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Space Science

First Cosmological Results From MAP 292

riptalon writes "The Wilkinson Microwave Anisotropy Probe, a NASA Explorer mission has announced the first results based on a year of observations from the L2 Lagrangian point. MAP carries two back-to-back microwave telescopes to study variations in the cosmic microwave background, to much greater accuracy than the COBE satellite. The excruciating details of the results on the age, geometry and composition of the universe can be found in this paper. Executive summary: 13.7 billion years old, flat, 4.4% baryons, 22% dark matter and 73% dark energy."
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First Cosmological Results From MAP

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  • Will it heat my cosmic coffee?


  • Does Dark Energy suck or blow?

  • huh? (Score:3, Interesting)

    by dirvish ( 574948 ) <dirvish@GINSBERGfoundnews.com minus poet> on Tuesday February 11, 2003 @07:56PM (#5284264) Homepage Journal
    Anyone care to let us non-space nerds know what baryons, dark matter and dark energy are? TIA.
    • by goatasaur ( 604450 ) on Tuesday February 11, 2003 @08:00PM (#5284290) Journal
      Baryons [wikipedia.org]

      Dark Energy [wikipedia.org]

      Dark Matter [wikipedia.org]

      Hope this helps you out a little. :)
      • from the definition of dark energy:

        This energy would act like a vacuum pressure, pushing things apart.

        now I ask you... what is vacuum pressure, and how does it push things apart? I thought vacuums sucked things in...

        • by jaoswald ( 63789 ) on Tuesday February 11, 2003 @08:44PM (#5284503) Homepage
          In this case "vacuum" is physicists' name for "empty space," meaning "as empty as possible." On earth, "empty" means "much less matter than in the atmosphere."

          When that empty space is surrounded by the earth's atmosphere, the atmosphere presses on the container that encloses the empty space. Open a hole in the container, and the atmosphere rushes in---that's the sucking part. (Indirectly, it is Earth's gravity that creates the pressure, but you could also imagine the Earth is in a big closed box.)

          Intergalactic space is presumably much emptier than any vacuum that we can achieve on earth. When the "empty space" in question is simply surrounded by more empty space, there isn't any sucking of matter. (Pressure is practically zero.)

          It turns out that space itself can contain energy; that is, "empty" is not the same as "nothing." General relativity predicts that there is energy in the curvature of space, which is roughly equivalent to the energy in Newton's gravitational fields. (Not exactly equivalent for strong fields, however.) Also, quantum mechanically, there is always the possibility of a particle or field being present in the empty space. That possibility provides a "zero-point" energy, even when the matter or fields are not there. If we really knew all the possible particles and fields, we could calculate what this would be. There might be particles and fields that we haven't discovered yet, or other additions to quantum mechanics that we haven't discovered yet, which is why we have to look to astronomers to determine the properties of empty space.

          The energy in otherwise empty space is the dark energy. That energy can cause dynamic behavior in the framework of space, causing it to expand and contract.
          • by Anonymous Coward
            Stephen Hawkin, in his book "A Brief History of Time", says (when talking about Black Holes) that there can't be "empty space" because of the Uncertainty Principle, and thus what is known as "empty space" is really particles and antiparticles creating and destroying each other all the time.

            He then goes to say that for each pair of particle-antiparticle, one can be sucked into the Black Hole while the other, failing to be destroyed by it's counterpart, escapes and allows us to detect the black hole.

            He then goes into saying that because an antiparticle would behave exactly the oposite than the particle, what would appear to be a pair being created and destroyed, would really be a particle going forward and backwards in time in a "circular " manner... and we would see it as a particle - antiparticle pair.

            But I'm not and physicist, so I wouldn't know better than what Stephen Hawking wrote... anyone care to elaborate?

            Cheers.
            Me
      • by WatertonMan ( 550706 ) on Tuesday February 11, 2003 @10:46PM (#5285142)
        What is funny is that "dark energy" is also termed "quintessence" or the fifth element. Quintessence was an other term for aether which, as you might recall, was the nebulous stuff in the cosmos prior to modern physics. Funny how things we thought we disproved pop back unexpectedly.

        Of course aether was primarily brought up by Maxwell to explain certain phenomena. It was disproved by the "fact" that the speed of light was a constant in all inertial frames.

        What's interesting is that there is a movement to suggest that perhaps, just perhaps, the speed of light wasn't a constant after all. While I rather doubt that, New Scientist has an interesting interview with the main proponent of that theory, Joao Magueijo. Interview with Joao Magueijo [newscientist.com]

        He has a book partially about this coming out this month called Faster than the Speed of Light [amazon.com]

        I rather doubt Einstein is wrong on this matter, although some of Magueijo's criticisms of superstring theory are often made. Still quite a few people are discussing the issue. Landau, for instance, has a recent paper on the topic. "Charge Conservation and Time-Varying Speed of Light [arxiv.org].

        To tie all this together, here's an interesting paper that ties some of this all together, including "dark energy." "Perfect Fluid Cosmology with Varying Light Speed." [arxiv.org]

        • excuse me for being, well, not exactly the brightest one here, but here goes:

          If the speed of light is constant, then why does it vary as it goes through different things? For example: when light goes through glass, it slows through the glass then speeds back up again.

          And with black holes, the gravity is so intense that not even light can escape.

          It would seem that these two things (the first being the most obvious of all) prove that the speed of light does vary. Or maybe everybody I learned from was full of it.

          Either way, any clarification would help.
          • If the speed of light is constant, then why does it vary as it goes through different things? For example: when light goes through glass, it slows through the glass then speeds back up again.

            You're correct. What's constant for all observers is the speed of light in a vacuum.

        • What is funny is that "dark energy" is also termed "quintessence" or the fifth element

          So, basically, it's Milla Jovovich?

    • Re:huh? (Score:5, Informative)

      by JoeBuck ( 7947 ) on Tuesday February 11, 2003 @08:06PM (#5284321) Homepage

      A baryon is a particle such as a neutron or proton. It's one of the two main classes of ordinary matter particles, the other is the lepton (e.g. an electron or neutrino). Baryons "feel" the strong nuclear force, leptons do not.

      Dark matter refers to exotic forms of matter that are "ordinary" from a gravitational point of view, that isn't made up of baryons or leptons. This stuff either interacts weakly with ordinary matter, or doesn't interact at all (other than via gravity).

      Dark energy has positive energy but negative pressure, so it causes a gravitational repulsion. Einstein's "cosmological constant" one possible example of dark energy. It can be thought of as a property of space.

      • Re:huh? (Score:5, Informative)

        by (void*) ( 113680 ) on Tuesday February 11, 2003 @08:35PM (#5284449)
        In astronomy, "baryons" can also include "leptons", simply because leptons are included in the mass that one measures using a galaxy rotation curve.
        • Re:huh? (Score:3, Interesting)

          Nope. Baryons are the heavy particles made up of three quarks. Leptons are light particles that are themselves fundamental particles. In between are mesons, made of a quark and antiquark.
          • Re:huh? (Score:4, Interesting)

            by adminispheroid ( 554101 ) on Tuesday February 11, 2003 @10:19PM (#5285022)
            You missed the part where he said "in astronomy." In astronomy, a lot of wrong things are true. In this case, when astronomers say "baryons" they mean "baryonic matter" i.e. atoms, molecules, ions, etc. which includes the electrons. Of course, in baryonic matter the electrons make up something like 0.02% of the mass, so it's hardly worth quibbling about.
            • Re:huh? (Score:4, Informative)

              by Peter T Ermit ( 577444 ) on Tuesday February 11, 2003 @11:29PM (#5285331)
              First, he said baryons, not baryonic matter -- you will never hear any astronomer call a lepton a baryon.

              Second, technically, even in astronomy, baryonic matter is only the nuclei -- the leptons are counted separately, though they're unimportant masswise, as you mentioned. Here's why.

              There are several ways of computing the amount of and types of matter in the universe. One of the most important is examining primordial gas clouds and looking at the relative abundances of hydrogen, helium, and lithium and their various isotopes. This tells us about the era of nucleosynthesis -- the time 3 seconds to 3 minutes after the big bang when the temperature and pressure of the universe was enough to induce nuclear fusion. After 3 minutes, this process ended and froze the ratios of primordial elements.

              By looking at those ratios, scientists could figure out the abundance of those nuclei -- the nuclei, not the leptons, which don't affect the ratios at all. From this, they can figure out the density of nuclear matter in the universe, which is related to a quantity known as omega sub b. This number is thought to be about 4.5% from measurements of the elements in those gas clouds -- and MAP confirmed this by a different method. But this baryonic fraction does not have anything to do with the leptonic component of matter... including electrons and neutrinos.

              So, when astronomers say that they have shown that 4.4% of the universe is made up of baryonic matter, they really mean baryons. It just so happens that there are pesky leptons hanging around the baryonic matter, too.

              • Re:huh? (Score:5, Informative)

                by efuseekay ( 138418 ) on Tuesday February 11, 2003 @11:54PM (#5285434)
                nope.

                Astronomy/astophysics pays my bills, and I can tell you that 4.4% of baryons from WMAP really means anything that is known in particle physics as quarks, leptons, blah blah blah.

                A rule of thumb is that 'baryons' in astronomy/astrophysics is anything that is in the standard model (sans the higgs.)But that's not the whole story.

                "baryons" (in the 4.4% of WMAP) is classified as matter that is not "dark". "Non-dark" means it interacts with other stuff and itself beyond just pure gravitation. That includes "radiation", which is stuff that behaves relativistically, and include things like photons, neutrinos,a nd perhaps other relics.

                To summarize, there is no difference between "baryons" and "baryonic matter" in astronomy.

                I will not call a lepton a baryon, but I will definetely lump leptons in when I say 4.4% of ther universe is made out of baryons. it's just a matter of context, and people in the field will udnerstand that.

                Really, astrophysicists are sloppy when it comes to naming stuff. So you have to be careful not to read too much into nomenclature like this, even in the era of "precision cosmology".

                • Astronomy/astophysics pays my bills, and I can tell you that 4.4% of baryons from WMAP really means anything that is known in particle physics as quarks, leptons, blah blah blah.

                  Sorry; I'm afraid you're wrong. Neutrinos, which are leptons, are not in that 4.4%. They constitute an additional 0.5% or so on top of the baryonic fraction.

                  "baryons" (in the 4.4% of WMAP) is classified as matter that is not "dark". "Non-dark" means it interacts with other stuff and itself beyond just pure gravitation. That includes "radiation", which is stuff that behaves relativistically, and include things like photons, neutrinos,a nd perhaps other relics.

                  I can't believe this, because according to your definition, all the leading candidates for exotic dark matter like WIMPs and axions aren't dark. That doesn't make any sense at all. I'm willing to accept that astronomers are sloppy with their nomenclature, but not that sloppy.

                  • you are right that neutrinos get a separate category on their own. That's me being sloppy.

                    On the other hand, I don't think the definition of darkmatter is fine as it stands. If wimps and axions are discovered by terrestrial detectors, then you begin to figure out how to classify them. You can call it detection of new physics (since wimps and axions are beyond S.M. stuff).

                    You hope that dark matter are not really "dark", i.e. you can see it via some interaction with non-dark matter. If you find it, then they are not "dark". In a maximally boring universe, dark matter is just that, dark and completely undetectable except through gravity. Though to prove that DM is really "dark" is almost impossible given the creativity of theorists unless one find a new model of universe which is as good but without appealing to DM.

                    • On the other hand, I don't think the definition of darkmatter is fine as it stands.... You hope that dark matter are not really "dark", i.e. you can see it via some interaction with non-dark matter. If you find it, then they are not "dark".

                      That's true, and your definition is consistent. However I prefer the definition of "dark" as being something that doesn't interact via em radiation, which means I'd have to coin a new word for something that doesn't interact except via gravity... maybe "sterile." But then I'd have to rename the sterile neutrino. *sigh* Maybe your definition is for the best. *grin*

                      In a maximally boring universe, dark matter is just that, dark and completely undetectable except through gravity.

                      Yeah, that would suck. :) But even maximally boring has to be pretty interesting. Not only do you need a new particle and extend the SM that way, you also have to extend it to explain how you can get a matter-antimatter asymmetry without any contribution from the weak sector.

          • Re:huh? (Score:4, Interesting)

            by Captain Nitpick ( 16515 ) on Tuesday February 11, 2003 @10:41PM (#5285116)

            In astronomy, "baryons" can also include "leptons", simply because leptons are included in the mass that one measures using a galaxy rotation curve.

            Nope. Baryons are the heavy particles made up of three quarks. Leptons are light particles that are themselves fundamental particles. In between are mesons, made of a quark and antiquark.

            You've got to remember that the terminology astronomers use is a bit...different. This is much like how they call anything heavier than helium a "metal".

      • ...It is my understanding that space is a co-relative property of energy, not an independent plenum in which things reside. That is to say, without taking into account the relationship between two or more energy peaks there is nothing which can be called "space." Space in this context simply means: spatial relationship, but that relationship is intercontained in the co-relative awareness which we call "energy."

        That makes me one of those cosmologists who takes consciousness as the primary medium from which all else is composed. Although from a materialist standpoint this is difficult to conceive, it is a perfectly valid assumption from which to build. But it proceeds from a subjective experiential validity rather than an "objective" sensual validity. Since I know from experience that I am transcendently conscious I have no trouble trusting my own authority on the matter.

        And frankly it leads to more elegant explanations of phenomena than proceeding from a materialist standpoint, and after all aren't aesthetics the real arbiter of truth?
      • Not quite. There are two types of dark matter. Some is made up of baryons -- it's part of the 4.4%. The rest is not made up of baryons, nor is a significant part of it made up of the leptons we know of. That's "exotic dark matter."
  • Tell that to Columbus.
  • by lingqi ( 577227 ) on Tuesday February 11, 2003 @07:59PM (#5284284) Journal
    Really, now. That just makes the universe sounds sinister. I can just imagine Vader argue with Yoda in Ep.III (cutting out the huffing) "Ahh you see master yoda, the universe is mostly the dark side." Can't they go for a policitally correct / socially sensitive / thoughtful of the children phrase like "cannot-see energy" or "we have no fscking clue where it is energy"?

    otoh, iirc the original background radiation measurements were done using a U2 (not the band, though it would be interesting) flying at some 70k ft, something about only a U2 can fly that steady (without resorting to satelites, anyway).
    • "dark" == not visble and "energy" == not matter

    • I'm going to go ahead and take your comment too seriously. I think the fact that it's called dark energy is just an analogy. Certainly the concept of "dark energy" as a sort of property of "empty space" has been around for quite a while (e.g. Einstein's cosmological constant). But perhaps "dark matter" got more attention in the media (maybe because it's easier to grasp, so to speak). So the phrase "dark matter" was coined first, even though the concept came about later. Then people eventually just started calling the intrinsic energy of space "dark energy" because it seems vaguely similar in concept.
    • by theCat ( 36907 ) on Tuesday February 11, 2003 @08:47PM (#5284519) Journal
      [darkhumor style=kurtvonnegut]
      It turns out some researchers called it God at first but that doesn't look as well in print outside of sacred texts. You know, "God is everywhere, but unevenly distributed and is repulsive, not that anyone would notice or at least they have not. Only we did notice so we're L337 and we're forming our own religion. We hereby declare all other religions apostate and anathema on the strength of our observations."

      We pagans know all about Dark Energy. Heck, we're obsessed with it. Only I'm a little surprised that it's not more than 75% of the known universe. I bet a lot of the Cold dark Matter will turn out to be wanna-be Dark Energy too, just tettering on the edge of going over for the last few billion years.

      The idea that only 4% of the Universe is "normal" really lines up with the notion many witches and Zen masters subscribe to, where 96% of Everything is utter nonsense. But you can still have loads of fun with the other 4% if you lay your hands on a good spell book. Just don't forget to close your sacred circle, and properly call the gates, and sanctify your athame first. Bless us but you don't want to upset the balance of entropy and cause any of that loitering Cold Dark Matter to get any fancy ideas.
      [/darkhumor]
    • Can't they go for a policitally correct / socially sensitive / thoughtful of the children phrase like "cannot-see energy" or "we have no fscking clue where it is energy"?

      How about black energy? Or, always-being-kept-down-by-the-man energy?

  • correction (Score:5, Insightful)

    by zaqattack911 ( 532040 ) on Tuesday February 11, 2003 @08:00PM (#5284291) Journal
    13.7 billion years old, flat, 4.4% baryons,
    95% We don't know.
  • More information (Score:5, Informative)

    by Anonymous Coward on Tuesday February 11, 2003 @08:01PM (#5284295)
    More information can be found at (including a cosmology tutorial):

    http://www.astro.ucla.edu/~wright/cosmolog.htm#New s [ucla.edu]

    This press release was mentioned in a post in the previous slashdot story yesterday.
  • Other links (Score:5, Informative)

    by riptalon ( 595997 ) on Tuesday February 11, 2003 @08:02PM (#5284301)

    Mass media coverage can be found at CNN [cnn.com] and the BBC [bbc.co.uk]. A list of all the MAP papers can be found here [nasa.gov].

  • by MrByte420 ( 554317 ) on Tuesday February 11, 2003 @08:04PM (#5284311) Journal
    You only get 73% of you daily dose of dark matter. That would leave eating bowl after bowl after bowl. Try my new "Extra Dark Total Universe" and get 100% of your Dark Matter in just one bowl!
  • Isn't this (Score:4, Funny)

    by Timesprout ( 579035 ) on Tuesday February 11, 2003 @08:07PM (#5284325)
    4.4% baryons, 22% dark matter and 73% dark energy.

    The recipe for coke ?
  • by The_Rippa ( 181699 ) on Tuesday February 11, 2003 @08:11PM (#5284338)
    13.7 billion years old, flat, 4.4% baryons, 22% dark matter and 73% dark energy

    Except for the age part, that sounds a lot like my ex-girlfriend.

    Happy Valentines Day everybody!
  • by monk ( 1958 ) on Tuesday February 11, 2003 @08:19PM (#5284375) Homepage
    Confused by "Dark Energy," "Vacuum Energy," "Dark Matter," and "Exotic Matter?" Here's a great collection of papers [lbl.gov]. (Mostly from the SNAP project)

  • by Tackhead ( 54550 ) on Tuesday February 11, 2003 @08:21PM (#5284383)
    From the launch press release [nasa.gov]

    "MAP, an Explorer mission, cost about $145 million."

    If I understand correctly...

    Measuring the age of universe, calculating initial proportions of baryonic matter vs. energy, and deriving shape of universe: $145M.

    Shuttle flight to install ISS module: $500M.

    Shuttle flight to watch ants float in zero-G: 7 deaths, $500M for launch, $2.0B for new shuttle.

    Your Congressional District's seat at the trough of Shuttle/ISS pork: "Priceless."

    Now that I've bashed, some constructive criticism - cut NASA in half.

    One half - NAA - I'll call the National Aeronautics Administration. Its job will be pure Aeronautics. Launch vehicles. Rockets. Engines. From pricy Shuttles to half-decent Shuttle-C heavy-lift modifications, to cheap expendables, to funky crewed vehicles like X-33, VentureStar, or DC-X.

    The other half - N(whoops!) let's call it the NSSA - National Space Science Administration - will do science. Build probes. Stick 'em on rockets built by the NAA, or LockMart, Boeing, or Armadillo, and do some frickin' science.

    Under such a scenario, we could have avoided the Shuttle/ISS debacle completely; NAA might have had concerns about losing funding once the last Shuttle was built, and probably would have had a significant incentive to keep asking Congress for funding to build newer, better, cheaper-per-pound launch vehicles.

    Why? Because they'd be under competitive pressure from every other contractor under the sun building launch vehicles to launch NSSA's space probes. Perhaps NSSA would have come to the same mistake NASA did - and decided that we Really Needed a Space Station - but even if that were the case, the design requirements of ISS would have immediately mandated a heavy lift vehicle, wholly unlike the Shuttle.

    In such a scenario, NSSA would have had the choice between building ISS with three FooCorp Big Dumb Booster flights, or 30-40 NAA Shuttle flights.

    Unlike the current NASA monolith, in which both halves exist to feed each other, a separate NSSA would have been loathe to spend its hard-begged budgetbucks to use another government department's (i.e. "NAA's") Shuttle, particularly in the face of cheaper alternatives. (And likewise, NAA, seeing that it had no Shuttle customers, would have been forced to spend its hard-begged budgetbucks building the Shuttle's successor, or find itself on the Congressional chopping block.)

    • Umm.... (Score:2, Informative)

      by Anonymous Coward
      Do you have any idea about how NASA really operates?

      NASA's budget and operations are firmly divided into unmanned and manned areas. Almost none of the unmanned science missions are launched by the Shuttle fleet... most are launched on corporate expendable launch vehicles.

      Science in NASA is almost totally disengaged from launch vehicle & station planning & operations. This is a problem, not a cure.
    • So tell me, if NSSA uses NAA's equipment, does NSSA pay the NAA? In that case, you are simply robbing Peter to pay Paul, and creating 2 Beaurocracies from one.

      That's progress.

  • From the article: Expansion rate (Hubble constant) value: Ho= 71 km/sec/Mpc

    What does the Mpc stand for?
    • Re:Expansion rate? (Score:3, Informative)

      by riptalon ( 595997 )

      Mpc = Mega parsecs, i.e. millions of parsecs, where parsec stands for parallax arcsecond and equals about 3.26 light years.

      • Thanks - so how fast are we expanding away from other stuff in the universe? I understand the 71km/sec part. How does that relate to parsecs? 71km per sec per every 3.26 million light years?
        • Re:Expansion rate? (Score:2, Informative)

          by efuseekay ( 138418 )
          The further away the object is from us, the greater the velocity it seems to be expanding away from us. So H=71km/s /Mpc means that for every Mpc the objet is away from us, it is flying away from us at the velocity of 71 km/s.

    • Re:Expansion rate? (Score:3, Informative)

      by Gruturo ( 141223 )
      What does the Mpc stand for?

      Megaparsec (a parsec is 3.26 light years, or 3.08*10^16 meters).

      Basically, it means that an object 1 megaparsec away from you is moving away by 71km/second (since the whole universe is expanding like a 4-dimensional balloon, all points are moving away from all other points, and this speed increases with their relative distances)

  • by TWX_the_Linux_Zealot ( 227666 ) on Tuesday February 11, 2003 @08:35PM (#5284450) Journal
    "MAP ... to study variations in the cosmic microwave background, to much greater accuracy than the COBE satellite"

    And their web page is better too. My satellite can beat up your satellite!
  • So... (Score:4, Insightful)

    by CrazyDuke ( 529195 ) on Tuesday February 11, 2003 @08:38PM (#5284472)
    I would interpret this to mean the following:
    (no profit recycling please)

    1. 4.4 of the energy is stored in atomic nucleuses and some exotic particles.
    2. 22% is stored in matter we can't directly observe, but can observe its effects on surrounding objects.
    3. 0.6% is electrons and other small mass particles, measurable energy, etc.

    Guess: Up to 73% of the original mechanical energy of the big bang is still in the form of mechanical energy (kenetic energy + potential energy).
    Guess#2: Or 73% of the original ME of the big bang has been lost to entropy.

    Aside Question: Given 2 objects of the same mass and potential energy at rest. Raise one of the objects to a higher potential. Does that not raise its mass relative to the first since the mass is its total energy/c^2? I remember NASA was puzzled by the Voyager probes not making it as far out as they expected them to be by now. Perhaps because they gained mass relative to us? Also, if 2 objects accelarate relative to each other and thier KE increases (relitively), does that not increase the mass, and their for the attraction between the two objects?

    Bah, time to RTFA.
  • by cachorro ( 576097 ) on Tuesday February 11, 2003 @08:39PM (#5284480)
    The universe is flat.

    If you travel far enough through the universe, you will fall off the edge (if the dark energy doesn't get you first).
  • "...13.7 billion years old, flat, 4.4% baryons, 22% dark matter and 73% dark energy."

    This just sings to me, I think this could be the new "all your base are belong to us." or something of that nature. Quite nice.
  • Another question. (Score:2, Insightful)

    by CrazyDuke ( 529195 )
    Would not a sphere of unimaginable size have a surface that would essentially flat?

    For millenia, most of the world thought the earth was flat and people could fall off the edge. Could this just be an extension?
    • Would not a sphere of unimaginable size have a surface that would essentially flat?

      That's why the cosmologists have had such a hard time figuring out what the universe is shaped like. It's so flat and so big that it is very hard to tell.

      However, a flat universe, and an unimaginably colossal (hyper-)spherical universe would cause slightly different phenomena to be observed. This new data has allowed the cosmologists to make their predictions with a better chance of being right.

  • by Ponderoid ( 311576 ) on Tuesday February 11, 2003 @08:52PM (#5284559)
    Can anyone tell me what's so special about the Sun-Earth L2 point that made it attractive to put the probe there? I couldn't find any reference on that site about why that spot was chosen.

    At first I thought that it might need permanent shade from the sun, but I checked and found that the Earth's umbra doesn't extend that far out.

    Unlike L4 or L5, the L2 position is a meta-stable point, requiring frequent correction to remain in place. There had to be a very good reason to choose it. The site has quite a bit of info about what exactly that spot is (nothing I didn't know already) and how the probe got there, but not a word why.
    • by djcinsb ( 169909 ) on Tuesday February 11, 2003 @09:31PM (#5284748) Homepage
      L2 is nice for several reasons. The instrument on MAP needs to be kept cold. Sitting at L2, the spacecraft can keep the instrument pointing away from the Sun, and still measuring data, without ever needing to worry about interference from the Earth or Moon, and there is this nice big dish (the solar array) shielding the instrumentation from direct sunlight. In addition, NASA has lots of experience with spacecraft at the collinear Lagrange points (L1 and L2), so the orbits and communications are very well understood there. And L2 is far enough away from the Earth-Moon system to avoid complicated orbit perturbations, but close enough for relatively easy communications (that is, the radio doesn't have to be too big).

      Hope that helps!
  • Since time has been proven to continue into infinity, why do we state that the universe 'started' 13.7 billion years ago? What was happening 13.8 billion years ago in the space we currently occupy? Surely the Big Bang was a result of some other cosmic event, since time could stretch infinitely into the past as well as the future. The universe couldn't have been born without being first conceived...
    • Nothing of the sort (Score:3, Informative)

      by rufusdufus ( 450462 )
      Time has not been proven to continue into infinity. Go read 'A Brief History of Time' for a good laymens introduction to cosmology.

      Space and time are concepts deeply intertwined with energy and matter; they is not distinct from them. Thus, there is no 'before' the universe began, there is no time there, there is no there there either.
    • Since time has been proven to continue into infinity, why do we state that the universe 'started' 13.7 billion years ago? What was happening 13.8 billion years ago in the space we currently occupy? Surely the Big Bang was a result of some other cosmic event, since time could stretch infinitely into the past as well as the future.

      Space and time are linked together. Without space, there is no time. There was nothing before the big bang because there was no "before." The big bang was an explosion of matter and spacetime.

      The universe couldn't have been born without being first conceived...

      Quantum physics says that something can indeed be created out nothing; so yes... the current theory is that the universe popped out of nothing some 13 billion years ago. Of course 13 billion years isn't exactly the age since time is relative, so the universe as a whole doesn't actually have one "age," but that's another matter altogether.
      • Quantum physics says that something can indeed be created out nothing

        Well, getting more philosophical than physicists like, technically there isn't nothing. There is space and there are the laws of Quantum Mechanics. Quantum Mechanics still rests on a fairly Newtonian view of space/time. That's one of the many reasons it is such a bear to unify with General Relativity which has a conception of space much more in tune with Leibniz' view of space.

        Also the "big bang" is extrapolating back well beyond Planck time to where/when we really don't have physics to describe. So we can say that a classical view of the history of the universe (i.e. arrived at with relativity) suggests a big bang. We could say it was something from nothing, as the true big bang doesn't even have space. (Thus invalidating what I said about Newtonian space) However we really don't know what is going on that early and even if there was a big bang of the sort we think of.

        This is one of those places where our cosmological speculation outstrips our physical laws. If we adopt the inflationary bubble universes, then perhaps our "big bang" really arose from a sufficiently flat space/time the vacuum fluctuations created our universe. Who knows? While it is fun to speculate, I think a lot of discussion of the "origin of the universe" ought to be presented clearly as speculation. It is moving a little too far beyond established theory for my tastes.

    • "Since time has been proven to continue into infinity"

      Uh? It has? When?


      Do not let English and common sense lead you into confusion. Go read a cosmology primer; asking what was 'before' the big bang is like asking what the big bang happened in. Time and space didn't exist an infinite time ago... which is hard to think about... so we _can_ say that things 'started' 13.7 billion years ago.

    • Ah, no. According to current theory, asking what was happening before the big bang is like asking what is north of the north pole (Hawking quote IIRC). The big bang was the creation of time. How can anything exist before the big bang? The whole idea of "before the big bang" doesn't even make sense.
  • by Anonymous Coward
    This isn't science! Wait, oh shit, it is.

    Let the naysayers be damned. I don't think there's a 'real' scientist out there who believes that this is the ultimate truth as to what the universe is composed of.

    However, it's a good start at figuring out just what exactly is going on.

    Where would we be now if some nutcase back in the day didn't say, "Hmm, well, what if the world was actually round?" and start working on craziness that would ensure.

    Where would we be if some looney wouldn't have said, "You know, math would be a lot easier if zero exisisted."?

    Giving random figures about things you aren't certain about isn't science. It's an important *part* of science. It's a launch vehicle for experimentation and theorizing.
  • by Dr. Mu ( 603661 ) on Tuesday February 11, 2003 @09:15PM (#5284671)
    When I first saw the COBE map [lbl.gov] awhile back, a little part of me said, "Well, that's nice, but such subtle data from a single platform isn't much to go on." But now, the new image [nasa.gov] certainly does seem to correlate well with it. The similarities are graphically obvious, and the fact that those data were obtained independently from COBE's is what makes this announcement most significant.
  • Does this research: New Light on Dark Matter [psc.edu], count as a prediction of these observations?

  • by msheppard ( 150231 ) on Wednesday February 12, 2003 @01:25AM (#5285768) Homepage Journal
    The map (really big version too) is today's Astronomy Picture of the Day. [nasa.gov] Along with another good description of the findings with the typical excellent APOD links.

    Go Apod!
    M@
  • Executive summary (Score:2, Insightful)

    by jfmiller ( 119037 )
    I'd just like to mention that I really appriceate it when the author of an article on science sums it if for us. I often have only 5 min to brouse the headlines and information like this is most welcome.

    JFMILLER

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