A few minutes before sunset; the sky is dark red. Carla, Man, Peter and Ferdinand are sitting around the campfire. In about fifteen minutes supper will be ready.
“Last night we talked about the origin of our universe. How will the sun and our earth end?”, says Ferdinand.
“In a book on cosmology, I have read that about 5 billion years ago the sun has arisen from a huge hydrogen nebula, that – in the course of half a billion years – has been squeezed into a core under the influence of the mutual gravity of the particles. Due to this concentrated high amount of mass of the particles, the pressure and temperature have been raised so high that a continuous nuclear fusion has started in the core of the sun, whereby Hydrogen nuclei transform into Helium nuclei. This process of nuclear fusion in the interior of the sun will remain stable for about 10 billion years; the sun is now half way this stable phase.
During the nuclear fusion in the sun, a small part of the mass of the Hydrogen nuclei is converted into radiation, wherefrom we see and feel the light and heat radiation today on earth. By the sunlight and this heat, life on earth is possible; otherwise the earth's surface would be too cold for the living humans and animals.
Due to the constant loss of mass during the nuclear fusion, gravity in the interior of the sun decreases slightly, causing the core of the sun to swell slowly, because the pressure by the nuclear fusion remains unchanged and the compression under the influence of gravity decreases slowly.
After 10 billion years, most of the Hydrogen in the core of the sun is consumed as a fuel, and therefore this way of nuclear fusion will slowly come to an end. In the interior of the sun, the radiation pressure due to the nuclear fusion will decrease, and gravity causes the core to collapse, whereby the temperature in the core will increase dramatically. In the layer around the core, not all Hydrogen is consumed, and the nuclear reaction will continue in the outer layers of the sun. Due to the rapid collapse of the core, the temperature in the layers around the core is much higher than in the original core and these outer layers will swell enormously – the diameter of the sun will increase by 200 times – and thereby the solar radiation will increase many times. Due to the much larger surface of the sun, the sunlight will be red: the sun will become a red giant . The magnitude of the sun becomes so huge that the planets Mercury and Venus will be swallowed; the calculation model is uncertain what will happen to the Earth, but the solar radiation will be so intense that life on earth will become impossible.
This enormous radiation over a period of 2.5 billion years – after 10 billion years – will cause a mass loss of a very significant part of the outer layers. After 2.5 billion years, the core will shrink further – in this period the diameter of the sun will shrink from 200 times larger to 100 times smaller than the current diameter – and the temperature in the core will increases so far that the sun will shine very sharply : the sun has changed into a white dwarf  that will exist for 10 billion years. Hereafter the sun will probably cool and extinguish, and the sun turns into a black dwarf ”, says Peter.
“This predicts a violent and scorching end of our earthly life. First we have to see if our life on earth can last for more than 5 billion years before the sun will turn into a red giant. I expect that our earthy life will come across a number of other major threats within these 5 billion years, such as massive meteorites that had probably been the source of extinction of dinosaurs ; or humanity may well cause a world-wide nuclear war, that will destroy all life on earth”, says Ferdinand.
“It is also possible that in these 5 billion years the earth will be pulled from its orbit by the gravitational force of another large passing celestial body. If this happens, then the earth will probably cool to almost absolute zero in the empty space”, says Carla.
“Peter, your description of the end of our solar system reminds me of the end of in het Buddhist question “Aeonic Fire” of “Eternal/Endless Fire”:
When the fire at the end of time rages through and everything is destroyed, is this destroyed or not?”
One master answered: “Destroyed, because it goes along with this”.
Another master answered: “Not destroyed, because it is the same as this”.
“Why is this not destroyed?”
The other master answered: “Because this is the same as our universe”. 
Carla, yesterday you have explained that our universe has expanded completely uniform from one point with small quantum mechanical irregularities in the beginning, that later led to merging of matter into planets and stars. As a result, the centre of our universe is everywhere and nowhere; or in other words, every place is the centre of our universe.
When everything changes, does the centre of our universe also change? And changes – disappears – the centre of our universe at the end of time? What do you think?”, asks Man.
“A very good question with an important core. I think our supper is ready. Shall we first have supper before I will let my light shine on this question?”, says Carla.
“You are right: our supper is more important than questions about the origin and the decline of our universe . Let us enjoy the food prepared by our cook”, says Man.
Carla, Ferdinand, Peter and Man join the fellow travellers for their supper. After the meal they help with the dishes and the cleaning of the supper area; they prepare coffee for the whole group. Then they sit with fresh coffee at the still smouldering campfire, that is rekindled by Peter.
“What important core did you notice in my question about the changing centre?”, asks Man to Carla.
“Before I will go into this, I think it is good to explain the end of the different types of stars.
Basically, the way whereby a star will extinguish, is determined by the mass or the energy of the star. Stars with masses up to 1.4 times the mass of the sun , will swell into a the red giant in the same way as the sun, shrink into a white dwarf and at last extinguish into a black dwarf, because 1.4 times the mass of the sun is the maximum where white dwarf stars are stable.
Stars with a mass that is larger than this critical mass, can – depending on their mass and composition – take different paths on their way to their end as star. I will name only three of these different paths:
- Stars with mass around the critical mass of 1.4 times the mass of the sun, will rapidly implode at the end of their stable existence, whereby the nuclear fusion in the core wil causes so much pressure and energy that the contracting gravity of the mass is completely overcome: the beginning white dwarf will violently explode and be seen as a supernova to the starry sky ;
- Stars with a mass of more than 8 times the mass of the sun can – after a huge explosion during their short life as supernova whereby the largest part of the core mass will be blown into space – end as neutron stars with a mass of between 1.4 and 3 times the mass of the sun and a diameter of about 10 kilometres . The mass density of these neutron stars is very high and it consists entirely of neutrons, because the protons with the electrons fuse into the nucleus: the core of a neutron star resembles one giant atomic nucleus of neutrons, that is held together by gravity. There can still escape radiation in the form of neutrons and radio waves from gravity. Due to the radiation of high energy neutrons, a neutron star will cool from 10¹² K to 106 K within a few years. The electromagnetic radiation is usually observed as pulsating radio waves by the strong magnetic field while the neutron star rotates rapidly around her axis: this type of neutron star is being called a pulsar. A standard work on Cosmology says free rendered about these pulsating neutron stars: “The star is dead! Long live the star! From the ashes of the old star a pulsar neutron star is born, that emits its pulselike message of matter to the end of our universe; until after a million years its rotation energy runs out”. 
- Stars with a mass of about 15 to 20 times the mass of the sun, can end – after a huge explosion during their short period of time as supernova – as a so-called black hole when their residual mass after the explosion is more than 3 to 4 times the mass of the sun . The gravity of this residual mass is so large, that the core is further balled into a black hole from where nothing can escape: no radiation and no light. Around the black hole is an imaginary round surface called the observation horizon. Just outside this observation horizon; light can just escape the gravity of the black hole, within this horizon, everything – also light – is inescapably sucked into the black hole. Black holes are in different sizes and types, depending on the mass of the core of the black hole and the core diameter. The dimensions range from less than one millimetre to 1000 km in diameter and from 10 times to 10? times the mass of the sun . There are also fast rotating black holes with a flat gas/matter disc outside the observation horizon. This rotating disk can swing plasma perpendicular to the disk into space. The inside of the disk – of course outside of the observation horizon – can be so hot that the brightness is 100 to 1000 times larger than all nearby stars and moreover, the inside of the disc just outside the observation horizon of the black hole can also broadcast high energy x-rays .
This is a small virtual walk around the graveyard of the stars in our universe as a prelude to your question about changing – and the possible end – of the centre of our universe.
Shall we first have a beer before I will start herewith?”, says Carla.
“With your walk on the cemetery of stars, I begin to get a first impression of the meaning of a statement by a physician: “Empty space is the seat of the most violent physics””, says Ferdinand.
Peter gets four beer and hands the bottles to Carla, Ferdinand and Man. They drink a few sips.
“How can we detect black holes when these holes cannot broadcast information about their existence?”, asks Man to Carla.
“By the end of the eighteenth century, there was already speculation about the existence of a large number of black stars – or black holes – within our universe  and in 1915 the astrophysicist Karl Schwarzschild had described the preconditions for non-rotating black holes based upon Einstein's general relativity theory predicted: his calculations predicted the possibility of a gravitational field caused by a point mass with an observation horizon. But Albert Einstein and Arthur Eddington – the renowned experts on general relativity and gravity in the 20s and 30s – considered intuitively that black holes did not fit within their theoretical frames of reference .
The Indian astrophysicist Subrahmanyan Chandrasekhar  has calculated the maximum stable mass of white dwarfs as a 19-year-old young man on his boat trip to England in order to continue his studies and careers . In England, nobody was interested in his calculations, or his calculations were not accepted; and Arthur Eddington was an opponent of format, who in 1935 had presented his – afterwards inaccurate – view, that stars with a considerably larger mass than the sun could be saved from the fate of a ending as a black hole. Until 1960, Arthur Eddington's view was common in the astronomical world. Subrahmanyan Chandrasekhar was forced to focus his attention on other areas .
In 1939, Robert Oppenheimer  and others, using the so-called "Tolman-Oppenheimer Volkoff Limit", predicted that neutron stars – with more than 3 times the mass of the sun – could crush as ball into a black hole. The Second World War and the Nuclear Weapons Act led to an intermezzo in the theory of the life-end of stars. With the development of nuclear bombs, physicists were busy with threats of the nuclear life-end by enemies of the state.
In the 1950s the development of theory on the course of life of stars came back to life again; in 1967 the name Black Hole was introduced within the circle around the physicist John Archibald Wheeler , and this name became widely accepted. In 1964, Cygnus X-1  was observed for the first time and it is one of the most radiant sources of X-rays that can be seen from Earth. Around 1971, it was suspected that the core of Cygnus X-1 may contain a black hole and in 1990 this indirect evidence of the existence of a black hole was widely accepted. .
In 1975, English physicist Stephen Hawking  published calculations showing that black holes emit radiation at a temperature just above the absolute zero point. Because of this radiation, the black hole will lose energy and will become lighter when more matter evaporates than new matter from outside the observation horizon is attracted into the black hole. Theoretically, the black hole could completely evaporate through this radiation; but according to the calculations only a very small amount of energy will escape from the black hole throughout the entire age of our universe, . This so-called “Hawking radiation” is caused by the fact that at the absolute outer boundary of the observation horizon, the quantum mechanical uncertainty principle involves that matter/energy within the boundary can just escape to outside the boundary horizon. This matter/energy just outside the boundary radiates with a temperature just above the absolute zero.
In 1981, there was a debate between Stephen Hawking on one side and Gerard 't Hooft and Leonard Susskind on the other side about the question if information that will disappear into a black hole is lost forever . Gerard 't Hooft  and Leonard Susskind  had the opinion that this information is not lost forever in a black hole. One reason why both disagree with Stephen Hawking is that losing information in our universe – that must be seen as a closed system after the big bang and the uniform expansion – entropy  will decrease: this is a gross violation of the second law of thermodynamics that states that entropy  of a closed system can only increase .
I will explain this principle of increase of entropy by a simple metaphor. Fresh whipped cream is almost completely uniform, has a low entropy and contains little information, because the whipped cream is everywhere equal and can only be ordered in one way. Over time, the homogeneity of whipped cream will increasingly get lost, and at some point the whipped cream will separate in fluid and fat: the way wherein the separated cream can be ordered will increase and the entropy is also steadily increasing. Or freely rendered: order changes into chaos and a clean room changes over time in a dirty dusty room. And within our universe: just after the big ban the entropy was very low, because everything was almost homogeneous and everything could be ordered in a very limited manner. Over time, the universe became organised in particles, clusters of gas clouds, galaxy systems with stars and solar systems; and after some time graveyards of stars and solar systems arose: in short, the entropy is increasing ever more.
For these three physicists, this difference of view was of fundamental importance, comparable with the fundamental differences of view on the afterlife in the Christian faith before, during and after the .
According to Gerard 't Hooft and Leonard Susskind, the loss of all information after passing the observation horizon of a black hole implies that all the energy involved in this information might be lost forever. Or, to put it another way: all energy – read: E = mc² – connected to the mass of this information will be forever lost when passing the observation horizon. This is not permitted on the basis of the physical law of conservation of energy . In case all information might be lost, according to the law of conservation of energy, all energy involved with this information/mass should be completely annihilated at the moment of passing the observation horizon . Such enormous energy pulses/radiation – or residues thereof – caused by the complete annihilation of information/mass, have not been observed near black holes within our universe. According to Gerard 't Hooft and Leonard Susskind, this information is not lost in the observation horizon and/or within a black hole. I think this information can only be lost if our universe is not a closed system: if this is the case, this energy should leak into other dimensions, thus into a different universe . To date, no increase in energy from another universe has been observed within our universe.
Stephen Hawking believes that the gravity of a black hole is so huge that nothing – no light, no radiation, no mass – can escape from the observation horizon. The gravity within a black hole is so large that all matter is fully compressed into the smallest possible order and shape: a black hole that is not rotating will take the form of a fully compressed sphere or point. This results in a completely homogeneous core that has a low entropy wherein the original information will completely disappear. Thus, according to Stephen Hawking, the information of matter entering the black hole is lost forever.
In the course of the many discussions about the differences in view, Leonard Susskind (partly on the basis of Gerard van 't Hooft's work) developed the idea – and showed with the string theory  – that the information of the disappearing matter remains behind as a hologram  at the observation horizon of the black hole.
I will try to explain this idea of a hologram of information at the observation horizon of a black hole. According to the theory of general relativity, time near a very heavy mass – for example on the surface of an extremely heavy planet – passes slower than in the free space . Or, more accurately, an observer floating in a free space at a fixed distance from a planet will see the clock on a heavy planet, tapping slower than her/his own clock. Big black holes contain disturbingly more mass than a heavy planet. The full mass of a large black hole causes that an observer in free space will see, that changes and movements of a second observer who is approaching the observation horizon of a non-rotating black hole, will come to a halt. The observer floating in the free space will see the clock of the second observer almost come to a standstill. When the second observer goes through the observation horizon of the black hole, the observer floating in free space will notice that the second observer will not change anymore: this second observer will remain visible and standing still at the observational horizon forever . For the floating observer in the free space, the time at the observation horizon of the black hole has come to a standstill. Thus, according to Gerard 't Hooft and Leonard Susskind, the information of the mass that falls into a black hole, will remain always present on the observation horizon.
This difference of view has ended with the publication of Stephen Hawking in July 2004, wherein he has states, that the information – that has disappeared in a black hole – will reappear along with the vaporisation of mass/energy from the black hole.
After reading this outcome of the difference of view, I doubt whether both points of view have fundamentally come together. In addition, I have doubts about both ways of modelling. I will come back to it another time, Peter. Maybe when I give my view on your question about quantum mechanics”, says Carla.
“At the beginning of your introduction, I did not understand why you had first highlighted the end of the different types of stars, before addressing the issue conservation of “information/energy of matter/energy” when passing the observation horizon of black holes.
Also during your explanation of the search for answers to this question, I get again the impression that – for science and philosophy – humanity can only have access to limited numbers of myths for interpretation of our existence in a broad sense.
Now the end of my life is nearing, I prepare myself on passing the doors of perception between my life on earth and a life in the hereafter. Mankind has developed only a limited number of myths to give an interpretation – or explanation – to this irrevocable change. The separate world religions use these myths, and they have arranged these religious ideas in a different manner, but the original ideas show great resemblances .
Thereby I recognize two ideas very clearly. After the death of my aunt, I have taken care for the settlement of her inheritance or – in a metaphor – for a hologram of my aunt at the doors of perception between life and death. Within her legacy, I have recognised her fully as she was in my recent memory. Many years later I looked back at photos of her; my world had changed and she remained unchanged in the photos: she stood still in time.
Let us go on with our consideration of the universe. Carla, what will happen according to theoretical physics when an observer will pass the observation horizon of a black hole?”, says Man.
“That is an interesting question that we probably cannot answer with certainty, because an observer will cease to exist in the core of a black hole: the observer will fully merge with the core.
In my speculation, I will assume the simplest model :
- First of all, this model is based on a non-rotating black hole, because a rotating black hole rotates almost almost at the speed of light due to its small diameter; as a result, the layer just outside the observation horizon is very hot by friction .
- In addition, the observer enters perpendicularly to the observation horizon of the black hole, because otherwise the observer will probably faster and faster around the black hole .
- Let us assume a very large black hole with an observation horizon at a number of kilometres from the core, so this will maximize the survival time of the observer .
At the moment an observer enters the observation horizon of a black hole, there is a division between inside and outside the observation horizon. Like in our daily lives, different observers have a different and fragmented view of our universe .
I have just told you that an observer who is at a safe distance from the black hole will see the second observer who approaches the observation horizon come to a standstill in time and in place due to the massive gravity of the black hole. After passing this horizon, the image of the second observer remains visible on the observation horizon, because the time of the second observer has stopped. Space, time and space time cannot be observed beyond this observation horizon by observer at a safe distance . Mathematically, infinity and zero are approaching each other on the observation horizon in a singularity . Over time, the image of the observer who had passed this boundary, fades very slowly, amongst others under the influence of new matter approaching to and circling around the black hole.
The observer who goes through the observation horizon, will initially not notice that his time is slowing down, because all and everything in her/his vicinity slowing down in the same manner. Each second is experienced by her/him in the same way as before when she/he was at a safe distance. Also, she/he will experience nothing special at the passing the observation horizon, life continues as before. She/he is still too far away from the singularity of the black hole to notice its influence. In her/his experience of time, she/he will continue to live normally for about 20 hours, but faster and faster the core of the black hole will come near. The last second before her/his final death, the observer's body is stretched in the length by the huge – almost point mass out of the black hole – and compressed in the longitudinal direction; in the last hundredths of seconds, the observer dies and she/he will fully merge in the mass and singularity of the black hole.
Then time, space and timespace cease to exist for her/him – just like timespace doesn’t exist in the core of the black hole – : the four dimensions of timespace are again reduced – or wrapped to a point in the core of a black hole like in our universe before the big bang.
In my view, this is a very fast and peaceful death”, says Carla.
“Definitely a quick death, but the last 20 hours are lonely”, says Man.
“I think that at the same time more matter will disappear in the black hole. It will not be much matter, because from a distance it is difficult to travel straight to a black hole. Most matter in the direction of the black hole will have a minor deviation, whereby it will continue the journey in space after passing the black hole in another direction. At an extremely small deviation, the matter has a chance to continue of circling around a black hole. Only in exactly the right direction and without any deviations in between, matter can travel exactly to the observation horizon of a black hole”, says Carla.
“Can matter and radiation escape from a black hole?”, asks Ferdinand.
“I expect that there are black holes in sizes and kinds, just as there are stars in sizes and kinds. Let me assume a black hole, that is so compact that no movement, no nuclear fusion, and no heat development in the core is possible.
Still, I expect that this very compact black hole will shine like black body. The energy of radiation is proportional to the frequency of radiation . Because all mass – and as a consequence all energy via E = mc² – is sucked into the core of the black hole, the black hole will radiate with only an extremely low surface temperature. This radiation has a very low frequency; probably a tiny part of this radiation will reach the observation horizon. Via quantum mechanical mechanisms, a small part of this radiation/mass will escape from the the observation horizon; as a consequence this radiation will contain very little information”, says Carla.
“Is it possible that our universe will disappear into a black hole?”, asks Peter.
“I don’t know; I don’t think so. It is already late. Shall we continue another time?”, says Carla.
 See also: https://en.wikipedia.org/wiki/Red_giant
 Source image: https://en.wikipedia.org/wiki/Red_giant
 See also: https://en.wikipedia.org/wiki/White_dwarf
 Sources for the contribution by Peter:
- Harrison, Edward, Cosmology – The Science of the Universe (2nd Edition). Cambridge: Cambridge University Press: 2013, p. 100 – 104,
- Thorne, Kip S., Black Holes & Time Warps – Einstein’s outrageous legacy. New York: W.W. Norton & Company: 1994, p. 164 – 178,
 See also:
 Free rendering of the Zen koan Dasui’s “Aeonic Fire” in: Cleary, Thomas, Book of Serenity – One Hundred Zen Dialogues. Bosten: Shambhala, 1998 p. 131 – 136
 See also: Buddhist question “Yunmen’s Sesambread” in Yamada Kôun Roshi, Hekiganroku, Die Niederschrift vom blauen Fels. München: Kösel-Verlag, 2002, p. 236 - 243
 This is the so called “Chandrasekhar limit”, named after the Indian astrophysicist Subrahmanyan Chandrasekhar. His first name is via Sanskrit deductible to: “Birth/Origin from the good Brahman) and his second name to: “Summit/Crown or Best Part of the Moon”. In Buddhism the “moon” is sometimes used for “belief” or the “All-encompassing One”.
- See also: https://en.wikipedia.org/wiki/Chandrasekhar_limit
- Thorne, Kip S., Black Holes & Time Warps – Einstein’s outrageous legacy. New York: W.W. Norton & Company: 1994, p. 140 – 164,
 See also: https://en.wikipedia.org/wiki/Supernova
Remark: A supernova may also arise in another way, for example from a white dwarf near a red giant, where the white dwarf explodes and the red giant disappears from his orbit around the white dwarf, because the gravity of the white dwarf has spread out over a huge space with the explosion.
 See also: https://en.wikipedia.org/wiki/Neutron_star
 Source: Harrison, Edward, Cosmology – The Science of the Universe (2nd Edition). Cambridge: Cambridge University Press: 2013, p. 105
 This is the so-called “Tolman–Oppenheimer–Volkoff limit”. See also: https://en.wikipedia.org/wiki/Tolman%E2%80%93Oppenheimer%E2%80%93Volkoff_limit
- Harrison, Edward, Cosmology – The Science of the Universe (2nd Edition). Cambridge: Cambridge University Press: 2013, p. 246 – 269
- Thorne, Kip S., Black Holes & Time Warps – Einstein’s outrageous legacy. New York: W.W. Norton & Company: 1994, p. 209 – 258
 Source: Thorne, Kip S., Black Holes & Time Warps – Einstein’s outrageous legacy. New York: W.W. Norton & Company: 1994, p. 351
 Impression of a rotating black hole – the observation horizon is shown as a black ball – with a disc of gas/matter that is circling around the black hole and a vortex current perpendicular to the disk caused by, for example: a) hot gases caused by heat of due to friction in the inner ring of the rotating disc, or b) magnetic lines due to the rotating disk that swings plasma out of the disc outside the viewing horizon.
- Thorne, Kip S., Black Holes & Time Warps – Einstein’s outrageous legacy. New York: W.W. Norton & Company: 1994, p. 346 – 354 en
Source image: https://en.wikipedia.org/wiki/Black_hole
 Free rendering of a quote assigned to John Archibald Wheeler; See: John Harrison, M. Empty Space – A Haunting. London: Gollancz, 2012, p. 2
 Source: Thorne, Kip S., Black Holes & Time Warps – Einstein’s outrageous legacy. New York: W.W. Norton & Company: 1994, p. 123
 Source: Thorne, Kip S., Black Holes & Time Warps – Einstein’s outrageous legacy. New York: W.W. Norton & Company: 1994, p. 124 – 134
 See also: https://en.wikipedia.org/wiki/Subrahmanyan_Chandrasekhar
 Source: https://en.wikipedia.org/wiki/Chandrasekhar_limit
 Source: Thorne, Kip S., Black Holes & Time Warps – Einstein’s outrageous legacy. New York: W.W. Norton & Company: 1994, p. 140 – 163
 See also: https://en.wikipedia.org/wiki/J._Robert_Oppenheimer
 See also: https://en.wikipedia.org/wiki/John_Archibald_Wheeler
 See also: https://en.wikipedia.org/wiki/Cygnus_X-1
 Source: Thorne, Kip S., Black Holes & Time Warps – Einstein’s outrageous legacy. New York: W.W. Norton & Company: 1994, p. 314 – 321. Remark: In 1990 Stephen Hawking has accepted his loss in the bet with Kip Thorne.
 Photo of X-rays by Cygnus X-1. Source image: https://en.wikipedia.org/wiki/Cygnus_X-1
 See also: https://en.wikipedia.org/wiki/Stephen_Hawking
 Source: https://en.wikipedia.org/wiki/Hawking_radiation
 Simulation of a black wherein a galaxy disappears. Gravity forces has an effect of a lens that distorts considerable. Source image: https://en.wikipedia.org/wiki/Hawking_radiation
 See also: https://en.wikipedia.org/wiki/Black_hole_information_paradox
 See also: https://en.wikipedia.org/wiki/Gerard_%27t_Hooft
 See also: https://en.wikipedia.org/wiki/Leonard_Susskind
 See also:
- Susskind, Leonard, The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics. New York: Little, Brown and Company, 2008 p. 126 - 175
 Entropy is also the dimension for the number of possible ways of organizing information within a particular context. See also: Susskind, Leonard, The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics. New York: Little, Brown and Company, 2008 p. 131
 See also: https://en.wikipedia.org/wiki/Entropy
 See also: Origo, Jan van, Who are you – a survey of our existence – part 2.2 – Intensities and Associations. Amsterdam: Omnia – Amsterdam Publisher, 2014, p. 100
 See also: https://en.wikipedia.org/wiki/Conservation_of_energy
 See also: Susskind, Leonard, The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics. New York: Little, Brown and Company, 2008 p. 184
 See also: Susskind, Leonard, The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics. New York: Little, Brown and Company, 2008 p. 191
 See also: https://en.wikipedia.org/wiki/String_theory
 See also: Susskind, Leonard, The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics. New York: Little, Brown and Company, 2008 p. 290 – 308; en https://en.wikipedia.org/wiki/Holographic_principle
 See also:
 Of course, the image of the second observer will change at the observational horizon for the observer who is floating in the free space, but this change is extremely slow because the time is (almost) standing still due to huge gravity forces from the black hole.
 See e.g.: Eliade, Mircea, A History of Religious Ideas, Volume 1,2,3. Chicago: The University of Chicago Press, 1982
 This is the Oppenheimer – Snyder black hole model. See: Thorne, Kip S., Black Holes & Time Warps – Einstein’s outrageous legacy. New York: W.W. Norton & Company: 1994, p. 211 – 219 and 451
 See: Thorne, Kip S., Black Holes & Time Warps – Einstein’s outrageous legacy. New York: W.W. Norton & Company: 1994, p. 294 and 346 - 347
 See: Thorne, Kip S., Black Holes & Time Warps – Einstein’s outrageous legacy. New York: W.W. Norton & Company: 1994, p. 291 - 292
 See: Thorne, Kip S., Black Holes & Time Warps – Einstein’s outrageous legacy. New York: W.W. Norton & Company: 1994, p. 451
 See: Smolin, Lee, Three roads to Quantum Gravity. New York: Basic Books, 2001, p. 45
 See: Thorne, Kip S., Black Holes & Time Warps – Einstein’s outrageous legacy. New York: W.W. Norton & Company: 1994, p. 451
 See also: https://en.wikipedia.org/wiki/Gravitational_singularity
 Source image: https://universe-review.ca/I15-61-tidal.jpg
This image shows the elongated in a correct manner when approaching the core of the black hole, but in reality, the feet and legs will also be compressed in the direction of the core.
 See: Thorne, Kip S., Black Holes & Time Warps – Einstein’s outrageous legacy. New York: W.W. Norton & Company: 1994, p. 451
 See also: Susskind, Leonard, The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics. New York: Little, Brown and Company, 2008 p. 155 – 175