It all began some 13.8 billion years ago from a hot dense rapidly expanding state known as the
big bang this is the best possible theory we know of how the universe came to be a question that's
been the basis of humanity's existential crisis from the moment we gain the ability to think
but that's only half the answer to the question there is a flip side to this existential crisis
we've always been morbidly curious about not only seeking knowledge about how it all started
but also about how it would all come to an end some think the universe will keep on expanding
till it tears itself into shreds or that all the stars will eventually die out causing the universe
to freeze as there'll be no heat but some believe that the universe will stop expanding and then
begin collapsing back into itself until everything crushes back into a singularity
and according to scientists this may happen sooner than you think welcome to Factnomenal
and today let's find out when and how the universe will start shrinking again marking the end of days
since the 1990s scientists have understood that the expansion of the universe is speeding up the
space between galaxies is widening faster now than it was billions of years ago this is an enigmatic
problem as none of the four major forces gravity electromagnetism or the weak and strong forces are
able to explain the cosmic acceleration scientists estimate that galaxies are getting .007 percent
further away from each other every million years due to this mystical force that we know
very little of but according to some researchers the reign of this unseen energy is perhaps coming
to an end after stretching the universe for billions of years relatively speaking its days
are numbered and when it stops the universe will begin collapsing inwards triggering the big crunch
how will the universe end not with a bang but a whimper wrote American poet T.S Eliot regarding
the end of the world he may be onto something because there's certainly a possibility that
the universe may end freezing over as one by one all sources of heat and space may
dissipate leaving the universe too cold to persist anymore eventually all the stars in the cosmos
will burn up their fuel with most of them leaving behind dense remnants known as white dwarfs and
neutron stars the largest stars will collapse into black holes while these beasts are not as ravenous
as they're often portrayed to be given enough time their massive gravitational attraction would draw
most matter into their all-consuming maws and when all the black holes lose their mass due to
hawking radiation even the black holes will fade away leaving nothing but inert energy in a cold
dark remnant of the universe however according to physicist and mathematician alexander friedman's
calculations our universe's destiny is determined by its density and it could either expand or
contract rather than remain in a steady state as would be the case in the big freeze scenario
with enough matter gravity would eventually halt the cosmos expansion causing it to come
crashing back inward astronomers added up all the matter in the known universe and calculated
that there's enough mass that the cosmos should ultimately collapse to an infinitely dense state
or perhaps even into one gargantuan black hole this math caused many astronomers to theorize
that the universe's life is a cyclic process it's born of a singularity expands until gravity wins
over dark energy and then the universe must collapse back to achieve a singularity again
to eventually kick-start yet another expansion also known as the big bounds in the 1970s and 80s
physicist john wheeler became a leading proponent of the big crunch yes the same john wheeler who
helped to coin the term black hole well after you get through saying completely collapsed objects
six times you look for a shortcut and that's when i found myself using the phrase
black hole as to him the big crunch was an obvious fate a revolution in understanding
black holes was underway wheeler saw each one as an experimental model
of the universe's final state but one must agree that this seems overly simple and wheeler two
admitted that his conclusion was based on the convenience that it was easy to picture
so was he wrong well not exactly but before we speculate on why the universe would shrink and
eventually collapse back in on itself we must understand why it expands in the first place
the early radical and rapid expansion of the universe was propelled by the big bang itself
it's theorized that since then gravity and dark energy have engaged in a cosmic tug of war
gravity pulls galaxies closer together dark energy pushes them apart whether the universe
is expanding or contracting depends on which force dominates gravity or dark energy after
the universe went through early inflation it began to cool down and protons and electrons
combined to form neutral hydrogen atoms thanks to this light was able to stream out into the
universe to form what we recognize today as the cosmic microwave background in these early stages
of the universe gravity was the major force that influenced the structure of the universe gravity
pulled the brakes on expansion slowing it down and made it possible for matter to coalesce
sometime down the line stars began to form and over the next several billion years
larger structures such as galaxies and galaxy clusters began to take shape and the universe was
starting to look a lot like it does today while these cosmic objects formed the space between
galaxies continued to expand but had an ever slower rate thanks to gravitational attraction
but somewhere between three and seven billion years after the big bang
something happened instead of the expansion slowing down it started to speed up dark energy
started to have a bigger influence than gravity the expansion has been accelerating ever since
though dark energy makes up approximately 70 of the total mass and energy of the universe its
properties remain a total mystery a popular theory introduced by Albert Einstein is that dark energy
is a cosmological constant and unchanging form of energy that's woven into the fabric of space-time
if that's the case and the force exerted by dark energy can never change then the universe should
continue expanding and accelerating forever or at least until it becomes so stretched and thin
that it will tear itself into pieces however now a competing theory suggests that dark
energy doesn't need to be constant in order to fit with observations of past cosmic expansion
this is based on an idea introduced in 1998 this theory proposes that dark energy may rather be
something called quintessence a dynamic field that changes over time
so what does that mean well quintessence can be either repulsive or attractive unlike a
cosmological constant which only works one way depending on the ratio of its kinetic
and potential energy at a given time dark energy can switch its tide from being a repulsive force
to an attractive one if that happened gravity and dark energy wouldn't be at odds with each other
but would work together to begin the contraction of the universe when that happens dark energy
will surrender to gravity and let the big force of attraction dominate the universe
beginning the end of days as we know it the only question now is when would that happen
Paul Steinhardt director of the Princeton Center for Theoretical Science at Princeton University
in new jersey and his team of researchers have predicted how the properties of quintessence
could change over the next several billion years based on their physical model of
quintessence they came to the conclusion that dark energy in their model could decay with time
according to the team's model the repellent force of dark energy could be amid a rapid decline that
potentially began billions of years ago if that's true the anti-gravitational property
of dark energy will eventually dissipate over time and the acceleration of the universe's expansion
would slow down or perhaps it is already slowing down and if that's the case within
just 65 million years it could stop all together but as dark energy isn't a constant it won't
just stop but perhaps would switch and could become attractive pulling the entire universe
inwards and after a massive 14 billion years of expansion space itself will begin contracting
the initial phase of shrinking would be quite gradual and any probable civilization existing
in the universe during this time wouldn't even notice the shrinkage but after a few
billion years the contraction would reduce the size of the current universe by half
according to steinhardt from there the universe may keep on contracting until it collapses in
on itself causing the big crunch or it may shrink just enough to return to the stage
where the universe was ripe enough to cause the big bang and immediately cause another big bang
aka the big bounce this phoenix-like resurgence of the universe would prove that our universe
may not be the first or only universe but just the latest in an infinite series of universes
that have expanded and contracted before ours but how plausible is this Gary Henshaw a professor of
physics and astronomy at the university of British Columbia believes that quintessence
is a perfectly reasonable supposition for what dark energy is but says it also depends on how
testable this theory is unfortunately as of now there's no good way to test whether quintessence
is real or whether the cosmic expansion has started to slow even professor Steinhardt admits
this but he's hopeful to find the answers in the team's future studies tell us in the comments do
you think our universe is unique or is it just one of the infinitely occurring many universes
that are born from the ashes of older ones and as always thanks for watching Factnomenal