Time Travel - is it possible?
Discussion
in a time machine sense?
The Grandfather Paradox, and the probability that no-one from the future seem to have visited us suggests there could be a few issues with time travel, at least backwards, but a couple of random boredom generated musings:
1) Going to the future. If we could measure to a very precise degree everything there was to measure about the physical characteristics of a roulette wheel and ball at the moment of the ball's release and had a fast enough computer, we could fairly easily work out the winning number before the ball stops rolling, yes? The same for lottery balls. Because the winning number is not something really random, but the inevitable and calculable consequence of the physical properties of the relevant factors at play.
Similarly, at vastly larger scale, everything that happens in the future to anything is an inevitable and calculable consequence of the current state. Even 'free will' is determined by chemicals and electrical impulses in the brain. Thus, if we could know everything there was to know about today, we could calculate what happens in the future.
In the roulette example, as soon as the ball is released, we can predict what number it will stop at. So there is no need to wait for the ball to fall. We could jump 'to the future' and save the waiting.
2) Going to the past. If we were on a planet one light year from the Earth, and looked back through a telescope at our planet, we would see the past as it was one year ago. If we had a vehicle that traveled faster than light, we could travel back to the earth, along the light coming towards our telescope, and reach the Earth before the light we saw had left it. And we would have gone back in time.
Or maybe not.
The Grandfather Paradox, and the probability that no-one from the future seem to have visited us suggests there could be a few issues with time travel, at least backwards, but a couple of random boredom generated musings:
1) Going to the future. If we could measure to a very precise degree everything there was to measure about the physical characteristics of a roulette wheel and ball at the moment of the ball's release and had a fast enough computer, we could fairly easily work out the winning number before the ball stops rolling, yes? The same for lottery balls. Because the winning number is not something really random, but the inevitable and calculable consequence of the physical properties of the relevant factors at play.
Similarly, at vastly larger scale, everything that happens in the future to anything is an inevitable and calculable consequence of the current state. Even 'free will' is determined by chemicals and electrical impulses in the brain. Thus, if we could know everything there was to know about today, we could calculate what happens in the future.
In the roulette example, as soon as the ball is released, we can predict what number it will stop at. So there is no need to wait for the ball to fall. We could jump 'to the future' and save the waiting.
2) Going to the past. If we were on a planet one light year from the Earth, and looked back through a telescope at our planet, we would see the past as it was one year ago. If we had a vehicle that traveled faster than light, we could travel back to the earth, along the light coming towards our telescope, and reach the Earth before the light we saw had left it. And we would have gone back in time.
Or maybe not.
I used to think time travel was a case of flying faster than the time zones.
How naive I was
The whole light year thing wouldn't work because time is a constant. It's just that the information (light) takes time (at the speed of light) to reach us.
I find the theory of going back into the past more interesting into the future and the repercussions of such actions.
How naive I was
The whole light year thing wouldn't work because time is a constant. It's just that the information (light) takes time (at the speed of light) to reach us.
I find the theory of going back into the past more interesting into the future and the repercussions of such actions.
xjay1337 said:
I used to think time travel was a case of flying faster than the time zones.
How naive I was
The whole light year thing wouldn't work because time is a constant. It's just that the information (light) takes time (at the speed of light) to reach us.
I find the theory of going back into the past more interesting into the future and the repercussions of such actions.
No time is not a constant. The speed of light is considered constant. Given a strong gravitational field has an apparent effect on the speed of light, it is suppossed that it is time that is shifting,and not the light.How naive I was
The whole light year thing wouldn't work because time is a constant. It's just that the information (light) takes time (at the speed of light) to reach us.
I find the theory of going back into the past more interesting into the future and the repercussions of such actions.
Tricky stuff quantum physics.
bearman68 said:
No time is not a constant. The speed of light is considered constant. Given a strong gravitational field has an apparent effect on the speed of light, it is suppossed that it is time that is shifting,and not the light.
Tricky stuff quantum physics.
Is it though? Excuse my dumb scenario.Tricky stuff quantum physics.
Say I am one light year away on Planet Jay and there is someone on a planet earth. We each had the same pen held at the same height in the same gravitational scenario.
Say at exactly half way between our planets there was a really bright "GO" light. (so the message took an equal amount of time to travel to both parties)
Assuming we both reacted immediately we would both drop our pens and they would hit the ground simultaneously.
It's just that if either of us looked at each other via a telescope we would not see the pen land until the light had relayed the message.
The events both happened in the same but time we are not able to see if because of the limitations of the speed of light. 60 seconds here is the same as 60 seconds on Planet Jay, surely.
xjay1337 said:
The events both happened in the same but time we are not able to see if because of the limitations of the speed of light. 60 seconds here is the same as 60 seconds on Planet Jay, surely.
No, time is relative. Make yourself a cup of tea before you start reading:https://en.wikipedia.org/wiki/Introduction_to_gene...
The TL;DR of this is that there are two theoretical methods of time travel.
Firstly that time stops when an object travels at the speed of light or is trapped in the gravity well of a black hole (so by travelling really fast you would age much more slowly; this effect is measurable even on a transatlantic plane flight).
Secondly that since spacetime is curved it's possible to draw a straight line between two points that has a shorter distance than the distance on the plane - and if you could send something along that straight line it would appear to travel faster than the speed of light, and therefore time. That's a wormhole.
as far as we understand it going backwards in time is impossible.
There are some corners of theory that if you use exotic matter etc then you can build a wormhole to the past or go faster than light (which in essence is the same thing as time travel) but this is more down to our dodgy theory than anything else.
We can travel forward at different rates depending on speed and gravity.
There are some corners of theory that if you use exotic matter etc then you can build a wormhole to the past or go faster than light (which in essence is the same thing as time travel) but this is more down to our dodgy theory than anything else.
We can travel forward at different rates depending on speed and gravity.
The Spruce goose said:
I think one day a computer powerfully enough could predict certain things with a high accuracy ratings the problem is then once the future is know it may not then take place.
Nope, its all down to the butterfly effect and chaos theory.Up until 40ish years ago science thought everything was one big newtonian machine that yes if you could figure out the equations you could calculate everything.
Its not though. The rules can be quite simple but these end up with chaos and structure both from the same simple start! We can never know the starting point of these things with anywhere near enough accuracy to predict ( heisenberg uncertainty principle).
Science has learned to embrace chaos and work with it.
xjay1337 said:
Is it though? Excuse my dumb scenario.
Say I am one light year away on Planet Jay and there is someone on a planet earth. We each had the same pen held at the same height in the same gravitational scenario.
The events both happened in the same but time we are not able to see if because of the limitations of the speed of light. 60 seconds here is the same as 60 seconds on Planet Jay, surely.
That doesn't change the speed of light. If your planet Jay was actually a spaceship programmed to somehow speed towards earth at the speed of light the instant you got the "Go" signal, then as you arrived you would still be releasing your hand to drop the pencil whilst the guy on earth would have dropped it a year ago.Say I am one light year away on Planet Jay and there is someone on a planet earth. We each had the same pen held at the same height in the same gravitational scenario.
The events both happened in the same but time we are not able to see if because of the limitations of the speed of light. 60 seconds here is the same as 60 seconds on Planet Jay, surely.
Here's the time dilation thought experiment you want to melt your brain- Train in a tunnel near the speed of light, does it fit inside or not?
https://youtu.be/kGsbBw1I0Rg
The Spruce goose said:
I think one day a computer powerfully enough could predict certain things with a high accuracy ratings the problem is then once the future is know it may not then take place.
It is possible for your computer to predict the likelihood of a specific result. If you wanted to know, for instance, whether the EU would survive a Brexit all you need is circumstances to be reduced to data, feed it in, and then work out the percentages. As time goes by the results would be honed and would become ever more accurate.
The 'butterfly effect' has to work against a considerable inertia and whilst the activities of an insect will effect the end result, the broad results would be the same.
If you turned right instead of left, then you might not have been involved in the accident which killed you. However, this would have little effect overall if the next asteroid hits the earth as the ambulance arrives.
i think a quantum computer could do it.
'In the quantum world, the future affects the past: Hindsight and foresight together more accurately 'predict' a quantum system’s state'
http://www.sciencedaily.com/releases/2015/02/15020...
'In the quantum world, the future affects the past: Hindsight and foresight together more accurately 'predict' a quantum system’s state'
http://www.sciencedaily.com/releases/2015/02/15020...
MarshPhantom said:
If it was possible somebody would have come from the future to see us.
Big Bang Theory on this:https://www.youtube.com/watch?v=N0qDy0T5WXM
My issue with time travel has always been: what would happen to my physical form as I travelled - as it can't be in two places at once, if I travelled through time, surely my body would have to undergo all its intermediate activities on the journey?
So effectively it would just be like a FFWD/RWD button?
glazbagun said:
That doesn't change the speed of light. If your planet Jay was actually a spaceship programmed to somehow speed towards earth at the speed of light the instant you got the "Go" signal, then as you arrived you would still be releasing your hand to drop the pencil whilst the guy on earth would have dropped it a year ago.
Here's the time dilation thought experiment you want to melt your brain- Train in a tunnel near the speed of light, does it fit inside or not?
https://youtu.be/kGsbBw1I0Rg
Well my head is very confused.Here's the time dilation thought experiment you want to melt your brain- Train in a tunnel near the speed of light, does it fit inside or not?
https://youtu.be/kGsbBw1I0Rg
If you freeze frame at the exact moment the train is in the tunnel both parties surely relative lengths are diminished?
Or is the tunnel still longer for the person watching and vice versa for those on the train?
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