Suppose that you are standing on a pier at the edge of the Pacific Ocean. You have just created a new isotope of oxygen, ¹¹O. Somehow, despite the fact that ¹²O is comically unstable and has a half-life of 580 yoctoseconds, ¹¹O is stable. In your hand, you have a small glass of superlight water made with ¹¹O, so that every molecule in the glass contains the new isotope.

You pour the water into the world's ocean and go home. In your will, you leave instructions to be handed down through generations of your family: wait several millennia for the world's ocean to mix completely. Then go to that pier, or any pier, and take a glass of water from the sea. Then count the ¹¹O atoms in the glass.

What are the odds of getting one back?