• Question: Can according to general relativity space and time exist independently.why or why not?please explain in detail.And why TIME has a geometry?

    Asked by shobhit to Chris, Dave, David, Fiona, Jack on 22 Jun 2013.
    • Photo: David Freeborn

      David Freeborn answered on 22 Jun 2013:

      Hi shobhit,

      In relativity, space and time are both dimensions. So instead of 3 dimensions of space moving through time, we have 4 dimensions: 3 dimensions of time and 1 dimension of time. Time behaves exactly like another dimension of space.

      So, in principle, yes, space and time can behave independently. Space and time are a bit like the “stage” on which physics events happen. But in general relativity, physics also affects the stage: mass will stretch and warp it through gravity.

      Time has a geometry, because all dimensions have a geometry. Each dimension is like a piece of string. You could lay the string out straight, and this would be a flat geometry. Or you can curve it back on itself, and it will have a curved geometry. When you have 4 dimensions, there’s a lot of room for a really complex geometry.

      We think the Universe is curved, a bit like a “donut” shape. But every object with a mass slightly bends the space and time around it too. That means time seems to slow down around heavy objects, and other objects are drawn towards them: this is Gravity.

      I hope that’s slightly clear! These are really difficult concepts to understand, and really tough to explain too!

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