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|Re: Will The Universe Expand For Ever???Why???
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Posted by dan/">dan on July 27, 1998 01:58:41 UTC
: : The Big Bang (BB) theory postulates an explosion of space (nothingness) itself, not an explosion of matter into space. In the latter case, it would be possible to analyse the motions of galaxies and determine where, in space, the explosion occured. In other words, it would be possible to find the center of the universe.
: : In the former case, there is a limited amount of space, but it is expanding. Inside the universe there is matter and there is space. Outside the universe there is... ( ? !! ? ).
: : Since we SEEM to be at the center of currently observed motion (the "velocity of recession interpretation" of observed redshift data), and since it's very unlikely that this is acutally the case, BB assumes that any obesrver anywhere in the universe would also see their location as the center of motion. (We have no choice but to ASSUME this until we can actually go somewhere else in the universe to see if it's really true. Stand by.)
: : According to most cosmologists today, the most likely explanation for all observers seeming to see their location as the center of motion is the expansion of space itself.
: : The usual analogy offered to help visualize this is to place several marks on the surface of a balloon. These marks represent stars or galaxies. As the balloon is inflated more and more, the skin of the balloon stretches and the marks get further and further appart. Note that the marks themselves also get larger as the various parts of each mark move away from each other. This analogy is not bad, depending on how well you can translate it in your head from two dimensions to three dimensions.
: : This expansion is counteracted by the attractive force of gravity. This force is assumed to have infinite range (stand by as above for confirmation), and the question of how long expansion will continue depends on the total mass of the universe. If that total is below a certain critical value, the universe will expand forever. If it is below the critical value, expansion will halt some day and then the universe will begin contracting (ultimately ending in a Big Crunch?). If it is exactly at the critical value, the universe expands more and more slowly, forever, getting so close to zero that we might not be able to measure the diffenerce, but never quite stops.
: : Current observations indicate that the total mass of the universe its less than 10 percent of the critical value. The universe will expand forever if this is correct.
: : And if the Big Bang is correct. And if gravity's range is really infinite.
: : Unless there is a significant amount of Dark Matter in the universe. But that is another story for another day.
: : Do you mean to tell me that our top scientists accept a theory (BB) that assumes matter came (exploded out of) from nothingness? Is this what the BB postulates? Then no wonder I could never understand it, who can? It makes NO SENSE! : You must be mistaken! All this time I thought they believed in a cyclic type of BB universe which makes more sense but is still impossible due to the amount of matter and the distance it is scattered though (infinite space)! : There is no center to nothingness, and the only markers we have are matter itself, so to say that there is a center is ridiculous! Red shift/blue shift whatever, and I don't mean to downplay the work of all the scientists, because it is important and I : revere them for thier contributions and dedication and calling, it is just the way I talk, many have told me I am abrasive in using others ideas..... : As far as explaining age, galaxies, black holes... are born, live, die all the time thoughout the sea of nothingness, some are probably 100 times the age of our own galaxy, but given universal time scales we see as humans only a billionth of a second out of (seemingly) eternity! Even geologic time is hard for us to comprehend, that is just a drop in the sea. : Dark matter, is that the stuff we have'nt figured yet? I think it is in some form of neutral energy partical spread throughout space which reacts in a static/friction way with matter as it moves though it.
: Billy (just an older college student, married, two young'ens, atheist, humanist, newby to science, to old really, but will get involved with classes, disscusions...)
: Can't respond very often, to many irons in the fire...
: :) Not very good on this dagblnged computer info hyway, can't even chat, I'm just to slow...
I read most of the responses to teng's question and was disappointed at how many of them were inaccurate conjecture. BILLY, you obviously don't have the SLIGHTEST bit of knowledge on this matter and shouldn't have attempted to answer the question. For example nothing is even CLOSE to 100x the age of our galaxy. The Universe is only about 15billion yrs.old and our sun is about 5 billion yrs old. I have studied this material, as it seems larry has, and can say that larry has pretty much hit the nail on the head. So teng, from now on i would suggest emailing an astronomer at a local college w/ your Qs b/c it seems that any moron can convince himself he knows what he's talking about and won't be afraid to spread his ignorance.
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