Some black holes erase your past

[Judi Lynn]

February 21, 2018 by Robert Sanders, University of California - Berkeley


In the real world, your past uniquely determines your future. If a physicist knows how the universe starts out, she can calculate its future for all time and all space.

But a UC Berkeley mathematician has found some types of black holes in which this law breaks down. If someone were to venture into one of these relatively benign black holes, they could survive, but their past would be obliterated and they could have an infinite number of possible futures.

Such claims have been made in the past, and physicists have invoked "strong cosmic censorship" to explain it away. That is, something catastrophic – typically a horrible death – would prevent observers from actually entering a region of spacetime where their future was not uniquely determined. This principle, first proposed 40 years ago by physicist Roger Penrose, keeps sacrosanct an idea – determinism – key to any physical theory. That is, given the past and present, the physical laws of the universe do not allow more than one possible future.

But, says UC Berkeley postdoctoral fellow Peter Hintz, mathematical calculations show that for some specific types of black holes in a universe like ours, which is expanding at an accelerating rate, it is possible to survive the passage from a deterministic world into a non-deterministic black hole.

Read more at: https://phys.org/news/2018-02-black-holes-erase.html#jCp

[WhiteTara]

1. It remnds me of that tv show

Quantum Leap. He's jerked from one reality to the next with no explanation of past present or future.

[Anon-C]

2. ...

"There are some exact solutions of Einstein's equations that are perfectly smooth, with no kinks, no tidal forces going to infinity, where everything is perfectly well behaved up to this Cauchy horizon and beyond," he said, noting that the passage through the horizon would be painful but brief. "

[Binkie The Clown]

3. CLASSICAL physics is deterministic. Quantum physics is not.

The future is not determined by the past according to the quantum view. But then cosmologists tend to ignore the quantum level because it's "too small to matter" on an inter-galactic scale.

The argument goes:

Adequate determinism is the idea that quantum indeterminacy can be ignored for most macroscopic events. This is because of quantum decoherence. Random quantum events "average out" in the limit of large numbers of particles (where the laws of quantum mechanics asymptotically approach the laws of classical mechanics). Stephen Hawking explains a similar idea: he says that the microscopic world of quantum mechanics is one of determined probabilities. That is, quantum effects rarely alter the predictions of classical mechanics, which are quite accurate (albeit still not perfectly certain) at larger scales. Something as large as an animal cell, then, would be "adequately determined" (even in light of quantum indeterminacy).

Stephen Hawking in The Grand Design puts it:

"Quantum physics might seem to undermine the idea that nature is governed by laws, but that is not the case. Instead it leads us to accept a new form of determinism: Given the state of a system at some time, the laws of nature determine the probabilities of various futures and pasts rather than determining the future and past with certainty."

As attractive as such a simplification is to cosmologists, it's not strictly true. The universe is only approximately deterministic, or more correctly, statistically deterministic. In other words, stochastic.

[Ferrets are Cool]

4. Doesn't everyone have an infinite number of possible futures?

Or am I being too narrow minded?