Time Travel

[LuciferSam]

Hi guys. I'm in this debate with my dad over time travel, and neither of us seem to be able to come to an agreement. We were watching Superman (the original) and the scene came on where he goes around the world and goes back in time.

My dad says that this could work, if he were going the speed of light past the International Dateline in the reverse direction.

I disagree greatly, and here's why: the dateline has to do with the Earth's position relative to the sun. Once a body starts going past it external to the Earth, that changes the relationship. Secondly, going the speed of light makes one stay the more or less same age while everything else gets older, indirectly travelling into the future, not the past. It doesn't matter whether or not you're passing the dateline: time is a human measurement, and once you start going the speed of light, conventional measurement of time breaks down.

Thoughts?

[tovaris]

Going at the speed of light only makes time flow slover, and the knowlage of fiziks we zave today does not alove time travel. And besides the date line has nothing to do with actual time only a line on the map nothing more.

[Camazotz]

Because I'm not mathematician or physicist, the best way I know how to time travel is using a flux capacitor in a Delorian.

[Miserabilia]

The thing is you will not travel through time with that at all. The relative speed of time around you will just change.

[Magical]

Time travel is impossible, full stop.

Travel at the speed of light is impossible, (excepting the theoretical warp drive (http://techandfacts.com/warp-drive-promising-nasa-studies/)). This is because you would need an infinite amount of energy. At the speed of light your mass would become infinite. This is due to the relationship between energy and mass: E=MC^2.

[Human]

Time Dilation means time speeds up outside your spaceship as you go closer to the speed of light

At 99% speed of light 7 years on earth pass for every year on your spaceship

So we can time travel to the future with the right technology, but not to the past.
GPS satellites have to account for time dilation to keep their clocks accurate.

[LuciferSam]

And besides the date line has nothing to do with actual time only a line on the map nothing more.

This is what I keep saying! My dad doesn't seem to get it, though.

[tovaris]

This is what I keep saying! My dad doesn't seem to get it, though.

Togh luck :)

[LuciferSam]

Time Dilation means time speeds up outside your spaceship as you go closer to the speed of light

At 99% speed of light 7 years on earth pass for every year on your spaceship

So we can time travel to the future with the right technology, but not to the past.
GPS satellites have to account for time dilation to keep their clocks accurate.

Exactly. If light speed travel or near-light speed travel were possible, you could only travel into the future (sort of). There's no way to go back in time, even indirectly.

Now this next part is a little off topic, but I also feel it should be mentioned that if Superman went back to change something, this now causes the reason he had for going back in time in the first place to not exist, so by the time he returns to the present, he will not have any need to go back in time to make the change, which means the event did occur, etc. etc. etc.

Also, whatever actions he performed to "change" events occurred in the past, which means that however the present ends up, it is because of what he did in the past, so even if one does find a way to go back in time (extremely unlikely), it's not truly possible to change anything.

These paradoxes render travel back in time impossible, or at least the ability to go back and alter events.

[kenoloor]

Because I'm not mathematician or physicist, the best way I know how to time travel is using a flux capacitor in a Delorian.

or a Tardis...

[Twilly F. Sniper]

Time travel is impossible.

[Camazotz]

or a Tardis...

I also know nothing about Doctor Who.

[Cygnus]

It would be possible to make time go slower at incredible speeds, but I do not know about time travel, maybe in the future you could access your memories, but not really time travel.

[mickeymouse19]

Actually, wormholes do allow time travel. It is just that most scientists are too fixated on maintaining the theory of causuality to even think it can be possible. Basically, the "Grandfather paradox".

In Stephen Baxter's Xeelee sequence (hard sci-fi, "hard" = obeying natural laws as opposed to "the Force" etc.), this problem was solved by proposing that casuality might actually not exist at all. That would mean that in the case of a grandfather's paradox (if you go back in time and kill your grandpa you won't be born, and thus won't be able to kill your grandpa), you'd still exist despite you being never born in this universe.

That would fit in nicely into the many-worlds interpretation of quantum mechanics. Basically, by killing your grandpa you'll create another universe where you were never born, but you will still be alive because you were born in your universe. Basically, you'd become an "illegal alien" in this possibility universe, but that would not negate your existence. Killing Hitler won't change anything in your reality, it would just create another timeline where he was killed. It seems farfetched but it is not as farfetched as it seems as many-world interpretation of quantum mechanics basically says each decision/possibility creates an endless braching of timelines, not just time travel, it's just that you experience only one.

[LuciferSam]

Actually, wormholes do allow time travel. It is just that most scientists are too fixated on maintaining the theory of causuality to even think it can be possible. Basically, the "Grandfather paradox".

In Stephen Baxter's Xeelee sequence (hard sci-fi, "hard" = obeying natural laws as opposed to "the Force" etc.), this problem was solved by proposing that casuality might actually not exist at all. That would mean that in the case of a grandfather's paradox (if you go back in time and kill your grandpa you won't be born, and thus won't be able to kill your grandpa), you'd still exist despite you being never born in this universe.

That would fit in nicely into the many-worlds interpretation of quantum mechanics. Basically, by killing your grandpa you'll create another universe where you were never born, but you will still be alive because you were born in your universe. Basically, you'd become an "illegal alien" in this possibility universe, but that would not negate your existence. Killing Hitler won't change anything in your reality, it would just create another timeline where he was killed. It seems farfetched but it is not as farfetched as it seems as many-world interpretation of quantum mechanics basically says each decision/possibility creates an endless braching of timelines, not just time travel, it's just that you experience only one.

But if you went back in time and accomplished what you set out to do, i.e. killing your Grandfather in the past, you would have no reason to go back in time in the first place.