Audio problems may be experienced during narration, the rest of the film should be fine. This is due to removal of soundtrack music.
you
In this series of films we interview some of the world's leading scientists to learn about their ideas for the origin of the big bang
It seems as a consensus that a quantum theory of gravity is needed and the most dominant approach is string theory
So we've come too soon to meet with Gabriele Veneziano
The father of string theory [and] one of the first to apply the idea to cosmology in order to answer the question
What happened before the Big bang?
But there's more than one approach to string cosmology we also spoke to alan Ira who works on string gas cosmology?
David [wong] who's reviewed Several string inspired models. I'm a recycle [aereo]
do who specializes [on] the interaction between Quantum Gravity theories and the early universe [a]
String theory, [I] suppose [add]
It fundamentally is the idea the concept that the fundamental building blocks of Nature and not point particles
but our extended objects loops or strings and
from that follows a
Very Rich sort of mathematical structure and in particular describing gravity and so string theory is provided as with
One of the candidates perhaps the best candidate for a quantum theory of gravity
Just as the different vibrational modes of guitar strings correspond to different musical notes
So different vibrational modes of fundamental strings give rise to both matter and Force carrying particles
In particular a closed string is shown to have properties of the long sought-after
Graviton this Implies string, theory can explain all particles and forces
unifying Quantum theory with general relativity
So what we believe is that if you take a theory of quantum gravity?
[then] you would be able to have some new kind of effects like
Discretization of your space time and [you] might therefore be able to understand what happens at what we call it as a big band
I
[was] looking into a
phenomena related to the strong interactions to the Nuclear Force [I]
Arrived at a at an equation at the formula which was supposed to describe
You know did
This interactions of these processes
It was only a Few years later that that
Formula was understood as describing the collision of strings
After it was sterilized that indeed there was a string behind these mathematical models
The theory was abandoned as such
because it didn't quite work in the details so between 74 and 84 very very few people were working on this theory until
the work of Greene and Schwartz
proves that this could be a consistent theory for
a bigger
scope which was the description of gravity and
it's quantization in fact as a description of all the
interactions including the strong interactions the problem that
the new Incarnation of string theory is supposed to solve is to reconcile or
allow to
Put together the theory of gravity
Given by General relativity and the Quantum mechanics Quantum
effects
Give infinities, which go out of control?
[now] the beauty of string theory is that not only it reconciles
Quantum mechanics and gravity
But it eliminates completely these infinities
Still it comes with its extra dimensions of space
so in order to reconcile this with our
perception of the 3 plus 1 dimensional world of the [three] dimensional space and one time
We have to imagine
although there are alternatives the simplest one is to imagine this extra dimensions are small and
Compact ok for instance think of a little sir
Okay, now [Tido] [ality] is
Tells us that strings behave very strangely
in the presence of compact dimensions in the sense that they cannot distinguish between
the certain compactification radius and
A dual one, that's why it's called duality
which is
Small if the original Circle was large then the dual circle will be small and vice versa in
Cosmology is a
quantity called the scale Factor of the Universe which tells you how
distances for instance of clusters of galaxies your
Changes changing time the scale Factor is a key cosmological parameter which represents the expansion of the universe and increases with time
The classical Big bang the scale Factor is [0] and values such [as] temperature density
pressure and Curvature become infinite
The expansion or the evolution of the universe can no longer be extended back in time and so the big bang singularity
becomes the absolute beginning, so what happens to the scale factor in string theory there is a
A
duality
similar to the one related
[to] the compactification radius for the scale Factor in other words
the
equations of string cosmology as opposed to
Einstein's Cosmology have this extra symmetry in which you can
Replace the scale Factor by its inverse there is another symmetry that this time string
Cosmology and [Einstein] cosmology share which is the inversion of time?
[ok] we know that you know we can run the expansion of the universe
[backwards] and we find a
contracting universe solution to the same equations and
now if you combine these two
symmetries scale Factor Duality and time reversal
You get a new cosmology which looks very [interesting] because it looks as if it wants to describe a universe
before the Big bang the idea of this
scale [Fatto] duality based
Cosmology is that
there had [been] an evolution of the universe which was some kind of mirror image of
What happened afterwards so in the same way as the post big bang, era? Where we live?
In our model will last forever, and I think [it] also lasts forever in ordinary
inflation [ok]
For us because of the symmetry this duality also the past is infinity ok and the future and the past are both
infinitely long and
The behavior of the scale Factor is of the inflationary type
So it seems
This was the the thing which thrilled me in the early 90s that
Naturally it seems as things here it leads
Thanks to this duality to some inflationary cosmology
There's the starting point from for the [Bharat] ik model was to think of
the Big Bang
occurring as a collision as a
Collision between our universe and really another universe in a higher dimensional space so a very dramatic
Sort of framework to think of this but
It was inspired by the idea of brains in
string theory [and] brains of these
extended objects not now just
strings not just loops of matter but
planes or hyper planes in Higher dimensional space at Neil turok Paul Steinhardt
[bert] over at and Collaborators
Took this seriously as a model for the big bang that you would really have a big bang would be a collision [in]
between brains and [that] collision would heat our universe and
indeed imprint
the structure in our universe would originate from the collision [of] the of these brains and
so that's a very fascinating idea and and they studied the the
Spectrum of perturbations that would happen, but again you have this this issue of a singularity
The hope was that in the high dimensional
theory you would be [able] to resolve as
What would just be a singular and apparent singularity and so the challenge is to do the calculation of the singularity?
in some
fundamentally
Richer theory of Gravity that might come
From from the string theory setting but that's very very difficult and very controversial as to how to do that calculation
One possibility to do this has been to mix the string inspired a [chaotic] model with loop quantum cosmology
Which is thought by some to remove the singularity?
string Gasps cosmology is based on the physics of
Closed strings and closed strings are responsible for for gravity unlike open strings in Standard
Cosmology, which is based on a general theory of relativity?
[if] you go backward in time the universe
Shrinks and becomes smaller and smaller until it hits a
The so called singularity point the curvature of space-time
becomes infinite the pressure becomes infinite
so there are so many infinities in this and in this system while the volume or the size of the universe is
observer, it's nothing so in in this string gas cosmology which is
based on the notion of
replacing a point particle which is completely completely a
Localized notion in physics by some extended object like a string [but] [by] you a few things
And one of them would [be] this the so-called
T-Duality some kind of symmetry between the physics of
large stuff and the physics of [small] stuff
So this symmetry between these two things will give you a cosmology
which would be the cosmology of the expanding universe would be the cosmology of the
Contracting [universe] and these two universes will be connected
[through] what is known as the self to all point the cosmology of expanding universe would be the same as the cosmology of
Contracting universe and since these two should exist side-By-side together
in order to
preserve this a t-Duality
You would not heat
any single arity because now the smallest size of the of the universe would be the size of a string so the universe at
Most can contract it can be shrunk to the size of string and that's the point we call it
The self to a point trains are winding around
space now our space should be compact and
Therefore we [use] a torus so strings are a winding around a torus shape
What happens this winding modes are?
changing to [so-called] Momentum modes the strings are
unwound then that's the end of the
String you phase or as you want to call it the ogaden phase
So what happens is [that] how we describe the production of this gravitational waves?
there would be some if you least you can assume is just like having a
bulge on your taurus on your tire
okay, and then this ball caused by the fluctuations on the windings winding modes of
strings and then this bulge
Rotates and
Propagates along the space which in this case space is like a torus
unwinding [A]
The strings will give you the expansion of the universe
This model says then the formed out universe
Starts with extra dimensions because [string] theory needs [axial] dimensions if you take Super string theory there [nine] plus [one]
Dimension if you take brains that are m-Theory ten plus one dimension
So it's a let let's start with a universe which is very small and is made out of nine or ten you name it special
dimensions and the Universe starts expanding
Now if [it] [start] expanding you have some mods
Which they are called winding mod which they have an energy which is proportional to the length of your toes?
Let's take that unit so then at some point it becomes
Energetically too expensive to keep expanding and the universe going to start contracting so as you go to smaller smaller play
Spaces they become energetic already expand, so the universe is going to go back and forth, so this was a way of
Explaining the initial similarity because we are never going to reach the zero because becomes too expensive it was a way to solve
The issue of dimensionality of space-time saying that at some point the universe goes through these oscillations
So the universe [result] the entropy of the universe is big
but
something
Happens that in a random kind of event and now three out of this nine or ten dimensions
They become bigger. They
compactify themselves and the till in string Theory its
String as it moves is one dimensional object
It moves in space-time
So it spans a two dimensional kind of brain and too much watching
So only if you have two plus two equal to four
only four dimensions you can have two strings that are going there words it key to each other and
Unwind and that's what you want in order to liberate the universal cosmic inflation works in any number of dimension and you can get still
scale Invariance
in any number of dimensions which is not the case here in
Strangest cosmology you can see it
nicely
that it only works in three spatial dimensions, and this is the feature of
Working with the strings because strings are extended object
There are two
Possible definitions on the big bang one is that its initial is
the beginning of time is a singularity beyond which you cannot go and so on and so forth and
The other which is really what is related to observations the first is a theoretical
Concept the second which is really [related] to observation is that the universe had to be hot?
very hot at some moment and
in the Standard
Inflationary scenario that moment comes after inflation not before inflation comes after invasion because inflation
By its exponential growth of the universe cools it down
practically to zero temperature it has to reheat the universe to a sufficiently high temperature so that
certain processes take place like
Big bang nucleosynthesis
producing helium you know and things like that cannot happen at low temperature, so ah
So what I?
Like to say is that the standard model of inflation is a pre big bang model
Because we shouldn't talk about
Just hypothetical singularities, which I?
Maintain they are really?
obtained by by using General relativity Beyond its limits of
applicability the expansion rate of the universe
was
almost constant
during
inflation
Which means that the the expansion was exponential in in our model it is not constant this
expansion rate actually grows in time, so
So on so this leads to different predictions and your inflationary
While it goes at a different rate your expansion rate yeah it still ends up with these same
Factors Flattened
flatness yes, I
but okay, [II] what it does not give automatically is a
scale-Invariant
spectrum of
perturbations
now
[in] fact for some time it looked that it could not give at all a flat spectrum of perturbations
then
For other reasons people in found the mechanism called the car battle mechanism
to which British
scientists contributed a lot by the way
once himself I think
and and through that mechanism
We found that actually sprinkled [Madhuri] can give a flat spectrum
Nearly scale-Invariant spectrum. We have been able to show that a
the most interesting and profound feature of cosmic inflation which was
explaining
the fluctuations in the universe the correct prediction of
existence of Mass fluctuations in the universe
We are able to also
To predict that but in our model. We have to admit that we [are] working
with the case that the universe started to being flat and
remains flat
Well inflation does a fantastic job to explain this and there is an ample of time here during this hackathon
Phase you have ample of time
to get rid of the magnetic Monopoles and
therefore
totally I agree with a
Palestine [hart's] recent paper that
[he's] claiming actually I you just need to have more time to get rid of these things
Many string theorists believe that there is a huge landscape of solutions to string theory which are populated by a multiverse thought to be
Generated by eternal inflation can the Pre Big bang model also generate a multi
the initial conditions look like a
chaotic Sea of Waves gravitational waves
Scalar waves [if] you want on select [a] magnetic waves and so on now these waves
would Collide interact and as the
Strength of the interactions grew because this was the solution
[eventually] they could
They could collapse
gravitationally and
And so by forming black holes in this
in this agitated sea, okay, and
each black hole would correspond eventually to a separate universe or
if you want the inside of a black [hole] is a
Cosmology the idea that a universe can be born from a black hole is most associated with loop theorist [Lee] [smolin]
However, there is no consensus in the loop community regarding [this] [fear]
Similarly it may not be the consensus position in the string community, but there have been well respected string theorists arguing
This is a reality and the latest edition of scientific American has a new incarnation of the idea on the front cover
the distribution of galaxies on the largest scales in our universe
reflects that the dynamics at even earlier times and and models like
inflation like the Pre Big bang like the egg periodic Model
[the] way we test those I think the best way we have currently to test. Those is is through the
predictions they make for the the distribution of
Matter on large scales in our universe, so one way to do this is to these very large-scale
Surveys high Redshift surveys of Galaxies in the universe today, so my my colleagues here in the university of Portsmouth
They are experts in map surveys of galaxies at high Redshift the day in the universe we see a faint
background Radiation the Cosmic microwave background radiation and
We've got a picture of the sort of patterns you can see
Here in that, this is from [the] Nasa's
W map satellite and at a very small level [that] of just one part and a hundred thousand you begin to see?
fluctuations in the [temperature] and those are fluctuations in the temperature [of] the Big bang and
We believe these fluctuations originated as same as quantum fluctuations at even earlier times
So we study the statistics of these fluctuations?
It reflects
density fluctuations
And it also has the possibility of reflecting
Not just the density field but also the gravitation the gravitational field in general and then and in particular that would include
gravitational waves
inflation or the pre big bang make distinctive predictions for the spectrum of
these gravitational waves, so
The pre Big bang all the at periodic models do produce gravitational waves primordial gravitational waves during these pre
Big bang phases, but because you're running towards a singularity
and the amplitude of the the gravitational metric fluctuations the gravitation waves are growing and growing as
The evolution progresses so that means corresponds to smaller and smaller cosmological scales
so
That means that on most of the gravitational waves are produced on a [small] scale
There's very little left on the large scale. There's a very low amplitude on the large scales, so it's hard to produce a significant
Cosmological background on the very large cosmological scales that are being probed by the bicep experiment
So that would be a real challenge for these pre big bang models. I think so that so the string gas cosmology
Claims to be able to produce an almost scale [invariant] spectrum, but do make the prediction that nonetheless. It should still [have] a slight rise
Towards smaller scales
and that's in that's a
distinctive prediction from inflation where
All the inflationary models have a decreasing energy density as as the universe expands and so
they end up with a
spectrum that decreases towards smaller scales that's called a red tilt because
Red because red has a long wavelength okay, so any any good I?
would say scientific theory should be falsifiable so that the analogy [that] I want to make here is just like having a
Analog radio and just you know
Turning your radio knob to higher or lower frequencies. So reactive means if you go to a
lower frequency should hear more noises what inflation and we predict for
fluctuations in Energy is
You will hear a little bit noisy if you go towards
Longer wavelengths and
shorter frequencies, so in that sense
there is no difference [between] our model and
Cosmic inflation, or I guess any alternative models and that has been tested if you get any model which predicts?
That there are some dependence on the scales [you] are already out. There is no
No room for you to play
but
The key feature I guess in our model or any other alternative models is what you predict for
the tensor fluctuations our tensor means fluctuations in
the Fabric of space
due to the gravitational waves in cosmic inflation predicts that uh
the same thing about
fluctuations in energy is true for
gravitational waves namely the gravitational waves also would be scaling [Barian] and
At best would have a tilt
Like a red tilt which was true for fluctuations in energy
So why our model our string gas cosmology model is kind of unique among any other?
String inspired models like the ik periodic model, or the Pre Big bang cosmology?
Is that the [predict] that not only the gravitational waves are produced at the beginning of the universe?
We predict a blue tilt which is unique to this model
In order to test the theory you
simplify your your initial model and one has [to] be very cautious because we don't know at the end of the story the
Predictions that you find how related are with the original model [you] had at the beginning?
So for instance if you were going to [found] that they are not there is no observation of any kind of tension
polarization and if there is no
observation of a relic gravitons that would be a positive thing for a periodic yunus
If you were going to find it state that there is no
observation of the tensile polarization
but the [rays] of the version of the relic gravitons that could be very good for the case of the
Pre Big bang model in the Standard Flashin we have the opposite of that you have
observation of the tensile polarization and non observation of any kind of relative gravity in March
2014 [by] [scepter]
meant at the South Pole Observing the Cosmic microwave background
[claimed] to find evidence of primordial gravity waves also known as [tensor] [noise] in the CMB polarization
What are these results mean if they are confirmed?
Certainly the simplest pre big bang model that we constructed would be incompatible
With the observation of gravitational [waves] from inflation
so with biceps
result
now of course as every theories we are seen looking whether you know we can modify or
you know x
Extend the model or play with some free parameters. We still we had in order to
To see whether we can get such a set such a spectrum of [tensile] perturbations
but ok it's not the most natural thing in any case, but if you think they are, right
So the good news is both inflation and our model predicts the existence of the gravitational dips
But the second thing which is still as an open question and if you look at the raw Data by them it's somehow
prefers a blue tilt over the red tilt of
Course the Bicep2 didn't say anything about the tilt of the power spectrum, and I think still
They didn't have that precision saying that we found the primordial gravitational waves to my mind is not enough
To say that the inflation the cosmic inflation is the winner of this
Race between these different models [all] what we are saying is [that]
Look for the tilt is great to find the primordial gravity on things
But look for the tilt the bicep2 claims will be bad news for both the pre Big bang model
and the [ecologic] model the good news for string gas cosmology [the]
[question] remains will the results hold up so it's a remarkable claim and
has been said you know remark extraordinary claims require extraordinary evidence and
That's fair enough. [that's] going to require a lot of
examination
In particular the questions that have [been] raised are
whether this signal which they saw could be due to
polarization of dust
foreground contamination
So it could be dust in our Galaxy
So it turns out the best information may well come from the planck satellite
It makes an all-sky survey and so as well as mapping
the cosmos at the Edge of the universe it's also mapping our Galaxy and
So they've got many free all sky coverage many frequencies
They should improve the models precise of these
dust [foregrounds]
And so we're now all waiting to see what comes out [from] the next release from the Planck collaboration
So I believe that dedicated
polarization
Experiments, which are going on in addition with extra analysis from the basic group and also the planck?
Data which are supposed to give us some new results. I believe by the beginning of next
Fall then we would be able in a more confident way to see if these results are correct
It's not necessarily going to be easy, but if the [amplitude] is as large as the bicep experiment report then
it
should be [possible]
By and and what we've got to do is is to
test that
gravitational wave spectrum across a range of scales, so
There are proposals for future satellite experiments
Which would give a more precise measurement of of the gravitational [wave] spectrum on the microwave background sky?
There are also the other way to go out go after it would be to look for
direct gravitational Wave Detection experiments and so
if
Which prober much very different length scales, so they're potentially looking for primordial gravitational waves
on
Really on the scale of the solar system for instance, so there are?
ambitious satellite proposals like the the [bigbang] observatory or the Desica experiment
many string inspired cosmologies point to the same conclusion
Seen in loop Quantum cosmology that [the] universe bounced from a previous collapsing space-time
Another theory Java [Lipschitz] Gravity also seems to make the same prediction
Why do these different models converge on the same answer any theory that has some kind of?
discrete space then by definition there you don't hit the
Singularity because I mean because you have this elementary volume that we are going to do to hit
So I
Mean the fundamental element which we have in line
Mystic Theories there is the string scam So I?
Don't know whether that could be an explanation of why all these these?
models
Somehow go to this bouncing solution one will arrive at the very small scale that can be
string scale on the one hand or can be
You know can be the discretization of your of your space
Kind of you know like causal dynamical translations of all
or
loop quantum gravity or whatever swell yeah, I think they came after us, but but
Indeed indeed we are in good company, [so] in lieu quantum gravity you only have the planck scale
And I guess so the bounce has to occur when the curvature is of clanky and scale order
Whereas in string Theory
There is this
different
Conceptually different scale which is the string
Length scale all of these things are related to the basic idea that you cannot trust
the classical Theory all the way to the singularity
now for us what comes first [a] string corrections for them are maybe different kind of
Quantum Gravity Correction
Infinity in the future doesn't scare us, I think
Even religions always talk [about] the beginning, but not [a] name
I mean, we know the theory in the infinite past and we can even construct the general solution of the equations, so
We don't see any any problem to extend these solutions all the way to infinity
I'm saying the beginning of time is a myth not in the sense that I can prove the opposite
But in the sense that I don't think you can prove the words beam of time, okay? It's a myth in that sense
It's true if you apply general relativity
all the way to till the singularity
But I think almost all
Physicists agree that before you reach the sink you write is something must come in. I don't know I I
think it's it's not very satisfactory to have a model with start and
certainly the
classical hot big bang cosmology beginning in a singularity
That is a prediction of if you follow the general relativity to its logical conclusion
there's there's a singularity there at the start but but I think
Most physicists look at that and think well
That's just the theory telling us that the theory breaks down a singularity is that the theory is broken down I?
think there must be
some
Consistent description of all parts of our universe I find it very unlikely that there's a an edge either in space
That we'd fall off the edge of space or that we should fall off the edge of time in that way back at the beginning
of time, so I would think that there is a continuation a
smooth description
Whether or not that means time is infinite?
Is another question because we know that space doesn't have to be in you know [just] you can have oh
Here's a nice spacial surface. Which is more or less smooth?
And finite, but it doesn't have an age and so you know we could have some
smooth Topology for space-time in that way
But or it could be smooth and extends forever
and we may never know the answer to that question and
I'm sure we will keep trying to push back further and further to learn more about
The early universe and what happened before the early universe
We see we see these these funny hot and cold spots
Red and blue blotches on the sphere of the Cosmic microwave background [as] a singularity you've got no physical description for why?
Some places are hotter in some places in colder and yet overall it's almost uniform and all these
pre Big bang models are trying to give us a
A theory in which we can make that calculations. I think that is an open question. I mean there is this
you know
work
Very various people like [vilenkin] [as] you said before who has who studied the possibility that the universe
could not have a beginning and
He studied three different cases of universe. I mean of
Scenarios he took eternal deflation because we know that
inflation is
Eternal in the future, so the question is is it [a] tunnel in the past?
now
then he
Studied the cyclic model the entropy increases
the only thing that you can allow that to happen if the volume increases
so then its density which we measured remains constant, but if then its density remains constant
Then we know that the average
expansion rate is positive and
If that is the case then we know that this theory [there's] a theorem that says that this kind of theories that have
They are genetically incomplete in the past which means that they [cannot] go to the past infinity
So they have a kind of beginning
And that's not the case that this theory is trying to say that we don't have this beginning
So this is a problem, and I don't know how this could be resolved
nevertheless
Given that we do not know the full theory of quantum gravity
[I] don't think that we can definitely say this is right, or this is wrong
and then he studied an
emergent scenario, which I believe is called the cosmic egg as well, but you started with a universe which [is] static and
then
something happened at the
The thing is going to to start expanding
So I
for the three cases
He [has] so that
You cannot avoid the initial
The beginning you might say that all these
Questions have been addressed
Not in the context of a full
Quantum Gravity Theory
and
It might be that everything
we know my chance if you go to a full quantum gravity field [I] guess at least in the frame [of] framework of
string theory whether you believe in the pre big bang cosmology whether you believe in the egg periodIC Universe or
Extremely gas cosmology there was no beginning for the universe. I'm sure there was something
well, you are passing through the self to [all] point or the collision of the [two] brains for the egg periodIC Universe which [mimicked] this
The so-called big bang, but to me it is hard for me to
Comprehend it. Let's say this way that there was nothing and then [suddenly] the universe
Came about recently alan guth also
saying that he thinks that there was
no, beginning for the universe the universe was past eternal as well, so I am
If I want to bet I want to bid for a universe which had no no clear-cut
Beginning, there's to be no clear agreement on whether the universe had a beginning
Cosmologists such as the Lincoln [Mitani] argue that [there] most likely was a beginning
[whereas] many quantum cosmologists side with alan guth [whose] recently suggested that there may be no such beginning so is there any
Possibility of actually settling this dispute with observations at a listicle [is] [picking]
I don't see how the observations are going to give us any kind of
you know
Fingerprint about about that. I don't exclude but up to what we have right now
I don't [believe] [that] they can give us any kind of data. We have we analyze them within a particular
Scheme of a theory and if we do not have the full quantum gravity theory, I'm not sure how we can
What do we look for a number [of] problems have been associated with [the] collapsing universe?
Namely the instability is associated with a knife attribute and the increase of entropy. How can these be resolved the anisotropy is
washed out during this
what we call the string phase in which you avoid the singularity that the entropy that you produce at the
bounds
is
Saturate
Saturates a certain bound on entropy
Which is sometimes called the hubble bound it is not that they of course that the entropy?
Decreases that something strange is that the bound itself?
gets relaxed as
the universe goes from the
Contracting phase to the expanding phase is not a surprise [that] they bound in the contracting phase they bounce tends to become tougher and tougher
until [it] [gets] saturated
But at that point precisely around that point you bounce
Once you bounce you start to Expand and then they bounce relaxes then it goes up
the Entropy also goes [up] by the second law of
thermodynamics, but not as much as the bound so there is a lot of room for
interpreters today
Pound is huge
Relative to what we know is the entropy of the universe today, so I?
think it's a very interesting question, but I don't think is as bad as
For instance is presented in penrose book that you know
the Entropy had to be
particularly low at
The [dabangg] I had a bank
While string theory loop quantum gravity and her Java [Lifshitz] gravity all of the news to inspire bouncing
Cosmologies and are probably the prime candidates for a theory of Quantum gravity
Wikipedia currently lists more than a dozen other candidate theories can they be used to try and understand the early universe
[I] don't think that this these models. They are
Developed to an extent that they can
Answer this I mean this kind of question cousin sets is easy
It's a very nice and dutiful the kind of scenario
[just] takes you know the basic idea of causality
But I think that it's so minimalistic. That is very
Difficult to make go Beyond and make some kind of you know claims about the origin of the universe and things like that I
also, because in these models
If you don't take that much into account the matter so I do not think that these models can
Make at least at this stage and kind of claim about
The face before the Big [bang] or the face of the big planets
String theory has been widely cited the best candidate for a unified theory [of] physics, but in recent years
There's been a backlash arguing that it cannot be experimentally tested now in this film
We've reviewed three different string inspired [cosmology] and there are several others the great hope for these models
Is that they can freak string theory in contact with observations?
It must be tested if it's to be accepted and perhaps cosmology can provide a way for this
If it can perhaps string theory can tell us, what happened before the big bang?
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