# The Naked Scientists Forum

### Author Topic: Time travel....into the past?  (Read 3293 times)

#### Ethos_

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##### Time travel....into the past?
« on: 14/12/2012 02:07:55 »
Experiment has shown that increasing velocity slows the passage of time relative to observers. Take a trip on a spacecraft near light speed or park your craft near a Black Hole for a time, then return to earth to discover many years have passed while you may have only aged a few weeks or months. This proves that the traveler has moved into future events relative to all stationary observers. Now lets investigate the results of time travel into the past. While there are many reasons why this is considered impossible, let's ask a few questions anyway.

Consider the results of time travel into the future: The traveler experiences a slowing of time relative to all stationary observers. However, all stationary observers experience an increase in time relative to the traveler. To be quite honest, the folks left on earth during this adventure have time traveled into the past relative to the traveler. And the reason for my logic is this:

If slowing the pace of the clock results in travel into the future, then speeding the pace up should result in travel into the past. This is, of course, all relative and depends entirely upon what one defines as time travel.

........................Ethos_

#### Ethos_

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##### Re: Time travel....into the past?
« Reply #1 on: 15/12/2012 15:00:48 »

If slowing the pace of the clock results in travel into the future, then speeding the pace up should result in travel into the past. This is, of course, all relative and depends entirely upon what one defines as time travel.

........................Ethos_
Now that I may have gotten a few of you to think about this, have any one of you realized that we may have been defining time erroneously?

Let's dig a bit deeper into this notion;  Let's assume that our astronaut can attain full light speed, 186,282 miles per second. As he spends just one second at this velocity, how much time will elapse for his comrades left back on mother earth? Now, let's push the envelope and accelerate him to c^2. What will be the result for his friends left back on earth?

If we are judging time properly when we notice the slowing progression of the astronaut's clock relative to the stationary observer, then an eternity can pass for the observer when the astronaut attains some incredible velocity. This of course can only be demonstrated with math and in reality is completely out of the question.

What this thought experiment does is raise an important question: Is it really time that has slowed when we observe the differences between both clocks? Both the astronaut and the observers on earth still live in the same universe,..................OR DO THEY?
« Last Edit: 15/12/2012 18:06:38 by Ethos_ »

#### CliffordK

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##### Re: Time travel....into the past?
« Reply #2 on: 22/12/2012 23:47:28 »
Current physics theory is that one may not be able to ever travel faster than the speed of light, although there are some theories that one might be able to warp space, essentially changing the distance.  But, that may not be the same as travelling faster than the speed of light.

Both observers, the one travelling fast, and the one travelling slow will experience a forward progression of time.

Let's think of the Europeans and the Incas, separated for about 10,000 years.
During that time, Europe became technologically more advanced than the Incas.
Consider if time had actually run faster in Europe than South America.

To Francisco Pizarro, it may have seemed like he was stepping back in time.  But in this scenario, did he actually step back in time when he sailed to South America, or did he just arrive at a continent that had followed a different time line?  Messages sent back to Europe, of course, would arrive at the proper place in the time line, and if he had returned to Europe, he would have aged normally.

I don't see travelling from the fast to the slow developing countries, or visa versa as time travel, but rather just going to a place that had progressed differently.

#### Ethos_

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##### Re: Time travel....into the past?
« Reply #3 on: 23/12/2012 00:28:30 »
I don't see travelling from the fast to the slow developing countries, or visa versa as time travel, but rather just going to a place that had progressed differently.
Exactly my friend.................and this is similar to how I view the question of time. Defining time...........? Just how are we to do this? Do we use a clock that is relative to motion and a ruler that is also rather a pesky thing to depend on when motion is involved? And how do we separate the two, motion and time? One could contend that the only thing that changed during our astronaut's trip was time. Another might have just as much right to contend that the only thing which changed was the ruler. And another might say with some confidence that they both changed. Very disturbing set of circumstances with out a doubt.

Before I stick my neck out too far, I will say one thing about what I believe. It may be impossible for anyone here to agree with, but that's OK. We can agree to disagree.

Our concept of time is flawed, IMHO. I don't believe in the future or the past, only the present. And even that is difficult because as soon as we recognize it, we call it the past. Think about the photon, according to theory, it experiences no passage of time because, of course, it's moving at the speed of light. If the light that was created at the Big Bang has experienced no aging, relative to us the observer, then relative to us, that same light has already seen it's end. Because some trillions of years in the so-called future, if people still exist, they could make the same statement that I just made. And let's take this even further, let's go all the way to the end, what ever that means. For any reasoning cognizant being that may still exist, they could utter the same words. So, what does it mean? For the photon, the future is now. The beginning is also the end. There is a saying: Time is an illusion that has purpose.

For the photon, there is only the now. For us, the difference between past and future is now and it just makes our trip a little more interesting.
« Last Edit: 23/12/2012 04:33:45 by Ethos_ »

#### UltimateTheory

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##### Re: Time travel....into the past?
« Reply #4 on: 23/12/2012 03:59:31 »
I was thinking about time travels to the past before mine main theory and came to following conclusions:

- if time travel is possible then somebody or something will be subtracted (its mass) from the Universe in the moment of beginning of time travel. It means Universe is lighter than it was before. Let's call it time t1.

- now we're moving to the past in the same Universe (as long as there is just one, no multiple Universes)- and something or somebody mass is added at time t0 - Universe is growing up, is heavier than it was. t0 < t1. But thing or somebody was there already in that form or another (atoms were used to other things, rocks, or bodies of animals that we eat etc.)

- now imagine that we're waiting dt = t1-t0 and repeating this process. f.e. dt = 1 hour.

in t0 there are appearing 2,3,4,5,6 instances of somebody or something, (....) repeat over and over again and there is infinite mass... because infinite number of exactly the same simultaneously existing atoms.

This process would end up in creating black hole at time t0..

Let's assume that multiple Universes are possible.
In such scenario- source Universe is making lighter, the more people or things abandon it, and target Universe is making heavier.
« Last Edit: 23/12/2012 11:48:40 by UltimateTheory »

#### Bill S

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##### Re: Time travel....into the past?
« Reply #5 on: 24/12/2012 22:33:36 »
UT, I’ve tried all kinds of ways of getting round this one, but the reality is that t=0 is an immutable spacetime point.  It cannot ever exist without, then with, all the people and objects that are always at that point.

However many times you might return to t=0; however many “copies” of you might turn up there, they will all always have been there.

No way round it without multiple universes, and even then it’s not as simple as it might at first seem.

#### UltimateTheory

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##### Re: Time travel....into the past?
« Reply #6 on: 25/12/2012 11:41:38 »
Quote
No way round it without multiple universes, and even then it’s not as simple as it might at first seem.

ockham's razor: the simplest answer is the most probable: multiple parallel universes don't exist and time travels to the past are not possible.

#### RE.Craig

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##### Re: Time travel....into the past?
« Reply #7 on: 11/02/2013 21:00:21 »
Take a look at any astronomical object in the sky and you are looking at the past. Even our own moon is only ever seen from earth as it was 1.25 seconds ago. What is more strange is that you only ever see the sun were it was over 8 minuets ago. You could say that when bound to the earth everything in the heavens is a recording with no live broadcasts available to us!!!

Imagine the odds of the sun and the moon and the earth being in there given positions, with there given time/speed of light delays for an eclipse of the sun to occur, it must be billions to one!!!
« Last Edit: 11/02/2013 21:13:08 by RE.Craig »

#### RD

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##### Re: Time travel....into the past?
« Reply #8 on: 11/02/2013 22:12:40 »
Imagine the odds of the sun and the moon and the earth being in there given positions, with there given time/speed of light delays for an eclipse of the sun to occur, it must be billions to one!!!

The plane of the orbit of the moon is very close to the plane of the ecliptic (about 5o out).

If it was in the plane of the ecliptic there would be a solar eclipse every month.

That we see one 8minutes late and the other 1.25 seconds late would make no difference
in the hypothetical co-planar situation described above : the solar eclipses would still be monthly.

In reality the moon is not always in the ecliptic plane, but does cross it twice a month, so that means solar eclipses are not a “billions to one” chance event but inevitable and predictable.
« Last Edit: 11/02/2013 22:19:55 by RD »

#### RE.Craig

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##### Re: Time travel....into the past?
« Reply #9 on: 11/02/2013 22:15:01 »
@Ethos "If slowing the pace of the clock results in travel into the future, then speeding the pace up should result in travel into the past. This is, of course, all relative and depends entirely upon what one defines as time travel."

What you say is correct but only if we were able to exceed the speed of light, but more importantly our experience of the past would not be one in which we were able to physically interact with. It would only ever be a visual experience.
Lets imagine we had a craft that could exceed the speed of light and that our craft was fitted with cameras with which we wanted to take pictures of the Titanic striking it's ill fated ice berg. If we wanted our pictures in 24 hours ie 12 hours there 12 hours back we would need to exceed the speed of light by @1750000x!!!The first thing we would need to do is to travel just a little further than 586 trillion miles  to get ahead of the light that left the earth 100 odd years ago, we would then need to stop and ready our really expensive Mega Tetra pixle camera then let the image of the past come to met us. We press the shutter on the camera at 11:40pm April 14th 1912.
We restart our craft and speed back to earth at the speed we left it at, 12 hours later we have pictures of an event we never believed we would ever see. But as I stated before, even if we could travel at fantastic speeds our experience of the past would always be a visual one.

#### Bill S

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##### Re: Time travel....into the past?
« Reply #10 on: 11/02/2013 23:24:44 »
RE.Craig; Apart from the science fiction bit about travelling faster than light, you are, of course, right; but we are looking into the past in that way all the time.  In no way can that be said to be travelling to the past.  Every thing we experience, we experience in our present.  Relativity assures us that that is someone else's past and future.

#### Ethos_

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##### Re: Time travel....into the past?
« Reply #11 on: 12/02/2013 00:41:40 »
RE.Craig; Apart from the science fiction bit about travelling faster than light, you are, of course, right; but we are looking into the past in that way all the time.  In no way can that be said to be travelling to the past.  Every thing we experience, we experience in our present.  Relativity assures us that that is someone else's past and future.
Absolutely my friend, and that is precisely why I expressed my belief that the present is the only reality. We may view the past as we look across the cosmos at distant stars and, someday may even observe events yet to occur by seeing into the future. But of a truth, all we may ever personally experience is the present.

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##### Re: Time travel....into the past?
« Reply #11 on: 12/02/2013 00:41:40 »