qwerty Posted May 3, 2005 Share Posted May 3, 2005 I think i remember a while ago reading or someone telling me that the edge of the universe is only as big as where all the expanding mass has reached. When the big bang happened (if it did happen) then wouldn't the edge of the universe not be where the mass has reached, but be further, because the light (which would be travelling faster then the mass from the big bang, because nothing travels at light speed or faster) would have reached further than the mass which was exploded from the big bang. any ideas on this? Link to comment Share on other sites More sharing options...
Spyman Posted May 3, 2005 Share Posted May 3, 2005 Well, first You must decide which shape the Universe has, number of dimensions and so on. (There seems to be a lot of theories about this but no prof.) And if I am not totaly wrong then the most common, (Big Bang), is that Universe has a shape without edge. (Bent in another dimension like a balloon, whatever direction You go, You will end up where You start.) If You decide to belive in a theory where Universe has an edge, then You must decide what an edge consist of, where to draw the line, whats inside and whats outside. In this case You can have several edges, how far we can travel, how far we can look, edge of stars, edge of life, edge of matter, edge of light or edge of gravity and several others. Link to comment Share on other sites More sharing options...
luc Posted May 10, 2005 Share Posted May 10, 2005 In General relativity, I don't know of any model in which the Universe has an edge Actually, the most popular model is the Concordance model, an Universe flat and with infinite volume, so there's no edge. There're other possibilities though, for example that the Universe could have the topology of a hypertorus, but in this case there's no edge either In fact, for a flat universe, that is curvature k=0, there are 18 possible topologies, one of them is the infinite case, other the hypertorus, and 16 more. I don't have the complete list of the 18 topologies, but according to this page http://www.williams.edu/go/sciencecenter/center/RS01html/RepSci2001-ASTRONOM.html a woman called Joey Shapiro made a thesis classifying these 18 topologies. I'd be very grateful to anybody that can provide me that thesis Link to comment Share on other sites More sharing options...
CanadaAotS Posted May 10, 2005 Share Posted May 10, 2005 Actually there's a theory that the universe was expanding faster then the speed of light at the big bang, the inflation theory. Link to comment Share on other sites More sharing options...
BlackHole Posted May 10, 2005 Share Posted May 10, 2005 Actually there is a cosmological constant or vacuum energy which is controlling the dynamics of the universe. We don't know why the universe is accelerating, nor do we know exactly what happened during this period. Looks as if completely new physics will be required. Link to comment Share on other sites More sharing options...
luc Posted May 10, 2005 Share Posted May 10, 2005 Actually there's a theory that the universe was expanding faster[/i'] then the speed of light at the big bang, the inflation theory. Actually is also expanding faster than the speed of light. Any point behind our Hubble sphere is expanding faster than the speed of light Link to comment Share on other sites More sharing options...
Bettina Posted May 10, 2005 Share Posted May 10, 2005 Help me to understand this. If the universe was created from a big bang, how could it be other than spherical? I don't understand how it could be flat. Bettina Link to comment Share on other sites More sharing options...
luc Posted May 10, 2005 Share Posted May 10, 2005 Help me to understand this. If the universe was created from a big bang' date=' how could it be other than spherical? I don't understand how it could be flat. Bettina[/quote'] if the universe has an infinite volume, then it started with an infinite volume, so it can't be an sphere, because has always been infinite, and always will be Bettina, you may want to take a look to this paper. It gives a review of ten of the 18 possible topologies that our universe can have http://www.dushkin.com/text-data/articles/31943/body.pdf "The shape of the universe: Ten possibilities" Link to comment Share on other sites More sharing options...
Johnny5 Posted May 10, 2005 Share Posted May 10, 2005 if the universe has an infinite volume' date=' then it started with an infinite volume, so it can't be an sphere, because has always been infinite, and always will be Bettina, you may want to take a look to this paper. It gives a review of ten of the 18 possible topologies that our universe can have http://www.dushkin.com/text-data/articles/31943/body.pdf "The shape of the universe: Ten possibilities"[/quote'] There is only one possibility, and it is the actuality. It is not the case that there are multiple possibilities here. Space is three dimensional Euclidean. It is mathematically necessary. Regards PS: When you use the term 'shape', in the context of the question, "What is the shape of the universe?" do you mean the structure of space, or do you mean something else? Link to comment Share on other sites More sharing options...
luc Posted May 10, 2005 Share Posted May 10, 2005 There is only one possibility' date=' and it is the actuality. It is not the case that there are multiple possibilities here. Space is three dimensional Euclidean. It is mathematically necessary. Regards PS: When you use the term 'shape', in the context of the question, "What is the shape of the universe?" do you mean the structure of space, or do you mean something else?[/quote'] Johnny I agree that space is Euclidean, but an Euclidean 3-manifold can have 18 different topologies, please read the paper Link to comment Share on other sites More sharing options...
Johnny5 Posted May 10, 2005 Share Posted May 10, 2005 Johnny I agree that space is Euclidean, but an Euclidean 3-manifold can have 18 different topologies, please read the paper I have to be honest with you... the pictures were cool but they prove space is simple 3-D Euclidean. Just look at the ones with the straight lines going off into the distance. The lines are straight. I have no idea what even one of the 18 "topologies" is after looking. Well basically because I was only looking to find an error as fast as possible. What in the heck was I supposed to see? Link to comment Share on other sites More sharing options...
Bettina Posted May 10, 2005 Share Posted May 10, 2005 I read it....and the answer is.....they don't know yet. Bettina Link to comment Share on other sites More sharing options...
Bettina Posted May 10, 2005 Share Posted May 10, 2005 I looked here too and they claim the universe is flat. So, can it still be spherical but so large that it looks flat? I'm just having a hard time imagining an explosion of space not being spherical in shape at the beginning. http://map.gsfc.nasa.gov/m_uni/uni_101shape.html Bettina Link to comment Share on other sites More sharing options...
Johnny5 Posted May 10, 2005 Share Posted May 10, 2005 Somewhere in the universe is the center of mass of the universe, it is a place it is somewhere you can go there and move your head around and look in any direction. You can set up a three dimensional rectangular coordinate system with its origin at that place, and you can use that reference frame to define the position of every single object in the universe. Since you dont need to do anything else to discuss the positions of things, you can use the simple Geometry used by Euclid to understand motion. I see no point in trying to curve space, and study manifolds and what not. Link to comment Share on other sites More sharing options...
J.C.MacSwell Posted May 11, 2005 Share Posted May 11, 2005 Somewhere in the universe is the center of mass of the universe' date=' it is a place it is somewhere you can go there and move your head around and look in any direction. You can set up a three dimensional rectangular coordinate system with its origin at that place, and you can use that reference frame to define the position of every single object in the universe. Since you dont need to do anything else to discuss the positions of things, you can use the simple Geometry used by Euclid to understand motion. I see no point in trying to curve space, and study manifolds and what not.[/quote'] There is nothing wrong with that. You can live your life quite happily that way. Science isn't everything. Link to comment Share on other sites More sharing options...
Johnny5 Posted May 11, 2005 Share Posted May 11, 2005 There is nothing wrong with that. You can live your life quite happily that way. Science isn't everything. If someone could show me a solid reason to study manifolds, I would pick it up as fast as I could. But really, I would rather study Lagrangian dynamics first, and everytime I start to read about it, it's worse than having a tooth pulled. Link to comment Share on other sites More sharing options...
BlackHole Posted May 11, 2005 Share Posted May 11, 2005 Nambu dynamics is an active area. All one needs is a course on abstract algebra, real & functional analysis and differential geometry (Michael Spivak is the best in this field). Link to comment Share on other sites More sharing options...
nomadd22 Posted May 12, 2005 Share Posted May 12, 2005 The big bang didn't throw matter out into the universe. It expanded the universe. Far off galaxy's aren't receding because they were accelerated by an explosion. They're receding because the space in between is expanding. One of the concepts that's hard to grasp is that not having a boundry doesn't mean that space is infinite. And the term "flat" doesn't mean the universe is shapped like a pizza. It just means that it's geometry does't change much. Last of all, don't try to simulate intelligence by using big words you don't understand. Link to comment Share on other sites More sharing options...
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