How much salt would I need to float in my bath?
Eureka! You can float in your bathtub by increasing the water's density. However, you're going to need an awful lot of salt.
Asked by: Richard O'Neill, Glasgow
As Archimedes showed over 2200 years ago, the trick lies in boosting the density of the bathwater until it exceeds that of your body. The easiest way to do that is to add salt to the water. But it requires a lot of the stuff: around 30kg in a standard bath-tub.