[Applause] in the year 1783 a famous British
in the year 1783 a famous British
in the year 1783 a famous British scientist called the Reverend John
scientist called the Reverend John
scientist called the Reverend John Mitchell the rector of this church in
Mitchell the rector of this church in
Mitchell the rector of this church in fawn Hill Yorkshire presented a paper to
fawn Hill Yorkshire presented a paper to
fawn Hill Yorkshire presented a paper to the Royal Society in London in his paper
the Royal Society in London in his paper
the Royal Society in London in his paper he argued that there could be in space
he argued that there could be in space
he argued that there could be in space possibly objects whose gravity was so
possibly objects whose gravity was so
possibly objects whose gravity was so strong that you could not escape from
strong that you could not escape from
strong that you could not escape from them even if you went as fast as the
them even if you went as fast as the
them even if you went as fast as the speed of light and of course if light
speed of light and of course if light
speed of light and of course if light would not escape then someone on the
would not escape then someone on the
would not escape then someone on the outside was not going to be able to see
outside was not going to be able to see
outside was not going to be able to see the object the Reverend Mitchell had had
the object the Reverend Mitchell had had
the object the Reverend Mitchell had had become the first person to postulate the
become the first person to postulate the
become the first person to postulate the existence of what we now call black
existence of what we now call black
existence of what we now call black holes now John Mitchell had used Isaac
holes now John Mitchell had used Isaac
holes now John Mitchell had used Isaac Newton’s theory of gravity a theory
Newton’s theory of gravity a theory
Newton’s theory of gravity a theory which we now know is not accurate when
which we now know is not accurate when
which we now know is not accurate when gravity is very strong but in 1958 and a
gravity is very strong but in 1958 and a
gravity is very strong but in 1958 and a American physicist called David
American physicist called David
American physicist called David Finklestein used Albert Einstein’s
Finklestein used Albert Einstein’s
Finklestein used Albert Einstein’s general theory of relativity a much more
general theory of relativity a much more
general theory of relativity a much more accurate theory of gravity to prove that
accurate theory of gravity to prove that
accurate theory of gravity to prove that black holes could indeed exist even
black holes could indeed exist even
black holes could indeed exist even though light can’t escape from the black
though light can’t escape from the black
though light can’t escape from the black hole the black hole has still got
hole the black hole has still got
hole the black hole has still got gravity so it can be detected by its
gravity so it can be detected by its
gravity so it can be detected by its gravitational influence on things around
gravitational influence on things around
gravitational influence on things around it now currency dentally back in the
it now currency dentally back in the
it now currency dentally back in the 1780s while John Mitchell was
1780s while John Mitchell was
1780s while John Mitchell was speculating about the existence of black
speculating about the existence of black
speculating about the existence of black holes a friend of his a composer called
holes a friend of his a composer called
holes a friend of his a composer called William Herschel was using very large
William Herschel was using very large
William Herschel was using very large homemade backyard telescopes to sweep
homemade backyard telescopes to sweep
homemade backyard telescopes to sweep the sky and discover objects that we now
the sky and discover objects that we now
the sky and discover objects that we now recognize as being distant galaxies and
recognize as being distant galaxies and
recognize as being distant galaxies and in some of these in the very center we
in some of these in the very center we
in some of these in the very center we call the nucleus he detected bright
call the nucleus he detected bright
call the nucleus he detected bright points of light here’s a picture of one
points of light here’s a picture of one
points of light here’s a picture of one of those ones we call it NGC 55 48
of those ones we call it NGC 55 48
of those ones we call it NGC 55 48 this is a Hubble Space Telescope picture
this is a Hubble Space Telescope picture
this is a Hubble Space Telescope picture of it and it turns very bright in the
of it and it turns very bright in the
of it and it turns very bright in the middle in what we call the nucleus the
middle in what we call the nucleus the
middle in what we call the nucleus the central galaxies there well and Herschel
central galaxies there well and Herschel
central galaxies there well and Herschel had no way of knowing this but he was
had no way of knowing this but he was
had no way of knowing this but he was seeing light being emitted not by stars
seeing light being emitted not by stars
seeing light being emitted not by stars in the galaxy there but by gas spiraling
in the galaxy there but by gas spiraling
in the galaxy there but by gas spiraling into a supermassive black hole it was
into a supermassive black hole it was
into a supermassive black hole it was not until the beginning of the 20th
not until the beginning of the 20th
not until the beginning of the 20th century that astronomers got more
century that astronomers got more
century that astronomers got more indications that something bizarre was
indications that something bizarre was
indications that something bizarre was happening in the nuclei of galaxies like
happening in the nuclei of galaxies like
happening in the nuclei of galaxies like NGC 55:48 astronomers at Lick
NGC 55:48 astronomers at Lick
NGC 55:48 astronomers at Lick Observatory analyzed the light coming
Observatory analyzed the light coming
Observatory analyzed the light coming out of nucleus of his galaxy and
out of nucleus of his galaxy and
out of nucleus of his galaxy and discovered that there was lots of hot
discovered that there was lots of hot
discovered that there was lots of hot glowing gas there and remarkably this
glowing gas there and remarkably this
glowing gas there and remarkably this gas was moving very quickly it was being
gas was moving very quickly it was being
gas was moving very quickly it was being much faster than the stars were in the
much faster than the stars were in the
much faster than the stars were in the galaxy in fact it was even going up to a
galaxy in fact it was even going up to a
galaxy in fact it was even going up to a few percent of the speed of light over
few percent of the speed of light over
few percent of the speed of light over the next couple of decades astronomers
the next couple of decades astronomers
the next couple of decades astronomers began to detect radio emission from
began to detect radio emission from
began to detect radio emission from galaxies such as this one here called
galaxies such as this one here called
galaxies such as this one here called sin a and that radio mission was very
sin a and that radio mission was very
sin a and that radio mission was very powerful in the mid-1950s the
powerful in the mid-1950s the
powerful in the mid-1950s the husband-wife team of Jeffrey and
husband-wife team of Jeffrey and
husband-wife team of Jeffrey and Margaret Burbidge calculated that the
Margaret Burbidge calculated that the
Margaret Burbidge calculated that the energy being put out by an active
energy being put out by an active
energy being put out by an active galactic nucleus in something like cen a
galactic nucleus in something like cen a
galactic nucleus in something like cen a was the equivalent of 100 million
was the equivalent of 100 million
was the equivalent of 100 million supernova explosions going off as a star
supernova explosions going off as a star
supernova explosions going off as a star exploding as a supernova it was a
exploding as a supernova it was a
exploding as a supernova it was a tremendous amount of energy
tremendous amount of energy
tremendous amount of energy in 1963 two of their collaborators Fred
in 1963 two of their collaborators Fred
in 1963 two of their collaborators Fred Hoyle and really Fowler published a
Hoyle and really Fowler published a
Hoyle and really Fowler published a paper in which they they argued that
paper in which they they argued that
paper in which they they argued that such a huge source of energy could only
such a huge source of energy could only
such a huge source of energy could only be a supermassive black hole some kind
be a supermassive black hole some kind
be a supermassive black hole some kind of hypothetical super star where the
of hypothetical super star where the
of hypothetical super star where the nuclear reactions going on inside it
nuclear reactions going on inside it
nuclear reactions going on inside it simply could not provide enough energy
simply could not provide enough energy
simply could not provide enough energy most of you are probably familiar with a
most of you are probably familiar with a
most of you are probably familiar with a concept of energy particularly if you
concept of energy particularly if you
concept of energy particularly if you pay
pay
pay and electric bill well where is the
and electric bill well where is the
and electric bill well where is the electric company get that energy from
electric company get that energy from
electric company get that energy from well one possibility is something like
well one possibility is something like
well one possibility is something like this this is the itaipu hydroelectric
this this is the itaipu hydroelectric
this this is the itaipu hydroelectric dam it’s very tall it’s about 40 stories
dam it’s very tall it’s about 40 stories
dam it’s very tall it’s about 40 stories from bottom to top there that’s like a
from bottom to top there that’s like a
from bottom to top there that’s like a big skyscraper at the top of the dam up
big skyscraper at the top of the dam up
big skyscraper at the top of the dam up here upstream is the water and we say
here upstream is the water and we say
here upstream is the water and we say that this water has gravitational
that this water has gravitational
that this water has gravitational potential energy that means it has the
potential energy that means it has the
potential energy that means it has the potential to convert and produce other
potential to convert and produce other
potential to convert and produce other forms of energy so the dam the water
forms of energy so the dam the water
forms of energy so the dam the water falls over the dam here falls down 118
falls over the dam here falls down 118
falls over the dam here falls down 118 meters and as it does that it is
meters and as it does that it is
meters and as it does that it is accelerated by the Earth’s gravitational
accelerated by the Earth’s gravitational
accelerated by the Earth’s gravitational speed and as it as it gains speed the
speed and as it as it gains speed the
speed and as it as it gains speed the gravitational potential energy is
gravitational potential energy is
gravitational potential energy is changed into energy of motion and that
changed into energy of motion and that
changed into energy of motion and that rushing water the bottom of the dam
rushing water the bottom of the dam
rushing water the bottom of the dam drives turbines and generators to make
drives turbines and generators to make
drives turbines and generators to make the electric current which is then
the electric current which is then
the electric current which is then shipped off and heats and lights
shipped off and heats and lights
shipped off and heats and lights people’s houses and so on the
people’s houses and so on the
people’s houses and so on the hydroelectric dam like this is a very
hydroelectric dam like this is a very
hydroelectric dam like this is a very good analog of how a supermassive black
good analog of how a supermassive black
good analog of how a supermassive black hole produces energy here the water is
hole produces energy here the water is
hole produces energy here the water is only falling down 118 meters matter
only falling down 118 meters matter
only falling down 118 meters matter falling into a black hole will fall
falling into a black hole will fall
falling into a black hole will fall trillions of kilometers that’s further
trillions of kilometers that’s further
trillions of kilometers that’s further than the outer regions of the solar
than the outer regions of the solar
than the outer regions of the solar system a good fraction the way to the
system a good fraction the way to the
system a good fraction the way to the nearest star and it’s being serrated not
nearest star and it’s being serrated not
nearest star and it’s being serrated not by the gentle gravitational pull which
by the gentle gravitational pull which
by the gentle gravitational pull which is holding us down on our seats right
is holding us down on our seats right
is holding us down on our seats right now it’s being accelerated by the
now it’s being accelerated by the
now it’s being accelerated by the tremendous gravitational pull of the
tremendous gravitational pull of the
tremendous gravitational pull of the black hole if we calculate how much
black hole if we calculate how much
black hole if we calculate how much energy is being produced there for let’s
energy is being produced there for let’s
energy is being produced there for let’s say one kilogram of material falling
say one kilogram of material falling
say one kilogram of material falling into a black hole it’s enormous
into a black hole it’s enormous
into a black hole it’s enormous it’s more than a nuclear explosion of
it’s more than a nuclear explosion of
it’s more than a nuclear explosion of this material would generate well a mere
this material would generate well a mere
this material would generate well a mere five weeks after
five weeks after
five weeks after Hoyle and Fowler had published their
Hoyle and Fowler had published their
Hoyle and Fowler had published their paper the same Journal carried some
paper the same Journal carried some
paper the same Journal carried some papers that identified this object
papers that identified this object
papers that identified this object scored 3c273 looks like a bright star
scored 3c273 looks like a bright star
scored 3c273 looks like a bright star and indeed that was what people had
and indeed that was what people had
and indeed that was what people had previously thought it was but
previously thought it was but
previously thought it was but astronomers at Caltech showed that this
astronomers at Caltech showed that this
astronomers at Caltech showed that this is in fact a distant active galactic
is in fact a distant active galactic
is in fact a distant active galactic nucleus and it’s very bright and it’s
nucleus and it’s very bright and it’s
nucleus and it’s very bright and it’s very far away and the brightness of this
very far away and the brightness of this
very far away and the brightness of this is more than hundreds of times greater
is more than hundreds of times greater
is more than hundreds of times greater than the brightness of an entire bright
than the brightness of an entire bright
than the brightness of an entire bright galaxy of a trillion stars we can
galaxy of a trillion stars we can
galaxy of a trillion stars we can appreciate that in this Hubble Space
appreciate that in this Hubble Space
appreciate that in this Hubble Space Telescope picture up here these little
Telescope picture up here these little
Telescope picture up here these little blurry patches which you might not be
blurry patches which you might not be
blurry patches which you might not be able to see over here
able to see over here
able to see over here those are entire galaxies like our own
those are entire galaxies like our own
those are entire galaxies like our own but it’s look how bright 3c273 is it’s
but it’s look how bright 3c273 is it’s
but it’s look how bright 3c273 is it’s brilliantly bright here compared to
brilliantly bright here compared to
brilliantly bright here compared to these ordinary galaxies over here it’s
these ordinary galaxies over here it’s
these ordinary galaxies over here it’s so blindingly bright that we can’t even
so blindingly bright that we can’t even
so blindingly bright that we can’t even tell that it’s located in a galaxy there
tell that it’s located in a galaxy there
tell that it’s located in a galaxy there that of course caused enormous
that of course caused enormous
that of course caused enormous excitement among astronomers and pretty
excitement among astronomers and pretty
excitement among astronomers and pretty quickly a whole lot more objects like
quickly a whole lot more objects like
quickly a whole lot more objects like this were being found in 1969 the
this were being found in 1969 the
this were being found in 1969 the English astrophysicist Donald Lyndon
English astrophysicist Donald Lyndon
English astrophysicist Donald Lyndon Bell argued a very important point he
Bell argued a very important point he
Bell argued a very important point he said well if objects like this by 3c273
said well if objects like this by 3c273
said well if objects like this by 3c273 faraway in the distant universe in the
faraway in the distant universe in the
faraway in the distant universe in the past were being powered by supermassive
past were being powered by supermassive
past were being powered by supermassive black holes then in nearby galaxies
black holes then in nearby galaxies
black holes then in nearby galaxies there must be boremont black holes
there must be boremont black holes
there must be boremont black holes because a supermassive black hole is
because a supermassive black hole is
because a supermassive black hole is simply not going to go anywhere
simply not going to go anywhere
simply not going to go anywhere overnight and a large body of research
overnight and a large body of research
overnight and a large body of research continuing down to this present day by
continuing down to this present day by
continuing down to this present day by many astronomers as shown that this is
many astronomers as shown that this is
many astronomers as shown that this is indeed the case we now think that every
indeed the case we now think that every
indeed the case we now think that every massive galaxy has a supermassive black
massive galaxy has a supermassive black
massive galaxy has a supermassive black hole in its center the nearest and best
hole in its center the nearest and best
hole in its center the nearest and best example of this is actually our own
example of this is actually our own
example of this is actually our own galaxy the Milky Way the center of the
galaxy the Milky Way the center of the
galaxy the Milky Way the center of the Milky Way the nucleus the Milky Way is
Milky Way the nucleus the Milky Way is
Milky Way the nucleus the Milky Way is about 25,000 light-years away in
about 25,000 light-years away in
about 25,000 light-years away in direction the constellation of
direction the constellation of
direction the constellation of Sagittarius but you will not be able to
Sagittarius but you will not be able to
Sagittarius but you will not be able to see it with your eye but because there’s
see it with your eye but because there’s
see it with your eye but because there’s a lot of dust in space in the way
a lot of dust in space in the way
a lot of dust in space in the way however very large telescopes using
however very large telescopes using
however very large telescopes using infrared cameras can penetrate the dust
infrared cameras can penetrate the dust
infrared cameras can penetrate the dust and get us pictures of what’s going on
and get us pictures of what’s going on
and get us pictures of what’s going on there and I want to show you a
there and I want to show you a
there and I want to show you a time-lapse movie which is based on
time-lapse movie which is based on
time-lapse movie which is based on images taken by the European Southern
images taken by the European Southern
images taken by the European Southern Observatory’s Very Large Telescope or
Observatory’s Very Large Telescope or
Observatory’s Very Large Telescope or VLT in Chile notice there’s nothing at
VLT in Chile notice there’s nothing at
VLT in Chile notice there’s nothing at the cross there notice that and each one
the cross there notice that and each one
the cross there notice that and each one of those blobs there’s a star and I
of those blobs there’s a star and I
of those blobs there’s a star and I click to start the movie then the date
click to start the movie then the date
click to start the movie then the date of observation if you’re wondering when
of observation if you’re wondering when
of observation if you’re wondering when it was will appear up there ok so you
it was will appear up there ok so you
it was will appear up there ok so you can see that the stars are moving around
can see that the stars are moving around
can see that the stars are moving around this is from year to year here and
this is from year to year here and
this is from year to year here and they’re moving fastest around this cross
they’re moving fastest around this cross
they’re moving fastest around this cross in the middle here let’s zoom in on the
in the middle here let’s zoom in on the
in the middle here let’s zoom in on the cross and watch these stars are going
cross and watch these stars are going
cross and watch these stars are going around in elliptical orbits there and
around in elliptical orbits there and
around in elliptical orbits there and let’s watch again to this star number 2
let’s watch again to this star number 2
let’s watch again to this star number 2 up there
up there
up there astronomers have real exciting names for
astronomers have real exciting names for
astronomers have real exciting names for stars here it comes to comes around here
stars here it comes to comes around here
stars here it comes to comes around here zips around that cross at high speed
zips around that cross at high speed
zips around that cross at high speed there well we can use Newton’s laws of
there well we can use Newton’s laws of
there well we can use Newton’s laws of motion use law of gravity to calculate
motion use law of gravity to calculate
motion use law of gravity to calculate what force you need to make that star
what force you need to make that star
what force you need to make that star swing round like that and how much mass
swing round like that and how much mass
swing round like that and how much mass is needed if it’s done by gravity which
is needed if it’s done by gravity which
is needed if it’s done by gravity which it is and that comes out to be over 4
it is and that comes out to be over 4
it is and that comes out to be over 4 million times the mass of the Sun well
million times the mass of the Sun well
million times the mass of the Sun well notice the obvious thing there there
notice the obvious thing there there
notice the obvious thing there there isn’t anything at the location of the
isn’t anything at the location of the
isn’t anything at the location of the Cross there if there’s 4 million solar
Cross there if there’s 4 million solar
Cross there if there’s 4 million solar masses were in some kind of hyper super
masses were in some kind of hyper super
masses were in some kind of hyper super star powered by nuclear reactions as our
star powered by nuclear reactions as our
star powered by nuclear reactions as our Sun is that would be a blindingly bright
Sun is that would be a blindingly bright
Sun is that would be a blindingly bright star so bright that that picture we
star so bright that that picture we
star so bright that that picture we completely washed out and white and you
completely washed out and white and you
completely washed out and white and you wouldn’t be able to see anything up
wouldn’t be able to see anything up
wouldn’t be able to see anything up there instead the stars are orbiting
there instead the stars are orbiting
there instead the stars are orbiting around 4 million solar masses of
around 4 million solar masses of
around 4 million solar masses of darkness over there these observations
darkness over there these observations
darkness over there these observations are our clearest proof that supermassive
are our clearest proof that supermassive
are our clearest proof that supermassive black holes do indeed exist there’s now
black holes do indeed exist there’s now
black holes do indeed exist there’s now no reasonable doubt that in the nuclei
no reasonable doubt that in the nuclei
no reasonable doubt that in the nuclei of galaxies there are supermassive black
of galaxies there are supermassive black
of galaxies there are supermassive black holes well how do you feed a black hole
holes well how do you feed a black hole
holes well how do you feed a black hole let me tell you something about black
let me tell you something about black
let me tell you something about black holes black holes do not suck black
holes black holes do not suck black
holes black holes do not suck black holes are not some kind of cosmic vacuum
holes are not some kind of cosmic vacuum
holes are not some kind of cosmic vacuum cleaner going around sweeping up sucking
cleaner going around sweeping up sucking
cleaner going around sweeping up sucking up everything around them it is in fact
up everything around them it is in fact
up everything around them it is in fact rather hard to go into a black hole the
rather hard to go into a black hole the
rather hard to go into a black hole the reason for this is that except when
reason for this is that except when
reason for this is that except when you’re extremely close to the black hole
you’re extremely close to the black hole
you’re extremely close to the black hole gravity is a black hole is pretty normal
gravity is a black hole is pretty normal
gravity is a black hole is pretty normal it’s just like any other gravity in the
it’s just like any other gravity in the
it’s just like any other gravity in the universe the earth is orbiting the Sun
universe the earth is orbiting the Sun
universe the earth is orbiting the Sun if the Sun were suddenly to turn into a
if the Sun were suddenly to turn into a
if the Sun were suddenly to turn into a black hole and don’t worry it won’t
black hole and don’t worry it won’t
black hole and don’t worry it won’t happen but if it did if the Sun suddenly
happen but if it did if the Sun suddenly
happen but if it did if the Sun suddenly became a black hole well the earth would
became a black hole well the earth would
became a black hole well the earth would just keep on orbiting around the Sun
just keep on orbiting around the Sun
just keep on orbiting around the Sun it’ll be dark that’s all but the earth
it’ll be dark that’s all but the earth
it’ll be dark that’s all but the earth will keep going around in the same orbit
will keep going around in the same orbit
will keep going around in the same orbit let’s watch go back to our little movie
let’s watch go back to our little movie
let’s watch go back to our little movie of the center of our galaxy and zoom in
of the center of our galaxy and zoom in
of the center of our galaxy and zoom in again and again let’s watch this star –
again and again let’s watch this star –
again and again let’s watch this star – at the top here go slowly first a little
at the top here go slowly first a little
at the top here go slowly first a little bit like Halley’s Comet clear around the
bit like Halley’s Comet clear around the
bit like Halley’s Comet clear around the Sun it speeds in and zips around there
Sun it speeds in and zips around there
Sun it speeds in and zips around there the important point here is star 2 there
the important point here is star 2 there
the important point here is star 2 there watch it again is not getting sucked
watch it again is not getting sucked
watch it again is not getting sucked into the black hole to go into a black
into the black hole to go into a black
into the black hole to go into a black hole that star would have been on a
hole that star would have been on a
hole that star would have been on a direct collision course with the black
direct collision course with the black
direct collision course with the black hole and that’s probably not going to
hole and that’s probably not going to
hole and that’s probably not going to happen because the black hole is really
happen because the black hole is really
happen because the black hole is really small so it’s gonna miss and it’s gonna
small so it’s gonna miss and it’s gonna
small so it’s gonna miss and it’s gonna go flying off this matter going the
go flying off this matter going the
go flying off this matter going the black holes is mostly gas or is entirely
black holes is mostly gas or is entirely
black holes is mostly gas or is entirely gas and the thing about gas is gas
gas and the thing about gas is gas
gas and the thing about gas is gas doesn’t easily pass through gas
doesn’t easily pass through gas
doesn’t easily pass through gas if you’ve seen a couple of fires burning
if you’ve seen a couple of fires burning
if you’ve seen a couple of fires burning with columns of smoke when the smoke
with columns of smoke when the smoke
with columns of smoke when the smoke comes together they doesn’t pass through
comes together they doesn’t pass through
comes together they doesn’t pass through like this and keep on going it comes
like this and keep on going it comes
like this and keep on going it comes together and it swirls together in one
together and it swirls together in one
together and it swirls together in one column of smoke
column of smoke
column of smoke well Donald Lyndon Bell recognized that
well Donald Lyndon Bell recognized that
well Donald Lyndon Bell recognized that gas that was falling in towards a
gas that was falling in towards a
gas that was falling in towards a supermassive black hole was going to end
supermassive black hole was going to end
supermassive black hole was going to end up swirling together and end up
up swirling together and end up
up swirling together and end up spiraling around it and settling down
spiraling around it and settling down
spiraling around it and settling down into we caught an accretion disk now
into we caught an accretion disk now
into we caught an accretion disk now disks are quite common in astronomy this
disks are quite common in astronomy this
disks are quite common in astronomy this is a the best-known nearby example the
is a the best-known nearby example the
is a the best-known nearby example the rings of Saturn the rings of Saturn are
rings of Saturn the rings of Saturn are
rings of Saturn the rings of Saturn are particles of dust and ice orbiting
particles of dust and ice orbiting
particles of dust and ice orbiting together around Saturn here in a very
together around Saturn here in a very
together around Saturn here in a very thin plane the material into black hole
thin plane the material into black hole
thin plane the material into black hole is actually not dust and ice like
is actually not dust and ice like
is actually not dust and ice like Saturn’s rings they’re it’s gas gases
Saturn’s rings they’re it’s gas gases
Saturn’s rings they’re it’s gas gases and liquids have a special property that
and liquids have a special property that
and liquids have a special property that we call viscosity viscosity means that
we call viscosity viscosity means that
we call viscosity viscosity means that one part of a gas is pulling another
one part of a gas is pulling another
one part of a gas is pulling another part of one part of liquid it’s pulling
part of one part of liquid it’s pulling
part of one part of liquid it’s pulling on another part and I’ve got a little
on another part and I’ve got a little
on another part and I’ve got a little demonstration to show this over here so
demonstration to show this over here so
demonstration to show this over here so here I have a jar and inside this jar is
here I have a jar and inside this jar is
here I have a jar and inside this jar is an apple I just thought if we can do an
an apple I just thought if we can do an
an apple I just thought if we can do an experiment with gravity than Apple was
experiment with gravity than Apple was
experiment with gravity than Apple was the right fruit to use if I take this
the right fruit to use if I take this
the right fruit to use if I take this Apple here in the jar I turn the jar
Apple here in the jar I turn the jar
Apple here in the jar I turn the jar upside down you all know what’s going to
upside down you all know what’s going to
upside down you all know what’s going to happen it’s going to fall down on the
happen it’s going to fall down on the
happen it’s going to fall down on the ground so here we have a fine Apple who
ground so here we have a fine Apple who
ground so here we have a fine Apple who would like an apple in my other jar over
would like an apple in my other jar over
would like an apple in my other jar over here I have something different this is
here I have something different this is
here I have something different this is a jar of honey
a jar of honey
a jar of honey organizers won’t mind if I tip this
organizers won’t mind if I tip this
organizers won’t mind if I tip this honey upside down upward on the carpet
honey upside down upward on the carpet
honey upside down upward on the carpet right oh it’s not down very quickly is
right oh it’s not down very quickly is
right oh it’s not down very quickly is it that’s because honey is viscous and
it that’s because honey is viscous and
it that’s because honey is viscous and the viscosity of the honey means that
the viscosity of the honey means that
the viscosity of the honey means that there’s a blob in the middle which would
there’s a blob in the middle which would
there’s a blob in the middle which would like to fall down on the floor make a
like to fall down on the floor make a
like to fall down on the floor make a mess on this nice red carpet here
mess on this nice red carpet here
mess on this nice red carpet here but it’s being held back by the
but it’s being held back by the
but it’s being held back by the viscosity of the honey which is around
viscosity of the honey which is around
viscosity of the honey which is around it and that honey in turn is being held
it and that honey in turn is being held
it and that honey in turn is being held back by the edge of the jar there well a
back by the edge of the jar there well a
back by the edge of the jar there well a similar thing happens in the accretion
similar thing happens in the accretion
similar thing happens in the accretion disk the viscosity in the gas is not
disk the viscosity in the gas is not
disk the viscosity in the gas is not quite like the viscosity in the honey
quite like the viscosity in the honey
quite like the viscosity in the honey it’s actually provided by tangled up
it’s actually provided by tangled up
it’s actually provided by tangled up magnetic fields but let’s have a look I
magnetic fields but let’s have a look I
magnetic fields but let’s have a look I decide on rings again what you can
decide on rings again what you can
decide on rings again what you can probably tell from this picture here is
probably tell from this picture here is
probably tell from this picture here is that the inner part of the Rings is
that the inner part of the Rings is
that the inner part of the Rings is going faster than the outside part you
going faster than the outside part you
going faster than the outside part you can see sort of directly dragged off
can see sort of directly dragged off
can see sort of directly dragged off here this is like the planets going
here this is like the planets going
here this is like the planets going around the Sun mercury the closest
around the Sun mercury the closest
around the Sun mercury the closest planet a Sun goes faster than Venus and
planet a Sun goes faster than Venus and
planet a Sun goes faster than Venus and explanatory it goes fast in the earth
explanatory it goes fast in the earth
explanatory it goes fast in the earth and so on the gas on the faster orbits
and so on the gas on the faster orbits
and so on the gas on the faster orbits is being held back by the gas further
is being held back by the gas further
is being held back by the gas further out and that’s going to slow it down
out and that’s going to slow it down
out and that’s going to slow it down it’s gonna make you go into lower orbit
it’s gonna make you go into lower orbit
it’s gonna make you go into lower orbit and thus spiral into the black hole so
and thus spiral into the black hole so
and thus spiral into the black hole so Donald Lyndon Bell proposed that that is
Donald Lyndon Bell proposed that that is
Donald Lyndon Bell proposed that that is how you go inside a black hole well
how you go inside a black hole well
how you go inside a black hole well viscosity doesn’t just make stuff go
viscosity doesn’t just make stuff go
viscosity doesn’t just make stuff go into a black hole does something else as
into a black hole does something else as
into a black hole does something else as well and let’s do a little demonstration
well and let’s do a little demonstration
well and let’s do a little demonstration of the other thing that it does if you
of the other thing that it does if you
of the other thing that it does if you can could you take your two hands and
can could you take your two hands and
can could you take your two hands and squeeze them together and then I want to
squeeze them together and then I want to
squeeze them together and then I want to push hard and then rubbed up really hard
push hard and then rubbed up really hard
push hard and then rubbed up really hard and really vigorously okay what’s
and really vigorously okay what’s
and really vigorously okay what’s happening they’re getting hot and you’re
happening they’re getting hot and you’re
happening they’re getting hot and you’re moving your hands pretty slowly here
moving your hands pretty slowly here
moving your hands pretty slowly here inside the accretion disk the gas inside
inside the accretion disk the gas inside
inside the accretion disk the gas inside is going faster than the gas outside we
is going faster than the gas outside we
is going faster than the gas outside we call this a differential motion the
call this a differential motion the
call this a differential motion the differential motion between your hands
differential motion between your hands
differential motion between your hands here and the friction between them
here and the friction between them
here and the friction between them generates heat that you fairly quickly
generates heat that you fairly quickly
generates heat that you fairly quickly feel the viscosity in the accretion disk
feel the viscosity in the accretion disk
feel the viscosity in the accretion disk is like the friction in your hands and
is like the friction in your hands and
is like the friction in your hands and this is going to heat up that gas
this is going to heat up that gas
this is going to heat up that gas enormously it’s going to heat it up so
enormously it’s going to heat it up so
enormously it’s going to heat it up so much that it’s going to become white-hot
much that it’s going to become white-hot
much that it’s going to become white-hot and that is the cause of the brilliant
and that is the cause of the brilliant
and that is the cause of the brilliant light we’re seeing from 3c273 there and
light we’re seeing from 3c273 there and
light we’re seeing from 3c273 there and that is also how those Dark Star
that is also how those Dark Star
that is also how those Dark Star postulated by the Reverend John Mitchell
postulated by the Reverend John Mitchell
postulated by the Reverend John Mitchell over two centuries ago turn out to be
over two centuries ago turn out to be
over two centuries ago turn out to be the most powerful sources of energy in
the most powerful sources of energy in
the most powerful sources of energy in the universe
the universe
the universe thank you
thank you
thank you [Applause]
”
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