Catch up on stories from the past week (and beyond) at the Slashdot story archive

 


Forgot your password?
Close
typodupeerror
×
Science

Black Holes and Hidden Dimensions 200

Posted by Hemos from the looking-into-my-other-universe dept.
Slackware Geek writes "It is being reported in the Nature Science Update that a new observitory being built in Argentina to study cosmic rays could detect extra hidden dimensions if they exist. 'Cosmic rays could find holes in Standard Model of particle physics ...If the Universe contains invisible, extra dimensions, then cosmic rays that hit the atmosphere will produce tiny black holes. These black holes should be numerous enough for the observatory to detect.'"
This discussion has been archived. No new comments can be posted.

Black Holes and Hidden Dimensions More

Black Holes and Hidden Dimensions

Comments Filter:

  • Miniature Black Hole (Score:4, Interesting)

    by alfredw ( 318652 ) <alf@[ ]ealf.com ['fre' in gap]> on Monday January 14, 2002 @07:51PM (#2839050) Homepage
    Does anyone know how this works? Is this detecting the Hawking radiation from an evaporating hole, or is it detecting other effects?

    • Re:Miniature Black Hole (Score:4, Informative)

      by spiro_killglance ( 121572 ) on Monday January 14, 2002 @08:11PM (#2839149) Homepage

      Yes they would be detected by the shower of particles produced by the (very rapid) Hawking radiation decay of the black holes. Its in the article except they didn't mention Hawking radiation by name.

    • Re:Miniature Black Hole (Score:5, Informative)

      by mreece ( 38002 ) <mreece@midway.uc ... .edu minus berry> on Monday January 14, 2002 @09:39PM (#2839549) Homepage
      >Is this detecting the Hawking radiation from an
      >evaporating hole, or is it detecting other effects?

      Yes, this is essentially what happens. The decay is actually somewhat more complicated; there is an initial "balding" phase in which the black hole loses its hair, along with a "spin-down" phase... after this, there's a very quick evaporation with high sphericity. Go to http://arxiv.org and search for "black hole production"; some recent papers by Giddings have details. It was believed for a while that the cross-section is geometric, which would lead to a good chance of detecting these in the next generation of colliders if large extra dimension (LED) models are correct. A paper by Voloshin indicates, on the other hand, that the cross-section is really exponentially suppressed by the black hole action. I'm not sure this has quite been settled completely.

      The basic idea behind all this, by the way, is that there may be extra dimensions which are large compared to the Planck scale (up to a millimeter in size - that's about as far as gravity has been probed!). Gravity would be a field in "the bulk", that is it propagates in all the dimensions, but the standard model fields are localized on some sort of 4-dimensional "brane." There are actually a couple of different models with large extra dimensions - one is the ADD model (Arkani-Hamed, Dimopolous, Dvali) and another is the Randall-Sundrum or "warped extra dimension" model. Searching on arxiv.org for any of these names should get you links to the papers.

      The basic reason for looking into all of this is the hierarchy problem, namely that the gravitational force is far weaker than the other forces. The electroweak scale is on the order of one TeV (= trillion electron volts, where one electron volt is about 1.6*10^-19 Joules). Gravity, on the other hand, is associated with a much higher energy scale. To explain this, the ADD model proposed that maybe the fundamental Planck scale is actually on the order of a TeV, like the electroweak scale. In other words, they solve the hierarchy problem by saying there is no hierarchy. Gravity propagates in more dimensions, so that its effect in our four-dimensional part of the universe looks much weaker. The other fields are localized in such a way that this ratio doesn't take any effect for them, so we see them at the "true" Planck scale on the order of a TeV.

      It just so happens that the TeV scale is what we're looking at with current colliders, which is why there's so much interest in this lately. But cosmic rays give an alternate approach. Keep in mind that these ideas are very speculative, but still worth looking into.
      • The basic idea behind all this, by the way, is that there may be extra dimensions which are large compared to the Planck scale (up to a millimeter in size - that's about as far as gravity has been probed!).

        I find that amazing! Now if the theories allowed for those extra dimensions to periodically grow to sizes large enough to swallow single socks and small toy cars, I'd call it a very significant development.

        Seriously, I'm amazed that gravity hasn't been experimented with on smaller scales. Would that be something that requires zero-g and objects in a vacuum, or do you get other problems, like electrostatic/electromagnetic forces or even gravity of surrounding objects on those scales that make gravity difficult to measure directly at that resolution?

        • >Seriously, I'm amazed that gravity hasn't been
          >experimented with on smaller scales. Would that be
          >something that requires zero-g and objects in a
          >vacuum, or do you get other problems, like
          >electrostatic/electromagnetic forces or even
          >gravity of surrounding objects on those scales that
          >make gravity difficult to measure directly at that
          >resolution?

          Apparently the current limit is now somewhat less than a millimeter, but still on the order of a millimeter. Yes, it is very difficult to test. A group at the University of Washington has developed small-scale gravity tests; see http://www.npl.washington.edu/eotwash/shortr.html for an explanation.

          Basically, you have the right idea; it's hard to screen out all of the other effects at a scale that small, which is why studies at the millimeter scale are extremely difficult.

  • Must resist... (Score:4, Funny)

    by imrdkl ( 302224 ) on Monday January 14, 2002 @07:52PM (#2839051) Homepage Journal
    Black holes, expensive science project, currency devaluation, it's got potential, yes? Anyways, a different dimension would at least give them a new place to search for a president...

    Moderators, punish me now.

    • Re:Must resist... (Score:3, Insightful)

      by barawn ( 25691 )
      I do just want to clear things up -

      Argentina didn't come up with this science project - the world did. It's an international collaboration of dozens of countries and about 300 scientists worldwide. Argentina was chosen as the southern site of the array due to the location - the array consists of a flourescence detector, which requires stable weather and clear air. The northern site is still under discussion, though it seems most likely to be in Utah (along with the dozen or so other cosmic ray observatories in Utah).

      The Auger collaboration is then completely distinct from Argentina's government, so we don't really worry about the governmental problems except for the problems they cause our friends down there and the Argentine portion of the collaboration.
    • Anyways, a different dimension would at least give them a new place to search for a president...

      Ahhh. Hopefully, it'll be a pretzel-proof dimension.
      • Ahhh. Hopefully, it'll be a pretzel-proof dimension.

        No, that's American presidents. They'd be better off looking for a dimension full of spanish speaking Alan Greenspan clones willing to run.

        (Note to anybody who takes that wrong - America had Herbert Hoover for their financially inept leader, and in comparison Clinton *and* Bush look good, either choking on a pretzel or choking an intern with his...)

        --
        Evan

  • `Width' of a single atom (Score:2, Interesting)

    by joebp ( 528430 )
    Many physicists now argue we cannot experience these extra dimensions directly because they became rolled up more tightly than the width of a single atom during the Big Bang.
    Wow, how scientific.

    There's more information about the Pierre Auger Project here [auger.org].

    • Do you have a problem with the concept of 'width of a single atom' or what are you saying? Or perhaps radius would be a better word? Of course, the radius of an atom is not something which is very precisely defined due to quantum mechanics. IIRC, a common definition of the radius of an atom is the value r for which (formula in LaTex) \int ^{r}_{0}dr\int d\Omega \Psi ^{\dagger }\Psi >0.5 where \Psi is the normalized wavefunction for the atom. Of course, determining \Psi for anything more complicated than a He atom is a many-body problem with no analytical solution (supercomputers here we come!).
      • Uh oh... To correct myself, the He atom is no longer analytically solvable, only the H atom is. Of course depending on whether you are calculating electron orbitals or the nuclear structure. I.e. for electron structure, a proton with only one electron orbiting it, and if you're calculating nuclear structure the deuteron nucleus (1 proton + 1 neutron) are the most complicated things with analytical solutions. The rest is more or less daring approximations, and number crunching...:)
      • the radius of an atom is not something which is very precisely defined due to quantum mechanics
        Indeed. What I was trying (unsuccessfully I must admit) to communicate is that relating something to the size of an atom is like measuring my head with an elastic ruler, for the reasons you give.
      • > any physicists now argue we cannot experience these extra dimensions directly because they became rolled up more tightly than the width of a single atom during the Big Bang.

        Do you have a problem with the concept of 'width of a single atom' or what are you saying? Or perhaps radius would be a better word?

        Width or radius, neither would matter. "During" the big bang (0 - 5 seconds for example), there were no atoms. The universe was far too hot for any to form.
    • Actually, as I've stated elsewhere, the best information on the PAO is here [auger.org.ar], because this is the Argentine site, where we're actually doing things. Most of the stuff on auger.org is administrative and outreach stuff - if you want to find out what's actually going on, check out the Argentine page. If you notice, it's actually rather active! (Check under the CDAS page for a better list of the milestones we've reached).

  • "Extra" (Score:1, Interesting)

    by Anonymous Coward
    Extra is the wrong word; "undetected" or "hitherto unseen" is more accurate. Extra implies "laws of nature" and similar nonsense that the cult of science preaches to the guild.

    Any other dimensions that are there are already existing, and are not "extra" or in addition to whats in the universe.
    • "Undetected" or "hitherto unseen", I'll agree with. I do not get your reasoning for "extra" implying "laws of nature", nor do I see how science is a "cult."
  • Black holes are weird things. I mean, think about it, something that is strong enough that light can't even get out of it. And like it warps space. That's deep...
    • Yes but if you accept the fact (fairly well proven) that all matter warps space, then black holes aren't all that strange anymore. If everything warps, space, then it becomes fairly obvious that something dense enough will warp it to the point that it's inescapable.
  • Every time I read kooky sounding things like this, I want to shake my head and sigh, but then I think that is probably what a crapload of people were doing when Goddard was sitting around playing with frames and fuel and just feel that weird, "Damn, they could actually be on to something," feeling. I'm just waiting for some religious scholar to do something similar so I can be the first man to fly into the sun and have bragging rights in the afterlife for most badass exit.

  • circular/spherical space-time (Score:5, Insightful)

    by carambola5 ( 456983 ) on Monday January 14, 2002 @08:03PM (#2839111) Homepage
    I wonder if this [mit.edu] can shed some light on the subject. It talks about modeling a universe where light naturally travels at a fixed radius rather than a straight line. Assuming the radius to be extremely large, the proposed universe would act quite similarly to ours. Assuming an extremely small radius (small as in atomic-level) and I think we may be hitting upon the door of the next dimensions.
    Think of it... In a world where light traveled in a fixed radius of one meter, you would see the back of your head if nothing is in the way. And, it would seem, that your head is 6.28 meters away from you. Problem is, you wouldn't be able to see beyond that one-meter radius circle. Now, what if that radius was shrunk to the atomic level... you wouldn't be able to see beyond the circle(sphere?) that the fixed radius spans. Obviously, your eye is way too large to detect that kind of precision.
    Thoughts anyone?
    • It's just a hypothetical "universe" for use in a mathematics class, and someone wrote ray-tracing software to determine what vision would be like in that universe. I don't see that having any bearing on physics in this universe!
      • First of all, it's believed that these other dimensions are so-called "curled up," meaning that there is some sort of circular attribute to them. Taking this into account, I remembered viewing that website and put some ideas together:

        Think of what the author said in terms of particle physics. He/She looked into a world where photons moved in a circular fashion. If the radius was big, it'd be just like our current universe. If it was small, we wouldn't be able to see much beyond our point of view.

        What I'm trying to say is that photons move in the three orthonormal dimensions, and change coordinates with respect to the fourth dimension. Duh. Everyone knows that. But what if there were some other particles (Higgs boson, perhaps?) that function similarly, only on these "curled-up" dimensions? The reference to the website was made simply to introduce the reader to a circular/spherical coordinate system. My comments following the link asked the reader to reduce the radius of said coordinate system.
    • This sounds like it is something different from the debate on whether the universe is open, closed, or balanced. IIRC, that debate has to do with whether parallel lines tend to converge, diverge, or remain the same "distance" apart over the distance of the galaxy. There is a good argument that the universe is exactly balanced, because if it is closed or open the equations lead quickly to massive expansion or sudden collapse. Or am I wrong? :)

      • "if it is closed or open the equations lead quickly to massive expansion or sudden collapse."

        On the universal time scale, what is 'sudden'

        Last I heard, and I haven't payed attention in about 2 years, evidence was suggesting that Hubble's constant was getting larger over time ... the universe is expanding faster and faster
        • I'm no expert, but my best guess for "sudden" is the Planck time (derived from G, Planck's constant, and the speed of light) which is 5 x 10^-44 seconds.

          The only other possibility I could imagine is the size of the universe divided by the speed of light, which is something like the age of the universe. That of course, would have been sudden when the universe was celebrating it's Planck's time birthday, but pretty darn sluggish today.
  • Let's assume for a moment that the observatory really IS able to discern the energy released as the minature black holes--wouldn't that energy be largely comprised of particles from our own spacetime dimension? My assumption is that the energy released would be the collision of the singularity with the surrounding particles, so in effect all we would be able to track would be "common" energy, not the extradimensional black hole which would have collapsed into nothingness.

    Maybe I'm missing something...
    • Very tiny black holes evaporate very quickly due to Hawking radition. The radiation is actually the black hole itself exploding.
    • It's not that the energy would be from particles from higher dimensions, but rather that without the extra dimensions the cosmic rays would have insufficent energy to form the black holes in the first place. This is made pretty clear by even a cursory reading of the article, but that seems to doesn't seem to be the norm around here.

      Now, a slightly more interesting question is why the extra dimensions would lower the threshold of singularity formation. Do they make space more compressible by giving it more room to flex in or what?

  • Could help in validating string theory? (Score:1, Insightful)

    by Anonymous Coward
    If I remember correctly, the idea that our universe contains extra tiny dimenions is a key component of string theory. If these hidden dimensions can be proven to exist, then this could lend string theory a lot of credibility.
  • Of course there are extra, invisible dimensions! Where else do you think all those socks go when you wash them in the laundry?
    • Of course there are extra, invisible dimensions! Where else do you think all those socks go when you wash them in the laundry?

      It has something to do with static electricity. It is interesting to note that while man has found a way to artificially create this phenomenon with a major appliance, dogs are able to do it on their own. Dave Barry wrote a great article [geocities.com] about this a few years ago. To quote:

      Darrell's theory is that ''the dirt is being pawed into the ozone layer,'' or that ''enough dirt is being tossed into the sky that another planet will be formed somewhere between Earth and Mars.'' Thanks to the Hubble astronomers, we now know that this is not the case; a more logical explanation is that dogs have somehow figured out how to paw the dirt into (speaking of Newt Gingrich) a completely different dimension.

  • Experimental proof for string theory (Score:5, Informative)

    by bravehamster ( 44836 ) on Monday January 14, 2002 @08:10PM (#2839145) Homepage Journal

    This would be a nice feather in the cap of string theory, which to this point does not have any experimental observations to back it up.

    One of the predictions (or you could say requirements) of string theory, is that the universe contains a total of 11 space-time dimensions, 7 of which are "curled-up" and are extremely tiny. Every time you move, you pass through the entire universe in each of these 7 dimensions, although your position in the 3 "enlarged" dimensions hardly changes. The interesting thing is that a guy predicted these extra dimensions way back in the 1910's, and was ignored for about 50 years. Experimental evidence on the side of string theory (or as they're calling it now, M-theory) would go a long way towards convincing the experimental physicists that all these theoretical physicists aren't off their rockers.

    • Actually, String theory has moved to M-theory, and involves "super strings" and membranes. I've read many books on the subject... most of them have taken a long time to read, i.e. read a few pages, think about it for a few days, go back...

      Anyhow, some links:

      My take is that, as has been said before, the world consists of 11 dimensions. There are actually many super-string/m-theories, but they are not contradictory, kinda like different views of the same thing.

      A main problem with these theories is that there are many (infinite?) solutions the math sets that descibe them.

      A 'string' in the theory is like a circular guitar string that is taunt... it has certain modes of vibration, each mode representing a certain type of particle.

      Also, there are different types of strings... strings that are self connecting, open string, string that loop around more than once...

      Ok, that probably didn't clear anything up...

    • Or, we could just build a superconducting particle accelerator as large as the solar system. Then we could probe distances as small as the Planck length (the approximate size of most strings).

      Then again, with the SSC canceled, maybe not . . .

    • Re:Experimental proof for string theory (Score:1, Insightful)

      by Anonymous Coward
      Extra dimensions weren't predicted back in the 1910's. They were postulated back in the 1920's, by Kaluza and refined by Klein. Kaluza-Klein theory was not ignored; IIRC, Einstein helped Kaluza get a faculty position on the basis of this work. K-K theory had problems though (e.g., the existence of the extra unobserved dilaton field). It got resurrected in the context of grand unified theories, until Witten killed it by showing you couldn't get the Standard Model out of it. (Then he shot down his own proof when working on M-theory, by introducing compactification onto a line segment rather than a closed manifold.)
    • Detection of signatures of large extra dimensions wouldn't actually offer direct experimental evidence for string theory. Yes, string theory predicts extra dimensions, but it isn't necessarily the only theory that does.

      Direct evidence for string theory at any point in the near future is highly doubtful. We just can't get good evidence of such high energy scales. We could see associated effects, like extra dimensions or supersymmetry, but those don't necessarily imply string theory.
  • I've been trying to wrap my mind around the basic ideas of quantum physics with the help of one of those popularizing books, but they have not talked about black hole evaporation. Is this like alpha radiation, where the probability curve of the location of a couple of protons is such that there is a reasonable chance that it will find itself outside of the range of the strong nuclear force? (but in the case of the black hole the force would be gravity and the location would be the event horizon or at least the point where the electrical force pushing on an ion would be stronger than gravity.)
    • It's called Hawking radiation, it occurs when spontaneous pair generation occurs right next to the event horizon and one of the particles falls in while the other escapes.
    • My ( basic ) understanding is that this is a quantum mechanical process. Right outside the
      event horizon you get particle-antiparticle
      creation. If memory serves the antiparticle is absorbed by the black hole ( reducing it's mass)
      and the particle is emitted.


      http://wwwusr.obspm.fr/admin/seminaire/chalonge/ bl ack-hole.html

    • Yes. The process by which blackholes evaporate is called Hawking Radiation. One interpretation of the evaporation is that particles tunnel out of the gravity well by a quantum process exactly analogous to that attributed to spontaneous radioactive decay. Of course gravity isn't limited to a short distance, which decreases the probability of quantum tunnelling.

      An alternative interpretation (and the more popular one), is that virtual particles of positive and negative mass enegries are created near the event horizon, and the negative mass energy particles fall into the black hole, while the positive mass particles escape. Ordinarily such virtual particles are created all the time and quickly annhilate each other back out of existence, but in the rare case that one crosses the event horizon they can't come back together and thus one becomes a real particle. Since we assume that negative mass energies can never be truly realized, only positive particles will ever escape.

      In both cases the blackhole loses mass and appears to emit particles. In fact, there is nothing about Hawking radiation that makes either interpretation more valid than the other.

  • New Observatory (Score:4, Funny)

    by Y B MCSE ( 469234 ) on Monday January 14, 2002 @08:19PM (#2839191) Homepage

    Cosmetic rays will indeed prove that the univers is shallow and one dimensional.

  • A bit more on the multiple universe theory... (Score:4, Informative)

    by instinctdesign ( 534196 ) on Monday January 14, 2002 @08:21PM (#2839204) Homepage
    Coincidentally I was just reading an article from a Discover magazine about the possibility of multiple universes. Thankfully you can also get the very same article online from Discover's website. Here is a snippet:
    We also have every possible option we've ever encountered acted out somewhere in some universe by at least one of our other selves. Unlike the traveler facing a fork in the road in Robert Frost's poem "The Road Not Taken," who is "sorry that I could not travel both / And be one traveler," we take all the roads in our lives. This has some unsettling consequences and could explain why Deutsch is reluctant to venture from his house.
    Also, at the end of the article, it provides a few good links for those interested in reading more about Young's double slit experiment. For the sake of being thorough (and those who don't want to read the article) the urls are www.colorado.edu/physics/2000/schroedinger [colorado.edu] and zebu.uoregon.edu/~js/21st_century_science/lectures /lec12.html [uoregon.edu].
    • These are actually completely different theories. What you call "multiple universes" sounds a lot like the Everett "many worlds" interpretation of quantum mechanics, i.e. that we can think of "wave function collapse" as a branching of the universe into different possibilities. Most people tend to think of this more as a way of looking at QM rather than an actual claim that other "universes" exist, and it certainly doesn't suggest any way of making contact with these other "universes."

      The idea of extra dimensions, on the other hand, simply implies that there are more spatial dimensions in the universe than it appears. Of course, there seem to be 3, plus one time dimension, but it's possible there are others that are visible on in small-scale (high-energy) effects. This has nothing to do with other universes.
    • Are you talking about that the article with the "11 Unanswerable Questions"? That was indeed, at least to me, a phenomenal read. It's based on 11 questions that premier scientists came up with at a recent NASA convention for physicists and astronomers. The article is interesting not only for its mad-crazy science (that's a technical term), but also the convergence of astronomy (ultra-macroscopic) and particle physics (ultra-microscopic) and how they need each other to explain these questions.

      Sadly, it is not up on Discover.com's website yet so I can not provide a link. It is in the latest (February 2002) issue and I highly reccomend it--it definitely re-piqued *my* interest in astrophysics...
    • These are actually completely different theories. What you call "multiple universes" sounds a lot like the Everett "many worlds" interpretation of quantum mechanics, i.e. that we can think of "wave function collapse" as a branching of the universe into different possibilities. Most people tend to think of this more as a way of looking at QM rather than an actual claim that other "universes" exist, and it certainly doesn't suggest any way of making contact with these other "universes."

      Interesting, sorry about the error... I read a lot of science articles but on a very broad range of topics so I get things confused now and then. Too bad you can't edit posts... shucks.

      Also, I actually have the newest Discover sitting about four feet from where I'm sitting but I have not yet had the chance to read the cover article. (I like to save the most interesting looking for last.) However the article on the new type of holography is absolutely not to be missed either, nor is the article on savants. Got a bit off-topic there... like I said, I have a varied taste. :-) Thanks again for the correction.

  • Random thought: no dimensions, no space (Score:3, Interesting)

    by Nindalf ( 526257 ) on Monday January 14, 2002 @08:23PM (#2839211)
    If we're going to go to such extreme wierdness as space having dozens of dimensions, why not just give up on the concept of position as fundamental quality of a particle? Between relativity and quantum mechanics, we've already lost absolute motion, flat space, and simultaneous exact position and momentum. What still makes so much sense about the concept of space?

    Why not go for a dimensionless graph universe of immutable particles/nodes representing conserved quantities? In addition to mass particles, have energy particles, charge particles, etc. (these are bad examples, of course; given the mass-energy equivalence, a "particle" of kinetic energy would have to be a compound entity). Just set up the rules to define the various types of connections, which have variable quantities (or possibly, are made and broken; however it works out to be simpler) and for determining the probabilities with which they may change from one arrangement to another. To put it in programming terms, take the data out of the particles, and put it into the relationships between them.

    It wouldn't be easy, it might be useless, but I know it would at least give me fewer headaches to start with a clean slate than to twist the classical ideas of space all out of shape.

    You can certainly have a graph system that behaves identically to a spacial system (though a graph system of Newton's physics would certainly be uglier than his elegant concepts), and it would lead to fighting fewer spacial preconceptions that give people such a miserable time keeping up with modern physics.

    Anyway, just a random thought.
    • Relativity and quantum mechanics dump the "classical ides" of space. The problem is that we are thought all our lives to think in those classical bounds. If you look at it from a purely physical, or even purely mathematical point of view, there is nothing classix about the description of space being made. You can't graph the spatial system in any clear way since its more than 3 dimensional...
    • Hmm... I think everything is energy. The difference between energy & matter is just perception on our part.

      Matter is just a very tight bundle of energy.

      Matter is also just the property of having momentum and being subject to gravity. It's just a 'mode' of being...

      Hmm... personally, I think it is really interesting to consider how our modes of observation effect our possible theories. What if we were being that 'saw' in terms of microwaves? How would our theories be different? I suppose it would all ultimately lead to the same place.
    • Actually, there are some people working on combinatorial quantum gravity models, though I don't know enough about them to be very informative. Look up "spin networks" or "spin foams."
    • Position isn't a fundemental quantity. Physicists have known this for a long time. Unfortunately we don't have any idea how to do math or geometry, let alone physics without a concept of absolute positions.

      Quantum mechanics is one way to fudge the matter by saying that we know how the particle is distributed over space, assuming space really had geometric (point-like) positions. String Theory takes this farther by building a structure for the universe where no objects are ever point-like. We believe that this can work because non-point-like objects can be described by the volume of space they take up, but it's probably not the best way.

      Many of us in physics would love a system to represent the world that physics actually takes place in, but we just don't know how to do that so we continue to work in increasingly awkward point based geometries and try to figure out what physics looks like when we impose our artificial framework on top of it.

  • Argentina -- a bad idea. (Score:3, Interesting)

    by juju2112 ( 215107 ) on Monday January 14, 2002 @08:30PM (#2839237)
    I don't think Argentina is really the best location for a scientific observatory -- they're currently in the process of overthrowing their government. There is rioting in the streets, mass looting, etc, etc. If I was in charge I would want it to be in a country that was much more stable.

    • Not really (Score:3, Informative)

      by barawn ( 25691 )
      The media and the rest of the world is convinced that Argentina is synonomous with Buenos Aires. That, and they're perfectly happy to sensationalize everything as well.

      The observatory is actually in a place along the Chilean border called Malargue (you'll never find it on a map - ever) which (according to all my friends there) is a little bit worried about the goings on in BA, but life, for the most part, seems normal.

      Seriously, the government overhaul is the least of the Observatory's problems - the biggest problems we have are getting things in and out of the country. International customs is horrible. Ever try to explain to someone what a photomultiplier is? Or how something that looks like a very big light bulb is worth $1000?
      • Waving my arms and shouting "Turista! American!" was enough to get an Argentinian Customs supervisor to pull me and my luggage off the Secondary Inspection line at EZE and throw me out onto the street. It's really not a bad country -- the Recoleta section of Bs.As. reminds one of Greenwich Village or SF, complete with street vendors and mimes, except nicer -- and the place will probably be dirt cheap once the Argentinian peso floats 40-50% down in value as is predicted.
        • "Norteamericano" is the correct way of doing it - they're american down there too - South American. But, I digress...

          Ezeiza's inspection really has never been anything at all to me - they don't even LOOK at anything non-Argentines bring in, because they don't care - all they're checking for is an excess of the import duty-free limit (which, I've been told, can easily be avoided, like all taxes in Argentina - which is one of their problems). No one has ever even spoken to me in that line - it's just hand over import form, smile, nod, and walk.

          The Recoleta didn't really impress me. I was also extremely disturbed by the number of cats in that graveyard. That's just plain weird. The area was nice, but seemed a little too touristy. Just my opinion though. I love Malargue, though (where the project actually is - in the Mendoza province). It's like a jump back 50 years in time, and the people are all incredibly friendly. The only problem I have is that the geography is so incredibly boring, as Argentina, save for the Andes, is simply ridiculously flat.
  • It has been suggested more than once in the litterature that cosmic rays might actually be linked with the mass repartitionin the universe. Superclusters are aranged in a sponge like maner. Astronomers have and still do wonder how this came to be, since it means either the universe was asymetric in the beginning or somehow became asymetric. Quantum non-locality gives a pretty satisfying answer : As a particle passes in "empty" space, it accelerates. how? well empty space isn't exactly empty, rather it's a swarming soup of particle anti-particle pairs being created and destroyed. The theory goes to say that the particle, over a long period of time, gets accelerated by the absorbtion of these half-photons being created and destroyed. The particles accelerate until they are slowed down by a gravitational field and thus matter conglomerates and empty space gets emptier. Those particles arrive at extremely high speeds and are thought to be the cause for cosmic rays.

    • Re:Possible source of cosmic rays (Score:4, Interesting)

      by barawn ( 25691 ) on Monday January 14, 2002 @10:13PM (#2839666) Homepage
      Unfortunately, this argument isn't very likely. The main problem we have is how to accelerate particles to such high energies - 10^20 and above is impossible by any stretch of the imagination, but the 3 x 10^20 particle that slammed into Dugway, Utah appeared to have a slightly better imagination than humans.

      Empty-space acceleration would have to be massive to counteract the utterly huge deceleration caused by energy loss in galactic/extragalactic magnetic fields, interaction with the interstellar medium, and, most importantly for extreme high energy cosmic rays (UHECRs), the GZK effect - photopion production by interaction with the cosmic microwave background radiation. It's simply not possible to accelerate particles like this in empty space - we would've seen it already in particle accelerators.

      Seriously, physicists right now have no idea how these particles are accelerated. Supernovae? Not nearly enough energy, by any stretch of the imagination - fundamental arguments like conservation of energy kill you far below the 10^20 eV limit. Gamma-ray bursts? Maybe, but the distribution of cosmic-rays doesn't agree with GRBs as a possible source. Extragalactic? Not unless you throw away basic physics and ignore the GZK effect - there's no way they could propagate that far.

      Basically, the one question that there have been tons upon tons of papers in the recent literature for is "where is this gigantic particle accelerator nearby us?"
      • Basically, the one question that there have been tons upon tons of papers in the recent literature for is "where is this gigantic particle accelerator nearby us?"


        I dont know where it is, but its probably run by some mice.

  • And furthermore.... (Score:4, Funny)

    by Y-Crate ( 540566 ) on Monday January 14, 2002 @08:53PM (#2839329)
    ".....Argentine officals hope to discover new black holes, dimensions and other phenomena, and find new ways to send their debt there."
  • Allright, so when will I be able to go to wal-mart and pick up my sliders brand dimension hopper? Just imagine the possibilities of disposing a body...
  • This is a first... I mean, we get the goatse.cx references on the NORMAL boards, but this is one on black holes! I say this at the risk of losing my precious karma.
    (Humor. Not troll.)
  • The article was okay in describing the result of these high-energy collisions and the means of detecting them, but what I want to know is why, if there are additional dimensions in addition to the four familiar ones, this should decrease the energy necessary to generate these miniature black holes? Could somebody more familiar with the appropriate theories fill me in on why this should be so?

    • Re:Why should this happen? (Score:1, Informative)

      by Anonymous Coward
      This article [aip.org] discusses your question in the "Long before the Planck scale" section; the idea is that the size of the extra dimensions brings down the "effective" 4D Planck scale from the usual 10^19 GeV to about a TeV.
    • The essential reason is that the "fundamental Planck scale" is ~ 1 TeV in LED (large extra dimension) theories. Gravity is a "bulk" field (propagates in all dimensions) while the standard model fields are localized, so this affects them differently. The gist of it is, if you put enough energy in a small enough region, you make a black hole. If there are more dimensions, the size of that region is bigger, so it's not as difficult to make black holes.

      Let me try to outline what's going on: I'm getting this from "Black hole production in TeV-scale gravity, and the future of high energy physics" by Steven Giddings (hep-ph/0110127 on arxiv.org). It's a nice article to start with, if you want to dig into the literature on this.

      (By the way, this is using the "warped" extra dimension model but the general ones are similar.)

      The Planck mass in D dimensions is M_p^(D-2) = (2 pi)^(D-4) / (4pi G_D) with G_D the gravitation constant. It turns out (M_4 / M_p)^2 = (M_p)^(D-4)V_{w}, with V_{w} the "warped volume" of the extra dimensions. (I'm not being very rigorous here; in fact this is how the volume is defined, and the ratio is given by a certain integral in terms of the warped metric.) This is essentially a sort of "Gauss law" argument, over the extra dimensions.

      Now, let's consider a black hole with radius r_h much less than the geometrical scale R_c of the extra dimensions. It turns out that for a black hole of mass M, spin J, in the J = 0 limit, we have r_h = 2 [C M / M_p^(D-2) ]^[1 / (D-3)] where C is some constant in terms of D that I don't want to bother writing. The Hawking temperature looks like T_h = (D-3)/(4pi r_h). This description is valid roughly for M_p > 1.1 TeV - .8 TeV for D = 6 - 10.

      Black hole cross-section was assumed to be geometrical (pi (r_h)^2), but as I mentioned in another post this is questioned (look up papers by Voloshin - but Giddings questions those), and there may be an exponential suppression. Anyhow, the important point is that, once you take all this into account, you get that the cross section sigma grows when D is larger, i.e. you don't have to put energy into as small a region if there are more dimensions.

  • Bug (Score:5, Funny)

    by metis ( 181789 ) on Monday January 14, 2002 @09:26PM (#2839492) Homepage
    Rumor has it the the code for the sixth dimension has a dangerous bug. An attempt to observe a cosmic ray entering this dimension can cause an illegal cast from a neutrino to a photon.

    The problem is that

    "The result of casting elementary particles outside the inheritence hierarchy is undefined."

    The Manual 4.1, chapter 7 cited in Universe(3)

  • More info on the Observatory (Score:5, Interesting)

    by barawn ( 25691 ) on Monday January 14, 2002 @09:41PM (#2839559) Homepage
    Oh my God, I'm amazed - this is the observatory I actually WORK for, and it's on SLASHDOT, my God.

    Forgive me for going completely crazy replying to everyone, but this is just too cool.

    OK, so long as people promise not to Slashdot the server (heh, that was dumb) for anyone who wants more information, go to the main Auger website [auger.org], or for even cooler information, go to the Auger site in Argentina [auger.org.ar].

    Auger is actually a very interesting project, and it's not like anything you'd ever think of - it's a 1600 km^2 array of water Cerenkov detectors (10 cubic meters of water) spaced 1.5 km apart - the picture in the article is of the flourescence detector, which is more like what you think of for a standard detector, but due to the limitations of the flourescence method of detecting cosmic rays, its duty time is only 10%, as opposed to the 100% of the surface array.

    The project is proceeding along... pretty well. We've basically finished the Engineering Array, a small-scale testbed to find all of the design flaws in the initial project (and boy, did we find them) and we've detected some cosmic rays which we believe to be ~10^19 eV. We've also demonstrated the hybrid design as well (events where the flourescence detector triggers as well as the surface detector).

    The black hole stuff isn't the important goal of the project - the goal is to elucidate the spectrum of cosmic rays above 10^20 eV, because we have no idea where those particles come from - all of basic physics says they can't exist. This is one of the big questions in astrophysics in recent years, up there with gamma ray bursts and odd quantum states of matter.

    It's way cool. And not just because I work on it...
  • *bubble bubble bubble from the bong*

    Someone's been smoking a *little* too much Argentinian "coffe".
  • Here's a fun way to play with extra dimensions... This used to have some nice ASCII art for the first three but Lameness filter encountered. Post aborted!
    Reason: Please use fewer 'junk' characters.     Fucking lame-ass filter.

    1.) Visualize a line. It has one dimension.

    2.) Now add another dimension. Visualize a square. It has two dimensions.

    3.) Now add yet another dimension. Visualize a cube. It has three dimensions.

    4.) Now add another dimension. Visualize a hypercube. It has four spatial dimensions. Kinda fucks with your head doesn't it? Stuff like this is REAL bad to think about if you can't sleep, by the way.

    Tim!

  • What if one uncurls? (Score:2, Interesting)

    by LichP ( 549726 )
    This may sound like a silly question, but would it be theoretically possible for one of these potentially-existant curled up dimensions to uncurl?

    What the universe be like if we suddenly got some osrt of extra spacial dimension?

    Or going the other way, would there ever be any risk of one of our current spatial dimensions curling up?

  • Yes! (Score:2, Funny)

    by 3Suns ( 250606 )
    Very soon I will be able to travel between these alternate universes, and assassinate all my alternate selves. By doing this, I shall transfer all their energy to my own body. I will be the posessor of godlike speed, strength, and intelligence! It's not murder, I'm just collecting all the excess energy into one container.

    I shall be The One!
  • As soon as they find the black holes in our atmosphere, I can reclaim my lost pens, socks and lighters -- maybe even bring back Jimmy Hoffa.

  • cosmic rays trillion accelerators (Score:3, Informative)

    by peter303 ( 12292 ) on Tuesday January 15, 2002 @10:34AM (#2841794)
    The most energetic cosmic rays are 10^14 more
    energetic than the largest human accelerators.
    The tradeoff is "luminosity". You may only see a
    few of the highest energy cosmic rays in a year,
    while you want zillions of hgih energy particles
    in an accelerator.
  • Well, from what I know about black holes, as matter passes through the event horizon, the entropy increases. This increase in the black holes entropy translates into an increase in the size of the event horizon. So, as the mass increases, so does the event horizon. At the same time, the temperature of a black hole is inversly proportional to the mass. So the temperature decreases as the mass increases. On the flip side, if the mass is small, the event horizon is small, and the temperature is extremely high. Since we are talking about a extremely small black hole, we are talking about photons being radiated at an extremely high energy in a very short time. Now I understand that the uncertainty principle allows extreme fluctuations in changes in energy as long as it is "paid back" within a short amount of time. But it seems that this extreme "Heat" is being radiated off by extremely energetic photons. In my layman analysis, it would seem that such extreme energies in our atmosphere would be detectable by several means. In lieu of this, I can understand that if there are 10 spatial dimensions, energy is being radiated in all dimensions and therefore in the three spatial dimensions we experience, we would only see a fraction of the total energy radiatated. Now for my question. It would seem likely that the radiation radiates in proportion to the spacial dimensions. If these extra spacial dimensions are soooo small, then they would have only a small fraction of the total energy radiated. Therfore, wouldn't we STILL see a phenomenal amount of energy in our atmosphere from the Black Hole Evaporation???? (Sorry for the length).

Slashdot Top Deals

The Tao is like a glob pattern: used but never used up. It is like the extern void: filled with infinite possibilities.

Close