Dead Low Tide

Puzzler time. Here we go.

Imagine, if you will...

There is a yacht tied to a dock in a harbor at dead low tide.

So, the tide begins to come in at two thirds of a foot per hour. It is a steady rate. So if you were in the harbor and you were measuring the rate of the tide, after a half hour, it would have come in a third of a foot.

The porthole on the side of the yacht is 9 feet above the surface of the water.

How many minutes will it be before that distance is reduced from 9 feet to 7 and a half feet?

Good luck.

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Remember last week's puzzler?

Secret Discovery

Time for this week's puzzler.

Here it is. Very short, and very elegant.

During World War 2, the Japanese discovered a secret weapon, which they had hoped to use to their military advantage.

But it turns out, they did not. They did try, but it was not to their advantage.

And this discovery is something that is used by virtually every country in the world today, on a daily basis.

What was this discovery? And how was paper involved?