Topical Astrophysics Post And Open Thread



Jaybird is Birdmojo on Xbox Live and Jaybirdmojo on Playstation's network. He's been playing consoles since the Atari 2600 and it was Zork that taught him how to touch-type. If you've got a song for Wednesday, a commercial for Saturday, a recommendation for Tuesday, an essay for Monday, or, heck, just a handful a questions, fire off an email to

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41 Responses

  1. Avatar Herb says:

    Ha! That was good, man.Report

  2. Avatar BlaiseP says:

    Bravo, Mr. Jaybird! Whiman:

    WHEN I heard the learn’d astronomer;
    When the proofs, the figures, were ranged in columns before me;
    When I was shown the charts and the diagrams, to add, divide, and measure them;
    When I, sitting, heard the astronomer, where he lectured with much applause in the lecture-room,
    How soon, unaccountable, I became tired and sick; 5
    Till rising and gliding out, I wander’d off by myself,
    In the mystical moist night-air, and from time to time,
    Look’d up in perfect silence at the stars.

    Unlike Whitman, unaccountable, grown tired and sick, people like you and me and Neil DeGrasse Tyson find awe in the sky. To consider our planet, huddled up for warmth from a nice long-lived star, protective Jupiter hoovering up stray comets, our moon which gives us rotational axis stability, we have it pretty good. Life could evolve here because we had warmth and stability and the tides to stir our seas. Our presence near the edge of our galaxy gives us a pretty fair view of deep space, especially the southern hemisphere, where we can now see the galactic core in the infrared through its shroud of dust, great stars hurtling around the black hole at its core.

    Like children, bravely peering over the edge of a ravine into the canyon below, sending great telescopes into space and building more on the tops of the desert mountains of Chile, we look not only out into space but back into time. The sky seems dark because the universe is expanding. Mr. Hubble’s galaxies act as lenses for yet more distant light.

    The thing which bakes my noodle is the notion of time and light. The most ancient energy (of which light is only a tiny fraction) which reaches us today is the background microwave Penzias and Wilson detected, an artifact of the universe’s creation. But all we can detect of the universe is a great circle defined by the radius of a photon travelling since the moment of creation in our direction. What lies beyond that great circle, beyond which we cannot see?Report

  3. Avatar Matty says:

    dark matter, unlike aether, is, in fact, testable not only in theory but in practice

    The luminiferous aether was perfectly testable, it just failed every test…

    Like your mom.Report

  4. Avatar Stillwater says:

    Nice JB. HMD to all the moms, all the people with moms, and all the space moms, too!

    Re: space and stuff, I find the whole thing confusing, in fact so confusing I’m sure most of my beliefs are false (which might explain why it’s so effing confusing). Start with the second law, move on to an infinitely old universe, if so, then why hasn’t the universe already turned black? Either the universe isn’t infinitely old or the second law is wrong. But people love their second law, so the way out of the conundrum is that the universe *had a beginning*, which is a weird conclusion from a philosphical pov since there had to be something before the beginning, etcetc. But then we find evidence that the beginning we thought was out there waiting to explain all our problems isn’t the *right* beginning, and we’re not sure what could even *be* the right beginning. So maybe the universe is older than we thought. Like a lot older. Maybe even infinitely old? Then what do we make of the second law?

    And why in the hell is there something rather than nothing? Isn’t that question more like a koan than it is empirically answerable? Confusions…Report

    • Avatar BlaiseP in reply to Stillwater says:

      The issue of Oldness falls down the rabbit hole when you come to terms with the passage of time as an outworking of the universe itself.Report

      • Avatar Stillwater in reply to BlaiseP says:

        I get that part. I just think it’s wrong. Supposing a big bang, the theory seems to be that there is pre-temporal goo existing conceptually outside of space (because it created space) and conceptually outside of time (because it created time) and within in this spaceless timeless goo a trigger caused … something … which resulted in an eruption of creating spacetime.

        That seems incoherent to me.Report

        • Avatar BlaiseP in reply to Stillwater says:

          It does seem somehow Wrong, doesn’t it? My son seems to believe there’s something inherently wrong with it, too. There are Brane Theories running around which attempt to describe the Trigger you describe. He’s got some ideas about String Theory as well, saying anything that complicated has to be wrong. It’s fascinating and slightly depressing to have a child who’s smarter than you’ll ever be, heh.

          Here’s hoping we manage to get the Webb Telescope launched. Yes, it’s gone way over budget. I don’t care and neither should anyone else. The answers it will provide cannot be obtained any other way.

          These are the days of miracle and wonder
          This is the long distance call
          The way the camera follows us in slo-mo
          The way we look to us all
          The way we look to a distant constellation
          That’s dying in a corner of the sky
          These are the days of miracle and wonder
          And don’t cry baby, don’t cry

        • Avatar Patrick Cahalan in reply to Stillwater says:

          Everything comes from something that isn’t it.Report

  5. Avatar Mike Schilling says:

    There’s also Olbers’ paradox, which argues that the sky should be completely bright, and is hand-waved away by the Big-Bang-caused expanding universe. And all of this, in the standard model at least, depends on the existence of the Higgs boson, without which matter has no mass.

    Not even your Mom.Report

    • Avatar wardsmith in reply to Mike Schilling says:

      Guess who’s link didn’t make it this time? 😉Report

        • Avatar BlaiseP in reply to Mike Schilling says:

          Olber’s Paradox is not so hard to un-paradoxify. When the Hubble Space Telescope took its now-famous picture of the Deep Field, what was once used as a reference “black spot” in the immortal words from 2001 A Space Odyssey — “it’s full of stars”.

          Power varies as the inverse square of distance. Though Olber’s Paradox lets us point to an arbitrary point in sky and say “there’s a star there”, that star might be an awfully long way away, the sort of star which took Hubble Space Telescope 11 days just to image its galaxy. It’s not really a paradox at all.Report

          • Avatar Mike Schilling in reply to BlaiseP says:

            Assume an infinite universe with a uniform distribution of stars.

            Now divide the universe into concentric shells centered at the Earth. The first has radius N, the second radius 2N, then radius 3N, etc. That is,. shell K has radius KN. Now, the volume of each shell is (at the limit) proportional to K^2, (*) and the average distance from the earth is (at the limit) proportional to K, so by the inverse square law, each shell should be equally bright. There are an infinite number of shells, so, day or night, the sky should be infinitely bright.

            There’s nothing wrong with the reasoning, so the assumptions must be false.

            * To be precise, it’s 4/3 * Pi * (3KN^2 -3KN + 1)Report

            • Avatar BlaiseP in reply to Mike Schilling says:

              Doesn’t work in this universe. The distribution of stars is decidedly not uniform. The naked eye can only make out three galaxies. The Large Magellanic Cloud has about the brightness of a 100 watt light bulb seen from 46 kilometers away, 0.021 W/(M^2). Spitzer Space Telescope gives us a trillion stars in the Andromeda Galaxy alone. The light of a trillion stars, blazing away for two point six million years and the light is just now reaching us, a hundred watt light bulb seen from a 151 kilometer distance.

              The nearest star is 1.29 parsecs away, the Andromeda Galaxy somewhat less than 800,000 parsecs away.

              And that’s just the close galaxies. Making out galactic distance requires a Type Ia supernova in the target galaxy.Report

              • Avatar Fnord in reply to BlaiseP says:

                Even if the galaxies, or even galactic superclusters, were homogeneously arranged out to infinity, you’d still have an infinitely bright sky. Mr. Schilling’s math holds regardless, even if the light of a given shell is sufficiently dim that it’s invisible to the naked eye.

                The reason the sky is not infinitely comes down to the fact that
                1) the observable universe is not infinite in size, and
                2) Hubble’s law means that the universe, as observed, is not homogeneous.Report

              • Avatar BlaiseP in reply to Fnord says:

                No you wouldn’t. The universe is finite but unbounded. Big difference. Yes, a few photons reach us from every star. That doesn’t mean the universe becomes infinitely bright. That would presume every photon was directed at us. Mr. Schilling is a fine human being but his math is bunk.Report

              • Avatar Fnord in reply to BlaiseP says:

                If a few photons reach us from an infinite number of stars, then that’s an infinite number of photons.

                The inverse square law was known in 1823. Heinrich Olbers was not an idiot. The inverse square law is not sufficient to deal with Olbers’ paradox in an infinite, eternal, static, and large-scale homogeneous universe.Report

              • Avatar BlaiseP in reply to Fnord says:

                Naturally, I’d argue the universe is finite, time-bound, dynamic and startlingly inhomogeneous. Nor are there an infinite number of anythings in the universe, more Cantor and less of this finger-wiggling.

                The fact is, Olbers’ math was dead wrong and easily proven to be so. Anyone with an incident light meter can demonstrate why.Report

              • Avatar Mike Schilling in reply to Fnord says:

                Fnord is entirely correct. The math is fine, and amounts to a proof that the universe is not infinite, eternal, static, and large-scale homogeneous.Report

              • Avatar BlaiseP in reply to Fnord says:

                The math is beyond wretched. I have already furnished the data. My advice: purchase or rent an incident light meter, hie thee to the nearest sundries store for some graph paper and record your readings at one-foot intervals from a light bulb.Report

              • Avatar Fnord in reply to Fnord says:

                Your so-called data is non-sequitur. I know about the inverse square law, Mr. Schilling knows about the inverse square law, and Olbers knew about the inverse square law. Name dropping Cantor isn’t going to do anything for you since Cantor is required for neither the formulation nor the resolution of Olbers paradox. The paradox merely requires an elementary understanding of converging and diverging series. The resolution involves no new math, merely noting that the assumption do not hold. Which was, in fact, Olbers’ point in formulating the paradox in the first place, to postulate a finite observable universe.Report

              • Avatar Stillwater in reply to Fnord says:

                Why couldn’t someone resolve Olber’s paradox simply by saying the following; if the universe contains infinitely many stars, and if the universe also contains an infinite amount of other matter which blocks starlight, then at any point P in the universe will only a small fraction of total starlight will be observable?Report

              • Avatar Mike Schilling in reply to Fnord says:

                A few reasons:

                1. A fraction of infinity is still infinity.
                2. The stuff blocking the starlight is receiving an unbounded amount of energy, and will eventually start radiating it off (or simply boil away).Report

            • Just out of curiosity, especially given the choice of picture to accompany this article, how is the presence of dust clouds that occlude a portion of the sky accounted for? The brightness of a distant star is not just a function of how far it is from me, but also what’s in between me and it.Report

              • Avatar DBrown in reply to Michael Cain says:

                The solution to Olber’s paradox is simple – the universe can be infinite (no requirement that it is but assume it is since if it works for infinite, it of course works for a very, very, very large but finite universe, too.)

                Since light has a finite speed AND the universe had a beginning (about 14. 3 billon years ago) we can see light ONLY from stars that have been radiating light (photons) that has had time to travel to us.

                In reality, it is farther that we see since ‘space’ has been stretched by cosmic expansion – so in reality, we can ‘see’ light from stars out to about 31 billion light years. This means the sky has a very finite number o stars even if the universe is infinite. So the sky is nearly black (of course some scattered light covers all areas of the sky.)Report

              • Avatar Stillwater in reply to DBrown says:

                In one sense, Olber’s paradox isn’t a paradox at all. It’s actually a refutation, no? It says that three things commonly believed about the universe – that it’s infinite, static and eternal – can’t all be true.Report

              • Avatar MikeSchilling in reply to Stillwater says:

                Exactly. It’s what’s called an indirect proof: if, given a set of premisses, you can validly conclude a falsehood, at least one of the premisses must be false.Report

              • Avatar DBrown in reply to Michael Cain says:

                Most of space is nearly a perfect vacuum – only near stars or around some groups of stars are gas clouds that form these bright objects but from millions and even billions of light years away, these clouds are tiny specks and really account for little compared to the vast size of a galaxy; that in turn, becomes a tiny, tiny object to us from those huge distances. Of course, some gas exists around galaxies but due to the vast volume, the average numbers of atoms is just about one atom per cubic centimeter – compared to air (6 * 10 to the 23 power!), this is still almost a perfect vacuum and even for billons of lightyears would be a trivial amount of material and not block any significant amount of light from a star that far away.Report

  6. Avatar Miss Mary says:

    Love the picture, JB! Is it the Horsehead Nebula in Orion?Report

  7. Avatar Diablo says:

    This is a common misconception based on the assumption that space is truly empty. Yes compared to say the density of the atmosphere, space appears very empty, but it isn’t. There are massive clouds of hot gas and dust particles that are insanely massive. These clouds end up blocking a lot of our view of the universe. This link has some pics of what the center of the Milky Way looks like under different instruments….

    As you can see, depending on the instruments used, the what we can observe actually is very different than what we normally see, primarily due to cosmic dust blocking our line of sight.

    The really crazy stuff is when astronomers are able to use the gravity of a closer stellar body to bend the light around it, to not only see behind it, but improve the view, similar to using binoculars…only they are using stars and galaxies.

    The only class I have ever dropped was a physics class dealing with the evolution of stellar bodies as I could not get my head around the mathematics involved. I don’t know how these folks study this stuff and not just blow out their brains at the enormity and scale involved.Report

  8. Avatar Procopius says:

    Love this topic. I’ve been stuck reading economics for a couple of years but this used to be one of my lives too. If I understand it correctly, Buddhist cosmology says that, yes, the Universe (Samsara) has no beginning. That implies that it’s infinitely old, I think. The cosmology also says that it’s cyclical. The specific numbers that were given at various times don’t fit very well with current theories but that’s OK because it’s irrelevant, it has nothing to do with extinguishing suffering, which is the only thing the Buddha taught. I have always found this idea emotionally satisfying, and I don’t want to spend time learning the math and science to form an informed opinion on whether it’s true or not. From general reading, I gather that the most recent consensus is that there is not enough mass in the universt to cause it to reach a limit and start contracting, to which I can only say, “Fine, but there’s still so much we don’t know.” So my preferred model is that somehow, out of the heat death universe, a new beginning arises and we start getting ready for the next Buddha to be born. There may or may not be a creator god; she’s not necessary. And love the Second Law as I might, I’ll give it up if I can have my cycles.Report

  9. Avatar Pan says:

    Try looking at this from a different direction
    Just because everything so far has been made of bits and pieces ” particles”
    Dosen’t mean all thing we will ever encounter as students of life , are , or will beReport