Notes on Nobel Conference - Part 2
Day One late afternoon:
Speaker Three: Kip Thorne - Feynman Professor of Theoretical Physics, California Institute of Technology, Pasadena, California
Caltech’s Kip Thorne is one of the world’s foremost experts on the consequences of Einstein’s theory of general relativity. Thorne has done pioneering research on black holes and gravitational physics and laid the foundations for the theory of pulsations of relativistic stars and the gravitational waves they emit. He is a co-founder of the Laser Interferometer Gravitational Wave Observatory (LIGO) Project, whose goal is to detect gravitational waves emitting from black holes, a search that could ultimately provide a view of one of the universe’s most mysterious objects.
Studies black holes. Cofounded the laser interferometer lab for detecting the gravity waves produced by black holes. CalTech faculty. National Academy of Sciences, many honorary degrees. co-authored "Gravitation". Recognized for research, general writings, teacher.
Newton and Einstein. Newton 1643-1727: a framework for the laws of nature that last 200 years. Space, time, forces, accelerations ... everyday experience. Einstein 1876 - 1955: A new framework, now in place for 100 years. Laws the same in all reference frames. Time is "relative" (personal); space is "relative" (personal). Minkowski: Space-time unified; absolute (4 dimensions). Teacher of Einstein's Discovered in Einstein's laws a way to unify space and time. This is an absolute reference frame. Laws as 4 dimensional geometry. Space-time (and space & time) warped by mass & energy they contain.
The warping of space he means: space is warped inside and around the sun and any other massive body. So a flat sheet bisecting the sun won't be euclidian. The parallel lines will cross. Warping of space and time like a rubber sheet. Deflection of starlight [Einstein 1915]. There is a shift (gravity lensing). Verified by Eclipse Expedition of 1919. By 1955 the test data was found to be not very accurate. Appeared to be too big by about 20%. In 1970 they used radio interferometry. By 2005 accuracy was found to be to 1 part in 10,000 (.01%). Using SIM (Space Interferometry Mission), to be launched in 2011, researchers will map stars in sky to 4 microarcsecond accuracy, 1,000 times more accurate that solar light deflection for measurements far from the sun. But this may be bumped by Bush's Moon/Mars mission.
Warping of Space: gravitational Lensing [Einstein 1912, 1936]. SIM will search for exotic objects, map dark matter in galaxies and clusters of galaxies, and measure the cosmological properties of the Universe.
Warping of Time [Einstein 1915] TIme slows near any massive body. 1955 it's still controversial! Sun is messy! 1976 Gravity Probe A, Robert Vessot predicted time slows near Earth by 4 parts in 10 billion. Confirmed to accuracy of 0.01 per cent.
Warping of Time today: global positioning System (GPS) works on basis of accurate clocks in satellites. GPS would not work if correction for rate of time not built into it.
The Whirl of space: The angular momentum of a rotating body drags space into tornado like whirl around it [ Lens & Thiring 1919]. Accounts for one revolution every six million years. Gravity Probe B's goal is to measure space whirl to one per cent accuracy. Some data in. Results due in one year.
Black Hole (BH) made from warped space-time. Predicted by Karl Schwarzschild in 1916. Oppenheimer & Synder gave specific predictions in 1939. Diameter is very large compared to pi because of the warping of space (dimple). Below the event horizon no signal or light can escape because time slows, and below the horizon time flows backward [?]. As black hole spins it creates a whirl of space. The challenge for coming decade: probe black holes in exquisite detail.
Map for non-spinning hole. At event horizon the rate of time is zero. A fast spinning hole has a long narrow throat. How can we see a black hole and map its space-time warpage? Use radiation made from the same stuff as the hole: a second smaller black hole in orbit will produce gravitational waves. Full map of big hole's warpage is encoded in the waves. This includes all aspects of small black hole as it orbits a big black hole. For a pair, the small BH creates frequency, large BH creates precession of small BH, given as a modulation in the signal. How to monitor gravitational waves? Consider it being like two corks on the waves of the ocean. Monitor that motion with corks. Earth-based detectors. Small holes in distant galaxies: about 10-100 suns, about 100 km in size. Using a network LIGO detectors. Network is required for detection confidence, waveform extraction and direction by triangulation. LIGO has built two detectors in the US (one in Hanford WA, one in Livingston LA). Full network requires collaboration of about 500 scientists at about 50 institutions in 8 countries.
LIGO (laser interferometer gravitational-wave detector) works by the motion of mirrors. It will detect one part in 10 to the -21st power in the GW field. Motion is 4 times 10 to the -16th power cm of movement. How small is ten to the -16th"? Well, 1-cm is 10 to the -2 m, human hair is 10 to the -4 m, wavelength of light is 10 to the -6 m, atomic diameter is 10 -8 m, nuclear diameter is 10 to -13 m, LIGO sensitivity is 10 -16th m. A year-long search begins next month.
LISA is a planned 3 satellite laser interferometer space antenna to be launched in 2014 (again, probably Moon/Mars funding will ground LISA). Looks at giant holes in distant galaxies where there may be 1 million suns the same diameter as LISA when deployed. In orbit around the sun like the Earth. What if map is not that of a BH? May have discovered a new type of inhabitant of the dark side of the universe. Two long-shot possibilities are:
- Boson stars - objects made from cold, dark matter (dark "stars")
- Naked Singularities - where gravity becomes infinitely strong with strange warping of gravity.
Probing the big BH's event horizon and subsequent tides by small BH, will be the job of LISA. Most interesting source of waves will be collisions of BHs. The most violent events in the universe. In such a case 10% of a hole's mass is converted to radiation. Fusion has efficiency of .5 of 1%. With a colliding BH there are no electromagnetic waves emitted whatsoever, just gravity waves. When they collide you get tornados, wild vibrations of warped space-time. How far can we see these collisions? 250M light years (includes about 50,000 galaxies) estimates predict one collision every 10 years (so we have to be lucky to see one). Upgrade in 2010 to advanced detectors with greater capability.
Want to interpret observed waves and compare with computer simulations. Simulations are very difficult. Movie made by numerical relativity group in Golem Germany depicts the waves.
Singularity in BH's core. Domain of quantum gravity: string/M theory (Gates' lecture). Is there any hope to ever do experimental studies of singularities in the present day universe? Probably not. Roger Penrose' Cosmic Censorship Conjecture: all singularies are hidden. Thorne bet Hawking about naked singularies along with Prescal. Hawking has conceded the bet, but not graciously. Conceded because of the result of imploding gravitational waves. They had enough energy to nearly form a BH, but waves went in , interacted nonlinearly, and created a naked singularity. At the center both time and space began to boil. Right at the center was a naked singularity. Lasts for infinitesimal time.
Wormholes and Time travel:
Wormholes span the universe through a hole in hyper-space. GR says they could exist if you could keep throat open. But to do that you have to thread through it a string of matter with a negative energy.
Backward Time Travel: Kip said in 1988-90 that if you have a wormhole, it's easy to make a time machine. Time dilation ahead or behind if you go through the wormhole. Kip and Kim 1990 say you get an explosion when you try to activate it due to quantum fluctuations in the same space and time. You get a quantum feedback loop. Kip later said that the explosion is weak, resulting in no destruction. Hawking said you're wrong and that the time machine self destructs.: chronology protection conjecture.
Growing consensus is that only the laws of quantum gravity know for sure. Stephen Hawking's 60th birthday gift to Kip: a first attempt to estimate via quantum gravity that there is zero probability that time machines can be created (to the level of 1 in 10 to the 60th). His 60th birthday gift to Stephen was LIGO and LISA will test his BH predictions.
Our extreme ignorance of warped space-time:
Does a BH have the precise shapes of warping that GR predicts?
What happens when BHs collide?
What other objects made from warped space-time ... exist?
Singularies: what are their structures?
Q&A
Q - ?
A - If the laws of physics permit time travel they should keep the world safe for not only historians but also physicists. Self consistency proposed by Novakoff. Says you can't go backward in history. Full story not known. Might collide with yourself coming back so balance might be preserved.
Q - Ellis - expert on GR. No fixed space-time to grab onto. It's all moving around. Also, time machines discussion between Einstein and Gerbel. It upset Einstein.
A - Went to see Gerbel, wanted to know about galaxy spins lining up. Time travel perhaps affected by net spin of universe. Duhler [?] example of naked singularities. Hawking says nature abhors naked singularity. Challenge is whether or not singularity is generic or a special case. If you disturb it slightly do you still get a naked singularity?
Q - Freedman - do you have concern about the background noise to be detected by LIGO ?
A - Lasts for seconds to tens of minutes. If only a few times a day it should be okay. For LISA it is a major issue. Small objects falling into BH all the time. Have to sort them out. Have to develop ways to separate out sources. Thousands or millions of sources for LISA.
Q - Levenson - how well was precession of Mercury known at that time of Einstein?
A - Maybe 10%, not real good, but enough to be a question for decades until Einstein's predictions.
Q - Gates - Ray Wise some months ago, LIGO science has started already. What are possibilities that might lie around corner if they are lucky?
A - Depends on how kind nature is to us. There are uncertainties. Here, as with x-ray astronomy, theorists can predict but the astronomy capability lags behind theory. Do have a shot at seeing real waves. LIGO is funded by NSF, not NASA. However LISA depends upon NASA.
Q - How fast do gravity waves travel?
A - GR says at speed of light. Nature of physics says energy travels via quanta called gravitons. Like photons they lack zero rest mass. Can test. Gamma ray bursts would exhibit gravity waves and light waves arriving at same time.
Q - Quantization of time?
A - Gates: quantization of space-time, no fundamental quantization of time, but some measure of effect on scale of space-time that can be measured.
Q - Mathematical predication of where BHs are found?
A - Look in region of space with clusters of stars or massive stars. Better odds there.
Day Two
Day Two morning:
Speaker Four: Sylvester James Gates, Jr.
John S. Toll Professor of Physics, Department of Physics, University of Maryland, College Park
S. James Gates Jr. has focused his research on the mathematical and theoretical physics of “super-symmetric” particles, fields, and “strings,” including topics such as the physics of quarks, leptons, gravity, super and heterotic strings, and unified field theories of the type first envisioned by Albert Einstein. Gates’s work has been featured, along with that of several fellow physicists working in superstring theory, in a 1996 television program titled “The Path of Most Resistance,” part of the PBS television series Breakthrough: The Changing Face of Science in America.
"Is Cosmic Concordance in Concomitance with Superstring/M-Theory". What is important is to find you passion and then live it every day. Gravity, QM and GR need to be combined somehow. Super-symmetry and string theory may be the path. Accessible only to a small number of physicists who can do the math.
Teaches undergrads every year. Kenneth Griggs did the animation. Images are his creations. Necessary because no part of string theory has every been observed in the laboratory.
Einstein's biggest blunder: the Cosmological Constant. Introduced in his Field Equation. It was for the "quasi-static distribution of matter as required by the fact of the small velocities of the stars". Later thought it was the "biggest blunder he ever made in his life". Lambda is the cosmological constant. At the time all thought the universe had been here forever. It was a fudge factor inserted in the field equation. Big bang and big crunch is possible if Lambda = 0 (no constant). If Lambda is less than 0 you get expanding universe that speeds up (concordance model). If Lambda is greater than 0 you get a fixed universe bubble or fast expanding universe.
Dark energy: 65% of energy in universe, dark matter is 30% regular matter (baryons) is 5%. Dark matter keeps galaxies together. Computer simulations show that without it a pinwheel galaxy would spin apart. So it plays some role sustaining galaxies over billions of years. Galaxy at instant of big bang has equal distribution of energy, (concordance model).
One early clue was that satellites launched into orbit to detect nuclear explosions occasionally got out of alignment and turned their sensors outward. They detected explosions from outside the solar system. Natural phenomena. This creates violent ripples in space-time. LIGO is set to detect these. LIGO measures changes in distance caused by ripples in space that are perhaps 1/100th of the diameter of a proton. It's like a sonogram. Analogy is that we're in the womb making sonograms of our mother (the universe).
Science fiction is motivated by science. Strings are on the order of 10 to the -35 meters in scale. Compare to protons on the scale of 10 to the -15, atoms on the scale of 10 to the -10, DNA on the scale of 10 to the -9, cells on the scale of 10 to the -5. The Bosonic String uses non-covariant and covariant equations. Employs number theory, topology, etc. Leptons (electrons & friends) include all those that spin at a half H-bar. Quarks are in protons, neutrons, etc. and they spin at a whole H-bar. Action at a distance is not consistent with Einstein's SR. Time and space are not independent. According to the math, action is instantaneous, but that's not the case if all travels at the speed of light. How to resolve?
The interaction paradigm is one photon sending a message carrier. That message carrier conveying forces has a time delay that accounts for forces not being instantaneous. Photoelectric effect showed that there was a classical path and a quantum path. Analogy: Kids don't understand at first how objects fly through air, but they learn. Dogs catching frisbees can learn it too. Einstein didn't trust QM, but cell phones are a good test that it does work. Interaction paradigm could also be an electron giving off a photon and it splits into an electron and a positron, they recombine, and it is transferred to another photon. Quantum weirdness. Feynman Rules. Ultra-violet infrared catastrophe of GR.
In 1960 Hawking and Beckinstein said you can escape from a BH but requires quantum weirdness. So you have quantum rules happening on a gravitational scale. Hawking's BH radiation paper used gray-body factors and suggested that there is a gap that contains this "guess" that combines them.
Where does string theory fit in physics? Waves and particles replaced by filaments. It has normal modes (like notes from a string). Strings can be open or closed (ends tied together). Like spaghetti and spaghetti-Os. These are not fairytales, they represent the mathematics. Complex, but not more than an orchestral performance represented by musical scores. In how many different perspectives can you see an object? In 3D there are three: top-bottom, back-front, left-right. But strings require 25 ways. In the first generation of string theory no one incorporated spin. So they took the math of spinning electrons and applied it to strings. Created "spinning string". This approach required only 10 dimensions.
In 1984 four physicists wrote equations for the 10D heterotic superstring. Nodes of vibration are points that don't move in a vibrating string. They rotated the nodes. Propagation of left-moving modes. In a single package this describes gravity and quantum theory. This filled in the "guess" that Hawking made. Exactly in agreement.
In late 90s 4D heterotic superstrings. Electrical charge, weak charge & families save the day. More complicated than their 10D cousins. Right movers and left movers (propagation of left-moving modes). So this shows that extra dimensions aren't required (but still may happen). Formulation C: three formulations of heterotic strings.
How forces arise in string theory: two free closed strings join to form a single closed string: C3. In reverse, they can split apart (C3 : C1 and C2). Since strings represent notes and notes are particles, following the notes shows that there is a well established mathematical basis for quantum gravity.
SLeptons and Leptons means that symmetry mandates string versions of leptons. This yields photinos, selectrons, smuons, staons. He says it would have been proved by the super conducting supercollider, but wasn't built. So they saved the cost of 4-5 B2 bombers by not building it.
Q&A
Freedman - Is String Theory Concomitant?
A - Many parts are, especially concordance of dark matter. String theory looks very good here. Quintessence (cosmological constant) is greatest challenge to string theory. Fudge factor is highly nontrivial. In special limit of string theory you can put fudge factor in if superstring theory employed.
Levenson - in legacy of Einstein, how does string theory fit? Geometry is a way of thinking. Geometrical thinking
A - Geometry is the key to string theory. Incomplete. We don't understand what geometry means in totality of string theory. Still looking for that iconic image of a man in the elevator. No such deep dramatic statements in string theory. Few think Einstein will be correct in this regards.
Ellis - you are cautious and many colleagues in string are not. Penrose's Road to Reality discusses geometric side. 4D very exciting but not linked to cosmology yet. Loop quantum gravity is a new theory and this could link to string.
A - Loop Quantum Gravity he opposes. Problem is that Energy Momentum Tensor (us) can be set to zero. But in string theory you can not set EMT to zero, you must have it for 4D theory. Says space, matter, energy equally important. Thinks the two theories will coalesce through use of spin networks. GR has no fixed reference frame, and string theory does. String loops (spaghetti-Os) are the forces of gravity. Covariant string field theory. That's the geometric route for spaghetti-Os to combine with Einstein's theories.
Q - Place of uncertainty in string theory?
A - Assume that we have properly understood quantum theory, so uncertainty is a basis.
Q - Is there a medium in which strings vibrate?
A - It doesn't vibrate in a medium despite the animations (not the truth). Don't require an extra dimension in which to perform the vibrations.
Q - Is 10 to the -35 scale is coincident with Planck's constant?
A - Not a coincidence. Math of string theory has behavior of Einstein's graviton. Had to insert Planck length to make it work.
Q - Multiple spatial dimensions but only 1 temporal dimension. Could there be more than one temporal?