Why can't whales go on land?

The reason whales die rather quickly when they're stranded on a beach is two things. First, their bones are lightweight and porous, much lighter than the bones of land animals. this is because, in the water, the bones don't have to provide the kind of support that ours do on land, so they've evolved more as places for muscles to attach to than for actual support. On land (away from the buoyant water where gravity isn't a big factor), the whale literally crushes itself under its own weight. Second, they overheat. Most whales are designed to live in cold water, which takes heat out of a body some 20 times faster than air does. Their fat (blubber) insulates them very well in the water. On land, however, they dont have the cooling of the water, and the blubber makes them overheat. Dead whales literally cook inside, since after death the thermoregulatory mechanisms that normally cool the animal are shut down, and decomposition sets in, inside what is essentially a big pressure cooker (the body).