# Template talk:Spacetime

WikiProject Physics (Rated Template-class)
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## Image

Two-dimensional analogy of spacetime distortion generated by the mass of an object. Matter changes the geometry of spacetime, this (curved) geometry being interpreted as gravity. White lines do not represent the curvature of space but instead represent the coordinate system imposed on the curved spacetime, which would be rectilinear in a flat spacetime.

The image seems to be an illustration of curved spacetime, and/or gravity potential, but why is the surface highest at a certain distance from the central mass? Does that make any sense? - Patrick (talk) 11:34, 28 April 2015 (UTC)

I replaced it, see also de:Diskussion:Beschleunigung/Archiv#Gravitationspotential: "not suitable to illustrate curved spacetime". - Patrick (talk) 07:56, 18 May 2015 (UTC)
Hi, Patrick – I've been a little busy and just noticed this change of image. The distortion is explained in the caption found in the Gravity article. It's true that the actual gravitational distortion is best depicted by a rectilinear grid such as the one in the image you used to replace this one; however, that distortion in this image is explained as the artist's conception of the x,y,z coordinate system that would be imposed on the curved spacetime, and not the actual curvature of space. Also keep in mind that these renditions are 2D representations of a 3D concept (nobody's figured out how to better represent such a complex 3D concept on a 2D medium). Yet another reason to favor this image is the fact that it also depicts Gravity Probe B within. So if you were looking for an opinion regarding the keeping of this image in this template, now you have it. In my opinion this image is far superior. – Paine  01:28, 24 May 2015 (UTC)
Changing from a polar to a rectilinear grid was not the point. My question is: why is the surface highest at a certain distance from the central mass (with the radial curves having an inflection point further out)? Does it have a physical meaning or did the artist draw this just arbitrarily because he thought it looked nice? Is it related to the rotation of the Earth?
The caption, including "which would be rectilinear in a flat spacetime" does not seem to make much sense. Both in a curved and in a flat 2D space one can use polar spacial coordinates.