Slashdot Mirror

← Back to Stories (view on slashdot.org)

Giant Black Hole Found

Posted by chrisd on from the infinite-radius-finite-diameter dept.

paradox writes "Reuters is reporting that scientists have found a massive black hole 40,000 light-years away that could change the way scientists think about black holes. The mass of this particular black hole is 14 times the mass of the sun, compared to the typical mass of 3 to 7 suns."

176 of 283 comments (clear)

  1. Scientists should really... by tcd004 · · Score: 3, Offtopic

    Scientists should really leave rosie o'donnell alone.

    tcd004

  2. Kill It! by bcilfone · · Score: 1

    Destroy it before it kills us all!

    --

    A choice of masters is not freedom
    1. Re:Kill It! by praxim · · Score: 1

      I prefer the Half-Life version, which is, I believe, "Destroy the damned thing before it grows any larger!"

  3. Why the puzzle? by Mt._Honkey · · Score: 1, Interesting

    Is it so odd that a stelar black hole formed, and maybe driften near a cluster of stars or a big ass nebula in its lifetime? Maybe it's ancient.

    --

    Don't Bogart the fish sticks
  4. Re:Potential energy source? by Anonymous Coward · · Score: 5, Funny

    Tell you what. You fly out there and do a complete survey of the area. We'll wait for you to come back with your findings and whatever you decide is the best course we'll implement. This is in your hands now.

    Thanks for volunteering.

    BTW, don't fall in! hahaha... Astronomy joke... *sigh*

  5. Size IS important. by ho11yw00d · · Score: 1

    But what about its physical size? I mean, when you are dealing with monstrous astro-physical phenoms beyond human comprehension, isn't it important to be boggled by the density?

    --
    That's not my hand.
    1. Re:Size IS important. by zCyl · · Score: 5, Informative

      But what about its physical size? I mean, when you are dealing with monstrous astro-physical phenoms beyond human comprehension, isn't it important to be boggled by the density?

      Because there IS no size. A black hole by definition is a singularity, and has no conceivable dimensions. The closest thing a black hole has to a size is what's called the Schwarzschild radius, or the event horizon. This radius is the distance from the center at which light can no longer escape (ignoring Hawking radiation, another topic entirely). The Schwarzschild radius is equal to 2GM/c^2, where G is the gravitational constant, c is the speed of light, and M is the mass of the black hole. So the radius is really nothing more than a constant times the mass.

      If you know the mass, and you don't have rotation, you know everything that can be known about it.

    2. Re:Size IS important. by rabidcow · · Score: 1

      If it's a black hole, its density is infinite. Its physical size is zero, unless you mean the size to its event horizon, but the actual mass is all at the center.

    3. Re:Size IS important. by egomaniac · · Score: 2

      A black hole is a singularity. It has no size, and therefore its density is infinite.

      The sphere defined by its event horizon does have a size, but it will be very small (a few tens of miles across, perhaps). Maybe an astrophysicist in the audience will compute the size for us?

      --
      ZFS: because love is never having to say fsck
    4. Re:Size IS important. by cascino · · Score: 5, Informative

      Technically the singularity itself possesses infinte density, and thus it's size cannot be resolved (i.e.: it's a single point, no matter how close you magnify it).
      The Schwarzschild radius of such an object, however (better known as the "event horizon"), can be calculated fairly simply using a variation of the escape velocity formula
      Rs = 2*G*M / c^2
      Where G is the gravitational constant, M is the mass of the object, and c is the speed of light.
      Plugging the numbers into the equation yields a radius of 2.95 * 10^6 km. Therefore this black hole has a radius just over four times the size of the sun, and an area 16 times as large. Compared to black holes usually on scales relative to that of the Earth, that's REAL big.

    5. Re:Size IS important. by sokoban · · Score: 1

      Let's see. I found the radius of the event horizon to be about 41.8 Km. That's pretty darn huge. The formula I used was 2GM/c^2. Based on the data that the mass is about 14 Solar masses, M is roughly equal to 2.8e31.

      --
      09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0 is the magic number.
    6. Re:Size IS important. by Unknown+Poltroon · · Score: 1

      I beleive you can know the charge also, positve or negative.

      --
      All Troll + "offtopic" mods are meta moderated as "Unfair", because you abused the system.
    7. Re:Size IS important. by the_2nd_coming · · Score: 5, Informative

      no a sigularity is the center of a black hole, it is where space time becomes undefind. a black hole is the defined by the eventhorizon. so it does have a size. if it is just a sigularity it is not a black hole, it is a naked sigularity.

      --



      I am the Alpha and the Omega-3
    8. Re:Size IS important. by anethema · · Score: 2, Interesting

      I'm confused. I was under the impression that a black hole was a star that had collapsed and the space between the electrons and the nucleus (sp?) was reduced to zero. We're always told if the earth turned into a black hole, (yes i know it cant) it would be the size of a basketball. Can someone please clarify? Im giving up the right to moderate on this story by posting this, so someone better reply :) ...

      --


      It's easier to fight for one's principles than to live up to them.
    9. Re:Size IS important. by Anonymous Coward · · Score: 1, Informative
      When an object collapses to a black hole, all the matter crunches down to a singularity of zero size. But the singularity is not the black hole. The black hole is a region of space outside (and including) the singularity, from which light cannot escape. That region has a finite size.


      P.S. If the Earth turned into a black hole, it would be about a centimeter across.

    10. Re:Size IS important. by Anonymous Coward · · Score: 1, Informative

      In other words, the matter that was formally the Earth woould not take up any space at all (it would crush down to zero size) but its horizon (the area of space that it caused all light/matter/etc to be pulled in) would be about the diameter of a basketball. Or a marble. Depending on whom you ask.

      A nice little presentation on black holes can be found here.

      http://archive.ncsa.uiuc.edu/Cyberia/NumRel/Blac kH oleFormation.html if you are paranoid.

    11. Re:Size IS important. by Anonymous Coward · · Score: 2, Informative

      Actually, speaking as someone studying in the field of quantum gravity, the question of whether singularities exist is still very much up in the air, though many people hope that Planckian physics will remove them. There are even some tentative results in that direction. On the other hand, it has been suggested that quantum gravity must contain at least "mild" singularities. So it is rather premature to claim that "most scientists" (or even most quantum gravity theorists) have abandoned the idea of a singularity.

    12. Re:Size IS important. by HorsePunchKid · · Score: 1

      I was under the impression that you could also determine the magnitude of the charge, but I'm not sure. I imagine it might be very difficult to determine the charge if the accretion disk radiaties so much. But a black hole certainly has a magnetic field. This Astronomy Picture of the Day had some interesting links about magnetism in an astronomical context.

      --
      Steven N. Severinghaus
    13. Re:Size IS important. by Suidae · · Score: 1

      um, I think the Schwarzschild radius of the mass of the earth is said to be closer to the size of a pea.

    14. Re:Size IS important. by Suidae · · Score: 1

      How do you determine the angular velocity of a black hole? Frame dragging maybe?

    15. Re:Size IS important. by MetricT · · Score: 1

      Actually the formula for the radius of a black hole is:

      R = 3km * (Mass in solar units)

      So a black hole with 14 solar masses would have a radius of 42 km.

    16. Re:Size IS important. by sigwinch · · Score: 5, Informative
      A black hole is a singularity.
      It's important to remember that a singularity is a mathematical artifact where a physical property has no meaningful definition when measured by a particular metric. For instance, the north pole of the Earth is a longitude singularity, a point where the very concept of longitude ceases to have physical meaning.
      It has no size, and therefore its density is infinite.
      Actually, that turns out not to be the case, at least not relative to our reference frame. Imagine you're a distant (and indestructible!) observer watching a star collapse into a black hole. The more it collapses, the more it is affected by gravitational time dilation: time appears to run slower for the matter in the star than for the observer. Clocks in the star slow down. Light travelling away from the star is shifted towards the red end of the spectrum.

      The more the star shrinks, the more it is affected by gravitational time dilation, and thus the more slowly it collapses as measured by the outside observer. The collapse thus asymptotically approaches infinite time dilation, and appears to freeze in time to the distant observer. Its physical size at the asymptote is the size of the event horizon, a.k.a. the Schwarzchild radius.

      One way of measuring the star is to ask how long it would take light to travel from its outside edge to its center, as measured by a distant observer. (Theoretically, of course, as the star would absorb any light.) Think of it as the radius measured in units of literal light years. As the collapse approaches infinite time dilation, the 'light radius' approaches infinity. This is the singularity at the center of the black hole, and is a mathematical construct arising from the distant observer's point of view. It does not mean that density or any local physical parameter is infinite

      I'm deliberately ignoring what the collapse looks like to an observer inside the star. Known physics simply cannot make any meaningful predictions, except that it will never be observable from the outside (because it literally takes an eternity to occur).

      --

      --
      Kuro5hin.org: where the good times never end. ;-)

    17. Re:Size IS important. by BLAMM! · · Score: 2, Funny
      What, African or European?

      Sorry. Couldn't resist. :)

    18. Re:Size IS important. by Anonymous Coward · · Score: 1, Informative

      It's important to remember that a singularity is a mathematical artifact where a physical property has no meaningful definition when measured by a particular metric . For instance, the north pole of the Earth is a longitude singularity, a point where the very concept of longitude ceases to have physical meaning.


      You are confusing coordinate singularities (such as the longitude singularity you describe, or the event horizon singularity in Schwarzschild coordinates) with a true curvature singularity (such as at the center of a black hole). The former is a mathematical artifact of your choice of coordinate system in describing the metric; the latter is physical.


      It has no size, and therefore its density is infinite.


      Actually, that turns out not to be the case, at least not relative to our reference frame.



      An external observer can't assign a size, zero or nonzero, to something within the horizon. It's true that an external observer will measure the size of the collapsing object to asymptotically approach the Schwarzschild radius, but that has nothing to do with the size of the singularity itself.


      This is the singularity at the center of the black hole, and is a mathematical construct arising from the distant observer's point of view. It does not mean that density or any local physical parameter is infinite


      Not true. The presence of the singularity is local and has nothing to do with any external observer's perception. For instance, if you compute the curvature scalar (contraction of the Ricci tensor), which is a local physical observable, it will blow up at the singularity.
    19. Re:Size IS important. by the_2nd_coming · · Score: 2

      Physicly you would not have a black sphear, however, Light that is refracted around the eventhorizon would give the aperence of size. therefore a blackhole hs a diameter.

      --



      I am the Alpha and the Omega-3
    20. Re:Size IS important. by throbber · · Score: 1

      I'd hate to be a pedant, bat urely you should be talking in Volume rather than Area. After all, the area of a cross-section of both would be the same if you took it at the right spot.

    21. Re:Size IS important. by archen · · Score: 1

      Well see if this helps to clarify things. A black hole does not have size but it does have a mass. The mass can change, while the size technically does not. What we define as the black hole is typically what we can't see. A black hole has an event horizon around the singularity (the hole itself). The horizon defines that edge where nothing comes back (exempting hawking radiation). The more massive a black hole is the larger the radius of the event horizon is - so a black hole can sort of be bigger when you consider where the event horizion is, but at the same time static in size (the singularity itself).

    22. Re:Size IS important. by Fortmain · · Score: 1

      Indeed, check out Stephen Hawking's 'Law of Cosmic Censorship': The Universe does not allow "naked singularities"; they will always be clothed in a black hole.

      --

      We gotta make democracy safe for the world! -- Pogo
    23. Re:Size IS important. by SimCash · · Score: 1

      Not quite, do not forget electrical charge. In fact, electrical charge is how you set up to vibrate a black hole so you can create gravity waves as a carrier signal. Do not know why you want to use gravity as a carrier signal, but that is how you do so.

  6. oh, NO! by A_Non_Moose · · Score: 3, Funny

    First a hole in wu-ftpd and now they are in space!

    Hey, that is it, a black hole is a security exploit in space.

    Maximillian!!!!

    --
    Have you read the moderator guidelines? Well, have you, PUNK? (and I want a Karma: Gnarly option)
    1. Re:oh, NO! by joel8x · · Score: 1

      How the hell does rjamestalylor who posted virtually the same exact post one minute later than you get a score of 2 Funny ,when you only got a 1 Off Topic???????(I guess you should have linked to a slashdot article instead of just mentioning it!!)

      I hate favoritism

      --
      Sound waves should be free!
    2. Re:oh, NO! by rjamestaylor · · Score: 1
      Because my post was actually clever!


      (kidding! just kidding!)

      --
      -- @rjamestaylor on Ello
  7. Repeated story by rjamestaylor · · Score: 3, Funny
    Michael just posted a story about the discovery of a giant hole....

    (it's funny. laugh.)

    --
    -- @rjamestaylor on Ello
  8. Re:Potential energy source? by Doppler00 · · Score: 1

    That doesn't make any sense. We can't actually create our own black holes (thankfully!) and the ones we know about are too far away to be any use. The only time I can think of when the gravitation of a planet is used for energy is when the gravitational pull of a planet is used to increase the velocity of a space prob.

  9. Re:That's nice by rebug · · Score: 1

    they were kinda asking for that, but the other black hole is cooler. I wouldn't want to sit and throw things into mr. goatse man's black hole, and I don't think Hawking is doing much research in that particular area.

    --

    there's more than one way to do me.
  10. Another hole found? by Anonymous Coward · · Score: 3, Offtopic

    Specialists concur that this is hole is even bigger than the previous hole found (and also reported on /., one story back).

    Although CERN tried to keep this hole silent until every God had a patch available to stuff the hole, it didn't work out that way.

  11. Re:Potential energy source? by Robert1 · · Score: 2, Interesting

    Uh, how would you make the energy? You could send something shooting into it, thus it gaining some kinetic energy, but aside from the slingshot effect it wouldn't have much practical purpose. Anything you shoot at it (if your making power) would probably need to be resent, in which case you'd have to draw it back out. Net energy gained = 0.

    Only thing I can think of is using it as a giant waste dump. Launch our trash into it and let it approach the center of the blackhole for all eternity.(Gotta love time dilation)

  12. It will change the way scientists think about them by glwtta · · Score: 4, Funny

    "We now think they are bigger!"

    --
    sic transit gloria mundi
  13. Re:Potential energy source? by Fnkmaster · · Score: 2

    Umm, how exactly would you extract that? Perhaps tidal forces can be utilized to extract power (tidal forces near the event horizon of a black hole are large, though surprisingly they are larger for a small black hole). But you can't just magically extract gravitational energy from a massive object with an r^2 gravitational field. Perhaps it's possible, but the gravity of even this massive black hole is only 14 times stronger than the Sun - so we could do whatever it is with the Sun first. I've never heard anybody propose extracting gravitational energy from the Sun, so I presume there is no easy way to do this. Accelerating particles falling inward hit an orbiting station which converts this accelerated stream into energy which it retransmits as electromagnetic waves outwards, perhaps? Sounds sort of like an artificial accretion disk - which is an interesting idea, come to think of it. Have no idea if this is at all self-consistent (much less practical).

  14. Re:Imponderable physics question by rebug · · Score: 1

    What i want to know is how the hell your theoretical planet would end up living near enough to a black hole to orbit it. Plantets aren't just hanging around looking for something to orbit around, you know.

    It's a scale issue. Planets don't orbit around black holes, galaxies do.

    --

    there's more than one way to do me.
  15. Distance by gandalf_grey · · Score: 5, Insightful
    It's worth noting that the center of the galaxy is 26,000 lightyears from us, see: space.com. So 40,000 LY is not exactly nearby, as the story seems to imply.

    So, don't worry about being sucked into infinitely long strings of goo just yet.

    --
    Mmmmmmm. Floor pie!
  16. I've always had doubts... by fireboy1919 · · Score: 3, Insightful

    ...about extrapolated data.

    How do we find stars and planets? We make assumptions about stellar phenomena and then predict other phenomena using those assumptions as long as they seem to work.

    We do the same thing with everything we use. We've done the same thing with other stuff, but most of the time, we can observe a lot more dimensions of the data than we can with stellar phenomenon to make our predictions.

    So I suggest that there are any number of reasons that could indicate why this answer makes sense: the model for detecting mass may be wrong, or the model of the formation of black holse, or somethinig else that I haven't considered.

    At any rate, we have a long way to go to learn to understand stellar phenomena.

    --
    Mod me down and I will become more powerful than you can possibly imagine!
    1. Re:I've always had doubts... by LMCBoy · · Score: 4, Insightful

      "How do we find stars and planets? We make assumptions about stellar phenomena and then predict other phenomena using those assumptions as long as they seem to work."

      Huh? We find stars and planets by stepping outside at night and looking up. What exactly are the "stellar phenomena" that we have a long way to go before understanding?

      I suppose, since you're questioning the mass determination of the black hole, you must be saying that we don't yet understand Kepler's 3rd law of motion (that is the only theory needed for the measurement). Hmm...Kepler came up with that in 1609. In 400 years, his laws have been used to: construct the first accurate mathematical model of the solar system (still in use today), predict a planet beyond Uranus (Neptune was discovered exactly where Keplerian physics said it had to be), send humans to the moon, send probes to the outer planets and beyond, and determine masses of binary stars throughout our galaxy.

      In short, there's nothing in this particular measurement that requires *any* understanding of stellar physics. It's a simple application of 400-year old Newtonian gravity. If you want to question the result, I suggest looking at the systematic errors of the observations (e.g., is the inclination angle of the system known? if not, the black hole could be more massive than measured).

      Oh, and the process you describe (start with an assumption, make a prediction based on the assumption, test prediction by experiment/observation, refine assumption) is called the scientific method, not "extrapolating data".

      --
      Liberal (adj.): Free from bigotry; open to progress; tolerant of others.
  17. Re:Potential energy source? by jdrogers · · Score: 2, Insightful
    A massive black hole this close to Earth would probably be quite useful in developing high energy procedures, and also as a interstellar navigational tool, since it could be use to perform very effective "gravity whip" manoevres, such as are used by NASA deep space probes.

    Well, thats all well and good, but it would still take 40,000 years for light to get there, let alone a probe traveling much slower. I think we can safely say this won't get much use as a gravity sling-shot anytime soon.

    As far as an energy source, a black whole doesn't really offer much (that I know of) that any other mass out there would. I think we are better off trying to capture the energy of a much closer object, the sun. Hey, its green too, even if it is fusion. :-) The more exciting thing about this is that since it is relatively close, it will be easier to resolve with telescopes the miscellaneous things that go on around a black hole. We can learn a lot about how the universe works from watching how stuff falls into it and what things come shooting out from near the event horizon.

    JD

  18. Irresponsible by Puk · · Score: 5, Funny

    I think Reuters is being completely irresponsible by reporting this hole before a fix can be completed by all affected parties. The only current known fix for this hole is to make sure less matter falls in than energy is radiated by the hole, and keep it that way for a long time. In the meantime (however many millions and millions of years that takes), script kiddies with FTL drive capabilities will be having a field day.

    Slashdot is just contributing to the problem by spreading the news. Sheesh!

    -Puk

    p.s. This hole is hardly a surprise. We've found that space is riddled with such holes, and to my knowledge, none of them have been closed. If space was open source to begin with, enterprising hackers would have found these holes long ago, and plugged them with Bill Gates' ego.

    1. Re:Irresponsible by Sabalon · · Score: 4, Offtopic

      Universe Pack 2 has been out since June which fixes this hole. It is not our fault that the various gods running the universes can not be bothered to check for updates to their cosmos once in a while.

    2. Re:Irresponsible by shaunak · · Score: 1

      "If space was open source to begin with, enterprising hackers would have found these holes long ago, and plugged them with Bill Gates' ego."

      Well, if you plugged them with Billy boy's ego, would they radiate Hawking Monopoly Radiation(Tm)?

      --
      -Shaunak.
  19. Re:That's nice by rebug · · Score: 1

    Hawking radiation might smell. Here's how we find out.

    • build a very large catapult
    • fire yourself towards this black hole. try to achieve a velocity somewhere around 1.46e+07c. we can't wait all day for your answer, you know
    • as you approach the singularity, note any aromas. take notes. hurl the notes back toward earth at near infiinite velocity so they don't just get sucked in


    we'll be waiting

    --

    there's more than one way to do me.
  20. Hello! Light-years! by fm6 · · Score: 1, Redundant

    Uhm, you do know how far away "40,000 light years" is? Assuming you could even travel that far, and find a way to tap the energ, how would you send it back? If you used a laser beam, it would take 40,000 years to get here! I rather hope the energy crisis will be over by then!

    1. Re:Hello! Light-years! by fm6 · · Score: 2

      Rundundant? I was first! The others are redundant!

  21. Some info by bryan1945 · · Score: 1

    Ignoring all the obvious jokes that ACs are going to post...

    14xSun is no big deal. The hypothetical central black hole in each galaxy has been ranged from 100-100,000 xSun mass, 10k being a nice round figure.

    Also, considering that modern theory says that a sun needs to be anywhere from 10x to 100x our sun's mass, even considering the mass blown off during contraction, 7x sun mass is just a wrong number. 14x would be somewhere along the minimum mass to generate a black hole.

    Of course, if worldwide consensus has now switched in the last 12 hours, everything above I said is wrong. Cold fusion, anyone?

    --
    Vote monkeys into Congress. They are cheaper and more trustworthy.
    1. Re:Some info by JoeRobe · · Score: 4, Informative

      14x is a big deal. The 100-100000 solar mass black holes at the center of galaxies (which still isn't proven, but has a lot of data pointing towards it) are not stellar black holes. They would be called galactic black holes. Stellar black holes are byproducts of dead stars. The Chandra limit, 1.4 solar masses, is the minimum mass that is needed to make stellar remnants collapse. If it is over 2 or 3 solar masses, then it collapses all the way into a black hole. Now, that was figured out several decades ago, so of course that number might be slightly "off," but I seriously doubt that Chandra was off by a factor of 10. I'm curious where you get 10-100 solar masses from...

      When a star with a mass of ~30 solar masses or higher dies, it supernovas, blowing off most of its mass. IF WHAT'S LEFT is greater than a couple of solar masses (and within the Schwarzschild radius), then it collapses into a black hole. I repeat: it MUST ONLY be more massive than a few (2 or 3 - it's under debate) solar masses! True, the original star must be greater than ~30 solar masses; but the mass of the black hole is far less than the mass of the original star. THIS is why a 14 solar mass black hole is so strange!

      By the way, NO information regarding black holes is the subject of "worldwide consensus".

      --
      The best way to predict the future is to invent it.
    2. Re:Some info by coyote-san · · Score: 2

      You're confusing two different masses. One is the mass of the star that collapses in a type-II supernova. There's a minimal size for such stars (just as there's a minimal size for a star to be a star, instead of a large Jovian body), and IIRC there's also a maximum mass due to various physical constraints.

      The other mass is what's crunched into the black hole. If I remember the numbers right, and they haven't been surplanted by more recent research, at "maximum" crunch some of the stellar mass is falling inward at a third of the speed of light, and the maximum density is something like 4 times that of a regular nucleus. This is a *very* hard surface, and anything outside of the maximum crunch will be blown outward. A lot of the matter in the crunch will be blown outward, as the "spring" releases. This is the same force (under Newton's second law) that pushes the matter within this shell inward past the final resisting force and into a black hole.

      All of this conspires to mean that only a fraction of the stellar mass will actually end up in the black hole. Far more will end up in the planetary nebula. But it all together and you get the usual figure of about 7 stellar masses as the maximum mass of a black hole created by a single star.

      --
      For every complex problem there is an answer that is clear, simple, and wrong. -- H L Mencken
    3. Re:Some info by bryan1945 · · Score: 1

      Reading the 2 main replies to my post, I did confuse a bunch of issues and situations into one event.

      Just wanted to point out that these guys/gals know some info which I paraphrased and/or glossed over, and that they have good point which I missed.

      --
      Vote monkeys into Congress. They are cheaper and more trustworthy.
  22. Re:Imponderable physics question by Anonymous Coward · · Score: 2, Informative

    The event horizon of a 14 solar mass black hole would be about 84 kilometers in diameter. A planet could certainly orbit a black hole, and the orbit would be no different than that about a non-black hole of the same mass. (Though to be picky, neutron stars can't be as massive as 14 solar masses.)

  23. non-watered down story by ChazeFroy · · Score: 5, Informative

    Here's a link to the European Southern Observatory story that's not watered down (gotta love Reuters and AP like that!).

  24. Supermassive black holes by ukryule · · Score: 4, Interesting

    Whatever happened to the theory of supermassive black holes? These black holes, at the centre of each galaxy are supposed to be millions of times heavier than the sun.

    So what's so great about a black hole only 14 times as heavy as the sun (which is also further away than the centre of our galaxy)?

    1. Re:Supermassive black holes by Lupus+Rufus · · Score: 2, Interesting

      I don't see what's so confusing about it. This black hole was part of a binary system, with a star progressively feeding a black hole. It is an example of a relatively small phenomenon. Supermassive black holes, on the other hand, represent the cores of galaxies, and are incomparable to these "small" black holes for any number of reasons. This 14-sol black hole is new because we never knew small black holes could be so large.

      --

      Aren't you dead?

    2. Re:Supermassive black holes by Doctor+Fishboy · · Score: 1

      The problem comes in formation. Binaries do not coalesce to form larger mass black holes (it's a problem of getting rid of the huge angular momentum storead as the stars orbit each other), except possibly as binary black holes which take many mega-years to spiral into each other via gravitational radiation loss. 14 solar masses is also larger than the sum of masses of most binary systems, and those systems which *do* have large masses don't merge for dynamical reasons (mostly the AM problem above).

      The interest is that there's no clear formation mechanism for these medium-sized black holes.

    3. Re:Supermassive black holes by supruzr · · Score: 1

      Actually, there's a perfectly satisfying and reasonable explanation of how a black hole of 14 solar masses can form, and then find it's way as the drainpipe of stellar matter in a binary system....

      And to receive that deeply fulfilling answer, all you need to do is BUY MY NEW BOOK entitled, "How to influence people, and con them into buying misleading books" and you can BUY IT NOW for a special one-time-only price of $99.98. BUT WAIT, THERE'S MORE! ACT NOW and receive a tesseract keychain*, ABSOLUTELY FREE.

      *Due to dimensional constraints, your tesseract may resemble a Little Piece of Useless Crap.

  25. Where the hell did those figures come from? by the_2nd_coming · · Score: 2

    black holes are not typicly 3 -7 suns in mass they are like 3-7 thousand suns in mass. a 14 sun mass black hole is very light.....I think it is spose to be 14000 suns......

    --



    I am the Alpha and the Omega-3
    1. Re:Where the hell did those figures come from? by Anonymous Coward · · Score: 1, Insightful

      Not true. Most black holes form from large stars, and so are only a few solar masses. Then there are the supermassive ones at the centers of galaxies, that are millions of solar masses. We don't really know of any in between those two ranges.

    2. Re:Where the hell did those figures come from? by the_2nd_coming · · Score: 2

      realy? thats counter intuitive.....perhaps the text I have read only dealt with super masive centers of galaxys and I did not read it......I will have to read a history of time and blackholes and supernovas(or what ever the second part is) again.

      --



      I am the Alpha and the Omega-3
    3. Re:Where the hell did those figures come from? by dadragon · · Score: 1

      Blach Holes and Baby Universes by Stephen Hawking.

      --
      God save our Queen, and Heaven bless The Maple Leaf Forever!
    4. Re:Where the hell did those figures come from? by aengblom · · Score: 2, Interesting

      And I quote:

      "Working out the star's mass and orbit, they inferred a surprising mass for the black hole. It weighs about 14 times as much as our Sun. That's nearly twice as much as any other in a similar binary system. (Black holes at the centres of galaxies can be thousands of times heavier still)."

      --


      So close and yet so far from the world's perfect ID number
    5. Re:Where the hell did those figures come from? by the_2nd_coming · · Score: 2

      no no the book I was refering to was Blackholes and Time warps

      --



      I am the Alpha and the Omega-3
    6. Re:Where the hell did those figures come from? by the_2nd_coming · · Score: 2

      right so this is significant because it raises the size the a small blackhole can be. right

      --



      I am the Alpha and the Omega-3
    7. Re:Where the hell did those figures come from? by Rasta+Prefect · · Score: 2, Informative

      Actuallly no, the majority of black holes are stellar black holes. These are created by the collapse of giant stars and are generally a few suns in mass. 1.4 being about the lower end for collapse, I believe. Take an astronomy course.

      --
      Why?
    8. Re:Where the hell did those figures come from? by LMCBoy · · Score: 2

      No, you missed the point that there are two kinds of black holes: Some are expired stars; the ones we can see have a normal star as a binary companion. Until now, these were always found to be between 3 and 7 solar masses. Others are "supermassive" black holes; we believe every galaxy has one of these at their center. These are typically more than a million solar masses.

      They are both gravitational singularities, but on a hugely different scale, and the physics of their formation is totally different.

      --
      Liberal (adj.): Free from bigotry; open to progress; tolerant of others.
  26. Re:Potential energy source? by the_2nd_coming · · Score: 2

    actualy if we could gather the massive amount of anti-matter being shot out of it then it would be very usful as an energy source

    --



    I am the Alpha and the Omega-3
  27. Making stars by Goonie · · Score: 2
    Crazy as it sounds, I've read (in Robert Zubrin's Entering Space - a highly entertaining and thought-provoking read even if you don't agree with all of it) it might one day be possible to use black holes (though probably not ones this size), to turn supergiant planets (Jupiter size and bigger) into stars, and then inhabit the moons surrounding the planet.

    Basically, it might one day be possible to move a black hole with the aid of its own gravity field and its radiation emissions. In essence stick a very large mirror in orbit round the black hole, and when the mirror is in the right position, dump some matter into the hole. When the matter gets swallowed, you get a burst of radiation which pushes the mirror in the desired direction. As the mirror is in orbit round the black hole, the hole gets pushed along as well.

    Anyway, when it gets to your supergiant planet, you dump it straight in. You might assume that the planet gets swallowed straight away, but apparently the push of the radiation generated in the process limits the inflow of material to a surprisingly slow rate. Hence, the core of the planet is a lot denser and hotter, and you get fusion starting up. Instant sun, just add planets/moons/whatever, which should last for many millions of years before it gets swallowed up.

    Of course, the engineering of such a mirror would be a truly astounding feat, and there's lots of other issues (not least, any convenient moons would probably have their orbits thrown in to chaos) but who knows what our distant descendants might be capable of?

    --

    Any sufficiently advanced technology is indistinguishable from a rigged demo
    --Andy Finkel (J. Klass?)
    1. Re:Making stars by Suidae · · Score: 2, Insightful

      In essence stick a very large mirror in orbit round the black hole, and when the mirror is in the right position, dump some matter into the hole. When the matter gets swallowed, you get a burst of radiation which pushes the mirror in the desired direction. As the mirror is in orbit round the black hole, the hole gets pushed along as well

      Wait, why would the hole move? seems like it might move toward the incoming matter a bit, due to mutual attraction (but not very much), and the burst of radiation presumably has an 'equal and opposite' push on the hole. The radiation pushes the mirror to a higher orbit. Seems like a way to move the mirror, but I don't see how it moves the hole. Its like a solar sail but you have to throw junk into the hole to get a push.

    2. Re:Making stars by Goonie · · Score: 1

      I'll be honest, you sound right, but I'll have to reread the book to make sure I'm quoting the concept correctly. It's more likely my own error in reproducing the way it would than a fundamental flaw in the system

      --

      Any sufficiently advanced technology is indistinguishable from a rigged demo
      --Andy Finkel (J. Klass?)
    3. Re:Making stars by Alpha+State · · Score: 2

      Think of a rocket engine - the explosion is focussed by the nozzle so that all the exhaust goes in one direction, so the reaction pushes the engine in the other direciton. The mirror would have to do the same - send a majority of the radiation in the opposite direction to that which you want to travel. This would push the mirror, presumably gravity drags the black hole along. The whole thing would be in a very precarious balance.

      You could just drag the black hole with a mass and a large rocket engine, or push a mass into it - but the mirror scenario uses the black hole for power.

    4. Re:Making stars by Suidae · · Score: 2

      Hmm, a giant parabolic mirror with the black hole at the focus (held beneath the dorsal guiding feathers)? All impinging radiation from the hole is redirected to provide thrust against the mirror?

      Ok, I can see how that might work. Just position the non-orbiting mirror to balance the pull of gravity with the radiation pressure. Thrust is limited only by the amount of radiation you can generate. Interesting.

    5. Re:Making stars by Anonymous Coward · · Score: 1, Insightful

      It would cheaper to search 1 million normal stars for terra-compatible planets than it would be to do this.

      Think about the force required to accelerate and slow the 3-14x the sun mass. Think about how much stronger than existing materials it must be to hang in that gravity field, and survive the inevitable radiation.

      Think about it falling in if it wasn't orbiting. Think about the balance problem, of balancing millions of tons of mirror, magnified by the excessive gravity field, with an explosion. Think about how unpredictable the accretion area of a black hole must be.

      Think about the mirror orbiting, so it doesn't fall in - which means you can't push against it (otherwise its orbit will change).

      Think about the size of the M in the F=MA equation, and derive what you think the F might need to be.

      Think about the unpredictability of energy output once you got the two together. Black hole flares and jets would keep cooking your people. The planet would shrink, and its gravity would change, thus affecting the orbits of the moons.

      Given all of those problems, I suspect that it would cost more usable energy - to create and position the mirror, and throw raw material at the black hole than it would output for the purposes of living. Ie using the same energy in some sort of localised fusion reactor would probably keep more people alive longer.

  28. yes you can... by efuseekay · · Score: 5, Interesting

    it's called the Penrose process. You use it on a rotating blackhole.

    The idea is that in a rotating blackhole, the minimum point of the potential moves around, so you can actually "slows" the blackhole while getting a nice angular momentum kick.

    Much like how you use the rotation of jupiter for slingshot. ("gravity assist" is a bad phrase, reality is that it's "angular momentum assist")

    --
    Mode (3) smart-aleck mode. Press * to return to main menu.
  29. Re:Potential energy source? by miracle69 · · Score: 2

    Well, regarding tapping energy from space, perhaps the best idea I've heard might possibly be the only way to make a potential perpetual machine.

    Oh god! I used those words. "Perpetual Machine". Surely someone is hovering over the keys about to remind me about the three laws of thermodynamics. 1) You can't win, 2) You can't lose and 3) You can't break even. Gimme a sec here. I understand them, I assure you.

    But...

    The only proposal I've ever seen that might give us a perpetual machine (or practical perpetual machine, as we'd be long dead before it ceased to work) involved two fixed points at a *very* *very* large distance apart. Between these two points, you connect them by some sort of cable of unbelievable properties and have once end attached to a large expandable spool of cable, which happens to be attached to a generator.

    BFD, right? Two fixed objects in the universe can't create energy.

    But... we can tap the energy of the expansion of the universe by allowing the spool to feed cable (while generating electricity) as the universe expands.

    No one knows if the universal expansion will be infinite or not. Should it be infinite, this would be a perpetual motion machine.

    --
    Linux - Because Mommy taught me to Share.
  30. errata by efuseekay · · Score: 1

    thinking a bit more, Penrose Process is nothing like the gravity assist. Sorry!

    --
    Mode (3) smart-aleck mode. Press * to return to main menu.
  31. not a new discovery by sokoban · · Score: 1

    GRS 1915+105 has been known about for quite a while actually. It was first seen as a strong x-ray source in the early 90's. http://www.ufoinfo.com/space/shockwaves.shtml is a great article giving info about this microquasar.

    --
    09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0 is the magic number.
  32. we could be living in one big black hole by goodchef · · Score: 1, Interesting

    On the subject of black holes, it's interesting to note that our entire (known) universe could be inside of a black hole. In fact, that super-black hole could be inside of a larger universe, and so on ad infinadum, or as far as you wanted to observe. conversely, since we seem to always be finding that our current "elementary" particules are in fact made up of smaller stuff. (atoms -> protons&electrons etc. -> quarks -> strings), black holes in our universes could contain entire universes within them.

    Or perhaps, since the massive gravity of a blackhole would warp 4-dimensional spacetime, perhaps they lead to other unknown parts of this universe, so far away that we've never observed or discovered it. in that case, having a black hole nearby wouldn't be that bad. We'd still have to find some exotic matter or something to counteract the tidal forces, and there's time discrepancy issues to deal with, but that's a somewhat moot point.

    --

    "Inflammable means flammable? What a strange country!" -Dr. Nick, The Simpsons

    1. Re:we could be living in one big black hole by SumDeusExMachina · · Score: 1
      That's all well and good when you think about it, but I thought black holes were just points in space?

      Perhaps you're referring to the event horizon?

      --

      Is your company running tools written by ma
    2. Re:we could be living in one big black hole by junkgrep · · Score: 2, Insightful

      ---On the subject of black holes, it's interesting to note that our entire (known) universe could be inside of a black hole.---

      This isn't really a good way to phrase it. "Inside" is not a concept that conveys any helpful meaning about this possibility, and in fact it sort of really confuses the issue. The basic physics point is this: it looks as if an entire universe can start from just a single singularity: that our universe could have started as a result of a quantum event. Victor Sternger has discussed this idea at length.

      ---We'd still have to find some exotic matter or something to counteract the tidal forces, and there's time discrepancy issues to deal with, but that's a somewhat moot point.---

      Moot because it doesn't seem in the least possible? This "matter" would have be so exotic that it would be unlike any "matter" that anyone has ever even concieved of before to survive the tidal forces.

    3. Re:we could be living in one big black hole by LMCBoy · · Score: 2

      "it's interesting to note that our entire (known) universe could be inside of a black hole."

      Wow, groovy.

      Except for the troubling lack of a singularity anywhere, and our complete failure to notice the tidal forces that should be ripping us all to shreds (how is that a "moot point"?)...

      --
      Liberal (adj.): Free from bigotry; open to progress; tolerant of others.
    4. Re:we could be living in one big black hole by EllisDees · · Score: 1

      Oh, comeon! The inflationary pressure in our own universe could be the result of the matter falling into a black hole in another universe, with time running in reverse (from the perspective of the 'outside' universe) because the infalling matter actually exceeds the relative speed of light (once again, to the 'outside' universe). You gotta have some imagination with this stuff. :)

      --
      -- Give me ambiguity or give me something else!
  33. im curious... by crazney · · Score: 1

    how do they work out the mass of a black hole?

    considering that they are so massive that the gravity causes it to be relitivly small, they can't work on size - so what do they work on?

    eh?

    --
    stuff
    1. Re:im curious... by JetJaguar · · Score: 2

      Except that the radius of the event horizon, even for super-massive blackholes is pretty small. Even if we could "see" the event horizon, I'm not sure there would be phenomenon happening there that would identify it as such. The event horizon is basically a theoretical construct, and isn't something that you would necessarily be able to see with a telescope, the physics gets really weird at blackhole event horizons, strange enough that nobody's really sure what it would look like, although some people have attempted to model it...

      The only way to determine blackhole masses is using stellar kinematics. Either by looking at galactic stellar rotation curves (for the case of super massive blackholes at galactic centers), or looking at binary systems where the companion to the blackhole is visible, and analyzing the affect of the blackhole on the visible partner. There is no reliable way to directly measure the Schwarzchild radius.

      --

      Shop Smart, Shop S-mart!

  34. Re:Potential energy source? by KarmaBlackballed · · Score: 2

    The only known way to use gravity to generate any kind of power is the harness things as they fall. The classroom description for things that can fall is that they have "potential energy."

    Hydro-electric is the only successful example I can think of. Here are the problems with trying to reduce our oil dependency by using this black hole:

    1. It is 40,000 light-years away. 40,000 LIGHT YEARS AWAY. Me thinks even a fraction of 1 light year is, uhhh, too far.

    2. What, you need another problem? Read #1.

    If you need another reason, think about this one: A light year is the distance LIGHT travels in one year. Electricity through a wire travels SLOWER than that. So, okay somehow you rigg up a generator close enough to the black hole to greate electricity. It will run down your super long wire to your PC where you are browsing Slashdot in about 40,000 years.

    --

    --- -- - -
    Give me LIBERTY, or give me a check.
  35. Stellar, middle-weight, supermassive by michaeldouma · · Score: 5, Informative
    There are three main classes of black hole. This article relates to the "stellar" type...

    Astronomers suspect that most black holes are produced when massive stars (at least 8-10 times the Sun's mass) reach the end of their lifecycle. This is a so-called "stellar black hole." Stellar black holes are the remains of dead stars several times heavier than the Sun, compressed to a diameter of a few miles or less. Supermassive black holes have masses comparable to those of a typical galaxy. These masses range anywhere from a million to 100 billion of our Suns. Supermassive black holes tend to be in the centers of galaxies, creating what are called Active Galactic Nuclei (AGNs). They may have formed in the early universe from giant gas clouds or from the collapse of clusters of immense numbers of stars. Lastly, the field of black holes, formerly dominated by heavyweights packing the gravitational punch of a billion Suns and lightweights just a few times heavier than our Sun, has another contender, the middleweight black holes, weighing in at 100 to 10,000 Suns.

  36. Article Style? by Suidae · · Score: 1

    Gah! Who wrote that? It reads like a list of facts, looks like somone just forgot the &ltul&gt tags.

  37. Those naive scientists by BillyGoatThree · · Score: 3, Funny

    "Reuters is reporting that scientists have found a massive black hole..."

    Sounds like somebody should learn to hover over Slashdot links before clicking them...

    --
    324006
    1. Re:Those naive scientists by xanadu-xtroot.com · · Score: 1

      SOMEONE please mark this funny (eventhough I know it's OT)! That was pretty good! :-)

      --
      I'm not a prophet or a stone-age man,
      I'm just a mortal with potential of a super man.
    2. Re:Those naive scientists by jallen02 · · Score: 1

      Uhm.. It is a story syndicated from reuters, thus "reuters reports" is technically and semantically correct. Excite happens to pay reuters for the ability to syndicate their content in their own site, but make no doubt that reuters generated it.

      ...

      Jeremy

  38. Re:Potential energy source? by tetrad · · Score: 1

    The black hole is 14 times the mass of the Sun, or roughly 3e+31 kg. The distance is 40,000 light year, or roughly 4e+20 m. Gravitational energy goes as m/r^2 ... (3e+31)/(4e+20)^2 ~ 2e-10 kg/m^2. Compared with the gravitational impact of the Earth or Sun, the black hole has essentially no influence at this distance, which makes it impractical to use as an energy source.

  39. Re:Potential energy source? by Violet+Null · · Score: 2

    Oh god! I used those words. "Perpetual Machine". Surely someone is hovering over the keys about to remind me about the three laws of thermodynamics.

    Yep. =)

    you connect them by some sort of cable of unbelievable properties and have once end attached to a large expandable spool of cable, which happens to be attached to a generator.
    ...
    But... we can tap the energy of the expansion of the universe by allowing the spool to feed cable (while generating electricity) as the universe expands.

    If I understand what you're saying (and I might not), you run into a few problems:

    * The cable would have to be infinitely long. Once we know how to make an infinite mass, infinite energy is a snap, but until then...If the cable is not infinitely long, eventually reach it's length and that's that.

    * (The more serious one) Assuming Big Bang theory, yadda yadda, the reason the universe expands is because of kinetic energy -- mass moving away from the "big bang". Assuming enough kinetic energy, gravity will never catch up -- this is true. However, if you're attaching a cable to an object and you expect the object to move the cable, the cable will be taking it's energy from the object, which means eventually the object would stop moving. Unless, of course, the cable is frictionless, but given a frictionless material, you can get perpetual motion much easier.

  40. oh man... by SaturnTim · · Score: 4, Funny



    oh man, that sucks...

    (Black hole? Get it? Sucks? )

    man, i picked the wrong week to stop sniffing glue.

    --ST

    --
    http://www.theMediaBunker.com
    1. Re:oh man... by dimator · · Score: 1

      hahah. i wish i had mod points.

      --
      python -c "x='python -c %sx=%s; print x%%(chr(34),repr(x),chr(34))%s'; print x%(chr(34),repr(x),chr(34))"
    2. Re:oh man... by geekoid · · Score: 2

      Soo, you ever seen a grown man naked?

      --
      The Kruger Dunning explains most post on /. http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect
  41. News just in! by redcliffe · · Score: 1

    A second massive black hole has been found in the slashdot.org headquaters, that is sucking in all records of previously posted articles. It was found after several duplicate articles had been posted to the front page of slashdot.org.

    :-) BTW if you don't realise, that is a *joke*!!!

  42. Re:Potential energy source? by Anonymous Coward · · Score: 1, Funny

    Ya see we get these poodles and we threaten
    to throw them into the black hole, they
    run real fast on a treadmill.... Its soooo
    simple and sooo obvious.

  43. Why use a black hole?!.... by Dutchmaan · · Score: 2

    .... when the Sun delivers to your door!

  44. Re:Potential energy source? by Violet+Null · · Score: 2

    Here's an interesting idea. It seems to me that black holes would provide a near infinite source of green (haha) power. Considering the fact that their gravitational power only increases, it is obvious that they constitute a never-ending supply of kinetic power

    Problem: You can't really harness potential energy (it's potential, see?) Sure, as the black hole gets bigger, you can rest well in the knowledge that, where you to plunge towards it, you'd gain a lot more kinetic energy, but until you actually start falling towards it, you're getting squat.

  45. My brother was telling me about this... by Wilbur+Bell · · Score: 1
    While he doesn't have the full scoop, being at NASA he does an inside track on some of the research, especially if it involves the Hubble or some of the clustering stuff he's working with.

    Anyway, aparantly there is quite some contention between the groups working on the project about the results and the interpretation of them. Such a huge black hole would have destroyed any such feeder star in the nova that created the black hole. But there it is, a relatively small star feeding it's very heavy brother.

    Try this link, it offers a bit more detail. Perhaps Walt can offer a bit more, he's better at explaining this stuff anyway.

    --

    Wil B.

  46. what i learned from star trek by ubugly2 · · Score: 2, Funny

    we can slingshot around the sun to a point when the black hole was just forming,then go to warp 9.9997 to get there,then create a dyson sphere around the forming black hole and then we can...we can{insert treknobabble here}.

  47. Pictures? by xanadu-xtroot.com · · Score: 1

    Is anyone able to find any pictures of this? I'm looking into pictures of other black holes (no GoatSex links please...), but I can't seem to find anything of this one.

    TIA!

    --
    I'm not a prophet or a stone-age man,
    I'm just a mortal with potential of a super man.
    1. Re:Pictures? by xanadu-xtroot.com · · Score: 2, Informative

      I just ran across this that would certainly explain a couple things:


      The Question We are deeply indebted to you if you can help us in obtaining two representative images about: 1)the real image (picture) of a "black hole" (photographed) 2)the most distant part of the Universe ever photographed.

      The Answer 1) There are no "real" pictures of a black hole. This is because black holes themselves do not emit of reflect any light (that's why they are called black holes), and they are too small and too far away to be imaged. There are images of binary star systems consisting of one normal star and one black hole, and of the central regions of Galaxies that are believed to contain black holes. There are some examples of the latter, taken with the Hubble Space Telescope, at: http://imagine.gsfc.nasa.gov/docs/ask_astro/answer s/970318d.html

      But these pictures don't actually show a black hole, you need to study the motion of stars to infer that there must be a black hole.

      2) Again, you may want to look at some Hubble pictures (with explanations): http://imagine.gsfc.nasa.gov/docs/ask_astro/answer s/970318d.html

      These are some of the most distant galaxies ever photographed; although some quasars are believed to be more distant, they make boring photographs (they just look like a point of light).

      Best wishes,

      Koji Mukai


      (no, this isn't my work, I just found it on a Google Search)

      --
      I'm not a prophet or a stone-age man,
      I'm just a mortal with potential of a super man.
  48. Re:Must...resist...urge... by ackthpt · · Score: 1
    Giant black hole found...

    Must resist urge!

    Aaahh, will weakening!

    Can't hold out much longer!

    Aiiieeeeee!

    Experts are looking into it.

    --

    A feeling of having made the same mistake before: Deja Foobar
  49. Re:Potential energy source? by Suidae · · Score: 1

    By unbelievable properties, I presume you mean that it doesn't expand with the universe? Otherwise the cable would expand at the same rate, resulting in no gain.

  50. Re: dmond by scorcherer · · Score: 1
    Scientists say a mini black hole can be found inside every package of the WinXP 'operating' system. They confirmed the theory, based on observations saying 'Suddenly everything sucks'.

    (The real reason why the graffiti artists did s/clicks/sucks has nothing to do with the level of suction of WinXP or black holes. It means that, instead of using a CLI, in WinXP you do everything under su.)

    --

    --
    The Cap is nigh. Time to get a fresh new account.

  51. article on the science journal nature, by vikool · · Score: 5, Informative
    here is the article on the science journal nature, it is slightly more detailed than the one on reuters

    http://www.nature.com/nsu/011129/011129-13.html

    vikas

    1. Re:article on the science journal nature, by Random+Walk · · Score: 1
      It's still only a press release, but at least it gives the reference to the original publication, which is a huge pro.

      I'm always annoyed by sensational and completely uninformative press stories that never give a reference to the original source where you could get better information. Motto: dumb down to the max, don't give readers a chance to get informed.

  52. here is the reuters link by vikool · · Score: 1

    http://reuters.com/news_article.jhtml?type=science news&StoryID=413514

  53. Re:Potential energy source? by gilroy · · Score: 4, Interesting
    Blockquoth the poster:

    Assuming Big Bang theory, yadda yadda, the reason the universe expands is because of kinetic energy -- mass moving away from the "big bang".

    Actually, the Universe expands because, well, the Universe expands... it's in the nature of the spacetime metric, as one of the solutions to Einstein's equations. It doesn't (necessarily) have anything to do with kinetic energy... it's not that planets, stars, etc., are flying into empty space. It's that space itself is growing larger with time.
    --
    The Mongrel Dogs Who Teach
  54. Nah, the Sun Is A Much Better Idea (TM) by jamesmartinluther · · Score: 1

    Hey, lets develop this green stuff which can take energy from the Sun and store it for later. Like, we could eat this green stuff. We could even feed this green stuff to other animals and make hamburgers and stuff.

    The possibilities of using the Sun for energy are endless.

  55. Blackhole's Gravity by WhiteBandit · · Score: 1

    Well I remember taking Physics quite awhile ago in high school. If my now faulty (God, I'm only 20!) memory still serves me right, the gravity of blackholes are really nothing to be in awe of. (To a specific point of course).

    In the following example, I will use Sol (our sun!) as the subject. Now even though it could never turn into a blackhole, we'll hypothosize it is. Basically, if it turned into a blackhole, this "amazing gravity" that sucks even light in, would only be effective within the *original* volume of the sun. i.e; Earth would be fine. Everything should orbit normally without a problem. Now once you get near where the surface of the sun once was and even within the original volume, this is where this astronomical gravity comes into effect.

    Now I honestly know I wasn't sleeping during that part of class (if so, then this is some ellaborate theory I've just created...) so I may be wrong. But I notice everyone talking about how we could "use it as a slingshit for space travel" or "Oh No! We may be sucked in!!", but from what I remember studying, it really isn't like that.

    1. Re:Blackhole's Gravity by TheOnlyCoolTim · · Score: 1
      without a problem.


      We'd either be dead from the cold, or possibly from some radiation it would shoot out when it collapses. No problem at all.

      While I am now talking out of my ass, I think the reason you can use it is a slingshot is not the great amount of gravity it has but the fact that that gravity is more or less a point source. Thus your Spacecraft could get very close to ALL the mass so there would be great effect: instead of your semi-orbit around the Sun or Jupiter which would have to be very very big and take a long time, your time in the gravity well of the black hole would be a lot shorter with a lot more acceleration.

      Tim
      --
      Omnia vestra castrorum habetur nobis.
  56. Mailing List! by SiMac · · Score: 1

    God has a (private) mailing list to coordinate announcements of this nature so that religions can receive updates, but the scientists broke the schedule and released this before many religions had updates...

    Oops, wrong story

  57. Re:Potential energy source? by Floody · · Score: 1

    "'Feed' it enough to keep it from collapsing" ??

    By definition, it has already infinitely collapsed. How can it "collapse" again?

    Theoretically, it could "evaporate" (Hawking radiation), but for stellar (or larger) mass holes, the energy emitted via Hawking radiation is less than cosmic background radiation. Thus "evaporation" can't even begin for a long, long time. Long after all fusion in the universe has ceased.

  58. Re:Potential energy source? by Graspee_Leemoor · · Score: 1

    "Between these two points, you connect them by some sort of cable of unbelievable properties and have once end attached to a large expandable spool of cable, which happens to be attached to a generator."

    Could you run some fibre-optic along with that ? I want to put a bsd server in the universe on the other side of the singularity.

    Welcome to alternate.www.freebsd.org.

    Hey- if it's a *mirror universe* on the other side we could set up lots of mirror sites in it for ironic purposes.

    But seriously, does anyone know what would happen to fibre-optic cable in a black hole ? Would it gain infinite mass or something ? Would the tcp packets be really phat ?

    graspee

  59. Re:Potential energy source? by ceoyoyo · · Score: 1

    One more, bigger problem. As the Universe expands, so does space. This means that your cable gets longer and longer. So does your measuring tape of course, so you don't know about it, but your spool of cable will never budge at all.

  60. Stop the sun now! by piecewise · · Score: 3, Funny

    Come, fell Slashdotters! We must stop these scientists and our fellow readers for discussing extracting kinetic energy from black holes!

    Instead, we must focus on more realistic goals:

    1. Building giant solar structures on top of our homes!
    2. Trying to run our SUVs using corn!
    3. Convince ourselves that wind mills are actually doing anything for us!

    Come! Unite! Ignore the energy crisis and come up with silly ideas!

    Ooh, i forgot one.

    4. Believe that Americans might actually CONSERVE! Hhaahhaha!

    Sorry -- it's too bad being cynical didn't produce a significant amount of energy. ;-)

    --
    The next comment I write will be ready soon, but subscribers can beat the rush and see it early!
    1. Re:Stop the sun now! by ShoeHead · · Score: 1

      Whare *are* the physics concerning black holes? Would it be profitable/possible to tie a large weight or something on a huge line, and link it to a super-heavy flywheel or something?

    2. Re:Stop the sun now! by discogravy · · Score: 2

      Sorry -- it's too bad being cynical didn't produce a significant amount of energy. ;-)

      if cynicism ever actually produced energy, America would actually look forward to elections and MS products! too much to hope for...

      --
      FreeBSD for the impatient.
    3. Re:Stop the sun now! by LMCBoy · · Score: 2

      It's possible to extract huge amounts of energy by simply dropping matter into black holes. In fact, this is the most efficient way to get energy from matter. Too bad there aren't any nearby. Ah well, maybe we'll make one of our own someday.

      --
      Liberal (adj.): Free from bigotry; open to progress; tolerant of others.
    4. Re:Stop the sun now! by ChelleyBean · · Score: 1
      Slashdot: When News Breaks, We Give You The Pieces

      Oh my... is this available on a T-Shirt?

      love,
      me

    5. Re:Stop the sun now! by flewp · · Score: 1

      Too bad there aren't any nearby.

      I'm pretty happy there aren't any blackholes around...

      --
      WWJD.... for a Klondike bar?
  61. Wilbur gives us the link to esa.org above ... by gigi · · Score: 1

    that's where it all came from.
    let's hope we don't get eaten by this baby.

  62. hmm... by slobberjaws · · Score: 1

    i thought i covered that up last night, must have been that pizza.................

  63. PUBLIC ADDRESS TO THE TROLL COMMUNITY by Anonymous Coward · · Score: 1
    We, the troll-friendly readers of Slashdot, are unhappy with the poor quantity and quality of trolls posted to this, a story which offers such great potential for goatse.cx links, references, and ASCII art.

    Where are you? Why have you forsaken us? Are we doomed forever to read "Insightful," "Interesting," and (god forbid) "Funny" posts, with no promise of sweet trolls waiting at the bottom of the page to entertain us with insults, cryptic remarks, and links to gay porn?

    What has become of Slashdot's once-mighty troll empire?

  64. Re:Potential energy source? by TheOnlyCoolTim · · Score: 2

    We're actually rather close to making our own black holes I think....

    There was worry when the Relativistic Heavy Ion Collider at Brookhaven went online that among other ways of ending the World (Strangelets) or the Universe (transition to a new vacuum state), that the collisions would produce a black hole which would fall into the center of the Earth and consume it.

    There was a report on the RHIC website, which I can no longer find as the website seems to have been overhauled, where they used complex maths I don't understand to decide that (a) The probability of the thing making a black hole was somewhere around 10 to the -30 and (b) even if it did make a black hole it would be a small one that would "evaporate" instead of being able to grow and consume the Earth.

    There are also some good books where there are black holes in the Earth - read "Earth" by David Brin, which is entirely about a black hole falling into the Earth, and the Hyperion series by Dan Simmons is set in a future universe in which evil AIs made a scientific experiment drop a black hole into the Earth (I don't want to give out too much of the plot, but everyone thinks Earth is destroyed - they are wrong).

    Tim

    --
    Omnia vestra castrorum habetur nobis.
  65. Re:Microsoft by rjamestaylor · · Score: 2

    At least they're offering a fix...

    --
    -- @rjamestaylor on Ello
  66. Paper can also be found. . . . by astrobabe · · Score: 1

    at http://xxx.lanl.gov/abs/astro-ph/0111538 in various formats. . . . .

  67. Possible black hole merger? by MetricT · · Score: 2, Interesting

    I remember reading in the literature about a survey of the masses of all known stellar-mass black holes, which led to the interesting discovery that, for reasons unknown, a majority of black holes mass about 7 Msun.

    I can't help but wonder if a 14 Msun black hole is the remnant of a black hole merger. Maybe we'll be able to compare the black-hole-merger-grand-challenge problem with reality after all.

  68. Sling-what? by itwerx · · Score: 1

    Is it just me or is the "slingshit" typo in a discussion about "black holes" entirely too apropos?
    Next thing you know people will think Uranus is a black hole...

    Go ahead, mod me down, it's still funny! :)

    1. Re:Sling-what? by WhiteBandit · · Score: 1

      haha! Oh dear. I didn't even notice I typed "slingshit"! I mean the "i" and the "o" are right next to each other. Well so much for trying to sound intelligent :-/

  69. Massive Black Holes, Massive Black Holes by Grayswan · · Score: 1

    I mean, aren't ALL black holes "Massive"? I mean, you never hear stories about *tiny* black holes.

    When everyone thinks alike, no one is thinking.

    --
    If you open your mind too wide, people will throw trash in it.
  70. Re:Potential energy source? by Alpha+State · · Score: 2

    In "A Brief History of Time" by Steven Hawking, radiation from black holes is discussed. Basically, they harness zero-point energy when the "quantum foam" effect occurs at the event horizon and one particle of the matter / antimatter pair is dragged into the hole. The particle that escapes appears as radiation while the trapped particle actually reduces the black hole's mass by matter / antimatter annihilation, returning the borrowed Planck energy. In this way black holes evaporate.

    All you have to do to generate energy from a black hole is to harness this radiation, effectively directly converting mass from the black hole into energy. You can keep it going by dumping anything you like into the black hole.

    Disclaimer: it's a long time since my physics days, there are probably a lot of errors in the above. And it's only a theory anyway. And black holes can be dangerous - please do not attempt this without adult supervision.

  71. 40,000 Light Years? by BoarderPhreak · · Score: 3, Funny

    Would that be the Delta or Gamma quadrant? ;)

    1. Re:40,000 Light Years? by Alsee · · Score: 1

      Would that be the Delta or Gamma quadrant? ;)

      That reminds me - How come they never mention the Beta quadrant?

      -

      --
      - - You can't take something off the Internet! That's like trying to take pee out of a swimming pool.
    2. Re:40,000 Light Years? by pete-classic · · Score: 2

      We don't discuss that outside the Empire.

    3. Re:40,000 Light Years? by Fweeky · · Score: 1

      The Beta version of Galaxy Quadrant[TM] was reported to be too unstable for production use; spacefaring races are advised to wait for the release version.

  72. An even bigger question is... by JetJaguar · · Score: 2

    Assuming there were planets orbiting around the pre-blackhole star would they survive the super-nova explosion that also creates the black hole? I suspect that most planets would very nearly be ablated away or vaporized or both...

    --

    Shop Smart, Shop S-mart!

  73. Re:Potential energy source? by goethean · · Score: 1

    That's really the problem with most available holes, isn't it?

    --

    _____
    God is only experiencing itself -- Nisargadatta Maharaj
  74. Re:Potential energy source? by Mr.+Piccolo · · Score: 1

    Not hot enough, eh? Throw a few Pentium 4s in there and it should be hot enough for anybody!

    --
    Glückwünsche, haben Sie Slashdot ermordet, indem Sie zum korporativen Druck beugten und Subskriptionen einlei
  75. Publicly available space information? by rice_burners_suck · · Score: 2

    This is an amazing discovery. I'd like to know what kind of equipment and techniques scientists (or should I say astronomers) use to compute the mass of things such as black holes.

    In fact, I've always been interested in space, stars, planets and related subjects. If there was some software (inexpensive or even free) that allowed me to perform my own computations (perhaps using information on the net which is published by observatories or NASA or whatever), that would indeed be the coolest thing. I've searched for information like that, but I haven't found any, so I assume that space explorers down here on Earth don't make any of their information publicly available. It's a shame though.

    Of course, I know of programs that have maps of the stars and whatever, but there really isn't any information on things like blue/red shifts (as an example off the top of my head).

    Well all of this stuff probably requires supercomputers anyway, which is something I don't have.

    Oh well.

    1. Re:Publicly available space information? by LMCBoy · · Score: 2

      Actually, most of the data used by astronomers is publicly available. Try the following:

      HST data archive: every HST image. Also has other mission data.

      Astronomical Data Center: archive of data tables published in peer-review astronomy journals

      NASA/IPAC Extragalactic Database: index of known data for other galaxies. You can get redshifts here, for example.

      The software used by astronomers is also generally publicly available. For example, Debian Linux ships with IRAF, the image reduction software that most of us use (the ones who can't afford IDL anyway).

      --
      Liberal (adj.): Free from bigotry; open to progress; tolerant of others.
  76. Owner of black hole sued! by freaker_TuC · · Score: 2, Funny

    The owner of the black hole, 40,000 light years away has been sued by the RIAA because of distributing matter against the DMCA.

    DMCA 3, FREEDOM 0

    The owner of the black hole takes the charge not lightly and plans to close the black hole completely leaving space and time in it's destruction. GOD 1, DMCA 0

    --
    --- I am known for the ones who want to find me on the net. Is that a privacy risk or a privilege? One might wonder..
  77. Giant black holes? by epsalon · · Score: 1

    Imagine a beowulf cluster of those...

    --

    Make even shorter URLs - 8LN.org

  78. giant hole by ljoas · · Score: 2, Funny

    Ok!

    Who sent the goats.ex link to NASA?

    /L

  79. initial report by vikool · · Score: 2, Informative
    this page gives the first report of an anomaly that came about on the GRS1915+105

    http://www.nature.com/doifinder/10.1038/35107019

    vikas

  80. How about finding a small one? by cra · · Score: 1

    I'd like to have a small ome, myself. Just large anough to fit inside my kitchen waste-bin, so that I could just put all my garbage into it, and never have to carry it out. I know you'd like one, too.

    --
    This message has been ROT-13 encrypted twice for higher security.
  81. The theories does not fitt or is it the messure by Orre · · Score: 1

    Do anyone know if the messure of black hole density is validated and verified?

    Maybe the messure is the problem and not the theory of how black holes funktion etc. !

    1. Re:The theories does not fitt or is it the messure by Hoi+Polloi · · Score: 1

      You can measure their density based on how objects orbit them.

      --
      It is by the juice of the coffee bean that thoughts acquire speed, the teeth acquire stains. The stains become a warning
  82. Mod parent up (and other things) by Snafoo · · Score: 2

    Actually, I find that the interior of singularities usually has, like, a lot of blue-yellow plasma zipping around in it. Also, there are these weird five-dimensional aliens that look like your son, Dax, and Major Kira.

    --
    - undoware.ca
  83. Math IS important. by Magnusite · · Score: 1

    A three dimensional object should be measured in volume, not area. Plugging the numbers into the equation yields a volume about 10 times the volume of the sun. Also, I don't see how 2.95*10^6 == (1.39*10^6)*4. It seems to be twice the radius, not four times.

  84. Re:oh, NO!...Uhhh...dunno. by A_Non_Moose · · Score: 1

    (Note: I'm going to blather on and off topic.
    If your time is precious...skip this post
    If you don't care either way...read or whatever)

    Joel8x wrote:How the hell does rjamestalylor who posted virtually the same exact post one minute later than you get a score of 2 Funny {snip}

    I hate to say it, but you answered your own question...you should have waited, but this is what I got, moderation wise:

    Offtopic=1, Redundant=1, Funny=4, Total=6.


    Offtopic...humm, mebbe, mebbe not...Black Hole the movie referrence to the bh the thing... must be a objective and admit I had a point.

    I honestly think some of the "mislabeled redundant posts" are because of the *newest first sorting*...that is prolly why.
    Like it really matters, eh?

    Don't sweat it, dude...

    Like I have in my sig, and like I've said to you:
    I have answered my own question.

    Reguards,

    Moose.

    --
    Have you read the moderator guidelines? Well, have you, PUNK? (and I want a Karma: Gnarly option)
  85. infinite within the finite by 0x4B · · Score: 1

    It's never realyl occured to me before that a black hole would be of infinite size in terms of out ability to measure distance (either with light, or a really big yard stick). Even if the mass is finite.
    The thing that strikes me is that the universe itself it finite in sixe (though unbounded - akin to the surface of a sphere from a 2D perspective).

  86. Re:Potential energy source? by tenman · · Score: 1

    a black hole which would fall into the center of the Earth and consume it. ... even if it did make a black hole it would be a small one that would "evaporate" instead of being able to grow and consume the Earth.

    I'm not up on black holes, but does the black hole eat it way to the center of the earth? Like consume all the engery/matter/stuff in it's path? If this was the case, and using the black hole as a source of energy was a concern, couldn't we use black holes, to drill for resources that are deep below the earths crust/mantle/core? Better Yet, I've seen /. articals about mining the moon/astroids/meteors/rosie o'donald huge ass. Wouldn't that be a great way to punch the holes to the payload? I might be on the wrong track. I have never accused of being right in the head

  87. Bad Idea... by DataGrunt · · Score: 1

    Scientists should not be allowed to study any more black holes. Think about it, they study it, they think they can explain it...
    There was an article posted two months ago about a group of scientists getting together and making plans to build a super particle accelerator. It was said to be strong enough to create mini black holes. Now that they think they know what a black hole is they are going to make one on earth. Does that just not sound like a bad idea to anyone else? Scientists are going to kill us all.

    "Today I stood in the rain and it was my job" USMC

    1. Re:Bad Idea... by Hoi+Polloi · · Score: 1

      I hear a giant sucking sound and it isn't coming from Mexico! [ref. Ross Perot]

      --
      It is by the juice of the coffee bean that thoughts acquire speed, the teeth acquire stains. The stains become a warning
  88. Bush by macdaddy · · Score: 2

    ...and yet the biggest black hole competition is still left undecided. The final two contestants are "The Space Between Bush's Legs", and "The Vacum Between John 'beat by a dead guy" Ashcroft's ears".

  89. Re:Potential energy source? by nerdlyone · · Score: 1

    "Actually, the Universe expands because, well, the Universe expands... it's in the nature of the spacetime metric, as one of the solutions to Einstein's equations. It doesn't (necessarily) have anything to do with kinetic energy... it's not that planets, stars, etc., are flying into empty space. It's that space itself is growing larger with time." _____ I have read that it is basically kinetic energy that causes the expansion of the universe--leftover outward-moving energy from the big bang itself. This outward momentum (maybe not exactly the right term) is countered by gravity. To imply that it is "inherent in the space-time metric" means that there is some force causing expansion. That said, recent supernova observations actually did indicate that the expansion of the universe is *accelerating*, which means that there *is* a force causing expansion of the universe. But this acceleration to the expansion is different than the initial expansion itself, which is basically kinetic energy. I realize that space itself is also expanding, but that is a *result* of matter expanding, not the *cause* of matter expanding.

  90. Diameter of black holes by GPS+Pilot · · Score: 1
    compressed to a diameter of a few miles or less.

    I have heard black holes referred to as "singularities." If the diameter is a few miles, that's pretty far from a singularity. Are you referring to the diameter of its event horizon, rather than the the diameter of the object itself?

    And, if the middleweight class ranges from 100 to 10,000 Suns, but supermassive starts at a million Suns, what class does a hole belong to if it weighs between 10,000 and one million Suns? Or is there a gap, and no black hole has ever been found that falls between those classes.

    --
    That that is is that that that that is not is not.
    1. Re:Diameter of black holes by supruzr · · Score: 1

      I have heard black holes referred to as "singularities." If the diameter is a few miles, that's pretty far from a singularity. Are you referring to the diameter of its event horizon, rather than the the diameter of the object itself?

      I'm hoping that when mister Douma said "compressed to a diameter of a few miles or less" he was referring to the instant at which the black hole can said to be created. As far as the volume of a singularity, pick your favorite Grand Unified Theory. Stuff like this is where physics and quantum mechanics don't like to agree. The classic idea is that the singularity is a point, and thus cannot have volume. Mathematically speaking, using the density equation d=m/v, where the density of a black hole must be infinite, to cause the effect it does, and the mass is the same as that of the star that used to exist there, the volume must approach zero. However, if you happen to believe in some derivative of string theory, 0-dimensional points cannot exist, and I don't even think I can get into how string theory/M-theory explains black holes. I'll leave that to someone else.

      As far as the discrepancy of black holes between 10,000 and 1 million Sols, it's quite possible that one in that range has never been observed. We haven't exactly found a lot of black holes, and there are even still those that believe black holes don't exist. We don't exactly have conclusive proof to that effect, it's just that these anomalies we keep finding REALLY REALLY closely resemble what we'd expect a black hole to be like. Go figure. But hey, it could always be the Amazing Super Mega Anti-Reverse Cosmic Effect that makes us THINK we're finding black holes, and THEN who is going to be laughing? THEN who will be called luddite crackpots for not believing? HUH?

  91. Gravity assist doesn't come from rotation by GPS+Pilot · · Score: 1

    You could do a gravity assist at Jupiter even if the planet didn't rotate on its axis at all.

    Jupiter's orbit around the sun changes by a negligible amount when you do this, but the rotation on its axis (the length of a Jovian day, if you will) is unaffected.

    --
    That that is is that that that that is not is not.
    1. Re:Gravity assist doesn't come from rotation by efuseekay · · Score: 1

      yes. which is why I added my errata on the error of my ways.

      --
      Mode (3) smart-aleck mode. Press * to return to main menu.
  92. Not a Black Hole... by Domini · · Score: 2

    The article mentions 3 to 7 suns begin the normal size of a black hole...

    This does not seem correct.

    I have been told that this would rather be described as a "pulsar".
    (Dr Evil made me do it! ;) )

    Anyhow, this is just my 0.02 worth of destructive critisism...
    :P

    1. Re:Not a Black Hole... by Domini · · Score: 2

      My friend wish to apologise:

      ---
      The correct range for neutron stars is 1.2 - 3 solar masses and black holes
      from 3 - billions of solar masses....
      d
      ---

  93. Black holes are not vacuum cleaners by B.D.Mills · · Score: 2

    From the article:

    Black holes suck in everything near them including light...

    This is a very common misconception, judging by the number of otherwise well-informed Slashdot readers who have been repeating this fallacy. Black holes do not suck in things any more than the Earth or Sun do. The unusual gravitational effects of a black hole are only evident for bodies that are close to the event horizon.

    If the Sun was replaced by a black hole with the same mass, the planets and other bodies in the solar system would continue to orbit as if nothing unusual had happened. They would NOT be "sucked in".

    --

    The only thing necessary for the triumph of evil is for good men to do nothing. - Edmund Burke
  94. Re:Potential energy source? by TheOnlyCoolTim · · Score: 1

    Theoretically I guess you could use a black hole to dig a tunnel, but I do not think it would be practical and it is definitely too risky. You don't want to have to worry about a problem with your mining operation ending the world.

    A rogue black hole generated on the surface would not generally eat its way to the center of the Earth. The event horizon of anything we make would probably be very small, only able to capture a few molecules at a time. It would fall more or less invisibly into the Earth (maybe there would be some radiation you could notice). Then it would would go back and forth underneath the Earth, with gravity slowing it down and moving it towards the Earth's core. Meanwhile the whole time it would be consuming matter, and eventually it would consume the Earth. Maybe, not sure on this, but it might be that we wouldn't notice the Earth being consumed until a few hours before the Earth was completely consumed, because the rate of growth would increase quite a bit.

    Tim

    --
    Omnia vestra castrorum habetur nobis.
  95. Virgin target! by _cnn_ · · Score: 1

    Yeah, virgin target. Let's go hack it!

  96. Re:Potential energy source? by gilroy · · Score: 2
    Blockquoth the poster:

    I realize that space itself is also expanding, but that is a *result* of matter expanding, not the *cause* of matter expanding.

    I'm sorry to repeat myself, but you are in error here. Even in an empty Universe, the Einstein equations lead to a spacetime metric that is either expanding or contracting. (I believe this solution is called a deSitter Universe.) It doesn't take matter at all, so it can't depend on the kinetic energy of matter.

    To imply that it is "inherent in the space-time metric" means that there is some force causing expansion.

    No, actually, it doesn't mean that at all. It means exactly what it says: the metric of spacetime -- the set of notional "metersticks" by which distance is defined -- is simply expanding as a function of time. It's in many ways the exact opposite of a force: there's no agent acting, no particle mediating the expansion, no interaction causing it. It just happens, because the structure of spacetime is such that it expands.


    People intiuitively want a stable Universe, so they try to imagine things that "cause" the expansion. I believe it's very analogous to the Newtonian breakthrough in dynamics: For a long while everyone thought that the "natural" state of motion was to be at rest; therefore physical theories "had" to explain constant-velocity motion. But Newton saw that constant-velocity motion -- of which rest is just a particular case -- is the natural thing, and it is accelerations that must be explained. Likewise, people think the Universe "should" be stable and therefore think one must explain the expansion. But the Einstein equations show that the expansion is natural and therefore need not be explained further.

    --
    The Mongrel Dogs Who Teach
  97. Re:Potential energy source? by nerdlyone · · Score: 1
    In response to your comments on my post, I think you are getting a bit nitpicky, and not technically accurate. You wrote:

    The correct description is as the other poster says: space is expanding, though gravity is slowing down that expansion.

    Space expands because matter is expanding or moving. The space-time and matter are not separable, you can't talk about a space-time metric existing without matter existing somewhere, because matter dictates the structure of the metric (as well as the metric dictating the movement of matter).

    You also said:

    No. The metric changes with time, but there are no forces involved in gravitational phenomena.

    I think you are confusing the difference between models and reality. Both Newton and Einstein came up with models. Einstein replaced a gravitational potential (the source of a force) with a space-time metric. You can view the universe as one in which matter causes a gravitational force to be exerted or one in which matter causes the geodesics of space-time to be shaped differently, which causes matter to accelerate. They are one in the same. To say that "there is no force involved in gravitational phenomena" is merely a choice of models. It also totally misses my point.

    My point was that if the metric is indeed changing with time, there has to be a reason behind it--the metric does not control the universe, it only models it. The metric changes locally near matter because the matter is there, not because it is "inherent in the metric" (unless you think the metric creates the universe, rather than the metric merely modeling the universe). Likewise, the metric changes with time because of other conditions, namely, the negative vacuum energy density (positive vacuum pressure). This is what caused the initial expansion of the universe--hot radiative pressure when so much matter and energy were confined to a "small" region (though size doesn't have much meaning since it was really the entire universe), creating a really high energy density.

    I also wrote:That said, recent supernova observations actually did indicate that the expansion of the universe is *accelerating*, which means that there *is* a force causing expansion of the universe.

    You replied:No, that's not true either. The geometry of space obeys field equations, and can change with time. No forces are involved. What you say would be true if gravity were described in Newtonian terms by a force, but general relativity does not describe any gravitational phenomena in terms of forces.

    Gravity *is* described in Newtonian terms by a force. You seem to think that because one model (Einsteins) does not refer to the term "force" then force does not exist. The "force" in Einstein is buried in tensor equations, and how they determine the shape of geodesics, which determine how matter moves. But both models describe the same phenomena (though I agree relativity does it more accurately).

    And finally, you write:Again, no. The matter in the universe flies apart because the intervening space expands.

    Whatever, you desire to contradict literally everything I posted has gotten in the way of your understanding. Your statement indicates that you think space-time's expansion causes matter to move apart. This is exactly the opposite of what is happening. Space-time would not be doing what it is doing if there were no matter. Ultimately, space-time is used to describe the location and effect of matter (via gravity) on other matter. Matter determines the shape of space-time. Movement of matter causes the metric to change over time. I agre the two are self-referential, but without matter, the space-time would not exist. And anywhere you have matter, you will have space-time. Matter is the important quantity.

  98. Re:Potential energy source? by nerdlyone · · Score: 1
    I'm sorry to repeat myself, but you are in error here. Even in an empty Universe, the Einstein equations lead to a spacetime metric that is either expanding or contracting. (I believe this solution is called a deSitter Universe.) It doesn't take matter at all, so it can't depend on the kinetic energy of matter.

    The deSitter Universe is just a model of the universe with zero curvature--one in which there is *exactly* enough energy to keep the matter therein expanding forever (i.e., zero curvature).

    I have never heard of a space-time model for a matterless space-time. I couldn't find it under deSitter. I would be very interested to read such, if you can provide a cite.

    I agree that the expansion of the universe is not caused by some currently acting force, I believe you may have misunderstood my post on that point. But your statement seems to indicate you do not seek any initial cause for the state of the expansion--that it started expanding for no reason. Even a newtonian particle at constant velocity (to use your example) needs to somehow obtain that velocity. In the case of the matter in our universe, I always thought it was because of the initial energy density and radiative pressure from the big bang, giving an initial impetus to matter. Indeed, other authors seem to think this too, see here for example (just somethign I turned up on a quick search).

    Finally, something that may have caused some confusion, I mentioned recent supernova observations and the idea that there *is* a force causing *acceleration* of expansion. What I posted is accurate, do a google search for quintessence or dark energy.

  99. Re:Potential energy source? by gilroy · · Score: 2
    Blockquoth the poster:

    Even a newtonian particle at constant velocity (to use your example) needs to somehow obtain that velocity.

    Um, no. Constant velocity does not to be explained in Newtonian physics. It is just every bit as "natural" as being at rest. You might have an intuition or a bias that everything "should" have begun at rest and therefore the current state of non-rest must be explained. But that isn't implicit in Newtonian physics. The advance made by Newton was exactly the realization that changes in velocity required agents but that constant velocity does not.

    I mentioned recent supernova observations and the idea that there *is* a force causing *acceleration* of expansion.

    What is implied by the recent supernova observations -- and we will leave aside the argument over whether Type I supernovae are really standard candles that can be used for this sort of thing -- is that the rate of expansion of the Universe is accelerating. So much we agree upon, although we should both be cautious that these results are still preliminary (and in fact seem recently to have been scaled back some).



    One possible explanation for this acceleration -- and the only one that I've seen attract serious attention from cosmologists, though they are far from unaminous on this -- is the presence of a cosmological constant in Einstein's equations. A cosmological constant acts like a pressure density defined everywhere in space and keeps the metric expanding ever faster. But it doesn't exert a "force" in any standard usage of the word. We don't need a repulsive force to accelerate the expansion, because space itself is exapnding and carrying the matter along with it.


    I will admit to misusing the name "deSitter Universe", which is apparently not the construct of which I was thinking. I guess it's time to dust off ole MTW and try again.

    --
    The Mongrel Dogs Who Teach
  100. Re:Potential energy source? by nerdlyone · · Score: 1
    Um, no. Constant velocity does not to be explained in Newtonian physics. It is just every bit as "natural" as being at rest. You might have an intuition or a bias that everything "should" have begun at rest and therefore the current state of non-rest must be explained. But that isn't implicit in Newtonian physics. The advance made by Newton was exactly the realization that changes in velocity required agents but that constant velocity does not.

    Yes, duh. But since we are talking about the big bang model, and since this model posits that all these particles (i.e., all matter in our universe) are moving away from each other (NOT in the same direction) then you have either swallowed some pretty amazing initial conditions which you have twice implied need no explanation, or else there is a reason for the particular movement of all this matter. Your glib reference that space-time is just that way isn't very satisfying. I also don't think it is correct, with all due respect. You obviously know some physics.

    A cosmological constant acts like a pressure density defined everywhere in space and keeps the metric expanding ever faster. But it doesn't exert a "force" in any standard usage of the word. We don't need a repulsive force to accelerate the expansion, because space itself is exapnding and carrying the matter along with it.

    Ah, we agree, though not on terminology. You can refer to an added term (the C-constant) and deny that forces exist, but then you have to admit that the added term includes the effects of a force.

    And again you say we don't need a "force" to explain the acceleration of expansion. I guess we don't as long as we are using a math model that does not refer to force explicity, though it includes the effects implicitly by another method. But I am not sure you understand this. You have repeatedly stated that no force is needed because space itself is expanding.

    Now, let me be clear, I am not talking about mere expansion, but acceleration of the rate of expansion--a different thing by one time differential.

    This definitely requires some kind of force to be acting. Particles don't change their velocity without a force (as you correctly pointed out). Neither does space-time. It sounds like you think we cannot inquire into why space-time behaves the way it does--it is just the metric, or the constant. But space-time depends on the matter therein, period. The two (space-time and mattter) are self-referential--they both affect each other, and matter EFFECTS space-time, i.e., brings it about. Space-time does not bring about matter. The only reason we have space-time is to describe how matter (and energy, to be technically correct) acts. If you take away the matter and energy, the idea of space-time is meaningless.

    The reason space-time is expanding is, respectfully, not "because it is inherent in space-time" as you have twice stated (that is the original reason I posted--to disagree with this gross oversimplification). It is because the matter in our universe is moving. Move the matter, and your space-time geodesics, etc. change. If you have matter flying apart, away from other matter, then you have a space-time that looks like ours does, i.e., expanding. But to say that matter (and our universe) is expanding because the space-time metric looks the way it does is backward. That implies that the universe is governed by our model of the universe. The metric, the cosmological constant, these are just part of the model. You can't refer to them in order to explain, only to describe.