# Astronomy

By chengfoo1986

@chengfoo1986 (21)

Malaysia

3 responses

@nayanmange (148)

• India

21 Oct 07

Well, we have three spatial dimensions length, breadth, height. And one dimension of time. So in all there are four dimensions in our space-time co-ordinate system. But there are theories, like the string theory, m-theory, etc., which predict that there may be many more dimensions present which cannot be seen by the human eye.

@Stephen_Dedalus (3)

•

10 Jan 08

We've always been familiar with 3 dimensions of space and therefore movement. There's forward-backwards, side-to-side, up-down... any movement or force or direction or accelaration or anything that's a vector quantity... it can be resolved into 3 perpendicular dimensions... 3 figures and a magnitude... i, j and k... or x, y and z...
if you run at top speed forwards, all your motion is in this central dimension... but say instead of running at a bearing of 120 you ran at a bearing of 121... you'd be moving in your original dimension... yet not quite at full speed, because some of your full speed will be used in moving along an entirely different dimension...
spacetime came before einstein, but the idea of space and time being the 2-sides of the same cosmic coin is integral to understanding his work
einstein stipulated that the speed of light is the same for all observers, and this that in 4-dimensional space-time any movement in the space dimension detracts from your progress in your space dimension... and that we are all of us moving at the speed of light through 4-dimensional spacetime, and mostly through the time part... a photon emitted at the big-bang will have gone through no time whatsoever as it has always been moving through the spacial dimensions at the speed of light... therefore has had no movement through the temporal dimension...
but string theory includes extra dimensions... the idea that every fundamental particle is inherently just a string... what makes these things different you say? what makes an electron string different from an up quark string? Well.. according to string theory it has to do with the string's oscillatory (vibrational) properties... as though all the world's matter is as a set of tuned guitar strings... how do they vibrate this way? well this is where the extra dimensions come into play, string theory suggests that there are many extra curled up spatial dimensions that at the planck length (similar to the length of a string... this is important) and these are called calabi-yau spaces... at this small scale left right and up and down wouldn't mean nearly anything and all movement and space would be a very complicated array of curled up dimensions. These dimensions... rather like a woodwind instrument... have an effect on the vibrations of the strings... and should these extra-small dimentional calabi-yau spaces have slightly different properties... then the charge on an electron may be different... or the strength of the gravitational constant would change by a little or by a lot... or we may see completely different sets of matter... yeah groovy and mathematically abstract ain't it...