What do We Know and How do We Know It

One of my favorite jobs was as a planetarium director. I got to meet a good fraction of the fifth graders, and smaller fractions of other ages of students from a major metropolitan area. The best part, for me, was the free form question period at the end when the students got to ask anything about astronomy or physics.

A fundamental test of your scientific mojo is to ask yourself, or have someone else ask you, what do you know and how do you know it. I few good ones at the very fundamental level:

1)Everything is made of atoms (Feynman's nomination for the most important scientific fact). How do we know?

2)Every living thing is made of cells (easy) and all those cells are built on extremely similar designs (harder) and all almost certainly derive from a common ancestor (hard).

3)The Sun is a star, and the other stars are very far away.

4)The Earth and the other planets orbit the Sun under the influence of gravity.(easy for physicists, I hope!)

5)The Americas used to be connected to Europe and Africa. India and Australia used to be near the South Pole.

6)Carbon usually forms covalent bonds with up to four other atoms. When it forms covalent bonds with four other atoms they wind up at the vertices of a tetrahedron centered on the carbon atom.

(7)Exp[i*theta] = cos(theta) + i* sin (theta)

More nominations welcomed, preferably not too esoteric.

Because I like this type of question, I always thought parenthood would be a perfect job in answering how and why questions. Unfortunately for this theory, my kids were so clever that they usually figured out nearly everything for themselves - at least that's the way the proud parent remembers it.