[Zero]

You probably know what Turing completeness is.

In computability theory, a system of data-manipulation rules (such as a computer's instruction set, a programming language, or a cellular automaton) is said to be Turing complete or computationally universal if it can be used to simulate any single-taped Turing machine.

But thinking about it, since the tape is supposed to be infinite, it's a purely theoretical object. Nothing on earth has infinite memory, hence nothing is Turing complete.

Even the human brain isn't Turing complete!
 

[Korrelan]

What if the tape is a loop... it's still infinite but requires a finite amount of memory to compute lol.

 

[Zero]

You cheater 

The loop still has a finite number of cells...