My Gran'dad

Would you like to hear a story about my gran'dad? Listen carefully. There's a prize for the best answer.

My gran'dad was fishing in Lake Superior one hundred years ago. In a rowboat. It was a hot sunny day. Rowing is hard work. When you do hard work on a hot, sunny day you...sweat.

Can anyone tell me what is in sweat? Right! Water and ...salt.

Can anyone tell me the technical name of table salt? Right! Sodium chloride – the same salt that occurs in natural waters.

Scientists use salt to study the movements of water in lakes and oceans. You can't tell where the water has come from or where it is going to by looking at water. But, you can tell by measuring the concentrations of salt in water – the movement always goes from high concentrations to low concentrations.

Listen carefully. I have a prize for the person with the best answer. Gran'dad jumped into Lake Superior to cool off, and the salt from the sweat on his back was evenly distributed throughout Lake Superior. Here is the question:

How long do you think it would take Lake Superior, through its outlet, to get rid of 90% of the salt from the sweat off my gran'dad's back?

Raise your hand if you want to answer. Only the answers that I repeat will count.

One hour. Two hours. One second. A day. Twenty days. One year. One hundred years. A month. And the last one: Never!

Would the person who said one hundred years come here? What is your name? José? Here is your prize, José: a Johnny Biosphere punch ball balloon. After you blow it up, do not tie it. Fold the mouth piece over like this, then push it into the balloon. If you want to take the balloon on your next trip to Australia, just pull out the mouth piece, deflate the balloon, and put it in your pocket. Blow it up when you arrive.

Before I give the balloon to José, let me tell you the right answer: It takes Lake Superior 500 years to get rid of 90% of the salt off my gran'dad's back!

Rivers flush themselves out in weeks or months, but large lakes take decades to centuries. For that reason you must be very careful what you put into large lakes, or into rivers that flow into large lakes.

Has anyone here ever been to Toronto? Toronto is located on Lake Ontario, downstream from Lake Superior. If you are ever there and have a glass of frozen orange juice or a cup of coffee for breakfast, think of my gran'dad will you? Because you will have swallowed at least one, and maybe a thousand salt ions from the sweat of his back!

Don't say "yuck!" That's ecology! One day a salt ion may be in a river, the next day in a willow tree, and the day after that in your body. That's nature's way of reusing and recycling things. Rain dissolves salt from rocks. Rivers carry the salt to the oceans. That's why the oceans are salty.

Did you know that our blood contains 0.9% of salt? Some people think that may reflect our evolutionary origin from fish in an ancient ocean.