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Dec28-05, 04:55 PM
Sci Advisor
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Garth's Avatar
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Yes van gogh, a standard analogy of the gravitational field around the Sun, for example, is to consider a flat rubber sheet. Small balls would roll across it along straight lines, but if now a bowling ball is placed in the middle so that it makes a dip, then the small balls would be deflected towards the centre - the Sun - or they can even be made to 'orbit' around the circumference of the dip.

As an analogy this model can be very helpful but realise that it is only an analogy and breaks down in that it uses gravity twice, to keep the balls on the sheet whilst trying thereby to explain gravity! The real situation is to visualise the curvature of the rubber sheet intrinsically. The paths of the small balls are now straight lines across the curved surface of the sheet, their paths are bent, or even orbit in a closed ellipse, because the surface on which they are 'drawn' is curved.

This sheet represents curved space, in GR gravitation is properly described by the curvature of space-time. The time component is not 'curved' instead it is revealed as time dilation.

I hope this helps.