# Time travelling

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how does a galaxy travel faster than c? link plz

It's recession velocity is greater than c. Y'know you can google yourself it's not as if there are not a wealth of websites about this.

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it doesn't matter which way it is going, matter can't travel at c. who told you it could if it was going the other way?

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it doesn't matter which way it is going, matter can't travel at c. who told you it could if it was going the other way?

:Sigh: it's a genral relativistic effect and what do you mean by the 'other way'? Recession velcoties may be greater than c as they are not due to local cooridnate velcoties, but the expansion of the universe itself. Davis and Lineweaver (2000), showed that there must be galaxies in the observable universe with recession velocities greater than c for any reasonable cosmological model.

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Hmm, I pondered over this question too, but it is not the galaxies that are moving away, it is the space that is expanding in the 4th dimension, and since space isn't really a "thing" it can travel faster than c with no problems. It is only explained that the galaxies are moving away from us, because those are the observable effects, but they aren't really the object that's moving away, just a method to explain what is observed kind of like teaching that the reciprocal of a fraction is when you flip its denominator with its numerator, instead of doing the algebra to prove it.

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As I have said in the theorys I put forward space expands from all points. The distance increases but the objects don't have to move for this to happen. But then I'm just a loony and as thales told me space don't expand that fast. By the way wheres Thales. Is he ok.?

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An interesting point to make here, is that if the universe continues to expand in this way every particle will be in its own hubble volume and will not be able to observe any other. If all the particles change into their simplest form, ie energy ie photons, then all the photons will be in a "universe" of their own as part of a type II multiverse.

Now for the sci-fi speculation.... These photons will be close to infinitely red shifted and thus have as little as possible energy..... however they can never have no energy, and perhaps in their own universe this energy will be seeminly infinite.... it may allow for a local contraction of space into a size close to a singularity... this would then proceed to expand in the manner of the big bang, creating new matter, just of a lower energy state than the former universes, but all the same equal, just scaled down.

Have I just create a new type of multiverse?

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Here's something thats been bothering me for a while (sry havent read the entire thread)

If a person goes back in time and kills the person who invented time travel, would he have been able to go back in the first place? But if he wasn't able to, then the person who invented time travel would still be alive? But then the person would be able to go back in time..

this bugged me for a few months

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that is usually refered to as the grandfather paradox. there are several answers. basically, no one knows. a popular theory is that you create a new universe when you travel back in time.

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The grandfather paradox can't happen, as I have discussed at great length in previous threads on this subject.

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The sun is not the center of the universe. Nor is it stationary. The speed that pluto is moving' date=' in relation to the earth, is not much different, considering the speed that our sun is moving in the galaxy. And the speed our galaxy is moving. Etc. Etc. I have no idea how *absolutely* fast we are moving, relative to the center of the universe, but might it be theoretically possible that something at the center of the universe, at a perfectly relativistic standstill, would be accelerated through time at a rate directly proportional to the rate at which we age, divided by the ratio of our absolute speed through the universe to the speed of light?[/quote']

Yeah, after seeing that I remember thinking up something similar a while ago now. The idea I had would be to just travel outside our galaxy and come to a dead stop, you wouldn't need to travel to the centre of the universe. Since you were at a dead stop the opposite time dilation effect of slowing should play more of a role on you, because you'd be travelling as slow as possible from the speed of light.

Wouldn't that be the time frame used on a universal scale?? Adding the speed of whichever heavenly body you were examining to find it's relative time or something like that??

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that is usually refered to as the grandfather paradox. there are several answers. basically, no one knows. a popular theory is that you create a new universe when you travel back in time.

I find parallel universes hard to accept and I think the other theory is far cooler.

You discover time travel and go back to kill your father before your conception. You can't do that because if you did you wouldn't be able to go back in time to kill your father. But if you discover the means to travel back to try and kill him something must go wrong with your insane plan, the gun you use missfires and your father kicks your arse so you end up in jail for attempted murder...

But I realised a nice twist to that which I haven't seen mentioned anywhere else so...

You go back to meet yourself 15 years ago and explain who you are and how you got back in time. So that means nothing at all can happen to prevent you getting to the time where you discover time travel. Firing a loaded gun at your head would result in a missfire. Jumping out of a plane and you'd survive.

What you'd most likely do though is freak out and become paranoid about safety, even though you knew you would live for another 15 years no matter what you did.

And if it's not already been done, I want a cut of the profits from the movie.

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The grandfather paradox can't happen, as I have discussed at great length in previous threads on this subject.

would you give us a breif synopsis of why it can't happen or a link to said threads?

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The nutshell version is that a paradox is as difficult to form as it is to resolve.

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Yeah' date=' after seeing that I remember thinking up something similar a while ago now. The idea I had would be to just travel outside our galaxy and come to a dead stop, you wouldn't need to travel to the centre of the universe. Since you were at a dead stop the opposite time dilation effect of slowing should play more of a role on you, because you'd be travelling as slow as possible from the speed of light.

Wouldn't that be the time frame used on a universal scale?? Adding the speed of whichever heavenly body you were examining to find it's relative time or something like that?? [/quote']

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The one about all motion/speed being relative?

I can understand that but why couldn't something leave a galaxy and stop moving completely??

Granted it would still be relative to all the other galaxies in the universe but it wouldn't be travelling through space, would it??

Which would mean the time dilation effect of travelling closer to the speed of light to slow time would be affecting this object in the least possible way.

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The one about all motion/speed being relative?

I can understand that but why couldn't something leave a galaxy and stop moving completely??

Granted it would still be relative to all the other galaxies in the universe but it wouldn't be travelling through space' date=' would it??

Which would mean the time dilation effect of travelling closer to the speed of light to slow time would be affecting this object in the least possible way.[/quote']

Time dialtion is dependent on relative speed only, not on spatial sepration (though spatial sepreation certianly is important to simulataneity), so if I was travelling at 0.99c relative to a very far awya galaxy then from my point of view 'clocks on that galaxy would appear to me slower and from their point of view my clocks would be running slower. Of course in there own refrence frame evryone considers themself to be at rest.

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Time dialtion is dependent on relative speed only, not on spatial sepration (though spatial sepreation certianly is important to simulataneity), so if I was travelling at 0.99c relative to a very far awya galaxy then from my point of view 'clocks on that galaxy would appear to me slower and from their point of view my clocks would be running slower. Of course in there own refrence frame evryone considers themself to be at rest.

Yes I understand what you mean.

What I'm trying to say is if you left our galaxy and stopped moving so you're not moving in relation to any other body in the universe, your atomic clock would appear to be ticking faster than anyone elses.

I suppose with the universe either expanding or contracting in size you'd still be moving but still at the slowest rate possible compared to everything else.

So to come to a true dead stop you would have to leave our universe.

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i just got an idea, though i am sure i am no where near the first to have this one.

time could be like a DVD. it can be skipped forward and back, but not changed. you may be able to go back in time, but doing so would also revert you two how you were at the time which you are traveling two. basically, the universe in rewind. memories erased due to the reversal of chemical processes. if you go back farther, you could be spread across the world or even the cosmos, though you wouldn't know it.

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i just got an idea' date=' though i am sure i am no where near the first to have this one.

time could be like a DVD. it can be skipped forward and back, but not changed. you may be able to go back in time, but doing so would also revert you two how you were at the time which you are traveling two. basically, the universe in rewind. memories erased due to the reversal of chemical processes. if you go back farther, you could be spread across the world or even the cosmos, though you wouldn't know it.[/quote']

A time machine then would not be a device for sending you into the past, it would be a device for sending the rest of the universe into the past, or should that be future??

You'd need an energy field or some similar kind of shield to cut you and your time machine off from the rest of the universe.

To do it on a smaller scale say just the planet Earth, you'd need to cut that off from the rest of the universe (press record ), then when you wanted to travel back in time you step out of the film/movie (leave Earth and join the rest of the universe again) and press rewind (only as much as you've "recorded") then jump back into the movie and press play again.

So how do we go about making our new improved DVD player??

The way I see it all we need is some rubber bands, plenty of tin foil, a big hard disk drive, a few blank DVD's and some marker pens to label the disks.

I have to go now, the nurses are breaking through the door again...

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Here's a thought I had a few years ago. Let's say you want to travel back in time using the faster than light-reversal of time method. For now let's just forget about light barriers and such.

As you accelerate towards lightspeed you move into the future. When you reach c you have travelled x amount of years into the future. Now you go faster than light, theoretically moving backwards in time. Eventually you have to slow down but as soon as you decelerate to lightspeed you start moving forward in time again. Now you finally stop, step out the door and find yourself right back where you started.

...and?

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Its an interesting position. But the problem comes when you move farther than you intend. You would have to have precise timing if you were to want to stop in the exact position you started. (Aside from the logical and technological barriers of course )

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