“California faults are a lot less likely to generate a tsunami.”Tsunamis are created by a particular kind of earthquake common off Japan and South Asia. They are generated when one side of a fault fracturing the ocean floor shifts violently beneath the other, which displaces huge amounts of water. Continue reading
It’s traditional to teach kids subtraction right after addition. That makes sense — the same facts about numbers get used in both, though in reverse. And the black art of “borrowing,” so crucial to successful subtraction, is only a little more baroque than that of “carrying,” its counterpart for addition. If you can cope with calculating 23 + 9, you’ll be ready for 23 – 9 soon enough.
At a deeper level, however, subtraction raises a much more disturbing issue, one that never arises with addition. Subtraction can generate negative numbers