changing the past not possible through time travel?

[echoSAW]

This has most likely been mentioned somewhere in here already, but I seem to remember reading somewhere that if "time travel" were ever possible, it would only be one way (to the future) and that would be by achieving faster-than-light travel (or some other fantastic speed) which would really just slow time down for you rather than actually jumping forward. Something like "Flight of the Navigator" but without a Pee-Wee Herman spaceship.

[belfpala]

it would only be one way (to the future) and that would be by achieving faster-than-light travel (or some other fantastic speed) which would really just slow time down for you rather than actually jumping forward.

You just need "very fast" travel for that time dilation/compresion, nothing physics-breaking. FTL travel would allow apparent time travel. That is, you'd travel from point A to point B before anyone at point B received information that you left point A.

[Deleted]

This has most likely been mentioned somewhere in here already, but I seem to remember reading somewhere that if "time travel" were ever possible, it would only be one way (to the future) and that would be by achieving faster-than-light travel (or some other fantastic speed) which would really just slow time down for you rather than actually jumping forward. Something like "Flight of the Navigator" but without a Pee-Wee Herman spaceship.

Well if you want to get really deep into the intricacy of time travel.. walk to the other side of your room.. then walk back.. congrats you just time traveled. I really cba explaining the details of how that works im too tired right now. But you are correct. We can (as far as we currently know) only travel forward in time. (also as it stands you cannot travel faster than light). In essence the faster your travel the "slower" everything around you moves. If you were to travel at light speed for 10 years then come back (aka 20 years), time on Earth would have passed multiples of hundreds of years.

There was a brilliant lecture by Prof Brian Cox on around christmas from the BBC where he explained "Dr Who" science. part of what he did looked at the possibilities of time travel. See if you can find it

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You just need "very fast" travel for that time dilation/compresion, nothing physics-breaking. FTL travel would allow apparent time travel. That is, you'd travel from point A to point B before anyone at point B received information that you left point A.

You would also have to break the laws of physics. String theory can make it possible. But we cant prove it yet. it also relies on dimensional planes where we can pop in and out the planes. Speed within the plane is governed by light. Nothing can move faster than it. Speed outside the plane is not governed by light so you could in theory go faster than it then pop back in at your destination.

[Ghostpanther]

What is time travelling forward in time if not for slowing down own time in relation to others? Why would that not be considered time travelling since it's very similar to fast forwarding? Of course any practical use of this would require significant speeds that might be close to impossible to achieve.

Time traveling is akin to taking a trip, going forward in time and then returning to the same time period ( as if nothing had happened to those you left behind ) you left. Which is impossible. Astronauts however who travel at the speed of time, time does slow down for them. That is lets say they travel at the speed of light and 3 years goes by for the astronaut , if they return to earth, more time would have taken place on earth than it did for them. However, they themselves only experienced 3 yrs of time of their life. This is possible. Which it has already been proven. But a actual time machine as seen in sci-fi Movies is pure fantasy.

So in theory, if we could travel much faster than the speed of light or somehow bend time, then we could move forward , experience like 1 year in our lives and come back, but when we did return, several more years would have taken place back on earth. This type of time travel is possible. But forget about things staying the same for your loved ones back on earth. So for practical purposes, there is no going back.

[Zoaric]

There's three prevailing theories. We don't know which one is right, so both yes and
no is my answer.

[Ghostpanther]

There's three prevailing theories. We don't know which one is right, so both yes and
no is my answer.

There is only one type of "time travel" which has been proven to be true. The one I mention above. The others are pure theory with no evidence of being true. None.

[Zoaric]

There is only one type of "time travel" which has been proven to be true. The one I mention above. The others are pure theory with no evidence of being true. None.

What evidence? We've never actually time traveled, so it's not as though any of them
have been proven or disproven; all of them are just theories. While we have a good
idea that the form of time travel you described is the only one we can accomplish, or
is even possible, I have yet to see anything other than theorizing from anyone.

[Budong]

If you were able to travel back in time, you would create a new timeline from the point you arrived. The time line you left would be unchanged and all future events for yourself would be part of your new timeline. You would essentially be stuck in the new timeline as there is no way to go back to the old one.

[Soeroah]

If time travel's possible, then at some point, some jackass is going to get a time machine. Because there's billions of years ahead of us, and many more billions of jackasses. And he's gonna take it for a joyride, or use it to deliberately screw up history, or some such thing. We don't even need some evil future regime, just one single jackass in all of mankind's potential future. One future neo-Nazi who thinks Hitler should have some phase cannons. One future chucklehead who wonders what would happen if Rome never collapsed. Etc.

Either it's not possible, or there's something WAY bigger than us that's preventing us mucking with things (and it's impossible to get around), or all of history would be rife with time travelers screwing with things.

On the other hand, if all time travel leads to a new timeline diverging, we could have billions of people in our future time traveling to the past and disappearing from our timeline altogether. That would nullify fears of our past changing, explain why none have appeared, and make the whole concept a lot more personal.

[Deleted]

You just need "very fast" travel for that time dilation/compresion, nothing physics-breaking. FTL travel would allow apparent time travel. That is, you'd travel from point A to point B before anyone at point B received information that you left point A.

Or you need a massive gravitational field, for example stable orbit around a black hole. Time dilation is rising exponentially in relation to speed, therefore orbiting a black hole is more plausible, even if it bears its own set of problems (formation of the accretion disk and so on).

FTL tachyon travel would indeed hypothetically allow to "go back", too bad the entire universe doesn't store that much energy, and thanks to the dilation you'd be at the end of the universe (atleast you'd find out if it's indeed heat death that's in for us). Alcubierre drive is more sane of the many insane proposals to fast interplanetary movement.

//

What evidence? We've never actually time traveled, so it's not as though any of them
have been proven or disproven

But he is right. Astronauts in space are technically time travellers and our satellites constantly need to be adjusted because they travel to the future (yearly by a very small margin). Clocks are ticking faster on the Mount Everest than inside Earth's core. You didn't read his post in its entirety, did you?

[belfpala]

Or you need a massive gravitational field, for example stable orbit around a black hole. Time dilation is rising exponentially in relation to speed, therefore orbiting a black hole is more plausible, even if it bears its own set of problems (formation of the accretion disk and so on).

Right, but is there really a difference in hanging out close to an event horizon and then getting away, compared to just going fast, energy-wise? I haven't ever studied that.

[Deleted]

Right, but is there really a difference in hanging out close to an event horizon and then getting away, compared to just going fast, energy-wise? I haven't ever studied that.

Whether you are travelling at 150k km/s or 200k km/s, there is no real difference in time dilation, but there is a massive difference in energy output and there are other major issues. For example heating of the ship, correction and inertia, or small particles breaking your ship apart. You'd need to maintain a speed very close to the speed of light to really feel anything. For exampe you'd only experience 10x higher dilation (1 year = 10 years) at speed just a 0,5% slower than light, which is insane to consider in practical engineering.

Orbiting a black hole at lower speeds with dilation from gravitational pull of space-time in equation is technically much more plausible to realise from a technical standpoint, but I can't really answer your question (energy-wise).

[belfpala]

Orbiting a black hole at lower speeds with dilation from gravitational pull of space-time in equation is technically much more plausible to realise from a technical standpoint, but I can't really answer your question (energy-wise).

Orbiting wasn't my question. Getting into an orbit close enough for noticeable affect and subsequently leaving that orbit was.

(I'm not un-educated on this topic; I just haven't researched this particular question).

[Clockwork Pinkie]

The whole idea of it is just that, an idea, and can't be done with all the human minds that ever existed, because things in the universe are too powerful, too complex, and too complicated for our minds to comprehend. A time machine would just consist of going into space and going through a wormhole or blackhole. Nothing 100% manmade with numbers and levers and "put year here". Going into the past, atm, seems impossible, but going into "the future", very possible, if you can accept that time is moving at it's normal pace on Earth, and whatever you're traving through is progressing you very very slowly until it decides to spit you out, and when you return to Earth, well, it could not be there. That's of course, if you survive. Or, something I've always wondered about. Travel at faster-than-light. Spend a day/week/month on another planet a human could survive on, then come back, and see how far time has gone. No wormholes needed.

[Lellybaby]

I'm afraid I cannot answer any of your questions.

Temporary Prime Directive - I'm sure you understand!

Even if you couldn't go back and change time, just being able to visit important moments in time would be one of the interested jobs ever!

All those people with Arts Degrees majoring in History would be elated!

[Cosmic Janitor]

While I think it is probably only a novel dream and will remain that way, the idea a couple pages back that if we had invented it it would have already happened is a bit shalliow tbh. Spaceflight is also possible, but I still don't tour the galaxy yet and probably never will, because there are other factors to it. Maybe it just takes unspeakable amounts of energy so that in all of existence it only happened once? Maybe it is regulated so rigorously and because of the scale, simply no jackass ever did it and caused problems? Saying it will never have happened on this basis alone is as saying spaceflight never happened, because this morning I wasn't using a rocket to get to work.

[Vercigentorix]

You could go with Hawking's opinion on this-the fact that we aren't flooded with time travel tourists is proof that time travel isn't possible. It's basically the Fermi paradox for time travel.

I considered writing a paper on Time Travel for one of my classes, my head near exploded when I got to quantum entanglement as it pertains to time travel.

[Garnier Fructis]

You could go with Hawking's opinion on this-the fact that we aren't flooded with time travel tourists is proof that time travel isn't possible. It's basically the Fermi paradox for time travel.

I considered writing a paper on Time Travel for one of my classes, my head near exploded when I got to quantum entanglement as it pertains to time travel.

But John Titor.

[Vercigentorix]

But John Titor.

Haha. Maybe Titor is part of some future government's evil plan to confuse the shit out of us and throw us off the scent of actual time travel by sending a slow kid back in time to spam us with information that proves to be false.

[Begrudge]

I started thinking again about this conundrum, I then deduced a couple of things. If you created a time machine it would have to take each of the molecules of you and preserve them as energy as you reversed the entirety of observable existence, the machine you build would have to reverse every process, including the most intricate of details, like reversing the trajectory of every single neutrino and everything down to the plank level. Everything in existence would have to have its physics reversed, but, your molecules would have to be shielded from this effect and everywhere that you were in life would need filler energy since the energy from your body would not be used in the reversal process as it would need to be preserved so that you would be able to go back with the same consciousness as to be able to change time as it moved forward again, then, you would either need to live from that time or go into space and travel near light speed back to your time, as time is relative to the speed you are achieving. Time travel to the past is then fairly hard as you can see you would need something with the power to move the entire universe in extremely precise ways as one object back however long you would need to go back. I think my brain is bleeding now. O man, and another problem arises. If you could do this you would be removing your future selfs energy from the universal equation making it so that as you moved forward in time you could be born again and then there would be two of you! Seems like the grandfather paradox is false though at least.