One story in particular seems to have grabbed people's attention this past week, and my email inbox was stuffed with versions of it, so thanks to all of you who sent it.
Remember the 1980s movie Back to the Future with Christopher Lloyd and Michael J Fox, where Lloyd plays a somewhat nuts professor inventing a time machine from a converted DeLorean car, and Fox the guy who used it and traveled back in time to cause all sorts of paradoxes? Well, that can't happen, according to a new theory out there that is positing a rather interesting view of the universe that prevents that from happening:
Here's the way the second article puts it:
“On a quantum computer, there is no problem simulating opposite-in-time evolution, or simulating running a process backwards into the past,” says Nikolai Sinitsyn, co-author of the study. “So we can actually see what happens with a complex quantum world if we travel back in time, add small damage, and return. We found that our world survives, which means there’s no butterfly effect in quantum mechanics.”
Using an IBM-Q quantum processor, the team created a complex system using quantum gates and demonstrating cause and effect, running both forwards and backwards in time. The simulation involved two hypothetical people, Alice and Bob, who each have a qubit – a quantum bit of information.
In the scenario, Alice prepares her qubit in the present, then sends it backwards in time. At some point in the past, Bob interferes with the qubit by measuring it. Then, the system is run forwards again to the present time, and Alice checks her qubit.
What you think “should” happen next depends on which time travel rules you subscribe to. The butterfly effect says that because the qubit is tied to so many variables, Bob’s small interference should completely change the system by the time we get back to the future (or present, to Alice).
But the team found that that wasn’t the case. Alice’s qubit comes back relatively unscathed, and she can recover the information on it. Interestingly, the fact that it’s tied to so many variables seems to be what actually saves it from damage – the information in the present qubit was hidden in the quantum correlations in the deep past. This web of connections isn’t so easily disturbed by Bob’s amateur efforts at timeline vandalism. (Emphasis added)
And here's the way the first article puts it:
A variation is known as the "grandfather paradox" — in which a time traveler kills their own grandfather, in the process preventing the time traveler's birth.
The logical paradox has given researchers a headache, in part because according to Einstein's theory of general relativity, "closed timelike curves" are possible, theoretically allowing an observer to travel back in time and interact with their past self — potentially endangering their own existence.
But these researchers say that such a paradox wouldn't necessarily exist, because events would adjust themselves.
In other words, a time traveler could make changes, but the original outcome would still find a way to happen — maybe not the same way it happened in the first timeline but close enough so that the time traveler would still exist and would still be motivated to go back in time.
"No matter what you did, the salient events would just recalibrate around you," Tobar said. (Emphasis added)
Or to put all that slightly differently (and relying on these articles without the benefit of the original papers): the universe has a built-in mechanism that seems to allow the possibility of time travel without apparently allowing major shifts in events (or does it? We'll get back to that.). That mechanism appears to view causality not in a linear fashion, but a planar one, as a "web of connections", not one line leading from cause A to effect B, but several possible lines connecting the two. One might even speak in terms of a kind of "temporal network mass"(for want of a better term); the more the connections, the great the "temporal network mass" and the more that is required to move - i.e., change - it. The event still happens, but the path is different, meaning that the history is different. In other words, small changes of history can result if the outcome remains the same.
Notably, in the experiments, the scientists were using quantum computers (!) to run their experiments, and the computers behaved in an oddly deterministic way, demonstrating this "temporal network mass". In other words, the effects were being run at quantum scales. But I raise the point about history (the path) being different because while the claim is made that there is a mechanism preventing all the nasty paradoxes, I think that they haven't been removed, but merely relocated. Suppose one found a way to calculate that "temporal network mass", say, by calculating the lines emerging from each node? (In fact, what we're suggesting is that the lattice of space-time might be a semi-regular tesselation, for those interested in the technical stuff.) But if that were the case, and assuming this type of paradox-free time travel were possible on the macro-scale as well as the quantum, how would one calculate, say, the "temporal network mass" of a Joseph Stalin, whose wretched existence affected human history and millions of lives? And could that be undone by a time-traveller? And if so, how?
One really (and I mean really extremely) high octane speculation emerges from the idea that the universe as a self-correcting mechanism in the form of that "web of connections", and that is that a "temporal network mass" could only be overcome by a correspondingly greater force, a force sufficient to move it. And part of that temporal network mass results precisely from its history, and the only way to overcome that is to overcome the particular memory of that particular historical path.
And that means the only was to test such an hypothesis, is to do it on a macro-scale.
OK. Now that I've once again run straight off the end of the speculation twig and crashed into the bottom of the speculation canyon like Wile E. Coyote, I'll stop there before I get myself into more trouble.
See you on the flip side...