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Deepest Optical Image Of The Universe To Date 24

Posted by michael from the asa-eight-million dept.
fenimor writes "The deepest optical view of the universe, obtained by Hubble Space Telescope, may turn out to be some of the earliest star-forming galaxies. The telescope has looked 95 percent of the way back to the beginning of time, to glimpse whether the hottest stars in these early galaxies may have provided enough radiation to 'cool' the universe after the big bang."
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Deepest Optical Image Of The Universe To Date More

Deepest Optical Image Of The Universe To Date

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  • A question (Score:5, Insightful)

    by T.Hobbes ( 101603 ) on Friday September 24, 2004 @11:11AM (#10340705)
    I was thinking about these photos, and came upon was seems to me to be a paradox. OK, so the Hubble takes this ultra-deep image of a point in space. This is said to be an image of the universe X billion years ago, and Y billion years after the big bang. All well and good.

    Now, so far as I know, intersteller distances are measured by the light year; Alpha Centuri is ~4 light years away, etc.

    I extrapolate from this that this ultra-deep and ultra-old image of the universe is both the _oldest_ and the _most distant_ image yet taken.

    The problem is this: You can point the hubble in any direction, and get an equally old image. Further, if you take a deep enough image, you can (theoretically) take an image of the Big Bang itself (or X million years after it, whatever).

    The paradox to me, is that this means the Big Bang can be conceptualized as a the outer edge of a sphere that surrounds us. You can, with the telescope, image in any direction in all three dimensions, and your limit wrt distance in any of those directions is the big bang. So the big bang is the edge.

    Now, this seems absurd to me, so I obviously got something wrong somewhere. Does anyone know what I got wrong?

    • Where I said "The paradox to me, is that this means the Big Bang can be conceptualized as a the outer edge of a sphere that surrounds us. You can, with the telescope, image in any direction in all three dimensions, and your limit wrt distance in any of those directions is the big bang. So the big bang is the edge."

      I should have just said "You can conceptualize the universe as a sphere, with the Earth (or Hubble) as the center, and the Big Bang as the outer edge. No matter what direction you travel in, the

      • Re:a correction (Score:3, Informative)

        by TMB ( 70166 )
        There's a big difference between those two statements! The first one is quite correct (well, except for issues relating to the opacity of the early universe - if you did it with a neutrino telescope or gravitational radiation telescope, you could theoretically see back to almost the Big Bang). The second isn't - if you travel, you're going forward in time, whereas when you look at light from far away, you are seeing back in time.

        [TMB]
      • The matter that makes up the Earth, you and I, the sun, our Galaxy, was all part of the explosion we call the Big Bang. So you don't have to look far away, and deep into the past to see something that was once part of the Big Bang. Everything you look at, including the nose on your face, was once part of the Big Bang. So, the Big Bang is not the edge of the Universe.

        • what was, is

          and what is, won't be

          because you have seen it into being
        • > The matter that makes up the Earth, you and I, the
          > sun, our Galaxy, was all part of the explosion we
          > call the Big Bang.

          Well, yes, and no. "The matter" was indeed formed during the big bang (well, shortly after it, during nucleosynthesis). But only Hydrogen, Helium and a little Lithium. The rest of the actual atoms you and I are made of were formed in stellar cores as a result of fusion (for elements lighter than and including Iron) or in stellar supernovae (for all elements heavier than Iron).

    • I think you're right (Score:2, Interesting)

      by Anonymous Coward
      The Big Bang obviously no longer exists at a single point in space. The residual image is at the outermost edge of the universe. What's the paradox?

    • Seems correct, but no paradox .. (Score:5, Informative)

      by RedLaggedTeut ( 216304 ) on Friday September 24, 2004 @11:25AM (#10340824) Homepage Journal
      I think what you say is basically correct:
      If you look out as far is possible, which should be either the point in time where the universal "balloon" expanded at the speed of light, or maybe so far that the Hubble constant times the distance is the speed of light, then you get to see the big bang.

      Most of it is called the cosmic microwave background.

      There are two reasons why there isn't as much of a paradox:
      One is that spacetime might look like this: Space is 3D, but consider that it as 2D, then the universe would look like a balloon that gets inflated: every point on the balloon seems to be at the center of the explosion called big bang.

      The second reason is that it gets harder to see the big bang itself, because Einsteins relativity theory predicts really big shifts in wavelength for stuff that moves away near the speed of light - so any electromagnetic waves and light from the big bang would be far below infrared and low in energy. And incrementally so as you get to look closer to the big bang.

    • Re:A question (Score:5, Informative)

      by zrail ( 50290 ) on Friday September 24, 2004 @11:27AM (#10340846)
      Technically, the furthest you can look back is about 300,000 years after the big bang, because thats approximately the point in time when the universe cooled down enough to become transparent. Before that, the universe basically consisted of a really hot soup of plasma.

      Try this page [wikipedia.org] for some background information on cosmology and cosmic background radiation [wikipedia.org].

    • Re:A question (Score:5, Informative)

      by Bootsy Collins ( 549938 ) on Friday September 24, 2004 @11:52AM (#10341218)

      Now, so far as I know, intersteller distances are measured by the light year; Alpha Centuri is ~4 light years away, etc.

      Well, actually, parsecs (and kiloparsecs and megaparsecs) are what tend to be used, for mainly traditional reasons. But it's a straightforward unit conversion.

      The problem is this: You can point the hubble in any direction, and get an equally old image. Further, if you take a deep enough image, you can (theoretically) take an image of the Big Bang itself (or X million years after it, whatever).

      In practical fact, you can't see back to the Big Bang, for a number of reasons. The first is that until a few hundred thousand years after the putative Big Bang, the Universe was opaque to radiation. Photons were simply too unlikely to pass much of any distance through the Universe without scattering off a charged particle of some sort. After that point, the Universe became transparent to photons. Consequently, that's as far back as you can see -- with photons, anyway. But you're right that you can see this change of state in the Universe (the so-called "surface of last scattering") in any direction you look, and in fact that's what astrophysicists are looking at when they map the cosmic microwave background radiation.

      The other thing that prevents you from seeing all the way back to the Big Bang is that as the Universe expands, light is redshifted (basically, its wavelengths are stretched out with the expansion). That's why we have to look in the infrared band for these distant galaxies, and that's why the light we observe from the surface of last scattering is in the microwave band. Light emitted at times closer and closer to the putative Big Bang is redshifted by larger and larger degrees, approaching infinite redshifting at the Big Bang itself (when the scale factor of the Universe, describing the expansion of space relative to today, is 0). So even if the surface of last scattering wasn't there, there'd be a practical limit to just how far back one could see, based on just how low-energy (long-wavelength) of photons one could detect and interpret.

      The paradox to me, is that this means the Big Bang can be conceptualized as a the outer edge of a sphere that surrounds us. You can, with the telescope, image in any direction in all three dimensions, and your limit wrt distance in any of those directions is the big bang. So the big bang is the edge.

      The Big Bang occurred everywhere. It occurred where you're sitting, where I'm sitting, and where Zaphod is sitting.

      Imagine some event -- say, the change of state that I described above, referred to as "decoupling", when the Universe became effectively transparent to photons, where before that it was opaque. This happened basically everywhere at once -- as the Universe expanded, densities and temperatures dropped until the scattering probabilities fell low enough. This happened everywhere, including right where you and I are now. But the photons that were around here then are long-gone now. They've been flying off in different directions since then. Similarly, the photons that were 10 light years away aren't around us either: the time they've had to fly, times the speed of light, is a long way from here. If you think about it, the photons you're going to see are ones that started out on a shell that's centered on us, with a radius equal to the distance light could travel in the time since decoupling (it's a little more complicated than that because of the expansion, but that's the basic idea). At any later time, from 1 second to 1 billion years later, that shell will be larger.

      So that's why we see a given time in the history of the Universe as a shell around us. It's not because these things (like the surface of last scattering, or the Big Bang itself) really are shells, but simply because that's all we can see. The photons that started at points interior to that shell aren't anywhere near us now; they've had enough time to propagate further than the distance between us and their starting points. The photons that started at points outside that shell haven't had enough time to reach us yet.

      Hope this clears things up some . . .

    • Re:A question (Score:3, Insightful)

      by NonSequor ( 230139 )
      The universe isn't neccessarily Euclidean. There are all sorts of funky ways it can loop back on itself.

    • The problem is this: You can point the hubble in any direction, and get an equally old image. Further, if you take a deep enough image, you can (theoretically) take an image of the Big Bang itself (or X million years after it, whatever).

      Nope, we can only see back 14-15 Billion years. What's interesting is that our "horizon" is limited because the universe is expanding uniformly. IE, space is appearing between us and Alpha Centauri as much (per unit distance) as it is appearing between us and other g

  • 95% Really? (Score:3, Funny)

    by redog ( 574983 ) on Friday September 24, 2004 @11:40AM (#10341032) Homepage Journal
    "The telescope has looked 95 percent of the way back to the beginning of time,""

    Then it can tell me where I put those keys a couple days ago?

    Right?

    Please!

  • So did anybody see (Score:3, Funny)

    by Marxist Hacker 42 ( 638312 ) * <seebert42@gmail.com> on Friday September 24, 2004 @01:17PM (#10342456) Homepage Journal
    The Big Bang Burger Barn? (obRef, Restaurant at the End of the Universe).

  • Actually, you are correct... (Score:5, Interesting)

    by j_cavera ( 758777 ) on Friday September 24, 2004 @01:28PM (#10342581)
    This is not a paradox, rather just a way of looking at it that is different than what you are used to. The universe at the beginning of time, existed as a point (more or less) that expanded (somehow) into what we see today. As you look out into the universe, you also look back in time. The farther back you go, the smaller the universe was.

    By logic, if you could look all the way back to the big bang itself, you would see a point of light. And this is where your percieved paradox occurs. But this is actually the correct way of thinking about it, because time = distance. So where does that point lie? Everywhere, at a distance of 15 billion (give or take) light-years from us! So no matter where you look, you see a "part of that point" from 15 billion years ago.

    OK, this is an oversimplification as the universe was opaque for some time after the big bang, but you get the idea. Here's a potentially useful (though not perfectly accurate) analogy. Go inside a large spherical room with white walls. Put a bright light bulb at the center (big-bang). The walls are evenly illuminated because no matter which way you look, your line of sight intersects with some of the rays of the bulb, that seem to come to you from all around you.

    In fact, if you had a good enough detector, you could determine the shape of the bulb's filament by irregularities in the light from the walls. This is what the cosmic background explorer (COBE) missions are about.

    BTW, yes IAAP (I am a physicist).
    • Hi,
      Sorry for the offtopicc, but all seems quiet and since YAAP and seem to know about the stuff I thought I'd just ask :)

      I am wondering if, today, we have some real "expectations" about the universe course from big bang (if big bang there was) to now and if yes, if we have commonly believed aswers (or prefered models about this) about the following assumptions that I make myself when trying to imagine the whole picture:

      - The universe is roughly a 4D sphere, and we belong to its boundary (or the univ
      • We should see the mirror effect of lightsources that "were coming from some point at some time, and which appear from the oposite direction in the exact same (inversed) way at a precise later time. Those Timings and directions being influenced by our observer's relative position to an original source and "where was 'its' equator" ('its' because we all have one) then and now.

        I think there is active research into this, ie, we should be able to see an image of our own galaxy out there somewhere, and it is b
      • OK, that's a lot to process but here goes: > The universe is roughly a 4D sphere... Actually from the COBE experiments and the large scale structure of the universe (galactic superclusters and all), the universe is very close to flat, hyperspatially speaking. As of yet, no one knows how this came to be or what it means. > ...sphere radius was nearing zero and is since then expanding True enough, if you substitute "shape" for "sphere". It's almost meaningless to discuss the shape of the singulari

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