Scientific theories are not “guesses” but are logi­cally rigorous attempts to explain the observed facts of nature and to predict the results of new observations.

When a theory’s predictions are confirmed, it becomes an essential tool in the further practice of science, but even good theories may someday be superseded by theories more comprehensive or more accurate.

The universe is vast and old, with our sun one of bil­lions of stars in a local galaxy, joined by billions of similar galaxies occupying the depths of space beyond.

Life has changed over the eons, with complex creatures evolving from simpler precursors, and human beings therefore occupy one branch of an immense fam­ily tree of living organisms — all sharing a common molecular machinery driving basic life processes.

As Einstein demonstrated, conceptions of time and space based on everyday life don’t apply accurately to all speeds and all realms of space.

The microworld of the atom, and realms even smaller, obey “quantum” laws completely at odds with common sense, and notions of cause and effect and the very nature of reality are inherently blurred on that scale.

The way a thing works is often influenced by its connections to other things and the ways that they work, a principle that applies to everything from the networks of cells in the brain and the body’s other organs, to ecological and economic systems, to human interactions and social institutions.

Little is certain in science but much is highly probable, and the proper quantification of probabilities is essential for inferring facts, drawing conclusions and formulating sound judgments.

There is more to the world than we have dreamed of in our philosophies. There is more to be discovered, and principles today unknown will someday yield their secrets to continued inquiry, if the culture of the future remains educated enough to permit science to survive.