what are blood grooves for?

[puukkoman]

Wow I sparked a little too much debate. I mean ice CAN be compressed. I know ice is less dense than water. When it freezes, it expands, thus giving it room to be compressed.

Nope, ice cannot be compressed, nor can water. Hydrostatic lockup in an engine is a good example of this truth. If you get water into your exhaust pipe, for example, and it gets into the cylinders, there can be no compression when the pistons move toward the head, which leads to blown gaskets and other expansion failures (cracked blocks, etc.).

 

[parbajtor]

Liquids can't compress so I doubt a solid can unless there are voids. Can a solid be compressed enough to change the crystal structure or arrangement of molecules? I guess that is what happens with diamonds but I don't think a mechanical process is going to make that change.

We see this "compression and expansion" all the time. It's the reason why clay-backed katana bend in the quench. The different atomic packing (body centred cubic) in Martensite causes it to expand relative to the austenite/pearlite in the spine which is face centred (and therefore packs more atoms into the lattice). Another example is memory metal where the metal "remembers" its original cold forged shape and returns to that shape if heated or in some cases an electric current is applied.