# Thread: Space time around the Earth spin?

1. There are a few article tell about Nasa experiments prove that space time around the earth is spinning. Is this true?If so why is it spin?

2. It is called "frame dragging" and it is an effect predicted to occur near rotating masses according to General Relativity.

3. It's true, they tested it

4. Wiki does not do justice to what a great experiment this was. I recommend checking out utube.

5. space sticks to matter?why?

6. Originally Posted by MaxPayne
space sticks to matter?why?
Masses will not only "curve" the structure of space-time around them, but also they will "twist" local space-time if the mass is rotating. Why? Who knows!

7. Originally Posted by MaxPayne
space sticks to matter?
No. Where did you get that idea from?

8. The way I think of it is to consider firstly a person standing on a non-rotating planet, then a person standing on a similar rotating planet. To both of these people, the energy-momentum tensor that is the source term of the Einstein equation will be to a reasonable approximation the same. In particular, both people can regard the energy-momentum as purely temporal. Therefore, the deformation of the otherwise flat spacetime produced by the energy-momentum source will be more-or-less the same. Here, I'm applying the principle of general relativity. In the respective coordinate systems, the Einstein equation is the same (the same source term) and therefore have the same general solution. But the otherwise flat spacetime being deformed is different in the two cases. For the non-rotating planet, the otherwise flat spacetime is non-rotating, whereas for the rotating planet, it is rotating. In the non-rotating case, the exterior solution is the Schwarzschild metric, with the deformation from the Minkowskian metric being non-rotating in form. The same deformation applies to the rotating flat spacetime and has the effect of lessening the rotation of the surrounding spacetime, this effect decreasing with distance just as the gravitation decreases with distance. When this is considered in the inertial frame of reference in which the planet is rotating, the surrounding spacetime rotates with the rotation of the planet.

This can also be viewed as an example of Mach's principle where in the frame of reference of the rotating planet, the planet is not rotating and the planet imposes some of this non-rotating character onto the surrounding spacetime. But further from the planet, this effect diminishes and the rotation of the flat spacetime increasingly dominates. In the frame of reference of the non-rotating distant spacetime, the spacetime surrounding the rotating planet has some of the rotation of the planet.

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