Big Questions in Science

Sebastian de Haro, fall 2012

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Robbert Dijkgraaf NRC 05-05-11: Total amount of Information on earth is 1 zettabyte

bytes

Big Questions in Science, fall 2012. SdH, AUC 7 Big Questions in Science, fall 2011. SdH, AUC 7

1 bit

Wave-like pattern encoded in wave function:

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Wave propagation

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“Traditionally these are questions for philosophy, but philosophy is dead. Philosophy has not kept up with modern developments in science, particularly physics. Scientists have become the bearers of the torch of discovery in our quest for knowledge. The purpose of this book is to give the answers that are suggested by recent discoveries and theoretical advances. They lead us to a new picture of the universe and our place in it that is very different from the traditional one, and different even from the picture we might have painted just a decade or two ago. Still, the first sketches of the new concept can be traced back almost a century.” (The Grand Design).

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?

Steven Weinberg:

Petty reductionism: whole to parts.

Grand reductionism: “To reduce the world of physical phenomena to a finite set of fundamental equations (or principles)” (Freeman Dyson). “Search for the common source of all explanations.”

Big Questions in Science, fall 2012. SdH, AUC 15

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Particle physics / gravity

String Theory, M-theory

Quantum mechanics/relativity/class.mech

Statistical physics/condensed matter

Biology

Chemistry

The rest

Weinberg: “One of the members of the [SSC] board argued that we should not give the impression that we think that elementary particle physics is more fundamental than other fields, because it just tended to enrage our friends in other areas of physics. The reason we give the impression that we think that elementary particle physics is more fundamental than other branches of physics is because it is. I do not know how to defend the amounts being spent on particle physics without being frank about this.”

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Philip Anderson: “They [the results of particle physics] are in no sense more fundamental than what Alan Turing did in founding the computer science, or what Francis Crick and James Watson did in discovering the secret of life.”

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“By far the most important [prediction] is super symmetry which is fundamental to most attempts to unify Einstein's General Relativity with Quantum Theory. This would be confirmed by the discovery of super partners to the particles that we already know. The Superconducting Super Collider (the SSC) was being built in Texas and would have reached the energies at which super partners were expected. However, the United States went through a fit of feeling poor and canceled the project half way. At the risk of causing embarrassment, I have to say I think this was a very short sighted decision. I hope that the US, and other governments will do better in the next millennium. (Stephen Hawking, Millennium lecture)”

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Snaartheorie, M-theorie

De rest

Intermediate areas:

Particle physics / gravity

String Theory, M-theory

Quantum mechanics/relativity/class.mech

Statistical physics/condensed matter

Biology

Chemistry

The rest

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Singularities

Big Bang

Black Holes

The problem of infinities Most serious: information loss

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Pierre-Simon Laplace (1749-1827).

Escape velocity.

Earth:

‘Black star’:

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Einstein 1915: mass implies curvature of space-time. Curvature is perceived as gravitational attraction.

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Black hole itself cannot be seen. Indirect evidence: matter swallowed up by supermassive black

object. Predictions: time delay, gravitational lensing.

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Black hole itself cannot be seen. Indirect evidence: matter swallowed up by supermassive black

object. Predictions: time delay, gravitational lensing.

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If as heavy as the sun: one meter. Supermassive (one million suns): size of the solar system. Milky Way: Sagittarius A*.

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Free fall.

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Heaviest objects, not even light can escape. Fish in the water analogy. Free fall.

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1973 Bekenstein develops black hole thermodynamics. 1974 Hawking: black holes emit radiation.

The key: quantum fluctuations of vacuum.

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Hawking Radiation

If we wait long enough, the black hole will evaporate.

Radiation contains no information about what went in.

Information disappears. Black holes violate quantum mechanics.

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Black holes emit radiation. The radiation is thermal, contains no information. Information is lost. New level of unpredictability in physics.

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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.

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1993 Gerard ’t Hooft Thought experiment: box volume

Entropy: measure # states

RE

#~ ES

Gravity in the Bulk

Theory on Boundary Big Questions in Science, fall 2012. SdH, AUC 52

’t Hooft 1993 “dimensional reduction”

Susskind 1994 “holography” Maldacena 1997 holography in string theory 2004 Hawking admits he lost his bet

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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.

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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?

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Gravity 5d

4d particle physics (QCD) Gravity 4d

3d particle physics

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Temperature Hawking radiation

Temperature material

Electrical and thermal transport properties

(conductivity)

Small perturbations of black hole

Common element in all holographic dualities: “long” distances in one theory correspond to “short” distances in the other.

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Big Questions in Science, fall 2012. SdH, AUC 59

Long-distance cutoff

UV cutoff

Gravity seems equivalent with physics of conducting materials

Also connections with hydrodynamics

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Sheldon Glashow (1975)

Cosmology

Quantum Mechanics

Particle Physics

String Theory

Geology Medicine

Astronomy

Biology Chemistry

Big Bang

Oceanography

Contextual models with local overlaps and interaction within general framework.

Unity: connection of distant areas (IR/UV). Important question: Fundamental variables?

Answer may depend on physical context. Roger Penrose : Grand reductionism does not

exclude (rather, necessitates) philosophy. Connection math, arts, ethics.

Big Questions in Science, fall 2012. SdH, AUC 64