The discussion revolves around the concept of time travel, exploring whether quantum theory could make it possible. Participants delve into theoretical implications, historical examples, and the nature of time as understood through different scientific frameworks, including relativity and quantum mechanics.
Participants do not reach a consensus on the nature of time travel, with multiple competing views presented, including the relativistic and quantum mechanical perspectives. The discussion remains unresolved regarding the implications of time travel and whether it is theoretically possible.
Participants acknowledge limitations in current theories, including the incompleteness of relativity and the need for a Theory of Everything to provide clearer insights into time travel.
I read somewhere (and don't know it it's true) that Churchill had an opportunity to have Hitler assassinated and decided against it. The fear was that another believer in the cause, who would be a more effective leader, might take his place and win the war.misskitty said:it would be great if we could use the information we have about Hitler's whereabouts during the Second World War so we could go back, hunt hinm down and kill him. However, we have no idea what that would do to the future and what effects it would have.
In Michio Kaku's book, Hyperspace, Kaku explains how changing the past, according to relativity, is not possible.misskitty said:it would be great if we could use the information we have about Hitler's whereabouts during the Second World War so we could go back, hunt hinm down and kill him. However, we have no idea what that would do to the future and what effects it would have.
Relativity gives us a simple method to sort through the thorniest of these paradoxes. We will make use of the "world line" method, pioneered by Einstein.
...Our world line never really begins or ends. Even when we die, the world lines of the molecules in our bodies keep going. These molecules may disperse into the air or soil, but they will trace out their own never-ending world lines. Similarly, when we are born, the world lines of the molecules coming from our mother coalesce into a baby. At no point do world lines break off or appear from nothing.
...Our world line thus contains the entire body of information concerning our history. Everything that has ever happened to us--from our first bicycle, to our first date, to our first job--is recorded in our world line...
...With the aid of the world line, we can now picture what happens when we go back in time. Let's say we enter a time machine and meet our mother before we are born. Unfortunately, she falls in love with us and jilts our father. Do we really disappear, as depicted in Back to the Future? On a world line, we now see why this is impossible. When we disappear, our world line disappears. However, according to Einstein, world lines cannot be cut. Thus, altering the past is not possible in relativity.
The second paradox, involving re-creating the past, poses interesting problems, however. For example, by going back in time, we are fulfilling the past, not destroying it. Thus the world line of the inventor of time travel is a closed loop. His world line fulfills, rather than changes, the past.
...Thus perhaps we can fulfill the past, but never alter it. World lines, as we have stressed, cannot be cut and cannot end. They can perform loops in time, but never alter it.
In the quantum theory, we can have multiple states of any object. For example, an electron can exist simultaneously in different orbits (a fact which is responsible for giving us the laws of chemistry). Similarly, Schrödinger's famous cat can exist simultaneously in two possible states: dead and alive. So by going back in time and altering the past, we merely create a parallel universe. So we are changing someone ELSE's past by saving, say, Abraham Lincoln from being assassinated at the Ford Theater, but our Lincoln is still dead. In this way, the river of time forks into two separate rivers.