Why time travel must be impossible!

I keep getting my mind ravelled around this time travel/ bending space time stuff and it tells me one thing.

If theories are right and I were to travel to a star x light years away, by the time i return millions of years will have passed on earth. I really dont get this

My theory and understanding using a laymans common sense is this..

If there was a planet 50 light years away and i was to travel to it at 100x the speed of light, i would get there in 6 months (I think). If i was to travel back at the same speed i would have spent a physical earth year away. So how does this make any difference to the time on earth?

My watch would have run at the same speed and a year will have passed.

So.. an observer on earth looking at this planet would see it as it was 50 years ago and if i looked at earth from there.. it would be as it was 50 years ago.

However the fact that I travelled faster than light is irellevant to time, it just means that I got to my destination faster than the light did.

Is it just me who thinks this? Did that even make sense to you?? lol

[edit on 21-9-2007 by fiftyfifty]

i can under were you are coming from but it still doent mean that my mind is doing summersolts now hehe

As far as I understand;

As a perceived year in deep empty space passes, many years will have passed to the people back on Earth. It has something to do with the nature of time being relative to the gravitational potential energy in an environment.

It supposedly even changes depending on your altitude and depth inside the Earth. The rate at which everything changes in a system is slowed by the gravity of massive objects. So when you are out in your space ship and you are living your life, you say spend 5 minutes doing something and back here on Earth a generation has passed. Seems crazy doesn't it, but it is apparently provable.

Time Dilation really, not time travel.

edit:

The lower your gravitational potential, the slower your clock runs. So, it is like more of reality comes to pass in outer space than here in a defined time period.

[edit on 21-9-2007 by Darce]

[edit on 21-9-2007 by Darce]

I just don't get how that can be? The simplest way of looking at it as I said in my original post is.. if you had a watch with you, the time on it would run at exactl the same speed as an identical watch on earth right?

I do understand that you would age differently in space due to the physical environment bu that is nothing to do with time.

the time on your watch will always show you the correct time - relative to your current position. as you aproach the speed of light time slows down so to you the time would stay the same but from your point of view everyone else would have froze. So one second to you could be the same as 1 year to the rest of us.





[edit on 21-9-2007 by scepticsRus]

How could you appear to have frozen if you are travelling at that kind of speed?

sorry fiftyfifty, wrote it the wrong way around ..... i really must read what i write

First off let's get things strait, Time... what is it? It is a scale created by Carbon based life forms to measure the period of their own of decay.

It is a constant, always moving forward and never changing speed. It is felt but not visible, has no smell, taste, or sound unless you count the "tick, tick, tick, tick, tock" of a clock.

The only way to stop time is to take a photograph. The only way to visibly remember is to make a movie.

Time travel is completly possible, infact you are doing it right now without thinking about it. You are traveling forward through time at a constant of 1 second intervals.

There are several theories about traveling through time using
"Wormholes" as we know of many that exsist. The only problem with this is that it is just that, a theory.

The closest thing to traveling backwards through time is what the OP had mentioned about Lightyears and visibly veiwing it.

and finally my own theory on the only way to travel through time is through use of teleportation. But even then that is only plausable and not possible, as of yet.

Who knows maybe someone can figure it out in the future. I'm sure in the Medieval era if someone had mentioned something about a computer and using one everyone would of told them they were crazy and it is impossible....

I think what your getting at is the fact that the speed of an object warps that objects perception of time and at the speed of light, time would appear to stop for that object. This has been proven by taking two syncronized atomic clocks (which are very precise) and putting one on a plane and leaving one on the ground. It was found that the one which had been travelling around, obviously at a greater speed than the one on the ground had experienced a very slight time contortion and was now out of sync with the first. of course, tou can't accelerate an object of any mass to the speed of light anyway as it would require an infinite amount of energy!

also, check this out:
en.wikipedia.org...

basically, you can't measure time because every second can be divided in half, and then the half a second can be divided in half and so on and so on unto infinity........So how can an infinite number of units of time pass by in a second!!!!!! this can be applied to anything we measure, distance, height etc... There was an awesome thread around here somewhere on this...I'll try and find it and post a link.

[edit on 21-9-2007 by Chonx]

reply to post by fiftyfifty


Hi FiftyFifty, (found a better diagram. seemed more clear.)

You're not the only one whose confused. When Einstein developed his special and general theories of relativity many scientists were as perplexed by the results as you are. Space-time, and it's measurement, is relative to a particular viewer/measurer. Mathematically this is easy to see, but the math can be difficult. One model to help us understand the nature of time dilation is the light clock:

galileoandeinstein.physics.virginia.edu...

Imagine you are beside a train track, and you see a train approach you. On this train is a strange clock. A single pulse of light moves from the floor of the train to the roof of the train. To make this easier to picture, imagine it takes one second for the pulse of light to move from the floor of the train, reflect off the roof, and hit the floor of the train again. (Even though in reality it will seem instantaneous.)

As the train moves at normal speeds, the light will appear both to a person on the train, and an observer outside the train, to take one second to complete its round trip from floor to roof to floor. This is what our common sense would seem is right. But something weird happens as the train approaches the speed of light.

As the train moves faster and faster, the light clock will take longer and longer to complete its journey, but only from the perspective of someone outside the train. From this outside perspective, the light no longer looks like it is moving straight up and down from floor to ceiling, but rather is moving at an angle. Because the light appears to be taking this angle, it also appears to take a longer amount of time to complete it's trip from the floor of the train, to the ceiling, back to the floor again. Hopefully the diagram in the link will make my description clearer.

The really weird part about all this is that from the perspective of the person on the train, the light clock is working as it should, taking one second to make it's journey from floor to ceiling to floor.

The big question is, so whose perspective is the correct one, the outside observer or the train observer? Well, weirdly enough, they are both right. The measurement of space-time is relative to the observer, and both readings are perfectly correct.

So, a space traveler, going the speed of light, from the perspective of someone on earth, will seem like they are taking a long time, but from the perspective of someone on the spaceship, they are not taking any extra time at all.

Hope this helps. It's definitely weird, fascinating stuff.



[edit on 9/21/2007 by Toromos]

Originally posted by fiftyfifty
if you had a watch with you, the time on it would run at exactl the same speed as an identical watch on earth right?

I do understand that you would age differently in space due to the physical environment bu that is nothing to do with time.

What I am talking about doesn't have to do with humans ageing faster in zero G. Reality itself is ageing faster out there. And no, if you were capable of observing a giant clock back on Earth, the hands would appear to be hardly spinning at all. At the same moment your watch would appear to be running at a normal rate. Your perception of time has a lot to do with your frame of reference. You do not need to travel al light speed to experience this phenomenon.

[edit on 21-9-2007 by Darce]

We certainly have some real Fart Smellers in here.... *Ugh* I mean Smart Fellers in here. I like the post about the train with the clock, very visual.

That round trip taking 1 year is a measure of the earthtime you'd be away from home but the principle of time dilation would make it seem like a much shorter time to the traveller by comparison who would probably only need to pack a sandwich for the trip.

I won't get into the current theoretically imposed speed limit of C which I feel will turn out to be a rubbery barrier like the speed of sound turned out to be not so long ago

Basicly, the faster you go the slower time *appears* to move for you.

Thanks for the interesting replies folks, especially the train one.. that was nice and simple for my simple brain to understand

I kind of understand now. I agree with Parry noid. I do not think time travel is possible by travelling at high speeds however i'm not even about to get into teleportation, I can't hack that on a Friday afternoon!

If we are to achieve it, i think a new technology would need to be developed.. lets just wait and see.. well maybe I wont see. Ive only got another 80 years left maximum

I personally think that the best hope for time travel is to create a gravity well as this will bend space time.

Some scientists think that its possible that if you were to travel back in time it wouldnt be to the same dimension that you left and as such the grand father paradox simply would not apply. This would also imply that leaving the past to travel to the future would mean the same thing, you would never get back to the dimension from which you originated.

This is another interesting take on it
Time Travel Using Laser Light

What if you were to travel to the future, starting from an open area, and you ended up with a wall of a building in your position. Is it even possible that two separate matters can link up if such even did occur. This would be one issue we would have to worry about if we did have this technology.

That scenario troubles me too Dan5647

What would guarantee that the ground under your feet at the point in space-time you depart from will be the at the same level at your destination. You could materialise 100 feet above the ground/water or below it, or even within the foundations of a structure or the trunk of a huge tree.

All the paradoxes that arise when we consider the reality of accelerated time travel would indicate that it's not possible to actually visit the past/future and physically interact with it. There is the possibility to view the past though.

EG: just look at the stars and you're seeing events of up to thousands of years ago. Then travel toward those stars at high speed and you'll see their history being played in fast forward which allows you to see events before observers back home see them. This does not imply that you could change those events as they've already happened and it's just a symptom of the speed of photons carrying information about the events that gives this illusion of time displacement. If travelling at >C you could theoretically look back toward your origin and see events going in reverse because you'd be overtaking the photons that carry that information (for simplicity let's not get into doppler shifts etc ).

Time travelling is most likely possible, only in dreams and such.

In reality, I don't think you, or anybody can do the time travel, and yet like I've said before, it's probably only a man's dream and imagination of time travelling.

Time travelling probably would put lives of everyone, even the extraterrestrial individuals in danger, or death.

[edit on 22-9-2007 by TheoOne]

[edit on 22-9-2007 by TheoOne]

I would go with Einstein, time (as well as everything else) is relative. Time is also intrinsically connected to gravity, ergo YOUR time will always be personal.

MY time (here where I sit) will also be personal, but I also basically share that personal time with the rest of the world cos the world ain't that big.

Our understanding of the passing of time is just an evolutionary fact. Bit like our understanding of a particular colour or note ~ just a perception.

An easy way of looking at it for me is that when you travel closer to the speed of light, all the atoms in your body and watch spin slower. This makes it so that you age slower and your watch slows down. Ofcourse, you don't notice them slow down because your perception of time also slows down.

So if you were to fly a spaceship around the sun at close to the speed of light for 100 years, your body might age 10 years and it might only seem like 10 years, but when you get back to Earth everyone might have aged 100 years. This would be a simple way to travel into the future 100 years.

As for travelling into the past, I can only see two possibilities. The first one would be to reverse the course of the whole universe, excluding yourself. The second would require the existence of perpendicular dimensions (I just made that up then), this is like moving to parrallel dimensions where different possibilities of our universe exist. Except with perpendicular dimensions, you would be moving to dimensions of our universe that are infront or behind ours in time.

It's kind of like ripples in the water, if you sit on one ripple you might have one infront and one behind you. The ripple in front might have existed for 3 secs and the one behind you for 2 secs. So you could theoretically travel 0.5 secs forwards or backwards in "time".