How can one imagine space time curvature(q)
"Jack Partridge" <partridge@purple-pelmet.co.uk> wrote in message news:<kwCT9.14473$q67.3195@news-binary.blueyonder.co.uk>... > Hello there, > > New to this newsgroup. A bit surprised by all the animosity flying around in > all the posts. Hmm. > > Anyway, can anyone help me? I have been trying to work out whether > space-time curvature is absolute. It came up when reading the following in > Kip Thorne's book: > > "... if we move reltive to each other ... the density of mass that you > measure will be different from the density I measure, and the pressure of > matter we measure will differ. Similarly, it turns out, the sum of the three > curvatures of space-time that you measure will be different from the sum > that I measure. However, you and I must each find that the sum of the > curvatures we measure is proportional to the density of mass we measure plus > three times the pressure we measure. In this sense, the Einstein field > equation is the same in every reference frame; it obeys Einstein's principle > of relativity." > > I know that space-time is a mathematical construct, a way to represent the > manifold of events: dimensions to measure co-ordinates with, to define > positions with to test theories with. But many people talk about curvature > of space-time as if it was reality, i.e. as if it was what space is actually > like. > > Can anyone help?
Roughly speaking, if you assume that force of gravity is mediated by virtual gravitons, in a similar way the force of electromagnestism is carried.
In electromagnetism, the instensity of the field, at a given location, roughly correspondences to the number of the virtual particles that land at the location. More interestingly, the direction of electromagnetic force, correspondence to the direction in which the virtual particles will interact and deflect a charged particle.
Similarly, if you want to visualize curvature, you can start by looking at it, as roughly how the gravitons interact and tell bodies to move.
The curvature of space is an interesting concept. In SR, the space time continum
dr^2 = c^dt^2 - (dx^2 + dy^2 + dz^2)
is frame indepedent. The curvature of space roughly couples to this concept of space-time continum remaining constant in any frame.
Roughly, you can try to convince yourself as follow. Suppose, i gave u mallebale wire of fixed length. Now, you can twist and reshape the wire as much as you like. I can say that a fixed length of wire adjustes to the conditions, you subject it to, without losing its integrity.
You can imagine gravitional forces, as twisting and reshaping the above dr^2 containst in any frame.
-suresh > > Cheers, > > Jack.
To which the response is
Hi Jack Partridge again - I started this thread. Thanks to everyone who
> responded. > > Suresh Kumar: I like the idea of looking at the 'density of gravitons', but > gravitons are still hypothetical, and - correct me if I am wrong - are > force-mediators in quantum theory, which is at odds with GR. I think. True that gavitation has not been successfully quantized and that when one tries to quantize gravity, the peturbations are not renomalizable and the process introduces meaningless infinities that are really hard to get rid of. However, in fact, QED for EM waves is not mathematically correct, even though, it does produce observable results.
> I really like the idea of a malleable wire of fixed length representing the > invariant space-time vector, being twisted in curved space-time. But it > still leaves me wondering: 'if curvature is measured differently in > different frames, then space-time does not exist. It is merely a > mathematical way of representing the set of events in the Universe. > curvature is different from space time interval.
For example ds^2 = g_uv dx^a dx^b
the space time interval ds^2 stays same in any frame. However, curvature g_uv can be different.
Space-time is 'more real' of a concept than curvature. Almost any event in your life, has the space-time interval in any frame.
Btw, most of this, is beyond me. Dr. Steven Calip can explain even better than i can.
-suresh
Many people say that visualizing 4 dimensions is impossible. I disagree.
One simple way to vistualize the hypersphere of the univese is to realize that if you look far enough in any direction you are looking at the single point of the big bang. Thus the entires surface of the furthest sphere of space is a single point. If you contemplate this, you may be able to visualize a four dimentional hypersphere.
In QuantumEventTime the curvature is easily understandable. Space is much life a fluid composed of ZPE which is energy from the early universe now being received (annilated) by mass, and propogated into the distant future.
To understand space curvature this way is simple, the earth. at the surface is annilating 32 feet of time and space every second. Objects accelerate downward due to spacetime beneath them being lost to the distant future.
It is clear that gravity works like this and is not a force mediated by gravatrons or anything else. When you accelerate in a car you feel the acceleration. In a free fall (in a vacuum) you are weigthless and feel no forse of accelleration at all. It is as though you are staying still while the space beneath you is annhilated to nothingness.
This annilation of space is equivalent to the gravitational space curvature Einstein predicted. The resurection of the space in the distant future is responsible for the expanding universe.
Er... Pardon? You feel acceleration because of the resistance. In a car, you feel the acceleration of the car, as your body is resisting the acceleration of the car, as imparted to you via the car seat.
In free fall, you feel nothing because there is no resistance to your travel.
We feel gravity while standing on the surface of the earth as we are resisting travelling towards the 'gravitational center' of the earth at the speed of 32 feet per second.
It is an event that would happen regardless of HOW. It takes resistance to the movement to provide that feeling.
That is correct, sort of. Another point those who believe in strange forces at a distance can make is the all the atoms of your body are being accelerated together, so you don't feel it. I guess saying it is not a force because you don'r feel it is a little silly except that it may help some understand Einsteins interpretation of gravity as the shape of space it a world where gravitational acceleration is equivalent to inertial acceleration. The floor is accelerating you relentlessly upward toward the stars futiley, as though space flowing into the planet earth, which in effect is exactly the case.