# Gravity, relativity, spacetime.

Ok so there seems to be alot of posts about spacetime, dimensions gravity etc… May interest some of you to know that this is my area of research…

Anyway I don’t claim to know more than anyone about such matters but my i would like to share some of my interpretations on such matters. Actually the “spacetime distortions” post did make me look more into the theory of gravity and slightly change my views of space and time.

First I think its important to state that no one really understands time. But i think we do atleast no what time isn’t. Its not absolute; everyone measures there own time relative to everyone else according to a) there motion b) the gravitational field they experience. actually i would incourge anyone interested in such matters to read abert einsteins book on “relativity the special and general thoery”. Its aimed at the layman and he uses alot of useful imagery(trains etc.) There is also an appendix which was written in 1952 that deals with “the problem of space”. I found it very insightful.

I think personally that there is a big misunderstanding in general relativity that people think that the geometric interpretation (ie gravity curves space and time then matter follows these curves) is the fundemental action of gravity. Thats what i thought but i now think that to really understand both gravity and spacetime we should correctly assert that gravity acts on matter and as such objects move under its influence these effects then cause obervers to percieve space and time as curved( ie non-euclidean: the sum of angles in triangle will not equal 180).

The deeper insight given in the appendix is that empty space does not exist independently of the gravitional field. So really if there was no matter there would be no space. Maybe another may is to say that space is a property of matter and even then two dirfferent obervers will disagree on the geometry of space. The import thing is that the laws of physics should be the same indeppendent of the geometry of space(priciple of general covariance) otherwise the laws of physics would be different for two different obervers.

My research is concerned with quatum gravity. Put simply this means I must use the priciples of buth relativity and quantum mechanics to form a consistant theory of gravity. There are many candidate theories for QG: strings, loops, causal sets, etc.
My reasearch uses something called the Exact renormaliztion group. This idea states that at different length scales the effective laws of physics should take different forms because only quantum fluctuations(waves) with wave lengths less than the scale of observation should really contribute.

So for large scales all quantum effects will act. We observer that general relativity is an effective theory of gravity on all scales fom of a centimeter right up to galactic scales. But when the consider microscopic scales gravity should take a different form. This really means that as gravity defines space. space itself will have a different structure when we view it on very small scales( so far this structure is predicted to be a 2 dimensional fractal…though im far from understanding this yet). But this adds another twist, even the number of dimensions is dependent on the gravitational field!!!