dark matter

just_some_guy · Feb 18, 2005

Has anyone heard an explanation for why we see no gravitational evidence for nonbaryonic dark matter in our solar system?

yevaud · Feb 18, 2005

Sure. Notice that 99% of the evidence (such as there is) as to it's existence is in the voids between galaxys? That's because stars, singularities, and solar systems sweep up most of the matter around them. Don't forget that anything that possesses mass is effected by gravity, after all. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

just_some_guy · Feb 18, 2005

Fair enough. That explains how the dark baryonic matter (ie., atoms, us, planets, furry bunnies etc.) gets swept up. But baryonic stuff is supposed to account for only a small proportion of all dark matter. We see plenty of evidence of "normal" matter in our solar system, but to my knowledge there is no evidence of nonbaryonic matter in our solar system (apart from neutrinos) - there should be lots of it around if it is influenced by gravity. Shoudn't there?

yevaud · Feb 18, 2005

Borman: thank you. I didn't have the time, at that moment, to do more than pop off a quick, off-the-cuff explanation. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

just_some_guy · Feb 18, 2005

Thanks Borman, interesting theory. I wonder if there is some property of CDM that causes it to be repelled by star-forming processes. I've no idea how such a property would fit in with the observations of elliptical V's spiral galaxies though!

tom_hobbes · Feb 18, 2005

Cracking thread guys. Borman, I'm an idiot so please treat me gently. Would the halo of dark matter be spherical or disk shaped? And if galaxies are surrounded by halo's of dark matter substantial enough to account for the velocities of stars around the hub, what effect if any should all this non baryonic stuff have on the observed luminosity of galaxies? Wouldn't it serve to dim the light that we see emitted from them? Wouldn't we be able to spot that fairly easily? <div class="Discussion_UserSignature"> I wish I could remember But my selective memory Won't let me - Mark Oliver Everett </div>

ehkzu · Feb 20, 2005

Unfortunately this goes both ways. Remember, the discoverer of plate tectonics got run outa geologist town on a rail, so to speak. And Einstein was not down with quantum physics. So we're left trying to leap off the edge of what's proven very, very carefully. I suppose the one law that keeps getting re-proven is Occam's Razor, which is what you're applying here.

Saiph · Feb 20, 2005

actually, both are very much as troublesome as the media presents. There is a lot of controversey around dark energy (since we have no clue what it could be, or if it's there) and dark matter (which we know is there, but don't know what it all is). As we find more forms of matter that eluded us in the past, e.g. more brown dwarfs, red dwarfs, bh's, gas clouds, etc. We fill in more of what dark matter is. But we don't know if it's only regular matter. What the media doesn't portray is the discussion, debate, and science around these concepts. They present it as a "matter of fact" more often than the truth, which is a "work in progress". <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

mikejm · Oct 21, 2005

I was discussing this on another forum and was getting nowhere. Apologies if this has been discussed in a previous thread, this is my first post. Is it not obvious that the whole big bang theory is wrong when you consider that nothing is supposed to have existed before the big bang right? So, how can something be created out of nothing, I mean this is scientifically impossible. The notion that gasses reacted with eachother in space to form a massive explosion seems viable yet no-one provides an explination as to how these gasses came literally out of nowhere and what was the space they existed in. I realise in Einstein's equation (E=mc^2) it is possible for matter to be formed from energy or at least it has to be the same as energy, but where did the energy come from in the first place? The argument I received from the other forum was "if god created the universe where did god come from". this led me to consider that this question would only be possible to answer if you put "god" in the same context as matter and, whether god exists or not, this idea is unrealistic. I do not intend this post to be a debate about the existance of god but I think it helps to consider that there may be more than one level of existance. I mean no one really knows what "dark matter" is and yet it is said to occupy around 87% of the universe, so that is a massive majority of our own existance that we don't even understand! What makes us think our comparitively tiny minds have the whole thing figured out? I'm not really sure of the general views of this sort of topic are on this forum, like I say I'm a n00b so, bonus if it's well received if not let the flaming commence!

j_rankin · Oct 21, 2005

As i've explained in another post somewhere on this board, i believe that the universe is the result of inevitability. Since it is impossible for nothing to exist, every possibility exists instead, and time is the exploration of everything that's possible between the two extremes of possibility. That also explains how we exist. If it's possible for atoms and molecules to arrange in the way they do to create sentient life...then between the extremes of possibility, it is inevitable that sentient life will be created.

bonzelite · Oct 21, 2005

well, i get flamed for posting anything that remotely questions any of the sanctified accepted models for cosmology. like black holes and the big bang. beware that the big bang is being accepted as a fact. and if you disagree then you are a "fool." or you "know nothing about physics." yes, this has been talked about ad nauseum on here even in the short time i have been here. and will be again and forevermore.

bonzelite · Oct 21, 2005

i agree with this: "As i've explained in another post somewhere on this board, i believe that the universe is the result of inevitability. Since it is impossible for nothing to exist, every possibility exists instead, and time is the exploration of everything that's possible between the two extremes of possibility. That also explains how we exist. If it's possible for atoms and molecules to arrange in the way they do to create sentient life...then between the extremes of possibility, it is inevitable that sentient life will be created." it is similar to saying that it is plausible that every book ever written is in a potentiality within the dictionary. if you get an ape to pick out words an infinite amount of times, eventually, the ape will arrange the words into the form of "war and peace" someday, in an infinite timeframe from the point from which the ape began picking out words. but it does NOT answer the question in physical terms about the origin of the universe as it is today. or where it came from. or what came before it. it is my belief, however, as you have basically stated, that the universe is an infinite state of potential. it always existed. i do not believe in a big bang.

j_rankin · Oct 21, 2005

The universe is a permanent thing, since it's impossible for there to be nothing. This does not rule out the big-bang because it is possible for only one thing to exist. There are limits to the possibilities because one of the extremes is that only thing thing exists - so therefore everything that is possible must be bound to the possible results from that extreme. And there we have our physical universe. You cannot take one point in time and then go straight to the next point in time and see a completely different universe.

bonzelite · Oct 22, 2005

i feel we agree but create the idea that we may not. to me, a big bang implies impermanence, as there was a beginning. so this universe, per that idea, was not permanent, but was introduced as a new object. it was not always here. a truly permanent universe is of no conceivable orign or end. that it may have derived from a prior state of non-existence, of nothing, is to suggest that the universe was not infinitely, potentially able, to have existed forever. so its permanence today, which may be such actually, is contingent upon having had a beginning. is this the possible result of the extreme you speak of? if so, then i can agree for sake of argument and context that we can "buy" that. we can have a permanent state today from a beginning. on the other hand, it seems asymmetrical: there is nothing, then suddenly, there is everything, and a complete permanence of that state, replacing the already steady non-existence. a balanced reality, perhaps, is a simultaneous state of nothing with the known universe that is defined against its opposite: nothing. and the nothing would not be what it is without the universe: something. but the nothingness prior to the universe is undefined. as is a singularity of infinite density that is collapsing forever, or exploding from an infinite density. or if we define it as a permanent and infinite state of probability, this pre-big bang nothingness, then that would assume, too, that a spontaneous explosive point of infintesimal smallness could, too, exist. so maybe the big bang did happen. it could have happened provided that its potential to exist was part of a nothingness state of infinite potentiality. and the odds were infinite that it would or would not happen. and it just happened to get lucky and it did happen. as well, you would have to include every other possible state that could arise out the nothingness, including a potential for infinite nothingness to continue existing

kmarinas86 · Oct 22, 2005

An alternative to the Big Bang http://en.wikipedia.org/wiki/Cyclic_Multiverse_Theory http://en.wikibooks.org/wiki/Cyclic_Multiverse_Theory Or... http://academia.wikicities.com/wiki/Cyclic_Multiverse_Theory

j_rankin · Oct 22, 2005

I too agree with most of what you are saying. However I believe that the stalemate between everything existing and nothing existing is exactly what causes the universe to exist and expand over time and also accelerate its rate of expansion. If we imagine that the universe is an entity trying to reach perfection, then we can see why the universe is growing larger. It is trying to become 'everything' (in a physical sense, not an endless possibilty sense), while it started off as 'nothing'. Perhaps the universe will not stop accelerating until everything in it reaches the speed of light, and therefore has infinite mass. The second it reaches infinite mass, it will become a singularity once more and the big-bang will occur again. If time is a dimension, then perhaps time itself is the energy upon which the universe is fueled to accelerate, but this is all speculation. Interesting though.

bonzelite · Oct 22, 2005

that is very interesting.

newtonian · Oct 25, 2005

mikejm - Welcome. Excellent first post! I agree that something cannot come from nothing. However, sometimes, as in the vacuum of space, "nothing" is not absolute - as in the appearance of virtual particles seemingly from nothing. Most scientists agree that the latter observation does not violate the law of conservation of matter and energy, nor does it violate causality - i.e. that is that everything that exists is a result of cause and effect. In short, our universe was not created from "nothing" in the absolute sense. The simplest answer would be to choose between the only two possible origins of everthing, namely: 1. A first cause, or First Cause, as in God. E.g.: "In the beginning God created the heavens and the earth." - Genesis 1:1 2. An infinite number of past causes and effects. The Bible teaches choice #1. I concur. Isaiah 40:26 links the existence of stars with God's dynamic energy and plural forms of power: (Isaiah 40:26) . . .“Raise YOUR eyes high up and see. Who has created these things? It is the One who is bringing forth the army of them even by number, all of whom he calls even by name. Due to the abundance of dynamic energy, he also being vigorous in power, not one [of them] is missing. Footnote - “Dynamic energy.” Heb., ´oh·nim´, plural.; Lat., for·ti·tu´di·nis, “fortitude.” Note tha ohnim is plural, and this implies there may be forms of energy scientists have not detected which leave the false impression that something can come from nothing, when it is actually being converted from this undected form of energy. Or undetected plural forms of energy. As in dark energy, for example.

newtonian · Oct 25, 2005

borman - Hi! I am the former paulharth6. How are you? On that first camp: Dark matter could, of course, include ordinary matter that is simply too dark to observe - as in faint brown dwarfs for one of many examples. Now, I seem to have a mental block as to what stands MOND stands for - I will look it up. OK, from dictionary.com acronym definitions: What does MOND stand for? Modified Newtonian Dynamics (missing dark matter theory) And LCDM? Dictionary.com lists these two definitions, neither of which fit your context: LCDM Large Component Development Management LCDM Life-Cycle Document Management My guess: Last Chance Dark Matter? Can you please explain! Also, what's new in the attempt to explain the anomalous slowing of those long distance space probes? Clearly this can involve unknown causes for acceleration and also dark energy. Could dark matter and dark energy be linked in a manner similar to the way ordinary matter and ordinary energy are linked (as in e=mc^2)?

newtonian · Oct 25, 2005

J_rankin - Why do you believe it is impossible for nothing to exist? I agree, btw, and here are three reasons: 1. The law of conservation of matter and energy. 2. Causality, the scientific observations of cause and effect. 3. God, as the First Cause, always existed. Why do you believe every possibility exists? I disagree. It was possible for me to post Saturday on SDC, but I did not as I was busy in Katrina relief. Or do you think that because it was possible for me to post, that therefore I did post? Do you see the problem with that belief?

j_rankin · Oct 25, 2005

In another post in this thread i wrote: "There are limits to the possibilities because one of the extremes is that only thing exists - so therefore everything that is possible must be bound to the possible results from that extreme. " I agree with what you are saying.

j_rankin · Oct 25, 2005

I believe it is impossible for nothing to exist because that would mean that 'nothing' would be 'everything'. That is a paradox. Every possibility (between everything and nothing) is being explored by time. When everything reaches the speed of light, there will be no time left and so all the energy of the unvierse creates a new singularity (the big-bang) and it all goes back to when there was no time. That is my belief.

the_masked_squiggy · Oct 26, 2005

Wow, I'm sorry that it's taken such a short time for you to become bitter with the forums. I personally have no problems with honest discussion and debate about things. Even if you challenge popular beliefs. Sometimes it's the attitude of the person posing the arguments that ruffles feathers. Perhaps a different approach is in order? I've noticed that I jump the gun myself sometimes in taking insults to heart. Also when people argue the existence of something proven by observation and measurement that others around here start getting uppity. Not that they're not willing to explain why it works, but they get impatient when they point at the elephant in the room, describe how it got there, take measurements of the size of its tusks, and are then told that their educations are worthless. As for how often things are talked about...there are new people all the time. Why should we only talk about new things and leave them out of the old ones?

Saiph · Oct 26, 2005

bonzelite: <blockquote>In reply to:<hr />well, i get flamed for posting anything that remotely questions any of the sanctified accepted models for cosmology. like black holes and the big bang. beware that the big bang is being accepted as a fact. and if you disagree then you are a "fool." or you "know nothing about physics."<hr /></blockquote> I hope you don't take my comments as a personal attack at least. I'm discussing the idea you present (which I may disagree with), and am making no judgement on you personally. Now, part of what you pick up is some defensiveness, as what you post doesn't always read as questions or doubts about BB and BH's, but as a categorical denial of their possibility. When that happens, people get a bit defensive, and the tone of the responses can get a bit sharp. Just take a look at the post and see if they are talking about the idea you brought forth, or you yourself. And if they do specifically say you know nothing about physics, or are a fool, ignore it, or try to glean the actual useful information from it. The first one is a not so kind way of pointing out you may wish to brush up on material at hand (Both sides of the issue, e.g. look at why it is believed BH's are real by most). But remember, people get a bit hotheaded. If you pay attention only to their arguements, not their "flames" when they arise, things work out (this does mean you may end up ignoring entire posts). Take me for instance, I get railed at constantly, but I have never been in a "flame war" because I don't really respond to it. I don't take it personally, such behavior erupts when you critique anybodies closely held opinions about anything (wether the opinions are right or wrong). <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

newtonian · Oct 26, 2005

bonezelite - That post about nothing was something else! To me the origin of the universe must involve something - in view of the law of conservation of matter and energy and the scientific observations of cause and effect. Simply stated: "In the beginning God created the heavens and the earth" - Genesis 1:1 Note a beginning. Isaish 40:26 links the existence of stars to God's dynamic energy (in plural in Hebrew). How many plural forms of energy have we failed to detect, thus assuming "nothing" when there is actually "something" - or more accurately something else! In short it was something, likely something else, that caused the "big bang" or beginning.

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