Dark Matter/Dark Energy

[Fraser]

Apparently, there are some people who don't seem to believe that dark energy/dark matter actually exist. I've created this discussion thread to contain the conversaton. Talk about it here all you like; however, keep the conversation to this thread. I'll be actively moderating other discussions and pushing any arguments about dark matter/energy into this thread.

Thanks!

So... do you have a problem with the concept of dark energy or dark matter?

[duffer]

So... do you have a problem with the concept of dark energy or dark matter?

In a word, yes, because most of what I've read is extremely vague on what it actually is. My dumb questions on the subject are: could you describe it using the periodic table? i.e. is it normal matter that simply happens not to have collapsed into light-emitting stellar systems? If not, could it ever be synthesised in lab/particle accelerator etc?

[N3373H]

I agree, it sounds dubious. If it does exist, it must be invisible or we wouldn't be able to see billions of light years away. Also, if it has enough repulsive mass (sic) to accelerate the universe apart, wouldn't it have the reverse effect of gravitational lensing and distort our views of distant galaxies? I'm still not sure I understand the nature of dark matter/energy (where it is or where it emanates from). If it's between galaxies, then why isn't it also closer to home where we can detect it? Perhaps the calculations that predict it are in error. ? :wacko:

[Tinaa]

From what I learned in Intro to Astronomy, we may being sitting on dark matter and it could be streaming through our bodies. Planets, brown dwarfs, neutrinos, WIMPS, MACHOS, and exotic matter (stuff not made of protons, neutrons and electrons), and who knows what else are candidates for dark matter.
The more I learned, the more questions I had! I don't know who said this, but it fits, "Not only is the universe stranger than we imagine, it's stranger than we can imagine."

[Decimal]

I personally Believe Gravity, Light and Dark Matter are Similar and Have resembling Characteristic Properties

I also believe that in time we will be able to distort warp or even alter these to fold space (kinda like stargate..but not as perfect :unsure: ) it wont be such like creating a worm hole through space from one location to another, but like cutting two circles out of a peice of paper and making them meet...

I understand me..

[N3373H]

I'm still confused. If dark matter is made up of massless or almost massless particles, then how can it be repulsive? I understood that in Einstein's terms, gravity wasn't so much a force as a result of mass warping time/space, and objects moving past the mass were drawn to it by the curvature of space. In this view then wouldn't dark matter be the opposite of mass and warp time/space in such a way as to cause the object to follow the curvature of space away from it? If so, then with so much predicted dark matter, the universe's appearance would be so warped it would look as if we were in a giant funhouse. I'm starting to get too deep for my own understanding. :blink:

[Fraser]

Dark energy and dark matter are two different things.

Dark matter has mass. If you look at a distant galaxy and consider it as a single object, in terms of how it attracts other galaxies, bends light, and even stays together as it rotates instead of flying apart, you would calculate its mass as being X. If you actually added up all the stars, planets, dust, etc in the galaxy, you would end up with a visible mass of Y. It turns out that X is several times Y. In other words, it has more mass than you can see, and astronomers don't know what that extra mass is. They know it's there by how it interacts with objects, etc.

Dark energy is completely different, and has absolutely nothing to do with dark matter. Sadly, they have similar names. Dark energy was only discovered about 5 years ago by astronomers who wanted to know how expansion of the Universe was slowing down. They did this by measuring the distance to various supernovae in the Universe. They found that the supernovae were more distant than they were supposed to be. The only way they could be as far away as they are is if the Universe isn't slowing down, but actually speeding up. In other words, some repulsive force is being generated in the vacuum of space between objects. The further apart they are, the force is being generated. What this force could be is a complete mystery.

So there you go. Dark matter is just like regular matter, we just can't see it. Dark energy is a strange repulsive force that is created in vacuum.

[Evil Steve]

you would calculate its mass as being X. If you actually added up all the stars, planets, dust, etc in the galaxy, you would end up with a visible mass of Y. It turns out that X is several times Y.

Wouldn't Y be several times X ( sorry pedantic)

some repulsive force is being generated in the vacuum of space between objects.... What this force could be is a complete mystery.

It may seem stupid but someone has to say it.
They have taken into account the lessening effect of gravity as objects get further away from each other, haven't they?

Evil (not answering just asking)

[Fraser]

No, X is the total mass of the galaxy, and it seems to be several times the visible mass.

Visible Mass + Dark Matter = Total Matter

Regarding the dark energy, the distance is too far for it just to be coasting. Gravity should be slowing everything down, but the opposite is happening. One theory I've heard is that at great distances, gravity actually flips around and starts repelling.

[Cambo]

Have I got this straight?

Dark matter is non light emitting matter?

If not what is dark matter made of?

Dark energy is something that is out there but we don't know what it is made from or how it is made?

I am wondering is this my first post with nothing but questions?


:blink:

[cswift1]

This topic is insanely confusing, I think, for one reason - the logic of it is running backwards. Having made observations of the rate of expansion of the universe, something is simply not adding up. And that something is the mass of the universe. It seems that we need more, alot more, for the observations to start making sense. It's the same with dark energy. It appears that the outer reaches of the observable universe are expanding faster than they "should" be. Again, only by hypothesizing some form of energy can observations start coming into line. It's working it backwards the same way that Mendeleev did in putting together the Periodic Table of the Elements. He had to leave "holes" in the table where certain elements "should" be but had yet to be discovered. He could not tell you what these elements looked like or even what they were, but he was able to say something about what they did. Only later was he proved to be correct in predicting a) their existence and b) their chemical behavior. In the same sense as Mendeleevv, there is (for now) no way to get anything other than vague explanations about what they "are" or what they "look like". All we do know is that IF dark matter/energy existed, our observations would make more sense. Again, it's kind of working backwards but it's a technique that has produced a great amount of fruit in past scientific discoveries.

[Fraser]

Welcome to the Universe Today forums cswift1.

Great explaination. We haven't seen dark matter directly, but we can measure its effect on objects in space. Dark matter could very well be normal stuff, like brown dwarfs or clouds of dust which aren't emitting enough heat or light for us to see them. Of course, it would mean that there are hundreds of brown dwarfs for every regular star. But it's still a possibility.

Once again, the only way we know dark energy is out there is because of the effect it's having on objects in space. Imagine you're throwing a ball up into the air. The ball leaves your hand, slows down from gravity and then falls back. That's the way the Universe was supposed to work. But instead, imagine you throw the ball and instead of slowing down, it just keeps accelerating into the sky. The discovery was completely unexpected. After the initial momentum from the Big Bang, the Universe is accelerating apart.

[scott712]

The requirement for more matter than we can see or "Dark Matter" arises from the observation that galaxies seem to spin far too fast to not spin apart unless there was more mass than is apparent from the dust, interstellar gases, stars, black holes etc.

I see a possible flaw in this assessment. Gravity might be a great deal more powerful over long distances than we have been able to verify. Was it the Pioneer Space Probe that left our Solar System? Anyway, there were reports that this probe's trajectory was signifigantly different from expected.

Some have postulated that there is a relatively strong repulsive force between any two given pieces of matter that partially overcomes the gravitational attraction that we might measure between them in a laboratory. This strong repulsive force would fall off more rapidly with distance than gravity. Thus in a laboratory we might be left with the impression that gravity is a lot weaker than it really is.

This close range repulsive force is probably not the "Dark Energy" everybody is talking about that causes the Universal Accelerating Expansion.

Wm. Scott Smith

[kashi]

:unsure: I like the idea that our universe is a "brane" (a 4 dimensional sheet) which is next to a whole lot of other universes of a simular formation. When objects have a very large mass (eg. black holes at the centre of galaxies), the sheet bulges and can actually affect other sheets (universes). Think of layers of paper, one of which has a marble shaped bulge in it. The gravitational effects from one universe could therefore affect another. Perhaps there is a universe close to ours wondering where all of the gravitational effects of their matter has gone!

Kashi

[N3373H]

If the universe is truly infinite then perhaps big bangs are a common thing. As the matter from one big bang heads towards the matter of another big bang, the matter would pull itself together to eventually form a super super massive black hole that would explode under it's own weight and cause another big bang. If these big bangs were, say, 28 billion light years away, we'd never be able to detect them but we would be able to observe an acceleration in our own visible part of the universe when there should be a deceleration. Then we wouldn't need any dark matter or dark energy. Am I making sense here, or have we already proven this not to be the case?

Just curious, do we know where the center of our known universe is? Where the big bang happened?

[Arramon]

sorry... i wrote this under another topic... so i'll just cut & paste...
----------------------

Dark Matter seems to be concentrated around the outer edges of our galaxy, more clustered as it recedes, and less the closer in it gets..... sort of like an outer layer to our galaxy, keepng things in.... Dark Energy seems to be keeping that Dark Matter in one globule, which constitutes our galaxy... if the ISM is comprised of mostly Dark Energy, which seems to repulse the matter around it, making the ISM expand, the globule of our galaxy will continue to expand along as well... but, seems to remain intact due to the gravity of our galactic bulge, and the pressures from the outer layer (dark matter) versus the repulsion of the Dark Energy (keeping that Dark matter within a 'cell' form)...

we are voids in space, connected by thins wisps of hot gas...
our galaxy is just a big pocket of hot gasses... filled with whatever else we now know... with small shafts of hot gas streaming from it... some connecting with other galaxies or globules of pocketed gas, and some with ends to nothing...

If Dark Matter can be analyzed to show its 'true' properties, then maybe we can start to theorize what the functionality of Dark matter might be... it seems to be helping stablilize the structure of our galaxy, so one function can be that it is, is some way, a protective shell around us, keeping the coldness of the ISM seperate from the temperatures within, and the Dark Energy from ripping our galaxy into many small individual elements that would be scattered if the Dark Matter were not present... that is to say if the galactic core couldn't hold the outer layers within its pull.

All speculation, of course... but, hope it helps some =)


. ..-={A}=-.. .

[Bill AH]

Is it possible that dark matter (or energy depending on the line of reasoning) is only part of the problem and the other problem is with the theories themselves (heaven forbid we as humans could be wrong :P ). Perhaps there is a large amount of dark matter out there but not the several times factor of X to Y. A better understanding of the theories that are predicting this dark matter may reveal that there is another part of the equation that hasn't come to light in the scientists minds yet. Therefore, it may be a combination of the two where dark matter can be a smaller, more believable amount.

[curry]

Dark matter does not have to be very complicated. We know that there is a lot of extra mass in the galaxies, we just don't know what it is yet. We can't see it, so we call it dark. It is similar to when we detect a wobble in another star. We know that some other mass is nearby, even if we cannot see it. This is one of the ways that we are detecting planets at other stars. The motion of galaxies clearly show that there is a lot more mass than what we can see. For now we call it dark matter. Some people want to think that this dark matter is something strange, could be, but most likely it will turn out to be just extra matter that we don't see yet.
Dark energy, unfortunately, has the same dark word in its name. This has led a lot of people to think that it has something to do with dark matter. It does not. They are completely different things. Dark energy comes about because it seems like the expansion of the universe is speeding up and It would seem like some form of energy would be needed to make this happen. We don't know what this energy is so we call it dark. The answer to this one is more likely to be something strange.
Curry

[Fraser]

Welcome to the Universe Today forums Curry.

Thanks for bringing it down to Earth. I really think that the term "dark matter" was a poor choice. It sounds cool, but it seems to rub people the wrong way.

[imported_Tintin]

The good thing about a pseudonym is that you can ask nonsensical questions without feeling ashamed

Does anyone know who it was who coined the terms dark energy and dark matter ?

Tinnin'

[Faulkner]

We are told that the universe is structured like the surface of the earth, but in 4(?) dimensions instead of 2! So in effect there is no "centre" or "boundary", but a seamless, endless "finite infinity". So I imagine if one travels in a "straight line" (if this is possible?) one would arrive back at the starting point! SO...relating this back to dark energy & the repulsive force of gravity...COULD IT BE that gravity is not in fact "repelling", but what we are observing is gravity "attracting" at long distances, matter looping back on itself, kinda thing. Hmm, hard to explain properly...does this make sense? In other words, we are seeing distant galaxies NOT accelerating AWAY, but accelerating TOWARDS us (but from another direction)!... well, I know I sound crazy, but believe me, it's just my inability to put this properly into words! Ha! I still find it IMPOSSIBLE to visualize such a universe. My commonsense tells me the universe MUST have boundaries, the "edges of the Big Bang", so to speak. Also, doesn't Hubble's latest findings of a "flat" universe (rather than a "curved" one) rule out this whole notion of a "finite universe" with "no boundaries"??

I guess, in a nutshell: I'M MINDBLOWN AND CONFUSED!!!!! :blink:

[Fraser]

The Universe isn't curved the same way the Earth is. If you head off in a straight line, you will never return to your original position.

[kashi]

Because space and time are both curved, maybe time curves around on itself. It's weird and counterintuitive. I think I'll stop thinking about it.

Kashi

[Faulkner]

Hmmm...well OK...but why do cosmologists describe the expanding universe in terms of an inflating balloon with black dots on it representing the galaxies? Is there a better way to describe the universe's geometry?? Are we talking a 3D universe, or multi-dimensional? I'm flabbergasted. How can there be no "edge" to this universe?? If the universe has no "edge", then it is either infinite (which goes against the Big Bang theory) or it warps back upon itself in some geometrical trickery!!?!... In which case, yes, you WOULD arrive back at your starting point, wouldn't you?? Cosmologists seem full of convoluted ideas that simply cannot be translated into layman's terms. :wacko:

[NeoDinian]

Dark matter was first used by Carl Sagan. I belive dark energy (as well as dark matter) was Steven Hawking.

[polymath]

This is the most fascinating discussion I have seen on the Net for a long time. I am in the same position as many contributors in that I am confused about the relationship between dark matter and dark energy. Before dark energy was discovered, dark matter was said to make up more than 95% of the Universe. Now that we have dark energy, the percentages seem to be 73% dark energy and 23% cold (what's that?) dark matter. I am taking these figures from a Sky and Telascope report on the findings of the WMAP satellite of earlier this year. So there must be some connection between dak matter and dark energy if they are both thought to be constituents of the Universe. Or have I completely misunderstood!

[Arramon]

I would say that we may need about another 5 years max to truelly chart and dimensionalize the degrees at which 'matter' and 'energy' flood our regions of galaxies and galaxy clusters...
I was just reading from a ESA website that they now believe that dark matter may be used as some sort of 'smeared paste' that helps 'draw & stick' galaxies together... it was from a team that was given like 100 hours of hubble time to examine a cluster of galaxies, or a certain range of sky...
it was previously thought (and said by me in here =P ) that dark matter may be more condensed towards the outer regions of a galaxy or cluster, but with these new findings, its being said that the dark matter may be less condensed towards the outer regions and more the closer in to the center of the cluster or galaxy you go... and that dark matter also clumps together in places, which could then attract galaxies together that may be close enough to eachother...
...and that the expansion of the universe may have been slower at first, because of high gravity, but then accellerated the farther the expansion due to the effects of dark energy...
i believe the team plans to release a mapping of this cluster that they were studying, a detailed chart of where dark matter & other compounds lay, the relations to each, pulling/tugging, the temperatures and the speeds that the particles may be repulsing at from the surrounding dark energy...

all very interesting... but this may change in a heart beat from someone else's studies... or alot of heart beats... whenever...

i give them 5 more years to be able to speak with any form of certainty...

. ..-={A}=-.. .

[Arramon]

Bling bling, said the scientist... =P

Check this article out about Dark Energy just released...

hmm...

. ..-={A}=-.. .

[budcamp]

We have no idea if either dark energy or dark matter exist. They are theories, which were created to solve a particular problem. They are not even really to the theory point. They are more like theory wannabe's.

Dark matter was created to solve the problem of what holds galaxies together. We watch them spin and compute that they should be spinning apart, but they are not. When all of the mater we can see in them is calculated, there is not nearly enough to hold them together. So what is it that holds them in place.

If it is mater, it does not reflect or emit light: x-rays, infrared, or radio waves. Is there a possibility that it is not there? There certainly is! It is possible we do not understand gravity as well as we think we do.

Dark energy is not nearly as likely to exist as is dark matter. Dark energy was invented when two research teams studied (I believe nine), super novae. They concluded that these nine objects were farther away than they should have been. They transposed that conclusion into the fact that the entire universe is accelerating. I know everybody needs their fifteen minutes of fame, but it is quite a stretch to accelerate billions and billions of galaxies based on the observations of nine stars. Even if they are correct and the universe they observed was accelerating, it was doing so eight billion years ago, which is the look back in time to where the observations were made. We have no idea of what those stars are doing today.

This is not much of an answer, but then there are no really good answers on this subject. We call them "DARK" because we know nothing about them.

Bud

[Arramon]

...thats a point that people seem to keep wanting to say...

i think i've read about 10 post like that....

It doesn't hurt to try to organize the chaotic into thinkable structures...
....and if the structures are proven to be otherwise later on, then the organizing can be altered to fit the newer findings....

its the process of where we are at now... we can't see into the future to know what others may find.. we can just try to organize our work now, so that others down the way can use this data to try and evaluate their own findings...

...and to call something by a particular name doesn;t put a branding upon that name that will stand beyond the test of time... names can change...
and maybe Dark matter, or Dark Energy, may be realized to be another form of Light Matter and Energy.... electromagnetic sources that produce their own currents and tows and forces....

In order to realize the extent of the universe, we must have knowledge banished from the forefront of our current minds, our current time, our current thoughts and processes of learning.... leave an open mind to allow all forms of information to enter for analyses... acquiring all data before computing a possible fact that should or shouldn't be..... theories don't claim to be facts.... its the ones who cliam that these theories don't exist or CAN'T exist that are claiming these theories to NOT be facts....

I, for one, will allow the theorists to strive as hard as they may.. for they are the ones who are conquering the unknown.... and are allowing us to learn more and more each day, each year, each decade, each moment....

Hail to these leaders who are unknown to most, but will forever be known to the likes of us who believe in the ways of discovery...

. ..-={A}=-.. .