g2006 Posted June 22, 2005 Share Posted June 22, 2005 Hi all Sorry if this is the wrong place to post this but could one of the mods just move it if it is....Thanks. Anyway i have done searches on singularities and i keep coming up with stuff explaining them but the words they use i cannot understand yet. So could any body please just give me an idea of what a singularitie is and any more info would be greatly appriciated. Link to comment Share on other sites More sharing options...
Spyman Posted June 22, 2005 Share Posted June 22, 2005 A singularity is a point without length, high and wide. Gravitational singularity: http://en.wikipedia.org/wiki/Gravitational_singularity Wikipedia is a good place where You can search for this cind of things. Link to comment Share on other sites More sharing options...
insane_alien Posted June 22, 2005 Share Posted June 22, 2005 do you mean singularities as in black holes or mathematical singularities. there is more than one type. Link to comment Share on other sites More sharing options...
ydoaPs Posted June 22, 2005 Share Posted June 22, 2005 if you would look to see what forum this thread is in, you would probably guess black hole. Link to comment Share on other sites More sharing options...
Nicholas Posted June 23, 2005 Share Posted June 23, 2005 A singularity could be space-time starting as a point. That is the Big Bang. It could also be infinite density of mass or a bunch of mass as a single dimensionless point. I believe that singularities are violations of physics. With the exception that if you run space-time backwards to a begining it has obviously expanded from a singularity. If the Big Bang was a mass singularity also its gravity would prevent any expansion. It would be a black hole. As Stephen Hawking has said about them: GR predicts its own downfall by predicting singularities. If there are no singularities then what replaces them? Finite or Maximum Mass Density does. In otherwords there will always be space inbetween matter particles. I believe this is the Pauli Exclusion Principle. Mitch -- Light Fallls -- Link to comment Share on other sites More sharing options...
luc Posted July 8, 2005 Share Posted July 8, 2005 The initial singularity of the Big Bang does not need to be a point. Link to comment Share on other sites More sharing options...
Nicholas Posted July 9, 2005 Share Posted July 9, 2005 Then it aint a singularity. Space-time goes back all the way to a point. And you can't say otherwise. Link to comment Share on other sites More sharing options...
alt_f13 Posted July 9, 2005 Share Posted July 9, 2005 Then it aint a singularity. Space-time goes back all the way to a point. And you can't say otherwise. One could. You can also say it does, but that doesn't make it true. We are not yet at a level where we can say with the greatest degree of certainty what happenned at the beginning, or even if there was one. We believe we might have a good idea. And just because space-time *may* have been a singularity, isn't to say a singularity is not possible in any other circumstance, regardless of what you believe. Link to comment Share on other sites More sharing options...
Nicholas Posted July 9, 2005 Share Posted July 9, 2005 If you can't see back to an original point of space. You are not going back far enough. Link to comment Share on other sites More sharing options...
luc Posted July 9, 2005 Share Posted July 9, 2005 Actually is thought that the Universe is flat and of infinite volume. How could then have emerged from a point? A point, in the finite time since the Big Bang, 13.7 billion years, couldn't have grown to an universe of infinite volume. Pure logic, people Link to comment Share on other sites More sharing options...
ydoaPs Posted July 9, 2005 Share Posted July 9, 2005 inflation Link to comment Share on other sites More sharing options...
luc Posted July 9, 2005 Share Posted July 9, 2005 inflation, what? Link to comment Share on other sites More sharing options...
ydoaPs Posted July 9, 2005 Share Posted July 9, 2005 http://en.wikipedia.org/wiki/Cosmic_inflation Link to comment Share on other sites More sharing options...
luc Posted July 9, 2005 Share Posted July 9, 2005 i know very well what's inflation. i don't know though how it permits that an Universe emerging from a point can have today infinite volume. Can you explain? Link to comment Share on other sites More sharing options...
ydoaPs Posted July 9, 2005 Share Posted July 9, 2005 how can 0 expand into any finite length? Link to comment Share on other sites More sharing options...
danny8522003 Posted July 10, 2005 Share Posted July 10, 2005 Ive read a lot about black holes and singularities both in books and on the net and there has always been one thing that puzzles me. If mass = density x volume and the density is said to be infiniate, then surely the mass is infinite unless the volume = 0. If it is 0 then the mass would be 0 and space-time would not be warped to form the blackhole. A factor i have thought of is that the singularity may not have any dimensions, if this is the case then it would exhibit 0 volume but again ow could it have mass? Also i wondered whether anyone has thought that maybe the hidden mass in the Universe known as dark matter maybe just a black hole or a series of them? Mainly because we can be unsure of how many of these holes exist and whether it is enough to prevet infinite expansion. Link to comment Share on other sites More sharing options...
luc Posted July 10, 2005 Share Posted July 10, 2005 how can 0 expand into any finite length? Imagine that you are in the origin of the real line. You can run either in the positive or negative direction, but you always will be over a real number, you can never achieve infinite, this is analogous to the volume of the Universe Link to comment Share on other sites More sharing options...
[Tycho?] Posted July 10, 2005 Share Posted July 10, 2005 It is not known if the universe is infinite in extent or not. Link to comment Share on other sites More sharing options...
Nicholas Posted July 10, 2005 Share Posted July 10, 2005 Universal expansion is proof the universe cannot be infinite. The universe had a begining a finite amount of time ago and is expanding at a finite rate. You can't get an infinite universe out of that! Only the future is infinite. Link to comment Share on other sites More sharing options...
Ophiolite Posted July 11, 2005 Share Posted July 11, 2005 Universal expansion is proof the universe cannot be infinite. No it isn't. For example [in simple terms] http://www.astronomycafe.net/qadir/ask/a11839.html Only the future is infinite.No. The future may be eternal. That is a different matter. Link to comment Share on other sites More sharing options...
BobbyJoeCool Posted July 13, 2005 Share Posted July 13, 2005 If mass = density x volume and the density is said to be infiniate, then surely the mass is infinite unless the volume = 0. If it is 0 then the mass would be 0 and space-time would not be warped to form the blackhole. d=m/v. for any finite amount of mass, in a point with no dimentions the volume is 0. Lets say that the mass is 1kg. so, d=1kg/0. 1/0 is undefined. so, we say it has an infinite density (mass with no volume). A factor i have thought of is that the singularity may not have any dimensions, if this is the case then it would exhibit 0 volume but again ow could it have mass? Take the mass in 10 supergiant stars. put them all together in the space of the planet Earth. the gravetational forces created by that much mass in such a little volume will force the mass to compress. It will draw in more mass with will force it to compress more until, in theory, it has compressed to a single point in space with no height, width, or length, but it still has mass, so it has an infinite density. Link to comment Share on other sites More sharing options...
BobbyJoeCool Posted July 13, 2005 Share Posted July 13, 2005 opps.. I just realize what you were doing... d=m/v, so m=dv. But when you put the numbers in... d=1/0... you're multiplying both sides by 0 (moving the v over with the d) 0*d=0(1/0) 0=0 Link to comment Share on other sites More sharing options...
danny8522003 Posted July 16, 2005 Share Posted July 16, 2005 But if m=dv then when trying to find m we get m=inf.*0. Anything multiplied by 0 is 0 so surely if the mass would be 0 when you do it backwards? So v must be >0 for the formula to work, but if it is >0 then we end up with infinite mass which im sure isnt allowed. Link to comment Share on other sites More sharing options...
BobbyJoeCool Posted July 17, 2005 Share Posted July 17, 2005 But if m=dv then when trying to find m we get m=inf.*0. Anything multiplied by 0 is 0 so surely if the mass would be 0 when you do it backwards? So v must be >0 for the formula to work' date=' but if it is >0 then we end up with infinite mass which im sure isnt allowed.[/quote'] In mathematics, you have to know what your doing... when you have a given equation, d=m/v for instance, and you're given all but one number to fill in the equation (in this case, density and volume), you cannot just move the equation around... Starting with the original equation... [math]d=m/v[/math] [math]d=\infty, v=0[/math] [math]\infty=\frac{m}{0}[/math] [math](0)\infty=(0)\frac{m}{0}[/math] [math]0=0[/math] d=m/v, so m=dv for v|v=/0 (as in when v does not equal 0). Because, as you see, in the original equation, when v=0, the equation is undefined. When you plug numbers into an equation, you have to check the original equation to make sure it's defined in the original equation. In this case, in the original equation, plugging 0 in for v makes it undefined therefore if d=m/v, m=dv is NOT TRUE at v=0. Link to comment Share on other sites More sharing options...
danny8522003 Posted July 17, 2005 Share Posted July 17, 2005 I think i understand now, thank you BobbyJoe . Link to comment Share on other sites More sharing options...
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