OK, Going Greenophiles, here’s an intriguing little puzzle I came across. It’s great for starting lively discussions at parties, particularly if you hang out with either engineers or dentists. Give this one a thought (via Skepticblog):

What would happen if you took a tube of toothpaste to the bottom of the sea, and then opened it?

The initial thought is that the toothpaste would squirt out. After all, the pressure at the bottom of the ocean is far greater that up here at (approximately) sea level. But! That would only happen if the pressure surrounding the tube were less than the pressure being exerted directly on the tube. The toothpaste would only rush from a high-pressure environment (the tube being compressed) to a low-pressure environment. Indeed, this is what happens if you are fastidious about your dental hygiene: when you squeeze the tube, you are creating a high-pressure environment inside the tube, but outside (your bathroom) is a much lower-pressure environment. Hence, the toothpaste comes out and you can brush your teeth, making your dentist very happy. At the bottom of the ocean, though, there is increased pressure on the tube, yes, but the outside pressure is exactly the same, so there is no reason why the toothpaste would go anywhere. And this is a good thing, because I would hate to see the world’s oceans contaminated by dollops and dollops of toothpaste, although having watched Shark Week recently, some specimens could do with better oral hygiene.