black holes are the strangest and most
mind-blowing objects in the universe
they're a place where the known laws of
physics seem to break down it's
basically an area of total mystery
scientists are mostly baffled by them
but black holes seem to be an essential
part of most galaxies and unlocking
their secrets could be the key to
understanding the very fabric of our
universe
so what do we know about black holes
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scientists have long predicted black
holes as a theoretical possibility
for most of the 20th century they
assumed they must exist
but it wasn't until near the end of that
century that they developed the methods
to properly detect them
then in 2019 a global research group
made a huge leap forward the first ever
image of a black hole
finally after years of wondering here
was direct evidence that they do exist
admittedly that image is a little less
dramatic than the fiery tornado-like
vacuums we see in films
scientists are getting ever more details
about these weird cosmic objects
they've even discovered what they sound
like
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but we're still so much we don't
understand about them
let's start with what we do know a black
hole is a region of space that is so
dense there's so much gravity that
nothing not even light can escape
we know there are several types
first there are stellar black holes
they're formed when a massive star
implodes and its outer layers explode in
a supernova
we see these supernovas all the time
they're some of the brightest objects in
the universe sometimes a supernova can
be brighter than the entire galaxy that
it's inside
if the star is big enough the remains of
its core will collapse into an
infinitely tiny dimensionless point and
a stellar black hole is born
there is so much
gravity condensed into that point we're
talking
several times the mass of the sun
condensed into a point that's smaller
than the smallest bit of an atom imagine
it's very dense it basically rips
space-time at that point creates a hole
so it's a point of infinite density
and that point is known as a singularity
we know that stellar black holes can
have a mass three to 20 times greater
than that of our sun
they sound gigantic but this is nothing
compared to supermassive black holes
these can be millions or even billions
of times the mass of the sun
no one really knows where they came from
initially
or not yet anyway and it's thought that
most galaxies probably all galaxies have
a supermassive black hole at their
center
so what about the reputation that black
holes are cosmic hoovers that suck up
anything and everything within reach
we know this isn't entirely true not
everything gets drawn in if it stays far
enough away
but if an object does get too close
and it crosses what's known as the event
horizon around a black hole it's reached
a point of no return
it's pulled in towards the center
the singularity where gravity is
infinite
at least that's the assumption
what's going on in that point to create
that much gravity well we know that if
you have huge amounts of matter matter
creates gravity if you have huge amounts
of matter at a single point there's
going to be lots and lots of density of
gravity there
but that's about it singularities are
probably the most mysterious thing in
physics they're kind of like a word for
something that we just do not understand
despite pop culture depictions where the
hero escapes the pull of a black hole
reality
things probably wouldn't end well so
what happens people think is if you got
close enough
then each atom will be drawn out one at
a time until essentially your entire
ship and you on it i'm assuming would be
drawn out into a line of atoms
essentially a piece of spaghetti
scientists actually call this
spaghettification
it's been observed in stars as they
cross the event horizon dragged in by
the black holes unbeatable gravitational
attraction
even light can't escape a black hole
this means by definition they're
invisible so how do scientists detect
them
black holes do have an impact on the
space around them they might have
gravitational effects on other objects
to make them rotate around the black
hole
it's these telltale signs around a black
hole that help identify them
so if they go past a star then they will
deform that star because they'll try and
pull material away
in 1971 it was these gravitational
effects and radiation that led
astronomers to identify a black hole for
the first time
they determined that x-rays were coming
from a bright blue star
orbiting a strange dark object
this radiation showed stellar material
was being ripped away from the star and
consumed by a black hole they labelled
cygnus x1
spotting patterns of radiation like this
is still essential in detecting black
holes today around the event horizon in
the many many billions of miles around
the event horizon gas and dust is very
strongly affected by the gravitational
effect of the black hole but doesn't get
sucked in so it will spin around around
the black hole lots of energy will go
into it it might radiate in lots of
different colours including x-rays and
gamma rays which are the most energetic
forms of light
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so when we look at the images created by
the event horizon telescope
collaboration it's the light from the
material zooming around the black hole
that we see
it matched
the models that they'd created of what
light would look like if it was
surrounding a black hole but also then
bent by the gravity of the black hole in
2022 the event horizon team released
their second image showing the
supermassive black hole at the center of
our galaxy the milky way sagittarius a
star
27 000 light years away
if you've ever seen interstellar
the film they have a
cgi of a black hole which was actually
physically correct there were other
things about that film that weren't
quite right about black holes but the
way it looked was actually based on real
physics and that's what they saw in
these pictures essentially a very fuzzy
version of it not as high definition as
interstellar but that's what a black
hole would look like
sagittarius a star appears in the sky as
about the same size as a donut on the
moon
so it looks very very small
both images made by the event horizon
team were groundbreaking
providing solid proof that black holes
do exist
but many mysteries remain
like where does mata swallowed by a
black hole really go
according to general relativity albert
einstein's theory of gravitation
nothing can escape a black hole
so everything it consumes is destroyed
in 1974
stephen hawking theorized that black
holes emit a tiny bit of radiation
now known as hawking radiation
this radiation causes a black hole to
gradually lose mass
and after a very very long time
eventually disappear
it appears that all the information
about what fell in the black hole was
lost
but this clashes with another
fundamental of physics quantum theory
it states that even if an object is
transformed or destroyed its quantum
information details of each particle
inside an object and how it behaves can
never be lost
this disagreement is called the black
hole information paradox
these two big theories of physics
don't agree with each other what
physicists have been trying to do for
decades now is to find ways to connect
these theories up in other words to find
another physical idea which encompasses
both of them
physicists could be close to unlocking
this mystery which may require a new
theory altogether
the only way to understand some of the
biggest mysteries in the universe about
what the universe is made of and where
it's going in the future not to mention
where it came from these are things that
you can only understand if you have a
more universal rule of physics which we
know we don't have the thing that we're
looking for sits in the middle of the
black hole so if you can find out what's
in the middle of black hole you've
solved physics basically
well
maybe not all of physics
but probably some of its most enduring
questions
this is why black holes in all their
paradoxical mind-bending glory are so
important
they could help not only further our
understanding of the most fundamental
rules of physics
but might be the key to discovering more
about other weird mysterious parts of
the universe
including the beginning of it all the
big bang
i'm alek science correspondent at the
economist to read more on this topic
please click on the link opposite
thanks very much for watching and don't
forget to subscribe
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