# Why can't we time travel in backward?

Why can't we time travel in backward??

Consider a person traveling in space (Straight road)
O
<|>
/\
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0 Km 12 Km
He travels at 100 m/s and completes 12km in 2 minutes.

Now plotting the time line
O
<|>
/\
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0 Seconds 120 seconds

Here are my observations

1) He loses 2 minute of his life
2) Space "CHANGES" (moves forward or backward - the person can move 12 km in any direction) BUT time "ADVANCES" (can move only in forward direction)

NOW....time and space travel are like lateral inversions yet symmetrical...its trivial as it is

Thus, if we were to perform time travel, then
Time "CHANGES" (moves forward or backward) BUT space "ADVANCES" (can move only in forward direction - which means we can go to the space in future, not in the past)
Thus we cannot time travel backwards...

This is my observation and I am just a degree student searching for research areas and I made this observation just now..I would like to take opinions from great brains and professionals

Pengwuino
Gold Member

NOW....time and space travel are like lateral inversions yet symmetrical...its trivial as it is

Explain this statement, I don't understand what you're trying to say.

Thus, if we were to perform time travel, then
Time "CHANGES" (moves forward or backward) BUT space "ADVANCES" (can move only in forward direction - which means we can go to the space in future, not in the past)
Thus we cannot time travel backwards...

Again, I don't understand what you're saying in the slightest.

NOW....time and space travel are like lateral inversions yet symmetrical...its trivial as it is

What I meant by this is that time and space are the coordinates

Thus, if we were to perform time travel, then
Time "CHANGES" (moves forward or backward) BUT space "ADVANCES" (can move only in forward direction - which means we can go to the space in future, not in the past)
Thus we cannot time travel backwards..

Now this means that in normal travel time moves only in forward and space changes in any direction
In time travel the reverse happens which means that space can move only in forward direction which is the future

phinds
Gold Member

Uh dude ... what direction is forward?

I think the whole thing sounds like nonsense

256bits
Gold Member

Interesting idea.

Any direction..if we are traveling in space we can travel in any direction say east or west or south.
And Yes it could be complete nonsense but please tell me which part sounds nonsense to you.

BruceW
Homework Helper

To say time only moves in one direction is not specific. Why should it move in one direction? For example, if we're talking about billiard balls, then we can calculate the position of billiard balls at specific times, but there is nothing to say that time flows in one direction.

There are 3 examples where time does flow in one direction, (According to a book I read by Paul Davies). These are:
Thermodynamic - i.e. entropy always increases or stays the same with time
Cosmological - because near the big bang, the universe had high density and since then, density has been decreasing.
Psychological - we only remember the past, not the future.

I'm not sure if Davies is right, but is your question about one of these? I think your question about the direction of time doesn't have a simple answer.

To say time only moves in one direction is not specific. Why should it move in one direction? For example, if we're talking about billiard balls, then we can calculate the position of billiard balls at specific times, but there is nothing to say that time flows in one direction.

There are 3 examples where time does flow in one direction, (According to a book I read by Paul Davies). These are:
Thermodynamic - i.e. entropy always increases or stays the same with time
Cosmological - because near the big bang, the universe had high density and since then, density has been decreasing.
Psychological - we only remember the past, not the future.

I'm not sure if Davies is right, but is your question about one of these? I think your question about the direction of time doesn't have a simple answer.
Nooo...that's not in my question but I like your point.

Its like this
In normal travel (like on car, walking) time increases(moves forward) and space changes.
Which means that in time travel space can move in forward only i.e time travel into the future

BruceW
Homework Helper

But the reason you say time travels forward when you are walking is because you remember your watch being at an earlier time, and you remember being at some other position at an earlier time.

Your question looks like it is about the psychological arrow of time.

If you imagine the person's path through spacetime, you could justify that either direction is forward through time (except for the arrows of time I mentioned before).
Of course, if you define the direction of time, then all the people on earth would agree on the direction of time, since we share the same frame of reference.

Special relativity does prohibit a circular path through spacetime (i.e. meeting up with your former self). Is this what you meant about time travel?

Andrew Mason
Homework Helper

Start the analysis by asking the question: what does it mean to go back in time? I think it has to mean that the entire universe returns to a previous state and thereby erase all evidence of its present state. If some part of the universe does not return to a previous state, it could be used as a clock to show that time reversal had not occurred.

In order to reverse time for even one millisecond, every particle in the universe would have to reverse its direction by exactly 180 degrees without losing any speed. The planets would all have to reverse direction to go back to where they were a millisecond before. Then the would have to reverse direction again so they would be moving in the direction they were moving one millisecond before. And, of course, no one could observe this time reversal because if they could, it would be evidence that time had not reversed.

Let's look at it macroscopically using a thermodynamics approach. In order for the entire universe to return to a previous state, it would need to go through some form of thermodynamic process. Since moving from that previous state to the present it did not go through a reversible process, it will require that more useful work be done to return to that state than was generated in the forward thermodynamic process. So the universe's supply of low entropy sources have to be consumed (ie. the entropy of the universe has to increase). So, time really has not reversed.

In short, time cannot be reversed because the universe is too complicated.

AM

phinds
Gold Member

Any direction..if we are traveling in space we can travel in any direction say east or west or south.
And Yes it could be complete nonsense but please tell me which part sounds nonsense to you.

Let's just focus for a minute on my question about direction. The term "forward" has no meaning in physics. You have to specify spacial coordinates. How can you possibly specify "forward" as a general concept? I contend that you cannot. The word really only has meaning in human terms. If I'm walking South, that's forward for me, but that has no meaning in physics and to use it as the basic of a far-fetched theory seems particularly nonsensical.

As something like playing with words, your concept is very clever but I don't see it having any possible bearing on reality.

LATER ADDITION: by the way, I don't pretend to be an expert and I'm willing to be wrong in my point of view but I think I have it right.

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So can we time travel to the future?? will that be more complicated???

SteamKing
Staff Emeritus
Homework Helper

We time travel to the future a day at a time, every day.

We time travel to the future a day at a time, every day.

I meant to travel into the future at a higher rate..like travel to 2111 AD..
will that be possible or more possible than time traveling into the past?

BruceW
Homework Helper

definitely. Just become an astronaut. They travel into our future slightly. I.e. they will age slightly less than us on earth because they are in a high-speed orbit.

BruceW
Homework Helper

I've tried to think a bit more about why it seems time is different to space - how Arjun was saying that we go left and right in x - and can return to the same spatial coordinate, but we can't return to the same time.

I've thought about it like this: we humans all travel almost entirely in the same direction of spacetime - that is the component we have labelled time. Which is why we have to make a huge change in our 4-velocity to get back to the same time (only possible by a wormhole or similar). But we only need to make a very small change in our 4-velocity to get back to the same point in space.

Just last week I felt what feeled like an electromagnetic field on my arm but I couldn't feel it on my hand when I positioned my hand where my arm was. About an hour later I experienced what seemed like myself having travelled back in time and reliving an hour.

Hello Aujun.

In short, time cannot be reversed because the universe is too complicated.

There is another way of viewing what Andrew Mason said

look at posts 8 and 11 of this thread

and ask your self what you mean by time travel, either forward or backward and why your idea of time travelling is fundamentally different from moving in space.

Hey guys,

I have a confession to make..
It seems that I could see the future in dreams..It sounds stupid but since Newtype has mentioned his experience I think it is worthy to share mine too..
I was (and still am) able to see the future(not far future just 6 or 7 hours)...Its no big deal but I see this through dreams..
I could see which episode will come on "courage:the cowardly dog show" that day or what food will my mom cook for breakfast..
I have also tried to control these dreams and become a lucid dreamer http://en.wikipedia.org/wiki/Lucid_dream" [Broken]

I was not so unsuccessful and at times I could control these..

Do you guys think that if we cannot physically travel into the future, we could travel spiritually through dreams?Or are all these just tricks played by our mind?

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Hey guys,

I have a confession to make..
It seems that I could see the future in dreams..It sounds stupid but since Newtype has mentioned his experience I think it is worthy to share mine too..
I was (and still am) able to see the future(not far future just 6 or 7 hours)...Its no big deal but I see this through dreams..
I could see which episode will come on "courage:the cowardly dog show" that day or what food will my mom cook for breakfast..
I have also tried to control these dreams and become a lucid dreamer http://en.wikipedia.org/wiki/Lucid_dream" [Broken]

I was not so unsuccessful and at times I could control these..

Do you guys think that if we cannot physically travel into the future, we could travel spiritually through dreams?Or are all these just tricks played by our mind?

.......................................................:uhh:

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phinds
Gold Member

Hey guys,

I have a confession to make..
It seems that I could see the future in dreams..It sounds stupid but since Newtype has mentioned his experience I think it is worthy to share mine too..
I was (and still am) able to see the future(not far future just 6 or 7 hours)...Its no big deal but I see this through dreams..
I could see which episode will come on "courage:the cowardly dog show" that day or what food will my mom cook for breakfast..
I have also tried to control these dreams and become a lucid dreamer http://en.wikipedia.org/wiki/Lucid_dream" [Broken]

I was not so unsuccessful and at times I could control these..

Do you guys think that if we cannot physically travel into the future, we could travel spiritually through dreams?Or are all these just tricks played by our mind?

I'm not sure what your purpose is to be here on this forum but I suggest you read the rules. This kind of nonsense can get you banned. This is a forum for serious physics. I don't know that this post breaks the rules for overly speculative posts, but if not, it's pushing the limit.

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If we're not supposed to talk about ESP activities, then why has this website in the past advertised Gerald O'Donnell's Remote Viewing and Remote Influcencing courses? Also, doesn't this topic belong on the forums that talk about quantum mechanics? By the way, I too have had prophetic dreams:

*When I was in my freshman year of high school, I dreamed I was taking a test in my physical science class. In that dream I saw a question and its number and myself circling an answer for it. Then I dreamed of the girl in my dream grading my test. I then saw myself getting a B+ on that test. In my dream I saw myself asking my physical science teacher about that question and he explained the correct answer. Later when I took that test in real life I saw that same question and the same number of it and I chose the answer that my physical science teacher told me in my dream (I got that answer correct). The person that graded my real life test was the same girl that graded it in my dream. I got an A- on that test in real life.

*Another dream I had was when I was in my freshman year at high school and I saw a car my parents purchased - in that dream it had a white paint job and a blue interior. A few months in real life later my parents purchased a white car with a blue interior.

*A few months ago I had a dream that I was sitting in front of a computer screen at my sister's house. Later in real life I did sit in front of that computer screen at her house.

*A few months ago I had a dream in which I was looking at a forum topic. Later in real life I was at that forum looking at that topic
.
*Just last night I had a dream in which I was asking where a friend of mine by the name of Brian was sitting at in a large room of people and I gave him some YuGiOh! cards. This morning I asked where Brian was sitting and gave him some YuGiOh! cards.

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Drakkith
Staff Emeritus

Not only can you experiences most likely be explained by other effects other than true precognition or something, this post is also seriously off topic and probably ready for a lock.

perhaps this is the wrong place to add this.. I tend to fall towards time as measurement created by humanity to keep things orderly. Time is only measureable from a defined point. If you remove the reference points, there isnt a way to measure it. There inst a forward or backwards, only existance. Could it be considered that time is the perception of the individual in any one space at any given time.

For instance, one has the ability to move into the future 1 hour. During the course of the movement the past and future exist for the individual, and the individuals that know the time traveler exist in the past while the individual moves forward in time. Does the past simply catch up to the time traveler or do multiple universes exist where the individual might exit ahead of themselves in a different time line?

Using that thought, assuming the same universe, could you slow down to a point where you could exit in the past of the time line you left while the people who are aware of your existance speed past you? I know this would still be considered forward motion in time, though exiting in the past of your current time line.

I dont think I am accurately conveying my thoughts.. perhaps one of you might understand what I am trying to say

BruceW
Homework Helper

If you would like to find out about what physics has to say about time, then you should learn about Einstein's relativity.

In the limit of small differences of velocity, and if we only include Galilean reference frames, we get Newtonian physics. In this case, the change in time between two events is the same according to everyone, and therefore simultaneity of two events is absolute.

So time as a physical concept is more than just something which is perceived by humans.

There is only one universe. If you've seen films where people go back in time, creating a new parallel universe, this is only a science-fiction idea. Its not rooted in anything scientific. (Even the quantum many-worlds theory doesn't literally mean there are multiple universes, only that outcomes of experiments effectively create non-interacting states which evolve independently).

I've not fully understood all the things you were talking about, but hopefully I've given some help in explaining time as a physical phenomenon.