Can Primordial Black Holes Alone Account For Dark Matter? 135
thomst writes: Slashdot stories have reported extensively on the LIGO experiments' initial detection of gravity waves emanating from collisions of primordial black holes, beginning, on February 11, 2016, with the first (and most widely-reported) such detection. Other Slashdot articles have chronicled the second LIGO detection event and the third one. There's even been a Slashdot report on the Synthetic Universe supercomputer model that provided support for the conclusion that the first detection event was, indeed, of a collision between two primordial black holes, rather than the more familiar stellar remnant kind that result from more recent supernovae of large-mass stars.
What interests me is the possibility that black holes of all kinds -- and particularly primordial black holes -- are so commonplace that they may be all that's required to explain the effects of "dark matter." Dark matter, which, according to current models, makes up some 26% of the mass of our Universe, has been firmly established as real, both by calculation of the gravity necessary to hold spiral galaxies like our own together, and by direct observation of gravitational lensing effects produced by the "empty" space between recently-collided galaxies. There's no question that it exists. What is unknown, at this point, is what exactly it consists of.
The leading candidate has, for decades, been something called WIMPs (Weakly-Interacting Massive Particles), a theoretical notion that there are atomic-scale particles that interact with "normal" baryonic matter only via gravity. The problem with WIMPs is that, thus far, not a single one has been detected, despite years of searching for evidence that they exist via multiple, multi-billion-dollar detectors.
With the recent publication of a study of black hole populations in our galaxy (article paywalled, more layman-friendly press release at Phys.org) that indicates there may be as many as 100 million stellar-remnant-type black holes in the Milky Way alone, the question arises, "Is the number of primordial and stellar-remnant black holes in our Universe sufficient to account for the calculated mass of dark matter, without having to invoke WIMPs at all?"
I don't personally have the mathematical knowledge to even begin to answer that question, but I'm curious to find out what the professional cosmologists here think of the idea.
What interests me is the possibility that black holes of all kinds -- and particularly primordial black holes -- are so commonplace that they may be all that's required to explain the effects of "dark matter." Dark matter, which, according to current models, makes up some 26% of the mass of our Universe, has been firmly established as real, both by calculation of the gravity necessary to hold spiral galaxies like our own together, and by direct observation of gravitational lensing effects produced by the "empty" space between recently-collided galaxies. There's no question that it exists. What is unknown, at this point, is what exactly it consists of.
The leading candidate has, for decades, been something called WIMPs (Weakly-Interacting Massive Particles), a theoretical notion that there are atomic-scale particles that interact with "normal" baryonic matter only via gravity. The problem with WIMPs is that, thus far, not a single one has been detected, despite years of searching for evidence that they exist via multiple, multi-billion-dollar detectors.
With the recent publication of a study of black hole populations in our galaxy (article paywalled, more layman-friendly press release at Phys.org) that indicates there may be as many as 100 million stellar-remnant-type black holes in the Milky Way alone, the question arises, "Is the number of primordial and stellar-remnant black holes in our Universe sufficient to account for the calculated mass of dark matter, without having to invoke WIMPs at all?"
I don't personally have the mathematical knowledge to even begin to answer that question, but I'm curious to find out what the professional cosmologists here think of the idea.
typo in title (Score:1)
Pirmordial
Editors, the word you're looking for is primordial.
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Re:typo in title (Score:5, Insightful)
The main alternative to WIMPs are MACHOs [wikipedia.org], and black holes have long been candidates for dark matter. The problem is that they would need to have five times more mass than all the "ordinary" matter in the universe, and there is little evidence for that. For instance the amount of gravitational lensing that is observed is way less than would be expected. Dark matter appears to be more evenly distributed in galaxies and not just in the "halo". Yet we don't observe that many black holes passing through gas and dust clouds or interacting with regular stars.
TFA says that there may be 100 million black holes in our galaxy, and that may sound like a lot, but it is actually nowhere near enough to account for all the dark matter. Even if they had 10 solar masses each (unlikely), that would still be less than 1% of the mass of the galaxy's "ordinary matter", when it should be 500%.
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If you get rid of dark energy, you eliminate the need for dark matter as well.
Current theory about universe involves more space appearing out of thin air, causing expansion. (More vacuum!).
Instead what should be examined is what happens to light traveling through immense amount of vacuum. We have discovered unexpected characteristics of vacuum, there may be more. It is possible that redshifting occurs through extended vacuum interaction and the output is that occasionally higher energy photons are conver
Re:typo in title (Score:5, Informative)
There is evidence for more matter than visible in the galaxies, which is completely independent of Dark Energy. The most prominent evidence is the rotational characteristics of the outer parts of a galaxy. The stars there are circling the center of the galaxy much faster than expected from a Keplerian point of view. Instead of falling with r^2/3, as Kepler's Third law of motion predicts, the speed of stars remains roughly constant if you get to the outer parts of the galaxy. This means that the mass of the galaxy inside the respective orbits of the stars has to grow much faster than the mass from the additional stars within outer orbits.
(Be careful not to confuse the speed of stars on their orbit with their angular speed! A star twice the distance from the center of a galaxy needs twice the time to complete a circle than a star closer to the center. Thus the angular speed halves, but the linear speed on the orbit keeps the same. With Kepler's Third law, we would expect the time to complete an circle for the outer star to be 2*sqrt(2) of the time the inner star needs.)
Re:typo in title (Score:4, Insightful)
Re:typo in title (Score:5, Informative)
Not really. There's areas of mass where there's little to no ordinary matter, where galaxies have collided and the gas has slowed down, but the dark matter has kept on going. This is demonstrated by gravitational lensing effects of the invisible mass. This doesn't really fit with MOND theories.
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I agree that the separation of luminous gas from gravitational lensing in for example the Bullet Cluster (https://en.wikipedia.org/wiki/Bullet_Cluster) is strong evidence that dark matter is something other than ordinary matter, be it in black holes or not.
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If mass can deform space, is it possible that those deformations could continue to exist after the mass has diverged?
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The waves represent a rapid change in the shape of space, right? Gravity isn't instant but changes in gravitational state travel at something like the speed of light. And the waves actually represent a temporary fluctuation before returning to an earlier state.
I'm thinking more in terms of space being so distorted by a mass that even once that mass has somehow been removed or lessened, the space where it once was remains distorted. I think there is a presumption that space is perfectly elastic, compressing
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Check this out and, if you would, please provide some comment.
http://thedaily.case.edu/rotat... [case.edu]
It seems to put a new spin (haha!) on the relationship between normal matter and dark matter and the rate of spin in galaxies.
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Just don't forget that rotational speed of Galaxies and Galaxy clusters is AN evidence for Dark Matter, but not the only one.
Gravitational Lensing provides the second major evidence for some (electromagnetically) unseen source of gravity, it also provides evidence that Dark Matter is just a "scaling problem" in our theory of gravity (AR)... google for "Bullet Nebula".
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If we're saying this gravitational lensing is caused by the same type of matter that makes galaxies spin too fast, that would seem to rule out black holes, since they wouldn't separate from stars in a galaxy collision.
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What separated from the stars in the Bullet Cluster is the gas and dust, which apparently are the largest amount of visible mass. I'd expect much the same effect from lots of small black holes as from WIMPs - in this case, anyway..
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You seem to know what you're talking about. Kepler's "laws" describe two bodies in orbit around each other, with one much more massive than the other, and at a substantial distance. Obviously (well, I _guess_ it's obvious), the rotation of gaseous bodies (like the Sun) is different; an hydrogen atom in the photosphere is not in _orbit_, so its behavior is not described by Kepler's (or Newton's) laws.
While it's a long ways to the next star in the arm of a galaxy, it's still not quite the same as if our Sun
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Normally in science the simpler the answer that fits the given data is considered the most likely. Given Dark Matter and Dark Energy are more or less scientific terms for paranormal activity ( just so people just don't go thinking it is cause by ghosts ) but right now they are a name of something, we are not quite sure how to measure and observe, it is just a variable if filled into the equation seems to fit the data that we observe in the universe.
Now as we learn more and collect more data and get better
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There's nothing paranormal about Dark Matter or Dark Energy. Dark Matter is matter that has gravity but doesn't interact electromagnetically. We actually have an example of such matter in the neutrino, although what we're observing isn't what neutrinos would do.
Like many things in science, they're a name for something we haven't been able to observe more directly. Are you familiar with how we found Uranus and Neptune? Astronomers observed anomalies in the orbit of Saturn, and figured that these could
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Yup, the observed dark matter isn't neutrinos, but neutrinos are dark matter by the definition of not interacting electromagnetically.
Neutrinos are weird. Back when we thought they moved at lightspeed, they were understandable. Another massless particle moving at c. The reason we know they don't is that they change flavor, and hence have to be experiencing time . Other than that, we can't tell the difference. In a supernova, the neutrinos show up a few hours early because the light has to make it ou
Need Dark Matter AND Energy (Score:3)
If you get rid of dark energy, you eliminate the need for dark matter as well.
That's completely wrong. Dark energy is needed to explain the acceleration in the expansion of the universe. Matter - either dark or ordinary - is gravitationally attractive and can never cause the expansion to accelerate. Dark Matter is needed to explain the "clumpiness" of the Cosmic Microwave Background, the rotation curves of galaxies and gravitational lensing observations e.g. bullet cluster. Black Holes have been considered a dark matter candidate before (MACHOs) and have been ruled out.
I think th
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Both astrophysics and particle physics are in chaos now.
No, we are not. There are two unexplained phenomena at galactic and intergalactic scales but either could easily be explained by adding a new field to the physics we already have. This is no more 'chaotic' than it was before we found the Higgs boson or the top quark.
At the same time, the energy level of the newly discovered higgs boson has trashed decades of string theory.
That is simply not true. The Higgs mass is at the upper end of the allowed range for SUSY but it is still in the allowed range to avoid vacuum instability. I believe that there were some papers that suggested that the mass was closer to this l
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Photons don't experience time. Of course nothing happens to them. You cannot alter a photon, only create new ones. The act of creating new ones leaves traces.
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But, if there were black holes scattered between galaxies, that would be a different story.
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Just use unsalted butter next time.
Well, let us look at the ---primordial--- pie. (Score:3, Informative)
See this link: Content of the Universe 2016 [nasa.gov]
So, the problem is that there is so much of it, you would think we'd see it perturbing stallar orbits more, it it were concentated in many, many discrete points of star gravitational influence. There would be a lot more stars orbiting pulsar type objects, perhaps?
A real cosmologist would know the odds of the galaxy looking the way it does if all the extra mass were in scattered black holes of a certain size. Probably low.
Re:No (Score:5, Informative)
Re:No (Score:5, Interesting)
It is annoying having lazy clueless laymen's idle speculations being promoted to being a slashdot article.
Dark matter seems particularly to attract these sorts of totally uninformed wild guesses being thrown out to "solve" one of the deepest questions in modern physics and cosmology.
To all and sundry out there - if you just thought of it then the answer is "no". All possible known candidates have been thought of and eliminated. Whatever dark matter and dark energy are, it is nothing we currently understand. Even most promising theories seem to be failing at present.
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"I've disproved climate change. You see, climate scientists forgot to take the Sun into account."
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Re:just wait (Score:5, Funny)
Don't count on it.
“There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.
There is another theory which states that this has already happened.”
Douglas Adams, The Restaurant at the End of the Universe
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It was also proved by Disaster areas accountant, that space is not metely curved, it is totally bent, hence the evidence of dark matter.
I think no, not that simple (Score:5, Informative)
https://phys.org/news/2015-03-... [phys.org] http://www.sciencemag.org/news... [sciencemag.org] If dark matter were simply some existing form of baryonic matter, even if trapped in black holes, then a phenoma like this where dark matter halos separate from collided galaxies and behave under different rules to continue on their existing path should not be possible at all, because it, like all the other ordinary matter involved, it should have followed the same paths gravitationally bound.
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But why would the black holes be distributed significantly differently than stars, and have "outer" orbits?
Most visible stars are caused by relatively recent compressions and/or concentrations of gas, and the concentration is heavier toward the center of a galaxy. Thus, relatively speaking, there could be more black holes outside the visible disk of a galaxy than stars.
But this would also imply the majority of black holes did not form from stars, at least not in the way we see them form now. If the black-ho
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Some probably "too simple" questions... (Score:1)
What happens to all the matter sucked up by black holes?
If some of the mass is converted to energy inside the black hole, could that affect our perception of the mass of those black holes?
Essentially, would an amount of mass that is being converted to energy inside the black hole affect the amount of mass we attribute to a black hole from our vantage point on the outside of said black hole?
Would it behave like some sort of "anti-gravity" effect, or would it act as a "gravity enhancing" effect?
I'm just a
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Matter doesn't get converted to energy when it drops into a black hole, it gets mired in time. It's mass is instantaneously added to the mass of the whole though. Then again, over a very very very long period of time, the black hole will evaporate due to radiating Hawking Radiation. If you reason that everything will eventually be swept up by black holes, then it's possible that this radiation is the ultimate fate of everything. Unless the expansion of the universe prevents new black holes from forming at s
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That's not quite right.
There are three types of stuff involved in the Bullet Cluster collision: stars, gas, and dark matter. The stars are the smallest fraction of the mass, the gas is a larger chunk of it, and the dark matter makes up most of it. We can see the stars and the gas directly (from visible and X-ray observations), and we can figure out where the dark matter is from gravitational lensing (which shows where the mass is).
In the collision, the stars in each cluster passed right through each other
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There are no "of courses". Some models do propose that dark matter does not even interact with itself. Alternately, some models propose that dark matter is it's own anti-particle, so it annihilates when it interacts with itself. In the latter case, we should be able to detect it as a gamma-ray source which cannot be explained by any other means. One recent report of gamma rays from dark matter was withdrawn when other sources were found.
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Too assertive about dark matter (Score:4, Insightful)
Quote: "Dark matter [...] has been firmly established as real [...] There's no question that it exists." There is still plenty of controversy related to the idea of dark matter, and there is no such thing in physics as proving something exists - you can only prove something to be false. I'm not saying dark matter does not exist, only that statements like the above are too assertive.
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*something* is there, but it's not necessarily Dark Matter. It could be something wrong in our theory of gravity, or something wrong with our understanding of galactic-scale space-time. Insisting it must be matter is probably this generation's ether.
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It has momentum (see: Bullet Cluster), which conclusively rules out modifications to gravity. That doesn't leave a lot of alternatives to the "non-luminous matter" concept, which is fairly broad. There is still a tiny bit of space for other theories, but they are getting more and more twisted into knots to explain expansion rates in the early universe, structure formation, galactic rotation curves, dwarf galaxy abundance, and dynamical data like the Bullet Cluster. Some sort of dark matter matter explains a
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I liked the sarcastic humor of this kind of response.
Every best of the best server admin trying to fix a computer: We've spent 100 years trying to get this computer to turn on, but only the lights turn on
You: I bet
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Even if someone had a model of MOND that created what we see at the Universal and galactic level, MOND is fundamentally incompatible with Relativity, the single m
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Astronomers have observed the gravitational lens effect of dark matter in the distant universe. Something is there.
Please, don't respond to Anonymous Cowards. They're mostly all just trolls spouting stuff they know is wrong so they can "start a discussion."
There are multiple observations made in the past 80 years that have caused us to look for an answer, galactic rotation, gravitational lensing, details dealing with the CMB, etc. All the easy things like more matter, changes to the laws of gravitation, lots of black holes, were the first things looked at and have failed to provide any solutions. Slowly, all these diffe
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Or maybe, just maybe... (Score:5, Interesting)
So so so much of the Standard Model (and astrophysics in general) starts out like "Given a spherical cow of uniform density at STP...".
We can basically derive ALL of chemistry from first principles involving (protons, neutrons, electrons) (and their charges), electron shell configurations, etc. Does the Standard Model provide an explanation for the mass of the electron, or any of the other 92 empirically derived "constants" that make up the current orthodoxy? Does calling the gap between reality and our understanding of it really benefit from calling it "Dark Matter", or "Dark Energy", or should we just call it "phlogiston"?
I'm not trolling, I'm serious. The Standard Model has lots of (statistical) predictive power, but absolutely no explanitory power -- back to the chemistry example, it's as though we have atomic weights and molar values, but no notion of electron shells -- we can predict, but we can't explain, at least not in a meaningful way -- yet.
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Well, not that many simplifications. Actually, many people try out many different things to see if your experimental observations are affected by the underlying theory you are basing your assumptions.
I want to point out some contradiction in your message:
- On one hand, you criticize the standard model for its high number of parameters (19, I believe that is the number, actually). And it is a fair criticism, you would like your theory to predict nature with the least number of empirical parameters. If every
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IMHO (based on playing with the dipole model).
Time is flat and constant and causlity happens in forward time.
Gravity and mass are the same, the mass of something is the potential of it to attract via the dipole binding force (DBF).
There is no momentum as such, only a reduction in the dbf cause by velocity effect on the component of the twist subtended onto the other particle. (do it numerically you'll see what I mean, if you move a particle faster away from a clump of dipole stuff the binding force reduces
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This is how I think of things. Basically just regions where energy is denser and lighter and flows in between them. The EM and Weak fields are just particular configurations or patterns of this and the entire thing is perfectly deterministic. We are living in a wrinkled energy background that constantly vibrates.
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In which case you're throwing out Special Relativity, and need to explain what it explains. It's one of the most tested theories in modern physics, and has been shown to offer very exact explanations of a variety of things.
For example, we know that unstable subatomic particles, when at near-light speeds, decay more slowly than if they were still.
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Note that "The Big Bang occurred" and "God occurred and caused the Big Bang" are equal in explanatory power - both say something happened without us being able to observe why (if there is a why). By Occam's Razor, we eliminate superfluous entities in our theories and therefore God.
This isn't to say that there is no God, or the God didn't create the Universe, but that there is absolutely no evidence for divine origin.
What I have concluded is that, if a God exists vaguely in the Christian, Jewish, and M
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Sure. I'm happy with the idea that, if God exists, God caused the Big Bang. What I'm saying is that it only matters if you have other reasons for believing in God, because in either case you're looking at one thing without cause.
Re:Or maybe, just maybe... (Score:5, Interesting)
That's the thing with (supposedly) fundamental particles -- you can't explain them in terms of something else... because then they wouldn't be fundamental. If you're talking about why they have certain properties -- like why there are 3 generations of matter (separated only by mass) and why they have the masses that we measure (as opposed to some other mass), maybe one day when we find a way to merge gravity with the standard model and/or figure out why the Higgs mechanism gives different masses to different particles, we'll find out.
But, if you mean you want to have explanations for things like "charge," "spin," "color charge," and why only certain ones exist -- we may never know. If they're fundamental properties, there may not be any real explanation other than "they just are." That's the universe we appear to live in.
String theory and some other interesting quantum theories are trying to explain deeper meanings and use expected symmetries to figure out missing particles and new physics... and they helped to tease out the Higgs Boson and its field to explain why all fundamental particles don't move at the speed of light. There may be more than one Higgs field & that may explain more if we find it. If there are hidden, curled up dimensions, we may be able to explain all the properties of particles in terms of vibrating strings or membranes in higher dimensions, but until string theorists can decide on what the shape of those curled up dimensions might be for our universe, they can't help much with predictions, much less explanations. Trouble is, there are a heck of a lot of possibilities for those curled up dimensions, and there aren't a lot of ways to discern which ones match our known universe yet. Sure, they can whittle them down to a subset that matches known properties of the universe, but that leaves a massive subset to eliminate false positives from.
I'd say string theory is your best bet for explaining why things are as they are one day... but it may be that some things just are, and that's as fundamental as they get -- at least as far as we can tell from experimental data from within the universe. Anything deeper is speculation or philosophy -- unless it can fit the math perfectly and explain things other models can't. For instance, we've never directly observed quarks, but we've been able to indirectly observe them and figure out their properties from subatomic collisions. At one time, people debated if they really existed or if they just helped the math work... but physicists generally agree they exist today. Maybe we'll find something more fundamental in time that will explain more. My bet is on strings, but... who knows?
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26% of the mass of the universe is made up of your simplifying assumptions: space is flat and uniform everywhere and everywhen, gravity is constant everywhere and everywhen, the speed of light is constant everywhere and everywhen, the Higgs field isn't really the luminiferous aether with a fancy new name, etc.
Addressing the first part of your post only, this is one reason I like the Timescape Cosmology [canterbury.ac.nz] model, that basically posits that some dark matter effects and all dark energy effects are just arising from GR. Most cosmology simplifies the universe to a homogeneous soup, which conveniently ignores small-scale GR effects that could be very important.
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Or maybe, just maybe, if you're not an astronomer or a physicist then there are other people who know more about this than you.
Perhaps the idea that it's all a simplifying assumption is your simplifying assumption.
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Sure. Bear in mind that your speculation is almost certainly wrong, and it's very likely that a real astrophysicist could come up with a counterexample. I like science fiction, and if you're going to have FTL ships you need to speculate. (For extra points, come up with a speculation that shows how it doesn't make time travel possible and practical.) What you are extremely unlike
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No, you can't have general FTL and special relativity and no time travel. The Bergenholms were no better than warp drive in that regard. In fact, since the ship settled at a speed where the thrust from the thrusters matched the power of the ambient stuff hitting the ship, it'd be slower than light. (That was the explanation, and the trip to Lundmark's Nebula was possible only because of the extreme rarity of intergalactic matter.)
I'm not complaining. There's lots of stuff I don't believe in the Lensm
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You'd think Planck-mass black holes would evaporate through Hawking Radiation almost immediately.
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I will concede that an observation could be a pseudo-fact in that there was an error with the instrument that measured it. This is why you need to be ab
All about you, is it... (Score:1)
"What interests me..."
"I..."
"I..."
Thanks for letting us know in an entirely opinionated piece you lack the science background, but this fascinates you.
My dog feels the same way about asphalt and rabbits.
E
WIMPs (Score:2)
WIMPs are unknown particles with unknown properties and the speculative detectors we hoped might detect them haven't yet ... ...this does not mean they don't exist, it just means the things we don't know the properties of we still don't know the properties of ...
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Is there a good idea to think they're WI and not just MP? There's the practical matter that we can go looking for WIMPs, but I don't know of any reason why nonstandard matter would be affected by the weak nuclear force.
Gravitational lensing (Score:4, Interesting)
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Why would it have to interact with itself through non-gravitational means? It doesn't clump like regular matter does, so it would seem that it doesn't have anything corresponding to electromagnetism.
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Why such controversy? (Score:2)
The idea that a form of matter doesn't interact with three of the four fundamental forces doesn't seem all that crazy to me. I mean, the photon and W and Z bosons don't interact with the strong nuclear force, do they? (I'm actually asking - I'm no particle physicist.) And the neutrino interacts with the weak force and gravity, b
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Some people just love to get in on the action, and if they can't do it by understanding the science, they'll do it by blindly dismissing the science. It's an easy route to giving yourself the impression that you're "in the know," putting yourself in the contrarian position (which is not always an incorrect thing to do if you've got the understanding back it up) and making yourself feel part of a more exclusive group. Eventually this all feeds back and you get people who think that being in the minority itse
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Thing is, dark matter is easy to understand. WIMPs are at least much like large slow neutrinos, and the idea of "something like regular matter but - " shouldn't be hard to grasp.
Syfy channel has been eliminated already? (Score:1)
A couple of problems (Score:2)
Well.... they'd need to be pretty small, and also to not evaporate via Hawking radiation. Tiny black holes evaporating would release light at a known frequency that hasn't been detected (or hadn't been a decade ago, when I was paying attention). And the black holes would need to be primordial, because otherwise they'd affect the proportion of Lithium in the interstellar dust. So they can't have been engaging in nuclear reactions while that was being formed (*quite* early in the process). And they'd need
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