The Fabric of the Cosmos: Space, Time, and the Texture of Reality

by Brian Greene

We choose hard data and the framework of mathematics as our guides, not unrestrained imagination or unrelenting skepticism, and seek the simplest yet most wide-reaching theories capable of explaining and predicting the outcome of today’s and future experiments.

These early pioneers of modern scientific thought argued that, when looked at the right way, the happenings in the universe not only are explicable but predictable. The power of science to foretell aspects of the future—consistently and quantitatively—had been revealed.

“Make everything as simple as possible, but no simpler.”

It’s not that the electron has a position and that we don’t know the position before we do our measurement. Rather, contrary to what you’d expect, the electron simply does not have a definite position before the measurement is taken.

Human language is far better at capturing human experience than at expressing deep physical laws.

The future is indeed the direction of increasing entropy. The arrow of time—the fact that things start like this and end like that but never start like that and end like this—began its flight in the highly ordered, low-entropy state of the universe at its inception.18

Quantum mechanics is starkly efficient: it explains what you see but prevents you from seeing the explanation.

Your new observation singles out those histories that could have preceded whatever your new observation revealed. And since this observation determined which path the photon took, we consider only those histories that traverse this path, thus eliminating the possibility of interference.

Einstein showed that nothing can move through space faster than light. But galaxies, on average, hardly move through space at all. Their motion is due almost completely to the stretching of space itself. And Einstein’s theory does not prohibit space from expanding in a way that drives two points—two galaxies—away from each other at greater than light speed. His results only constrain speeds for which motion from spatial expansion has been subtracted out, motion in excess of that arising from spatial expansion.

Special relativity has the constancy of the speed of light. General relativity has the equivalence principle. Quantum mechanics has the uncertainty principle. String theorists continue to grope for an analogous principle that would capture the theory’s essence as completely.