Kindle Notes & Highlights
Einstein’s equations portray everything in the block universe as decided from the beginning; the initial conditions of the cosmos determine what comes later, and surprises do not occur—they only seem to.
Gisin argues that time in general and the time we call the present are easily expressed in a century-old mathematical language called intuitionist mathematics, which rejects the existence of numbers with infinitely many digits.
If numbers are finite and limited in their precision, then nature itself is inherently imprecise, and thus unpredictable.
Gisin said it is important to formulate laws of physics that cast the future as open and the present as very real, because that is what we experience. “I am a physicist who has my feet on the ground,” he said. “Time passes; we all know that.”
It was on a Sunday about two and a half years ago that he realized that the deterministic picture of time in Einstein’s theory and the rest of “classical” physics implicitly assumes the existence of infinite information.
The universe’s initial conditions would, Gisin realized, require far too much information crammed into too little space.
But in Brouwer’s framework, statements about numbers might be neither true nor false at a given time, since the number’s exact value has not yet revealed itself.
Even though pi is irrational, with no finite decimal expansion, there is an algorithm for generating its decimal expansion, making pi just as determinate as a number like ½. But consider another number x that is in the ballpark of ½.
In other words, the world is indeterministic; the future is open. Time, Gisin said, “is not unfolding like a movie in the cinema. It is really a creative unfolding. The new digits really get created as time passes.”
“For Chrissakes, you have two uranium atoms: One of them decays after 500 years, and the other one decays after 1,000 years, and yet they’re completely identical in every way,” said Nima Arkani-Hamed, a physicist at the Institute for Advanced Study in Princeton, New Jersey. “In every meaningful sense, the universe is not deterministic.”
“Information is destroyed as you go forward in time; it’s not destroyed as you move through space,” Oppenheim said. The dimensions that make up Einstein’s block universe are very different from one another.
