Is Time Travel (going backwards) Possible?

[Bullgrit]

No, because Hitler existed. If time travel were ever to become possible, his bedroom would have been be filled every night with thousands of would-be asssssins from the future.

But what if Hitler's existence is the lesser of evil options? What if our history was orchestrated by time travelers? Things have happened the way they have because even the very terrible things were better than the other options? Or what if the time traveler is himself evil, and chose to have Hitler rise and other stuff?

What if our history is constantly changing due to a time travel war changing everything in the past. We wouldn't know a difference between one day and the next. Yesterday the history was that the Nazis won WWII. But a time traveler changed that and now we have history as we know it. Tomorrow our history may be different, but we wouldn't know it changed.

For the record, I don't think time travel to the past is possible. But I just don't think the argument that history is as we know it is a logical argument to disprove reverse time travel.

Bullgrit

 

[Umbran]

Time travel without space travel?

Here's an important point. Time travel is equivalent to space travel. Einstein showed us that time and space are not separate entities - they are wrapped together in a single "spacetime".

FTL does not take you out of "now". No matter where you go...there you are.

Well, he's talkign about travel *near* c, not faster than C.

FTL does not take you out of "now", but "now" is *not* what we intuitively think of. There's a set of events you think of as "now". But, someone else will see those same events happening at different times. This is "relativity" - the fact that perception of the order of events is relative to the observer, not absolute.

It thus can be set up that, if you can move faster than light, you can see an event, and then move in such a way as to arrive at the location of the event *before the event happens*.

From your perspective then, that one event can happen at two different times! If you can travel FTL, then you can remember a clown at your 6th birthday party, and then on your 30th birthday you can be the clown performing for your 6-year-old self. Same event, two times, two "nows".

 

[Raunalyn]

The problem with same timeline time travel if that it did occur, and something in the past was changed, we would not be aware of that change because all future events from the point that history would change would occur in that set direction (if that made sense).

So, someone may have traveled into our past and changed something...we just don't know what it was. Another possibility that has been approached in many sci-fi and fantasy novels is that travel into the past is quite possible, but nothing can be done to change the past. Events happen that force the timeline to occur as it is supposed to.

All hypothetical of course. Einstein even accepted the possibility of time travel...it was a matter of stepping out of the stream and walking upstream a little way and getting back in.

I'm of the firm belief of multiple timelines. A multiverse where time branches off in different directions.

 

[RSKennan]

Isn't traveling forward through time just traveling in someone elses' past?

This is interesting, and I've often thought of the possibility of time as a surface; one timeline defines its length, multiple timelines define its width. In such a universe, every possibility could be predestined, existing somewhere on the surface. In other words, time is not dynamic, and the present is a matter of perspective, and yet there would be free will- you could freely travel laterally.

The part that relates to your post is the part about the present being relative.

 

[dogoftheunderworld]

No, because Hitler existed. [...] So, in my opinion, if time travel is ever going to become possible in the future, we'd know about it now.

Only if you assume we are living in the past If we are at the front edge of the timeline (i.e. the future hasn't happened yet), then the past can't be changed until time travel has been invented, which it hasn't... yet

On the flip side I time travel into the past/future every Spring and Fall, thanks to the government being able to control time

 

[Fast Learner]

What, and every person from the invention of time travel until the end of time abides by that?

Access to time travel doesn't require massive amounts of power or some other limiter that keeps it in the hands of very few?

 

[Fast Learner]

There's also an easily probable combination of time travel being possible but humankind being wiped out before discovering/inventing it.

 

[Nellisir]

It thus can be set up that, if you can move faster than light, you can see an event, and then move in such a way as to arrive at the location of the event *before the event happens*.

This is what keeps breaking my brain. I'm sure I've understood it before, but I haven't been able to recently. And the recent articles about exceeding the speed of light have brought it up again.

The light from Alpha Centauri takes about 4 years to get here. If you exceeded the speed of light and teleported there, right now, you still wouldn't journey into the past - you'd arrive right now, four years after the events that you just witnessed. You could use your ftl phone to call home and confirm your arrival, but you couldn't use it to call yourself and remind you to bring your fuzzy slippers. And if you teleported back, you'd arrive back here a few minutes after you left, not a few minutes before...although the pictures of your vacation wouldn't arrive for another four years.

Or is that all wrong? It seems like something's wrong, but I'm not sure what.

So, set it up for me.

 

[Morrus]

Access to time travel doesn't require massive amounts of power or some other limiter that keeps it in the hands of very few?

Even one person per thousand years until the end of the universe is still billions and billions and billions and billions of people.

How rare are you suggesting something can be kept forever?

 

[Iosue]

No, because Hitler existed. If time travel were ever to become possible, his bedroom would have been be filled every night with thousands of would-be asssssins from the future.

Here are two of my favorite takes on the killing Hitler issue.

The thing about using the non-death of Hitler as proof of no time travel is we have no idea how our current timeline is supposed to be different. Maybe Hitler is relatively small potatoes, and we don't know about anyone far, far worse because time travelers have already taken them out. Maybe John F. Kennedy led us to worldwide nuclear holocaust, with a death count in the billions, so...