Dark Matter and Dark Energy...

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claywoman

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Okay...I just watched a program on Scientific America Frontiers on the universe trying to explain dark matter and dark energy. I think I'm more confused then when I started.<br /><br />The push/pull I sort of got but how are you going to find something that isn't visible or measurable? How do you know its out there? Help?<br /><br />Also it said that our universe slowed down its expansion but is now expanding faster? Huh?
 
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Maddad

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They are two separate ideas, and both are guesses that attempt to explain something we've seen but do not already understand (hypothesis). They have not been tested, a basic requirement for a hypothesis to become a theory, so both of these are very tentative.<br /><br />http://csep10.phys.utk.edu/astr161/lect/history/kepler.html<br />We measure the mass (weigh) of planets, stars, and galaxies by timing how long it takes objects to orbit them. The faster the objects orbit, the more massive the star. Johannes Kepler worked out the relationships in the early 1600's. It is extremely predictable, allowing us to measure the planets and the moons with great precision.<br /><br />Dark Matter<br />One of the very basic assumptions in science is that rules that work here, today, will also work there, tomorrow. When we measure the speed stars orbiting some distant galaxies, we notice that the mass of the galaxy they circle must be very heavy. However, when we count up all the stuff in the galaxy, we come up with a smaller figure for their weight (mass actually). We also see something difficult to explain with Keplarian laws in our own galaxy. The further stars get from the center of the galaxy, the slower we expect them to orbit. What we actually see is that they orbit faster than they should as they get further from the galactic core. One explanation for these observation, hypothesis, is that there is more stuff in these galaxies than what we can see. Quite reasonably we have been calling it dark matter because it doesn't give off enough light for us to be able to see it.<br /><br />There are all sorts of attempts to find this dark matter. Collectively, we have indeed accounted for some of the missing matter, but there is still more that we believe is out there.<br /><br />Other Explanations<br />We have not given much thought to other explanations than dark matter. One reason may be tha
 
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Maddad

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Dark energy is even less secure than dark matter. In the model (a way of thinking about it) of the big bang that we had before about ten years ago, the universe exploded into existence 14 billion years ago and went flying out in all directions. We wondered whether it was expanding so fast that it would continue forever, or whether it would slow down and fall back together again at some time in the future. The more stuff in the universe, the more gravity it would have, so the more likely it would be to re-collapse. If there wasn't enough stuff, then it would expand and expand and never stop. Once troubling aspect is that we had almost exactly the critical amount of stuff. Why should there be, just by coincidence, just enough to exactly balance the job done? We've been working on explaining that part of it.<br /><br />Then about 1995 an amature astronomer figured out that the light from 50 or so supernovas could be statistically used to measure how much the expansion of the universe had been slowing down. It was a tough assignment to catch these supernovas, but he worked out a technique and by 1997 found 42 of them, enough he thought.<br /><br />Understand that he thought he was going to be measuring how much the expansion had slowed. What he wound up measuring is how much the expansion had speeded up. This was sort of a blindside right cross to the temple of a boxer; it knocked all the astronomers cold. How could the universe be expanding faster? Nobody knew.<br /><br />Dark energy is a hypothesis to explain why we observe the expansion of the universe speeding up. The idea is that there is a hidden energy in the vacuum of space that pushes space itself apart. The amount of this dark energy is dependent on how much space there is. More space means more dark energy. When space expands, that means that you also have more dark energy, so space gets pushed apart faster - the expansion accelerates.<br /><br />As you might guess, I don't like this dark energy any b
 
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claywoman

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Thank you Maddad, this made it a little clearer but brings up more questions then it answers....<br /><br />This to me is a hard concept to understand and they were talking in a language I didn't really understand. It almost seemed they were talking a foreign language. I was trying to figure out the explanation of why the further away from the center of a galaxie the stars are like in a spiral galaxie, the faster they rotate? I'm still trying to figure that one out. My mind isn't as young as it once was.<br /><br />Is this where the dark matter/dark energy comes in? because of some mysterious gravitational pull? Help me out here, I'm not even sure if I'm saying this right....
 
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Maddad

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Well, you're not alone if it confusticates you. It does everyone. The stars should rotate slower as you move further away from the center. Right now we don't know why it happens.
 
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dlee0708

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<i>Well, you're not alone if it confusticates you. It does everyone. The stars should rotate slower as you move further away from the center. Right now we don't know why it happens. </i><br /><br /><br />To me this is the most fascinating thing in my entire lifetime. And what I don't understand is why everyone is so bent on getting man on Mars in 30-50 years. If it were up to me I would be putting tons more concentration on building things like the Kepler telescope and designing Kepler II, Kepler III, Kepler IV etc till we figured out what was going on. I am not saying touching the robotic missions to mars, but I would abandon the manned missions or at least WAY scale back on it and put more concentration on what is so bizarre out there.<br /><br />-Don<br /><br />
 
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newtonian

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claywoman - Hi!<br /><br />Dark Matter: <br /><br />First, I would class dark matter into three categories:<br /><br />1. Ordinary matter that is relatively dark and therefore not observed. This would include extrasolar planets, brown dwarfs and other faint stars too distant to observe, small masses, etc.<br /><br />2. Exotic matter - unknown, theorized about, but not yet discovered. Neutrino mass has, if I remember correctly, gone from this category to the above category.<br /><br />3. Imaginary matter - These are various postulated forms of dark matter that do not actually exist except in scientific theories, hypotheses and speculations which will eventually be proven wrong.<br /><br />However, it is true that galactic rotations in outer belts indicate the existence of a halo of dark matter in outer areas.<br /><br />Normally, outer layers revolve slower so as to stay in orbit - faster would cause escape velocity.<br /><br />I will post a quote later after I type it out.<br /><br />[One of my theories: matter beyond our visibility horizon (perhaps expanding FTL {faster than light}) and attracting our universe by a domino effect causing acceleration of expansion - an alternate theory to dark energy]<br /><br />Dark Energy- AKA vacuum energy (as a property of space or space-time), AKA cosmological constant (as in Einstein's calculations).<br /><br />This could be more than one form of energy.<br /><br />For me, this would be the energy(s) God is using to stretch out our heavens like a fine gauze (see original Hebrew) as in this quote:<br /><br />(Isaiah 40:22) There is One who is dwelling above the circle of the earth, the dwellers in which are as grasshoppers, the One who is stretching out the heavens just as a fine gauze, who spreads them out like a tent in which to dwell, <br /><br />Astronomers use similar terminology in describing the nature of our universe with its threads, filaments and walls and overall stretching gauze-like appearance.<br /><br />Were gravity the only form of ene
 
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dlee0708

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<i> Understand dlee that the distances we're talking about for the expansion of the universe are REALLY huge. The distance to Mars is microscopic by comparision. </i><br /><br />maddad, <br /><br /> I really don't understand how your comment has anything to do with telescope projects to understand Dark Energy. I am not saying actually going into the far reaches of space to see what is out there (it would be nice if we could, but I am positive in my lifetime this will never happen, possibly it will never happen), I am saying building telescopes to understand what is going on out there which we clearly don't understand (and you VERY clearly put into words).<br /><br /> When I heard Bush's speech he said that the money for the currently planned projects that aren't alligned with the Man to Mars mission and are not necessary that money was going to be diverted. This would mean all the Hubble type projects were going to be dead. I was one unhappy camper.<br /><br /> Fortunately it seems like this isn't happening so I think this whole Man to Mars mission is dead, but everybody seems to want it and I just don't understand why. I think it would be so incredible if we found out something as incredible as we did in the 1600's when we figured out the Earth was not the center of the Universe and I think this Dark Energy could be something like that. Who knows maybe with this knowledge we could get into far space, right now we just don't know squat and we really can't even make guesses because this universe expansion thing just doesn't make any sense.<br /><br />-Don<br />
 
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newtonian

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Don (dlee0708) - You posted the same minute as I.<br /><br />Note that this whole expansion thing does make sense to me (see my above post), though I agree with you that the details will likely be awesome and amazing as we discover them!
 
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Maddad

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dlee0708<br />"<font color="yellow">I think this whole Man to Mars mission is dead, but everybody seems to want it and I just don't understand why.</font><br /><br />It is extremely important that we establish life somewhere else beyond Earth. As it currently stands, a single event, such as the impact of a large asteroid, could end the only life known to exist in the universe. An outpost on Mars so far appears to be the most achievable solution.<br /><br />By the way, we have one member at SDC who is working to give our astronauts the technology to live on Mars. JonClarke's team is creating and testing the devices these people will use. The logs are available online, as well as photos of him in spacesuits.
 
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claywoman

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I'm finding this thread so very interesting but still somewhat confusing. Okay probably a stupid question but couldn't the forces that cause the outer planets to rotate faster in a solar system be the gravitational pull from another solar system? therefore again, it be something we can explain instead of the unexplainable?<br /><br />Also, do you think we will ever in our lifetimes, see either dark matter or dark energy? Or will they remain mysteries? Now on a color wheel, black which is what I picture 'dark' to mean, is instead of the absence of color, just the opposite, it's the combination of ALL colors. therefore wouldn't all the spectromic systems that we have now detect SOME color that is unexplainable?<br /><br />Just some ramblings from a very confused mind here...
 
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Maddad

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The increased speeds we're seeing are on a galactic level, not with anything as small as the solar system. The galaxy is 100,000 light-years across, while the solar system is about seven light-hours across. This makes the galaxy ten million (10,000,000 or 10<sup>7</sup>) times bigger than the solar system. While we can measure the effect for the entire galaxy, we cannot measure it for anything as small as the solar system.<br /><br />The explanation for it will be a hypothesis. There are a few floating around, but so far none of them are very satisfying. When one comes along that stands up to testing, then we'll be able to call it a theory. Once that happens people will gradually accept the new idea, and after a time that will become the accepted reason for the observation. Right now though we don't have anything that answers that challenge.<br /><br />The equipment we have now isn't seeing any light at all from sources that we've identified as having dark matter. Without any detectable light at all, it doesn't do us any good to talk about what it's color is. We'll know that once we see some light from an object that was previously dark.<br /><br />By the way, sometimes the normal by-product of a successful hypothesis is a new branch of science that we didn't have before. On a less dramatic level it may just refine our current understanding of nature. However, this one has the earmarks of being a big new development.<br /><br />I dunno whether we'll ever get hard observational evidence for dark energy or dark matter. Sure, I'd like to see it in my lifetime, but it's a bit elusive at the moment.
 
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Maddad

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http://www.maddad.org/astronomy/<br />http://www.maddad.org/astronomy/galaxies.htm<br /><br />By the way, if you haven't seen any galaxies, I've got a couple of high resolution ones on the astronomy section of my website. High resolution means a big picture, one that will be wider and taller than your monitor. It also means that it will take longer to download than a smaller picture. But it also means that it will be very clear, showing excellent detail. Andromeda and Spiral Galaxy NGC 3370 are both excellent.
 
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Maddad

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I've been wondering about the pioneer anomaly for a year or so. If you figure it out, you tell me what it is.
 
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nacnud

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How about<br /><br />1) Modified Newtonian Dynamics (MoND) [wikipedia] <br /><br />2) Gravity is different when applied at normal to the direction of motion to when applied parallel to the direction of motion.<br /><br />3) Er... someone got the sums wronge or forgot to account for a small known effect.<br /><br />Its a good mystery though.
 
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dlee0708

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<i>claywoman:<br />Also, do you think we will ever in our lifetimes, see either dark matter or dark energy? Or will they remain mysteries?</i><br /><br /><i>nacnud:<br />What about the pioneer anomaly? <br /></i><br /><br />If we were to follow Bush and his Man on Mars initiative where we funnel non-necessary projects that don't help the Man on Mars intiative it would be extremely doubtful we would figure out what Dark Energy, Dark Matter or the pioneer anomilies are which to me would be an absolute crime. But like I said before, it doesn't look like to me this is really going to happen.<br /><br />-Don<br />
 
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tiffanyholly

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Hi:<br /><br />I think what you call dark matter or dark energy is the zero point field or the fabric of space-time itself. I think the reason for the acceleration is that the fabric of space-time is like a rubber band. The initial "Big Bang" or sudden expansion has reached a point, whereby, the expansion is really no longer happening, and what you are observing is a contraction of space-time, hence the observation of acceleration of dark energy or dark matter.
 
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tiffanyholly

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Hi:<br /><br />In the Hindu Veda's and in Tibetan Buddhism they talk about a never ending, cycle, of creation and destruction. I think this flat universe of ours, is exactly how the eastern religions see it. The fabric of space-time as Einstein predicted in the General Theory of Relativity is warped by a Large body such as the sun, whereby, the planets follow a certain path because of the indentation on the fabric of space-time. Einstein said the fabric of space-time is like a rubber mat it can expand and contract. That is why I have no doubt that what we observe as dark matter or dark energy, are really the same thing, and that the fabric of space-time is now contracting, whereby, just like a rubber band when it contracts, dark energy-dark matter are creating the acceleration of the Universe.
 
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tiffanyholly

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Hi:<br /><br />It would be great if my theory could be proved. I also believe that this contraction of space-time will end in a singularity event, whereby, all matter and energy in the Universe is contracted to a single point, and then another "Big Bang" happens, re-creating our Universe again in a never ending cycle.
 
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tiffanyholly

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HI:<br /><br />A lot of my theory comes from Paul Steinhardt at Princeton University. The Ekpyrotic Model of the Universe is probably the correct analysis of how it works. You should check this theory out. All recent data is pointing to this model.
 
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claywoman

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I am so confused here, but the picture is getting a little clearer, I think...thanks guys...
 
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