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# Does wormhole travel violate Causality?

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### #1 Pess

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Posted 24 April 2014 - 09:24 AM

I had a discussion with a physics student on this matter. He said Jim Wisniewski had written a paper that detailed how you could travel through a wormhole without violating causality (basically, travel back in time only).

I opinion that no matter how you did it, if you got from point 'A' to point 'B' faster than light, you were violating casualty from at least one frame of reference.

For example, if your spaceship entered wormhole at location 'A' and instantaneously exited at point 'B' across the Solar System. You could then just wait at point 'B' until the photons from point 'A' reach you and you would see yourself entering the wormhole--effectively putting (by your frame of reference) yourself in two spots simultaneously.

What say yea all?

Pesse (Well I am a Gemini) Mist

### #2 D_talley

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Posted 24 April 2014 - 09:46 AM

No, since you would be seeing a past event of you entering point A, since the photons would take the number of years needed to travel to you at location B.

### #3 Pess

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Posted 24 April 2014 - 10:04 AM

No, since you would be seeing a past event of you entering point A, since the photons would take the number of years needed to travel to you at location B.

I'm a little shaky on the math, but it seems to me that you could create a casualty violation by changing your reference frames as you speed toward or away from the wormhole openings. So it would be impossible for an outside observer to observe you traveling FTL without violating casualty.

I had thought of a way around it (maybe). Perhaps travel through a wormhole would be instantaneous to those aboard the ship but, because time & space are linked, to an outside observer it would appear the ship never exceeded 'c'.

In other words if the wormhole linked two points in the Universe ten light years apart, then to an outside observer ten years would pass from when the ship entered point 'A' and emerged from point 'B' of the wormhole.

The occupants of the ship, of course, would sense very little time in the wormhole and the transit would seem more or less instantaneous.

Pesse (In other words: one way travel) Mist

### #4 D_talley

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Posted 24 April 2014 - 10:42 AM

An observer on the outside would get the message from point B ten years later since light/messages would take that much time to reach the observer.

An observer would never see you pop into point A and pop out of point B at the same time because the image of you popping out of B would be subject to the speed of light sending the info to the observer.

So faster than light travel and normal communications would be a big mess.

### #5 dyslexic nam

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Posted 24 April 2014 - 12:58 PM

I had thought of a way around it (maybe). Perhaps travel through a wormhole would be instantaneous to those aboard the ship but, because time & space are linked, to an outside observer it would appear the ship never exceeded 'c'.

Pesse (In other words: one way travel) Mist

Definitely outside any kind of expertise I have, but I don't understand how people would be deemed to have traveled faster than C. If someone is essentially teleporting from one location to another by exploiting folds in space-time, then they never cross the space between - they simply circumvent that distance. Thus, if there was a wormhole between Toronto and Havana, someone traveling through it would never have physically crossed the continental US. It is true that they would have traveled faster than C if they had physically crossed the distance between the 2 points, but the idea of wormhole travel (as I understand it) is that they wouldn't travel over that intervening distance since they are exploiting a sort of direct conduit between the 2 points. If true, they never would have physically accelerated to a speed approaching C. This may not matter for the purposes of some discussions, but I would think it would have implications for any theory (like yours) that would tie wormhole travel to a subsequent lapse in time to account for the distance "traveled" at FTL speeds.

### #6 scopethis

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Posted 24 April 2014 - 01:10 PM

wormholes have NO distance, they are folds in space-time; actually a portal, a hole, not a tunnel..sorta like flattening your house, opening the front door and stepping into the back yard...

### #7 Pess

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Posted 24 April 2014 - 01:27 PM

wormholes have NO distance, they are folds in space-time; actually a portal, a hole, not a tunnel..sorta like flattening your house, opening the front door and stepping into the back yard...

We can throw out Wormholes and substitue any mechanism that provides FTL travel.

Casualty depends on events happening one AFTER another and this breaks down at speeds in excess of 'c'.

I am trying to figure out a simple example of why this is, but going FTL effectively means you are going backwards in time....and I, for one, don't want to meet myself in a dark ally somewhere.

Pesse (<sings> We've only just begun...what?...oh, never mind) Mist

### #8 dyslexic nam

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Posted 24 April 2014 - 01:57 PM

It may be a given for folks better versed in the topic, but why would going faster than C mean that you are going backwards in time, and therefore impact causality? Based on what you have said, you are never actually in 2 places at one time, even though it may appear as such to a 3rd party. Similarly, your pre- and post-wormhole characters can never interact with each other, or simultaneously with a 3rd party - both because of the distances involved and because their simply isn't anyone still at your departure point. You might arrive at a given point before the visual information of your departure gets there, but I still don't get how this implies time travel. My luddite understanding of TT is that it would require you to travel to a point in time prior to your wormhole entry - not simply to appear to have done so based on the perspective of an observer.

### #9 maugi88

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Posted 24 April 2014 - 04:33 PM

I, for one, don't want to meet myself in a dark ally somewhere.

Why? Are you a mean?

### #10 maugi88

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Posted 24 April 2014 - 04:35 PM

Are we positive worm holes even are possible? I mean they are a neat idea but......

### #11 Pess

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Posted 25 April 2014 - 08:47 AM

I, for one, don't want to meet myself in a dark ally somewhere.

Why? Are you a mean?

Pesse (Yes) Mist

### #12 maugi88

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Posted 25 April 2014 - 03:23 PM

I, for one, don't want to meet myself in a dark ally somewhere.

Why? Are you a mean?

Pesse (Yes) Mist

Good to know!

### #13 Pess

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Posted 28 April 2014 - 10:04 AM

I guess the only way not to violate casualty would be that for any FTL mechanism, the travel would take (to any outside observer) just as long as the speed of light limitation.

So although travel through a Wormhole, or rotating Black hole or whatever...to the travelers the trip might be instantaneous (time stops at the speed of light so no passage of time would be noted by the travelers clock).

However, to the outside Universe a trip of ten light years would take at least ten years as measured by any other reference frame in the Universe.

Maybe that's why the Universe seems kinda empty: Travel away from ones home planet is almost always one-way.

Thoughts?

Pesse (The Big cop of the Universe is a stickler for enforcing the speed limit) Mist

### #14 scopethis

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Posted 28 April 2014 - 04:29 PM

but if you could travel several times the speed of light you could return home before you departed...

### #15 Pess

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Posted 28 April 2014 - 04:37 PM

but if you could travel several times the speed of light you could return home before you departed...

Pesse (Handy if you forgot your toothbrush) Mist

### #16 PeterR280

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Posted 28 April 2014 - 04:39 PM

but if you could travel several times the speed of light you could return home before you departed...

Not really.

If you actually transported (not traveled) to a star 10 light years away, then transported back after a few miutes, you would be back in a few minutes. You would have to wait 10 years to see yourself on the star when looking through (a very powerful) a telescope.

### #17 Pess

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Posted 28 April 2014 - 04:59 PM

but if you could travel several times the speed of light you could return home before you departed...

Not really.

If you actually transported (not traveled) to a star 10 light years away, then transported back after a few miutes, you would be back in a few minutes. You would have to wait 10 years to see yourself on the star when looking through (a very powerful) a telescope.

The problem with that statement, even though it sounds logical, is that it assumes Space & Time are discreet things. However, Einstein has showed us that spacetime is one and the same. Therefore, moving like that through a wormhole would violate casualty under certain circumstances (not all) since you could travel back in time as well as space.

Pesse (I am still trying to come up with a good thought experiment) Mist

### #18 PeterR280

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Posted 28 April 2014 - 06:41 PM

That's why I said transported versus traveling through space. There are also issues with defining simultaneity when you are moving.

### #19 Pess

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Posted 29 April 2014 - 10:14 AM

That's why I said transported versus traveling through space. There are also issues with defining simultaneity when you are moving.

Here is the problem as described to me. This graph is drawn from memory from other people smarter than me.

Look at the graph. Going up the 'X' coordinates reflects the passage of time from present. Going right along the 'Y' coordinates reflects movement through space.

The Green area reflects the speed of light as it spreads through time & space.

Note that a worm hole that connects points 'A' and points 'C' in space does not violate casualty because events happen in proper time order. However, a wormhole that connects 'A' with 'B' is actually outside the time curve and reflects travel back in time violating causality.

Therefore, if Wormholes exist they can not allow travel beyond what would be accomplished by just under FTL travel.

Pesse (Dunno) Mist

### #20 dyslexic nam

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Posted 29 April 2014 - 12:41 PM

I still don't understand where in the graphical representation you get anything that represents time travel into the past. Both Point B and Point C occur above the horizontal line representing "now".

Going up the 'X' coordinates reflects the passage of time from present. Going right along the 'Y' coordinates reflects movement through space.

As quoted, going up the X axis reflects the passage of time from present. Thus, the location of Points B and C - both above the horizontal 'now' line - represent events that occur after the departure event of Point A. For something to have happened prior to Point A, it would have to occur below that horizontal line. This would also require that entry into a wormhole allows one to exit into the past - not just into a place that has not yet been reached by the light of one's departure - and if this were the case then wormhole travel would most definitely conjure up all the traditional paradoxes of time travel.

You seem to be equating time travel to the ability to arrive in a place before one's departing photons. Maybe I am being too linear in my thinking, but this seems like a theory of time travel that describes something other than actual time travel. My understanding of TT (that is not simply moving forward in time) involves the potential to arrive somewhere at a time that occurs before actual departure. Based on your description and graphical illustration, this is not the case.

### #21 Sgt

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Posted 03 May 2014 - 02:27 AM

What would happen if you travel through a wormhole? :-)

### #22 maugi88

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Posted 04 May 2014 - 03:07 PM

You would get to the other side.

### #23 GregLee1

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Posted 04 May 2014 - 04:08 PM

Yes, but who cares? Causality can be paraphrased: there are no wormholes. But that will be true only until a wormhole is found. Causality is more a matter of fact than it is a physical law. It's like: Earth is the only planet with chocolate.

### #24 scopethis

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Posted 04 May 2014 - 04:31 PM

where do Mars Bars come from?

### #25 GregLee1

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Posted 04 May 2014 - 05:59 PM

So you're saying there never was any causality?

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