First published on the Steem blockchain by @remlaps on December 19, 2022. View the original post.
"Time travel offends our sense of cause and effect—but maybe the universe doesn’t insist on cause and effect." -[Edward M. Lerner](https://www.tor.com/2009/10/16/tropes-and-mundanity)
Introduction
Pixabay license from Genty at source. |
Today, Science Alert published the article A Physicist Came Up With Math That Shows 'Paradox-Free' Time Travel Is Plausible, which is an update of a 2020 article on the same topic. The article summarizes the 2020 paper, Reversible dynamics with closed time-like curves and freedom of choice by Germain Tobar and supervised by Fabio Costa. This is an Open Access paper (Creative Commons Attribution 4.0) in the journal, Classical and Quantum Gravity.
According to the paper, Einstein's theory of general relativity opened the door for the possibility of closed time-like curves (CTCs), which are paths through spacetime where an observer can interact with past or future versions of themself. In our intuition, however, this idea is challenged by the notion of the grandfather paradox.
The grandfather paradox is a potential logical problem that would arise if a person were to travel to a past time. The name comes from the idea that if a person travels to a time before their grandfather had children, and kills him, it would make their own birth impossible. So, if time travel is possible, it somehow must avoid such a contradiction.
Classical physics, and human intuition, both suggest that time moves in a single direction where past events determine the current state of the system, and where all parts of the system experience time in the same way. Relativity, however, argues that an event in a CTC can be in its own past and future.
