@Blood, Jamesbody

Nomenclature:

Hi brother.

I believe it works like this.

Relativity predicts time dilation and the existence of time dilation proves that time travel is possible, either into the past or into the future. If a person wanted to travel into the past all they would need to do is move into an area where time runs more slowly. In fact, technically speaking if you come down off a hill you have travelled into the past. This is because the closer you are to a gravitational field, the slower time becomes. Hence, we can say that time is not absolute but rather relative to the situation of the person observing it.

However, what appears to potentially be impossible is to travel either backwards or forwards within the same frame of reference. That is, in order to time travel I must necessarily cover distance. To put it another way, I am able to travel to somebody else's past or future, but not to my own. In Hawking's famous thought experiment a person is able to take a long journey away from Earth and return to the same frame of reference to potentially access the future, but again this is not their future, since they have been away from Earth's frame of reference.

If we look at it realistically, we can see that travelling to our own past or future is a seemingly insurmountable task, because everything else in the universe needs to meet the exact same conditions which existed at that time. As you will know the universe is in a constant state of acceleration, which means we would have to change the state of the entire universe in order to time travel within own frame of reference. Furthermore, even if that were a possibility, there would still have to be an absolute version of time which applies to the entire universe, and that is exactly what relativity refutes.

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xMathFanx:

@Nomenclature

When one person moves into the future at a faster rate than you do, then clearly you become his past.

Honestly, I'm not sure what you are trying to communicate by this based on your usage of the term "past". The only ways Physics currently knows how to theoretically "time travel to the past" (on a "Classical Scale") are:

A. Faster than speed of light travel

B. Tunneling to the past via a Wormhole (CTC)

C. Cosmic Strings to bend the fabric of space-time...

..The fundamental question in this debate is, "Is it possible to time travel to the past in a "Back to the Future" type format?" That is, could you travel into the past and meet your parents before you were born? Could you travel back to the "Wild West"?, ect., ect...

Amarel:

I hope you understand the problem with his post. When you are younger than your counterpart due to time dilation, you are not in their past. Time dilation does not allow us to get ahead or behind the present, by anyone’s frame of reference.

I am appealing to you on the hope that someone who typically disagrees with me isnt as intellectually stubborn as him so that one day, debate may occur

xMathFanx:

Yeah, I do understand, I think I have seen a couple of issues actually, that is why I raised the issue about his use of the term "past".

For instance, in his OP, he stated "Relativity predicts time dilation and the existence of time dilation proves that time travel is possible, either into the past or into the future." Now, there is already a problem with this initial statement because although we have experimental data demonstrating that time travel to the future happens regularly, we do not know of an instance where it has occurred to the past (in a classical sense). Now, there are potential theoretical models for which this could be achieved, but they have not been bared out through observation/experimentation. Therefore, to say the "existence of time dilation proves that time travel...into the past" occurs is not accurate.

Then he stated "If a person wanted to travel into the past all they would need to do is move into an area where time runs more slowly. In fact, technically speaking if you come down off a hill you have travelled into the past. This is because the closer you are to a gravitational field, the slower time becomes." Now, "time running more slowly" does not give you a window into the past (and I'm not sure how/why he believes it does). The arrow of time is still running forward (from your perspective) just at different relative rates. At no point is the arrow of time running backward.

In the next paragraph, he said "To put it another way, I am able to travel to somebody else's past or future, but not to my own. In Hawking's famous thought experiment a person is able to take a long journey away from Earth and return to the same frame of reference to potentially access the future, but again this is not their future, since they have been away from Earth's frame of reference." When would you have access to another person's past? You have access to two competing personal presents that now misalign in a more overt fashion (although they once appeared to align more closely) because of the various relative circumstances the people found themselves in. As for the future, yes, we know that you can travel to your version of their future in the sense that you identify with life on Earth and if you did the Hawking thought experiment, then you would return to a "future" Earth relative to your conceptual memory of it (from when you left) and other people would be older relative to you. However, the past is an entirely separate matter.

You (Amarel) said "The relativity of time does not allow you to travel to someone else’s past " Now, to my understanding (and I could be wrong, I definitely want to brush back up on my Special Relativity after this debate because I feel that I am becoming needlessly confused here and concepts are being phrased sloppily; although I have taken SR at Uni. level so this isn't just off the top of my head bs) you are correct in that statement Amarel. The only way one would get access to another's past (that we currently consider theoretically possible) is through one of the several methods I listed in a separate post (or some other theoretical framework that I did not list or hasn't been thought of yet). This is why I was confused by Nomenclatures us of the term "past" in this context. To make one correction I saw of yours also though Amarel, you said "However fast or slow you’ve traveled, when sharing a location and speed with another, it is both of your presents." Now, this is a statement that is operating on Classical Mechanics view of time. As Nomenclature rightly pointed out before, there is no universal "now" or "present". If you had an extremely precise clock out to many sig figs attached to people born at the same time, same place, and then allowed them to live their lives in separate ways, then time dilation effects are still occurring off-aligning their "clocks" relative to one another, just in an infinitesimal manner so it is effectively trivial and non-relevant in daily life (thus why it can still be usefull to model many events on Earth as though they occurred in a universal present).

Nomenclature:

For instance, in his OP, he stated "Relativity predicts time dilation and the existence of time dilation proves that time travel is possible, either into the past or into the future." Now, there is already a problem with this initial statement because although we have experimental data demonstrating that time travel to the future happens regularly, we do not know of an instance where it has occurred to the past (in a classical sense)

Your terminology "in a classical sense" does not actually mean anything. I have patiently explained that time runs differently dependent upon the frame of reference you are standing in. I have furthermore explained what the implications of this are in a real sense. It seems that you are here simply to argue, and the problem with that is that the laws of physics are not a matter of opinion.

Now, "time running more slowly" does not give you a window into the past (and I'm not sure how/why he believes it does).

I genuinely thought you were more intellectually honest than to ignore the explanations I took the time to write and simply come back with, "nah". How is it even possible that you do not understand this? I explicated in the absolute simplest terms possible. If time runs faster at point A than it does at point B, if I move from point A to point B then I have moved into the past relative to point A. It isn't complicated, mate. This is the reality, and you are responding here by refusing to understand why I am correct. That really isn't my problem.

When would you have access to another person's past?

You just asked me this precise question two hours ago and I gave you a simple answer. Do you even understand the principle of relativity in the first place? Because, forgive me, but I do not think you do. Right now, assuming you will have grandchildren, you are in their past, without even doing anything. This is because relativity stipulates that there are no absolute past, present and future. The entire point of relativity in the first place is that time is relative to where you happen to be standing. Yet you keep blathering on in such a way that you are making it absolutely clear you do not understand this fundamental point.

I have explained how time runs at different rates depending upon your frame of reference and I have explained how moving between these frames of reference can take you either to the past or the future relative to where you were previously. If you don't understand then that is one thing, but it seems more the case that you are refusing to understand.