Sometimes, you have to cheat a bit to get a theory to conform to reality as we currently understand it. We love to think of time travel and of warping space — and there are Big Thinkers who are bringing us closer to that total destiny today.
A Closed Timeline Curve (CTC) is the key to moving forward and backward in time. A CTC is like a stitch in time connecting one place with another.
A risk of time travel is the very one that plagued the fantasy travel show, Star Trek: How do we interact with the past without changing it? The greater writer Harlan Ellison addressed that very paradox in an episode he wrote for the series called, “The City on the Edge of Forever.”
In 1991, Oxford University’s David Deutsch found a way around the paradox of changing the future by interacting with the past by deciding a quantum particle traveling around a CTC is like a watchdog protector — always ready to reset the ready state to ready — and always guaranteeing that any interaction with the CTC provides the look and feel of a static, but changing, unchanged state — that would then not interfere with what has already happened.
Last year, Todd Brun and his associates at USC found a way to expand on the Deutsch ideas to decode quantum-encrypted messages:
Such a message could be sent sent as a series of particles, each in quantum state “zero,” quantum state “one,” or a combination state called a superposition. The intended recipient measures each particle but needs additional information after-the-fact from the sender to distinguish the superpositions from the non-superpositions. But a spy who could distinguish “on the fly” between, say, a zero and a superposition state could intercept the message and also send particles to the recipient that mimic the originals, thereby avoiding detection.
For the spy to accomplish this, the researchers imagine a particle entering a CTC so that it travels around and back in time, allowing it to interact with its future self, so to speak, before going on its way again. They describe an interaction that, in the simplest example, leaves a particle in the zero state unchanged but transforms a superposition of zero and one into a pure one state. A standard measurement by the spy that distinguishes one from zero can then reveal with complete certainty whether the initial state was zero or a superposition.
Ordinarily such a transformation wouldn’t be possible without advanced knowledge of the incoming state. The trick, Brun explains, is that the particle interacts with the transformed version of itself that comes back from the future. Brun says the scheme doesn’t violate any laws of physics, but he admits that the logic is hard to grasp. Compared with regular chronological reasoning, he says, “it’s definitely cheating.”
Sometimes you have to cheat on an idea in science to take the next leap of logic.
You can always go back later and disavow the lie — or make the cheat into a truth based on new information — but the idea that science is not always logical or true or trustworthy is a valuable lesson we must all learn.
Every day the truth changes.
Every moment facts become falsities.
Every instant the unknown becomes known.
Interesting article, David!
Let us know if you have any deeper thoughts on the matter, Gordon.