Why can you float in the Dead Sea?

In the Dead Sea, between Jordan and Israel, you cannot sink. People float on their backs reading newspapers.

The reason is salt. Ordinary seawater is about 3.5% salt; the Dead Sea is about 34% — almost ten times saltier. All that salt makes the water much denser, and denser water pushes up harder on anything in it.

The Dead Sea is so salty because it is a dead end. Rivers flow in, but nothing flows out. The desert sun evaporates the water and leaves the salt behind — the same process that makes all seas salty, turned up to maximum.

It is also the lowest place on dry land, more than 430 metres below sea level, and it is shrinking by about a metre a year as the rivers that feed it are used for farming.