4. PHYSICS’ HOLY GRAIL: UNIFICATION
• Relativity and quantum theory
• Look for clues: black holes.
• Both relativity and quantum mechanics play a role.
5. PLAN
• Classical properties of black holes.
• Quantum black holes: they are not black.
• Information paradox.
• Complementarity of observers.
• Holographic principle.
6. WHAT ARE BLACK HOLES?
• Pierre-Simon Laplace (1749-1827).
• Escape velocity.
• Earth: 𝑣 = 11,2 km/s
• ‘Black star’: 𝑣 = 299 972 km/s
7. WHAT ARE BLACK HOLES?
• Einstein 1915: mass implies curvature of space-time.
• Curvature is perceived as gravitational attraction.
9. OBSERVATIONAL EVIDENCE
• Black hole itself cannot be seen.
• Indirect evidence: matter swallowed up by supermassive black object.
• Predictions: time delay, gravitational lensing.
10. OBSERVATIONAL EVIDENCE
• Black hole itself cannot be seen.
• Indirect evidence: matter swallowed up by supermassive black object.
• Predictions: time delay, gravitational lensing.
11. HOW LARGE IS A BLACK HOLE? 2𝐺𝑀
𝑅= 2
𝑐
• If as heavy as the sun: one meter.
• Supermassive (one million suns): size of the solar system.
• Milky Way: Sagittarius A*.
18. • 1973 Bekenstein develops the thermodynamics of black holes
𝑘𝑐 3 𝐴
𝑆=
• 1974 Hawking: black holes can emit radiation! 4𝐺ℏ
ℏ𝑐 3 𝑀
−8 ʘ K
𝑇= = 6,2 × 10
8𝜋𝐺N 𝑀𝑘 𝑀
19. HAWKING’S PROVOCATIVE CONCLUSION
• If we wait long enough, black hole evaporates.
• The radiation does not contain information about what went in.
• Information forever lost.
• Black holes violate the laws of physics.
22. SUMMARY – HAWKING’S ARGUMENT
• Black holes emit radiation.
• The radiation is thermal, contains no information.
• Information is lost.
• New level of unpredictability in physics.
38. SUMMARY – BLACK HOLE COMPLEMENTARITY
• Alice and the cat have different descriptions of reality.
• Their points of view are mutually exclusive.
• Describe black hole from point of view of an observer.
• Led to holographic principle.
40. 𝑘𝑐 3 𝐴
𝑆=
4𝐺ℏ
Gravity in bulk
⇔
boundary theory
41. 2𝐺N 𝑀
𝑅s = 2
~𝐸
𝑐
THE DISCOVERY OF HOLOGRAPHY 𝑘𝑐 3 𝐴
𝑆BH =
4𝐺ℏ
• 1993 ’t Hooft
• Gedanken experiment: box volume 𝑅 3
ER
• Entropy: measure of # of physical states
𝑘𝑐 3 𝐴
S~E # 𝑆<
4𝐺ℏ
Gravity in bulk
⇔
boundary theory
42. HOLOGRAPHY
• ’t Hooft 1993 “dimensional reduction”
𝑘𝑐 3 𝐴
𝑆=
4𝐺ℏ
• Susskind 1994 “holography”
• Maldacena 1997 holography in string theory
• 2004 Hawking admits he lost his bet
43. HAWKING’S 2005 PAPER
There is no baby universe branching off, as I once thought. The
information remains firmly in our universe. I’m sorry to disappoint science
fiction fans, but if information is preserved, there is no possibility of using
black holes to travel to other universes. If you jump into a black hole, your
energy will be returned to our universe but in a mangled form which
contains the information about what you were like but in a state where it
can not be easily recognized. It is like burning an encyclopedia.
Information is not lost, if one keeps the smoke and the ashes. But it is
difficult to read. In 1997, Kip Thorne and I, bet John Preskill that
information was lost in black holes. The loser(s) of the bet were to provide
the winner(s) with an encyclopedia of their own choice, from which
information can be recovered with ease. I gave John an encyclopedia of
baseball, but maybe I should just have given him the ashes.
44. SUMMARY
• Black holes can radiate, which gives rise to information paradox
• Paradigm to solve this problem: holography – confirmed by string
theory: the world is 3- not 4-dimensional
• Gravity is a “fake” force
• Implications for reductionism?
45. SCIENCE & CULTURE BLACK HOLES IN De Gids
• Prof. dr. F.H. van Lunteren: • Essays: Gerard ‘t Hooft, Vincent
Influence of cultural and Icke, Ed van den Heuvel, Michiel
philosophical climate of van der Klis, John Wheeler,
quantum mechanics during Jeroen van Dongen, Sebastian
de Haro
Weimar Republic, March 29.
• WWW.HETWERELDBEELD.NL
• Poems: Leo Vrooman, Maria
Barnas, Rogi Wieg, Mustafa
Stitou, Jan Baeke
