As we near the end of 2010, everybody’s talking about the biggest science stories of the year. I’ve been thinking about these four:

Each of these stories assumes a fairly robust understanding of what life is. If you make an artificial cell, you must know what a cell is. If you create a machine that screens for signs of life, you must know what signs of life are. Congress banned funding of human embryonic stem cells under the assumption that embryonic stem cells are forms of human life. The arsenic-loving bacteria (should they exist as described) upend the presumably solid notion that phosphorus is crucial for life.

Alas, we are far from defining, let along understanding, what life is. In a series of