You may have heard the theory that it’s
possible there are multiple universes where you exist in each one, but live a different
life, and make different decisions resulting in a totally different outcome in each universe. We know this as the multiverse. But where did the idea for multiple universes
come from? Today we’re going to confront the idea of
the existence of a multiverse as recent discoveries in physics and astronomy could point to their
existence. Have we finally found evidence for a parallel
universe, or is it something stranger we cannot comprehend? The universe that we know and exist in all
began with the Big Bang which expanded faster than the speed of light in a growth spurt
called ‘Inflation’. And for as long as there has been a universe,
space has been expanding ever since it came into existence 13.8 billion years ago...and
it continues to expand. As far as we know, our universe is a single
expanding blob of spacetime speckled with trillions of galaxies that now stretches 93
billion light years from edge to edge. But beyond this limit, there are things we
cannot see, that could be something more, or just an infinite expanse of nothingness. Our universe might be really, really big - but
also finite, or it could be infinitely big. Both of these things are possibilities. However, if the universe is infinitely big,
there are only so many ways that matter can arrange itself within that universe, and eventually,
matter has to repeat and arrange itself in similar ways. If the universe is without an end, then it
just might be home to parallel universes. If that sounds confusing, think of a deck
of cards. If you shuffle the deck, there are only so
many orderings that can happen, and if you shuffle it enough times, the order of cards
has to repeat. With an infinite universe and only a finite
number of complexions of matter, the way matter arranges itself will also have to repeat. That said, if a multiverse does exist, there
would also be infinite versions of you. Other alternate versions of you might be doing
the same thing you’re doing right now, but some might be wearing different clothes, and
probably made vastly different career and life choices. You might drive a Ford Fiesta in one world,
but drive a Ferrari in another. But how could this be possible? Because the observable universe extends only
as far as light has traveled in 13.7 billion years since the Big Bang, the space-time beyond
this distance can be considered to be its own separate universe. And if this is true, then there would be a
multitude of universes existing next to each other in a giant patchwork of universes. Although the idea of parallel universes or
a ‘multiverse’ remains a mystery with some calling the idea pure science fiction,
it’s still one of the biggest debates between experts with some believing they exist, while
others disagree. So now let’s take a look at why some researchers
think they exist, and the unexplained scientific events that could actually be proof that parallel
universes might exist...but first, we need a little bit of physics to understand everything. In quantum theory, an elementary particle
such as an electron doesn’t exist in a single state, but a multiplicity of locations, velocities,
and orientations. One of those most famous logic-defying experiments
in physics is called the double-slit experiment. Waves that pass through two narrow slits will
form an interference pattern on a screen. It doesn’t matter if it's light waves, water
waves, or sound waves. However, light isn’t only a wave, it is
also a particle called a photon. Now here is where it starts to get weird. If you shoot a photon through the double slits,
it still forms an interference pattern as if the photon was traveling through both slits
at the same time. But here is where it gets more bizarre. Just by observing the double-slit experiment,
the behavior of the photon changes. Even if the photons are sent through the slits
one at a time, there is still a wave present that produces the interference pattern. This is a wave of probability because the
experiment is set up so the scientists don't know which of the two slits the single photon
will pass through. But, if they try to find out which slit the
photon really goes through by setting up detectors in front of each slit, then the interference
pattern doesn’t show up at all. So the scientists tried a variation on the
double-slit experiment and placed a special crystal at each slit that would split any
incoming photon into an identical pair. One photon should create the standard interference
pattern, while the other would travel to the detector. But the strangest thing is that it still didn’t
work. This means that observing a photon can change
events that have already happened. This is still one of the greatest mysteries
of quantum mechanics. From a physics point of view, parallel universes
are one of those imaginative and compelling theories that is very difficult to test, if
not impossible. However, the idea of many worlds began in
1926 when physicist Erwin Schrödinger demonstrated that the subatomic world is fundamentally
blurry. In our familiar human-scale reality, an object
exists in one well-defined place. Put your phone on the table next to you, and
it’s in the only place it can be regardless if you’re looking for it or not. But in the quantum realm, objects exist in
a small state of probability, and snap into focus only when observed. Before you look at an object, whether it’s
an electron, or an atom, it’s not in any definite location. It might be more likely that you observe the
object in one place or another, but it’s not located in a particular place. After nearly a century of experimentation,
this phenomenon is a core aspect of the physical world. It might sound crazy, and even Einstein struggled
with the idea. What happened to all the other possible locations
where the object could have been, and why should an object's behavior depend on whether
or not somebody was looking at it? Someone was bound to come up with a radical
explanation for this phenomenon. And in 1957, a man by the name of Hugh Everett
III (the third) while he was having a conversation with friends about physics. It was then that he came up with a wild idea
about how to fix this most perplexing problem in quantum mechanics. Therefore, Everett imagined a multiverse full
of different realms in which all the possibilities dictated by quantum mechanics could exist
at once. He proposed that all possible outcomes really
do occur, but that only a single version plays out in the world we live in. All the other possibilities split off from
us with each one giving rise in its own separate world, and everything that can happen does
happen in some world. All of this sounded really bizarre, and no
one would take Everett seriously at the time. But now, some physicists are considering the
possibility of a multiverse. In fact, theories of cosmology, quantum physics,
and the very philosophy of science have some problems that could be solved if a multiverse
existed. Along with the idea of multiple universes
created by infinitely extending space-time, other universes could also come into existence
from a theory called ‘eternal inflation’. We already talked about how the universe we
are in expanded rapidly after the Big Bang, and inflated somewhat like a balloon. Eternal inflation theorizes that some pockets
of space stop inflating while others continue to inflate giving the rise to many isolated
‘bubble universes’. That said, our own universe could be just
a separate bubble in the vast sea of space that contains other ‘bubble universes’
like ours. There is even another idea which comes from
string theory called ‘braneworlds’ which are parallel universes that hover out of reach
to our own. This theory is centered around the idea that
there could be many more dimensions to our world besides the three space dimensions,
and the dimension of time. These three-dimensional ‘braneworlds’
could exist in a higher-dimensional space. So is it possible that a multiverse or parallel
universes could exist? Well, recently there was a scientific experiment
done and the outcome was evidence of parallel universes. In 2016, a group of NASA scientists were working
with NASA’s Antarctic Impulsive Transient Antenna, or ANITA for short. It is a high-altitude helium balloon with
an array of radio antennas. This instrument was designed to detect ultra-high
energy cosmic-ray neutrinos which are high energy particles a million times more powerful
than anything we can create on Earth, and they are the only neutrinos that can reach
Earth without being weakened or reduced. Low-energy, subatomic neutrinos with a mass
close to zero can pass completely through the Earth. However, high-energy particles would be stopped
by the planet's solid matter, which is why high energy particles are detected coming
down from space, and a constant ‘wind’ of these high-energy particles falls to Earth. But the team of NASA scientists were surprised
when ANITA detected heavier particles called tau neutrinos coming up out of the Earth! If the particles were indeed real, it would
mean they would have been traveling back in time, and could be evidence of a parallel
universe. But this would also mean that the parallel
universe would be running backwards in time. But the interesting thing about this, is that
if there were any inhabitants in this possible parallel universe, they would see us as the
one’s moving backwards in time. So what’s really going on here? No one is certain yet, but the main investigator
of ANITA said that they encountered a small number of anomalies in their data, and once
they have exhausted all the possible explanations within the standard model of physics, only
then will it be time to consider ideas that push those boundaries. But more evidence has been found out in space
that could point to the existence of parallel universes. There are significant events in time and space
that leave their marks on the cosmos, and the Big Bang left its footprint on everything
we observe today. Recently, the European Space Agency’s Planck
satellite mapped the cosmic microwave background, the primordial microwave radiation that fills
the known universe. This relic radiation is a perfect record of
our universe from the moment it inflated and expanded. At first glance, the CMB looks to have a uniform
temperature, but at micro-kelvin scales, you can see variations in temperature in the form
of hot and cold patches. This is due to tiny quantum density fluctuations
that occurred when the universe was just born, meaning that matter wasn’t even distributed,
and some areas of the universe are more densely packed than others. But there is an intriguing mystery which concerns
a large and unusually cold patch on the CMB which is an astounding 1.8 billion light-years
across. This CMB cold spot is much colder than the
average CMB temperature, and this strange cold spot appears in the southern celestial
hemisphere. Some researchers previously thought this space
could be cooler simply because it had less matter than most sections of space. However, in a recently published survey of
galaxies, astronomers say that this cold supervoid should not exist. And in a separate study, simulations suggested
there was only a two percent probability that this Cold Spot formed randomly. However, researchers cannot entirely rule
out the possibility. But if this is not the answer, then there
could be more exotic explanations. One of those is that the Cold Spot was created
by a collision between our universe and another bubble universe. Black holes are a major quandary when it comes
to our understanding of physics because either they can destroy information - which contradicts
what we know about quantum mechanics, or they disregard Einstein’s theory of relativity. Now scientists are applying the many worlds
theory, now called Everettian, to the black hole information problem. By using the many worlds interpretation, scientists
are finding new ways to answer mysterious questions about black holes. Who knows, maybe black holes could have something
to do with parallel worlds. Speaking of black holes, we have a new video
here to check out if you haven’t seen it yet. We hope you enjoyed this video. If you have some ideas on what you’d like
to see next, let us know in the comments, and thanks for watching.
