Universe

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[nexus555]

In order for the universe to accelerate there has to be a force acting upon the space/time fabric. That is a must in our current laws of universal mechanics. I can see that the universe is expanding due to the big bag, but something is causing this acceleration.<br /><br />As I said in a previous post, how do we know that we're expanding and not contracting? What if you went to the other side of the universe from us, and to a viewer there, the "expansion" seemed to be opposite from our perspective? There has to be some form of energy or antigravity acting upon the universe. I'm not saying for sure that it's dark energy or matter, and I don't agree with those theories however it can be possible. <br /><br />Until we have a universal perspective, we will not know. Maybe our small portion (could be billions of lightyears) seems to be expanding, but some other part could be different. Maybe the universe has a spin and simply appears to be expanding.<br /><br />In the end, we don't know, we can only speculate and make theories.

 

[search]

Not quite so Nexus555<br />You are thinking in linear terms.<br /> <br />Remember the example of the chocolate cake with nuts (you can choose your prefered type of cake) in the oven. As it cooks it gets bigger and the nuts get further away from each other. We are in one of these nuts (our galaxy) and if you would go to any other nut or to the outside edge of the cake you would still see all nuts getting further away from each other. <br /><br />If someone would go "to the other side of the universe" (if there is another side since we do not know sides of the universe) it would still see the galaxies redshifting which getting away. Galaxies are getting further away from each other except those which belong to local groups and the reason is that distance between these galaxies is small enough for the force of gravity to be stronger than the force which is driving (whichever it may be) the accelerated expansion.

 

[alokmohan]

SEARCH,you mean this is dark energy.

 

[search]

That is one of the question in this universal puzzle.<br /><br />If the universe is accelerating as the WMAP data (and the following must be emphasized: the WMAP data can fit various theories but the one it appears to fit best is the Standard Model-Lambda CDM) Dark Energy could be the reason.<br /><br />I have posted this link several times but its never too much to post it. Again this is the WMAP first year results and they are different than the 3 year only in accuracy so do not worry if you will see values similar but within ±1-2% different in other sources.<br />http://map.gsfc.nasa.gov/m_mm/mr_limits.html<br /><br />We have to remember that there are competitive theories in play and competitiveness is intrinsic to man. <br />Either you are a scientist or a regular reader it is normal to fall in love with some theories rather than others and humans (as well as animals) are quite mean when defending their object of love.<br /><br />Some fall in love with Dark Energy others, Quintessense, Super Attractive Force at the edge of the universe, etc...<br /><br />However if you notice there is two things in common with these names: they all try to explain acceleration (not expansion alone) and they all are "attractive names".<br /><br />Who does not like the idea of having a misterious invisible Dark Energy or an exotic quantum Quintessense or even a 5th force located in the outskirts of the universe?<br /><br />I do not know which one it is but I do know that for the laws of physics to be correct (and they could be wrong) something really strange is happening. I believe that in the very near future once the instruments get more precise and our observation more refined we will narrow our margins of error and we will be able to continuously test Einstein theory of relativity until the last decimal of its precision. <br /><br />One day it may break and that would not make him less of a great mind, but if not, more rem

 

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Universe Song

 

[weeman]

The Universe song is a good one <img src="/images/icons/smile.gif" /><br /><br />What point in space are we seeing this accelaration? I have heard it is somewhere on the order of about 7 billion lightyears away. Of course, is it possible for this expansion to exceed the speed of light? Is it possible that all matter in the Universe will top out at lightspeed, but the dimensions of the Universe will continue to expand faster than light?<br /><br />It is most likely that all matter in the Universe will never travel faster than light. However, the dimensions of the Universe are not limited to any particular speed, so it is possible that the expansion of space itself can travel much faster than light.<br /><br />Going back to the nuts-in-the-cake analogy, the nuts (galaxies) are limited to a maximum speed, but the batter (the dimensions of space) is not limited to the speed of light. <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>

 

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<font color="yellow">What point in space are we seeing this accelaration? I have heard it is somewhere on the order of about 7 billion lightyears away.</font><br /><br />The answer to your question depends on the Universe model used and in knowing the density. I do not really think anyone knows the density of the Universe.<br /><br /><font color="yellow">Of course, is it possible for this expansion to exceed the speed of light? Is it possible that all matter in the Universe will top out at lightspeed, but the dimensions of the Universe will continue to expand faster than light? <br /></font><br /><br />Almost everything is possible when we are humbled by the Universe...<br /><br />The Hubble Deep Field: The Most Important Image Ever Taken

 

[alokmohan]

You may know fundumental thing that nothing can travel faster than light.Try to know some fundumentals also.

 

[dragon04]

<font color="yellow">Is it possible that all matter in the Universe will top out at lightspeed, but the dimensions of the Universe will continue to expand faster than light?</font><br /><br />The two are not discrete. Recessional velocity observation tells me that, I think. What kind of force could accelerate a galaxy with the mass of 100 billion suns, let alone a proton to and beyond the speed of light?<br /><br />I have to believe that recessional velocities are an expression of the non-Relativistic "force" acting on them, instead.<br /><br />I think that "dark energy" is an awkward attempt to identify a force acting from outside 4 dimensional space-time in terms of what we can observe.<br /><br />We can prove time and time again that matter (in our frame of reference) cannot exceed <i>c</i>.<br /><br />That had me in a dilemma trying to reconcile the Relativistic Truth with the problem of potential superluminal recessional velocities.<br /><br />That dilemma resolves itself if I am willing to believe one simple notion.<br /><br />If every galaxy (to simplify) is "glued" to a fabric that <b>itself</b> can expand at superluminal speed, then no rules are being violated.<br /><br />The remaining question would be whether or not "dark energy" within our 4 dimensional space-time is responsible or whether the force is acting from outside it.<br /><br /><br /><br /><br /><br /> <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[lukman]

<blockquote><font class="small">In reply to:</font><hr /><p> As for the singularity issue. Many galaxies seem to have a black hole (singularity) in its center. <p><hr /></p></p></blockquote><br /><br /><blockquote><font class="small">In reply to:</font><hr /><p> Dark matter seems to hold the galaxies together and explains the lack of matter in the universe to account for its density and fit the proposed theoretical model Lambda-CDM <blockquote><font class="small">In reply to:</font><hr /><p><br /><br />Can we have both dark matter and black hole at the same time holding galaxy together? If not, which does what? Thanks</p></blockquote></p></blockquote> <div class="Discussion_UserSignature"> </div>

 

[search]

<font color="yellow">Can we have both dark matter and black hole at the same time holding galaxy together? If not, which does what?</font><br /><br />Before continuing: <br />Black holes are objects predicted by general relativity. Dark Matter explains some phenomena in the universe.<br /><br />The black holes do contribute for some local rotation but do not explain the way galaxies seem to rotate. Vera Rubin showed that galaxies at the fringes move slower but as whole they rotate as a rigid body and dark matter is one explanation.<br /><br />Black holes have a localized effect depending on its Schwarzchild Radius (rs) and they contribute for accreting matter within the galaxy. Unless you are very close to it, a supermassive black hole contributes an insignificant amount of gravitational pull at a given point in a galaxy (other than the points within the rs).<br /><br />Dark matter explains (or some models infer dark matter from) the rotational speeds of galaxies, orbital velocities of galaxies in clusters, gravitational lensing of background objects by galaxy clusters, and the temperature distribution of hot gas in galaxies and clusters of galaxies. These and a few other effects seem to indicate that there is more matter than the matter we can see and that in some theories is called dark matter.<br /><br />Dark matter (or some other alternative explanation like MOND) may be the real candidates to explain how galaxies seem to hold.

 

[search]

Something else needs to be pointed out:<br /><br />Dark matter is what scientists call to the unaccounted and unseen matter of the universe. Matter that does not or hardly interact with other mattter and therefore does not produce light.<br /><br />There are several proposed categories:<br /><br />Baryonic dark matter (dark matter composed of baryons, i.e. protons and neutrons). An example are MACHOS-Black Holes fall in this category<br /><br />Non-baryonic dark matter which is divided into three different types:<br />Hot Dark Matter - nonbaryonic particles that move ultrarelativistically<br />Warm dark matter - nonbaryonic particles that move relativistically<br />Cold Dark Matter or CDM - nonbaryonic particles that move non-relativistically<br /><br />You have heard about the Lambda-CDM model. The actual accepted and most consensual model of Big Bang Cosmology.<br /><br />Lambda refers to the Cosmological Constant some kind of Dark Energy (74% universe energy density is believed to be in this form)<br /><br />CDM refers to Cold Dark Matter (non-baryonic, collisionless dust representing 22% of the Univere energy density believed to be in this form). <br /><br />The remaining 4% is what we can see (stars, planets and gas clouds)<br /><br />Quite amazing...

 

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It is an amazing Universe<br /><br />The Elegant Universe Part 1: Einstein's Dream (1/5)

 

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The Elegant Universe Part 1: Einstein's Dream (2/5)

 

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The Elegant Universe Part 1: Einstein's Dream (3/5)

 

[lukman]

Thanks SEARCH, i found a site so cool, it has many real media video clips for download, some of the titles are:<br />- Beyond-Standard-Model Models and Theories<br />- High Energy Particles from the Universe<br />- Accelerator and Reactor Neutrino Experiments<br />- etc<br /><br />Too bad, clips for "the elegent universe" is missing link. <br /><br />The site is http://lp99.slac.stanford.edu/streaming-media/download.asp<br /> <div class="Discussion_UserSignature"> </div>

 

[lukman]

Also:<br /><br />http://www.pbs.org/wgbh/nova/elegant/program_t.html<br /><br />but cant download them <div class="Discussion_UserSignature"> </div>

 

[lukman]

BTW, where can i get the dvd version of "The Elegent Universe" ? is product of Discovery? or anything similar by Discovery? thanks <div class="Discussion_UserSignature"> </div>

 

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The Elegant Universe Part 1: Einstein's Dream (4/5)

 

[search]

Hi lukman<br />I believe it is the product of NOVA<br /><br />Here is link and you can buy the dvd from them but I am sure you will find it in other places and inclusive ebay:<br /><br />The Elegant Universe

 

[lukman]

Thanks a lot <img src="/images/icons/laugh.gif" /> <div class="Discussion_UserSignature"> </div>

 

[slipstring]

Actually, there is a "before the big splash" as string theory with my modifications can explain the entire universe from before its beginning until after its end. <br /><br />I know string theory's on the rails now, as skeptical physicists say "but where's the proof?" Well, it's on its way, and it could be sooner than you think. <img src="/images/icons/smile.gif" /> String theory does have its problems, but they'll soon be corrected. <br /><br />M-theory was a brilliant expansion of string theory by Ed Witten which consolidated the 5 previous string theories into one comprehensive theory which now included membranes. However, because it relies on closed loop strings to explain gravity (which can escape our brane accounting for gravity's weakness) it relies on parallel branes in awkward positions "leaking" gravity to us in order to work properly which is not very intellectually satisfying. <br /><br />Being an astronomer in a wheelchair with lots of time to think, I spent many thousands of hours running simulations on my "mental model" of the universe I had been developing since age 8. After incorporating M-theory into this model, I was able to explain our universe from before start to finish. <br /><br />Some of those simulations included colliding membranes together in order to create new universes. During those simulations, I realized that dark matter could be explained by the vibrations imparted to each brane from the collision itself. Like two bubbles that bounce into each other (filled with a very thin brane fluid, similar to water in zero-g ), the branes would send shockwaves vibrating throughout each other, creating a spider's web network of dark matter throughout each brane after the collision. Where the branes vibrate the most, it would compress spacetime, as gravity is simply the curvature of spacetime. <br /><br />However, this would mean that the brane itself is what transmits the gravitational force, not the closed loop string gravitons of M-theory. The more

 

[kyle_baron]

First, let me say Welcome to SDC! I went to your website, and must say that it's pretty cool. <img src="/images/icons/cool.gif" /><br />Your knowledge on String Theory and Quantum Mechanics will be much appreciated. <img src="/images/icons/smile.gif" /> <br />But, beware, you will have to grow, or develope a thick skin around here. <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>