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When Seth Lloyd first presented his idea of a quantum time loop, he did not consider all the consequences. First, I didn’t expect to receive countless emails from would-be time travelers asking for help. If he could start time over again, he jokes, “I probably wouldn’t have done it again.”
Sadly, Lloyd, a physicist at the Massachusetts Institute of Technology, has no intention of revisiting the years gone by. Spoiler alert: No one goes back in time during this article. But what about particles? That’s another issue.
A theoretical route into the past called a time loop has long been hypothesized by physicists. But they have been dismissed as impossible for just as long, as they are plagued by impracticality and contradictions. But now Lloyd and other physicists are beginning to show that in the quantum realm, these loops into the past are not only possible, but experimentally feasible. In other words, we’ll soon be effectively sending particles back in time.
If successful, it increases the possibility that we will be able to send messages back in time, if not to humans, then at least in the form of quantum signals. More importantly, studying this phenomenon will help us learn more about how cause and effect actually work, what quantum theory means, and perhaps create successor theories that more fully capture the essence of reality. Even the way we do things brings us to the center.
In physics, time loops are more accurately known as closed time-like curves (CTCs). They first arose in Albert Einstein’s theory of general relativity…
