Sunday, April 22, 2018

Some Thoughts on Space and Time

Image Not with the Original Text
I read these brief comments written by a comrade in response to a person who claimed proof of "god". I found it sort of interesting although I have to admit, I don't really understand it, but I know some will.  I'm also aware that with subjects such as these there will be some controversy and different opinions. I am not referring to controversy between religious doctrine (idealism) and science but within the scientific community itself. Anyway, read away.

On the matter of "God" and "creation" (I just posted elsewhere):

Dave Parks, Exeter UK

The Friedmann solution to the Einstein equations of General Relativity is something I studied in my 2nd year at University. For simplicity here I will describe the closed model solution - this is where there is enough matter in the universe for it to eventually collapse under it's own gravity. A bit like a rocket shot directly upwards but without enough speed to escape the effects of Earth's gravity - eventually it decelerates and falls back to Earth.

First thing this is a 4-D model. There are two assumptions the universe is homogeneous and isotropic. Basically made of the same stuff throughout and in a symmetric or equal way in all directions. Any localised clumping or asymmetry evens out on a grander scale. Evidence from microwave background radiation suggests this is a highly reasonable if not accurate assumption for the early universe.

It is almost impossible for us humans to visualise 4-D - so we use analogies. For the closed Friedmann model that analogy is the surface a 3D sphere representing the whole history and expanse of 4D space-time. The North pole of this sphere represents T=0 (the Big bang). Time (1D) is represented by longitude, 3D space is represented by latitude. At this point the radius of the universe is the extent of the latitude of the sphere at that point which is also zero. As longitude increases as you move away from the north pole the size of the universe increase until it reaches a maximum at the equator. From then on the universe stops expanding and starts contracting back down to zero size - a "big crunch".

All points in space and time throughout the entire history and expanse of the universe are represented on the surface of this 3D model. This is a finite and bounded model. There is no "edge" - if you could travel around it you would not fall off the edge. If you could somehow approach the north pole you would find the region "smooth" no edges or boundaries. To speak of a minus time here is meaningless. There is no minus time or time "before". This is to abstract "time " as a concept separate from relativistic space-time. It is hard to understand for those who have not studied the maths and physics of Riemann geometry - non-Euclidean geometry is the reality of the Universe we live in. Talk of creation and "gods" have to be understood in that context.

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