celestial objects are extremely massive and
small.
It’s not exactly like the Big Bang, but
this is as close as we can get to it, and
this is generally how we identify objects.
We study something that has similar attributes,
and relate the information we get.
However, I bet you can guess that this is
not everything in the story.
Now, enter Theodor Kaluza, who dared to think
in a similar and daring way as Einstein did.
He thought, if we can describe gravitational
force as a distortion of space time, can’t
we think of the same for electromagnetism
and the other forces?
Maybe they are also distortions of components
much more fundamental than quarks?
Lo and behold, a working theory was made.
Upon further investigation, the more fundamental
components of the universe apparently behave
in a similar manner, precisely, as curves
and bumps in a field of membrane, similar
to, you’ve guessed it, strings.
This is where string theory rose to popularity.
A more concise description by string theory
is that the forces, the characteristics of
objects such as mass, charge, and spin, and
energy are all manifestations of vibrations
of tiny strings of energy.
To put it in perspective, it is similar to
how changing the tension in a string of a
guitar, for instance, produces a different
note, and a combination of notes produce a
different chord.
However, as astounding as this sounds, this
theory has consequences.
For string theory to be an accurate description
of the fundamental forces of nature, it has
to have dimensions which are more than what
we currently observe.
In fact, in it’s latest variation, the M-theory,
the strings have to have 11 dimensions in
which they can freely vary, and vibrations
in these dimensions manifest as the forces
or the characteristics of matter.
Now, don’t think of these dimensions as
what pop culture perceives it to be, like
dimensions as in travelling to a completely
different universe.
That also uses “dimensions” but in a different
context.
I have to stress this to not get you over
excited and think of an actual different universal
dimension that we don’t know of.
Although in the deeper sense, it is actually
the case.
But let’s move on.
But, okay, in the context that we are in,
where are these dimensions?
How do we know these exist?
Well, the simplest way to imagine these dimensions
is looking at a power cable hanging on an
electrical post.
If we are far away, we interpret these cables
as one line, or one dimension.
However, as we move in closer, we will see
that the cable is actually cylindrical, with
three more dimensions of length, thickness
and height.
Is that all crazy for you yet?
Now, string theory is purely theoretical and
mathematical in nature.
In the old days of physics, the common dogma
was that experimentation was performed first
before theory.
As scientists enter the modern age, the approach
was now converted to mostly performing the
theoretical foundation first before experimentation.
This places us to the next question: string
theory is mathematically consistent and is
theoretically sound, but how do we actually
test it?
This is the great challenge of string theory
nowadays.
There is a smorgasbord of approaches that
scientists come up with to determine the existence
of strings and extra dimensions.
According to a TED Talk by Brian Greene, respected
physicist in the field of string theory, one
way to test the existence of extra dimensions
is by colliding particles in the LHC.
But how exactly?
When two particles collide, the resulting
debris flies off everywhere, and a certain
energy change is measurable.
By conservation laws, we expect the difference
of the energies before and after the collision
to be the same.
However, if by some strange reason it doesn’t
this could possibly account for the extra
dimensions that we are looking for.
As interesting as it sounds, up to this day,
there hasn’t been a test devised to prove
the existence of strings.
The circumstances for the strings to be definitely
observed are just way too extreme for our
current technology.
However, it is not also falsifiable, as the
mathematics work.
But that just gives us something to look forward
to, doesn’t it?
As we end this video, we leave the question
to you, our dear viewers: what’s your impression
of string theory?
Do you think it’s accurate?
Do you think our scientists should spend their
energies proving this or should they move
to a different theory?
Let us know in the comment section below!
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Stay insanely curious!
