Less evidence of dark matter in early universe


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The uncertainty of science: Astronomers have discovered less evidence of dark matter surrounding galaxies in early universe.

Stars in the outer regions of some far-off galaxies move more slowly than stars closer to the center, indicating a lack of dark matter, astronomer Reinhard Genzel and colleagues report online March 15 in Nature. If confirmed, the result could lead astronomers to reconsider the role dark matter played in early galaxy evolution and might also offer clues to how nearby elliptical galaxies evolved.

In contrast with these distant galaxies, stars orbiting on the outskirts of the Milky Way and other nearby galaxies move too fast for their velocities to result only from the gravity of gas and stars closer to the galactic center. If visible galactic matter is embedded in a cloud of invisible dark matter, though, gravity from the invisible matter can explain the high stellar velocities. Using stars’ orbital velocities in nearby galaxies as a reference, astronomers expected that stars in galaxies farther away would behave similarly. “Turns out that is not the case,” says study coauthor Stijn Wuyts of the University of Bath in England.

In other words, scientists at this moment really have no idea what causes the faster rotation in the outskirts of modern nearby galaxies.

17 comments

  • PeterF

    Can anybody explain how the time dilation caused by gravity because of close proximity to a massive object (The galaxies they orbit and the mass of the stars themselves) effects the observed speed of those stars?
    From what I understand, an observer on a planet will observe objects in microgravity moving faster than they really are. Someone at the event horizon of a black hole should “see” everything else in the universe zipping around at near-light speed.

  • wayne

    PeterF–
    I was initially going to say– “the light cones, curve back on themselves,” but upon further reflection I’m not sure I’m understanding your question, could you expand on that a bit?

    This sounds like a Reference Frame question. (I only play an astrophysicist on the Interweb.)

  • Mitch S.

    This could fuel “Dark Matter deniers”.
    Why don’t they take a cue from mainstream climate scientists and “correct” the data to fit the theory?

  • Orion314

    Dark Matter, Dark Energy, BAH!
    IMO, just two new terms to obfuscate the fact we dont’ seem to know jack about gravity. Gravity. The holy grail of physics. If we ever really get our arms around that force, it will change everything. What’s the range of Gravity?, what’s the speed of gravity? Who knows?, your guess is as good as anyone. Please spare me the einsteinium lip service, he didn’t know any more about the mysterious G than anyone else.. Throwing off the explanation of space time curvature as an answer is like saying a blue bird is the same as a 747 cause they both have wings…BAH!!!!
    A theory I find interesting is that there are possibly two or more types of Gravity, type A & B , short range and long range. Perhaps, some out of the box thinking re: galactic rotation speeds and structure might be well be of service if they were to drop the idea that gravity is an unchangeable constant. After all , they have no problem viewing time as a variable.

  • LocalFluff

    @PeterF
    I love to watch lectures about that topic. There are many figurative illustrations of the currently best theory. But when pressed a bit, the cosmologists regress to math. n+F=1.07547347. That doesn’t make me feel any the wiser. So I’m afraid I have little hope for you,m and me, to ever really understand anything. Maybe there’s an error in the imagined concept “explain”?

  • Dick Eagleson

    Orion314,

    I’m also at least somewhat dubious about dark matter and/or dark energy being actual things. I was even more dubious about so-called String Theory back when that seemed to be the hip flavor du jour at the other end of the size scale.

    But the apparent success of recent gravity wave detection experiments appears to answer at least one of your questions. Gravity does seem to have a speed and that speed seems to be the same as light. That means that if, somehow, Sol was to instantly vanish, Earth would continue in its elliptical orbit for about eight minutes before zipping away into the outer darkness in a straight line tangent to the point where the last of Sol’s en-route gravity arrived.

    One doesn’t have to posit two or more types of gravity to fix the conundrum current astrophysics seems inclined to solve via assuming the existence of dark matter/energy. There are at least a couple theories out there to the effect that gravity is a single force, but doesn’t work precisely as Newton posited via an inverse-square law, but through a slightly different mathematics that very closely matches inverse square at interplanetary and even interstellar distances, but diverges significantly from it at longer distances – like from the center to the edge of a galaxy and at intergalactic distances. At least one of these theories is also said to be compatible with General Relativity for whatever that may be worth.

    You’re quite right that there’s plenty we don’t know. I’m not very confident these questions will be decisively answered within my probable remaining lifespan. Them’s the breaks.

  • Edward

    I tend to remain skeptical until I see real evidence. Thus, the hypotheses of Dark Matter, Dark Energy, and String “Theory” are only hypotheses, to me.

    Dark Energy is not needed if astronomers have misunderstood the distances to their reference objects. But it would be an explanation of how the universe could behave as we have derived that it does.

    Dark Matter likewise could explain why Galaxies behave as we see them behave, but like many other unknown phenomena, there could be something else happening that we have yet to understand.

    String Theory is merely another way to look at the fundamental structure of the universe. There is no real mystery that it solves, as Dark Energy and Dark Matter are supposed to do.

    Even the hypothesis of Anthropogenic Global Warming has more evidence that it is actually the Earth recovering from the Little Ice Age than that human activity drives the global temperature. Even the Piltdown Man had more and better evidence than AGW has.

  • LocalFluff

    There’s no easy way out of “dark physics”. It fits with galaxy rotation and gravity lensing. With observations and the crazy but simple theory. Astronomers have unwillingly adapted to the Darkness. Just assume it and everything makes sense. That and inflation, even worse than darkness. If it solves the equation, accept it. After rubber spacetime and quantum improbabilities, why not this too?

    Relativity and Quantum theory are the two big poles in physics. But inflation and dark matter and even Big Bang were just added later on, and don’t fit with either of those theories afterwards. Cosmology is bound to change.

  • wayne

    Sir Roger Penrose:
    “Fashion, Faith, and Fantasy in the New Physics of the Universe”
    https://youtu.be/kS1A5dJdOvI
    (1:43:05)

    “What can fashionable ideas, blind faith, or pure fantasy possibly have to do with the scientific quest to understand the universe? Surely, theoretical physicists are immune to mere trends, dogmatic beliefs, or flights of fancy? In fact, acclaimed physicist and bestselling author Roger Penrose argues that researchers working at the extreme frontiers of physics are just as susceptible to these forces as anyone else. In this provocative book, he argues that fashion, faith, and fantasy, while sometimes productive and even essential in physics, may be leading today’s researchers astray in three of the field’s most important areas—string theory, quantum mechanics, and cosmology.”

  • Dick Eagleson

    Yup. Time to quote J.B.S. Haldane again:

    “The Universe is not only queerer than we imagine, it is queerer than we can imagine.”

    If I may wax Rumsfeldian, the list of currently “known unknowns” is daunting enough. But it seems likely that the number of “unknown unknowns” may be appreciably larger.

    Perhaps the nascent, but rapidly progressing, field of gravity wave astronomy will yield some paradigm-shifting insights soon enough for us to hear about same while we’re still above ground.

  • wayne

    Dick– good stuff.

    “Matter tells space-time how to curve, and curved space-time tells matter how to move”

    I as well think the “dark energy” and “dark-matter” monikers are counterproductive. It’s way too akin to “insert magical thing, here.” And sorta similar to the silly-string folks inventing 23 dimensions, or the Inflation-people with their “insert 50 E-folding’s at this point” stuff.

    (That being said, I only play a Cosmologist, on the Interweb.)

  • Edward

    LocalFluff wrote: “Just assume it and everything makes sense. … Cosmology is bound to change.

    Correct on both counts. If the model works to explain the observations, then the only reason to change the model is when evidence arises that the model is wrong. That is when cosmology changes.

    Please remember that the flat Earth model worked for many centuries to explain observation, and it worked for everyday life. Later observations raised doubts that the flat Earth model was correct and cosmology has been changing ever since, eventually allowing for us to send probes to other worlds in order to further explain the universe.

    However, making up a solution without direct evidence, just to explain a mystery, is not the best science. It leads to ghosts to explain strange sounds, gods to explain volcanoes, and cosmological constants to explain stationary universes.

    At best, you can call these explanations “hypotheses.” Multiple hypotheses can fit any given observed phenomenon, but until you collect evidence that one may be correct, you cannot begin to conclude that it is correct. Occam’s Razor may be used to suggest that some are more likely than others, thus those would be the early ones to investigate, but conclusions without evidence are not scientific conclusions.

    Doyle’s character Sherlock Holmes said, “How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth?”

    This is a clever saying, but it only works when you have complete information. If whatever remains leaves unknowns, then the unknowns may contain additional clues to the correct answer. Without those additional clues, you may derive an incorrect truth. “Must be the truth” turns into “may be the truth.”

    To give an example of all this, Newton’s laws of motion created a model that worked for all of our observations, until Einstein did a thought experiment and hypothesized a relative universe. Experimental observation after observation confirmed his hypotheses over the course of a century. Now relativity is a theory, where a theory is an explanation of a phenomenon that remains subject to modification as future observations are made.

    Where relativity is concerned, we are mostly down to Dick Eagleson’s and Rumsfeld’s unknown unknowns, just as in Newton’s time no one knew that they didn’t know the effects of relativity.

    Meanwhile, from the posted article:
    ‘Dark matter must be there,’ Genzel says. ‘Without it, there are no galaxies and no “us,” so we need to understand its nature and distribution to explain what we see in the universe.’

    Dark matter must be there. Without it there must be some other, unknown, explanation. Since we have no other explanation, we conclude that the truth is (rather than “may be”) that dark matter must be there.

  • Orion314

    Dick,
    re:”wax Rumsfeldian” love the term! I remember just b4 9-11, when he said about the pentagon corruption audit and a
    1 trillion dollar theft , we don’t know what we don’t know…” just when we were about to get to the good part and
    ‘follow the money” 9-11 is the new focus. “We don’t know what we don’t know’…obvious to everyone on this site, yet , a revelation to the rest of the world, most of whom still, embrace the dark ages.

  • Dick Eagleson

    Edward,

    Very well put.

    I regard Relativity as the greatest human intellectual achievement to-date and Einstein, therefor, as the greatest thinker. I’ve long thought the reason we are still, as a species, short of having arrived at a Grand Unified Theory of Everything is that doing so requires the arrival of another human mind as good or better than Einstein’s.

    How long do we probably have to wait for Einstein 2.0? Perhaps no more than a century or so. The only roughly Einstein-class intellect to emerge in the ancient world was Archimedes. We got our next one most of two millennia later when Leonardo da Vinci was born. Less than two centuries after that, we got Isaac Newton. Einstein came along a bit over two centuries after Newton. It’s been nearly a century and a half since Einstein’s birth.

    World human population was probably no greater than 150 million in Archimedes’s day. It had tripled or more by the time Da Vinci and Newton came along. Tripled again before Einstein appeared. Quintupled between Einstein’s birth and the present.

    We probably don’t have more than another century to wait. It’s easily possible Einstein 2.0 may already have been born. Based on the past incidence of super-genius vs. human population, one could argue that Einstein 2.0 is overdue even now.

  • Edward

    Dick Eagleson wrote: “I regard Relativity as the greatest human intellectual achievement to-date and Einstein, therefor, as the greatest thinker.

    What a thought. Dick, I like you’re thinking.

    Perhaps it is because I am an engineer, but up until now I had regarded Thomas Edison as the greatest mind, despite his only real accomplishment having been to invent the think tank. From that one invention came many inventions, developed by others, that improved our lifestyles, and Edison received eternal credit for their work. Well done Edison.

    I believe that there are two things that were instrumental in the growth of human population: the agricultural revolution and the industrial revolution.

    Crop rotation was an invention (13th century) that allowed fields to be worked every year, rather than laying fallow every other year. This allowed for additional food production and population growth, which also allowed England to become the world power, United Kingdom. I think that had there not been an English law requiring fields to lay fallow every other year (repealed only about a century ago), England would have advanced much faster and sooner.

    The industrial revolution (18th century) happened because the extra food allowed a larger population that had nothing better to do than build upon the results of experimental science to invent many useful things. Until a couple of hundred years ago, virtually everyone lived in poverty, except for nobility, but the industrial revolution is bringing the majority of everyone out of poverty. Even 19th century nobility lived in poverty relative to today. Industry even made farming less labor intensive, freeing up even more people to be factory workers, artists, scientists, and inventors.

    Thus, it is not only the increased population that improves our chances for an Einstein 2.0, but it is our ability to have an ever greater percentage of our population available to be great thinkers as a profession.

    I would also include Galileo in your list of great minds. After two millennia, he reintroduced experimental physics, giving birth to the scientific method. Aristotle gets credit, from me, for having set back human advancement by a couple of millennia, because he and his contemporaries chose theoretical science over experimental.

    They had the hubris to assume that a superior brain could figure out the universe through thought alone. To paraphrase: “I think, therefore I am smart enough to figure out the gods.” He was polytheist.

    Don’t get me wrong, Dick, this rant about experiment beating out thought should not be taken as me not liking the way you think.

  • Dick Eagleson

    Edward,

    Didn’t mean to imply there weren’t a lot of other very bright people throughout history. There certainly were. Galileo, Copernicus and Kepler were certainly among them. Tycho Brahe too.

    I wouldn’t credit Edison with inventing the think tank. What he invented was organized, systematic, purposeful R&D as a paradigm for moving the state of a given art forward. That was actually a lot more important than the invention of think tanks.

    There is evidently a decent case to be made that agriculture was a consequence of humans inventing beer. Civilization was, in turn, invented as a consequence of no longer being able to live a nomadic existence when one had to stay with one’s crops.

    Food surplus in Europe during the late Middle Ages and the Renaissance was due to a number of things, not least the introduction of entire new crops such as potatoes and corn from the New World. Even before the discovery of the New World, the Medieval Warm Period did a lot for food production, lengthening growing seasons and making it possible to grow given crops at higher latitudes.

    The benefits of the Industrial Revolution barely need recounting – except to the deluded Neo-Druids who style themselves Deep Ecologists, perhaps. One problem with pervasive food surpluses and the conquest of many infectious diseases is that a lot of really stupid people aren’t weeded out of the human gene pool early in life anymore.

    I think you’re a little too hard on Aristotle. He actually did a lot of empirical work during his life. The scientific method hadn’t been worked out yet, but he traveled and looked at things. He believed in observation, but he didn’t have the benefit of the notion of experimentation. Still, he wasn’t just sitting upstairs thinking deep thoughts unmoored to reality. He got some important things wrong – like the notion that speed of fall increased with weight. Less consequentially, he also thought sponges were plants. But the problem was less Aristotle than the cult of Aristotle that developed after his death and lasted for centuries.

  • Laurie

    Good thing they had beer to compensate for the stupidity …

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