Rager
Temporal Novice
Albert Einstein's theory of general relativity provides an accurate description of the causal structure of our universe. There are two main issues which make us think these equations may be unrealistic. The first is that building a time machine seems to require exotic matter, which is matter with negative energy. The other main issue is that time travel seems to contradict logic, in the form of time travel paradoxes. In science fiction, paradoxes happen whenever there is a certain event that leads to changing the past, but the change itself prevents this event from happening in the first place.
In physics, a paradox is not an event that can actually happen — it is a purely theoretical concept that points towards an inconsistency in the theory itself. Stephen Hawking's chronology protection conjecture states that time travel should be impossible. One attempt at resolving time travel paradoxes is theoretical physicist Igor Dmitriyevich Novikov's self-consistency conjecture, which essentially states that you can travel to the past but cannot change it. Introducing multiple histories When I exit the time machine, I exit into a different timeline. This takes us back to square one, since if even just one paradox cannot be eliminated, time travel remains logically impossible. We showed that allowing for multiple histories (or in more familiar terms, parallel timelines) can resolve the paradoxes that Novikov's conjecture cannot.
https://bigthink.com/hard-science/time-travel-parallel-timelines/
In physics, a paradox is not an event that can actually happen — it is a purely theoretical concept that points towards an inconsistency in the theory itself. Stephen Hawking's chronology protection conjecture states that time travel should be impossible. One attempt at resolving time travel paradoxes is theoretical physicist Igor Dmitriyevich Novikov's self-consistency conjecture, which essentially states that you can travel to the past but cannot change it. Introducing multiple histories When I exit the time machine, I exit into a different timeline. This takes us back to square one, since if even just one paradox cannot be eliminated, time travel remains logically impossible. We showed that allowing for multiple histories (or in more familiar terms, parallel timelines) can resolve the paradoxes that Novikov's conjecture cannot.
https://bigthink.com/hard-science/time-travel-parallel-timelines/