The Big Bang may be a black hole inside another universe
The
idea that we are living inside a black hole isn’t as crazy as it
sounds. Black holes warp space and time to the point where space and
time reverse roles. For anyone falling into a black hole, the radial
dimension, towards the singularity, becomes time and the time dimension
becomes like space.
The
two well known predictions from this are that, from inside a black hole
event horizon, (a) you cannot escape because the way out is back in
time and (b) you can see the entire universe’s future because time in
the universe you left is now like space. Too bad you can’t tell anyone
about it.
Another
prediction is that the infinitely compressed central singularity of the
black hole lies in your future as you fall in. When you reach it,
nobody knows what happens because the laws of physics as we know them
literally break down. Whatever the theory of quantum gravity ends up
being might explain it, but for now we have no idea.
The
basic idea for the Black Hole Big Bang Theory (BHBBT) is that matter
from a mother universe collapses into a black hole. The singularity of
this black hole is at a single point in space with respect to anyone in
the mother universe. But, because of the reversal of time and space for
anyone inside the daughter universe, that point in space r=0 become
their initial point in time, t=0. Hence, what was a singularity in space
is now a singularity in time, just like the Big Bang.
This
means that any matter falling in from the mother universe will
disappear from that universe and emerge at the initial t=0 point of the
daughter universe thoroughly scrambled.
Not
only that, but what emerges at the Big Bang is not just the matter that
was there at the black hole’s formation but all matter that ever
fell into it. That is because time at the black hole’s singularity is
essentially perpendicular to time in the mother universe outside.
The
reason why a whole other universe can be contained inside another one
has to do with the strange way in which time and space can be warped,
stretched, compressed, and twisted. What appeared to be a deadend at the
center of a black hole, can instead be a passage way into the birth of a
new universe.
You
can have many interconnected universes this way, in which mothers give
birth to daughters which give birth to more daughters, and so on ad
infinitum. Thus, far from being only 13.8 Bya (Billion years ago), the
whole interconnected cosmos can be infinitely old or more properly
timelike paths can be infinitely long into the past passing from
universe to universe.
This
is not the same as the Many Worlds Interpretation of quantum mechanics
that I have criticized in recent articles of course. There is no
constant splitting of universes based on quantum observations. Rather,
this is a process that occurs through black hole formation, and each
universe would be essentially unique, although daughter universes would
share characteristics of their mothers. There wouldn’t be exact copies
of you running around.
Indeed,
some have argued that a process of natural selection may take place
with these universes, since the only universes that can reproduce are
those that can form black holes. It is also a potential resolution of
the anthropic principle, the theory about why human beings exist, since
each universe may have slightly different laws of physics. Just as not
all planets can support life, not all universes can. No many worlds
interpretation required just many distinct universes within a single
spacetime.
The Standard Big Bang Model
The
Standard Big Bang (SBB) model of the universe is that the universe,
including time, space, and matter, came into being at a single point
13.8 Bya. From the standpoint of General Relativity, the theory of
gravity of Einstein, space itself was compressed into that point. As
time began, space began to expand carrying matter with it as it went.
This process is still going on and we know this because when we observe
distant galaxies, they are all moving away from us. More over, the
farther away a galaxy is, the faster away from us it is moving. That is
consistent with a theory of the universe where space is expanding. The
more space there is between two points the faster they can be moving
apart. The standard example of this is a set of dots on a balloon. Blow
up the balloon and all the dots move apart. The dots further apart from
each other move apart faster.
Where is the center of the universe?
The
center of the universe, where the Big Bang happened is, for us, not
anywhere in space, but at a point in time, t=0, at the Big Bang. The
balloon analogy is helpful here because the center of the balloon, of
course, is not on the balloon. Space, therefore, is like the surface of
the balloon with one additional dimension, so it is 3 dimensions instead
of 2. The past is like the interior.
Black
holes, on the other hand, have their centers at a point in space, r=0
in coordinates centered on the black hole singularity. Thus, they are
fundamentally different from the Big Bang singularity.
So how can we be inside a black hole?
One
of the odd features of general relativity is its ability to bend space
and time to the point where time and space can exchange places.
Formally, this is where the signature of the spacetime metric changes in General Relativity.
The
metric is what tells us how space and time behave and what distances
mean at any given point. Intense concentrations of matter can warp space
and time so that the metric changes what space and time mean for
different observers.
For
an observer outside a black hole, called the far observer, the
singularity is at a point in space. For the observer inside the event
horizon, however, the sign of the r and t elements of the spacetime
metric change places. Now, for the near observer, the singularity is at a
point in time, some time in the future.
The
BHBBT suggests that, at least for certain types of singularities, once
matter reaches it, it enters a new universe where time at the
singularity is the initial point of that universe.
To
visualize this, imagine you are an ant crawling on a table. As you
crawl along, you crawl down a slope. The slope gets steeper and steeper
until it is completely vertical from the direction you were crawling in.
Suddenly, it ends in a point. This is typical of how black holes are
portrayed. But now, instead of ending in that point, it expands out
again from the point, flaring into a cone. Through some miracle of
quantum mechanics, you pass through the point and emerge into the cone.
Now you are in a new universe perpendicular to the one you left.
Why is the BHBBT a good idea?
The
BHBBT resolves some problems with the Standard Big Bang model of the
formation of the universe. One of the problems with the SBB model is
that it doesn’t explain why the universe is so homogeneous. When we look
at pictures of the early universe by studying the Cosmic Microwave
Background (CMB), for example, the universe looks as if it has been
thoroughly mixed. This is sometimes called the horizon problem.
The Horizon Problem
The
horizon problem is a problem with causality. The region over which the
CMB is observed to be homogeneous is much larger than is possible for
ordinary causality which is limited by the speed of light. The most
popular solution to the problem is called the inflationary theory in
which space expanded exponentially, carrying light and matter along with
it so that everything got thoroughly mixed. You can think of it like
God’s blender.
Inflationary
theory doesn’t solve a number of other problems including the
fluctuation problem, super-Planck scale physics problem initial
singularity problem, or the cosmological constant. It doesn’t matter
exactly what all these mean. The point is that it is far from a panacea.
The
horizon problem is address by the BHBBT model simply by pointing out
that matter falling into the black hole has plenty of time to interact
with other matter falling in before reaching the singularity. While this
is not on the daughter universe’s clock yet, it is in that quasi-time
that exists within the black hole event horizon that is neither part of
the mother universe nor the daughter but is somewhere in between.
The Flatness Problem
A
second problem with the SBB is called the flatness problem. The
universe appears, as far as we can tell, completely flat, meaning that
its matter density is such that it is exactly the critical amount = 1 to
be neither hyperbolic < 1, meaning it will settle to a constant rate
of expansion, nor spherical, > 1, meaning it will eventually stop
and collapse in on itself. Thus, it will simply slow down as it expands
to zero velocity but never actually stop expanding.
Why
the universe has exactly the correct matter density to be flat, called
the critical density, is one problem. What that matter is is another: we
don’t know. The universe has three general types of matter: baryons,
which are what we think of as matter, dark matter, and a third form. We
call it dark energy and we have no idea what it is.
Dark matter, at least, we can observe in the rotations of galaxies and
other gravitational behavior. Dark energy we only see in the expansion
of the universe and to explain it we introduce a constant into
Einstein’s equations called the cosmological constant which makes the universe’s density even out to the critical density.
We
believe that if the critical density were not 1 then we would not be
here. If it were more than one, the universe would have collapsed long
ago, perhaps only an instant after the Big Bang, if it were less than
one, the universe would have expanded so rapidly that galaxies would not
have formed.
The
BHBBT resolves the flatness problem by connecting the black hole
interior to what is called a de Sitter space, which represents our
universe, with an infinite amount of time. Thus, the observer inside the
black hole approaches the singularity and emerges into de Sitter space
and continues on for infinite time into that space.
It
turns out that the only solution that allows a de Sitter space to
connect to a black hole is a flat one. Thus, dark energy isn’t a form of
matter energy but is actually the result of a spatial topology (shape)
inherited from the black hole.
Black Hole Information Paradox
One
final point is about the so-called black hole information paradox.
Simply stated this theory suggests that when quantum information, in the
form of states of quantum particles, falls into the black hole, it
disappears from the universe. In the BHBBT, it does not disappear, it
simply goes from the mother universe to the daughter universe.
Is it true?
Right
now, the current SBB is highly problematic but it only includes those
aspects that we can rigorously demonstrate with experiment and
observation. The BHBBT is a compelling theory that can be rigorously
formulated within the bounds of Einstein’s theory of General Relativity.
It doesn’t require new physics. It also explains why the Big Bang
happened at all. And I think it is compelling in many philosophical ways
such as the anthropic principle, it explains why we are here, but it is
far from being demonstrated empirically.
Pathria, R. K. “The universe as a black hole.” Nature 240.5379 (1972): 298–299.
V.P. Frolov, M.A. Markov and V.F. Mukhanov, “Through a black hole into a new universe?”,Phys. Lett.B 216(1989) 272.
Smolin, Lee. “Did the universe evolve?.” Classical and Quantum Gravity 9.1 (1992): 173.
Stuckey, W. M. “The observable universe inside a black hole.” American Journal of Physics 62.9 (1994): 788–795.
Easson, Damien A., and Robert H. Brandenberger. “Universe generation from black hole interiors.” Journal of High Energy Physics 2001.06 (2001): 024.
Written by
