Recreating the Big Bang?

With the start of the Large Hadron Collider coming closer, the topic is present in the media more than ever. A commonly used motivation is the alleged recreation of the Big Bang (see illustration to the right).
Peter Woit recently mentioned that Martinus Veltman, winner of the '99 Nobelprize in physics, “described claims that the LHC will 'recreate the Big Bang' as 'idiotic', and as 'crap'. He said that this is 'not science', but 'blather', and that the field would come to regret this, arguing that if you start selling the LHC with pseudo-science, you will end up paying for it.”

I am totally with Veltman. But what is behind the story? What does the LHC have to do with the Big Bang?

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The Making Of
It is interesting to trace back how this inaccurate description developed. In February 2000, BBC News wrote on CERN's SPS:

'Little Bang' creates cosmic soup
10 February, 2000

Scientists have created what they describe as a "Little Bang" inside which are the conditions that existed a thousandth of a second after the birth of the Universe in the so-called Big Bang.

Two years later, CNN.com writes about RHIC:

'Little' Big Bang stumps scientists
November 20, 2002

Smashing together atoms to produce conditions similar to those in the first cosmic moments, scientists came up with some startling results that could force them to reexamine their understanding of the universe.

Five more years later we can read on MSNBC about the LHC:

Teams toil underground to re-create big bang
March 2, 2007

It is a $4 billion instrument that scientists at the European Center of Nuclear Research, or CERN, hope to use to re-create the big bang — believed to be the event that caused the beginning of the universe — by crashing protons together at high speed.

Within 7 years we have thus moved from a 'little bang' via a 'little Big Bang' to a complete recreation of the Big Bang, a story which catches on. The TimesOnline writes “The machine, the Large Hadron Collider (LHC), aims to recreate the conditions of the Big Bang, when the universe is thought to have exploded into existence about 14 billion years ago.”, the German magazine Stern titles "Large Hadron Collider" - Urknall im Labor (Big Bang in the Lab), and for the Telegraph the LHC turned into a “Big Bang Machine” that “could destroy the planet” [1].

True, the LHC speeds up particles to higher energies than SPS, but still this is far off from anything similar to the Big Bang.

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The Big Bang

The Big Bang is believed to be the first moment of the universe. Technically seen, it takes place at arbitrarily high energy density. It is commonly expected however that in this regime quantum gravity becomes important, and the density is neither infinitely high nor is the volume arbitrarily small. But still the temperatures for this to happen would be somewhere in the Planckian regime, that is at average energies of about 10¹⁶ TeV.

To our best current understanding, the universe then undergoes a rapid phase of expansion during which all energy densities drop and all matter cools. With dropping temperature, we pass the scale above which we expect Grand Unification and the three forces of the standard model separate. This is believed to be somewhere at 10¹³ TeV. Then around a TeV there is the electroweak phase transition. At some hundred MeV, that is about 10^-4TeV, quarks start to form bound states like protons and neutrons. This is commonly called hadronization. It is this transition that we can now hope to study in appropriately designed collider experiments [2].

After hadronization, at temperatures around one MeV (10^-6TeV), atomic nuclei can form - a process that is called 'nucleosynthesis'. Around this temperature also the only weakly interacting neutrinos decouple [3]. At temperatures of the oder eV (10^-12TeV) atoms form and photons decouple. These photons have been traveling freely since this so called `freeze-out'. We can observe them today in the cosmic microwave background with an average temperature of around 3K (10^-3eV) because they have been further redshifted by a factor 1000 since the freeze-out. After freeze-out, structure formation sets in, first stars, galaxies, solar systems and planets form. Some of these planets might carry intelligent life, some might even have a blogosphere.

For a useful illustration of the universe's timeline, see here.

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The Little Bang

There are several important differences between the conditions created at the LHC and the Big Bang.

1. The LHC main program is proton-proton collisions. There is no sensible way in which one could understand the conditions created in these particle collisions as a thermal density distribution. These are scattering experiments. (Though some of the data obtained in these experiments can have thermal characteristics, this does not mean it was indeed similar to the early universe.) The LHC will also have a heavy ion program in which lead nuclei are collided which each other. In these circumstances it is more appropriate to speak of actually creating an intermediate state with a high density and energy density.



2. However, in such heavy ion collisions, the produced state of high density from the two nuclei expands much more rapidly than would be the case in the early universe. Everything is over within the time span needed for light to cross a few diameters of the colliding lead nuclei, or a few 10^-22 seconds. In fact, the expansion is so rapid that it is not even clear from the outset if one can expect any thermalization. In contrast to this, in the early universe the hadronization transition happens after about the first microsecond, and the Hubble expansion is so slow compared to the back and forth of the quarks and gluons that it's granted the early universe is thermal. (Again, though some of the data obtained in heavy ion experiments has thermal characteristics, this does not mean it was indeed similar to the early universe.)



3. Also, in the early universe the expansion of the matter is due to the expansion of space itself. In the laboratory, it is the matter that expands in an to very good approximation flat and static background. Though this might not make a difference for the cooling of the matter, it is conceptually very different.



4. The typical temperature that is created in heavy ion collisions is some hundred MeV. That is about 19 orders of magnitude below the temperature we expect at the Big Bang.

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Bottomline

The LHC is not a Big Bang machine. It is more accurate to say that with the heavy ion program at the LHC we will be able to create conditions closer to that in the early universe than ever before. This sounds more boring, but at least it isn't blatantly wrong. Aside from this, it is more useful to think of the LHC it as the world's largest microscope, that will help us to peer into the structure of elementary matter to a resolution better than ever before.

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[1] For extensive explanation why it is implausible the LHC will cause the end of the world, see: Black Holes at the LHC - The CERN Safety report, Black Holes at the LHC - again, and Black Holes at the LHC - What can happen?[2] Please note that we are here talking about temperatures. The energy scales usually quoted for the LHC (14 TeV for pp and about 1150 TeV for Pb-Pb) are total center-of-mass energies, not temperatures.
[3] Since neutrinos decouple considerably earlier than photons, measurement of the cosmic neutrino background could allow us to lock back further than the cosmic microwave background.

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TAGS: LARGE HADRON COLLIDER, BIG BANG, SCIENCE AND SOCIETY, PARTICLE PHYSICS

This and That

• It's summer in the city again - last week saw the first really hot days in Frankfurt. One of the many nice things about Frankfurt is that it's easy to escape to the countryside - the meadows and fields at the foot of the Taunus hills for example are a great place for a after-work walk,
  
  
  
  with the city skyline in the background...
  
  
  
  Both photos have actually been taken from the same place, at around the same time. If you look closely, you can see the shadow of one of the towers projected onto another building, a phenomenon one can witness in Frankfurt at sunset around the summer solstice.
  
  My time in Frankfurt is coming to an end soon, and preparations for the move and all the things involved are one of the main reasons for my sparse blogging activity lately.



• The week also saw the record average price for gasoline so far, with €1.60 per litre, or $9.40 per gallon, which makes commuting to Heidelberg quite expensive. I'm quite happy that my old Twingo is content with a bit more than 5 litres per 100 km, or, eh, has a mileage of about 45 miles per gallon.
  
  I've always found the concept of mileage a bit confusing, not just because of the conversion to strange units such as miles and gallons, but also because of the reciprocal involved. Fortunately, there are now online tools to ease the conversion, and even Google does the job.
  
  It seems that the use of "miles per gallon" can mislead when searching for fuel efficiency - that's because the differences of inverse quantities are not very intuitive. You can check this out for yourself with an (a bit silly...) interactive quiz. But I'm still surprised that this deep insight has made it onto the pages of Science.



• Speaking of Science, this week's edition of the magazine is a Special Issue with reports on results from the first MESSENGER flyby at Mercury last January (subscription required, unfortunately). Which reminds me that I owe someone a longer post about the flyby I should publish soon.

Have a nice weekend!

PS to The End of Theory?

" 'If Darwin had had a computer on his desk,' [the ruddy-faced nonlinear economist W. Brian Arthur] exclaims, 'who knows what he could have discovered!' What indeed: Charles Darwin might have discovered a great deal about computers and very little about nature.

~ John Horgan, From Complexity to Perplexity, SciAm June '95

The End Of Theory?

Chris Anderson, the editor in chief of Wired Magazine, wrote last week an article that you find at the Edge proclaiming

The End of Theory:
The Data Deluge Makes the Scientific Method Obsolete

Anderson claims that our progress in storing and analyzing large amounts of data makes the old-fashioned approach to science – hypothesize, model, test – obsolete. His argument is based on the possibility to analyze data statistically with increasing efficiency, for example online behavior: “Who knows why people do what they do? The point is they do it, and we can track and measure it with unprecedented fidelity. With enough data, the numbers speak for themselves.”

This, he seems to believe, makes models entirely unnecessary. He boldly extends his technologically enthusiastic future vision to encompass all of science:

“Consider physics: Newtonian models were crude approximations of the truth (wrong at the atomic level, but still useful). A hundred years ago, statistically based quantum mechanics offered a better picture — but quantum mechanics is yet another model, and as such it, too, is flawed, no doubt a caricature of a more complex underlying reality. The reason physics has drifted into theoretical
speculation about n-dimensional grand unified models over the past few decades (the "beautiful story" phase of a discipline starved of data) is that we don't know how to run the experiments that would falsify the hypotheses — the energies are too high, the accelerators too expensive, and so on.

Now biology is heading in the same direction... ”

Examples he provides rely on statistical analysis of data. It doesn’t seem to occur to him that this isn’t all of science. It strikes me as necessary to actually point out the reason why we develop models is to understand. Fitting a collection of data is part of it, but we construct a model to gain insight and make progress based on what we have learned. The point is to go beyond the range in which we have data.

If you collect petabytes over petabytes about human behavior or genomes and analyze them running ever more sophisticated codes, this is certainly useful. Increasingly better tools can indeed lead to progress in varios areas of science, dominantly in those areas that are struggling with huge amounts of data and that will benefit a lot from pattern recognition and efficient data classification. But will you ever be able to see farther than others standing on the shoulders of a database?

If you had collected a googol of examples for stable hydrogen atoms, would this have lead you to discover quantum mechanics, and all the achievements following from it? If you had collected data describing all the motions of stars and galaxies in minuscule details, would this have lead you to conclude space-time is a four-dimensional continuum? Would you ever have understood gravitational lensing? Would you ever have been able to conclude the universe is expanding from the data you gathered? You could have assembled the whole particle data booklet as a collection of cross-sections measured in experiments, and whatever you do within that range you could predict reasonably well. Bould would this have let you predict the Omega minus, the tau, the higgs?

Anderson concludes

“The new availability of huge amounts of data, along with the statistical tools to crunch these numbers, offers a whole new way of understanding the world. Correlation supersedes causation, and science can advance even without coherent models, unified theories, or really any mechanistic explanation at all.”

With data analysis only, we might be able to discover hidden knowledge. But without models science can not advance beyond the optimal use of available data – without models the frontiers of our knowledge are set by computing power, not by ingenuity. Making the crucial step to identify a basic principle and extend it beyond the current reach is (at least so far) an entirely human enterprise. The requirement that a model be not only coherent but also consistent is a strong guiding principle that has pointed us into the direction of progress during the last centuries. If Anderson’s “kind of thinking is poised to go mainstream,” as he writes, then we might indeed be reaching the end of theory. Yet, this end will have nothing to do with the scientific method becoming obsolete, but with a lack of understanding what science is all about to begin with.

PS: I wrote this while on the train, and now that I am back connected to the weird wild web I see that Sean Carroll wrote a comment earlier with the same flavor, so did Gordon Watts. John Horgan wrote about problem solving without understanding, and plenty of other people I don't know added their opinion. This immediate resonance indeed cheers me up. Maybe, science will have a chance. Leaves me wondering whether writing articles that cross the line of provocation to nonsense is becoming fashionable.

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See also: Models and Theories.

PS to Canada Day

After you could recently test whether you qualify to be German, for Canada Day the Globe and Mail offers a similar questionaire "What's the score, eh?" to see whether you'd make a good Canadian/American. I scored 6/10 for both Canadian and American (mostly guessing though). Have fun!

Happy Canada Day

July 1st is Canada Day. Seems I missed it every time since I live in Canada, much like I've missed every 4th of July while in the USA. Anyway, here is what you are supposed to do: "Canada Day is celebrated with barbeques, parades, music, and of course fireworks in the evening in most of the cities especially in Ottawa with thousands Canadian flags and Canadians singing Oh Canada." Ideally this sounds like this:



If you want to sing along, here's the lyrics, comes of course in English and French.

Besides singing and barbequeing you are apparently supposed to buy lots of stuff in red and white with a maple leaf on it, like flags, hats, towels, pens, keyrings and flip-flops that they sell everywhere from mother's day on. I am pretty sure you can equip your whole household in Oh-Canada-design if you'd try. Anyway, I am in Paris (France, not Paris, Ontario), but happy holidays to our Canadian visitors :-)

Science Mugs

On Friday I came across Corie Lok's blog who announces the "Nerdiest Science Mug Competition" and offers a DNA strand with the names of faculty members. Brian Clegg adds a global warming mug, and Bob O'Hara contributes a mug from the Metapopulation Research Group (website). I can't quite keep up with so much nerdiness, but I found my mug from the String Pheno 2004 in my husband's kitchen. Here it is:



Looks like a black hole but if one fills in hot coffee it reveals...



A Calabi-Yau manifold. (Seems to be essentially the same picture as this.) And here is the backside, just for completeness.




My favourite mug is actually my PI mug, black and stylish.

So what's your nerdy mug? (Blogger doesn't allow images in the comments but you can leave links.)

This and That

• Event of the week: Germany made it into the EURO 2008 finals! They will play against Spain on Sunday 2:45 pm ECT.


• Most bizzare news of the week: Banana over Texas doesn't fly


• If the world could vote... we could just make Obama president and save a lot of money on more campaigning.


• Picture of the Week: Sunset over Mars
  
  
  (Click for larger version. Image Credit: NASA/JPL/Texas A&M/Cornell)


• Quotation of the week:

“Out of intense complexities intense simplicities emerge.”

~ Winston Churchill

Alice and Bob

Alice: You are late. How was your day?

Bob: Sorry honey, I had to wait for t = infinity, it took forever.

Alice: Thanks for asking, my day was perfect, I was thrown into the black hole three times.

Bob: At least you get to see something, you never tell me...

Alice: You know I can't.

Bob: What am I supposed to wear?

Alice: I took out the black suit and the shirt, it's in the bedroom.

Bob: I really hope they get this information loss stuff sorted out at some point, it's terribly annoying.

Alice: I hear we'll be back to Special Relativity next week.

Bob: Oh, really? The simultaneity again? How long will it take until they've understood it!

Alice: No, something about the clicks of the Unruh detector.

Bob: Humm. Am I supposed to wear a tie?

Alice: Well, I think the family would appreciate if you'd show some respect for my ex.

Cat: Meeow.

Bob: Oh no. Did they send more packages?

Alice: Oh yes. Seems you got the dead one, I left it downstairs.

Bob: Doesn't it ever cross their mind that disposing all these dead cats isn't so easy? The neighbors already talk, I heard them last week...

Alice: You can't wear sneakers to a funeral.

Bob: Well, he doesn't care any longer, does he?

Alice: Do me the favor, it's a tragic story and I don't want anybody to think we're not serious.

Bob: Tragic? Well, he shouldn't have shot his grandfather!

Alice: We don't even know that. Do we really have to go through this again?

Bob: Well, if we'd know whether he made it to the other side of the wormhole, you must know...

Alice: You know I can't tell you!

Bob: Yah yah! Cosmic cencorship! But it's unproved!

Alice: Well, one never knows, I don't want to cause us problems. Don't you see I'm just doing this for us!

Bob: Anyway. Will Fido be there?

Alice: Don't think so. Last time we talked he had a problem with a Kerr-Newman black hole.

Bob: Good, good. Let's go. I really think we could need a vacation.

Alice: We could ask for a different branch of the multiverse tomorrow.

Cat: Meeow.

Seminar in Heidelberg

This lovely old villa is the Insitute for Theoretical Physics in Heidelberg where I gave a seminar yesterday.


[Click to enlarge]
A very warm and welcoming place with lots of wood inside, a garden and nice people! Here are three friendly faces, from left to right: Carlo Ewerz, Eduard Thommes and Thomas Dent (Thomas D you might know from the occasional comment at this blog).


[Click to enlarge]

The photo was taken from a balcony on the upper floor with a great view on the city and the river Neckar. If you peer really hard you can see the Heidelberg castle in the background.

The Black Hole Information Loss Paradox

Prologue

I am constantly fighting information loss. Most importantly, there seems to get a lot of information lost in emails I write if those exceed one paragraph. What comes back then is stochastically distributed words that are uncorrelated with what I wrote. Anyway, as I had to realize yesterday, an inbox can also turn into a black hole if IT moves the folders but doesn't tell you how to reconfigure the ssh tunnel.

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Not the Paradox

So, what is the black hole information loss paradox? The evolution laws in quantum mechanics are time-reversal invariant. (That does not include the measurement process, which does set limits to our knowledge). Initial states evolve into final states, the evolution is given by a Hamiltonian and is unitary. You can turn it back around. If you start with something it will go into something with probability one. The evolution is a one-to-one map. Unitarity is a fundamental property of quantum mechanics.

Now consider you have some matter distribution (e.g. a pressureless gas) and let it collapse (for simplicity assume it is spherically symmetric). That what you need to specify the precise state I will call information. The collapsing matter forms a horizon and becomes a black hole. The black hole no-hair theorem says that a black hole can carry only three parameters: mass, angular momentum, and electric charge. After the collapsing matter has settled down, this is the only information you can get from examining it. What happened to all the other information of your gas? All the details of that initial state?

Well, you could say, it's inside the black hole. So, no, collapse and formation of a horizon is not the information loss problem. You could say, the information still exists, but we are just disconnected from it. What's the problem with that? As long as my inbox still exists at least somewhere, that's okay, even if I can't access it.

The Paradox

But Hawking tells us black holes emit radiation, and this radiation is thermal. It is purely thermal, completely random, does not contain any information except its temperature. That is in contrast to e.g. the radiation of the sun. Which is for all practical purposes also thermal, but it does contain information 'in principle'. If you'd throw your bag of gas into the sun and you waited long enough you could 'in principle' extract its details again from the sun's radiation. Not so for the black hole. There is nothing to learn from the black hole's radiation.

Still you could say, well, if no information comes out, then it just stays inside.

But if Hawking is right, and the black hole radiates, then it loses mass. And eventually it is completely evaporated. There is nowhere left for the information to remain. The only thing that you have in the final state is that thermal radiation distributed over space. One could say then, well, black hole formation just is not time-reversal invariant. A singularity forms. A singularity is an attractor, whatever you started with it is always equally singular. There is no one-to-one map. Why is that a problem?

Well, the black hole formation could have happened for anything that forms or later falls into the black hole, and we know stuff behaves according to quantum mechanics. We have tested that experimentally uncountably many times. But if you consider an initial quantum state for the black hole, then no matter what precisely it was, the result is always thermal radiation, determined solely by the total mass, charge, and angular momentum. If you look at the final state, you can't trace it back to the initial state. It's not a one-to-one map. The evolution is not unitary, in conflict with the laws of quantum mechanics.

And that's the problem. The paradox. The apparent disagreement between general relativity and the laws of quantum mechanics. Hundreds, if not thousands of papers have been written about it since the solution to this paradox can be a key to our understanding of quantum gravity - whatever that theory looks like it should be able to resolve the problem.

Solution Attempts

A crucial aspect of this problem is that evaporating black holes are to excellent approximation classical objects for a very long time. Quantum gravity only can become important in the very late stages of the evaporation, then when the curvature comes in the Planckian regime, which happens only when the black hole's mass is about Planck mass (or its diameter of the order Planck length respectively.) Quantum gravitational effects thus can only influence the radiation in the last stages.

Various approaches have been tried to solve the problem, all have advantages and disadvantages (this is likely an incomplete list):

• Solution: The evolution just is not unitary and information is indeed lost.
  
  Problem: This is not only unappealing because it requires us to rethink how quantum mechanics works, it also leads to violations of energy conservation.
  
  Reading:
  
  Unitary Rules for Black Hole Evaporation
  Andrew Strominger, hep-th/9410187



• Solution: Black hole evaporation is modified in the late stages and black holes do not completely radiate but leave behind a stable remnant of approximately Planck mass that keeps the information.
  
  Problem: Since the initial state that collapsed could have been anything, if the information is kept in the remnant that remnant must be able to carry an arbitrarily high amount of information. This leads you to conclude there must be an in principle infinitely large amount of black hole remnants with the same mass that are however different since they have different information content. This in turn results in the possibility to pair produce these objects infinitely in any arbitrarily complicated process where the energy is high enough. Even if the probability for the production of a single remnant is arbitrarily small, if there are infinitely many of them, you will still produce them. You could also emit them in black hole radiation itself: The high energy tail of the black hole spectrum might be exponentially suppressed, but if multiplied with infinity, black holes of arbitrary mass would decay instantaneously.
  
  Reading:
  Comments on information loss and remnants
  S.B. Giddings, hep-th/9310101
  
  Constraints on Black Hole Remnants
  S.B. Giddings, hep-th/9304027
  
  Trouble For Remnants
  Leonard Susskind, hep-th/9501106
  


• Solution: The information comes out with the radiation in the very late stages.
  
  Problem: Then you have only very little energy left to carry all that information, which could have been arbitrarily much. This means per each unit of information you have a very small amount of energy to emit it which takes a long time, and you can't emit it simultaneously because if the wavefunctions overlap they'd be correlated. So that last stages would last very long (the more information needs to go out the longer) leading to quasi-stable black holes which cause essentially the same problems as the remnants of the previous point (their mass spectrum is not exactly degenerated but almost). Besides this, one would like to have an exact mechanism for how that happens.
  
  Reading:
  
  Do Black Holes Destroy Information?
  John Preskill, hep-th/9209058
  


• Solution: Black holes evaporate completely but while so have formed a causally completely disconnected baby universe in which the information survives.
  
  Problem: Requires you to believe in a multiverse in whose totality information is conserved, though locally, in our universe, it isn't.
  
  Reading:
  A Possible Resolution of the Black Hole Information Puzzle
  Joseph Polchinski and Andrew Strominger, hep-th/9407008



• Solution: Since the AdS/CFT conjecture relates black holes (in AdS space) to a quantum theory one knows is unitary on the boundary, this would mean the evolution in the bulk is also unitary.
  
  Problem: As long as the conjecture is unproved one could equally well consider the information loss problem, if real, as a counter-example for the validity of the conjecture. (Also, I personally would find it unsatisfactory would this only work in AdS space).
  
  Watching:
  
  The Black Hole Information Paradox, Past and Future
  Joe Polchinski, PIRSA: 08040001
  


• Solution: Black holes have quantum hair that is not taken into account in the no-hair theorem.
  
  Problem: Since the black hole can carry arbitrarily much information, one needs arbitrarily many quantum numbers to do that and a modification of our theories that can accommodate them. Why haven't we yet observed any of that? (Also, it's not clear to me how one would know that the black hole always carries enough of these new quantum numbers.)
  
  Reading:
  
  Quantum Hair on Black Holes
  Sidney Coleman, John Preskill and Frank Wilczek, hep-th/9201059
  


• Solution: Other - There are no black holes / There is no Hawking radiation / There is no spoon, ie we live in a virtual reality and this paradox was created just for the amusement of our programmer.
  
  Problem: Possible but far fetched.
  
  Reading:
  
  The bleakness of reality.
  

Why I voted "No for other reasons"

From how I stated the problem above, it hopefully became clear why I think the problem is the singularity, not the horizon. The horizon is where information becomes inaccessible, but the singularity is where it gets lost. That's more or less by definition what a singularity is all about. The singularity is where the evolution becomes non-deterministic, where it can't be uniquely continued, it's where all initial states are crunched into the same divergence - already classically. Unlike the classical case however, here we have a scenario where the final state is without singularity again. Thus, the slicing has somehow to pass the singularity*.

But it is generally expected that some version of quantum gravity resolves the singularity and smoothens it out. Then, there is as far as I can see no reason why the evolution should be non-deterministic if the black hole eventually completely evaporates. If there is no slice on which initially different states run together, evolution from the initial to the final state has to be a one-to-one map. Determinism isn't sufficient, but necessary for unitarity. Either way, even if avoiding the singularity would imply unitarity, the problem then was not why, but how the information comes out.

Vaguely related reading:

Black hole evaporation: A paradigm
Abhay Ashtekar and Martin Bojowald, gr-qc/0504029

The paper mentioned in the previos post by Dr. Who (Horowitz and Maldacena, hep-th/0310281) tackles this problem with the uniqueness of the state by imposing a final state boundary condition at the singularity which effectively transfers the information in the outgoing radiation. It's an interesting paper (thanks for pointing it out!), but the solution seems to me very ad hoc.

Bottomline

The black hole information loss paradox makes for an excellent topic over which to argue, because everybody has a different favourite solution. Of course I don't believe any of the above offered solutions, and of course nobody agrees with me. Anyway, here are the preliminary results of our poll "Do Black Holes destroy Information?":

From presently 146 people who voted, the majority, 37.7%, said "No, it comes out in the radiation.". A for me surprising 25.3% said yes, black holes destroy information. 16.5% including me voted "No, for other reasons.", documenting the mentioned plurality of opinions. Again surprising for me a full 8.9% voted for the remnant solution. (Surprising because whenever I say 'remnant' I get shouted down immediately.) Also 8.9% said 'Other' which includes the quantum hair option that I forgot for the poll, and 2.7% think the information survives in a baby universe.

If you didn't yet vote, vote now! If you did, has this post change your mind?

Epilogue

The one-hour phone call to Canada to figure out how to reconfigure my email client and tunnel through to my inbox goes on my mom's bill. I had to re-download 12,442 emails, but no information got lost.

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* Andrew: In the paper you mentioned by Zeh: gr-qc/0507051, he has an endstate with singularity, see Fig 1. In this case you can draw surfaces up to arbitrarily late - but finite! - times that do not reach the singularity, but this is not the relevant scenario in which the black hole is eventually completely evaporated.

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TAGS: BLACK HOLE, INFORMATION LOSS, PHYSICS

Cacti

And again I am in Germany, fighting a jetlag. School holidays just begun, everybody is talking about soccer, and today I am visiting my parents. As you might know, I lived in Arizona for a while, and some years ago I brought my mother a couple of giant-cacti seeds. (The customs officer apparently was not too worried cacti would overtake the German fauna.) My mother indeed planted the seeds and here is how the baby cacti look at age 3 years


[Click to enlarge]

And that's how they look all grown up, takes a hundred years or so


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The above photo was taken in Tucson, Sabino Canyon I think. One gets kind of used to these cacti, the really large ones are called Saguaro Cacti. During winter, Tucson has a couple of nights in which temperatures can drop below freezing point. Since the water content of these plants is quite high, to prevent the smaller arms of their cacti from freezing, people cover them with clothes or paper cups. Looks quite funny.

Browsing through my old image folder I also found some nice photos of blooming cacti: here, here, here and here.

If you think this post is pointless, that's because it is.

PS: And today is our 2nd wedding anniversary!

Black Holes at the LHC - The CERN Safety report

Earlier this year there has been a bit of confusion about potential dangers of switching on the Large Hadron Collider (LHC) at CERN. A lawsuit in Hawaii brought old fears back on the front pages of newspapers again, that the Earth may possibly be destroyed by strangelets, magnetic monopoles, instabilities of the vacuum, or black holes created in the high-energy proton-proton collisions planned at the LHC. We had discussed the actually non-existing danger posed by micro black holes in our posts Black Holes at the LHC - What can happen? and Black Holes at the LHC - again.

Yesterday, CERN has finally published the official report by the LHC Safety Assessment Group (LSAG). A CERN press release announces that the CERN Council looks forward to LHC start-up, and that the new report, updating a 2003 paper, incorporates recent experimental and observational data and confirms and strengthens the conclusion of the 2003 report that there is no cause for concern. Today's New York Times quotes from the abstract of the technical paper by Michelangelo Mangano, CERN, and Steven B. Giddings, UCSB, which is one of the pillar of the LSAG report that [...] indeed, conservative arguments based on detailed calculations and the best-available scientific knowledge, including solid astronomical data, conclude, from multiple perspectives, that there is no risk of any significance whatsoever from such black holes.

But just have a look at the report by yourself:

• A summary of the LSAG report is available (as PDF file) in English, French, German, and Italian: The safety of the LHC / Le LHC peut être exploité en toute sécurité / Sicherheit am LHC / La sicurezza dell’LHC.


• The actual report is the 15 pages Review of the Safety of LHC Collisions (PDF file) by John Ellis, Gian Giudice, Michelangelo Mangano, Igor Tkachev and Urs Wiedemann of the LHC Safety Assessment Group.


• Technical details about strangelets and black holes can be found in the 11 pages Addendum on strangelets (PDF file) to the Review of the Safety of LHC Collisions, again by Ellis, Giudice, Mangano, Tkachev and Wiedemann, and in the 97 pages paper Astrophysical implications of hypothetical stable TeV-scale black holes by Steven B. Giddings and Michelangelo L. Mangano (available as preprint CERN-PH-TH/2008-025 (PDF file) and arXiv:0806.3381 [hep-ph]).


• A review of the report and the two technical papers was prepared by the CERN Scientific Policy Committee (SPC) to provide [...] an independent opinion on the conclusions stated in those documents. SPC panel members Peter Braun-Munzinger, Matteo Cavalli-Sforza, Gerard ‘t Hooft, Bryan Webber and Fabio Zwirner came to the conclusion that they fully endorse the conclusions of the LSAG report: there is no basis for any concerns about the consequences of new particles or forms of matter that could possibly be produced at the LHC.
  This review is also available as a PDF file.

The main focus of the Giddings-Mangano paper lies on a detailed analysis of the possible creation of microscopic black holes by cosmic rays and at the LHC, and on a meticulous discussion of the potential growth mechanisms of these black holes. This analysis then allows to conclude, from the observed existence of very old and dense astronomical objects such as neutron stars, that the Earth is safe - at least from potential dangers posed by the LHC.

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TAGS: physics, black holes, LHC

Poll: Black Hole Information

I meant for some while to write a post about the black hole information loss paradox, but despite my best intentions I haven't yet come around to doing so. As a warm up, for you and me, here is a poll:



Btw, here are the results of our last poll "Does the past and the future exist in the same way as the present?" From 153 votes, 41.2% decided for "Past, present and future exist in the same sense," 29.6% for "It is only the now that exists, but neither the past nor the future." And, surprising for me, only 15% voted for "The past exists as does the present moment, but the future doesn't.". The remainder chose "Other".

Interna

When I visited PI the first time, I got a visitor information package that among other things contained the Waterloo UpTown Business and Service Directory. In this brochure I found under 'T', between 'Tea Shops' and 'Travel Agencies' the entry 'Theoretical Physics' which lists Perimeter Institute. (It's the only entry in this category.)

Yesterday I picked up the new version of that brochure, which still integrates without any fuzz Theoretical Physics with Tattoo Studios and Night Clubs. I just looked up their website: www.uptownwaterloobia.com (bia = business improvement area). Does that building shown on the header with the sentence 'An experience you'll want to come back to' look familiar? You can also search the site for businesses, where you will find the category 'Theoretical Physics' as well.

Yes, Waterloo is really a nice and welcoming place for theoretical physicists. People congratulate me on the street that Mike Lazaridis just donated another $50 Mio, and tell me how much they enjoy the public lectures. It is a very pleasant environment to work in. Meanwhile, I am trying to find a sponsor for our September conference so we can have a reception the first day. I need an estimated $1,500 as I've been told - if you have any suggestions for who might be interested in sponsoring a conference on "Science in the 21st Century", please let me know. (I applied for a grant for travel support of younger people, but even if this goes through, which I don't yet know, I probably can't use it otherwise.)

Besides this, I am going on a trip today that will imply giving some seminars and so on. I will probably be stuck in transit and jetlag for a while, so you're facing a slow time.

A nice weekend to all of you.

Pi in a Cornfield

[Aerial image © 2008 by Lucy Pringle]
This photo shows a crop formation near Wroughton, Wiltshire, U. K., reported June 1, 2008. It is about 300 feet in diameter. The angles of the circle between the steps encode the first digits of Pi, as noted by Michael Reed. For more photos see here. For more info see here. For commentaries see here. Pretty, isn't it?

What is a System?

On the weekend my confusion about the whatabouts of life, the universe and everything else temporarily reached alarming proportions. Reason was that I tried to figure out what on Earth does it mean to 'fuck the system'? I have some familiarity with the four-letter word in this expression which leaves me to wonder what do we actually mean with 'system'?

Asking myself how I and most of my colleagues seem to use the word, I would have said the system is that what is described by a model (see also: Models and Theories). Then however I made the mistake of looking into the matter (e.g. in Bossel, "Systems and Models") which produced the rather abstract definition that a system is a set with elements that stand in some relation to each other, and generally has an environment that possibly provides input and absorbs output. A dictionary further explains:

System: from Gk. systema "organized whole, body"

After I had halfways reconciled these matters, I read a book called

The Systems View of the World
A Holistic Vision for Our Time
By Ervin Laszlo

(it's only 90 pages), which is essentially about systems and piles, and sub-systems and supersystems, life and love and reproduction, atoms and cats, self-reflective consciousness - and then manages in one full sweep to declare capitalism an outdated model, ventures for all-volunteer armies, and finishes with proclaiming a new kind of religion "celebrating [...] the sudden synthesis of the quarks and of the wide diversity of microparticles as well as of atoms and molecules throughout the expanding reaches of cosmic space". Wow. The author certainly had a vision. And if you want to get really confused, try reading this.

Either way, this didn't quite clarify what a system is either. To maybe explain why my confusion, let me ask instead: What is not a system?

Lazlo goes and piles rubbish as an example (p.25). Systems, so he argues, change qualities with the elements added. But to a pile of rubbish you can add more rubbish, and all you get is a larger pile of rubbish. It makes only a quantitave difference, he writes, it does not change the 'system' as a whole.

Now if I think in terms of mathematical definitions I can very well understand there's things that are not systems. But if I look at the real world I can't find no example for that. Everybody who is familiar with rubbish (and as a blogger I certainly am) knows that rubbish usually doesn't just orderly add up -it can develop some dynamics on its own. The pile Lazlo discusses just reminds me of the sand-pile model, a well known example for a dynamical system with self-organized criticality. So, here it goes again, we have a 'system'. The only example I can think of where one could have, in Nature, a set of somethings without any relation (interaction) between the somethings is some sort of multiverse. The analogy to Lazlo's pile of rubbish is striking.

But if everything is a 'system' then what is it good for talking about systems? Well, the usefulness of thinking in terms of systems is one of classification. One can have varios forms of systems with specific properties. Open and closed systems. Systems in equilibrium. Biological systems. Self-aware systems. Political systems. Social systems. Academic systems. Complex systems. Their elements are typically sub-systems and they are further part of super-systems, so one gets a whole hierarchy of nested systems within systems - that span all of science.

And then you go make models of these systems, find suitable variables, extract relevant parameters to try to understand the system and make predictions. Within the appropriate limits you can neglect the details of the sub-systems and talk about the system and its properties as an 'organized whole'. Might that be neglecting the quark content of molecules in a system called 'cell', or neglecting the hair color of scientists in a system called 'academia'. This procedure of neglecting finer structure and details is widely used, even within physics itself, e.g. if you think about effective theories.

I guess what confused me about this book is the author's proclamation of a paradigm shift and a change towards a "holistic vision", against reductionism, and for abandoning the "mechanistic worldview of the classical disciplines" (he seems to have a problem specifically with physics). Anyway, I think this paradigm shift just passed me by.

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PS: Has clarified, thanks to Andreas.

Discover Interview with Tegmark

Discover has a nice interview with Max Tegmark

Is the Universe Actually Made of Math?
Unconventional cosmologist Max Tegmark says mathematical formulas create reality,

where he talks about all of his four levels of the multiverse. It's quite entertaining to read. I have previously written why I think the mathematical universe hypothesis is nonsense unjustified, to summarize it very briefly: just because we (i.e. human beings) don't know anything except maths without 'human baggage' it doesn't follow from this it is the only thing there can be. Call it The Principle of Finite Imagination: The capacity of the human brain is finite. It is very possible that we simply aren't able to understand 'what' the universe is or why it works how it works. For my general problems with reality, see comments to the Block Universe.

But anyway, despite my disliking of its content, Tegmark's paper is as courageous as entertaining and bestowed this photo series upon you. If I have to read that

Tegmark has pursued this work despite some risk to his career. It took four tries before he could get an early version of the mathematical universe hypothesis published, and when the article finally appeared, an older colleague warned that his “crackpot ideas” could damage his reputation.

and

Q: Right from the start you tried to get this radical idea of yours published. Were you worried about whether it would affect your career?
A: I anticipated problems and did not submit until I had accepted a postdoctoral appointment at Princeton University [...]

it sounds to me like there's something really wrong with the academic system. If young people are afraid of pursuing their interests because it might damage their career this is likely to result in a self-reinforcing deviation of the topics that are investigated from those that are considered interesting. How can you expect science to work under these circumstances?

PS on Information Overload

As a PS to my yesterday's post on Information Overload, its dangers, and the question whether we might be making a mistake that we won't be able to correct, here is a brilliant article by Nicholas Carr in the recent Atlantic issue

Is Google Making Us Stupid?
What the Internet is doing to our brains

[...]

Over the past few years I’ve had an uncomfortable sense that someone, or something, has been tinkering with my brain, remapping the neural circuitry, reprogramming the memory. My mind isn’t going—so far as I can tell—but it’s changing. I’m not thinking the way I used to think. I can feel it most strongly when I’m reading. Immersing myself in a book or a lengthy article used to be easy. My mind would get caught up in the narrative or the turns of the argument, and I’d spend hours strolling through long stretches of prose. That’s rarely the case anymore. Now my concentration often starts to drift after two or three pages. I get fidgety, lose the thread, begin looking for something else to do. I feel as if I’m always dragging my wayward brain back to the text. The deep reading that used to come naturally has become a struggle.

If you read one article today, read this one.

Information Overload

Sorry for having been quiet the last days, I've been busy with too many things and I'm running behind on scheduling some upcoming trips (not to mention preparing the seminars attached to it).

If you have been following this blog for a while, you know that I'm skeptic when it comes to an evaluation of assets and drawbacks of the new online connectivity as to whether it is the assets that weigh more. The bottomline of my posts most often is of the form: Change happens somehow, we'll have to figure out whether it's a change for better and if not, readjust it. (If you memorize this sentence, you'll pretty much get the essence of everything I write). The big question is whether there can be change that hinders its own readjustment which in my post Cast Away I referred to as the 'Fiesta-Feature' - the problem you cause when putting the keys in the trunk that will lock on close.

One of the problems I have been writing about is Information Overload:

“[I]nformation overload is not only caused by the sheer volume of information, but also because of the complexity or confusing structure of information that might overtax the user’s cognitive skill to focus on relevant information ... Therefore Helmersen et al. (p. 2) characterize information overload as “difficulties in locating, retrieving, processing, storing and/or reretrieving information due to the volume of available information.” Information overload may lead to stress, health problems, frustration, disillusionment, depression, as well as impaired judgment and bad decision making ... From an ethical perspective, these consequences of information overload are problematic, because they undermine several basic principles, especially the requirement of participants’ autonomy/self-determination and the nonmaleficence principle.”

Behr, Nosper, Klimmt & Hartmann (2005) Some Practical Considerations of Ethical Issues in Virtual Reality Research, Presence Teleoperators & Virtual Environments 14:6, 668 (2005).

In my post The Spirits That We Called we've been discussing some secondary problems caused by the fact that information people indeed process isn't just what is available, but what is cheaply available. Faced with an overabundance of information, this potential input has to be filtered somehow, and ideally so without much effort - this is what eventually determines what is most likely to be read by many people. This cheapness is becoming more and more important, esp. for our political systems, and is unfortunately a factor that can easily be influenced with money and power. So much about democracy.

Either way, another question that I've raised in the post Can Technology Make us happy? is the conflict of short-term pleasures with long-term happiness. This is pretty much a problem of addiction (though not necessarily in the clinical sense), may that be to TV, online games, constant email checking, or blogging. The question is whether and how such developments will be corrected.

Especially when it comes to email, this is by now a fairly well documented one, as you can see e.g. from the quote about information overflow above, and companies are starting to draw conclusions from that. Among others, Loblaw, U.S. Cellular Corp (via Daily Commercial News) and Intel introduced the E-mail free Friday (via USA Today). Also the Departments of the Canadian government have urged their employees to turn off BlackBerries over night.

The Globe and Mail recently wrote in an article titled No e-mails, please. I'm trying to work

"But now there's a growing awareness that these technological tools can distract us from our work, filling our days with interruptions that, while work-related, prevent us from thinking carefully for any unbroken stretch of time.

That's one reason why companies such as Loblaw, Intel Corp. and U.S. Cellular Corp. are enforcing e-mail-free days, or restricting BlackBerry use in the office.

Others set aside time for creative thinking: Google Inc.'s 20-per-cent rule allows engineers to spend one day a week working on ideas that aren't in their job description. Gmail and Google News both grew out of ideas conceived during 20-per-cent time."

The reason why self-correction works in this case has, unsurprisingly, a priori nothing to do with happiness but with profit. Constantly checking email can be a productivity killer, which is why a small but growing number of companies are trying to do something about it.

It is in this regard very interesting that I read today in the NYT

Lost in E-Mail, Tech Firms Face Self-Made Beast

[...]

Some of the biggest technology firms, including Microsoft, Intel, Google and I.B.M., are banding together to fight information overload. Last week they formed a nonprofit group to study the problem, publicize it and devise ways to help workers — theirs and others — cope with the digital deluge.

[...]

The fractured attention comes at a cost. In the United States, more than $650 billion a year in productivity is lost because of unnecessary interruptions, predominately mundane matters, according to Basex. The firm says that a big chunk of that cost comes from the time it takes people to recover from an interruption and get back to work.

Companies are also realizing that there is money to be made in helping people reduce their digital gluttony. Major corporations around the world are searching for ways to keep software tools from becoming distractions, said John Tang, a researcher at I.B.M., who is a member of the new group."

For me, the big question is though how long will it take for academic non-profit organizations to realize the processing capacity of the human brain is finite. Unfortunately, instant email reply and reliance on being read is a peer-enforced group problem that is very unlikely going to be solved on the individual level.

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TAGS: INFORMATION OVERLOAD, FIESTA FEATURE, EMAIL