Why time travel is less implausible than you might think

Could time travel be possible? This question has been studied not only in science-fiction literature but also in theoretical works following Einstein’s discoveries. So far the answer has been that in order to time travel we must abandon logical consistency or face dramatic philosophical consequences. However, it now seems that this answer should be reconsidered.

By Ämin Baumeler

We, as humans, strive to understand what happens around us with one basic idea in mind: one event causes another event. Through the unfolding of cause and effect relationships, we perceive a chain of events.

Einstein’s theory of general relativity challenges this view. According to the theory, parts of the chain can be looped around. A loop in cause and effect relationships means that some “later” event is also the cause of an “earlier” event, with the result that the terms “later” and “earlier” stop making sense, and that time travel into the past becomes possible. “This contradicts my feeling for physics in the most vivid sense”, Einstein once commented.

Time travel is problematic in various ways. To illustrate a problem of a logical nature: imagine that you board a time machine, travel to the past, and destroy said time machine. This means that you will not be able to use the machine (since you destroyed it). Yet, if you do not use the machine, then you will not destroy it either, so you will use it after all.

Time traveler standing in front of a portal
A fascinating springboard for science fiction: time travel has been a popular and recurrent theme in literature and film for many years © mikkelwilliam/Getty Images

This and similar problems have been resolved by describing time travel quantum mechanically. These quantum-mechanical descriptions, however, remain unsatisfactory; they provide shortcuts to solve hard mathematical problems believed to be practically unsolvable. For that reason, again, time travel has traditionally been considered to be impossible.

Recently, however, researchers from the Institute for Quantum Optics and Quantum Information in Vienna described a new model for time travel in the journal it – Information Technology. They claim that their model complies with the fundamental requirements of logic, physics, and computer science, whilst making common objections against time travel, like those mentioned above, obsolete.

According to the researchers, time travel can no longer be ruled out based on current arguments. Furthermore, as the article notes, while time travel is just an “application” of the research program on causality, “causal loops might be considered as theoretical building blocks for approaching problems in physics, computer science and possibly other fields.”

Read the original article here:
Ämin Baumeler: Causal loops: Logically consistent correlations, time travel, and computation, 06.02.2019.

The Editors

Articles signed by the editors were written in a collective effort.

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