Evidence and theory collide with galactic proportions

By Phil Plait | January 5, 2011 7:00 am

I have a morality tale to tell here, but first we have to do some science. The science is part of the moral, and it’s actually rather surprising and cool. And it was reading about the science that made me chuckle, because the moral to me — as a scientist myself — was pretty obvious, but I know to others it will be as opaque as black hole.

Speaking of which…

We know that at the heart of every big galaxy lies a supermassive black hole. There’s one at the center of our galaxy — tipping the cosmic scale at 4 million times the mass of the Sun! — and one in Andromeda. In fact, looking for these monsters* was one of the key missions for building and launching the Hubble Space Telescope, a mission it had great success with.

There be monsters here. Click to supermassivate.

Why those black holes are there, and so huge, is a matter of some discussion. We’re pretty sure they formed at the same time as their host galaxies themselves, and in fact helped the galaxies grow at the same time the galaxies fed the black holes material. We also know that big galaxies like our Milky Way grew to their current enormous size by literally colliding with and eating other galaxies. This would inevitably lead to the doomed smaller galaxy’s black hole falling to the center of our galaxy, where the insatiable black hole already there would merge with it, growing bigger.

When this happens, so it’s thought, matter in the form of gas, dust, and stars would also fall into the center, feeding the black hole. The matter can pile up outside the hole and get incredibly hot — observations indicate it can reach many millions of degrees, blasting out light in the form of X-rays. Galaxies like these are called active, and we see them everywhere. And many of these active galaxies are weirdly shaped, distorted, indicating they may have recently undergone a big collision. Aha! That fits the idea that colliding galaxies feed black holes and make them active.

There have been so many observations of this that it has matured to become the standard assumption: most active galaxies have recently collided with another galaxy, dumping material into the core and triggering an outburst. I can’t tell you how many papers I’ve read about this, especially when I was working on the public outreach for the Fermi satellite, which was designed to look at active galaxies.

It’s a good story. The problem is, it looks like it’s wrong.


Astronomers using a fleet of telescopes observed over 1400 galaxies of all types, about 10% of which were classified as active. Looking at the shapes of the active galaxies (as well as the non-active ones as a control group — in that way, this was similar to a double-blind medical research study), they found that there is little or no connection between active galaxies and collisions/mergers.

This is stunning news! It goes against the paradigm that has been years, decades in the making. It’s not unbelievable, and by that I mean it doesn’t rely on weird assumptions or new science or anything like that. Something else must be making these galaxies active; perhaps instabilities inside them, or internal gas cloud collisions, or some other phenomenon. But apparently, at least for the past 8 billion years, it’s not due to collisions on a galactic scale. Mergers don’t feed the supermassive black holes and make them active in the way everyone assumed.

I imagine this will be a topic of much debate at the upcoming American Astronomical Society meeting in Seattle this week. But in the end, if the observations hold up, and the conclusions are sound, a remarkable thing will happen: it will be accepted. Scientists will see that their assumptions were wrong, or at least need to be modified, and there will be a shift in the way astronomy of active galaxies is done. Perhaps there’s more to this story, perhaps more observations are needed, perhaps different populations of galaxies need to be studied. But if it holds up, scientists will change their minds.

And that is why this is a morality tale. When scientists see better data, when the evidence is weighed, they can change their minds! This, despite claims from antiscientists of all stripes — homeopaths, antivaxxers, alt-medders, and so on — who claim scientists are too entrenched and too protective of the status quo (this is a standard trope in their claims). And there’s another moral, too: scientists do indeed actively engage with and try to overturn the status quo if they perceive it as wrong. Or, if they test it just to check it and find out it’s wrong, boom! They publish. Again, a lot of antiscience advocates say that scientists are too scared for their funding to overturn the mainstream thinking, but that’s utter baloney. They do it, and they do it a lot. They revel in it. You should hear the arguments that go on at colloquia and meetings!

That, to me, is what I was saying is obvious. Of course there are personal stakes and egos here, and it can be hard to let go of a hypothesis. Scientists are people. But by and large they’re people who see that what they are doing is bigger than themselves, bigger even than the specific research they’re doing. What they’re trying to do is codify the Universe itself! We can believe in all sorts of things, but that doesn’t make them true. Science is a way of marking that boundary. And it takes nothing away from the wonder — after all we’re studying galaxies, and galaxies that collide; we’re studying black holes and streams of trillions of tons of gas plunging into their waiting maws.

When I look out at the sky, I see all sorts of amazing and wonderful things, and the best part is that because of science, I know they’re real.



* I know, this is a morality tale, not a fairy tale, but that doesn’t mean it can’t have monsters too.

Comments (66)

  1. John

    Correction:

    “When scientists see better data, when the evidence is weighed *and there are no negative political or financial implications of doing so*, they can change their minds!”

    This is an exceptional case, unfortunately.

  2. Liam Bradey

    Brilliant post, Phil. It’s always nice to see that when most scientists are presented with evidence that their existing hypotheses are wrong, that they can just look at the evidence and say “yes, I was wrong, let us study this more” instead of whining and crying and blindly saying “this cannot be” and citing history and precedence. Ironically, unlike the alt-med types, who though their practices have been debunked, still persist in believing in their effectiveness.

    Thanks again on behalf of the world for all that you do!

  3. Great morality tale!

    While science is excellent at abandoning everything it once held dear with no regrets, this kind of ‘brand loyalty’ does still seem to exist to a small degree.

    So while you probably won’t get many people refusing to accept relativity in favour of good ol’ Newtonian gravity, there still seems to be an alarming number of people who can’t let go of Pluto being planet #9.

  4. Gary

    Afred Wegener will be happy to learn his critics were just pulling his leg for fifty years. *Eventually* the truth will out, yes; but until the evidence is so incontrovertible that nobody can deny it, the evidence shows that scientist are as likely as divas to protect their turf by any means possible. This self-congratulatory post seems a little over-wrought.

    On the other hand and to be fair, it isn’t necessarily a bad thing to be tenacious in holding your position for the right reasons. What is hard is knowing just how honest you really are.

  5. SLC

    Here is a, perhaps, somewhat apocryphal story from the past which illustrates Dr. Plaits’ thesis. Back in the 19th century, William Thompson (later Lord Kelvin), one of the founders of the theory of thermodynamics, did a calculation involving the radiation of heat from the earth which seemed to indicate that the earth was about 100 million years old. Charles Darwin was led to conclude that, if Kelvin was correct, his theory of evolution would absolutely collapse. Early in the 20th century, another Thompson, J. J. Thompson, gave a lecture describing the then recent findings of radioactivity. He proposed that the presence of radioactive material in the earths’ core would be a source of heat energy which would negate the computations of Kelvin and would lead to a much older estimate of the age of the earth. It turned out that Kelvin was in the audience and was seen to nod in agreement with Thompson and murmur that he, Kelvin, was wrong.

  6. Ryan Brown

    I’m not an evolutionary biologist, but I do want to point this talk out:

    http://www.ted.com/talks/lang/eng/elaine_morgan_says_we_evolved_from_aquatic_apes.html

    She presents some interesting concepts, and by her arguments a lot of scientists are simply ignoring the evidence for her theory. Again, I don’t know any details about the field, I’m not an expert, etc. etc.

    My point is that scientists are people too, and they do get entrenched in their ideas sometimes. See Ignaz Semmelweis, Johannes Kepler, etc. Yes, the ideas do usually eventually change, but we’re all capable of blind adherence to a way of thinking.

  7. Richard

    SLC – you’re referring to Rutherford, aren’t you? And Rutherford was very diplomatic (so he says) in his lecture:

    “I came into the room, which was half dark, and presently spotted Lord Kelvin in the audience and realized that I was in trouble at the last part of my speech dealing with the age of the earth, where my views conflicted with his. To my relief, Kelvin fell fast asleep, but as I came to the important point, I saw the old bird sit up, open an eye, and cock a baleful glance at me! Then a sudden inspiration came, and I said, ‘Lord Kelvin had limited the age of the earth, provided no new source was discovered. That prophetic utterance refers to what we are now considering tonight, radium!’ Behold! the old boy beamed upon me.”

    http://en.wikipedia.org/wiki/Age_of_the_Earth

  8. KiltBear

    Thanks for this post. While you advocate being a skeptic, I think many anti-religious pro-science folks think that science is based on immutable fact, rather than a process of discovery and verification (and sometimes anti-discovery.) It has been my experience that many folks have replaced priests with scientists and religion with science and really don’t understand the basis principle of theory with best supporting facts at the time vs “truth”. It is always fun to engage these folks and try to point out that their lack of critical skills and thinking leave them no better off than those with blind religious faith and zeal.

  9. Brett from Canada

    “Perhaps there’s more to this story, perhaps more observations are needed, perhaps different populations of galaxies need to be studied. But if it holds up, scientists will change their minds. ”

    On that topic, though, it’s worth reading this article in the New Yorker about something called the “Decline Effect”:

    http://www.newyorker.com/reporting/2010/12/13/101213fa_fact_lehrer

    The fundamental point in the article is that, particularly early on when a new idea is cool and in vogue, will tend to only publish results that *confirm* the theory they are testing. That means study after study that produces a nil result may never see the light of day because it’s not considered “interesting” by those conducting the study or funding the research, and so the theory in question will end up looking better than it actually is.

    But once the idea has reached the stage of being “accepted”, suddenly the mentality shifts. No longer are scientists interested in “proving” (I use that term colloquially) the theory to be true. Instead, they focus on trying to disprove the theory, and suddenly the rate of negative results goes up.

    The fundamental lesson to take from this is an important one: even scientists with the absolute best of intentions *will* allow their biases to leak through.

    Fortunately, the scientific method *does* work over the long term… the problem is, it can mean a decade of lost time as scientists pursue theories that are ultimately erroneous… like, say, a theory examining the cause of active supermassive black holse in galaxies. :)

  10. Alareth

    Well. A scientific theory was proven wrong.

    This means all science is wrong and this “modern” world is a complete and utter sham.

    I guess I’ll head to a cave and bang some sticks together to try and figure out why the sky gets dark everyday.

    It was fun while it lasted, goodbye science.

  11. Daniel J. Andrews

    John @1: What is your evidence that this is an exceptional case? All you’ve done is reword the standard denialist trope, “Scientists are corrupt” a la astronauts are lying as the moon landing was a hoax. Same thing, same smear, same old same old. E.g. CFC–ozone, HIV–AIDs, CO2–AGW, smoking–cancer, emissions–acid rain, asbestos–lung disease, as well as smears against people in evolution, cosmology, geology, physics, etc etc etc etc….

    Pathetic, but when ideologue groups don’t have evidence to counter the science guess they’re stuck with smearing the messengers. It is called AntiScience Syndrome.

  12. Stephen P

    @Ryan: if you want to know why the Aquatic Ape hypothesis is not generally accepted, try Jim Moore’s site on the subject: http://www.aquaticape.org/

  13. Pascvaks

    It’s easy to swallow things which aren’t too bitter or too sour, and too hard or too soft, and too big or too little. “Swallow-ability” also has a lot to do with who’s holding our nose and/or who isn’t. People are people, thankgoodness, no matter our age or title most of us are pretty decent folks. Thankfully, the truly vast majority of us are also quite moderate and prone to be very open to ‘new’ ideas. (At least for 5 or 10 minutes;-)

  14. Spaceman Spiff

    A couple of comments on the science presented in this paper.

    This study addresses active galactic nuclei (AGN) at redshifts z 2 (more than 10 billion years ago) and more recent ones z < 1 (less than 8 billion years ago). Heck set aside AGN — galaxy evolution changed dramatically between those two epochs. This is even true for the Milky Way, which apparently grew up in a rather quiet corner of the universe. Coincidence? In any case the findings of this study appear to be a significant break-through.

  15. Bora Cilek

    Great post..
    meanwhile I need some serious help from all of you people..I, like many others, had serious suspicions about the Dark Matter theory..for the past 8 months I came to the conclusion that we do not need DM at all to explain Flat Galaxy Rotation Curves and other similar phenomena..and it doesnt involve any egzotic theories, tensor fields, complex models etc..simple math, straightforward physics..I need help in finding the right place to publish this and probably, the right people to endorse it..

  16. Ryan Brown

    @Stephen P Thanks. Like I said, I know next to nothing about it (I just saw the talk a few days ago), but I thought it was worth mentioning.

  17. Bob_In_Wales

    Blimey, we’ve hit on a deep one here. This is one of those topics best reserved for the pub and a good long face to face. However, it is also a good chance to trot out one of my favourite quotes:

    A new scientific truth does not triumph by convincing opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.
    Max Planck, A Scientific Autobiography and Other Papers, 1949

    P.S. While hunting for the exact quote and who said it I found this, which is quite amusing:

    Physics isn’t a religion. If it were, we’d have a much easier time raising money.
    Leon Lederman

  18. M. B. Cilek

    Great post..I couldnt agree more.
    Meanwhile in a much related subject, I need your help..seriously !!
    the topic is “Flat Galaxy Rotation Curves and Dark Matter”..This is no joke frds, I just proved that we do not need DM at all to explain this and some other similar phenomena..and the theory involves no egzotic models, complex mathematics, weird conceptualisations..just simple math and straightforward phsics..I need to publish the theory (a very short article about 3 Word pages) in a credible place but they normally ask for endorsements..and I dont want my idea to be stolen during this process..waiting for your suggestions..

  19. Brett from Canada

    @Bora:

    See, the problem with a post like yours is this phrase: “it doesnt involve any egzotic theories, tensor fields, complex models etc..simple math, straightforward physics”.

    If that were true, I absolutely guarantee you someone would’ve already discovered this solution, published the results and been lauded as a hero. I mean, let’s face it, no physicists *wants* DM to exist, and there are no shortage of skeptics like yourself who insist it doesn’t, so if there *were* a “simple… straightforward” explanation, I’m confident we would’ve seen it by now.

    This is no different than that quote from Fermat about his infamous theorem, claiming to have found a “simple” solution to the equation. Turns out there was nothing simple at all about the final proof, and so we can either conclude that Fermat was a genius who found a solution no one else, in the hundreds of years following, did, or we can conclude he was simply wrong. The latter seems far more likely, don’t you think?

  20. Wee Mad Andrew

    To digress briefly from the coolness of watching Science At Work:

    I’m always impressed and a even a bit overwhelmed at the difficulty inherent in astronomy given that it’s rather stuck with a single snapshot in time of the distant universe, considering the timescale of us being able to look at it. As a chemist, I couldn’t imagine not being able to run experiments over and over to say “Yep, it’s like that every time.” So this sort of thing is always terribly enlightening.

  21. it doesnt involve any egzotic theories, tensor fields, complex models etc..simple math, straightforward physics

    This sounds disturbingly like the “plasma universe” claims I heard in the early 90s. I hope you have better luck with your hypothesis. Sorry I can’t help you; I’m not a physicist.

  22. M. B. Cilek

    yes, you are absolutely right..my feelings about the simplicity arose from the complexity of hundreds of articles I had downloaded from Arxiv and other similar sites..it is “relatively simple” I had to say, sorry..But I sincerely believe you would agree that “it is absolutely simple” when you see it..just for the sake of the theme of the blog, I suffer from the beurocracy in the scientific community and I regret how young minds are ignored and forced to follow insane theories like dark matter at the expense of creativity..anyway I indeed thank you beacause you took this seriously and bothered to reply..btw, I intend to publish the theory on St Valentines day (feb 14 right) and would like to share it with this blog first..

  23. This was was a big journal-club hit here – I awarded it my “everything-you-know-is-wrong” award for the month. The paper phrases their conclusions with proper precision – over this redshift and luminosity range, major mergers are not a significant contributor (thereby upsetting a lot of sort-of-handwavey theorists over the years…). They specifically note that their results leave open the possibility that less spectacular interactions could matter – and that, since they are more frequent, is a good direction to look. After all, these results have to be reconciled with the statistical studies that have indicated some kinds of AGN being linked to interactions. In one sense, the most interesting implication may be – since they reshuffle so much of the stars ad gas, why don’t mergers trigger luminous AGN (as they clearly do for starbursts)? One more thing of note – this used old-fashioned morphological classification, rather than any of its quantitive and less discriminating substitutes. I love the double-blind way they did it, too.

  24. I’m reminded of Isaac Asimov’s famous quote: “The most exciting phrase to hear in science, the one that heralds new discoveries, is not ‘Eureka’ but ‘That’s funny…'”

    When a scientist sees something that shouldn’t be happening according to widely accepted theory, *that* is the most exciting moment of a scientist’s life. It means he might improve upon a widely accepted theory or perhaps even knock over completely.

    In fact, scientists regularly try to knock down theories. If a theory seems to hold up, they’ll find the edge cases and test those to push the theory to its limits. (“How does it work if the speed is radically increased? Radically decreased? What about the temperature?”) If the theory doesn’t hold up, even better because then they get to take the new evidence and formulate a new theory.

    Of course, now I have a vision of Science-As-Mythbusters, only with the real explosions replaced with exploding theories. “Well, looks like this theory is confirmed if we use normal temperatures. Let’s ramp it up a few hundred degrees. Scientist Want Big Theory Boom!” ;-)

  25. ThirtyFiveUp

    Brett from Canada Says: Fermat?????

    Here is an answer which I suspect you know, but just in case others are wondering:

    Fermat’s enigma has been solved by Andrew Wiles in two papers consisting of 130 pages in total, and were published in the Annals of Mathematics (May, 1995).

    http://www.google.com/search?client=safari&rls=en-us&q=andrew+wiles&ie=UTF-8&oe=UTF-8

    Google search for Wiles, who is a true hero.

  26. Yojimbo

    See! That’s what’s wrong with science – ya can’t rely on it. Every time ya learn it, they change it.

  27. Revyloution

    That’s why religion is better than science, it never changes. You can always count on it. It’s truths are eternal, while scientists can’t make up their mind about anything.

    Praise “Bob” Dobs and and the infallibility of the holy Book of the SubGenius.

  28. mike burkhart

    This is what makes Science good it corects its mistakes .After all science is a serch for facts, and as I have said I think of the Universe as a big rubiks cube some times we just may turn is the wrong way and have to back track to get it right, I don’t know if we will ever solve it but we will keep on trying.

  29. Yojimbo

    @27 As a Pastafarian, my infallible holy book is different from yours (and so by definition more holy and more infallible). But as the FSM sorta frowns on it, I won’t be calling for a holy war. :)

  30. DrFlimmer

    @ M.B. Cilek

    Why don’t you try arxiv? You don’t need to pay anything. All you need is probably a .tex-file of your paper (which can also be downloaded for free, however it is not “straight forward”).
    If your theory is really scientifically sound, then there is no need to hide it for over another month. Go ahead, publish it.

    A journal that is (almost) free of charge is “Astronomy & Astrophysics”. Try them if other journals are too expensive.

  31. Chris A.

    @M.B. Cilek (#22):

    “…I regret how young minds are ignored and forced to follow insane theories like dark matter at the expense of creativity…”

    What’s so insane about dark matter? Isn’t it a bit presumptuous to assume that all matter in the universe must be self-luminous and/or interact strongly with e-m radiation? Why should that be so?

    I think it’s far more sensible to allow for the possibility of dark matter than to rule it out a priori, especially when there is some fairly compelling evidence for its existence (not just flat galactic rotation curves, but also lensing effects).

  32. M. B. Cilek

    @DrFlimmer
    I tried Arxiv..they have a new rule, they ask for endorsement from recognised authors..and these scientists usually endorse people that they know..I havent checked “Astronomy & Astrophysics”..I will look into it..thanks.

    @Chris A.
    I hadnot ruled out DM a priori..I it just seems so artificially manufactured without any sound clues and many of its proposed “consequences” might be explained by other means (like Frame Dragging)..I dont even bother mentioning so many contradicting facts like the “Cuspy Halo Problem” and many others..by the way, as u know the generic term “Dark Matter” also includes things like neutron stars, brown dwarfs etc.. which are literally dark (MACHOS in general) and certainly exist, but exotic DM like Wimps and so forth are beyond my understanding..maybe I am too conservative :-)

  33. M. B. Cilek

    @Naked Bunny with a Whip
    “..This sounds disturbingly like the “plasma universe” claims I heard in the early 90s.”

    yeah well, the universe might not be plasma, but it is most certainly a “fluid”.. which probably will form the basis for another “straightforward” theory..actually history seems to repeat itself, scientists believed in “aether” for hundreds of years, then it was wiped out in the early 20th century, and then what happened ? Dark Matter, Dark Energy..haha, Welcome back to the club, we missed you !! yes pals, there shoud be something out there, we just cannot perceive it yet…

  34. Keith Bowden

    “…literally colliding with and eating other galaxies”? Where’s the mouth on a galaxy? (For that matter, where’s the, um, exit? Don’t think I’d want to be around either.) Okay, the collision is literal, the eating is figurative.

    (Sorry, misuse of “literal” is a pet peeve.)

    Okay, now that I’ve scratched that itch… great posts today! I’m not only reading and learning a lot here, I’m clicking through to read and learn from other sources (including the original BA site). Thanks, Phil!

  35. Joseph G

    @#31 Chris A: Is there any known kind of matter that doesn’t interact strongly with EM radiation in SOME way??

    I know that this is very unscientific of me, but fallible as it is, my “gut” also has some serious questions about the existence of dark matter, or at least the more “exotic” interpretations of it (that it’s not simply dark, massive objects, for instance, but actual matter that doesn’t interact with “normal” matter) except via gravity.
    I know that science often infers something from an unexpected result (in this case galactic rotation curves, specifically) but c’mon, you have to admit that, at least on the surface, DM sounds very “wooey” and contrary to Occam’s razor.
    I mean, if you had no background in science and had never heard of dark matter before, and someone said to you “Well, these observations aren’t matching what we expect to see – so let’s just say that the majority of the galaxy is made up of this stuff that has mass but that we can’t see or interact with.” – what would you think? It sounds almost like an astrophysical “God of the gaps”.

    In any case, I’m confident that scientists will figure it out sooner or later. Whether DM exists or not, the debate is pretty darned exciting to me – it means there are yet some very major discoveries to be made about the nature of gravity or matter (or both).

  36. M. B. Cilek

    @ Joseph G

    exactly..we are still a bit like the ancient humans..lightning strikes-god of fire; floods hit-poseidon god of the seas; we are in love-eros god of sex…gravitational lensing and speedy stars-the Dark Knight (eee sorry Dark Matter I meant :) ) god of Cosmos..lazy thinking, easy escape..we have enough scientific background to figure out all of these I believe..Newton and Einstein supplied us with more than enough insight long ago..just need to have some more faith in physics and math, thats all..history is in the making friends…..

  37. Joseph G

    Gah, it wouldn’t let me edit that.
    To clarify, I know that galactic rotation curves are far from the only evidence supporting Dark Matter, it’s just the single most well-known and striking anomaly that we see, and any prospective modified gravity theory (or quantification of MACHOs, WIMPs etc) would of course need to be congruent with those other measurements, too.

    @#34 Keith Bowden: Heh, reminds me of this old MadTV sketch with these people who would stress the word “literally,” and use it to describe anything, even when it wasn’t necessary. E.G. “I’m LITERALLY nauseated by this food. LITERALLY. It’s LITERALLY inedible. LITERALLY.”

    @M.B.Cilek: Keeping in mind that I’m ignorant about math, what do you think are causing the discrepancies that led to the “invention” of DM? Inaccurate estimates of mass, errors in observation, or something else entirely?

  38. Colin

    (Sorry, misuse of “literal” is a pet peeve.)

    From my understanding, there would be very few literal collisions either. In fact, eating is more technically correct than colliding. Course, the misuse of literal is not a pet peeve of mine, so… play on.

  39. M. B. Cilek

    @ Joseph G
    I believe the main problem is wrong (or unadjusted shall we say) observations and consequently inaccurate estimates of galactic mass..I wish I could be more specific, but that is not possible for the time being..btw, I am not a phsyicist, an Electrical Engineer at best and about to crash out since I live on the other side of the world..
    cheers..

  40. Wow. I’m one of the folks who’ve long believed that galactic collisions can lead to AGN activity, and indeed I’ve said this in a lot of popular talks.

    Given that (at least last time I checked) interacting galaxies *are* associated with nuclear starbursts, we do have reason to believe that all the theoretical predictions that interactions will funnel a lot of the gas (i.e. raw material for making stars and/or fuelling AGN) towards the center of the merged galaxy. With all that stuff down there, it seems that it *ought* to fuel the black hole. But, perhaps, it can’t get rid of angular momentum fast enough to get all the way down there? And, in the process, gets “used up” in a nuclear starburst? It will be interesting to find out! It will also be interesting to see if this result holds.

  41. Messier Tidy Upper

    Great post & fascinating tale, thanks BA :-)

    I wonder how we’re going to explain this and what new theories will rise – and possibly fall.

    It raises a lot of new questions and questions a lot of old answers and is a good reminder to be humble about what we think we know and how certain we are that we *really* know it after all.

    When I look out at the sky, I see all sorts of amazing and wonderful things, and the best part is that because of science, I know they’re real.

    Except, such certainty is NOT really there is it? ;-)

    Looking at say, Betelgeux, Naos (Zeta Puppis) or Eta Carinae, we can’t say for sure that the speck in the sky we’re seeing hasn’t already gone supernova and that it still exists at all.

    Looking at Deneb, Canopus or Rigel we can’t be 100% sure their spectral class hasn’t shifted and evolved in the interim of light years of spacetime between the photons leaving the stellar surfaces and arriving in our eyes.

    We know we’re seeing galaxies as they *were* millions of years ago NOT as they appear today. (admittedly the change is probably usually slight but still)

    We even know we’re seeing the Moon as it was a second or two ago and our Sun as it was eight minutes or so.

    Science I think teaches us to question – teaches us that what we think is “real” may not really be.

    It tells us our eyes, our minds, and our textbooks can be unreliable and can fool us.

    We should therefore always be humble and always admit there are some error bars around what we think we know.

    That’s my two cents worth anyhow. Of course, I could be wrong here! ;-)

  42. John

    @Daniel J. Andrews #11

    Because there are few, if any, financial or political consequences of the results. This is an exception, rather than the rule. It makes perfect sense as more money is likely thrown in the direction of research that does have.

    I don’t have a problem with science, I just think bent science is way more troubling than anti-science, mainly because the latter is easier to spot.

  43. Messier Tidy Upper

    It is one of the best traits of science (& scientists) that it (they) constantly checks and revises & will admit when it gets things wrong.

    Dead certainty and unchangeable inflexibility are, I think, flaws not virtues although many religions & religious folks seem to think and claim otherwise.

    @17. Bob_In_Wales :

    Blimey, we’ve hit on a deep one here. This is one of those topics best reserved for the pub and a good long face to face. However, it is also a good chance to trot out one of my favourite quotes:

    “A new scientific truth does not triumph by convincing opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.”
    Max Planck,
    A Scientific Autobiography and Other Papers, 1949

    Sounds very much like Thomas (?) Kuhn’s idea of scientific revolutions as the original and technically most applicable idea of the now vastly over-used and abused “paradigm shift” term.

    Which is NOT always true methinks – but often so.

    P.S. While hunting for the exact quote and who said it I found this, which is quite amusing:

    “Physics isn’t a religion. If it were, we’d have a much easier time raising money.”
    Leon Lederman

    Now *that* is both very true & very funny! Hadn’t heard that ‘un before – thanks Bob_In_Wales for that! :-D

  44. Messier Tidy Upper

    Thomas (?) Kuhn’s

    On checking, yep, it is indeed Thomas Kuhn – See :

    http://en.wikipedia.org/wiki/Thomas_Kuhn

    &

    http://en.wikipedia.org/wiki/Paradigm_shift

    &

    http://en.wikipedia.org/wiki/Philosophy_of_science

    for more. Hope these links are interesting / useful for y’all. :-)

  45. Kmarion

    Great post. Sometimes it seems as if it is a no win battle though. Either the egos of Scientist are too big to accept other theories, or “look, scientist can’t seem to get anything right” .. well yea, you know the crowd.

  46. Nigel Depledge

    John (1) said:

    Correction:

    “When scientists see better data, when the evidence is weighed *and there are no negative political or financial implications of doing so*, they can change their minds!”

    This is an exceptional case, unfortunately.

    Is it?

    I think this claim requires some evidentiary support. Put up, or shut up, I say.

  47. Nigel Depledge

    Liam Bradey (2) said:

    . . . [scientists] can just look at the evidence and say “yes, I was wrong, let us study this more” instead of whining and crying and blindly saying “this cannot be” and citing history and precedence

    Individual scientists do sometimes fall prey to this (for example, as far as I am aware, Einstein never accepted the basic ideas of quantum mechanics). However, science as a whole moves ever forward, based on evidence and reasoning. For example, Wegener’s initial formulation of continental drift was not adequately supported by evidence, and his contemporaries rejected his idea. Subsequently, as new evidence came to light, Wegener was proved right. Now, continental drift is a necessary component of our understanding of the Earth.

  48. Nigel Depledge

    Ryan Brown (6) said:

    She presents some interesting concepts, and by her arguments a lot of scientists are simply ignoring the evidence for her theory. Again, I don’t know any details about the field, I’m not an expert, etc. etc.

    Well, I can’t follow the link you provide from work, but I guess from the title that the theory is the old “aquatic ape” idea.

    IIUC, there is currently no consensus about whether or not the aquatic ape idea is correct.

    On the one hand, the hypothesis very neatly explains many odd features about humans where we differ from the other great apes.

    On the other hand, there is a twofold problem. The first part is that we haven’t any evidence to indicate that any stage of our ancestry since we split from the chimpanzee lineage was aquatic (or sufficiently aquatic for the adaptations to have been brought about by this lifestyle). The second part is that it doesn’t really fit what has already been worked out from the evidence that we do have, i.e. that, until they migrated out of Africa, most ancient hominins lived in parts of Africa that are some considerable distance from any coast.

    A compounding issue is that, since pretty much all of the “aquatic ape” adaptations occur in soft tissues, we may never have the evidence to resolve this for sure, as soft tissues are notoriously poorly preserved as fossils.

    Until we have some better evidence, the aquatic ape idea cannot be resolved – IMO it remains a possibility, but the features of human anatomy that might be explained by the aquatic ape hypothesis remain only circumstantial evidence for it.

  49. Mike

    When you speak of science vs anti-science you seem to lump them all up in a single pile. But things are very different between, say, astronomy and medicine and their “alternative” counterparts. While both alts have huge amount of money involved guaranteeing their interest, I don’t think there’s nearly as much money – or at least private capital – involved in astronomy as there’s in medicine. Big pharmaceutical companies have time and again been shown to twist the research to their favour if not outright fabricate positive results. Heck, Merc even created a phony peer reviewed journal to tout their products.

    So while there’s little reason for astronomers to ‘hide evidence’ for astrology (if there was any), it’s not seemingly impossible that pharmaceutical companies might have conflicting interests when it comes to funding and presenting research about some new lines of healthcare.

  50. M. B. Cilek

    changing minds in the light of fresh data is totally acceptable..scientists have very dynamic minds (and sometimes pretty unstable) and their only weapon ıs analytical reasoning..and unfortunately sometimes, this reasoning is warped heavily away from objectivity, under the pressure of yielding a good theory within a reasonable time..do you remember Einsteins own words about his way of thinking ?? Contrary to his own equations which showed an expanding universe, he had defended a “static” one by introducing a “fudge factor” into the equations…and when he realized this much later he was quoted as saying “it was the biggest blunder of my life”..

  51. LittleJim

    @Joseph G;

    Dirt. Or dust. Very small rocks. Planets thrown out of their home solar systems billenia ago wandering the intergalactic abyss forever.

    Dark matter is basically stuff that either isn’t emitting on the EM spectrum itself or being illuminated by something shining on it or by other bits of matter (very small bits) slamming into it at a fair percentage of the speed of light and making it glow.

    The idea is that there’s a lot more of that stuff than originally thought. Enough to resolve the discrepancy in the equations, and therefore, a good candidate for further investigation.

  52. Nigel Depledge

    Mike (50) said:

    Big pharmaceutical companies have time and again been shown to twist the research to their favour if not outright fabricate positive results.

    While I know there to be clear evidence that negative results from clinical trials are rarely published, I have never seen any evidence that Pharma companies fabricate results.

    Full disclosure – I work in the biopharmaceuticals industry, and the site at which I work was bought last year by a Big Pharma company.

    What I do know is that if I were ever to fabricate results, I would be fired. A few years ago, a worker here was fired for making a fraudulent entry in a critical manufacturing document.

    If you’re going to throw around serious allegations like that, I think you should back it up with some evidence.

  53. Nigel Depledge

    @ Mike (50) –
    While I agree that astronomy vs astrology doesn’t really have a huge “customer” base and that medicine does, there are a couple of significant facts that you are ignoring:

    (1) : alt-meds are after the same customers as Big Pharma, i.e. everyone.
    (2) : Big Pharma are required by law in every civilised nation to prove that their products are (a) at least as safe as the best existing treatment, and (b) more effective than a placebo with statistical significance in a large double-blind trial.

    This is an oversimplification for the sake of argument, of course, but the point remains: Big Pharma are required by law to carry out trials that cost hundreds of millions of dollars to test their products in order to get a licence to sell the stuff. What regulation does alt-med have? In some cases, the same as food supplements (i.e. they may be required to prove that it contains what it says on the label), but in many other cases, none at all.

    So, alt-med practitioners are chasing the same customers as Big Pharma, but don’t have to make even 0.1% of the investment that Big Pharma companies are required to make. Think on that the next time you compare alt-med with Big Pharma.

    One other thing I agree about – that Pharma companies do indeed have a conflict of interest if a clinical trial returns a negative result. However, if the trial was properly designed in the first place, a repeat of the trial should return the same result.

    While there may be many flaws in the existing system, it is far easier to whine about “Big Pharma” than to propose a realistically workable and better alternative.

  54. Nigel Depledge

    Little Jim (52) said:

    Dirt. Or dust. Very small rocks. Planets thrown out of their home solar systems billenia ago wandering the intergalactic abyss forever.

    Dark matter is basically stuff that either isn’t emitting on the EM spectrum itself or being illuminated by something shining on it or by other bits of matter (very small bits) slamming into it at a fair percentage of the speed of light and making it glow.

    Erm … would not such dust show up in the far IR?

  55. M. B. Cilek

    as far as I know, maximum possible amount of such dirt, dust and gas together with a maximum poss amt of MACHOS (neutron stars, brown dwarfs, black holes etc..) are taken into account.. but the amount of matter needed is still an order of magnitude higher, if not more..that is why Dark Matter is invented…

  56. Bryan Feir

    Nigel Depledge (48) said:

    as far as I am aware, Einstein never accepted the basic ideas of quantum mechanics

    All the more ironic given that the work for which Einstein won the Nobel prize, his paper on the photoelectric effect, laid a lot of the foundations for quantum mechanics…

  57. Donovan

    I think you understated the heroics that will happen at the Astronomical meeting, Phil.

    After some scientists find and accept the truth of non-collision theory, they will try to share their love of the new idea with the collision theorists. The Ns and the Cs will find it hard to agree, the discussion will become heated, and the Ns will be banished. Later, the Ns will return wielding many strong telescopes of iron and carrying thick clipboards, impenetrable to the pens launched from the Cs’ rubber bands. The Ns will take back the convention hall and drive the traditionalist Cs from Seattle’s business district. But the Cs will survive and plot their revenge in the hotel lobbies, stewing in anger over cold coffee and stale doughnuts. The struggle will remain, heated by the burning furnaces of ad hominem debates, for tens of thousands of ten-thousandths of a University’s pre-approved per-diem. With no resolution possible and the world growing too small for such opposing dichotomies of astrophysical theories, the citizens of both sides, well, they don’t really care, but still must be defended in the name of reasonable assumptions in accordance with observation and natural laws. The mighty tour buses roll through the battle field, the scientists on both sides pull out their calculators, waving them in the air, both declaring victory by calculating the odds with all relevant variables. But the exchange of bizarrely inappropriate quark insults ends when King C’s crown of paper clips crashes to the pavement and he screams in agony as the atomic wedgie decides the victory for the Ns.

    The way you describe it, it sounds like people just talk it out and accept the whole thing on reason and evidence. Pfft.

  58. Joseph G

    @Donovan:
    I thought you were serious for a sec :)

  59. Anchor

    The paradigm of triggering AGN by galaxy mergers has always been a general one and tentative and most who invoked it have not limited themselves exclusively to it as a means of delivering fuel to the core. There are many ways of fueling central SBHs, and mergers between galaxies is but one general mechanism which remains plausible.

    But I have a nit to pick with how they subjectively characterize galaxies in 3 categories, as exhibiting evidence of a recent merger: 1. “No Distortion”, 2. “Moderate Distortion”, and 3. “Heavy Distortion”.

    The problem is that some merger events – perhaps most, if one counts the far more frequent kind involving a big galaxy absorbing a small dwarf system – don’t produce any discernable tidal distortion at all, while a fair number of examples that appear to be distorted may not in fact be due to a merger but instead may be attributable to another system that lies on or along the line of sight, to the foreground or background, making it appear distorted. The latter circumstance is much more common than one might at first expect, since galaxies are naturally gregarious and are commonly grouped in relatively population-dense clusters where superpositions are statistically more likely. (For example, an observer situated in certain places outside of our galaxy could mistake our Milky Way to be “heavily distorted” because of the nearby LMC, while as seen from other directions our galaxy would seem to be nearly distortion-free, with the LMC and SMC unambiguously separated from it). Dwarf systems absorbed into the core (a MERGER event!) can activate a nucleus without ever distorting the system as a whole.

    The SUBJECTIVE characterization of systems in those categories (yes, by experts) strikes me as too haphazard and weak to support a firm conclusion about a NON-correlation with AGN activity. Merger or absorption is still a perfectly serviceable mechanism for delivering fuel to the central SMB, as are instabilities that can arise in or near the core without external encouragement. Star-forming regions near the core can produce supernovae shocks that can fuel the nucleus as well. There are many scenarios that can fuel central SMBs.

    But it always bothers me whenever people pull the either-or card and insist that scientists must come down exclusively in favor of one mechanism or hypothesis or another as THE explanation at the expense of others that might well also play a significant role. This business isn’t a popularity contest or an election selecting a favorite candidate. Nature is not nearly so finicky or squeaky-clean as our ideals demand. I think this ‘study’ isn’t nearly what it’s cracked up to be.

  60. Anchor

    In other words, another conclusion that may be drawn from this ‘study’ that is equally consistent is that not all AGN are the result of mergers. But we already knew that…or at least those of us who don’t religiously pigeon-hole our paradigms knew it. The ‘evidence’ in the study is weak and does NOT necessarily remove galaxy mergers or absorptions as a potential means of delivering fuel to central SMBs.

  61. Messier Tidy Upper

    @3. Dave w :

    While science is excellent at abandoning everything it once held dear with no regrets, this kind of ‘brand loyalty’ does still seem to exist to a small degree. So while you probably won’t get many people refusing to accept relativity in favour of good ol’ Newtonian gravity, there still seems to be an alarming number of people who can’t let go of Pluto being planet #9.

    It is really a whole other topic but, in fairness, there are a tonne of valid reasons why the recent IAU definition of the word “planet” which was deliberately & dubiously foisted upon us all solely to remove Pluto and the other ice dwarf type planets from being considered “proper” planets along with the rock dwarfs and gas giants is ridiculously wrong. :-(

    The current downright illogical and dumb IAU definition is, I think, one of the mistakes of current science that will, hopefully, be corrected sooner rather than later and will go down in history as a temporary silly aberration.

    I think the best definition – the one originally proposed and which far better fits logic and Occams’ Razor and rational understanding – is that a “planet” is an object which is gravitionally rounded, never self-luminous via nuclear fusion and is not directly orbiting another planet. It’s that simple &clear-cut really.

    Thus Pluto counts as a planet along with Ceres, Haumea, Sedna, Quaoar, Eris & many others. Planets come in three main types : the gassy like Jupiter, the rocky like Earth & the icy like Pluto. :-)

  62. MaDeR

    For me, this is simple. As every human, any sciencist also have their biases, favorite ideas etc. But scientific method and peer review (you know, PEER, like in colleagues, other people with same job and interests and knowledge) should overcome any personal or individual bias, given time and sufficiently large amount of people that cross-controll and cross-verify each other.

  63. CB

    “Is there any known kind of matter that doesn’t interact strongly with EM radiation in SOME way??”

    Yes. They’re called neutrinos. They only interact via the weak nuclear force, and gravity. Because of this, they can pass through enormous amounts of ordinary matter without coming close enough to a single atomic nucleus to interact. It takes a gigantic detector (Ice Cube neutrino observatory is a cubic kilometer in size) to have a decent chance of seeing an interaction out of the billions of neutrinos that are passing through our planet in any given instant.

    One of the primary hypothesized particles to explain Dark Matter would be a more massive relative of the neutrino. This hypothesis actually comes from a different theory, not DM, and is called the neutralino. There are projects active right now that are attempting to find out if this particle exists. So it is not proven, but particles with similar (and probably to you seemingly very strange) properties are known to exist.

    And while I welcome anyone to come up with an alternative explanation, it would be pretty difficult to do so without resorting to something like the neutralino. You can’t just tweak gravity a bit and explain gravitational lensing in the complete absence of any electromagnetically visible matter, or matter than appears to have passed through an entire galaxy without being slowed down by gas clouds, etc. The MOND guys gave a serious go at it, they really know what they’re doing, and while they did pretty good with galactic rotation even they eventually had to add some kind of weakly-interacting dark matter in order to explain observations.

    So forgive me if I’m skeptical of someone claiming to be able to get rid of the need for DM using simple physics. Forgive me if it seems to me that the ones who dismiss Dark Matter because it seems made up (and aren’t aware of neutrinos), and liken it to the Aether, are themselves the ones guilty of lazy thinking and being stuck in their ways, refusing the new information because it’s too weird or something.

    And forgive me if I’m simply sick of people saying that well, eventually the evidence and ‘truth’ will prevail in a way that presumes truth will favor their interpretation, despite their being no evidence for it turning out that way and plenty to the contrary.

    P.S.
    @Messier Tidy Upper:
    I don’t really care what you call it, but there’s a 5 order of magnitude difference between the IAU-defined “planet” that has cleared its orbit the least, and the dwarf planet that has cleared its orbit the most. We’re talking the difference between the planet being over 10,000 times the mass of everything else in its orbit not counting direct satellites, and the dwarf planet being 1/3rd the mass of everything else.

    That distinction is clear, obvious, and deserves to be recognized. I don’t care what you call it; “Uber planets” and “regular planets”, fine. But Earth, Mars etc are Uber Planets, and Ceres and Pluto are Regular Planets.

  64. Nigel Depledge

    @ CB (64) –
    I guess that’s why they’re called WIMPs, or Weakly-Interacting Massive Particles (i.e. they interact with other stuff through gravity and the Weak force, but not EM or the Strong force).

    Now, if only we could discover some particles that interact only through the Strong force and gravity, I have a name for them ready to roll…

    SIMPles.

  65. M. B. Cilek

    @ CB (64)
    “So forgive me if I’m skeptical of someone claiming to be able to get rid of the need for DM using simple physics. Forgive me if it seems to me that the ones who dismiss Dark Matter because it seems made up (and aren’t aware of neutrinos), and liken it to the Aether, are themselves the ones guilty of lazy thinking and being stuck in their ways, refusing the new information because it’s too weird or something.”

    I forgive you, dont worry..
    just to clarify the matter: My theory explains flat galaxy rotation curves without resorting to Dark Matter..I do not believe in DM in general as I have said, but that is another issue and the theory adresses only one of the “supposed” evidences for DM (which is the most heavyweight I believe).
    The physics and mathematics is really simple !! you see, you cannot solve a problem even if you have the most sophisticated tools available, if your approach is wrong from the start..
    we are all aware of neutrinos and neutralinos and follow the experiments deep underground just to spot a handful of them..aether is of course a completelety different historical concept which has been abondened long ago but has started finding serious interest lately..I believe there was an ambiguity on ur side there..
    and last of all, lazyness may actually be defined as sitting idle and doing nothing which seems to be the case in DM theory, as so many scientists spend so many valuable man-hours and precious resources despite there is no viable clue yet, for DM to exist..all “evidences” suggested might be explained by various phenomena as I have stated earlier..Good luck to all DM fans in their relentless search to prove it..beam me up Scotty :))

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