adam_rockstar Posted May 18, 2006 Report Share Posted May 18, 2006 :eek_big: Quote Link to comment Share on other sites More sharing options...
Jay-qu Posted May 18, 2006 Report Share Posted May 18, 2006 3 spacial and we consider time to be one so there is 4, thats all we can really see and test, but new theories like super string theory require there to be more than this. Different versions of these theories bring up a different number of dimensions some have 10 and others have even more. Quote Link to comment Share on other sites More sharing options...
adam_rockstar Posted May 18, 2006 Author Report Share Posted May 18, 2006 so there can be more... in the crazy universe we live in, but it just depends on what theories you're comparing it to and the technology and knowledge we have available to us... right? Quote Link to comment Share on other sites More sharing options...
Tormod Posted May 18, 2006 Report Share Posted May 18, 2006 so there can be more... in the crazy universe we live in, but it just depends on what theories you're comparing it to and the technology and knowledge we have available to us... right? The theories do not create dimensions, they predict them. Whether they actually exist or not in a physical sense is something else entirely. Quote Link to comment Share on other sites More sharing options...
GAHD Posted May 18, 2006 Report Share Posted May 18, 2006 Point to Tormod. For the record I do *not* agree with time being considered a dimension any more so than considering gravity one. Quote Link to comment Share on other sites More sharing options...
Bo Posted May 18, 2006 Report Share Posted May 18, 2006 It all depends on what you mean by dimension. In principle the most consistent defintion for dimension is 'degree of freedom' So the number of dimensions of my problem is the number of things I can change. In this case a simple freely moving particle should not be considered to move in 3 dimensions (+time), but in 6 (+time). The reason is that the particle not only has a positionvector (3 dimensions), but also a velocity vector (also 3). If I want to I can add all kinds of other dimensions (e.g. a variable mass to effectively make gravity a dimension as GAHD wants it)With this definition of dimension the number of dimensions is unspecified. It just depends on what degrees of freedom you take into acount. If you talk however about spatial dimensions; our common sense tells us there are 3 of them (left/righ, up/down, forward/backward). (and indeed string theory predicts more). However relativity tells us that space and time are actually the same kind of things and space and time degrees of freedom get mixed depending on 'how you look at them'. Therefore it makes sense to talk not about spatial dimensions, but about the total of spacetime dimensions. (3+1 in our world) Bo GAHD 1 Quote Link to comment Share on other sites More sharing options...
Farsight Posted May 18, 2006 Report Share Posted May 18, 2006 How many dimensions are there in the Universe? Hard to say for sure. But IMHO more than three. You can tell because of gravity. It's a "force", but there's no maelstrom of whizzo magic messenger particles zigging between you and the ground making you fall down. Or making the moon go round in circles around the earth. What gravity is, is a distortion of the three regular dimensions, in some other dimension that you don't otherwise notice. The analogy is a bowling ball weighing down a rubber sheet. If you flick a marble at it, it rolls around the depression, in an orbit like the moon's orbit round the earth. The thing is, you're part of the rubber sheet along with all your rulers and light beams, which is why you don't notice the distortion directly. http://en.wikipedia.org/wiki/Curved_spacetime There are of course, other forces. Quote Link to comment Share on other sites More sharing options...
ronthepon Posted May 18, 2006 Report Share Posted May 18, 2006 What Bo said struck my thinking. Hey, dimension could be well defined as degree of freedom! Then we get many different types of dimension systems, though. Take: Observer frame D.S.D1- left-rightD2- front-backD3- up-down Take: World space D.S., cartesian styleD1- +ve x axis, -ve x axisD2- +ve y axis, -ve y axisD3- +ve z axis, -ve z axis Take: World space D.S., Polar styleD1- Dist from originD2, D3, D4: Angles with axes Finally if we get some sort of a degree of freedom in time, +ve time, -ve time etc. How's that for a flash insight? Quote Link to comment Share on other sites More sharing options...
Bo Posted May 18, 2006 Report Share Posted May 18, 2006 How many dimensions are there in the Universe?What gravity is, is a distortion of the three regular dimensions, in some other dimension that you don't otherwise notice. The analogy is a bowling ball weighing down a rubber sheet. You do something very dangerous here; namely taking an analogy literally. The bowling ball picture is something we can understand and therefore it is insightfull; However you should keep in mind that it is not what realy happens. space gets curved; but not 'in a certain direction' as is the case with the bowling ball. Curved space realy means that straight lines are not straight anymore (as compared to the 'flat' space case); that a unit length is not the same everywhere; that the angles of a triangle don't add up to 180 degrees; etc. Bo Quote Link to comment Share on other sites More sharing options...
InfiniteNow Posted May 18, 2006 Report Share Posted May 18, 2006 You do something very dangerous here; namely taking an analogy literally. All too common are dementians... :) Quote Link to comment Share on other sites More sharing options...
Tormod Posted May 18, 2006 Report Share Posted May 18, 2006 The bowling ball picture is something we can understand and therefore it is insightfull; However you should keep in mind that it is not what realy happens. space gets curved; but not 'in a certain direction' as is the case with the bowling ball. Well put, Bo! The question I sometimes ask people who wonder about this is "Into what does the gravity well extend". :) Quote Link to comment Share on other sites More sharing options...
Eclogite Posted May 18, 2006 Report Share Posted May 18, 2006 It has been suggested that we may live in a Universe consisting of only two spatial and one temporal dimensions. The illusion of the third spatial dimension is a consequence of the Universe's holographic character. I suspect a Google search for holographic Universe would turn up some interesting links on the topic. Quote Link to comment Share on other sites More sharing options...
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