- il y a 2 mois
The final agony of stars is often observed across many galaxies as supernovae, but they can also die quietly in despair. In their wake, they leave behind mesmerizing and mysterious remnants, some of which even lack a physical surface. During the lectures, we will peek behind the veil of secrecy of these compact objects, where gravitational, nuclear and electroweak forces are pushed to their extremes in an exciting competition for dominance.
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ÉducationTranscription
00:00:00we can start thank you everybody for coming again my name is nicolai and you're very welcome to ask
00:00:09a lot of questions and even maybe waiting for the micro not waiting for the micro if you're
00:00:15it is very urgent you can just shout very loud i can maybe repeat the question in the
00:00:23in the microphone and so on so we can move a bit faster so today we finally arrived at
00:00:29black hole everybody maybe was really waiting for for them these mysterious objects everybody's
00:00:36attracted to them and so on uh but first let me go through the the finish that the previous slides
00:00:45and like what we studied uh before and we were talking about neutron stars so neutron stars are
00:00:53kind of like perfectly compressed objects because they are very compact so the most compact objects
00:01:01in the universe but they have a surface so you can step on it you can have contention and principle
00:01:08you can extract a lot of information not only from the surface of the neutron star but also
00:01:14from the interiors for example with neutrino signals so you're we're kind of like connected
00:01:20to the neutron star in our universe and so on but if you compress the neutron star a little bit further
00:01:26nothing can resist the gravity anymore and it will collapse to the black hole and we will discuss it a
00:01:32little bit later but neutron star was so compact that actually already general relativity effects already
00:01:39start to play some role and we will discuss them a little bit later but just to give you some kind of
00:01:45feeling of them uh here i have a little bit of a of a movie so we can have if you have a neutron star
00:01:53and there is kind of a hot spot on the neutron star which was uh created by the environment of some
00:02:00particles on its surface so we just alter at some point we don't see really this hot spot because the
00:02:06neutron star is super small okay uh 12 kilometers of radius so it's impossible to see in a hot spot
00:02:12what we see from the neutron star is brightness and we see as the neutron star rotates and it has some
00:02:19uh this hot spot you see that the brightness increases and then increases over time and then you can
00:02:26construct a model so you can have your neutron star you can put this hot spot on the neutron star
00:02:32you can play with the size of the hot spot and it means temperature and you can feed this
00:02:38observational curve to the model and then you can kind of like update what it should be like the
00:02:43best and the best fit model it's called so what what should be the size of this spot and so on but
00:02:50because the neutron star is actually very complex and it's and this star so deforms or warps this that
00:02:58the space around it you can even see the other side of the neutron star for example of the moon we see
00:03:05we cannot see the other side of the moon yeah a lot of mysterious stuff about other side of the moon
00:03:13now we can i mean we've already photographed it and we even uh some satellites are right there but we
00:03:19cannot see it with a neutron star in principle you can see a bit of the other side just because the the
00:03:25space is so disturbed that for example from the that there is a photon emitted from the other side of
00:03:31the neutron star for example i am neutron star i'm emitting a photon there in principle you can never
00:03:36see it but because uh space is disturbed the photon will be bended and we will arrive right to you and
00:03:43you will see it and this basically this bending of the photon it depends on how compact is the star so
00:03:52what is the ratio of the mass to radius and then because if the neutron star is compact you will always see
00:03:59you see this whole spot always give you some information here the spot it appears and that's
00:04:05it but you will have this special or sorry general relativity effects we will see this whole spot and
00:04:12you will see all this brightness and then again with the best width model we can kind of estimate what
00:04:18should be the mass and the radius of the neutron star and this is what is done here here are some kind of
00:04:25contours and give you some estimation with observational errors and so on here there is another contour of
00:04:33what it should be the mass and radius of the neutron star here is mass in radius and then you can
00:04:38construct the model of your interaction what is the composition of the neutron star and i mean what is
00:04:44the equation of state of the neutron star that basically describes you what is the interaction in the center
00:04:49of the neutron star and so on and so on and you will close this curve and if this curve passes through
00:04:55all the contours you are very happy as a theoretician because you fulfilled all the observational constraints
00:05:01so your model is kind of good if not then you need to do your work better and these are models constructed here
00:05:10bsk it's actually brussels kern so these are models constructed uh here and there and you will be yeah in
00:05:18our group and then all these kind of occur they depend on what the competition of the neutron star surprisingly
00:05:26a neutron star is not just star of neutrons it also has protons electrons muons in the most basic scenario
00:05:35in the more exotic case you can have some condensate of pions of cairns or you can have some hyperons or
00:05:43you can have strange quark matter so the matter can be so compressed that you even go down from neutrons
00:05:50and protons to quarks quarks the kind of elementary particle as we understand them maybe in the future
00:05:58not because like atom was elementary but then it was not uh and so on uh and uh they they constitute
00:06:08actually proton and neutron zone so there could actually exist some quark stars or strange quark stars
00:06:15that consist of uh three quarks and they will be a bit smaller than neutron stars they are not yet
00:06:22discovered and as you can see all these contours here they kind of like in the in this in in this uh
00:06:30region but if you had some observation for example here this could actually point out for uh to a quarks
00:06:38but uh we don't have them yet uh yes and the another thing how to study a neutron star is uh is actually
00:06:50the cooling of the neutron star and again the cooling of the neutron star will depend on its
00:06:55composition so here's kind of we can observe different neutron stars for example one neutron star
00:07:01is hot then we say okay it's hot then it means that it is young if it is cold it means that this is old
00:07:09because it it cooled down very simple and we can uh pull the observation of orange here is kind of like
00:07:16temperature of the neutron star it should be here and here is the the year so age of the neutron star
00:07:24you can put these points here and then we can construct the model of the neutron star cooling
00:07:30so it starts very hard after the core cool of supernova super super hot and then it cooled down
00:07:37and the first moments again like the first stage of the neutron star cooling is neutrino cooling the neutron star
00:07:44is a bit particular in this sense because all the kind of like objects that we are used to they
00:07:51cool down from the surface to the interior so for example i don't know you eat a dumpling and on the
00:07:57surface it is already cold but if you buy it it would be hot in the middle because it it is cooled down
00:08:05by emission of photons and it's first from the surface then the heat arrives to the surface from the core
00:08:12and then it's always immediate the neutron star is a particular case because it's mainly cooled down
00:08:18by the emission of neutrinos and the most intense emission of neutrinos is in the core of the neutron
00:08:24star so the core can be cooler than the crust around it and then some heat will arrive from the crust to
00:08:33the core and we will be emitted with neutrinos so it's kind of like inverse cooling and this is called
00:08:38neutrino cooling and then in the end when the everything is cold and it enters the bottom cooling
00:08:45stage and this emission of neutrinos will depend on the internal contradiction of the neutron star
00:08:51in that nuclear matter is a bion-kion-bocquart method and you can estimate what should be the
00:08:57temperature of the neutron star at this point and this process of this neutrino carry away a lot of energy
00:09:04uh as uh one spends money uh in the casino actually all the money are gone in like uh half an hour and
00:09:31so and they call this process urka process that's why it's called there is modified and direct urka so
00:09:37there is murka and durka uh process uh i don't know murka i don't know like how here but you can call
00:09:46a cat usually in russia we call the cat murka that's why yeah uh and this is a neutron star sematic structure
00:09:55here kind of kind of a liquid work you can advise it to the two parts yeah kind of like a liquid work
00:10:03and then you have actually a solid crust with the press support and this crust kind of like the outer
00:10:09crust composition is close to the what we discussed with the white work so it's kind of like crystalline
00:10:14structure uh here of uh nuclei embedded in the lattice and then in the inner crust there are also three
00:10:24neutrons appear because the matter is more and more and more use and reach and then at some point
00:10:29there is something particular happens so the usual uh stable the most stable nuclei that we know
00:10:36they are spherically symmetric this is kind of the the most stable shape but in the very depth of the crust
00:10:43uh yeah of the neutron star this nuclei can be deformed kind of like uh rods or like tubes
00:10:52or in kind of like slabs and this resembles actually lasagna and spaghetti rice and it is called pasta
00:11:00phases inside neutron star and they can be the most stable shapes this is kind of the final thing
00:11:08and uh actually the lattice uh of the neutron star has the same structure as atomium this is why
00:11:16atomium was built for some a joke in the lattice of iron but who cares about iron when they have neutron stars
00:11:24uh so if you mention this uh crystal it will be composed of this kind of uh nucleus here embedded
00:11:32and we have this is called body center cubic lattice exactly you can see atomium and you can imagine this
00:11:38this and this is what is in the crust of the neutron star so why the crust is important uh if we have
00:11:46some system which is a creating matter on top of the neutron star so then there is a rocker
00:11:53low overflow so the matter uh transfers into the accretion disk and spies of the around neutron star
00:12:00loses the angular momentum finally falls on top of the neutron star this falling of the material compresses
00:12:07the crust and induces nuclear reactions in the crust which heat up the crust so here we have the process
00:12:13of accretion here is the temperature uh for example on the surface of the neutron star because of the
00:12:19nuclear reaction and so on you see it rises rises and rises and then because the christian process is
00:12:24on table at some point it stops this is called tuition period but okay doesn't matter accretion stops and then
00:12:32you can see the cooling of the neutron star and this is corresponds to the thermal relaxation in the
00:12:38crust of the neutron star and then we can construct the models of uh neutron star cooling so this aligns
00:12:45the models and we compare them with the observations here in the points and then they say okay this model is bad
00:12:52so this composition of the of the crust doesn't correspond to the reality and this looks better so maybe this
00:12:59is the composition of the neutron star crust and this is the composition of the neutron star crust and this
00:13:02was work that i was doing with colleagues from uh so this is where the crust is important for example
00:13:12and then uh uh we're slowly going to to general relativity effects and then in the 1973 there was observed
00:13:21one bolster uh which is late was called halstamer bolster and it was discovered in the sky and it has a period
00:13:31of uh 69 milliseconds and then later like maybe one year later again observations of this pulsar and the
00:13:39period changed by the huge amount 27 microseconds which is huge for for for because as we discussed last time
00:13:49the period of the pulsars is known down to 10 to the minus 18 or maybe sometimes 20 so like very very
00:13:57precise like enormously precise and here it changes period what what why why it is so and then uh house
00:14:06and they are they saw there is a smooth variation uh in the system so smooth variation in the time of
00:14:12pulses arrival with eight hours and this actually corresponds to the orbital motion of the pulsar
00:14:20in the binary system so imagine you have some binary system and then two new two neutron stars as it
00:14:27turns out there was a bingo and now that the another star was also newton star it's crazy two
00:14:32neutron stars in the system uh so they they rotate around each other and the one neutron star sends some
00:14:39well some impulses to you and then it goes if it moves towards you and it sends you some signals
00:14:47uh that you will see that the frequency changes because it sends you signal at this point and
00:14:52then it moves a bit closer to you and sends signal again and then you will see that the frequency
00:14:58actually decreases but then the more moves for example in my direction it sends you the signal and
00:15:04then in the system of the neutron star it sends the signal with the same frequency but because it already
00:15:10moved a little bit so then the path to you is longer then you will receive signals with a lower frequency
00:15:19this is uh just doppler effect and they observed it and then uh they calculated the orbital motion so
00:15:25on turns out that the companion is neutral star is quite the same month and then the other thing
00:15:32that they saw that actually the orbital separation of this uh binary period the gate you can see here
00:15:40in the points our observation and here is the line that perfectly describes this observation
00:15:47and that's why these people obtain noble price so uh can you say why the orbit of the neutron star
00:15:54in the gate when they have two neutron stars when they around each other there is no overflow of the
00:16:01gas so they cannot that kind of directly touch each other or interact why the orbital separation shrinks do
00:16:09you know uh good so that's why i'm uh i'm here i'm giving a lecture otherwise maybe i have no job uh to do
00:16:22so actually it's because of the emission of gravitational waves so we are now going to discuss the general
00:16:29relativity so i need to warn you that i will not really develop into details we will not discuss like
00:16:37uh time travel and so on i will try to discuss today kind of like the basics and the things that we
00:16:44are really observe in the universe so no speculations today just kind of facts uh and uh one of the tests
00:16:52of the general relativity is actually was uh this hostel taylor ulcer system so what is general relativity
00:17:01just uh let me discuss give you a brief introduction and so on so this is just
00:17:07relativistic theory of gravity so this is what replaced the newtonian theory of gravity so newtonian
00:17:14theory uh was i don't know at least left for like 300 years maybe and it was very successful in this
00:17:21in describing around and still successful you can use newtonian gravity in your everyday life but
00:17:28special relativity and then generalization with general relativity is very important uh today for us so it
00:17:36was built mostly by einstein but there was a lot of contribution from other people starting already
00:17:42from maxwell and then lawrence von kariminkowski a lot of other contributions that should not be
00:17:51forgot and it solves problems in newtonian description in particular instantaneous force on the interaction of
00:17:59gravity and by reconstruction this is geometric theory of gravity that also unifies space and time so it's
00:18:08kind of we know that we live in the four-dimensional world so to if you want to meet uh some other person
00:18:15you need not only specify the exact location in 3d but also time uh so so we'll talk about uh four-dimensional
00:18:27world but also just because it's very hard to plot something four-dimensional or higher even three
00:18:33dimensional is already harder then i will also discuss a lot about two-dimensional things just for
00:18:39visualization and it's kind of like the example of living in the four-dimensional world you can go to
00:18:46the airport park there and uh where like 100 years ago there was a famous uh set of conferences in the
00:18:55institute and a lot of famous people were there including einstein heisenberg uh planck and so on so
00:19:06it's just in the leopard park you can go there you will see this kind of picture and you'll be in the
00:19:12same place where these people were but because of 40 you will not meet them there because you're 100 years late
00:19:22uh so let me also discuss some kind of okay today there will be kind of postulates so you just need
00:19:32to believe in this uh in some characteristic of the general relativity
00:19:43first important thing is the equivalence of inertial and gravitational mass or there is a payment kind of
00:19:50third experiment of a person moving in the in the elevator or you can imagine moving in the rocket
00:19:57so if you are in the rocket and the rocket accelerates you will feel some force so you will stay in it
00:20:03it's not free falling so we're not floating around in space you will just stay on the floor you will be in the rocket
00:20:09and you will feel the same kind of effects
00:20:12effects as you're as you're standing here on the earth which apply to you some gravitational force
00:20:20with kind of the same let's say acceleration or in other words if you are in this accelerating rocket
00:20:27and you drop a ball let's say it will fall down uh on the floor of the rocket and will be described by the
00:20:35same physics everything will be the same it will be undistinguishable as you just drop the ball standing on
00:20:41earth this is kind of like the equivalence of two systems another important thing that this is very
00:20:51famous equation you know but i mean it's kind of seems uh mainstream but this is super important because
00:20:59this tells us that actually energy is equal to mass so every object that has some mass already has some
00:21:06energy or what is will be more important for us uh so in newtonian range you know that you have one body
00:21:15that has some mass another body with some mass and they're attracted to each other because of the mass
00:21:20but actually it's any kind of energy creates gravitational attraction any absolutely any so this will be
00:21:29important and the other thing is this is special relativity but the speed of light c is universal limit
00:21:36for any uh propagation information so if you have any question can we violate speed of light here then so
00:21:43no it is it just just impossible uh and here kind of like what is usually shown as intuitive feature
00:21:54or how it looks like general relativity so if you imagine yourself living in the two-dimensional world
00:22:02also like living organism cannot be in two dimensions because if you imagine some some kind of like a body
00:22:10and it has a digestion uh system so it eats something and then it's kind of like process it and then this
00:22:17goes out in 2d it will cut the body into into pieces so it cannot survive in two dimensions that's why we
00:22:25need three dimensions uh to survive and we are living in three dimensions so coincidence or not
00:22:33you don't believe me so if you are living in this two-dimensional world and there is kind of like a
00:22:39a space that you can imagine at this web or it's kind of like this issue and then there is some massive
00:22:46body you put on it it's kind of stretches the tissue in the 3d which you don't know about but it's just
00:22:54deforms the space around it you can see here for example kind of some star which deforms the space
00:23:01so you basically are moving there and it just you're not really kind of attracted to the star like some
00:23:08words for adjustment the space itself is warped or deformed or distorted that's why your trajectory will
00:23:16be banded and here's kind of in the relation in three dimensions of uh distortion of the of the space
00:23:25and time and here's some kind of obliged to show Einstein equations but uh let me tell you some kind of
00:23:33intuitive understanding of them so here t is energy momentum tensor it's what i told you that any kind
00:23:40of energy momentum whatever can create this uh that can disturb uh space and this is Einstein tensor that
00:23:50describes the geometry or curvature so energy creates curvature or energy uh justifies or kind of describes
00:24:01the geometry of the geometry of the of the space around and here's geometry of space time governs actually
00:24:08the orbit around massive body so if there was no body and for example here you would move on this
00:24:16trajectory for example and this is kind of like i will see the balance if there is a uh some star but just
00:24:23because the space is deformed you would think that you're moving just in the straight line but actually
00:24:31because of deformation of space your trajectory will be banded and you will move here so this is uh
00:24:38the beauty of uh of general relativity and then another uh important thing that uh that describes actually
00:24:50that how uh they are pulsar is gravitational waves so Einstein derived in equations and published them in 1950
00:25:00and then even before actually Heiveseid and Paul Carré already proposed these ideas but
00:25:06Einstein kind of like in 1916 he transforms his equations to simplify them a little bit and obtain kind
00:25:13of a wave-like form like in electromagnetism we know the maximum equations and we know that the
00:25:20life actually is a wave and also particle yeah very convenient uh we can transform these equations so they look
00:25:29like wave-like equation so there is a wave-like solution of the equations which is now called uh gravitational
00:25:37wave so there is a propagation of such a wave corresponds to the distortions of space-time and
00:25:45it can only be of quadruple form so mathematical unsupervised quadruple is because we have all this
00:25:52equation that i showed before in the tensor form but you can also kind of imagine this uh
00:26:01this tissue of the of the spacing diamond here so if i change the side of the body
00:26:08of the body we do not change the size of the body here the trajectory will be the same in other words
00:26:16if i substitute the sun in the center of the solar system to the black hole it will still rotate on
00:26:23the same orbit you will not feel it okay we will see it but like kind of if i don't look what's there
00:26:28i will kind of have the same feeling and we will have the same rotation so so it doesn't matter what is
00:26:34kind of the size so if i do kind of like this will be called kind of monopole modes so i have kind of
00:26:42pulsation here it will not really create any ripples on the on the surface uh of the space-time
00:26:52the same thing if i do this will be called dipole movement if we move right here and there it will also
00:26:59not create something because you can change the frame of the movement and it will not disturb you
00:27:05but if i go so here's kind of like dipole if i then break spherical symmetry and i will have something
00:27:18not spherically symmetric or i will have some quadrupole modes for example i will squeeze the star
00:27:24here and then there this actually will create kind of distortion of this form in in the space time
00:27:32well mainly in the space you can see them here the space will be stretches in that way and then that
00:27:39way and it's kind of like will be pushed here and then here so this this is kind of visualization
00:27:47of a gravitational wave so if gravitational wave passes through me it will be first kind of very
00:27:54slim then it will be very fast and then they will be short and fat and then it will be tall and slim so
00:28:04perfect hopeful and then and and so on uh exactly this quadrupole moment can be created if we have
00:28:15two moving compact stars so this is not fair if you can see and they can emit gravitational waves
00:28:23and this is what causes the decay of the orbit and describes how fair uh full search absolutely perfectly
00:28:31and it was the first indirect uh test of uh in the indirect detection of gravitational waves and a very good
00:28:41test of the general relativity that's why noble price uh given to these two guys this is kind of
00:28:48visualization here and you have two compact objects moving around and you have ripples on the surface
00:28:57of the space yeah this is uh yeah kind of gravitational wave propagates here with the speed of light
00:29:05uh c and we know when we already have kind of direct observational uh proof that they also propagate with the skin of land
00:29:15i will discuss it a little bit later so it was an indirect detection of gravitational waves
00:29:21waves and as you may heard the direct detection was in order so how to detect these waves as i discussed
00:29:31on my example if gravitational wave passes through us you kind of could see it's very small very big waves
00:29:39actually uh actually i i might forgot to discuss that even an Einstein didn't actually believe in this
00:29:48solution and the funny story that he wrote the paper proving that there are no gravitational waves
00:29:56and then this paper went to the referee referee found a mistake in Einstein paper
00:30:03and wrote to the to the to the uh to the journal that there is a mistake and actually there could be
00:30:10irritation only Einstein was furious he said i i i'm sending you the paper to publish not to refer it i
00:30:17i'm i mean but in the end the referee knew co-author of Einstein and then they agreed that indeed there was a
00:30:27mistake and could be a gravitational wave but people didn't really kind of like pay a lot of attention to
00:30:34them uh until a certain point so how how to detect them uh again so we can use interferon so we know that
00:30:45the light can be presented as a wave and there is called interference patterns so if you have uh two
00:30:53waves and they arrive in phase they can enhance each other so here are the two waves and they're in phase so
00:31:00they can amplify kind of the signal and this point and these points you have you will see some interference
00:31:07patterns and if they are perfectly out of phase you will have no signal so again they cancel each other
00:31:14this is called interference and already like in the 19th maybe 18th century michaelson invented
00:31:20one of the most famous interferometers it's a device to measure the distances with interference this
00:31:27file called interferometer and it allows to detect super precisely the location of in this case mirrors or
00:31:38actually any distance can be measured super precisely and in this device that was built in Italy and in USA at
00:31:46first they measure the the distances down to in one of the thousands of the size of the proton
00:31:55i mean if you if you say like to to any physicist this number will say i don't believe you this is this is
00:32:01just i mean you have a lot of you know like thermal movements small vibrations this is just impossible
00:32:08but people are deep it and that's why we have a mobile price again so how you can how this interferometer
00:32:16looks like so you have some people the light to the laser it goes to one mirror and here is reflected to
00:32:24another mirror and then here you will see so there is kind of some light it goes to one mirror and then
00:32:33it goes back and you see it reflecting and it goes to the screen here uh to the right and then if waves arrive
00:32:43in place or out of place you will see some image on the screen or you don't see it so if you calibrate
00:32:50your detector to be for example uh in place and that they will have some image over your out of the
00:32:56place and you have no image and you kind of the system is perfect no vibrations around if gravitational
00:33:03waves arrive it starts to basically stretch the the space in different directions and you will see the
00:33:10mirrors moving here and there and you will see appearance and disappearance uh let me play it again
00:33:17so here you will see the mirrors moving so you know gravitational waves you see mirrors moving because
00:33:26the space stretches and you will see appearance and disappearance with some frequency the image
00:33:31on this plate this is how gravitational waves now are detected and uh this is uh now existing
00:33:41you know telescope telescope near pisa so these are tubes with lasers they are just like four kilometers
00:33:48uh long uh very long tubes there was there is also ligo and ligo in u.s uh camera in japan uh there is a
00:34:00future space detector so in space you can build on like really really uh long ones so you have a better
00:34:07signal and so on future space detector and this is future einstein telescope that will be built in
00:34:14collaboration of belgium german and netherlands and maybe you recognize this feature and this is
00:34:19balunia maybe it will be there uh it is i think it will be decided next year it was kind of we'll see
00:34:29how it is with the budget cuts and so on
00:34:37but hopefully yeah this is a big thing now in in astrophysics detection of gravitational waves
00:34:44and then 17 of august in the 2017 there was a maybe the most important
00:34:52event in astrophysics in like 30 years or something like this
00:34:55we saw we detected gravitational waves and electromagnetic waves from the same source
00:35:04at the same time so here you can see observation of haval telescope and appearance of sun brightsport
00:35:12in the background of the galaxy and this was and here you can see the frequency in the gravitational
00:35:19wave detector here in the detector here is the time before merging of two neutron stars here is a simulation
00:35:26uh from gsi the german institute uh you can see the two neutron stars carliding and they mean a lot of
00:35:37gravitational wave you can see the signal is a frequency rising because it's like they move closer
00:35:44closer the orbit is smaller and smaller the signal radius and amplitude is higher and higher and this
00:35:50was detected in light and this is the big thing because as i said it's detected in different light
00:35:57it was detected in the radio in optics in the x-ray in gamma and in gravitational waves so it was a date
00:36:07of birth of so-called multi-messenger astronomy so we are now living in the era of multi-messenger astronomy
00:36:18uh let's move further and there was a one question about uh that's why i inserted this slide so
00:36:28exactly during the merger of neutron stars a lot of heavy elements for example gold is created well you
00:36:36have neutron stars means you have a lot of neutrons then you have a huge temperature because the
00:36:42gravitational energy is released uh in temperature so and this led to the active neutron capture so
00:36:49if you have here the the ejecta from this merger that i showed before it first goes to kind of like
00:36:57most stable elements of the node here will be iron somewhere here but then it will start to capture
00:37:04neutrons so this is number of neutrons so this is number of protons this is monster so we'll have
00:37:10it will start to capture neutrons from here then emit electrons and move here and then so on so it's kind
00:37:18of like uh in the case uh here so so yeah you you will see here the movement here the evolution of
00:37:31nuclear monster because of the a lot of neutron structures you move here to where you carry elements
00:37:37and then these uh extreme conditions you can create a lot of load for example one event of neutron star
00:37:45merger can produce 10 earth masses of gold so if you have neutron star merger nearby you can solve
00:37:54the poverty problem in the world uh the poverty problem in the world uh in my eyes of uh naive uh economist
00:38:02but uh physician yeah uh where you will not create gold is when you have merger of black holes
00:38:12because when you have mergers of black holes you will just have black hole uh so and actually the very
00:38:19first gravitational wave signal was in uh 14th september 2015 and it was merger of two black holes with the
00:38:2936 masses and 29 uh dollar masses and you can see kind of the simulation and here you have the signal
00:38:39kind of on the detector with some frequency which will increase and become closer and closer and that will
00:38:45be the ear at that point so just enjoy a big simulation you will also see gravitational waves it's kind of blue
00:38:55there and it's now they will collide and merge to one big black hole there are kind of nothing is created
00:39:04because as we'll discuss later nothing escapes um black hole uh and for this detection these guys receive
00:39:14nobel prize in 2017. here's uh one black hole and we stop emitting uh gravitational waves here
00:39:25and uh here is exactly our lecture three about black holes so what we can create with uh uh stars with a
00:39:34big mass it's already 45 minutes okay i'm quite late uh so okay anyway
00:39:45so what happens when two neutron stars reaches critical mass or what happens if core collapse supernova
00:39:52is is not successful or we have kind of a failed collapse uh if we surpass some limit that we discussed
00:40:01but nothing can escape uh the collapse even light and this was discussed actually already in the 18th century
00:40:11by uh by uh john mckel and uh pierre laplace and they concluded just from the newtonian theory that could exist
00:40:20some objects which will bind everything even light so in other in other words the escape velocity from such objects
00:40:30will be equal to the speed of uh to the speed of light so if you have some cannon on the mountain
00:40:37for example on earth you know that if you if you here uh should uh shoot the ball and if you do it very
00:40:45slow it will fall on the ballistic trajectory to do it a bit faster it will go here but at some point
00:40:52you will enter the orbital velocity or first cosmic velocity and it's very easy to obtain it because here
00:40:59basically your centrifugal force will be equal to the gravitational force and then you can calculate
00:41:06the uh this velocity but to escape from the from earth or you want to go to the infinity you actually
00:41:15need to double your kinetic energy or because uh velocity depends on the square root of kinetic energy
00:41:23you need to you will have your escape velocity which is square root of two of cosmic velocity and
00:41:29then we put uh to this like 2g well okay just this uh equation and escape velocity of earth is 11
00:41:38kilometers per second so for example if we want to launch some satellite infinity like voyager
00:41:44we need to reach this velocity from sand is higher and from the black hole is equal to the uh
00:41:52speed of light is uh 300 000 kilometers per second so if you put instead of b here you would
00:42:00speed of light then you can obtain what should be the radius of this body with a given mass and this
00:42:08is it what is called now flashing radius or the size of the black hole or event horizon uh radius
00:42:19uh so in the black holes the space time is ultimately deformed and bent a line way around the black hole so
00:42:28if you how you can detect the black hole you cannot see anything inside the black hole you can only see some
00:42:34signatures or what is going around so here for example if you have some star behind the black hole
00:42:42the light will go there and it will actually close into the to the well and then arrive here
00:42:48and you will see observed position on the star actually will be more to the left and it's already
00:42:55just actually at the same time as einstein published uh his general relativity carl schwarzel
00:43:04almost in the trench during the first world war he derived solution for gravitation of fields surrounding
00:43:12spherically symmetric body which is now called schwarzen black hole and at that time it was not called
00:43:18like this and people didn't really understand what is what is this black hole but they had already solutions
00:43:25with some singularities uh and it was also because by big scientists like edicton and landau they actually
00:43:34didn't really believe in black holes and they thought that there will be some force which stop the collapse
00:43:40and the black holes will never be there and it's uh only after generational shift so it's kind of like
00:43:48in the 60s already the black holes became a thing so the radius of the black hole with the mass
00:43:54of earth will be just nine millimeters so if you compress earth to the size of nine millimeters you can
00:44:03create a black hole from the sun the radius will be three kilometers and i remind you that the radius of
00:44:09the neutron star is only 12 kilometers and it has okay all of the same mass of the sun so it is that's why
00:44:16it's a kind of like perfectly compressed object if you compress it a little bit more then you have a black
00:44:22black hole then uh later after schwarzer in 1939 oppenheimer and schneider showed that you have collapse of the gas spheres with zero pressure
00:44:33so we discussed that we have a sun there in the dermal pressure or it can be pressure of radiation for
00:44:40bigger star that prevents the collapse kind of like sustain the uh hydrostatic equilibrium but if you have zero pressure
00:44:50the gas should collapse in the point which is called black hole in 1963 care obtained a solution
00:44:58if the body is rotating it's not just like staying still it's also rotating and uh later
00:45:04john biller introduced the term uh black hole and around this year in 1964 that there was the first
00:45:13indirect observation of a black hole in the system signals uh x1 so you can get the first
00:45:21system detected in x-ray in this constellation and this is now the chandra it's kind of modern picture
00:45:29of it so in this uh black hole there are a lot of interesting things going on for example there is a
00:45:36gravitational redshift or a time dilation you can actually feel the same so if you are close to the
00:45:42black hole average in like space time is uh worked and for example in the interstellar movie i don't know
00:45:50if you if you saw or not uh they arrived to the planet near black hole and for them kind of the time
00:45:58was going slower than for for daughter of uh mcconaughey and that's why when he was uh he kind of like
00:46:07saw her after she was already uh grown and there is another thing with this time dilation is kind of
00:46:13like twin paradox if you have someone who can travel close to the black hole leave there for example some
00:46:20twin and then arrive back to earth the other will be uh older so and there was like an experiment that
00:46:28the one twin uh went uh on the international space station and because he experienced acceleration there
00:46:37and that he actually was i think eight milliseconds younger than another one don't go to this
00:46:47uh and it can be interpreted in different ways so it can be like uh doppler effect or it can be like
00:46:56band dilation uh change of line frequency in this potential world actually corresponds to the slower uh
00:47:06time uh moving uh the other thing with the black holes uh that it has no hair as uh was said by john
00:47:16leader there is kind of a theory and the black hole has no hair for example fineman didn't like it
00:47:23because he thought okay it's it's too much uh this phrase uh but it actually corresponds to the fact
00:47:30that we can describe black hole with just three parameters it has mass spin and charge but charge
00:47:39actually if you have charge in space it's possibly neutralized so actually you can forget about charge
00:47:44because it's just math and spin nothing else no information can escape black hole so we're actually
00:47:51disconnected from it so everything that is going on inside the black hole we can't know what is going
00:47:57there and if you put microwave there or plant or like potato everything that has color shape a lot of
00:48:05nice things all information will kind of in the PR in the black hole and we never know uh what is there
00:48:13uh i like uh this kind of cartoon that there is all come with his razor and kind of cutting the hair
00:48:19from uh from black hole
00:48:23yeah and in the center of black hole we have a singularity but uh we don't really know what is
00:48:30inside the singularity because to describe this point we need to connect general relativity and quantum
00:48:37field theory which are still not unified uh even even nowadays there are different theories like drink
00:48:46theory supersymmetry and so on but still they are uh not developed enough uh to really set this uh to
00:48:53describe our world uh so we don't know actually what is in the singularity point uh of the black hole but
00:49:03actually general relativity is enough to describe what is outside and actually what we see uh in the
00:49:09telescopes so how can we see black holes first of all if the star just follows and disappears in the
00:49:19black hole so if there is kind of was something and now it is nothing you can imagine that it became a
00:49:27black hole so this is kind of a collapse on the star here and it doesn't create any kind of object in the
00:49:35center it just kind of faint or kind of failed supernova with some vision is here but it's really not
00:49:43very bright and here an observation from how those space telescope there was a star of 25 i think solar
00:49:49masses and then at some point like it was observation in uh 2007 you know 2015 just it appeared
00:49:58nothing there no supernova no gas shell should be black hole another thing is binary systems and this is
00:50:07how the first black hole was observed so if you have uh some material falling on the black hole just
00:50:14because it loses a lot of angular momentum it starts to heat up and emit in the x-rays and that's how you
00:50:21can liberate like from six to 40 percent of uh of uh mc squared it's uh much much more efficient than for
00:50:31example nuclear reactions nuclear reactions will give you like 0.1 percent uh in here you have like 40 percent
00:50:40uh and this is kind of foster from nathra uh if word in gravity so this is how we can we detect uh
00:50:48uh black holes another interesting thing with black holes is uh for example if you have not spinning
00:50:55black hole this uh the stable orbit the last stable orbit that we can describe just by solving
00:51:02the question will be uh the rapid so it will be three trusted radios so everything coming from outside to
00:51:09inside this orbit will eventually fall on on on the black hole so this will correspond kind of to the
00:51:15inner edge of the accretion disk here's kind of gas flow around and then if the black hole is spinning
00:51:23it's kind of like accelerates the gas kind of boosts it's called kind of like uh frame tracking effect
00:51:29effect so it kind of helps the gas to rotate around and actually that's why gas can survive so the orbit it
00:51:36can shrink a little bit and actually you can go down to 0.5 flat sheet radius if you have the maximum
00:51:44possible rotation so that's why spinning black hole becomes kind of smaller
00:51:49and then if you have a light uh coming the the photon sphere or kind of like last but it's actually
00:52:01unstable orbit around uh black hole uh like is located at 1.5 flat sheet radius uh here and everything again
00:52:11coming from outside into this every photon coming inside so this is kind of photosphere so you can
00:52:18imagine that you have some lights and you're standing here and then you emit uh in different
00:52:24direction the light everything that kind of scatters inside this photon sphere will fall onto the black
00:52:32hole and even this so this kind of critical point these photons will orbit the black hole but eventually
00:52:41this orbit is very unstable so very small every small perturbation will leave to the fact that uh photons
00:52:47fall on the black hole so this kind of leads you to sound angle this is called like alpha capture
00:52:55so this is what you will really see like if you reverse the situation and there is something emitting
00:53:00the light for example stars here so this this photon will go to you and reach to you this photon will reach
00:53:09you but for example if photon goes inside this photon sphere it will fall into the black hole that's why
00:53:16black hole kind of cast some shadow create some shadow uh on the black hole and here's kind of the image
00:53:23of the photon sphere and this is the shadow uh you really see and this is kind of angular size with
00:53:30the shadow on the black hole you can see here this is travel on black hole and this is actually well quite
00:53:37new like eight years ago we uh this is simulation i will show you later the real observation
00:53:47oh but if black hole rotates it again can help uh the light to escape so if you have some rotation of
00:53:57black hole like this you have some photon that can escape which which was closer to the black hole and
00:54:03here if it wasn't moving here just because there is a frame drive so it kind of stops problem from
00:54:09moving and it falls in the black hole that's why it can be asymmetric like this and this is a simulation
00:54:18so this kind of how could we see a rotating black hole without rotation would be just here with
00:54:24rotation one edge would be kind of flattened uh this is black hole from the fellow i know have you seen
00:54:37okay great so this is black hole from interstellar it has an accretion disk here you can see the other
00:54:45edge of the accretion disk is kind of because exactly of this bending is shown here so you can imagine this
00:54:51kind of like the space is kind of disturbing this this is the other side of it you see that it is
00:55:00uh not perfectly spherical exactly because of the rotation what you can see and what is unrealistic here
00:55:07that both slides are kind of have the same brightness because of the movement here of the gas
00:55:14actually the one side should be brighter because of the doctor being in and about christopher i mean
00:55:21so a lecture of uh keep torn discussing this he told that christopher nolan wanted to make it a kind
00:55:28of a bit in there and it's kind of like like a human watching the black hole it cannot really recognize
00:55:35what is bright and so on but here is kind of from the article of torn authors black hole in interstellar this is
00:55:45doppler shift and gravitation ray shift and this is how it will look like in the reality
00:55:53with all the physical effects but if you look on top of the black hole so if you look and you see the
00:56:00disc around what you will see is actually what was obtained just differently with the m 87 black hole and this is black hole in the center of our galaxy
00:56:12such as a with the interferometry as we discussed before in radio waves we can actually do in the center of the galaxy so just give
00:56:22you the feeling of the level of magnification it would allow us to see a telling ball on the moon
00:56:30and this is what is the level of the scene of the black hole virtually here we look on top so there is
00:56:36no kind of like crossing here if we were in the equatorial plane on the black hole we would see this
00:56:42accretion disc but just because we are on top we see accretion disc here and the one kind of side can
00:56:48be bright in another exactly because of the rotation of the black hole uh and here is kind of like our
00:56:56understanding that in the center of every galaxy we have a super massive black hole with like millions or like
00:57:04tens of billions of solar masses and they can actually kind of accretion disc here and they can launch some
00:57:12jets if we're looking from the top we'll see kind of blasters we can see quasars this is all kind of artistic
00:57:21view and this is a real observation we see these jets here here and there this also corresponds to the black
00:57:28black hole uh in the galaxies and here the star moving in the center of the galaxy so kind of like
00:57:36here you will not see the black hole but just because we start moving around and there is somebody that's
00:57:43strongly uh gravitate we can deduce kind of what should be the math of the black hole in the center of
00:57:50our galaxy and here's kind of comparison this is m87 star and the size of the shadow of the black hole
00:58:00this is a corresponding location of voyager the orbit of gluto and this is the side side of our
00:58:09black hole which is like a thousand times smaller than in m87 galaxy the other thing that we can use is
00:58:17gravitational lensing so the sun because of the bending of the light we can see this kind of like
00:58:24einstein beams uh or something like this and then we can we can assume that there is a black hole there
00:58:34uh or there actually could be primordial black holes could be uh created in the very beginning of
00:58:42the universe because we had all these kinds of fluctuations so we could have black holes from
00:58:48plant scales from 10 to the minus eight kilograms two thousand of solar masses created and this black
00:58:54holes could be floating around in space around us but actually only black holes uh larger than uh with
00:59:03masses higher than 10 to the 12 kilogram would survive exactly because of the flocking radiation so i will just
00:59:10give you first kind of simple explanation so the funny thing nothing can escape black hole until you use
00:59:20the quantum mechanics it's kind of like a magic thing that helps a lot so there are a lot of different
00:59:28interpretation oh yeah sorry so what i was wondering is that so when you usually see the image of this i can
00:59:51going into the satellite you show there you have like one accretion disk that's going like this
01:00:00and then you also see another sort of other one that's going like that is that actually the light that's
01:00:07of the equation is that behind the black hole that's getting bended and that makes you see it yes yes
01:00:13this is this is this is what uh i was trying to describe but there is no like another accretion disk crossing this is the same
01:00:21accretion disk just because you can see the other side of the black hole you see kind of like it's on top and
01:00:28in the bottom because in the same so there is a photon emitted there but it is blended and you can see it here
01:00:34again going here and and there yeah and this is you see the crossing just because the accretion some part of the accretion disk is in front of the
01:00:43yeah okay just one thing i was wondering is like why do some rotate and other zones
01:00:50uh well most of the black holes should rotate well actually i have a lot of accretion disk and i think
01:00:57i discussed it a lot actually like if you have some movements even if it's like like random movements
01:01:05in that you will have some net angular momentum anyway so we cannot like have all the particles perfectly
01:01:12canceling movement of each other so as the final kind of star will stay still you always will have
01:01:18some movement on the star and then it collapses it has some kind of i i discussed it it's like in the
01:01:24in the figure skating that kind of have a big start and rotate slower but then if you if you do like this
01:01:30and you're kind of like rotates like this you will rotate faster and this is for how black holes and
01:01:37actually the records we see they also rotate very fast and this black hole rotates like 60 percent of
01:01:44the uh this one 60 percent of the maximum possible uh while so a lot of black holes uh rotate and you
01:01:51have some kind of everything falling off the blank hole it also can give that angular momentum to the
01:01:57black hole and spin it down thank you yes um okay let me quickly i don't know if you're interested in
01:02:08hawking radiation let's imagine that you ask me questions about this uh yeah so there are a lot of
01:02:15interpretation how black holes can emit and actually they can evaporate one of the thing that you can
01:02:23imagine that there is some vacuum around black hole but in quantum theory vacuum is not like essence
01:02:30that actually some of these some virtual particles particles are created here and there so it's kind of
01:02:35like everything is boiling and you can imagine if one particle is created on one side all the event horizon
01:02:42and the other on another side is kind of like normally they would annihilate and there will be nothing just
01:02:49kind of like you take some energy from the vacuum and then return it back so energy there is energy
01:02:55conservation but then if one is there one is here one can be radiated another will fall inside the
01:03:02black hole so as we could see the black hole will radiate the particles this is one interpretation
01:03:09but actually the problem is it that the black hole emits particles or photons with the wavelengths
01:03:19the same on the size of the black hole so it's not some local effects you cannot imagine that okay
01:03:24lens horizon is big and it's kind of like locally particle here particle here one goes there one goes
01:03:31in the black hole actually the wavelength of the light is the same on the size of the black hole so it's kind of
01:03:36like the black hole radiates itself uh photons and it has some uh temperature actually very very very small
01:03:46here hawking himself described that kind of black hole scatters the vacuum and then it can create some uh
01:03:56emission the other thing to to think about this is kind of like everything what is is confined inside
01:04:02the black hole but something can funnel outside the black hole and then you can also obtain the right
01:04:10formula for the spectrum of the black hole or black body spectrum uh what is important
01:04:17that black hole with the masses of 10 to the 15 grams will evaporate because they emit
01:04:24in the same time as the age of the universe so everything smaller than this number should have
01:04:31been evaporated already so if some black hole was created in the beginning of the universe
01:04:35it will already be gone if it is bigger for example solar months were cold it will live basically
01:04:42forever and this emission is negligible uh so this is all i wanted to talk about
01:04:50so next questions
01:05:05thank you for listening the topic is hard and maybe the information was quite dense but
01:05:11any any kind of questions would be happy to answer um i have a question about how do you measure our face
01:05:19because since the two ways deal each other you just consider that if you don't have a signal they are
01:05:25our face but then is it not important you also know if even if they are that they are the same and
01:05:35they know each other is it not important to know how they are finding itself generally like we can have
01:05:42small waves or big waves but is it not important to sit and identify those waves is there a way to do
01:05:49i mean if they have the same wavelength they will just uh cancel each other and if they are a little bit
01:05:57like i showed you just uh one or zero like kind of uh one and another it can be something in between
01:06:04then you have a little bit of the signal so we have some kind of inter you can google just interference
01:06:10you will see kind of like uh for example you can have like a circles with the higher intensity small
01:06:16intensity and the density will drops and then rise again drops and rise again it's kind of like a waves
01:06:21you could spin or not but can they also kind of shift to spinning and not spinning or it's just like
01:06:38they're always they're spinning or not spinning you know what i mean uh it's yeah i understand the
01:06:44the question it's very hard i mean the black hole is kind of super massive and if it started to rotate
01:06:54it would be incredibly hard to stop its rotation you need to spend like enormous amount of energy
01:06:59to stop its rotation then to start to rotate to another side so it's it's it's very hard you can maybe
01:07:06decrease it's it's it's rotation if you will agree the particles which will orbit like counter uh for
01:07:15example like it will be called uh retrograde uh movement on the orbit you can maybe decrease a little
01:07:23bit but to really stop like all and then start to rotate to another like um unless you are god
01:07:30it's very hard it's very hard to do but in principle i mean there is no violation i mean if you have
01:07:37just a uh conservation of angular momentum yes
01:07:53um i have a question regarding the gravitational waves so you told us that
01:07:58it was already like one century of theory and now we we are able to detect it and validate the theory
01:08:07so what is driving the the current's new uh experience uh is there an application
01:08:16or some more of the issue to validate yes yes uh great question first of all i mean with these uh black
01:08:25holes we can know the masses on the black holes that they collided okay we know kind of the sum of
01:08:31the masses with with some models we can distinguish but not perfectly so this allows to understand uh
01:08:38which masses of the black hole are observable in the in the universe which masses really exist in the
01:08:44universe and uh kind of build uh some population synthesis models for example you take 10 stars and then
01:08:53you do the stellar evolution and then will they collapse to the black hole which mass of the black
01:08:58hole will form and then you can uh uh compare it to the to the observation on what is the mass distribution
01:09:07of black holes and so on another thing which is maybe more interesting i mean at least for me
01:09:13is when you have neutron stars because then you have also a signal from the neutron star like electromagnetic
01:09:19signal and you can have much more information and then you can obtain like the strict limit what is
01:09:25the maximum mass of the neutron star and then equate so uh the thing that i showed in the very
01:09:32beginning so this this gravitational wave event is counter so if you have a lot of them probably we can
01:09:41kind of like have a smaller quarter with a lot of statistics and then we can better constraint
01:09:47observation and we have one here or here and so on and so forth so this is uh really important uh for
01:09:56us but unfortunately we've had only one event and we're waiting for for another
01:10:03great question
01:10:07hi uh thank you for your presentation um so the angular momentum question led me to a thought
01:10:16when a merger of black holes occurred so as i understand each black hole has those uh three
01:10:25characteristics and merges into one so a lot of information is lost i was wondering where that
01:10:32goes my initial thought would be that the the information is lost as gravitational waves can you
01:10:39say that it's at first this much uh i mean they emit gravitational wave and uh lose kind of some energy
01:10:48but i mean one black hole and another black hole they described with the same set of parameters
01:10:54and the final state you also have angular momentum in this state so you can just have a you know
01:10:59some of the angular momentum and you can obtain the final angular momentum so you don't lose
01:11:03a lot of uh real information uh real information so it was already described as a system before they
01:11:10emerged yeah i mean i mean each black hole has kind of mass in angular momentum and then i mean you
01:11:17don't have more information about them and final state has the same set of parameters so you don't lose
01:11:24color of black hole or shape of the black hole because you know it's perfectly spherical and it's black
01:11:30okay thank you uh i have a second question about uh accretion disks so you mentioned that accretion
01:11:40disks can liberate huge amounts of potential energy can you go over that a bit so you mentioned that it
01:11:48was super efficient and i don't really understand what you mean by that so if you have some let me yeah
01:11:57if you have some object moving from the infinity or for example in the from this star and it falls
01:12:03into the potential well here in the gradation it has a huge like it moves actually here with the light
01:12:1240 percent of speed of light or something like this and then it can radiate it can you have one
01:12:18particle it collides with another and then it radiates a lot and then all this energy it basically
01:12:25goes into the radiation of photons uh from these particles so if you have something and you drop it
01:12:32on earth you'll feel some heat here well if you are super sensitive but if you if you drop it from the
01:12:40black hole you'll you'll feel like a lot it actually will destroy a lot of things around and so on
01:12:46just collision so the efficiency we're talking about is specifically the creation of thermal energy
01:12:58due to the massive falling yeah from you can create this energy just because the the particle has had
01:13:04some mass and that can be kind of liberated when it's attracted just gravitational energy liberation
01:13:12okay so it's uh just the acceleration yeah it's kind of yeah it's yeah okay thank you
01:13:30yeah i just had another question about the loss of information it is um it's like the walking radiation
01:13:37like when the the radiation doesn't really come from the black hole right it's gonna give you information
01:13:46of what's inside maybe it gives you information about how many particles of interference near it but
01:13:54let me really give you like you bring makeup for the loss of information um of things going to the black
01:14:02holes right yes yes great question this is one of the possible solutions of this energy loss paradox that
01:14:11so so the paradox is because kind of like all the information is lost in the black hole for example
01:14:17i don't know the the size of the microwave that uh fall into or kind of like uh some magnet that was
01:14:24on the microwave and so on i don't know uh everything like this and then what black hole radius is kind of just
01:14:30like black body spectrum it's it's just like black body there's kind of no more information there
01:14:38but there there is kind of a thing that maybe these photons kind of particles are correlated with each
01:14:45other in some way that information is encoded there could be yeah one of the one of the thing maybe
01:14:52this information is encoded on the surface of the black hole all information was kind of radiated when
01:14:58something fell uh on the black hole so there are different kind of i mean with the black holes you
01:15:04can have a lot of these felt experiments you can play around with your mind uh yeah so and also just
01:15:10one more thing also it would be weird to think that a black hole could evaporate you to that because in the
01:15:16radiation the whole generation really the black hole gains a particle because one falls inside there's a
01:15:23radiation there's a radiation radiation from the twin particle that stays outside of it so it isn't losing
01:15:30material does it it is losing because in this uh kind of naive interpretation the particle that falls in
01:15:39the black hole kind of has negative energy it's kind of just a kind of mathematical trick what we see
01:15:45is the black hole radiates the particle and that's and that's and that's it it doesn't gain the particles
01:15:52from vacuum black hole doesn't work to create the particles yes so it doesn't work and then one of
01:16:00the particle is lost so it loses uh some work so that's why it's kind of radiates uh outside and the
01:16:08other the force kind of okay it may be no such thing it's just kind of like naive explanation of this
01:16:15thing if you think of the tonally some kind of particles inside the black hole and the one which kind of
01:16:22has a wavelength on the side of the black hole kind of tunnels outside who kind of escapes in the
01:16:27quantum mechanical process then you just lost it
01:16:37yeah there will there is a one for you
01:16:38it's a very specific where everyone questions and like infinite time skills but um if the if the speed of
01:17:01of objects in the universe move at different uh times so the universe is standing right so if they
01:17:09move at different speeds and the black holes will pass things eventually will they absorb everything
01:17:17in super infinite time skills uh yeah i mean what is the end of the universe this is the question
01:17:26basically all black holes absorb everything again yes they will absorb a lot but not kind of like
01:17:35uh everything i think some of some of the things will be will escape because basically all the space
01:17:41kind of like is expanding around the universe is expanding the black hole is some space that kind of
01:17:48space point it's staying there and everything around is expanding it cannot reach maybe some other things
01:17:57i mean if they they move there is kind of like a proper motion of the black holes but there is also
01:18:04expansion in the universe so if i'm like near the one black hole so the one with another black hole kind
01:18:12of moving away from me just because the universe is expanding it's not kind of like it itself is moving it's it's
01:18:20kind of like you can imagine this uh 3d cube that i had somewhere uh i had it's yes
01:18:34yeah and you can uh take it and you kind of like stretch it into into different sides so this
01:18:40point will kind of stay still and another will expand but if you move in the frame of reference
01:18:45in one point another will expand uh in the end uh indeed kind of like uh they will stay like some
01:18:54white wars for example can leave for a long time because they will not uh go to the they will not
01:19:00become black holes so we're kind of like floating around there will be some particles still escaping
01:19:06so i mean there will be a lot of black holes for sure but uh not everything will be in one black hole
01:19:12it depends also because i mean there are some theories that universe is expanding and then it starts to
01:19:17contracts and then it's kind of everything falls to to one point but and i'm not discussing cosmology
01:19:23today and so on but you can read about this uh
01:19:36yes thank you we saw that uh two rotating black holes or whatever they are losing energy by creating
01:19:44plantation waves but is it so that uh a black hole spinning on itself is also somehow dragging
01:19:54by the dragging effect also the the space time around it is tracked a little bit uh you know it's nice
01:20:03moving here there yeah but the black hole doesn't create a sort of uh dragging of space time around
01:20:10itself yes yes it's kind of like drag but it doesn't create uh gravitational waves
01:20:17yeah well that i understand but still is space time actually the beat with the uh
01:20:24with the rotating the rotation of the dark hole yes yes i exactly discussed this uh
01:20:31uh here yeah because of this dragon you can actually shrink the last stable orbit to kind of like
01:20:41help the barn because we rotate around the black hole so the flattened red hole kind of shrinks
01:20:46so it's here so it's exactly kind of brand joining you're on
01:20:55okay if you get some more questions we can thank a lot to nikolai for this lecture
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