Hi
I'm new in this forum, but I was reading about what is time, and its concept is not very well defined.
UPDATE: I found a text from wired.com with an interview with Sean Carroll that do explain my point. Under there is a part that may help to understand what I'm saying!
In physics it is said that time is a dimension or a process, depending on what you think is right.
For example, if time is a dimension, it means you cannot change its properties, as you cannot distort the third, second or first dimension (it will always be first second or third). But it is observable that time does change its properties, going slower or faster (speed can change) depending on gravitional distortions (near blackholes time goes slower, for example).
If time is a process, than it does have a direction (arrow) that may or may not be changeable.
Anyway, what came to my mind is: What does a "time machine" (that makes time travel) do?
Obviously, it goes back in time. But how? How can particles "travel" through time?
I ask this because the "how" changes a lot depending on the mechanisms time travel works
What i'm trying to say is that if the "time machine" (and everything inside it) goes back in time, within a linear time line, we can imagine the classic time travelling issues and histories, as you just invert the arrow of time to get back at some past point. But I thought that, as blackholes slow times near it, what if the time machines does not go back in time? What if the "time machine" makes the universe around go back in time? That would not change the direction of the arrow of time as relative to the "time machine" you are still going throught one direction in time (isolated system?). All the issues and paradoxes of time travel would go away!
Imagine time as a linear dimension or process: If the universe goes back, than it means that each time it goes back, all the particles that make you are in the "time machine", so in the instant it stops going back all the particles that makes you will be in you: this means that there is no killing your father or going back where the time machine does not exist problem! Another you will not exist: it will simple not exist as you. Killing him does not mean killing you, because he is made of diffent particles. This keeps the linearity of time, doesnt it?
Also this leads to another problem: If the universe goes "back", or if you go back in time in a universe, it goes to a state of less entropy, which does not make a lot of sense (every moment the entropy in a isolated system increases). So you would just hop into a diferrent universe to this to work, or something that I have not thought yet....
I don't know if I explained it well, but what do you think?
I'm new in this forum, but I was reading about what is time, and its concept is not very well defined.
UPDATE: I found a text from wired.com with an interview with Sean Carroll that do explain my point. Under there is a part that may help to understand what I'm saying!
Wired.com: So what happens to the arrow in places like a black hole or at high speeds where our perception of it changes?
Carroll: This goes back to relativity and Einstein. For anyone moving through spacetime, them and the clocks they bring along with them – including their biological clocks like their heart and their mental perceptions – no one ever feels time to be passing more quickly or more slowly. Or, at least, if you have accurate clocks with you, your clock always ticks one second per second. That’s true if you’re inside a black hole, here on Earth, in the middle of nowhere, it doesn’t matter. But what Einstein tells us is that path you take through space and time can dramatically affect the time that you feel elapsing.
The arrow of time is about a direction, but it’s not about a speed. The important thing is that there’s a consistent direction. That everywhere through space and time, this is the past and this is the future.
Wired.com: So you would tell Michael J. Fox that it’s impossible for him to go back to the past and save his family?
Carroll: The simplest way out of the puzzle of time travel is to say that it can’t be done. That’s very likely the right answer. However, we don’t know for sure. We’re not absolutely proving that it can’t be done.
Wired.com: At the very least, you can’t go back.
Carroll: Yeah, no. You can easily go to the future, that’s not a problem.
In physics it is said that time is a dimension or a process, depending on what you think is right.
For example, if time is a dimension, it means you cannot change its properties, as you cannot distort the third, second or first dimension (it will always be first second or third). But it is observable that time does change its properties, going slower or faster (speed can change) depending on gravitional distortions (near blackholes time goes slower, for example).
If time is a process, than it does have a direction (arrow) that may or may not be changeable.
Anyway, what came to my mind is: What does a "time machine" (that makes time travel) do?
Obviously, it goes back in time. But how? How can particles "travel" through time?
I ask this because the "how" changes a lot depending on the mechanisms time travel works
What i'm trying to say is that if the "time machine" (and everything inside it) goes back in time, within a linear time line, we can imagine the classic time travelling issues and histories, as you just invert the arrow of time to get back at some past point. But I thought that, as blackholes slow times near it, what if the time machines does not go back in time? What if the "time machine" makes the universe around go back in time? That would not change the direction of the arrow of time as relative to the "time machine" you are still going throught one direction in time (isolated system?). All the issues and paradoxes of time travel would go away!
Imagine time as a linear dimension or process: If the universe goes back, than it means that each time it goes back, all the particles that make you are in the "time machine", so in the instant it stops going back all the particles that makes you will be in you: this means that there is no killing your father or going back where the time machine does not exist problem! Another you will not exist: it will simple not exist as you. Killing him does not mean killing you, because he is made of diffent particles. This keeps the linearity of time, doesnt it?
Also this leads to another problem: If the universe goes "back", or if you go back in time in a universe, it goes to a state of less entropy, which does not make a lot of sense (every moment the entropy in a isolated system increases). So you would just hop into a diferrent universe to this to work, or something that I have not thought yet....
I don't know if I explained it well, but what do you think?