Earth was in the crosshairs

By Phil Plait | September 10, 2008 11:29 am

On March 19, 2008, the Earth was caught full-on in the beam of nature’s deadliest beast, a gamma-ray burst.

Swift’s view of GRB 080319b
Swift’s view of GRB 080319B. Courtesy Swift team/Penn State University/NASA.

Lucky for us, the GRB was far away– far, far away: 7.5 billion light years distant, literally more than halfway across the visible Universe.

Had we been much, much closer, like a thousand light years away, the energy from the beam would have torn our atmosphere away, boiled our oceans, and irradiated the planet with a million times the lethal dose of high-energy gamma and X-rays.

Gamma-ray bursts (GRBs) are scary, scary, scary.

But it wasn’t that close; it was a million times farther away than the lethal distance (in fact, all GRBs are really far away, and so pose little real danger to us here on Earth). All we saw was a flash of light — actually, a flash of gamma rays, detected by NASA’s remarkable Swift satellite, designed to do this very task. But what a flash! Even from that terrible distance, the amount of light the GRB gave off made it visible, briefly, to the naked eye!

Artist’s impression of a GRB
Artist’s impression of a GRB. Click for a way cool animation. Courtesy NASA.

A GRB is born in the fury of an exploding massive star, when its core collapses into a black hole. A vast amount of energy is released, more than the Sun’s entire lifetime’s output. A hellish mix of forces focuses, squeezes this exploding energy and matter into beams, extremely narrow cones of emission, cosmic blowtorches which march across space. If you are too close, and in the path of a beam, well, saying "you’re toast" doesn’t quite cover it. But if the beam misses you, you don’t get the gigantic burst of light; the energy drops of very rapidly if the aim of the GRB is off. Even a miss by a fraction of a degree is enough to change its apparent brightness hugely.

Scientists making models of GRBs had an idea that this narrow, intense beam is inside a wider, mushier beam of energy. It’s easier to get hit by by the wider beam (like you don’t have to aim a shotgun as carefully as you do a rifle), and so the idea is that what we see from almost all detected GRBs is this wide beam. Actually being in the path of the narrow beam would be very rare.

And that’s what makes GRB 080319B (the second GRB seen on March 19, 2008), so remarkable: it was aimed squarely at us, and we were bathed by light from the narrow beam. We were looking right down the monster’s throat. The beam was incredibly tight; only about 0.4 degrees wide (take a look at a protractor to get an idea of how skinny this is). Had the beam been aimed just a scosh off, just a tad, the GRB would have appeared far, far dimmer. We still would have seen it, but it would have looked like just another GRB, and not the single most luminous event ever witnessed by humans.

Probably all GRBs have this narrow beam, but they miss us, so we don’t see them. And because the beam is so narrow, scientists say that this sort of thing would happen once a decade or so. Good thing we had Swift running at the time! Swift was able to detect the burst, then rapidly (within seconds) send the news to observatories all over (and above) the planet, so that they could instantly follow up with their own observations. This allowed astronomers to detect the burst at a wide range of wavelengths (radio, infrared, optical, ultraviolet, X-ray and gamma ray), which is critical: it gives us insight into how the beams are formed. That in turn tells us about how the black hole formed, how the star exploded, what sorts of material were involved, and their physical characteristics.

All of this tells us more about the Universe, which is good.

But it also tells us about gamma-ray bursts. And there is just something about them, something terrifying about the energy, the power, the raw fury of them, that fascinates me. They really aren’t a threat to us — we think they can only come from great distance — but they still represent nature at its fiercest. Sometimes the pursuit of science may seem cold and emotionless, but that is far, far from truth. And like GRBs, the closer you get to the truth, the more powerful, the more energetic, and the more passionate science gets.

And may I add, I have a whole chapter about these beasts in my upcoming book, Death from the Skies!, which is available for pre-order on amazon.com.

CATEGORIZED UNDER: Astronomy, DeathfromtheSkies!

Comments (134)

  1. Quiet Desperation

    I thought I felt something on that day.

    If we get hit by enough of these, will we all turn into Hulks when we get angry?

  2. Well, now I HAVE TO buy your book. I love this stuff, and I love pointing out how remote the possibility of this is, EVEN though there are a myriad of doomsday predictors clinging to this particular event.

    Missed the previous blog entry on WR 104. Great reading! There goes my day of trying to be productive!

  3. inertially guided

    7.5 BILLION Light-Years distant, and it was a NAKED-EYE object?!!!!? Okay, my Amazo-Meter just pegged.

    Tom

  4. Todd W.

    Phil,

    What would happen if it was a “glancing blow”, so to speak? I.e., it the atmosphere of a planet just barely got nicked by the GRB?

  5. GRB 080319B (the second GRB seen on March 19, 2008)

    Oh no! It’s the “Y2K fiasco” all over again! :-)

  6. Chris A.

    So my first thought was: At 7.5 Gly, how wide was the beam? In other words, we got “beamed,” but how much of our local universe did too?

    By my calculation, the 0.4 degree beam was over 50 Mly wide when it hit us. So, unless we were right on the edge of the beam, our entire local group of galaxies (MW, Andromeda, and their respective entourages) saw the show. (Hell, if we were on the edge, the other edge could almost reach to the Virgo Cluster!) Admittedly, I’m assuming Euclidean (flat) spacetime here; the real calculation (with varying spacetime curvature along the beam’s 7.5 Gly world line) is beyond my skills, but I think my approximation puts us in the correct ball park.

  7. Cheyenne

    Cool post. Your previous one on W104 that you linked to- kind of scary….but incredibly interesting. I hope it decides to play it cool and not go kaboom on us.

  8. kuhnigget

    Hey doctor Phil (sorry), I have a question regarding this subject.

    Because these things are so far away in space, I presume that means they are also far away in time. So is it safe to say that 7.5 billion years ago or so, the universe was a much more dangerous place than it is now, much less friendly (or indifferent) toward life?

    I guess what I’m asking is, does this sort of thing factor in to the Drake Equation and other attempts to estimate the probability of life throughout the universe? Seems like having your atmosphere stripped off and your planet bathed with lethal radiation might be something of a bummer if you’re a wee little blob of protoplasm or something.

  9. As a recent convert to “Palinism” I take exception to the use of the term “Naked” eye! How dare you suggest that our eyes go uncovered in public! Next I suppose you’ll be advocating naked eye or*ies in the streets! You’ll see, when Dear Sarah gets elected, she’ll put a stop to you ebil science types advocating this type of behavior.

  10. phunk

    kugnigget: for sure it was a more dangerous place, and there were also a lot less of the elements heavier than helium at the time, so there are many reasons life would be more rare back then.

  11. Sili

    How does one determine the distance to a GRB?

    What is the redshift at 7*10^9 LY (I hate ‘billion’)?

    Is it conceivable that a GRB could be distant, yet powerful enough that we could detect it as X-rays?

  12. His_Steveness

    So THIS is how the world’s going to end.

    Nice.

  13. alfaniner

    I guess it’s better to learn about this sort of thing after the fact, than before. I mean, considering all the unjustified fear-mongering the LHC activation created, something like this would certainly validate being concerned.

  14. ioresult

    Chris A, I had the same idea, but let’s try to go a little further.

    If the beam was 50Mly wide and the naked eye could see it… keeping in mind the average nightgazer’s dilated pupil is around 7mm wide, imagine the sheer power in that beam!

  15. tacitus

    I think people get a kick out of being scared of things like this — gamma-ray bursts and LHC activation — call it the “roller coaster” factor or something. To all intents and purposes, you know you are safe, but you still get a thrill out of believing for a moment that you could really be in danger.

    Sells books, though, of that I am sure and BA would not have it any other way (at the moment :) )

  16. BA said: “On March 19, 2008, the Earth was caught full-on in the beam of nature’s deadliest beast, a gamma-ray burst”
    You should have met my god-daughter when she was two. I tell you, I survived nature’s deadliest beast!

  17. Old Geezer

    Please help me understand something. The Swift contacted everybody else and told them to look over there! Assuming they weren’t already looking over there, how long did this phenom last so they could turn around and get a look-see?

  18. Neill Raper

    GRB’s and Supernovae bother me because, unlike asteroid impacts, having populations on Mars or The Moon won’t save us. On the bright side, if we ever get hit by a Gamma Ray burst we will never know it. Kind of like sitting on a nuke, well more like sitting on a stupidly large number of nukes.

  19. Gosh, I remember when that hit the wire the next day. So cool! Unfortunately, it’s not known if anyone actually SAW the thing, although the robotic optical telescopes scooped it up.

    Wonderful explanation and imagery.

  20. Cmajor7

    But… but…

    Phil keeps saying the GRBs are all far, far away from us? Why is that? Is there something special about the earth that GRB’s happen far away? Obviously, that’s not the case. What prevents a GRB from happening at the lethal distance? Is it that there are no candidate stars nearby? And why is that? I wish he’d be clearer about this sometimes.

  21. Mike R.

    Phil, I absolutely LOVE it when you do posts like this.

  22. Don Snow

    Great article and images.

    Really great images.

    OK, 1Kly is cataclysmic dose of GRB. And, 7.5Gly is a safe shot. What I want to know, at what distance does a GRB leave some life on Earth, but fritzes all the electronics? Survivors stripped of technology. Would it also damage brains?

    Just my morbid curiousity.

  23. Of course the origin Phil cites for these gamma-ray bursts hardly even merits the title “speculation”; look up “WAG” in the Urban Dictionary. To insist they can’t happen in our galaxy or in nearby clusters amounts to whistling in the graveyard. According to Phil’s description, and assuming the absolute brightness reported, at a million light years the radiation dose would still be lethal, and at ten million light years civilization would collapse (we’re near enough to collapse as it is).

    The distance estimate is little better supported than the origin myth. If it was closer than estimated, its absolute brightness would be less; at 750Mly, it would be 100 times dimmer (if “dim” can be used in this context) than claimed, but still a respectable energy release, able to denude the earth from 10 light years away, and collapse civilization from as far away as the middle of our galaxy.

  24. Aramael

    Events like this make me … darn, it’s a family blog, so I can’t say, but this is just amazingly amazing. 7.5 billion light years. The energy involved.

    Cmajor7: this sort of thing can only be produced by an enormous star collapsing into a black hole, and there are no candidates anywhere near us. And remember, it happened 7.5 billion years ago — this sort of explosion is more common in the, ahem, adolescent universe. If you know what I mean. And I think you do.

    Hey, astronomer people, I want to send my young niece and nephew (9 and 7) a telescope so that they can share my wonder. How hard is it to locate Mars, Jupiter, Saturn and so forth? The room for error seems pretty small, so I’d like to include instructions for finding them.

    And you know, then they could teach me (I live in one of the most densely populated parts of the world, so buying a telescope for my niblings who have access to a farm is about the only way I’ll see the planets live).

    (Hey, the word “live” could be taken in two senses. I’m foolishly tickled by that)

  25. Jeeves

    Stupid question, but I have to ask: how do we know the beam was only 0.4 degrees wide?

  26. Andy

    Awesome post, Phil. You just convinced me to get your new book when it comes out :)

  27. Anne

    In what sense is it the most luminous single event ever observed? I mean, on the one hand you can look at the Big Bang itself through the CMB; even redshifted, this supplied most of the photons currently in the universe, so it’s hard to argue anything else is more luminous. Even if you leave that aside, this GRB was certainly bright, but when you say “luminosity”, that suggests to me that you’re counting the total amount of radiation emitted – which isn’t (IIRC) all that much more than an ordinary supernova. GRBs are astonishing largely because they’re so highly beamed, but that’s not “luminosity” per se… You can calculate a pseudoluminosity by pretending that the brightness we see was uniformly spread over the whole sphere; in this sense I’m willing to believe that this GRB was the highest ever observed (apart from the Big Bang).

    As for why all the GRBs we see are so far away, it’s because they’re so rare but so bright. There are only something like five events per day in the entire observable universe, and most aren’t pointed at us. They’re roughly uniformly distributed through space, so the chance that one would occur in the small volume that’s within a few kiloparsecs of us is pretty slim.

  28. Josephine

    If Earth was in the crosshairs of this narrow burst, does that mean nothing was in the way of the beam while it travelled through the universe to eventually reach us?

    It is a narrow-minded question, I am aware, but as I am no astronomer I felt compelled to ask a qyestion I could not answer myself. For, if nothing was inbetween the burst, that would be mind-boggling and incredibly fascinating.

    If anyone answers this question I am much grateful in advance.

  29. @Anne: Hooray for a dose of informed skepticism, so ironically rare around here. However, I think it’s fair to cite brightness per unit solid angle. Jeeves asks a relevant question, in that context, but if the angle were much more or less than cited the event might be even more impressive, albeit for different reasons. Of course we don’t really know the correct order of magnitude of the distance. The big bang hardly counts, as it’s still speculative. :-)

  30. Naomi

    Eta Carinae’s about to go pop soon (that’s some time in the next million-odd years) – that’s thought to be a GRB producer, right? Let’s hope the axis isn’t pointed at us, it’s only about 8000 LY away ^_^

  31. American Voyager

    The energy here is too incredible to fathom. It blows my mind! I love reading posts like this

  32. @Josephine: The beam certainly illuminated trillions of objects while it made its way to us. At issue is whether any were exactly between us and the source. Even if it were shadowed, one would expect the beam to encounter a bit of gravitational-lensing, resulting in scattering, which would fill in holes. So I don’t think we can be sure there was nothing in the way. Anyway, if so, it wouldn’t be surprising; space is profoundly empty.

  33. Mike

    What if Halton Arp is right and this GRB is NOT at cosmic distances. it would explain a whole lot….

  34. tacitus

    Ugh, Mike, Halton Arp is flat out wrong re: cosmic distances. I am hoping you missed out a “tongue in cheek” emoticon.

  35. Gary Ansorge

    NAthan: AS far as calculating the GRBs distance, we have some pretty good yardsticks. Ever hear of Cephied variables?

    Someone already beat me to the punch about the early universe having a LOT more really big stars to form GRBs. After childhood, readily available H2 is already incorporated in RBSs (really big stars) and they blow up young.Not near as many today as then.

    But keep on asking questions. It’s fun seeing where you’re coming form,,,

    Gary 7

  36. I am glad that everyone is so interested in this remarkable event – herewith are some answers to some of your questions:

    1) The redshift was 0.937 which corresponds (using the most popular cosmology) to a distance of 7.5 billion light-years. This means that the explosion really happened 7.5 billion years ago.

    2) The Universe was probably much more dangerous back then, as more massive stars were forming in great abundance. Since massive stars live shorter lives, which end in supernovae, there were more dramatic explosions back then. We don’t have any really massive stars in our local neighborhood – say within 100 light years or so – which is very lucky for us!

    3) It is true that Swift tells everyone (well, at least everyone who is tuned into the Gamma-ray Coordinates Network alerts) to look at bursts, usually within one minute. However, the telescopes which caught the burst at the very beginning were looking at the part of the sky where they knew Swift would be looking (Swift’s observing plans are also available), and these telescopes have wide fields of view. Pi of the Sky and the TORTORA camera on the REM telescope both have fields of view which are a good match for Swift’s Burst Alert Telescope. So both of these have great chances to catch the burst at the very beginning. Pi of the Sky was first, and caught the entire thing, and TORTORA was very close to the beginning of the burst as well.

    4) The calculation that the primary beam is only 0.4 degrees wide comes from an analysis of the “jet-break” in the X-ray light curve. As a jet moves out from the central source, the light spreads out and the intensity drops dramatically. Models of how the slope of the light curve changes are used to calculate the width of the jet.

    5) As for the damage that GRBs can do to the Earth and the chances of that, I will defer to the Bad Astronomer’s upcoming book as I don’t want to steal his thunder! :-)

  37. Ian

    So you SAY they are natural. I say they are the echos of ruinous weapons of a long dead civilization and what we see is the aftermath of a terrible war, a long time ago in a galaxy far, far away.

    Ahem. No? Damn.

  38. Jose

    “Hooray for a dose of informed skepticism, so ironically rare around here.”

    Is this a dig at your own uninformed skepticism? If so, I agree.

  39. Anne

    @Nathan Myers: Whether you still want to call the Big Bang hypothetical or not in this era of quantitative cosmology, there’s no debate about the existence or brightness of the cosmic microwave background. So even if you prefer to write down “unknown” for the event that produced the CMB, that event was still extremely luminous…

  40. I don’t know we can count the Big Bang as one of the most luminous events witnessed by humans because we’re really only seeing the afterglow of the BB and not the actual event. From my completely uninformed non scientific perspective GRBs count as some of the most luminous events in human history because we are seeing the actual event with the naked eye. It is bright and we can see it now. It seems that simple I guess.

  41. @Anne: The CMB need not be the result of a single event.

    @Gary Ansorge: I presume you are pointing out that the general Hubble relation is calibrated against Cepheid variable stars. We know that there are exceptions to that relation (e.g. the QSO in front of nearby opaque galaxy NGC 7319), and I don’t know whether GRB 080319B was such an exception.

  42. Don Snow

    @[b]Nathan Myers[/b]

    Thank you, for your prompt and informative reply. I always appreciate an option other than total cataclysmic destruction of our planets’s atmosphere, oceans, flora and fauna.

  43. @Don: Now that I know your preference, I will do my best to control my own outbursts.

  44. Davidlpf

    NATHAN explain the CMB or are we going to get another ad hom or ad ingoratiam.

  45. Davidlpf

    Come is beyond your abilities th=o explain or understand or is the big bang theory contradicts something sacrd to you.

  46. Davidlpf

    that was supose to be

    Nathan, come on Nathat is it beyond your abilities to explain or understand or does the big bang theory contradicts something sacred to you.

  47. Ah, CMB = Cosmic Microwave Background radiation. The only stuff I can find that says CMB can be explained by anything other than the BB is from self proclaimed geniuses who have “disproved the Big Bang” or revised general relativity. Plasma cosmology pops up a fair bit so I too am looking forward to seeing an explanation.

  48. Davidlpf

    Either give an explaination or admit it you do not what you are talking about , and saying it is beyond our understanding is not an answer.
    Ad ignoratiam is an arguemnet out of ignorance, basically I can not understand the current so it most be wrong.
    Ad hom arguement by personal attacks another little logical falacy you use.

  49. Gonzo

    It’s easier to get hit by by the wider beam

    Typo.

    Also, do you have the definitive GRB post somewhere. I am highly confused here. How is it this explosion happens? We don’t know, I assume. It’s just really boggling my mind right now BA. How can it have so much energy? What gives? Help me, I am going to go insane thinking about this. Off to read everything I can find on GRBs.

  50. RL

    If a GRB was within a thousand light years of Earth, how long would it take to notice that things were happening? Would it be instananeous or would it take time?

  51. @ Gonzo

    Click on my name and the link will lead you to a very detailed article in Wikipedia on Gamma-ray bursts. The article has additional links such as Gamma-ray burst progenitors.

  52. Matt

    So, we know what would happen if it hit a planet at 1,000 light years, what would happen if it hit a planet closer than that? Say if it was in orbit around a planet. A nice peaceful planet that had no weapons. a planet that is not far too remote to make an effective demonstration of the power of this fully operational…uhm… Gamma Ray Burst?

    Also how does the power of a Gamma Ray Burst compare to the power of the Force?

  53. Lynnc, thanks for troubling to come over and comment. I really appreciate it when the scientists involved in these projects explain the detail.

  54. Steradian

    Lessee. 0.4 degrees beamwidth means that each GRB (assuming twin beams) illuminates
    ~7 ×10-5 of the sky around it with the core flux. Anthropically speaking, that seems to place some upper limit on the numbers and ranges of GRBs over the past couple of billion years, doesn’t it?

  55. Ken

    My theory is, whenever an intelligent civilization activates its first Large Hadron Collider it causes a gamma-ray burst.

    This is why we haven’t detected any extra-terrestrial civilizations.

  56. Jose

    @Nathan Myers

    I figured out your five step program.

    1. Make a vague, unsubstantiated, and insulting criticism of something you don’t understand.
    2. Try and get another commenter on your side with a compliment about how awesome they are compared to the Phil.
    3. When challenged, squirm a bit, and then admit you don’t know what you’re talking about.
    4. Regain the upper hand by pointing out that at least you know you don’t know what you’re talking about, unlike others.
    5. Congratulate yourself on a job well done.

    I think you’re somewhere between steps 3 and 4 right now. Let me know if I left anything out.

  57. yorkjj

    Given the age of the earth (4.5 billion years give or take) and the distance to this GRB (7-8 billion light years) I think it is safe to say it was not “aimed” at us. When this happened, we were not even here; at all. Given the travel of objects in space, we would not have been where the blast was pointed that long ago. Small point to make given that if we had been closer it could have been fatal, but I think it’s important to point out it was probably not personal or deliberate. Just a thought to keep it in perspective.

  58. Yorkjj writes, “Given the age of the earth (4.5 billion years give or take) and the distance to this GRB (7-8 billion light years) I think it is safe to say it was not “aimed” at us. When this happened, we were not even here; at all.”

    Well of COURSE it wasn’t “aimed” at us in any deliberate way. But the fact remains that GRBs occur all the time, some closer, some farther away. And it’s conceivable that at some point in the future our fair planet may drift innocently INTO the crosshairs without knowing what is coming our way. It’s just a matter of being in the wrong place at the wrong time. If a large asteroid or comet was coming our way, we might possibly have the time and the resolve to deflect it … but a gamma ray burst would arrive without any warning whatsoever.

    Phil speculates about a GRB arriving from only a thousand light years away. According to Wikipedia (so shoot me!), “Scientists suspect that if a GRB were to occur near our solar system, and one of the beams were to hit Earth, it could cause mass extinctions all over the planet. The GRB would have to be less than 3,000 light years away to pose a danger. A consensus seems to have been reached that damage by a gamma ray burst would be very limited because of its very short duration, and the fact that it would only cover half the Earth, the other half being in its shadow. A sufficiently close gamma ray burst would however, result in serious damage to the atmosphere, shutting down communications (due to electro-magnetic disturbances), perhaps instantly wiping out half the ozone layer, and causing nitrogen-oxygen recombination, thereby generating acidic nitrogen oxides. These effects could diffuse across to the other side of the Earth, severely diminish the global food supply, and result in long-term climate and atmospheric changes and a mass extinction, reducing the global population to perhaps 10% of what it can now support. The damage from a gamma ray burst would probably be significantly greater than a supernova at the same distance.”

  59. Todd W.

    Of course the GRB was aimed at us. Like any good hunter, they aimed ahead of where we were 7.5B years ago so that it would hit us when it finally covered the distance. ;)

  60. @Don Snow: I apologize for having relied on Phil’s numbers. I should know better.

    @Todd W: You don’t “aim” a shotgun, you “point”‘ it. (Sorry, no cite.) Pointing at where we would be 7.5By later (or whenever) would be “leading the target”, if we had existed at the time. Evidently, though, we just blundered obliviously into its path. We should learn some range safety rules or stay the **** off the firing range. Pull!

    @Jose: If you’re hoping somebody not a sock puppet will call you “awesome”, even compared to Phil, I predict a long wait.

    @shane: Has anybody demonstrated that the entire universe must be perfectly transparent to microwaves? ‘Coz I know of some bits that aren’t.

  61. Davidlpf

    Nathan why is there is a CMB in the first point.

  62. Davidlpf

    Come on you nearly had a day to go FETCH an answer where is it.

  63. Davidlpf

    oh and your response to shane is a strawman maening you did not answer the question but tried to change the subject another logical falacy.
    Oh and the answer Jose is Ad Hom another use of that falacy so is the answer to dons answer.
    The answer to todd is another strawman.

  64. Jose

    If you’re hoping somebody not a sock puppet will call you “awesome”, even compared to Phil, I predict a long wait.

    Yes Nathan. That’s exactly what I’m hoping for. You saw right through me. Oh God, will someone please tell me how awesome I am? Don’t make me take a sock puppet to myself. I heard that gives you hairy palms.

    But I’m also waiting for you back up some of your ridicules assertions instead of just making snide little insults. I predict an even longer wait.

  65. @Davidlpf: What? (You’re mumbling.)

  66. Davidlpf

    Just pointing out flaws in your arguement, either answer the question or admit you do know why there is a CMB. Are the words to complicated for you do we have make more simplistic for you. If there is something blocks microwaves what do you call it, why do you not see it. I wonder what you call something you do not know what it is exactly or can see it, hmm. Go fetch the answer.

  67. Al

    “The single most luminous event ever witnessed by humans”
    Phil I think you mean “identified in modern recorded history”. We don’t know that someone didn’t see a GRB 50% closer a few hundred or 50,000 years ago, but it was only a few people and no one believed them or they didn’t know how to write !

  68. DeiRenDopa

    @Nathan Myers: We know that there are exceptions to that relation (e.g. the QSO in front of nearby opaque galaxy NGC 7319)

    We do?!? May I ask how I know that? or how you know that?

    And do you have any other ‘exceptions’ you’d like to share?

  69. @DeiRenDopa: Does that one cause you discomfort?

  70. DeiRenDopa

    @Nathan: not at all; I’ve seen it mentioned on several crackpot websites, as “proof” that “quasars” are local, so I am surprised to see you mention it (I checked some of your comments elsewhere, you don’t seem like the kind of person who repeats such nonsense without having researched the claims yourself).

    So, may I ask how (you know that) I know that? or how you know that?

    And do you have any other ‘expectations’ you’d like to share?

  71. kuhnigget

    @ Jose:

    You’re awesome!!!!

  72. DeiRenDopa

    @Sili: How does one determine the distance to a GRB?
    A: by applying the Hubble relationship to its observed redshift

    @Sili: What is the redshift at 7*10^9 LY (I hate ‘billion’)?
    A: 0.937 (would you like a reference?)

    @Sili: Is it conceivable that a GRB could be distant, yet powerful enough that we could detect it as X-rays?
    A: yes, but a) many GRBs are detected, almost simultaneously (by SWIFT, for example) in the x-ray band; b) GRBs emit a great deal of energy over a very wide range of frequencies (so a GRB would be ‘visible’ in the gamma-ray band out to a very large redshift; c) the high energy (say, 100 GeV and above) spectrum of GRBs is poorly observed (GLAST/Fermi will change that)

  73. DeiRenDopa

    @Old Geezer: how long did this phenom last so they could turn around and get a look-see?
    A: some ‘observatories’ (hard to find a word that covers everything from specialist satellites to general purpose ground-based optical telescopes to radio facilities) were still watching it over a week later. However, the quickest off the mark, other than SWIFT, got ‘images’ within a second. For many years now there’s been a global network for disseminating ‘alerts’, and there are facilities which can respond to these (electronic) alerts within a second or a few … would you like some references?

  74. DeiRenDopa

    @Nathan Myers: Of course the origin Phil cites for these gamma-ray bursts hardly even merits the title “speculation”[…] The distance estimate is little better supported than the origin myth

    Oh? And may one enquire what your reasons for these astonishing assertions are?

  75. DeiRenDopa

    @Aramael: Hey, astronomer people, I want to send my young niece and nephew (9 and 7) a telescope so that they can share my wonder. How hard is it to locate Mars, Jupiter, Saturn and so forth?

    A: it’s very easy, provided they are ‘up’ (and not set) on the clear night you choose to look for them. There are many resources on the web for finding objects like these in the sky from a particular location on a particular night … unfortunately I can’t include a URL, but Sky and Telescope’s This Week’s sky at a glance should be easy enough to find (to take just one example)

  76. DeiRenDopa

    @Jeeves: how do we know the beam was only 0.4 degrees wide?

    A: it’s an interpretation of the way the intensity declined with time … if the source is a (relativistic) jet, then the curve of intensity vs time we observe here on Earth will have a very characteristic shape, and from the ‘jet break’ an estimate of the opening angle may be calculated. If you’d like a more detailed answer, I’d be happy to refer you to a website where you could get such an answer.

  77. DeiRenDopa

    @Josephine: does that mean nothing was in the way of the beam while it travelled through the universe to eventually reach us?

    A: essentially yes; at least nothing which could absorb sufficient gamma rays, x-rays, UV, light, IR, etc to dim the GRB appreciably.

    Of course, there is (was) plenty of matter, both ordinary (‘baryonic’) and dark, on the path, but it is (was) very tenuous … some few gas atoms or ions per cubic metre, a few specks of dust, etc.

    Until the beam encountered the Earth’s atmosphere, which absorbed everything except the (visual) light, some IR, and the microwaves and radio waves; that’s why SWIFT (and GLAST/Fermi, and …) are satellites, above the atmosphere.

  78. Davidlpf

    Nathan you have not answered anybodies questions things uncomfortable for you.

  79. @DeiRenDopa: I read the 2005 AstrophysJ paper. Either the QSO is there or it’s not. The “crackpot” label is not conducive to honest discussion.

    @Davidlpf: While you sit in the basement watching the site, some of us do things. (Quick, fetch the stick!)

  80. DeiRenDopa

    @Nathan: I read the 2005 AstrophysJ paper. Either the QSO is there or it’s not.

    I too have read “The Discovery of a High-Redshift X-Ray-Emitting QSO Very Close to the Nucleus of NGC 7319″ (The Astrophysical Journal, Volume 620, Issue 1, pp. 88-94). It seems you know more than the authors of the paper, who make no claims concerning NGC 7319 being “opaque” (in that paper).

    May I enquire as to the basis of your assertion that NGC 7319 is opaque?

    And may I ask how (you know that) I know that (“the QSO in front of nearby opaque galaxy NGC 7319″)? or how you know that?

    And do you have any other ‘exceptions’ you’d like to share? (“We know that there are exceptions to that relation”)

    @Nathan: While you sit in the basement watching the site, some of us do things.

    You mean like go read the 2005 ApJ, and check to see if your wild claim is consistent with it?

  81. @DeiRenDopa: No, I don’t mean that. Do you answer for Davidlpf now?

  82. Davidlpf

    No he does not, but you seem have enough time to troll the interent and insult people while you do not have any evidence in what you are talking about. If you really knew what you were talking about you have reply to the questions that were aske you and not your prescreened questions. Now with over forty eight hours to provide the answers you still have not answered a single one so this leaves only one conclusion you do not know what you are talking about. Oh what is that I hear coming another personal attack. Oh by the wat my room is not in basement and most of the time I am at work at a call center with limited internet access and understaffed because we have couple of workers out due to illness, So you have complete internet access and all the time and the world so either put or shut up.

  83. DeiRenDopa

    @NathaN: “We know that there are exceptions to that relation (e.g. the QSO in front of nearby opaque galaxy NGC 7319).”

    May I enquire as to the basis of your assertion that NGC 7319 is opaque?

    How do you know that “the QSO [is] in front of nearby opaque galaxy NGC 7319″?

    Do you have any other ‘exceptions’ you’d like to share? (”We know that there are exceptions to [the Hubble] relation”)

    Would you care to say a few words, Nathan Myers, on what you regard the criteria for assessing whether some piece of astronomical research is scientific or not are?

    Back to plasmas, gas, fluid dynamics, etc.

    The Sun is a big ball of plasma; to what extent, Nathan, is any study of the Sun unscientific if it does not explicitly and directly incorporate plasma fluid dynamics?

    Specifically, are all the papers on the Sun and neutrino physics unscientific for not having explicitly incorporated PFD?

    @Nathan: “I will mention that the “gas” could not “slam” (presuming that’s what’s really going on at all) if it were not ionized; it would just pass right through, because it’s what in the lab we would call a “hard vacuum”, and gas particles barely interact unless they actually collide.”

    OK, I’ll bite; what’s the mean free path of a gas particle (atom or molecule) in the ISM (interstellar medium)? Just an order of magnitude estimate will do thanks.

  84. Davidlpf

    oh Nathan todays thought for the day Extrordinary claims requre extraordinary evidence that was from a very famous scienctist nameed Carl Sagan.

  85. DeiRenDopa

    Nathan said: “I read the 2005 AstrophysJ paper [on a QSO very close to the nucleus of NGC 7319].”

    Nathan earlier said: “We know that there are exceptions to [the Hubble] relation (e.g. the QSO in front of nearby opaque galaxy NGC 7319).”

    Nathan is on record, in his comments on other blogs by Phil Plait, as ripping shreds off astronomers who do not explicitly use PFD (plasma fluid dynamics) to explain their observations, and who use “gas” instead of “plasma” when describing the ISM (interstellar medium) or IGM (intergalactic medium).

    Here’s a curious fact that anyone can verify for themself: P. Galianni, E. Burbidge, G Burbidge, H. Arp, V. Junkkarinen, and S. Zibetti, the authors of that 2005 ApJ paper Natha cites, use the word “plasma” exactly once in their paper … and that one use is a quote from another paper!

    It gets worse.

    The word “gas” is used 27 times, and in almost all cases the context is clear that “ionised gas” is what they mean.

    It gets even worse.

    The paper contains several mentions of physical processes involving the “gas”, from mere hints (e.g. “interacting”) to something stronger (e.g. “the passage of the QSO through the material of the galaxy has produced a dynamical disturbance as well as a radiative excitation”).

    Not a single mention of PFD!

    Clearly Nathan Myers must slam P. Galianni, E. Burbidge, G Burbidge, H. Arp, V. Junkkarinen, and S. Zibetti with the same venomous language as he hurled at Phil Plait so many times, right?

    And clearly a paper that so baldly and blatantly ignores PFD and whose authors refuse to even use the word “plasma” cannot possibly be regarded as reliable, can it?

  86. Davidlpf

    Ouch that just have hurt, not only does the only paper ho posts mentions plasma only once it mentions what was that gas 27 times more times. Let me see using insults not providing evidence, using termology only to make people he is right let me see that is 3 signs for anti science. The silence is speaking volumes of how little he understands. Now Nathan come on if you want to prove that you know what you are talking about give as some evidence, or are you just a one trick pony.

  87. @DeiRenDopa: You must be aware that papers that appear in ApJ follow ApJ’s own terminological conventions, enforced by ApJ referees. To pretend otherwise is to seek to mislead readers here. Why lie if you have anything real to offer?

  88. Davidlpf

    NAthan is all that all have to say is well they say gas because the editors made say it was gas, how weak.

  89. Davidlpf

    Nathan if you want us to take you seriously you have to give evidence which you have not. It is up to peove your theory we do not have prove it does not, so therefore your charges against people here a false and not proven.

  90. DeiRenDopa

    Nathan said: “You must be aware that papers that appear in ApJ follow ApJ’s own terminological conventions, enforced by ApJ referees. To pretend otherwise is to seek to mislead readers here. Why lie if you have anything real to offer?”

    I did a very quick search, and in no time at all I found several papers, published in ApJ, with the word “plasma” in their titles, for example “The Plasma Structure of the Cygnus Loop from the Northeastern Rim to the Southwestern Rim”, “Generation of a Fireball in AGN Hot Plasmas”, “Magnetohydrodynamic Shocks in Nonequatorial Plasma Flows around a Black Hole”, and “The Relativistic Filamentation Instability in Magnetized Plasmas”.

    I guess the authors of those papers didn’t get the memo from the ApJ editors, and neither did their referees.

    As for PFD, well, this gem, published in ApJ in 2006, deserves to have its abstract quoted here: “The Transition to Incompressibility from Compressible Magnetohydroynamic Turbulence”

    Abstract: “On the basis of three-dimensional time-dependent numerical simulations, we find that compressible magnetohydrodynamic fluids describing super-Alfvénic, supersonic, and strongly magnetized space and laboratory plasmas decay progressively to a state of near-incompressibility, characterized by a subsonic turbulent Mach number. This transition is mediated dynamically by disparate spectral energy dissipation rates in compressible magnetosonic and shear Alfvénic modes. Dissipation leads to super-Alfvénic turbulent motions decaying to a sub-Alfvénic regime that couples weakly with (magneto-) acoustic cascades. Consequently, the supersonic plasma motion dissipates into highly subsonic motion and density fluctuations experience a passive convection.”

    So, with this objective evidence before us, may I ask how you came to the conclusion that “papers that appear in ApJ follow ApJ’s own terminological conventions, enforced by ApJ referees”, in regard to the use of “gas” where “plasma” is clearly what you would have used?

    Oh, and FYI, the paper quoted, the one with the word “plasma” in it? It was published in 1981, in AJ! (the Astronomical Journal)

  91. DeiRenDopa

    Nathan said: “You must be aware that papers that appear in ApJ follow ApJ’s own terminological conventions, enforced by ApJ referees. To pretend otherwise is to seek to mislead readers here. Why lie if you have anything real to offer?”

    I did a quick search, and in only just a bit more than no time found several papers published by “Arp, H” in the last decade, in peer-reviewed journals other than ApJ.

    Taking one at random (“A possible x-ray jet from the starburst galaxy NGC 6217″, with W. Pietsch as co-author; journal is Astronomy & Astrophysics), I found:
    * one use of the word “plasma”
    * one use of the word “gas”, in a context where it is very clearly referring to a plasma (“Also in Cen A there is no particular optical object associated with the X-ray jet although there are some outer gaseous filaments which lie along the projected track”)!

    So here is some concrete, objective evidence consistent with the hypothesis that H. Arp has used the word “gas” to refer to a state of matter that Nathan believes must (always?) be called “plasma”.

    Further, the Discussion section of this paper gives no hint (that I could see) of any application of PFD, or even that it might have any relevance in terms of explaining the observations reported earlier in the paper … but perhaps Nathan Myers can?

    May we, the readers, expect that Nathan will hurl the sort of fierce barbs he is on record as slamming Phil Plait with against Halton Arp too?

  92. @DeiRenDopa: I see you’re having fun, but the point remains: language use in journals follows peculiar rules that don’t apply here.

  93. DeiRenDopa

    @Nathan: Who wrote this, I wonder? No prize for guessing correctly.

    “Therefore, when we look through a telescope — most especially a radio or x-ray telescope (although one doesn’t, exactly) — and see evidence of trillions of tons of plasma moving in what are easily determined to be multi-light-year spanning magnetic fields (which even Phil admits), we have no honest choice but to deduce correspondingly large electric currents, and correspondingly great masses of ions to carry them, and must conclude that plasma fluid dynamics have an essential role in explaining what we see. When (as Phil claims, probably honestly) astronomers laugh at any of their own number who dare mention it, and (as we see) prefer such purely speculative inventions as neutron stars and dark matter to explain observations, we know that Science has left the building.”

    So let’s see now … ApJ has published papers – lots of them – on plasmas and their dynamics (where’s the laughter?)

    Halton Arp, and other astronomers, uses the word “gas” when the context clearly means “plasma”, and also uses the word “plasma” without (apparent) sanction by journal editors or referees. Arp, along with many other astronomers, makes no mention of PDF “in explaining what we see”, much less says it has “an essential role” to play in such explanations (did Arp join Science in leaving the building?)

    But let’s have some more fun, shall we?

    How about you telling all readers, Nathan Myers, what you think the key differences are between language use in journals and the rules that apply here, with regard to the terms “gas” and “plasma”, and the role of PFD as a criterion for assessing the Science content of the respective materials?

    Oh, and would you be kind enough to answer at least two of the questions I asked you?

    What is the basis of your assertion that NGC 7319 is opaque?

    What is the mean free path of a gas particle (atom or molecule) in the ISM (interstellar medium)? Just an order of magnitude estimate will do thanks.

  94. Davidlpf

    Another strawman, strawman are made up arguments that easily explained by the user. Mostly used to distract from the fact they cannot answer the questions given them. You see nathan is out his league so he making questions and answers so he looks like he knows what he is different. Oh he is even wrong in his strawman.

    Nathan I know I probably have no chance of getting to answer any of the questions but the thing is longer you do not answer it more and more looks like you do not have clue what you are talking about to everybody who reads this. The thing is a lot of people come here a daily basis and some of them might (slime chance) be convinced by you so that is why I am still commenting on what you are posting here.From now on everytime you post on of your little insults or slanders I will link back here so everyone will know what we know you are nothing but a troll. (Also thinking about doing that universe today too.)

  95. @DRD: Obviously no galaxy is opaque throughout its breadth, at all wavelengths. At issue is whether objects in or beyond the galaxy in directions immediately adjacent to the QSO are obscured by dust. A tunnel of transparency just for us to be look through at a QSO is absurd. The mean free path of ions in the ISM is exactly zero; they interact with their immediate neighbors at all times.

    @Davidlpf: The chance that any reader at any time would have enough interest in your opinion about anything at all to follow a link you post is so low as to make me laugh.

  96. Davidlpf

    Well no answers still, keep proving my point Nathan.

  97. Davidlpf

    I think I Leave DRD to point out the path of the particles.

  98. DeiRenDopa

    DRD asked (3 (?) times): “What is the basis of your assertion that NGC 7319 is opaque?”

    Nathan said: “Obviously no galaxy is opaque throughout its breadth, at all wavelengths. At issue is whether objects in or beyond the galaxy in directions immediately adjacent to the QSO are obscured by dust. A tunnel of transparency just for us to be look through at a QSO is absurd.”

    Thanks for that.

    Let’s consider our own MW galaxy, near the Sun.

    On a moonless, clear, dark night, from a suitably dark site, at the right time of year/night, in the northern hemisphere you can see M31, the Andromeda galaxy, with your naked eye.

    On a moonless, clear, dark night, from a suitably dark site, at the right time of year/night, in the sourthern hemisphere you can see the LMC and SMC, the Magellanic Clouds, with your naked eye.

    More generally, almost all directions more than ~10 degrees away from the galactic plane, either north or south, from our location in the galaxy, provide clear lines of sight to millions of galaxies, in essentially all wavebands of the EM spectrum (the UV blue-ward of the Lyman limit, to the soft x-ray band, is somewhat of an exception; I’ll address that if anyone is interested).

    This means that an observer on a distant galaxy (say a few hundred Mpc from us) would be able to see right through the MW galaxy, in our vicinity, in all wavebands (caveat as above), provided they are not viewing us within 10 degrees or so of edge on.

    With respect to whether our location is special, in terms of the transparency of the MW disk in our vicinity, wrt spiral galaxies in general: from a century or more of research, a robust conclusion is that galaxy disks are essentially transparent when viewed at up to ~70 degrees of face-on (would you like me to provide you with some papers Nathan, so you can verify this for yourself?), in the optical waveband, outside of giant molecular clouds and regions of recent star-formation.

    And that, IMHO, is how science works Nathan … questions such as the transparency of a (relatively normal) spiral galaxy disk can be answered by drawing on the research results of thousands of astronomers, over a century or more, involving tens of millions (or more) of observations.

    An alternative approach may be termed “argument from incredulity”, and such an approach can be found in the writings of many who rail against contemporary biology, cosmology, and even geology. I’ll leave it up to each individual reader to assess the extent to which “[a] tunnel of transparency just for us to be look through at a QSO is absurd” is such an anti-science approach.

    Oh, and as the P. Galianni, E. Burbidge, G Burbidge, H. Arp, V. Junkkarinen, and S. Zibetti 2005 ApJ paper Nathan cites, on NGC 7319 and a QSO close to its nucleus, is available online, for free, I’ll also leave it up to each reader to decide for themself how closely Nathan’s summary of why the NGC 7319 disk is not transparent in the neighbourhood of the QSO corresponds to Galianni et al.’s approach (if anyone would like a URL to that paper, just ask).

    DRD asked Nathan Myers: “What is the mean free path of a gas particle (atom or molecule) in the ISM (interstellar medium)? Just an order of magnitude estimate will do thanks.”

    Nathan replied: “The mean free path of ions in the ISM is exactly zero; they interact with their immediate neighbors at all times.”

    Thanks for this.

    It seems my question was insufficiently clear; please allow me to clarify.

    By “gas particle (atom or molecule) ” I intended “neutral, un-ionised gas particle”.

    Let’s retract the steps that lead here, shall we?

    Nathan: “I will mention that the “gas” could not “slam” (presuming that’s what’s really going on at all) if it were not ionized; it would just pass right through, because it’s what in the lab we would call a “hard vacuum”, and gas particles barely interact unless they actually collide.”

    DRD, in response: “OK, I’ll bite; what’s the mean free path of a gas particle (atom or molecule) in the ISM (interstellar medium)? Just an order of magnitude estimate will do thanks.”

    What I am curious about is the extent to which Nathan can back up his claim concerning the “passing right through” each other, of (neutral) gas clouds which collide … where the gas clouds are in the ISMs of different galaxies.

    A quite separate question concerns Nathan’s claims that the ISM, in all its various phases, is completely ionised (i.e. every H has lost its electron, every He has lost at least one electron, and so on); I intent to take a closer look at these claims later.

  99. Davidlpf

    DRD wouldn’t the gas particles move in a random walk because of collisons between particles. So even if you had the particles that were ionized they would be travelling in different directions therefore what little electric current there is would be weak and also there would particles moving in opposite directions so cancelling what little magnet field there was there. Plus postive ions even moving the same direction would have an opposite magnetic field due to having an opposite charge.

  100. Davidlpf

    Nathan when the spectrum of the ISM is taken one thing that has been taken into account is broadening from collisions, so we have proof that not only does particles are colliding with each other we know that there are not moving all in the same direction. Therefore since to get the gas in the interstellar medium to act like plasma, first they have to be ionized and all have be travelling in same direction, since not all gas is ionized and not all are moving in the same direction therefore no plasma, therefor theory is dead.
    There are regions that all the particles travel in the same direction and are ionized due to enough collisions to give the particles enough energy to ionized. The thing is there are all spinning around a massive object like a spinning blackhole also due to the relationship eletricty and magnetism charge particles can travel up the magnetic field lines and cause jets into deep space.

  101. Davidlpf

    Nathan, I had to do homework for you because I don’t have century for stumble upon the right answer.

  102. Davidlpf

    Sorry DeiRenDopa for ruinning what you were trying to do.

  103. DeiRenDopa

    @Davidlpf: Nathan Myers’ comments on Phil Plait’s blogs are generally very strongly worded (well, those to do with astronomy that I’ve read are; I don’t know about other topics), and often quite absolute, with apparently no room for misunderstanding, shades of grey, or scope for clarification.

    An example: “We know that there are exceptions to [the Hubble] relation (e.g. the QSO in front of nearby opaque galaxy NGC 7319)” – for Nathan, there is no room for doubt, the QSO is ‘in front of’ NGC 7319, and NGC 7319 is ‘opaque’.

    Given such strongly expressed ideas, I expected Nathan would have been only too pleased to have the opportunity to explain further, to present material supporting those ideas, etc, and for him to demonstrate the depth and breadth of his knowledge and understanding of the science behind those strongly expressed ideas.

    Maybe it’s the way I have asked Nathan for clarification etc, or maybe he’s just busy, or maybe for some other reason, but so far it seems Nathan has not taken advantage of the opportunities, to explain his ideas further.

    To your comment about gas particles, random walks, and collisions: here’s what Nathan said: “The mean free path of ions in the ISM is exactly zero; they interact with their immediate neighbors at all times.”

    Now I’m quite puzzled by this, because as it is written it seems to be nonsense.

    Let me explain.

    One of the most common visual waveband emission lines in one of the ISM phases is the two green lines of [OIII]. These are ‘forbidden transitions’ of a doubly ionised oxygen atom, and the ‘forbidden’ term relates to the metastable nature of the excited state of the ion – left to its own, such an excited ion will not ‘decay’ to a lower energy state for some tens to hundreds of seconds.

    Yet the excited gas particle is clearly an ion, and clearly in the ISM (one phase of it anyway).

    But Nathan says such an ion’s mean free path “is exactly zero”! and that such an ion “interact[s] with [its] immediate neighbors at all times”!! Yet it sits there, in the ISM, sufficiently unperturbed for hundreds of seconds!!!

    I hope Nathan, or someone else, can clarify this apparent contradiction.

  104. DeiRenDopa

    @Nathan: SDSS object 587729652348223597 (http://cas.sdss.org/astro/en/tools/chart/chart.asp?ra=247.48968905&dec=40.63070747) is a spiral galaxy in the foreground with an elliptical galaxy in the background (or so it seems; I think some professional astronomers are going to take a much closer look to better constrain the range of possible interpretations) – IOW the spiral galaxy is back-lit.

    If you know how to, you can play with this image (or, better, the FITS) and estimate just how transparent the spiral galaxy is; all the data is available to anyone with an appropriate internet connection, for free.

    While the foreground object is certainly emitting photons, and the dust in the disk is almost certainly preferentially absorbing some of the photons from the background one, the spiral galaxy is anything but “opaque”.

    Interesting fact: this pair of overlapping galaxies seems to have been discovered by one of the ~100,000 Galaxy Zoo volunteers.

  105. Davidlpf

    DeiRenDopa
    I did not know that but I know what that implies, I will wait for
    Nathan to respond.

  106. Davidlpf

    Before Nathan comes back “see I told you were wrong”, I did not know what DRD was going at, there is evidence for what I said and has no bearing on anything else I said.

  107. @Davidlpf: Your capacity to absorb embarrassment astonishes even me.

    @DRD: Please feel free to provide evidence that your OIII ions are not experiencing electrostatic accelerations as they approach and recede from other OIII ions.

  108. Davidlpf

    Nathan it is up to you to prove your theory, if you even have one. At least I am grown up enough to realize when I am wrong unlike some.

  109. DeiRenDopa

    Nathan said: “The mean free path of ions in the ISM is exactly zero; they interact with their immediate neighbors at all times.”

    Later, Nathan said: “Please feel free to provide evidence that your OIII ions are not experiencing electrostatic accelerations as they approach and recede from other OIII ions.”

    @Nathan: it seems there is a breakdown in communication, evidenced by an apparent lack of mutual agreement on the key term “mean free path”.

    I introduced the term into this discussion, in the following exchange (I’ve bracketed the term with * symbols):

    Nathan: “I will mention that the “gas” could not “slam” (presuming that’s what’s really going on at all) if it were not ionized; it would just pass right through, because it’s what in the lab we would call a “hard vacuum”, and gas particles barely interact unless they actually collide.”

    DRD: “OK, I’ll bite; what’s the *mean free path* of a gas particle (atom or molecule) in the ISM (interstellar medium)? Just an order of magnitude estimate will do thanks.”

    Nathan: “The *mean free path* of ions in the ISM is exactly zero; they interact with their immediate neighbors at all times.”

    My use of the term is, as I understand it, straight from the physics textbook, e.g. here (http://hyperphysics.phy-astr.gsu.edu/hbase/Kinetic/menfre.html).

    It seems your use of the term, Nathan, is non-standard; would you be kind enough to provide a definition?

    One reason I am having difficulty with a meaning of the term, as I understand it from its context (i.e. Nathan’s statements), is that the mean free path of any particle in any environment is always zero!

    Why?

    Because I infer that it relates directly to the minimum (maximum?) distance over which there is no interaction (or acceleration due to interaction) with a particle’s immediate neighbours.

    But all particles (atoms, molecules, ions, electrons) have mass, and so there is always an interaction between neighbouring particles, with the particles experiencing accelerations as a consequence.

  110. DRD: I don’t find any suggestion that gravitational interaction is accounted for in the formulas you cited. Perhaps it’s considered negligible.

    Would you prefer to take the mean free path of ions in a fully ionized plasma as indefinitely large, as they may never actually collide in the ideal-gas sense? Or would you prefer to say every electrostatic interaction is a collision, so that all the ions are participating in collisions at all times? When a photon is released or absorbed in the process, would you count that as an inelastic collision?

    Might you say, instead, that a plasma is not accurately modeled as an ideal gas?

  111. DeiRenDopa

    @Nathan: what I have been trying to get to is your calculation of the mean free path of a (neutral) gas particle, in a typical ISM gas cloud (assumed to be neutral).

    Clearly, I have failed to achieve my objective.

    Now why was I (and still am) interested in this?

    Because of what you, Nathan, said: “I will mention that the “gas” could not “slam” (presuming that’s what’s really going on at all) if it were not ionized; it would just pass right through, because it’s what in the lab we would call a “hard vacuum”, and gas particles barely interact unless they actually collide.”

    I was (and still am) curious to know if you could back up your (very strong) assertion with some hard numbers and real physics.

    Whatever.

    Here’s my calculation; I’m interested in your perspective on this.

    Formula for mean free path (mfp), from the hyperphysics webpage in my earlier comment:
    1/(sqrt(2)*pi*n*d^2)
    where n is the density of particles per unit volume and d is the diameter of the gas particle.

    Let’s take d as 0.3 nm; note that it doesn’t matter much whether it’s 0.1 nm or even 1 nm, because I’m only interested in a general answer.

    The average density of (gas) particles in the ISM varies enormously, both within each of its phases and, more importantly, between each phase. So let’s take an easy number and also consider a range: 1 per cc, with a range of 0.1 to 1000 per cc.

    The mfp’s I get, with the above formula and values of input parameters, are (1 significant figure):
    3 billion km (d = 0.3 nm, n = 1/cc)
    30 billion km (d = 0.3 nm, n = 0.1/cc)
    3 million km (d = 0.3 nm, n = 1000/cc)
    200 million km (d = 1 nm, n = 1/cc).

    So it would seem that your (very strong) assertion, Nathan, is not supported by hard numbers and actual physics … two (neutral) gas clouds travelling at a relative speed of a few hundred km/s will “slam” into each other, with the gas particles undergoing collisions over a distance of no more than a distance about the size of our solar system.

    In particular, two such clouds will not pass right through each other, unless they are smaller than a few million to a few billion km in size.

    But maybe I did my sums wrong, or used the wrong page from the physics textbook. Would you be kind enough, Nathan, to show, with hard numbers and actual physics, that two such (neutral) gas clouds would pass right through each other?

  112. DRD: Working. While you’re waiting, what would you suggest for the average speed of hydrogen atoms in each cloud, relative to its reference frame, based on observed or presumed temperature?

  113. DeiRenDopa

    @Nathan: no worries. Neutral H, as atoms, is found in several different kinds of ISM, and within each kind the range of densities and temperatures is considerable, so it is misleading to give a single figure. In giant molecular clouds, the atomic H has temperatures of ~50-100K; in warm clouds, in which atomic H is mixed with ionised H, temperatures are ~<10,000K.

    Applying the standard formulae gives your typical H atom speeds of ~1 to 10 km/s in clouds with temperatures spanning the above ranges.

    Elsewhere, in commenting on another blog entry, Nathan said: "It’s a simple fact that all the detectable mass in the universe, save planet(oid)s, is plasma, partially or fully ionized, high-density or low."

    I'm quite curious about this; it's another strong assertion and also a very sweeping one.

    Would you mind providing some insights into what you consider the observational basis of this assertion is, Nathan?

    In light of the miscommunication earlier, perhaps you could start with a usable definition of "plasma", and apply that definition to the Earth's atmosphere (or several of its layers).

  114. DeiRenDopa

    @Nathan: I’ve noticed a number of other rather strong, sweeping assertions in your comments, in response to some of Phil Plait’s blogs, and I’m interested to understand better what the basis of those assertions is; would you mind taking some time to explain/expand please?

    Here are a few:

    “The big bang hardly counts, as it’s still speculative.” What are you referring to here, wrt “the big bang” and “speculative”?

    “The distance estimate [re a GRB] is little better supported than the origin myth.” What do you mean by “the origin myth” here?

    “Only plasma interacts appreciably with electromagnetic fields, and such interaction is not described by gas laws.” Can you clarify please? Specifically, by “electromagnetic fields” do you mean electric and/or magnetic fields? or do you mean photons? or something else??

    “When […] astronomers […] prefer such purely speculative inventions as neutron stars and dark matter to explain observations, we know that Science has left the building.” Why do you call neutron stars and dark matter “speculative inventions”? What specific meaning of “dark matter” are you using here? Once I understand better these points, I would like to explore what you mean by the last phrase; specifically, how you understand astronomy, astrophysics, and cosmology, as sciences, are conducted.

  115. @DRD:

    Big Bang, speculative: The fundamental problems with Big Bang have been well exposited in print. Who knows, they might even get resolved someday.

    Origin Myth: in context, refers to the origin of the GRB stated by Phil, on the basis of what appears to be no evidence whatsoever, to be a star collapsing to form a black hole. If you know of any evidence, I’m all ears. His reasoning appears to be, “I don’t know of any other gravitational process energetic enough, therefore …”

    Electromagnetic Fields: Ideal gas law says nothing about interaction with photons or other field phenomena. Real gases are composed of non-ideal particles that may absorb and re-emit photons, and may be ionized. Atoms don’t respond to the low-spatial-frequency effects that are what we usually call fields, although the ions do. Did you have a point?

    I have encountered no such thing as a “specific meaning” of dark matter. Any time an observed phenomenon cannot be accounted for by the gravitation of observable matter, dark matter is trotted out and simply assumed to have been placed wherever needed to produce the observed effect by adding in its gravitation.

    Similarly for neutron stars: periodic fluctuations are assumed to be produced by a rotating body, which must be small enough for to produce them at the observed frequency and dense enough for gravitation to contain it. If you know of any independent reason to believe neutrons can be stable in such an environment, I’m all ears.

    There’s nothing wrong with speculating, but you should be honest that’s what you’re doing.

  116. DeiRenDopa

    @Nathan: thanks for this.

    May I ask what is the extent of your physics training? Specifically, do you have the equivalent of a BSc degree with a major in physics? One reason I ask is that your comments seem, to me, to suggest that there is a disconnect between how you view the work of contemporary scientists (physicists) and how they view such work.

    I’ll address each of you comments later; in the meantime, do you intend to answer the other questions I asked? Specifically, “Would you mind providing some insights into what you consider the observational basis of this assertion is, Nathan?
    In light of the miscommunication earlier, perhaps you could start with a usable definition of “plasma”, and apply that definition to the Earth’s atmosphere (or several of its layers).”

  117. DeiRenDopa

    Nathan said: “The fundamental problems with Big Bang have been well exposited in print.”

    I must have missed these, and I’ve read plenty – look at the “Plasma Cosmology – woo or not” thread in the JREF Forum forum, for example – would you mind pointing these out, the ones that are consistent with contemporary science?

    Or are you saying that all of modern astrophysics, cosmology, etc is “speculative”?

  118. DeiRenDopa

    Nathan said: “Origin Myth: in context, refers to the origin of the GRB stated by Phil, on the basis of what appears to be no evidence whatsoever, to be a star collapsing to form a black hole. If you know of any evidence, I’m all ears.”

    Are you familiar with ADS (Astrophysics Data Service)? If not, I’ll provide the URL in my next comment.

    I put “GRB” in the title search field, and limited the search to “Astronomy” (i.e. not including physics or arXiv preprints), and the period to 2000 to 2008, and got >6000 references.

    Of course, many of these are simply reports of observations of GRBs, but there are quite a few on possible models, with many pages devoted to showing consistency between model and observation.

    But perhaps, as I have already noted, you are coming at this from a different viewpoint than that of contemporary science? May I ask what, if anything, in your view could – even in principle – constitute “evidence” for the idea that GRBs (or a class of GRBs or just one GRB) are a star collapsing to form a black hole?

  119. DeiRenDopa

    Nathan said: “I have encountered no such thing as a “specific meaning” of dark matter. Any time an observed phenomenon cannot be accounted for by the gravitation of observable matter, dark matter is trotted out and simply assumed to have been placed wherever needed to produce the observed effect by adding in its gravitation.”

    I’m afraid I really cannot relate this to astronomy.

    Perhaps it’s the “any time” part?

    Because that’s how Neptune was discovered, wasn’t it? And the failure to find any (significantly massive) object(s) with orbit(s) closer in to the Sun than Mercury, to account for Mercury’s observed motion, was the first successful post-diction of the theory of General Relativity, wasn’t it?

    Perhaps it’s the “cannot be accounted for by the gravitation of observable matter” part?

    Arguably the most well-known discovery from the Galaxy Zoo project is Hanny’s Voorwerp. It is, most definitely, “an observed phenomenon”, but I am unaware of any proposed explanations that include “dark matter”.

    Perhaps you meant to be rather less sweeping in your comment?

    Although I’m only about half-way through your comments, I must say I’m getting more and more unsure of what any of your comments mean, in terms of substantive content.

  120. DeiRenDopa

    Nathan said: “Electromagnetic Fields: Ideal gas law says nothing about interaction with photons or other field phenomena. Real gases are composed of non-ideal particles that may absorb and re-emit photons, and may be ionized. Atoms don’t respond to the low-spatial-frequency effects that are what we usually call fields, although the ions do. Did you have a point?”

    First, thanks again for the clarification.

    Here’s what you said earlier, that triggered my question: “Only plasma interacts appreciably with electromagnetic fields, and such interaction is not described by gas laws.”

    I’m having great difficulty understanding this Nathan.

    With the clarification of what you meant by “electromagnetic fields”, your first statement is clearly nonsense … photons can excite (neutral) gas particles (atoms or molecules), which subsequently relax to the ground state via emission of (other) photons. Plasma, or ionised gas particles, are not required.

    Further, the 21 cm hyperfine line of (neutral) hydrogen is widely observed, as have a number of astrophysical masers, several of which are due to neutral species such as water.

    It’s true that the ideal gas law is blind to atomic and molecular transitions, or the interaction of photons with matter in general … but that’s a different part of physics textbook anyway (quantum mechanics in general and QED in particular).

  121. DRD: You asked if I thought photons can interact with gases, and I confirmed that, yes, I am aware that they can both temporarily excite (“absorb and re-emit photons”) atoms, and also (if energetic enough) ionize them. Which part of that are you calling “nonsense”?

    Dark matter had not been discussed at the time Neptune was discovered. In any case, Neptune and Mercury seem both to be observable. If they had turned out not to be, one may reasonably doubt that astronomers of the time would have accepted a hypothesis that “dark matter” orbited in their places.

    I have never claimed there are no neutral atoms in space, so I don’t know why you mention the 21 cm line or the water masers. And why bring up gravitation among atoms in a gas?

    You must excuse me if I begin to suspect you are not serious.

  122. DeiRenDopa

    @Nathan: as I have said, several times, I have great difficulty understanding what you write! One reason is that your assertions are both sweeping and (apparently) absolute; another is that you seem to use at least some key terms with meanings that are non-standard.

    Here’s an example, you said: “Only plasma interacts appreciably with electromagnetic fields, and such interaction is not described by gas laws.”

    The “only plasma” seems to include the meaning “and not neutral gases”, and this is nonsense … neutral gases do “interact appreciably with electromagnetic fields”!

    Now of course the second part (the interaction between a plasma or a (neutral) gas “is not described by gas laws”) is true, but trivially so; in astrophysics the interaction between matter and radiation is studied using parts of the physics textbook appropriate to the interaction, e.g. general relativity (lensing), nuclear physics (main sequence stars), particle physics (cosmic rays, core collapse supernovae).

    Re dark matter.

    Here’s one of the difficulties I have: the term has at least three different meanings – ordinary (baryonic) matter that has not been detected by the photons it emits or absorbs (e.g. the IGM, until the advent of x-ray telescopes), non-baryonic matter such as neutrinos, and cold non-baryonic matter that comprises ~3/4 of the mass of the matter in the universe. By not clarifying which of these, if any or any combo, you mean, I can’t understand what you write. And your clarification only makes things worse, because you could be referring to any one of these three, any combination of them, or some other, idiosyncratic, meaning!

    It’s really quite frustrating trying to work out what you mean … non-standard uses of key terms, followed by what seems to me to be even more muddles.

    Last comment, for now: I had expected that you’d be only too pleased to take every opportunity to explain yourself more fully, and clarify things that are unclear to at least this one reader; after all, in my experience, that’s what scientists like to do (too often, you can’t get them to shut up!).

  123. DeiRenDopa

    Nathan said: “If you know of any independent reason to believe neutrons can be stable in such an environment, I’m all ears.”

    Um … as far as I know, it’s textbook physics. Just as when you learn about how the conduction electrons in a metal are (approximately) a Fermi gas, and that the pressure which holds a white dwarf star against gravitational collapse is the electron degeneracy pressure of the (electron) Fermi gas, so too a Fermi gas of neutrons has a neutron degeneracy pressure that holds a neutron star against gravitational collapse.

    Now as you probably already know, a Fermi gas is an ideal gas; in fact, it is the (one) quantum mechanical version of the classical ideal gas (and there is really no direct, quantum mechanical, analogue of the classical plasma).

    An interesting question is what prevents the neutrons in a neutron star from decaying into protons, electrons, and antineutrinos? After all, in our labs, that’s just what free neutrons do. Perhaps this is at least one question lurking cryptically behind your statement … is it?

  124. DRD: Now you’re not even pretending to be serious.

    When I say “the sun’s magnetic field”, I am, like others, not referring to its light. Similarly, when I say “dark matter”, I am, like others, referring to the putative stuff mentioned in the prayer that habitually ends astronomical press releases (e.g. “we hope this will someday help give us insight into the mystery of dark matter”). The prayer never says “cold non-baryonic dark matter”, but I don’t think anybody is confused by the omission.

    Parenthetically, I had not heard of the “~ 3/4 of the matter in the universe” figure; when last I heard, your “cold non-baryonic dark matter” was only 22% (or maybe 24%), and the even more mysterious “dark energy” made up the balance. Did the universe just get four times again more massive? I suppose that would leave only 0.4% hadrons. In any case the asymptote is clear: at some point the hadrons will be entirely negligible, ourselves included, and everyone (left?) will breathe a sigh of relief.

    I hope you’ll forgive me if I don’t peruse your “Plasma Cosmology – woo or not” thread. I am forced to doubt its seriousness.

    But getting back to your hypothetical non-ionized colliding gas clouds… it appears, by your own calculations (and pretending the clouds have somehow maintained a nice “slammable” boundary) that even after they met, it would take months more before an appreciable fraction of the atoms at each boundary happened to encounter a single atom of the opposing cloud, as they passed freely into one another. That hardly amounts to “slamming”, by my lights. (Please accept my regrets for not attending your next party.)

    Since you asked for a useful definition of “plasma”, you may refer to the Encyclopedia Britannica if you like. You might even find there an uncontroversial estimate for how much of the (hadronic, observable) universe is made of it. I don’t know why you mention Earth’s atmosphere; you are aware, are you not, that Earth is a planet, with a conventionally gaseous lower atmosphere?

    I await your next ingenuous query with quivering eagerness.

  125. DRD: Bless me, another question! You are too generous. Yes, indeed, when I asked how neutrons can be stable in a neutron star, I meant precisely that, no less and no more, with not a cryptonundrum to be found anywhere, nohow. Every neutron with which I have had much greater than fifteen minutes’ acquaintance had held at least a proton close at hand, and kept company with those of sits fellows barely more than an hundred, not two. I daresay an hundred neutrons, with scarce protons, makes not a noticeably large star. What say you?

  126. DeiRenDopa

    Nathan, there’s a thread in the Science, Technology and Mathematics section of the JREF Forum, called “Non-baryonic cold dark matter (“CDM”), the observational evidence” (http://forums.randi.org/showthread.php?t=112342).

    The OP (opening post) is by “DeiRenDopa”; in light of your recent comment about the limits of knowledge, in another blog, I’ll leave it up to you do decide whether the OP (opening poster) is the same person who is writing this comment or not.

    If you choose to not read that JREF Forum thread, or read it but choose not to discuss the observational evidence, I’d appreciate it if you’d be honest about that, and say so here.

    If you choose to read that JREF Forum thread, I’d be pleased to try to answer any questions you may have about the observational evidence presented in it.

    I’d be particularly happy if you were to present a case against the existence of CDM, within the framework of modern astrophysics.

    However, if you are more interested in discussing your own views of the nature of modern astrophysics, as a branch of contemporary science, I’d prefer that you do so in the 19 Sept blog (Swift bags etc), where there is already a discussion of that topic (sorta) under way.

  127. DeiRenDopa

    Nathan said: “But getting back to your hypothetical non-ionized colliding gas clouds… it appears, by your own calculations (and pretending the clouds have somehow maintained a nice “slammable” boundary) that even after they met, it would take months more before an appreciable fraction of the atoms at each boundary happened to encounter a single atom of the opposing cloud, as they passed freely into one another. That hardly amounts to “slamming”, by my lights. (Please accept my regrets for not attending your next party.)”

    I think it’s worth going back to where you first used this, to see if this can now be closed.

    In the “M83’s nursing arms” blog (2 Sept 08), you said: “@shane: Everybody who reads comments at all knows, now, that Phil’s pulling a fast one. I will mention that the “gas” could not “slam” (presuming that’s what’s really going on at all) if it were not ionized; it would just pass right through, because it’s what in the lab we would call a “hard vacuum”, and gas particles barely interact unless they actually collide. Plasma particles, by contrast, interact at macroscopic distances, so it really matters that, and how much, these “gases” are ionized.”

    Leaving aside the simple fact that Phil didn’t use the word “slam” in his blog anyway (does that make your comment a strawman argument?), we come to the question of whether two blobs of gas would “slam” together in a substantially different way than two blobs of plasma with the same density and atomic composition. And in particular whether the timescale for the plasma blobs’ slamming would be substantially shorter than months.

    Can you show us the relevant calculations to make such points?

  128. DeiRenDopa

    I found some standard plasma physics material online; the sections that seem to have direct pertinence to the calculations I expect you’ll be making, Nathan, are on this page (and just before and just after): http://farside.ph.utexas.edu/teaching/plasma/lectures1/node9.html

    When do you expect to be able to get back with the results of your calculations?

  129. DeiRenDopa

    Nathan said: “Yes, indeed, when I asked how neutrons can be stable in a neutron star, I meant precisely that, no less and no more, with not a cryptonundrum to be found anywhere, nohow. Every neutron with which I have had much greater than fifteen minutes’ acquaintance had held at least a proton close at hand, and kept company with those of sits fellows barely more than an hundred, not two. I daresay an hundred neutrons, with scarce protons, makes not a noticeably large star. What say you?”

    Neutrons decay by the ‘beta decay’ process, in which a down quark converts to an up quark with the emission of a W- boson, which subsequently decays to an electron and an anti-electron neutrino (or is it electron anti-neutrino?). This is the weak (nuclear) force in action; viewed ‘from afar’, the neutron becomes a proton, an electron, and an antineutrino.

    There is also an inverse beta decay process, in which a proton and electron become a neutron and an electron neutrino; this is the (weak force) process that is responsible for K-shell or L-shell electron capture radioactive decays.

    As you would expect, there is also a form of beta decay (beta+ decay) in which a proton decays into a neutron, a positron, and an electron neutrino. And these decays are observed in isotopes which favour them, energetically.

    And that’s the key to the stability of neutrons in a neutron star … they are not isolated, but are very tightly bound to the star itself, so beta decay is strongly suppressed. In fact, the neutron degeneracy pressure arises because the protons and electrons in the precursor object (the collapsing core of the supernova) undergo inverse beta decay, because it is energetically favoured.

    Analogies are always risky, because it’s all too easy to take them too far, but neutrons are stable in a neutron star, but not on their own, in a way somewhat analogous to how some crystalline forms of ice are stable under very high pressure but not under low pressure.

    Relating this to what happens on your lab bench: the two green [OIII] ‘forbidden’ lines (‘nebulium’) have never been observed in any lab, because no lab can create a sufficiently hard vacuum for long enough, and also excite oxygen ions sufficiently to populate the metastable state (from which the nebular lines originate). Yet I’ve never found anyone who claims the identification of these very common lines (in planetary nebulae, for example) with those two forbidden transitions is unwarranted simply because it hasn’t been observed in a lab.

    So too with the stability of neutrons in a neutron star: no earthly lab has come close to creating the physical environment experienced by neutrons in such objects, yet the underlying (nuclear, particle physics) theory is just as solidly based in lab work as the (atomic, quantum physics) theory underlying [OIII] lines. Please let me know if you have any further technical questions on this.

  130. DRD: Thank you for the neutron energetics exposition.

  131. DeiRenDopa

    @Nathan: you’re welcome.

    Do you have any questions on it?

    May I also ask: when do you expect to be presenting the results of your calculations concerning the collision of two plasma clouds?

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