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For all that mankind has learned through science, the Universe has so far managed to keep most of its secrets. For instance, we don’t know where the Universe came from, what its fate will be, or even its most basic composition.
But over the last few decades, tantalizing clues and some very intelligent guesswork led astronomers to an astounding hypothesis: the ordinary matter that stiffens our bones and fuels our suns plays only a bit part in the grand epic of existence. Astronomers now believe that for every kilogram of normal matter like atoms, electrons, and quarks there are five kilograms of dark matter.
Very recently, astronomers announced what many had thought impossible, the direct observation of the existence of dark matter. Billions of years ago, two galactic superclusters collided. The collision occurred at a relative velocity of over a million miles per hour. Not since the Big Bang itself has the known universe experienced so violent an event. The aftermath of this collision offered what may be a once-in-Creation opportunity to finally “see” dark matter itself.
Ordinary matter is organized into structures from scales as small as the nucleus of an atom to those that span much of the Universe. The same four physical forces that bind protons to neutrons and hold our feet to the ground cause suns to organize into galaxies, galaxies to group into clusters, clusters to gather as superclusters, and superclusters to form structures astronomers call simply filaments, bubbles, and sheets.
Superclusters can contain millions of galaxies in relative close proximity. The stars within these superclusters remain bound to their native galaxies, but most of the gases are diffused throughout the cluster and heated to millions of degrees in the process. These gases make up most of the mass of an individual galaxy, and about 90% of the visible mass of the supercluster.
Astronomers have long been aware that superclusters do not contain enough visible matter to explain their existence. The hot gases and galaxies orbit the cluster so quickly that the gravity of the visible mass is insufficient to hold the matter together. Thus the theory of dark matter was born. The theory suggests that dark matter interacts with normal matter via only one of the four fundamental forces: gravity. Calculations and computer simulations show that clumps of dark matter lie at the centers of all large structures in the Universe, even the Milky Way.
When two clusters collide at high speeds, the visible galaxies and dark matter pass right by each other as if nothing happened. But the gases smash into each other with enough force to slow them down considerably. Thus most of the visible matter in the clusters is stripped away leaving two remnant clumps of dark matter behind. This is exactly what astronomers believe happened billions of years ago in cluster 1E0657-56, also called the bullet cluster.
The image at the top shows the bullet cluster in both visible light and X-rays. The fuzzy red light is the X-ray glow of the stripped gases. To the right and left of that glow you can see the clusters of galaxies themselves. This animation attempts to show the collision and better explain the images as well.
Intense gravitational fields warp the fabric of space-time enough to bend light rays. At galactic scales, this can cause a phenomenon called “gravitational lensing” that focuses and distorts the light we see from distant galaxies. By measuring this distortion, scientists can calculate both the mass and extent of the lensing object. The illustration on the left shows how the images of distant galaxies are brightened, distorted, and duplicated by gravitational lensing.
To the right and left of the bullet cluster, astronomers observed two very large gravitational lenses using the Hubble telescope. The mass necessary to create such large gravitational lenses (shown in blue in the picture on the right) is far greater than that of the galaxies in the original clusters, therefore something very massive and invisible lies at the center of those clusters. That something, observed now directly for the first time, is dark matter.
If that all seems a bit less than a direct observation, just consider the bottom line: something completely invisible that is nevertheless more massive than a cluster of galaxies and spans millions of light years is distorting the light from behind the bullet cluster. We don’t yet know what the dark matter is, but we now know it’s there. Whether dark matter is simply the husks of failed stars, some exotic new sub-atomic particle, or something else entirely is a secret the Universe still holds from us.
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This just goes to show you once again that we are just scratching the surface of what we know about the universe. Interesting
40 years ago we knew almost this little about the oceans on our very planet…I surmise it will likely be longer than 40 years from now that “they” know as much about the universe…of course, it is a “bit” larger than the oceans, and a bit more inaccessable!! ;)
True. And the way the governments of the world is treating this sort of exploration is proving to retard this process even further. NASA should never have to fight for a budget.
The enigma of dark matter is baffling… it is baffling that it is considered an engima. Inferring mass from light reflectance or emittance is obviously problematic. What surprise is it that this method of inferring mass gives funny results?
It’s as though in ordinary life we were amazed that light-colored objects didn’t weigh more.
paalexan said: “The enigma of dark matter is baffling… it is baffling that it is considered an engima. Inferring mass from light reflectance or emittance is obviously problematic. What surprise is it that this method of inferring mass gives funny results?
It’s as though in ordinary life we were amazed that light-colored objects didn’t weigh more.”
The actual means by which astronomers determine the visible mass of clusters relies on a long string of assumptions about the mass distributions of stars within the galaxies and the size distributions of galaxies within the clusters. Which is just to say that the mass is not known precisely, but probably within a factor of 2 or so (just guessing). But the light-bending properties of mass can be very accurately calculated, and the result is that the necessary mass to produce the gravitational lensing observed is much greater than the estimated mass of the galaxies in the cluster.
So, I don’t think it gives funny results. On the contrary, it’s an artfully-reasoned scientific breakthrough!
Give NASA a blank check? I don’t think so.
paalexan said: “The enigma of dark matter is baffling… it is baffling that it is considered an engima. Inferring mass from light reflectance or emittance is obviously problematic. What surprise is it that this method of inferring mass gives funny results?
It’s as though in ordinary life we were amazed that light-colored objects didn’t weigh more.”
At one time scientists thought that dark matter was some ordinary matter which did not reflect or emit light, but there is so much dark matter that this would make major changes to the composition of the universe, which would make major changes to how the early universe evolved. Measurements of the composition of the universe indicate that the early universe did not evolve with 5 or 6 times the amount of ordinary matter. Ordinary matter can only contribute a small amount to dark matter – the rest is something strange that we do not understand. Likewise, measurements of massive neutrinos indicate that they are also only a small percent of dark matter.
Maybe the dark matter mystery will get solved in pieces – a little bit of brown dwarfs, a little bit of neutrinos, a little bit of a bunch of other things.
Good job, Anthony. DI.
Give NASA a blank check? I don’t think so. “Nastimann says”
Right Nastiman(n), give the money to: unwed unemployed uneducatable mothers, drug addicts, politicians (who are the most needy) for their porky little egotistic projects, the war on prostitution, Bible thumpers etc etc. Clearly NASA should have carte blanche on nearly all their projects. Soon the politicians/religious “leaders” will have screwed up this planet beyond belief. Sorry Nastiman, I had to that off my chest. I forgot the damn interesting subject, damn! Once again, this is a baby step, and if we can surpress the nastimans of the world, it may lead to an adult step.
Fascinating.
I was wondering why black holes aren’t a contender for ‘dark matter’ (being dark and massive). It turns out they are, sort of:
It seems that when a black hole evaporates (black holes do, in fact, radiate due to quantum fluctuations, an effect known as “Hawking Radiation”), it turns out that they don’t evaporate completely: when the size reaches about the size of a proton, containing a few milligrams of mass, it stops radiating. What’s left is known as a “primordial black hole”.
Primordial black holes are a contender as the explanation for dark matter, though there is as yet no explanation as to why there would be gazillions of these primordial black holes.
I still don’t know why ‘normal’ black holes are ruled out – laters.
mHagarty said: “True. And the way the governments of the world is treating this sort of exploration is proving to retard this process even further. NASA should never have to fight for a budget.”
Greater understanding of our universe is never bad, but governments also must weight the practical benefits of such investigationagainst the needs of their citizens. Discoveries such as this, despite being very interesting, are for all practical purposes useless, and do little to help out in the day to day lives of people.
of course, by no means am i saying this research should stop, just that the needs of people must be balanced with astronomers curiousity. And research into such things is rarely wasted money, though it may be a very long time before it has a practical benefit.
Anthony Kendall said: “The actual means by which astronomers determine the visible mass of clusters relies on a long string of assumptions about the mass distributions of stars within the galaxies and the size distributions of galaxies within the clusters. Which is just to say that the mass is not known precisely, but probably within a factor of 2 or so (just guessing). But the light-bending properties of mass can be very accurately calculated, and the result is that the necessary mass to produce the gravitational lensing observed is much greater than the estimated mass of the galaxies in the cluster.
Yes, of course it’s most complicated than just, “That’s pretty bright, must be a lot of mass,” but nonetheless it’s an estimation where all kinds of assumptions are made to try to estimate mass from how bright stuff is on a photographic plate. Ultimately, the data we have is just this: two methods of estimating mass disagree. So why not just say, “Oops, one of the estimations is off,” and be done with it?
Give NASA a black check and a worthy adversary.
I’m a bit suspicious of this dark matter, it seems like a stop-gap measure; like einstein’s cosmological constant.
mHagarty said: “NASA should never have to fight for a budget.”
You’re joking, right?
NASA does some cool stuff, but as a way of generating knowledge they give the fewest returns for the largest investments.
smokefoot said: “At one time scientists thought that dark matter was some ordinary matter which did not reflect or emit light, but there is so much dark matter that this would make major changes to the composition of the universe, which would make major changes to how the early universe evolved. Measurements of the composition of the universe indicate that the early universe did not evolve with 5 or 6 times the amount of ordinary matter.”
This is circular.
Estimates of early universe composition are dependent on observations of the current universe. You can’t use the estimates of early universe evolution to argue against observations of the current universe without pulling the rug out from under yourself in the process!
Cant Dark matter just be back hole matter?
paalexan said: “…So why not just say, “Oops, one of the estimations is off,” and be done with it?”
Probably because the astronomers are all hoping for something more important than just a disagreement between two estimated masses. No, seriously, I think it’s because the methods they use are both deemed fairly sound, so if there’s such a big disagreement than something must be going on there.
So much of astronomy relies on estimates–though some are prety darned good ones. Distances are fixed using “standard candles” that are all estimation and extrapolation. All masses are estimated, unless you can actually observe two objects orbiting each other (which we currently can only do with nearby objects). Even the brightnesses of objects in our own Milky Way are estimated based on a guess as to how dense the dust in the plane of the galaxy is. Scientific progress has to be made, even if it is based on estimates.
Anthony Kendall said: “Probably because the astronomers are all hoping for something more important than just a disagreement between two estimated masses. No, seriously, I think it’s because the methods they use are both deemed fairly sound, so if there’s such a big disagreement than something must be going on there.
A big disagreement is just really strong evidence that one or both estimates are wrong. :-)
Perhaps I’m overly skeptical of estimates, though, since I’m coming at this from biology. In biology, estimates are always wrong. Usually very wrong. Astronomy doesn’t seem to have nearly as many problems with complexity and overdetermination, though.
cutterjohn said: “Greater understanding of our universe is never bad, but governments also must weight the practical benefits of such investigationagainst the needs of their citizens. Discoveries such as this, despite being very interesting, are for all practical purposes useless, and do little to help out in the day to day lives of people.
Neither does carpet bombing innocent people – but you seem to have a decent sized budget for that?..
-just an observation-
NASA does a lot more than just explore the cosmos… How could we survive without the Tempur-Pedic Swedish (
I’m not saying we should give NASA a blank check, but I wouldn’t be opposed to handing them a hefty sum, either.
Also, why didn’t the dark matter stay behind with the galaxies as they were slowing down upon impact? Is this dark matter exhibiting properties of momentum?
Is there some type of unusual hierarchy here? That is to say, does the dark matter influence mass, but not the other way around? Or is there some other explanation as to why the dark matter didn’t stay with the galaxies?
One more thing: does this mean that dark matter *is* gravity? Does gravity no longer exist in particles that we can see? Or is dark matter actual mass that doesn’t touch anything? How attractive is dark matter to more dark matter clusters?
By the way: That was a damn worthy article from start to finish, Colonel Kendall.
As US government agencies go, NASA is better than some, but I cannot see how anyone could possibly defend the idea of handing them a blank check. My hard-earned tax dollars are a limited resource, and this country is full of people who want an ever-growing stack of them. As with any limited resource, we must prioritize. I do not agree with most of the priorities our elected officials pick, but turning on the faucet full blast for any agency seems patently stupid.
what if there isn’t any dark matter?
what if gravity just behaves differently in different parts of the universe, stronger in some places, weaker in others…
or maybe gravity’s strength has changed over the history of the universe… so that is was stronger in the past than it is now. (the light we are seeing from these galaxies is millions of years old), thus this stronger gravity could have caused the gravitational lensing effect… not dark matter.
this would explain why these galaxies can rotate so quickly (stronger gravity), and produce this lensing effect, without the need to introduce more mass (dark matter) into the equation.
Funny how this stuff never even makes it NEAR the news, let alone be treated by most as the incredible breakthrough it is. Things like this make me respect those who work hard for the sake of knowledge, yet get very little reward.
It’s funny to me that we always assume the things we know, ordinary matter, electromagnetic radiation, things like that, are all that exist. Perhaps this world we know is just a tiny little odd backwater of the universe. Dark matter is a complete mystery to us but is clearly the majority of matter in the universe. Is there such a thing as dark energy? Along similar lines, what makes us think gravity always behaves the same, just because it always does in our experience? Einstein proved that space is never linear, and time is never absolute, even though we always assume they are. The universe is an immense, unfathomable wonderland, and we’re miles away even from understanding the tiny little eddy we inhabit.
This is fascinating. But I always sort of had this basic doubt for the gravitational lensing. If it is anything like the above picture, that the light is bending, isnt Hubble supposed to see a HALO effect of the hidden object rather than just a duplicate? Please excuse me, if I do not make sense.
NASA did have a blank budget basically… until Bush stepped in. Also astronomy and general space research is directly related to improvements in the defense and civilian industries, so it is in everyone’s best interest (especially war-mongers…Bush?) to keep funding up, except that isnt happening.
The estimations made about the mass of stars is many orders of magnitude less than the disparity which dark matter accounts for. Put another way, there is so much matter there that the error in estimation of the mass of the stars is negligible. Gravitational lensing is a very old, universally accepted concept also.
paalexan said: “You’re joking, right?
NASA does some cool stuff, but as a way of generating knowledge they give the fewest returns for the largest investments.”
Here’s a list of just a few things NASA has developed… during the Apollo period.
Kidney dialysis machines
CAT scans
Cardiovascular conditioners
Stress free athletic shoes
Freeze-dried food
Advanced heat shields for the engines of cars and trucks
Water purification technology
Digital signal-processing techniques
Vacuum metallizing techniques
Cordless power tools & appliances
Cool suits
That’s, basically, from about 1965 to the end of the Apollo era in 1979… and it’s the ones that affect us in our EVERY DAY LIVES. They invented much, much more than that. Sure, the cost may have been a bit high, but had it not gone to science it most likely would have gone to a guy I, unfortunately, know who plays golf every sunday and raquetball 3 times a week while also collecting workers comp for his so called “bad back.” I’d rather my tax dollars go to finding out what makes this planet, solar system, and universe tick than to him or any other lazy bum who gets a free ride from our screwed up socical service system.
I found that article really interesting, and the comments upon budget allocation rather apt.
To paraphrase the late great Douglas Adams:
As cavemen, we probably spent far too long wondering what colour the wheel should be.
NASA’s biggest problem is that, like most governmental entities, it has become cocooned in an amniotic shell of red tape and back scratching that prevents any real cost effectiveness from setting in. The agency needs an administrative enema, and then needs to get out of the business of manned space flight. Once NASA releases the stranglehold it has, along with the aerospace mega-corps like Lockheed-Martin, on the manned programs and lets people like Burt Rutan and the like take care of that, they can focus on what they have always done best…real science. IMHO, of course. :-)
As for the dark matter, while I agree it has always smacked of the ‘Universal Constant’, I have come to realize that despite the Saturday morning cartoon sound of the stuff, it’s just a placeholder for ‘whatever-the-hell is really out there’.
Misfit said: ”
Also, why didn’t the dark matter stay behind with the galaxies as they were slowing down upon impact? Is this dark matter exhibiting properties of momentum?
Is there some type of unusual hierarchy here? That is to say, does the dark matter influence mass, but not the other way around? Or is there some other explanation as to why the dark matter didn’t stay with the galaxies?
One more thing: does this mean that dark matter *is* gravity? Does gravity no longer exist in particles that we can see? Or is dark matter actual mass that doesn’t touch anything? How attractive is dark matter to more dark matter clusters?
“
From what I gather, dark matter behaves like normal matter as far as gravity goes, but does not interact in any other way – in particular does not reflect or emit light, is not affected by electric or magnetic fields, does not collide with other matter, etc.
For instance, normal matter circling a super-massive black hole, such as the one found at the center of our milky way, interacts with other matter, a sort of ‘friction’, which *should* cause matter on the outer fringes to move slower. In point of fact, measurements of rotational speed seen in edge on galaxies (good old ‘red-shift’ / ‘blue-shift’), shows that this slowing does not occur. The current best explanation for this phenomenon, is that there is 4 to 5 times as much dark matter as normal matter orbiting the galaxy, and that it is ‘dragging’ the normal matter with it.
Back to your question: this means, that in a collision of galaxies, the dark matter may be deflected a bit by the mass, but will otherwise not interact the way normal matter would: no collision of atoms, no momentum change due to light reflection, just pure gravitational interaction.
Another example: normal matter in a galaxy tends to slow down and be swallowed by the black hole at the center – this is an observed phenomenon. Theoretically, and as far as we can tell, this does not happen to dark matter – there is nothing to slow down its orbit.
plunki said: “what if there isn’t any dark matter?
what if gravity just behaves differently in different parts of the universe, stronger in some places, weaker in others….”
Great question! Check out that link to Cosmic Variance at the bottom of the page. It’s a blog written by astrophysicists. I think they have something to say on that question and are far more qualified than I to discuss it.
Not just gravity.
plunki said: “what if there isn’t any dark matter?
what if gravity just behaves differently in different parts of the universe, stronger in some places, weaker in others…
or maybe gravity’s strength has changed over the history of the universe… so that is was stronger in the past than it is now. (the light we are seeing from these galaxies is millions of years old), thus this stronger gravity could have caused the gravitational lensing effect… not dark matter.
this would explain why these galaxies can rotate so quickly (stronger gravity), and produce this lensing effect, without the need to introduce more mass (dark matter) into the equation.”
Would something (gravity or something entirely different) cause “dark matter” to slow down? What about light itself?
Melon Head said: “this would explain why these galaxies can rotate so quickly (stronger gravity)…”
It is not that the galaxies rotate altogether more quickly, but that they aren’t finding the expected differential between the speed of the hub and the speed of the rim.
paalexan said: “You’re joking, right?
NASA does some cool stuff, but as a way of generating knowledge they give the fewest returns for the largest investments.”
Not true. I work in a lab where we get the majority of our funding from NASA contracts. Besides the stuff we actually do for NASA, there are quite a number of other side projects/discoveries, and IR&D type stuff that results from these dollars, most of which are directly beneficial to the “general public” (including you NASA haters out there).
NASA does a lot more than collect moon rocks.
Exactly. NASA is extremely important for *everyone*. Don’t envy those who do things you can’t do, but instead support them the best you can.
Very, very interesting article.
It is great that the people who are investigating the Cosmos are shaking the foundations of known knowledge and raising all these questions about Dark Matter, since many of the questions cast doubt on the current knowledge base. That is one of the hardest things to do in science, buck the trends. It can also be a sure way to get your research funding cut, or loose a tenured job! So I have to applaud those few that are willing to posit new idea’s and questions concerning then new and unexplained. I feel that this discovery will help point the direction to other dimensions of space and expand the current idealogy of Time.
NASA my not have an unlimited budget, being in the public eye and all, but what makes you think that one of the more covert black ops divisions, out of the public eye and funding, does not have an unlimited budget? Anytime we are looking into the unknown or staring down the rabbit hole, being restricted by budgets would quickly become unacceptable. With enough acoustic Kitty Programs, or arms deals, there would be pleanty of money for gathering knowledge to a central location.
Rather than bankrolling NASA our government seems to be more interested in finding more effective ways of killing people.
paalexan said: “NASA does some cool stuff, but as a way of generating knowledge they give the fewest returns for the largest investments.”
Are you sure about that? I hear there’s a planned $320 million “bridge to nowhere” in Alaska that disagrees with you. ;-)
PresMatt barely scratched the surface on his list of the inventions that have come out of NASA. You can find a number of other inventions that came out of the space program listed here and here, for example. Heck, Scientific American came out with an entire book on the subject of NASA technology that we use every day.
You shouldn’t be so quick to brush off the benefits of our space program if you don’t know how numerous the benefits we’ve seen from it are. It’s quite a large claim to say that NASA is the program we get the fewest benefits from per dollar too. Did you actually check all of the other programs?
I’m not for giving NASA a blank check either, but we should not deny how beneficial the program is. Both short term and long term projects are important, and NASA gives us benefits in both categories.
P.S. Anyone else here get their geeky glee from reading about evidence confirming the existence of dark matter? :-D
For finding dark matter, NASA _should_ get a black check. (no typo in that sentence)
I’m thinking dark matter might be an altered form of all those socks that disappear in the wash… they have to be going somewhere, but we never find them. Or those people on the back of milk cartons…
paalexan said: “A big disagreement is just really strong evidence that one or both estimates are wrong. :-)
Perhaps I’m overly skeptical of estimates, though, since I’m coming at this from biology. In biology, estimates are always wrong. Usually very wrong. Astronomy doesn’t seem to have nearly as many problems with complexity and overdetermination, though.”
Cosmology is an odd science. You can’t do experiments, really — it’s all “Make a guess, look for evidence that this is right or wrong.” Fascinating research, but it’s one of those fields where two prominent people can subscribe to wildly different theories without there being a lot of controversy.
So a case of an “incorrect estimate” is a real focal point for study. The estimates are based on theories about the way the universe works, or the way it’s structured. If the estimates don’t match, then, you’re right: One or both of the estimates is wrong. That’s a really big deal, since it means that one of the underlying theories is wrong (or incomplete), and you try to find out where the error is. You can’t just say “Huh, I was wrong”, because that estimate came from somewhere.
It’s like if you were guessing jellybeans in a jar, and you calculated the volume of the jar, and the size of a jellybean, and said “OK, I think there are 3,000 jellybeans in that jar, give or take 25%”. If you were then told that there were actually 15,000 jellybeans in the jar, you don’t just say “Well, I was wrong” – you say “Woah, there’s something I don’t understand about the way jellybeans fit in a jar. How can I account for this wild discrepency?” Maybe the jar used smaller jellybeans than you thought, maybe the jar has a little pocket of hyperspace in it, maybe the jellybeans were squished really really small, maybe the jar was bigger than you thought, and maybe the guy that counted the jellybeans was drunk. You look at all the theories, pick the one that seems most likely, and then go off and see if you can find more evidence to back that up or refute it.
(See? Cosmology is -just like- jellybeans.)
I’m not a scientist so I know almost nothing about the workings of the universe, but why not entertain at least the possibility that all that ‘dark matter’ is actually God! After all, doesn’t it permeate every part of the universe?
It can’t be explained any other way, just as we can’t explain God……..who knows, certainly not I, but it’s possible isn’t it?
shesdeluvley said: “I’m not a scientist so I know almost nothing about the workings of the universe, but why not entertain at least the possibility that all that ‘dark matter’ is actually God! After all, doesn’t it permeate every part of the universe?
It can’t be explained any other way, just as we can’t explain God……..who knows, certainly not I, but it’s possible isn’t it?”
No.
NASA is spending billions to find water on Mars, Moon, and Comet Temple, so they can strengthen their argument for Evolution. Their motive is: they’re trying to destroy our faith in the Bible, which NASA hates. Evolution never happened. The first DNA never came together by accident. No-one believes Evolution, but they preach Evolution, because they hate the Bible so much. The Bible is True. Our Lord Jesus Christ is the Creator.
Why are we drilled on Evolution, millions of times,……… but we never hear of other Science? We are not told of Thermo-dynamics, gravity, magnetism, levers, chemistry, inertia, centrifugal force, etc……………., but the Evolutionists preach Evolution to us every day. I smell an un-savory motive. They preach the Evolution Lie millions of times, hoping that we’ll believe the lie.
In a very real way, evolution is God, hence the preaching.
Ask yourself this: Does God evolve ? if not, why not ?
Jesus talk is childish, like talk of Santa Claus.
Many of us don’t subscribe to such primitive notions.
A bit off-topic, but honestly, I would not at all be opposed to giving NASA unlimited funds (provided there is accountability), even if it came at the expense of raising taxes. Curiosity is one of our most prevalent traits, and I can at least speak for myself when I say that I would much rather skip a coffee every other day and be exposed to the inner workings of our universe. On your death bed, would you rather think back on how you had that extra coffee and that nicer car, or how you will pass away knowing the origin of the universe and sentient life on Earth (and possibly other planets). Just thinking about how my time in this world will eventually be over, many years from now, and I would still have all of these unanswered questions in my head, is something that I have a difficult time dealing with.
We still don’t know very much about the oceans. Only explored about 3%.
Because if you say its God you say it is unknowable. No one is saying that now, they’re just saying they don’t know what it is.
Well, for starters, if gravity’s strength HAD changed over time, we should be able to observe a difference in the effect between our galaxy and other galaxies farther away.
As the article says, even in our own galaxy there is supposed to be dark matter.
On the off chance that someone might actually read this old article and all the comments I add this remark:
The Bullet Cluster in no way provides any more evidence for dark matter than any previous observation. There is no way to “see” dark matter in the data, rather it is just infered, the same as it has been infered from other data in the past.
Further more there is no objective reason to believe that there is such a thing as dark matter. There ARE serious inconsistancies in our obvservations of galaxies, however a precise description of the problem would be to say that astronomical objects, especially galaxies, behave as if there is more ‘gravity’ than predicted by Newton’s theory of gravity. So that means there is either some invisible source of the gravity (dark matter) OR Newtons theory of gravity is incomplete. Theories based on the premise of invisible stuff have NEVER made a correct prediction regarding the behavior of galaxies, including the Bullet Cluster. On the other hand theories based on the premise that Newton’s theory is incomplete have on several occasions made predictions that were later confirmed. The most famous example is General Relativity, though that is not relevant when talking about galaxy behavior.
Another, less famous, theory that assumes Newton’s theory is incomplete is called MOND. MOND (MOdified Newtonian Dynamics) has been exteemly successful in accounting for and predicting galaxy behavior in all but a few cases, including many cases where DM theories have been shown to be next to useless. For more information google MOND!!
Can one mesure the mass of a Black Hole??????? If not, can we not just assume the things may just weigh a sh#* tonn more than we give them credit for??? I mean, they have enough mass to warp the membrane of space time and exert enough gravity to capture light and thus make them unobservable or “Black”.. They seem to be located at the centre of galaxies which seems to me like their gravitational pull may be what cased the things to form in the first place… Thus making them the galactical equivilent of our solar systems sun with everything revolving around them. WE KNOW THEY EXIST..
Can black holes not account for the missing mass that we are giving Dark Matter all this credit for? :-) Am i being retarded??
What interest me so much is how dark matter only interacts with ordinary matter gravitationally. It does not contact normal matter(since it is believed to be very small that it simply passes through the gaps in ordinary matter) in any way other than by gravity.
What surprises me though is how its massive when it influences ordinary matter, but by itself it isn’t. (Sort of reminiscent of the higgs boson, something [which was] believed to give all the numerous subatomic particles their strange and unusual masses.) Here in the milky way it makes up most of the mass in the galaxy, yet on its own it doesn’t seem to want to coalesce with other dark matter.
This comment has nothing to do with the article. I just liked making the : ( tab change to : ) purple monkey dishwasher! sigh…
As per NASA’s blank check: money is an imaginary construct, especially without a gold standard to back it up. At this point, we have little regulated, tourist/shareholder-driven, arrogant CEO run competitors punching hole after hole in our atmosphere, raking in unimaginable profits doing what NASA could have done safer & better without endangering our species’ life.
As per the black holes, I, philosopher as I am, refer you to Neitzche: when you gaze into the abyss, the abyss…