Posts by klasm

1) Message boards : Cafe LHC : What will CERN do if they create a black hole? (Message 10487) Posted 28 Sep 2005 by klasm Post: Meckano:"What's your point? Inability to use words just means we don't know it well enough. Don't give up, expand your vocabulary, have hope, dream... " Not being able something in a everyday vocabulary is not just a matter of knowing something well enough. Our language and our senses are set up to deal with everyday things and things which we can detect directly with our senses. When we begin to deal with things outside that range it is not surprising that our language is insufficient. Let's imagine that you have gone to an island where everyone is completetly colourblind and can only see black and white and shades of grey.( There are hereditary disease with that effect). You now tell them that the sky is blue and so is the ocean. They don't even have the word blue and you will have a very hard time trying to explain even the concept of colour to them. Some would probably say that you are silly and that those are just different shades of grey. However if they knew about the physical properties of light you could explain that you have the abillity to directly see the frequency of light and that different things reflect different frequencies. They could then use a spectrometer to confirm that light refelct from things you said were blue indeed had similar spectral properties. They would still not be able to experience colour directly themselves but they could use spectrometers to register them and they could discuss them in terms of frequencies. They could even combine them and produce coloured paint. Here a mathematical description of colour does now let them deal with a propterty which they can not experienc directly or have a good vocabulary for. You yourself would have the same problem if a bat tried to explain what a forest looks like when it is seen using the bat's sonar. Again this is much like our own problem when we deal with e.g quantum mechanical phenomena. Our senses were never developed to deal with those things directly, and they are different from the things we are used to, but using machines we can detect them and we can use mathematics to deal with them. You also asked about imagination and thought experiments. They are both very important parts of any researchers day to day work. Howver thought experiments are only useful when they can also be given a mathematical form and be analysed. Einsten was very careful to set up all his thought experimetns that way, and it was also thanks to that which Niels Bohr could explain how many of them fit into quantum mechanics. Gravityboy: "... you want to describe the properties of some of the very non-"every day" objects using everyday math." Well if you are willing to trust me on this, you might not be, I can say that many parts of modern day research level mathematics is very very far from "every day". Much of the mathematics that is needed for doing things like string theory is quite down to earth compared to some other areas. Regarding what you said bout agreeeing with experiments and still begin wrong: It is nice when experiments agreee with our theories, it makes peopel feel good and sometimes even champagne corks fly, but the really important thing is when experiments do not agree with theory. that is when we have found something new and may have to refine our models. This is exactly why it is so important that a theory can be used to predict the outcome of experiments before they are done. That way we can test a theory and see if it wrong, but we can never say for sure that it is right. Again you only need to give a mathematical formulation of your theory and find some effect which it predicts to be different from the theories which you dislike. If you present your case in a precise way so that others can first check your calculations, someone will then do the experiment and you will find out. This is what any researcher in physics needs to do.
2) Message boards : Cafe LHC : What will CERN do if they create a black hole? (Message 10464) Posted 27 Sep 2005 by klasm Post: Yes I read his webpage before I made my first comment about it. There is no reason to hope that physics will become any easier to descbribe in vereyday terms than now, for the simple reason that we know that there are a lot of things which do not at all behave like normal everyday things. Ther are e.g many quntaum mechanical phenomena, which we have observed experimentally, which have properties which no everyday object have. The reason for using mathematics when dealing with most of physics is not just accuracy but also that it is the only way we can describe the properties of some of the very non-"every day" objects. There are many pictures used in popular science, like the "ball on rubber" description of curved space which gravityboy dislikes so much, which try to formulate things in everyday terms. However this is not at all the way we work with these things when doing research. These picutres try to get _some_ of the properties across in a nice way, but they are only incomplete parts of the original model, and in other properties not correct.
3) Message boards : Cafe LHC : What will CERN do if they create a black hole? (Message 10462) Posted 27 Sep 2005 by klasm Post: Well with the risk of once again being accused of more or less being responsible for stoping the development of mankind I will add something more to the discussion. The fact that it is thanks to phyicists, engineers and mathematicians like myself and our friends at CERN that we have things like computers and internet where "gravityboy" can post his theories refutes those accusations quite well. I think one of the main problem for gravityboy is that he wants all of physics to be explainable in more or less everyday terms which he can understand. Things which he can not understand or picture get the label "ridiculus" and he gets upset at others for using them instead of his fluxtheory. If gravityboy wants his theory to be tested and used as a theory of physics he can do that easily. First define what all his concepts are and write down a mathematical formulation of the theory. The mathematical fomrulation will then have to do two things. 1. It must be possible for it to accurately descbribe all pehomena that we have already observed. Like how much light bend when it passes close to a large mass like the sun. If it doesn't agree with these observation then it is in trouble. 2. It should be possible to use to predict the outcome of new experiments sothat it can be tested by the people doing experimental physics. If it only predicts exaclty the same things as other theories there is not much point in using them as separate theories One of the reason for why it is important to have a mathemaical formulation under point 1. above is to avoid things like the "It is God's wish"-theory. This is the simplest theory of physics you can find and has the same answer to all questions. "Why does the earth orbit the sun? It is God's wish!" However it is a useles scientific theory because it can't be used for anything apart from "explaining" things already observed.
4) Message boards : Cafe LHC : What will CERN do if they create a black hole? (Message 10349) Posted 21 Sep 2005 by klasm Post: Meckano: A short reply before I get on with my work for the day. 1. Nowadays we can actually see individual atoms. Modern electron micrscopes can btoh see and move individual atoms. We can actually build things atom by atom. Very small things that is. However one must be very careful trying to imagine an atom in anything like everyday terms. The old school book picture of eclectrons flying in circles around the nucleaus is really quite missleading. Electrons, protons and neutron look nothing like this in th real world. There really are no everday thigns we can compare them to, not matter how much we would like to do so. The flux guys way of descirbing things i even worse than this and wioll just lead your intuition wrong. There is plenty of good popular science which tries to explain about these things but he does not belong there, and unfortunately much of what one finds on the Net is quite bad too. 2. Again compressing pillow fileld ith feathr is not a good analogue of what goes on here. In that case you are compressing it by letting air out. IF you had put in a hydraulic press you could have compressed wit ha air and everything, not letting anything out. When you compress atoms to form neutron stars or other dense object you do not need to let anything out. There is no occupied volume which needs to move out of the way. 3. Some kinds of gravity waves come out in only some direction, others in all directions. The reasons for jets and accretion discs around black holes has nothing to do with outflowing empty space. The reson these things look like they do is connected to the rotation of the black hole and would take me some time to explain, so it will have to wait for another time.
5) Message boards : Cafe LHC : What will CERN do if they create a black hole? (Message 10347) Posted 21 Sep 2005 by klasm Post: Alex and Meckano: Do not go to the "flux guy" for advice about how physics or mathematics works. Most of his writings are complete nonsense, both as physics and mathematics, and that's my view as a professional mathematican. When you work in a physics or mathematics department you get sent things like his works regularly, sometimes its nonsense enough that anyone can spot it and sometimes you need to know quite a bit of mathematics to be able to tell. Regarding the "compressibillity" of space I can not really understansd what you are trying to describe Meckano. There is no need for space to move out of the way when you compress matter. You will see space getting more and more curved as the density of matter and energy in a volume of space increases but you will not see anything like a fluid flow out from that volume as it get more and more compressed. In the paper you refered to on physicstoday they discussed plane gracity waves not "gravity wave planes". The former is just a special simple form of gravitational wave.
6) Message boards : Cafe LHC : What will CERN do if they create a black hole? (Message 10247) Posted 17 Sep 2005 by klasm Post: Meckano: I'm afraid I can't quite follow your question. It is the case that graviatation affects how fast time is. As you get closer and closer to a large mass your time will slow down in the eyes of a far away observer. This is not an effect specific to black holes, it is in place around any mass, like the earth. This has actually been measured on earth. One has compared how fast time change for atomic clocks when they are on sea level and when they are high up in an aeroplane, one needs to factor out some effects due to the aeroplane's motion but that can be done, and one that the clock in the plane moves a little bit faster. Around earth this is _very_ small difference but near the event hoirson of a black hole it will be very strong. You could see the seconds of someone close to the horison get strectched into millenia. If you want to find out more about these effects without going into the mathematics behind it, not everyone looks forward to some nice math :-), I can recomend Nigel Calder's "Einstein's Universe". Its a few years old but still a good read.
7) Message boards : Cafe LHC : What will CERN do if they create a black hole? (Message 10233) Posted 17 Sep 2005 by klasm Post: Alex: One of the good things here is actually that we all get the same black hole, no matter which part of physics we start out with. General relativity and string theory say different things about what goes on inside the even horison of blacck hole but from the outside we see exactly the same thing. Both theories predict the same bending of space time outside the hole. In fact one of the things taken in favour of string theoyr is that it agrees well with general relativity on this point. Remember that string theory has been created to be a refinement of general relativity ans so will give very similiar results in most situations. One of the things theo theories agree on is that once you get a high enough energy density you will create a blavk hole. The "normal" black holes that peope talk about are formed in supernova explosion at the end of the life of a large star. What happens there is exactly that the core of the star has so high mass an densit yt that it begins to contract and under some cirumstances reaches the density needed to form a black hole. Not all supernova form black holes though, for stars of a very large mass the supernova actually blows the star away completely. There is also believed to exist a class of fairly small black hoels which were created by the random density variations in the big bang. The final evaporation of black holes of this class is one of the candidates for explaining some of the gamma ray burst that has been obsevered from large distances in space.
8) Message boards : Cafe LHC : What will CERN do if they create a black hole? (Message 10215) Posted 17 Sep 2005 by klasm Post: David: The important thing here is not mass but density. If you get a high enough density Take the whole milky way as an example of something with enormous mass, much larger than any of the black holes in the mily way. It does not form a black hole since that mass is spread out in a very large volume of space. On the other hand, if you take a small mass and compress it enough you will create a black hole with small mass. If you take something with the mass of a cup of coffe you will have to compress it into an extremely small volume before it becomes a black hole. But it can be done. There is a simple mathematical formula that tells you exaclty how small a wolume you need to compress any given mass into in order to create a black hole. So the important thing is density, not mass in itself.
9) Message boards : Cafe LHC : What will CERN do if they create a black hole? (Message 10200) Posted 16 Sep 2005 by klasm Post: Reply for Meckano A black hole which is far from any matter, eg not insid a galaxy or just in an empty part of galaxy is more or less unfed. but the microwave background radiation will still feed it energy no matter where it is. However the microwave background is getting less end less energetic as the uinverse gets older. So after a _long_ time it will be cold enoiugh that any black hole will radiatte more energy than it gets from the microwave background no matter where it is. So in the long run any black hole will evaporate. A small black hole wil radiate so much energy that it will loose mass faster than you can send it into the hole, no matter which environment it is in.
10) Message boards : Cafe LHC : What will CERN do if they create a black hole? (Message 10198) Posted 16 Sep 2005 by klasm Post:
11) Message boards : Cafe LHC : What will CERN do if they create a black hole? (Message 10189) Posted 16 Sep 2005 by klasm Post: Interestingly enough, no. Thanks to quantum mechanical effects black holes are not completely black. They constantly send out radiation making them loose a certain amount of energy. A black hole with a given mass has an effective temperature radiating this way. The smaller the mass the higher the temperature. A star mass black hole will have a temperture so low that it actually get more energy from the current background radiation in the universie that it will gain more mass from that radition than it loses from what itself emits. A black hole the size of an elementary particle however has so high temperature that it loses more than it can absorb, and the more it looses the smaller it gets, and so gets even warmer and looses energy even faster. That way a small black hole will evaporate itself away completely in an extremely short time. It will either leave just a swarm of particles behind, or possibly something new as well. For example Gary Horowits has found that if string theory is correct an electrically charged black hole might leave behind something called a Kaluza-Klein "bubble of nothing" Which in some sense is a missing piece of space time. We are quite certain about this general picture but the details depends on things which we still do no know, like the number of dimension of the universe and their sizes. LHC will be able to gives us some answers to those questions, both by producing black holes and by not doing so.
12) Message boards : Number crunching : CPU-Power (Message 10155) Posted 14 Sep 2005 by klasm Post: sounds like roughly equivilant to an IBM cluster running 768 Opterons @ 2.0GHz seems a bit low for what, nearly 10.000 active hosts? Not really. Let's assume that most hosts are running 3 projects, we're down to a bit over 3000 fulltime hosts, further at least half of them are slower than the opterons, takes us down to about 2000 hosts, and most of these machines runs the screensaver and so work only when the machine is not used by its owner, were down to around 1000 or less. All very rough estimates of course, but the final size sounds reasonable.
13) Message boards : Number crunching : This is what comes after Sixtrack... (Message 10084) Posted 12 Sep 2005 by klasm Post: In which case all of the toys for that problem are turned into scrap. Not really. Usually people are quite inventive when it comes to finding new interesting uses for machines once their original task is done. If scientific equipment is suddenly scraped it is usually for political reasons. like the american moon program being canceled when there was no russian reply to it.
14) Message boards : LHC@home Science : re:4th STATUS REPORT FOR THE USERS OF LHC@home (Message 10071) Posted 11 Sep 2005 by klasm Post: There will be an enormous amount of energy in the LHC beam. It has been computed that the proton beam from the LHC could work its way through 30m of solid copper. Likewise a swarm of proton from the LHC will have the energy to melt about 500kg of copper. So doing simulations in advance is a good idea. It has been suggested that one could use the LHC to create collisions like this, but with special targets, on purpose to study the plasmas created in the collision.
15) Message boards : Number crunching : hoarding (Message 10063) Posted 11 Sep 2005 by klasm Post: for science reasons lhc@home can neglect the donators choices? Yes. The only reason that this project exits is for it to acomplish scientific work. If a volunteer has choosen settings which do not work well with this, or any other project, he or she will have to stay with different projects. lhc@home made a choice to use boinc. this includes the donators choices. No. LHC, and any other project, will chose their optimal way to work and then it is up to us volunteers to chose projects which works well with our particular combination of hardware and internet access. Doing it the other way round would be a bit like asking victims of war to get injured in a nicer place so the red cross volunteers didn't have to endanger themselves. However I agree that it would be a good idea for both LHC and the other projects to state something about eg deadlines on a visible place on their web site. It is available on this website already but maybe one should put it up together with the other information about the unumber of WUs at various stages.
16) Message boards : LHC@home Science : re:4th STATUS REPORT FOR THE USERS OF LHC@home (Message 10029) Posted 10 Sep 2005 by klasm Post: Out of curiosity, why do the beam instabilities interest you? If the LHC is run with a setup leading to an instable beam the beam can crash into the the wall of the vacuum ring. The LHC beam has so much energy that this can destroy the wall, damage the detectors and lead to very expensive repairs and iterruption in the experiments. LHC@home helps the designers find out which combinations of machine paramters are safe to use when the LHC begins operating.
17) Message boards : Number crunching : Resigning due to short deadlines (Message 9823) Posted 1 Sep 2005 by klasm Post: Remember that BOINC will try to make sure that it runs the projects according to your set percentages seen over a LONG period of time. If LHC has short deadline and therefore momentarily gets more time than the percentage you have set that will then be compensate for. However this will only be the case when you let the client run untouched for several weeks. If you have too many projects atatched, and they have very different deadlines, you willl most likely see even more short time variatation in this. Not all combination of projects are good if you want balance on very short time scales, like a week, and there is no way around that, except an extremely small cache. LHC has not abused anyone. It has set its paramters according to the needs of the the project, and after that it is up to every user to see if they are willing to work within those limits. As far as the project is concerned there can not be anything seriously wrong with the parameters as long as the number of active users is increasing, since that means that the project is still getting more and more done.
18) Message boards : Number crunching : information should not be that difficult (Message 9762) Posted 31 Aug 2005 by klasm Post: One of the good things, for the science of the project, with send a WU to five persons while requiring three for quorum is that it reduces the risk som WU getting stuck with either someone grabbing too many WU, or just someone who for random reasons weren't able to connect and upload their results. As has been said before, most of the WUs are done nicely and quickly and a small number of WUs take a lot longer. Where the optimal balance here in terms of project completion time is of course something the project administrators will have to experiment with to find out. As usual the optimal thing for the science part of the project is that everyone keeps their caches as small as possible and connects often instead. Even though this might not optimal for those who want to collect credit it can be better for the project to have someone without work while others keep on working. One can also not assume that one should be able to run just any combination of projects with the hardware and connection one has. The projects behave differently due to their different scientific needs, and not all combinations are good.
19) Message boards : Number crunching : Network connection interval greater than wu deadline (Message 9734) Posted 30 Aug 2005 by klasm Post: Estimating the time a WU will take is harder on LHC@home than for many of the other projects. If the WU creates an orbit which is instable it can finish very quickly. Fiding out when orbits are stable is the point of this projects so varying WU times is unavoidable.
20) Message boards : LHC@home Science : If Neutrinos have no mass, can they escape a black hole? (Message 9652) Posted 25 Aug 2005 by klasm Post: ...and by doing so the black hole loses an amount of energy correspoding to the absorbed particle rather than gainging it. So the black hole loses part of its energy/mass in the creation of the the particle which flies away.

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