# Why volume remains same under deformation?

I have done some problems in current electricity where you stretch or squeeze a wire, the length and area of cross section change but the volume remains same.

A question on math.stackexchange.com tries to answer it mathematically( https://math.stackexchange.com/questions/1125781/does-the-volume-of-a-ball-remain-constant-under-deformation)

But why it is thee physical reason behind volume being unchanged and on what physical limits the stretching & squeezing (and other sort of deformation) will leave the volume unchanged?

P.S. As per Mike Dunlavey's comment I am not talking about incompressible objects.

• Ever heard of something being "incompressible"? – Mike Dunlavey Sep 17 '16 at 0:34
• Yes! But I am thinking about non-incompressible objects. And your comment does not answer my question. – Mockingbird Sep 17 '16 at 1:02
• If the object is compressible, the volume can change when deformed. – garyp Sep 17 '16 at 2:55
• Constancy of volume or its opposite, is an assumption you make, and which subsequently needs to be verified experimentally. – Deep Sep 17 '16 at 5:53