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Author Topic: Is superluminal travel without relativistic effects possible?  (Read 2625 times)

Offline Space Flow

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A thought experiment:

A traveler leaves from Earth in the year 3,000 in a spaceship capable of constant 1g acceleration and  heads for a planet 1,000,000 light years away.
Now we on Earth can see the destination and understand that we are looking at it 1,000,000 years in it's past. This is not where our traveler is going. We can not see his destination as it is in our present. The light from his destination right now will not reach us for another 1,000,000 years.
Under constant 1g acceleration this traveler can get to that star according to his time in less than 3 years. Both according to relativity, and newtonian non light speed restricted additive speed.
We say that on Earth 1,000,003 years will pass before we see him arrive at his destination. But is this a valid view of how long we actually understand that he travelled for?
Considering that 1,000,003 years ago when the traveler left Earth, Earth could not see his destination as it resided 1,000,000 years in the future of the image they were looking at.

So looking at it this way, we see the fact that spacial geometry conspires so nothing is ever able to "see" anything traveling faster than light. This is totally different to whether something can actually travel faster than light?

Our traveler covered that distance in under three years and Earth 1,000,003 years later in the year 1,003,003 visually confirmed that it took 3 years by Earth clocks for that traveler to get there. They just couldn't see the end of the journey until that much time had passed, as Earth can only view this planet 1,000,000 years in the past.

The real interesting thing would be the return trip. If that traveler than turned around and returned to Earth the same way.
As far as information by light goes, You would not be able to witness the start of such a journey from Earth for a million years. At that time you would see it blue shift as it accelerates and totally disappear when it crossed light speed.
From Earths 3,003 perspective we can't see the start of such a journey. But at some point in 3,006 a Gamma ray will be registered that throughout that year will redshift into our traveler landing back on Earth.
Does this produce some sort of paradox?
Our traveler back on Earth can monitor his previous journey away from Earth, true. But as he has no way to causally influence that journey in any way, causality is maintained.
Any observers on the planet at the other end of this return journey would face a reverse scenario. They can keep monitoring Earth but at the start of our traveler's journey, their view of Earth is 1,000,000 years in arrears of their present.
Our traveler does not become detectable to them till he is decelerating bellow their viewable speed of light where he would appear as a Gamma ray that redshifts to our traveler arriving in their now reference frame.
If they happen to keep the same calendar as Earth this would be during year 3003.
When he then heads back to Earth, his 3 year journey they will watch for the next 1,000,003 years as they essentially watch that traveler head 1,000,000 years into their past. When he arrives they will agree that he arrived on Earth in the Earth and their year 3006. They of course having witnessed this in the year 1,003,006.
All because light is so slow.

Where is this wrong, and why does it not need relativity?
What is going on here?


 

Offline jeffreyH

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When he then heads back to Earth, his 3 year journey they will watch for the next 1,000,003 years as they essentially watch that traveler head 1,000,000 years into their past.

No he is traveling into their FUTURE not their past. This is more pertinent. If a traveler has a velocity of 99.999...% the speed of light and that is his inertial motion then does this counter the effects of tidal forces when approaching a black hole. The acceleration due to gravity can add very little to the travelers velocity before his speed IS superluminal.
 

Offline Thebox

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Now we on Earth can see the destination and understand that we are looking at it 1,000,000 years in it's past.

I disagree we are observing the destination in the now of the now.  We can see the destination, we can time the entire journey, the destination can time the entire journey and the traveller can time the journey, and providing they were all using the constant-'constant to time the journey, the timing will be simultaneous.

 

Offline Thebox

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When he then heads back to Earth, his 3 year journey they will watch for the next 1,000,003 years as they essentially watch that traveler head 1,000,000 years into their past.

No he is traveling into their FUTURE not their past. This is more pertinent. If a traveler has a velocity of 99.999...% the speed of light and that is his inertial motion then does this counter the effects of tidal forces when approaching a black hole. The acceleration due to gravity can add very little to the travelers velocity before his speed IS superluminal.

No he is travelling simultaneous to the destination and the start point.


Imagine this person is racing the earth to the destination, the person is travelling parallel to the earth but a radius away causing the clock to slow down, imagine both the earth and the observer travel both at c, they both reach the destination simultaneously.

 

Offline Space Flow

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Quote from: Space Flow on 28 January 2016, 17:22:45
When he then heads back to Earth, his 3 year journey they will watch for the next 1,000,003 years as they essentially watch that traveler head 1,000,000 years into their past.

No he is traveling into their FUTURE not their past.
Please explain Jeffrey.
Because as far as I can make any sense out of their point of view, they have no way of watching the traveler is being watched as he gets further and further away. An increase in observable distance is synonymous with a longer look back time. To see anything at 1 million light years away you can only observe it i million years in the past. The speed of light says so.
They are watching that traveler reach his destination from the observation point of 1 million years in their future fully understanding that what they see happened 1 million years ago.
Where does this line of logic break down?
 

Offline Colin2B

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Considering that 1,000,003 years ago when the traveler left Earth, Earth could not see his destination as it resided 1,000,000 years in the future of the image they were looking at.
This is not unusual. When I set off to visit relatives 100 miles away my arrival is in our future when I set off. They can't see me setting off, I can't see them or their house.
As the traveller moves towards the distant planet he will move through light which has left it more recently, at halfway the light will have left 500,000 yrs ago, and so on until he is in their present.
Remember also that earth and the planet are in the same inertial frame, at rest relative to each other. So their present is our present, their year 3000 is our year 3000 (if they use the same numbering system), it just takes time for each to see the others present moments.

Our traveler covered that distance in under three years and Earth 1,000,003 years later in the year 1,003,003 visually confirmed that it took 3 years by Earth clocks for that traveler to get there.
No, it took 3 yrs by the traveller's clock, 1,000,003 by earth's clock.
(An aside: I am going to use your 3yrs for both the travel time added to the time for light to travel the distance, and for the time experienced by the traveller. However, it would be quite a coincidence if they were the same. You have an accelerating journey so it isn't a simple calculation.)
The traveller cannot get there faster than light, however his experience of the time taken will be less than the total journey time as seen by earth. This is because his clocks are measuring time differently from earth's clocks (although he doesn't perceive them to be) which is why he measures the speed of light to be the same as when he was at rest.
So you need to adjust the time earth thinks the journey took, by the time dilation factor to see what the traveller experienced.

When he arrives they will agree that he arrived on Earth in the Earth and their year 3006. They of course having witnessed this in the year 1,003,006.
No, he will arrive back at earth in 2,003,006. It has taken him another 1,000,003 yrs to travel back. But his experienced, elapsed time is only another 3 yrs making 6 in all.
The distant planet will see this in 3,003,006.
« Last Edit: 28/01/2016 23:12:06 by Colin2B »
 

Offline Thebox

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Considering that 1,000,003 years ago when the traveler left Earth, Earth could not see his destination as it resided 1,000,000 years in the future of the image they were looking at.
This is not unusual. When I set off to visit relatives 100 miles away my arrival is in our future when I set off. They can't see me setting off, I can't see them or their house.
As the traveller moves towards the distant planet he will move through light which has left it more recently, at halfway the light will have left 500,000 yrs ago, and so on until he is in their present.
Remember also that earth and the planet are in the same inertial frame, at rest relative to each other. So their present is our present, their year 3000 is our year 3000 (if they use the same numbering system), it just takes time for each to see the others present moments.

Our traveler covered that distance in under three years and Earth 1,000,003 years later in the year 1,003,003 visually confirmed that it took 3 years by Earth clocks for that traveler to get there.
No, it took 3 yrs by the traveller's clock, 1,000,003 by earth's clock.
[An aside: I am going to use your 3yrs for both the travel time added to the time for light to travel the distance, and for the time experienced by the traveller. However, it would be quite a coincidence if they were the same. You have an accelerating journey so it isn't a simple calculation.]
The traveller cannot get there faster than light, however his experience of the time taken will be less than the total journey time as seen by earth. This is because his clocks are measuring time differently from earth's clocks (although he doesn't perceive them to be) which is why he measures the speed of light to be the same as when he was at rest.
So you need to adjust the time earth thinks the journey took, by the time dilation factor to see what the traveller experienced.

When he arrives they will agree that he arrived on Earth in the Earth and their year 3006. They of course having witnessed this in the year 1,003,006.
No, he will arrive back at earth in 2,003,006. It has taken him another 1,000,003 yrs to travel back. But his experienced, elapsed time is only another 3 yrs making 6 in all.
The distant planet will see this in 3,003,006.


Just no, the clock will show a different time because the clock is broken, but the time does not change for any observer in this scenario, you are quite wrong .

While the traveller travels say 100  mile at 100mph, the earth also travels 100 mile at 100 mph, so where is the difference?


like Jeffrey said, you are travelling to the destinations future , your future also, as you age 1 second, the destination ages 1 second, nothing changes.

And I am finding it funny that people think  because the speed of something slows down , time slows down, it will definitely take more ''time'' to travel a distance if the speed slows down. 







« Last Edit: 28/01/2016 23:27:51 by Thebox »
 

Offline Space Flow

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Quote from: Space Flow on 28 January 2016, 17:22:45
Our traveler covered that distance in under three years and Earth 1,000,003 years later in the year 1,003,003 visually confirmed that it took 3 years by Earth clocks for that traveler to get there.
No, it took 3 yrs by the traveller's clock, 1,000,003 by earth's clock.
(An aside: I am going to use your 3yrs for both the travel time added to the time for light to travel the distance, and for the time experienced by the traveller. However, it would be quite a coincidence if they were the same. You have an accelerating journey so it isn't a simple calculation.)
The traveller cannot get there faster than light, however his experience of the time taken will be less than the total journey time as seen by earth. This is because his clocks are measuring time differently from earth's clocks (although he doesn't perceive them to be) which is why he measures the speed of light to be the same as when he was at rest.
So you need to adjust the time earth thinks the journey took, by the time dilation factor to see what the traveller experienced.
Colin, as far as the figures go, in reality it is much closer to 2.5 years travel time each way. At 1g forgetting relativistic restrictions you go through the light speed barrier in under one year.
Now bear with me for a moment as this puzzled me even when I did Special Relativity.
So by the reference frame of the traveler he accelerates at a constant 1g to the halfway point and then accelerates at 1g in the opposite direction to arrive 1,000,000 light years away from Earth in 3 years.
Earth on the other hand from the moment he left had to track him for 1,000,003 years because he took off from Earth's present 1,000,003 years ago traveled for 3 years to arrive at a destination at a time that Earth had no way of viewing for another 1,000,000 years. So without using any relativity equations at all I can explain why the traveler's 3 year travel time took an extra 1,000,000 years to view. Because the detection system is limited in the speed it can deliver information. Nothing can be seen to travel faster than light when light is the delivery system.
Put your self at the traveler's destination. Continually watching Earth. Yet what they see is the Earth of 1,000,000 years ago. So is there any way they can see the traveler leave Earth when the destination planet and Earth are co-moving so share a now that the other will not see for 1,000,000 years?
There can't be any paradoxes. The traveler leaves Earths now to travel to another now. He gets there in 3 years. Because of the limited speed of light Earth will only be able to view this journey at the speed of light, so will have to watch it spread over 1,000,000 years. That is when the speed of light delivers the information of what happened back then. The only time dilation becomes an illusion of the geometry.
Faster than light travel is possible.
It just can not be seen to be faster than light.
 

Offline Thebox

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The only time dilation becomes an illusion of the geometry.
Faster than light travel is possible.


Sight travels faster than light, I can personally see the light leaving the object through the light that arrives because it is clear relatively.  but If you are saying time dilation is an illusion, then yes we agree.

it may take 300 years to travel to a destination but the mind see's the destination in the instant.
« Last Edit: 29/01/2016 05:46:16 by Thebox »
 

Offline Space Flow

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Am I saying time dilation is an illusion?
Unless I can debunk this view above, I don't know what I'm saying.
Perfectly good experiments and a functioning GPS say that Time dilation is real.
But when applied to something capable of continued acceleration away from a starting frame of reference, there are two effects in observation.
One the constant acceleration and two the look back time. You can only view distance by looking backward in time. But the observer traveling is not traveling backward in time. He will leave in Earths and destinations present and will also arrive in both their co moving present moments. What anyone is allowed to see and how they are forced to view it is a result of the finite speed of light and not necessarily a true reflection of reality.
Our traveler traveled for three years. The Earth will receive the light of those three years spread over both the travel time and the look back time of this journey. The traveler never crossed any look back time, but light speed communication has no  way to show that.
The Lorentz transformations certainly work well in predicting observations, but are they only a mathematical approximation of the real geometry?
Does the above way of looking at reality seem plausible? If not, how is it refuted?
« Last Edit: 29/01/2016 06:48:44 by Space Flow »
 

Offline Thebox

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Am I saying time dilation is an illusion?
Unless I can debunk this view above, I don't know what I'm saying.
Perfectly good experiments and a functioning GPS say that Time dilation is real.
But when applied to something capable of continued acceleration in away from a starting frame of reference, there are two effects in observation.
One the constant acceleration and two the look back time. You can only view distance by looking backward in time. But the observer traveling is not traveling backward in time. He will leave in Earths and destinations present and will also arrive in both their co moving present moments. What anyone is allowed to see and how they are forced to view it is a result of the finite speed of light and not necessarily a true reflection of reality.
Our traveler traveled for three years. The Earth will receive the light of those three years spread over both the travel time and the look back time of this journey. The traveler never crossed any look back time, but light speed communication has no  way to show that.
The Lorentz transformations certainly work well in predicting observations, but are they only a mathematical approximation of the real geometry?
Does the above way of looking at reality seem plausible? If not, how is it refuted?

The problem is when people consider light and consider the speed of light , they do not consider the whole of light and often look at light in respect to a single particle travelling from A to B. What they fail to consider is the importance  of what is real and reality in the consideration of the whole, in regards to sight and observation, the truth is we personally do not experience any speed of light, we can not observe light in respect to while light is propagating through space, it is relatively invisible. to us light propagating through space is a stationary reference frame irrelevant of any velocities, we do not observe space itself moving or the movement of light.

My constant-'constant explains this pretty well.


Imagine this scenario,

r=1ly


p=c


traveller from A takes 1ly to arrive at B and has aged 1 Ly


traveller from B takes 1ly to arrive at A and has aged 1 Ly


A simultaneous start ''time''


Travellers A clock has a slower rate than travellers B clock

This is completely irrelevant to the time it takes  and the ageing process.


And some gibberish - Look at a point or mark a point on the wall in your room and mark a line of sight , a Y axis,

Move in respect to the point along an x axis and back to where you started from


You would argue the point had not moved, I would argue the point is now in a different geometrical location. You move relatively to the point and space, the point moves relative to space and you.


If you stay stationary relative to the point, both you and the point simultaneous parallel move relative to space.

I do not know why but I think this gibberish is relative some how.






« Last Edit: 29/01/2016 06:55:06 by Thebox »
 

Offline Colin2B

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Faster than light travel is possible.
It just can not be seen to be faster than light.
I obviously misunderstood your scenario.
Are you saying he travels faster than light?
If so I will reread your scenario in a different light.
 

Offline Space Flow

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I obviously misunderstood your scenario.
Are you saying he travels faster than light?
If so I will reread your scenario in a different light.
Yes Colin. For the sake of this thought experiment, I am looking at a typical relativity scenario, where relativity explains two different frames of reference views, and explains the different views by way of time dilation and length contraction.
I always believed that this adequately explained why the traveler could cross vast distances in only a short experienced time while we on Earth would have to watch him doing it at almost the speed of light and no faster.
There was always a nagging in the back of my mind that there was something about that that I was missing.
The other day, it cleared. It was the fact that no one was considering the look back time for the Earth observer.
For us to watch someone's journey we are not seeing his speed. We are seeing a combination of his speed and our inability to see in real time. The further he travels the further in the our past is the point of origin of the signal we receive. So if someone according to us is travelling at .9999999999..... the speed of light he will cover 1 million light years in a bit over 1 million light years. That is what we would observe. Yet when we observe him complete that journey that we say we observed him do in a bit over 1 million light years, we leave out the fact that the light we receive of him arriving actually originated 1 million years in our past.
The travel time we are observing is an illusion brought about by the slow speed of light.
When we factor that in, we would have to agree that the traveler actually arrived at his destination 1 million years ago and it's only because of the speed limit of light that we see him traveling at below light speed for a little over 1 million years. Time dilation in this way of describing the situation is an illusion.
The traveler on the other hand, started on Earth. Before starting he looks in a futuristic detector that shows him the destination planet and measures it to be co moving 1 million light years away. He then travels to that planet at enough constant thrust to get him there in 3 years. Now even relativity allows this to happen but he sees none of that. To him and all his instruments if he is accelerating at 1g, every second that goes by his speed increases by 9.81 m/s. when he lands at his destination he looks into an advanced detector back at Earth and sees that Earth is 1 million light years away. He has crossed 1 million light years in the arbitrary figure I suggested of 3 years travel time. He also understands that the Earth he is looking at is not the Earth he left from. The Earth in his detector is a view 1 million years in the past of when he left.
Now I'm not saying that relativity is wrong. GPS proves time dilation.
I just don't know how to falsify this view, as the look back time was never accounted for in my relativity lessons.
So yes look at this scenario with the view that superluminal travel is possible but just can't be seen to happen by the use of a limited speed detection system.
As another example look at sound. Nothing can be heard to travel faster than sound. If we didn't have light detection to show us that a plane traveling faster than sound is seen in front of where we detect the sound is coming from we could not detect what is actually happening. In exactly the same way nothing can be seen to travel faster than light. Unfortunately we don't have a faster than light detection system to show us what is really going on.
Anyway have a re read under these conditions and tell me where I have fallen into a trap. I suspect I have and I just don't have the neurons to see it.
 

Offline alysdexia

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Ye're all dumb halfwits who can't learn a damned thing.  The more time spent in talking it isn't spent in thinking.  Not only did ye ignore the etýma, everyone now doesn't know what superluminal means.

Put a mirror before the farer then wave.  If you (rather, a computer) can see yourself wave in it then you are not superluminal.  Then brace for impact.
 

Offline Colin2B

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The other day, it cleared. It was the fact that no one was considering the look back time for the Earth observer.
.......
The travel time we are observing is an illusion brought about by the slow speed of light.
When we factor that in, we would have to agree that the traveler actually arrived at his destination 1 million years ago 
I can't agree that the traveller arrived at his destination 1m yrs ago.
When the traveller leaves earth he is travelling into our future and the planet's future.
Forget the yr 3000 etc, let's call now yr 0. We are currently receiving light from the planet 1m yrs ago (yr -1m), but it has taken 1m yrs to get here and they have aged 1m yrs since it left. They are also at yr 0 in sync with us.
Take the example you gave of sound. We see the lightning and then hear the thunder, but the thunder isn't stuck at the time the lightning struck, time has moved on at that location and they have the same time as as the location where we hear the thunder.
 

Offline Space Flow

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I can't agree that the traveller arrived at his destination 1m yrs ago.
When the traveller leaves earth he is travelling into our future and the planet's future.
Forget the yr 3000 etc, let's call now yr 0. We are currently receiving light from the planet 1m yrs ago (yr -1m), but it has taken 1m yrs to get here and they have aged 1m yrs since it left. They are also at yr 0 in sync with us.
Take the example you gave of sound. We see the lightning and then hear the thunder, but the thunder isn't stuck at the time the lightning struck, time has moved on at that location and they have the same time as as the location where we hear the thunder.
Thanks for considering it. Unfortunately it doesn't debunk the idea in my head yet.
I may not be stating what I see as the problem clearly enough.
As you said lets call the start year zero for both planets. Lets even say that teleportation (instantaneous travel) is possible. You take off from here and I stay behind. Even though you travelled instantaneously I have no way of seen you arrive for 1m years.
Now lets look at the above scenario again. You take off and accelerate to the point that according to relativity gives you a Gamma factor that allows you to get there in 3 years. So according to you it took 3 years to complete the journey of 1M light years. Now relativity says that me on planet Earth would have to live for 1M and 3 years to watch you complete that journey. But if I watch you arrive 1M and 3 years later, how can I possibly say that it took you that long to travel?
You left in my present 1M and 3 years ago. But what I am seen as the end of your journey is not in my or the destination planet's present. I see you arrive 1M years in the past.
How then can I justify claiming that you travelled for over 1M years? I am seen your arrival at the destination but know that what I am looking at is light that took 1M years to get to me.
Yes I agree that I watched you travel at almost light speed the whole way, but that is just the speed of light. There is no known way to watch you travel faster. The speed of light doesn't allow it. But being a smart monkey I am cappable of post processing to work out what caused me to see what I see and so work out what really happened.
You took off from my present and travelled for 3 years to be seen by me 1M and 3 years in my past. That is what I observed, after watching you for all that time.
Anyway if I am not explaining it clearly it then just remains my own personal doubt about the validity of the Lorenz transformation in this scenario.
 

Offline Colin2B

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So is your issue with the ability to verify the result?
 

Offline Space Flow

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So is your issue with the ability to verify the result?

In a sense I was hoping that someone would jump on this and point out how and why this superluminal rather than relativistic view is wrong.
I want this debunked in a way I can understand so I can go back to thinking I understand how relativity works.
I had that confidence before, to the point that I felt comfortable explaining it to others.
This viewpoint has cast a doubt in my mind and I now need it resolved.
 

Offline Colin2B

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In a sense I was hoping that someone would jump on this and point out how and why this superluminal rather than relativistic view is wrong.
Whatever problem you have with the scenario seems to be around whether or not you can verify the arrival, but that isn't necessary for a relativistic view so why should it be for a faster than light view?
I suspect folks just can't grasp what the problem is, best to sleep on it and see whether it becomes clearer.
 

Offline Space Flow

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Whatever problem you have with the scenario seems to be around whether or not you can verify the arrival, but that isn't necessary for a relativistic view so why should it be for a faster than light view?
Hmmm.. I'm not sure that exactly defines my problem.
The problem I perceive is that the relativistic view no longer seems logical to me.
You see using relativity, all you need for a factor of 1,000,000 to 1 is a speed of  0.9999999999995c or  299792.4579998501Km/s. At 1g acceleration you can achieve this speed in under one year. So a bit under 1 year of acceleration, a bit under 1 year free fall, and a bit under 1 year deceleration, gets you there in under 3 years ship time. Relativity also tells us in the same calculation that an observer on Earth will watch you complete this journey in just under 1,000,003 years. That's what we are taught, that is what I believed, until the thought struck me, that if you watch someone travel for 1000000 years at nearly light speed then you are seen someone arrive somewhere in your own past and not in real time. You only saw the departure in real time. From the moment of departure on, the look back factor distorts the observation to bring it in line with the Lorenz equation view. Yet nowhere in the Lorenz transformation is this taken into account. Yes 3 years ship time translates to 1000003 years Earth observation time. But that is because I can only view something 1000000 light years away from 1000000 years in my own future. Not because it actually took you 1000000 of my years for you to get there.
So my problem is with the relativity view.
 
The superluminal view fell out of that thought process but is not the cause of my conceptual problem.
 

Offline Colin2B

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Sorry, my fault for not having the time to check what calculations you were using.

I think the clue is in what you used to calculate ship time, relativity.
The journey is not faster than light for the rest frame of earth and the planet, it takes 1m yrs for him to get there, so 2m yrs before earth sees the traveller arrive.
For the traveller the distance to the planet is shorter and so is not faster than light. The elapsed time experienced by the traveller is only 3 yrs, but it is yr 1m for the planet (and earth) when he arrives.

It isn't surprising that the Lorentz transform matches the look-back/ftl view because it is only a coordinate transform to account for the observed constancy of light speed, they have to give the same result because you are just reversing the maths.

It all comes down to whether you think the speed of light is constant in SR, and experiments indicate it is.
 

Offline Space Flow

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It all comes down to whether you think the speed of light is constant in SR, and experiments indicate it is.
It is because the speed of light is constant for all observers under any system that I find I have this problem.
it takes 1m yrs for him to get there, so 2m yrs before earth sees the traveller arrive.
Now where did that come from. No calculation or interpretation claims 2M years as observation time for Earth. The lorenz transformation at the quoted observed speed gives 1M  and 3 years observed travel to destination.
If any of the math came to 2M years then I wouldn't have this problem.
You see to cover 1M light years at 299792.4579998501Km/s counting acceleration time and deceleration time you arrive aprox. 3 years after a beam of light sent off at your departure time.
You are not seen to be going much slower than light from Earth.
So unless you can find a way to substantiate that claim of 2M observed travel years, I still say that  observed data at the end confirm that you arrived at your destination 3 years after you left Earth. Where is the time dilation apart from the illusion  created by the constant but slow speed of light.
Yes if I could see a clock on your spaceship while you were traveling I would say that it is slower than mine by a factor of 1M to 1. But I can explain that without bringing time dilation into it. Simply because for every one of my seconds your signal is coming from very close to 1 light second further in my past.
By the end of your journey you are 1M light years away and your signal is coming to me from 1M years in my past. That is why I would have to age by 1M years to see you complete your journey and not because of time dilation.
 

Offline Colin2B

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The journey is not faster than light for the rest frame of earth and the planet, it takes 1m yrs for him to get there, so 2m yrs before earth sees the traveller arrive.
For the traveller the distance to the planet is shorter and so is not faster than light. The elapsed time experienced by the traveller is only 3 yrs, but it is yr 1m for the planet (and earth) when he arrives.
Sorry I was using shorthand in my post, for 1m yrs read 1m+3yrs, it then takes the light another 1m+3yrs to get back to earth to show his arrival, 2m+6 yrs total.

Edit: Sorry again, I realise I havn't been understanding your scenarios properly. Let me check:

1. Light speed is constant - Relativity
The journey is not faster than light for the rest frame of earth and the planet, it takes 1m+3 yrs for him to get there, it then takes the light another 1m+3yrs to get back to earth to show his arrival, 2m+6 yrs total.
For the traveller the distance to the planet is shorter and so is not faster than light. The elapsed time experienced by the traveller is only 3 yrs, but it is yr 1m+3 for the planet (and earth) when he arrives.

2. Light speed is not constant - No Relativity
It takes 1m+3 yrs for him to get there, it then takes the light another 1m+3yrs to get back to earth to show his arrival, 2m+6 yrs total.
For the traveller there is no time dilation so the elapsed time experienced by the traveller is 1m+3 yrs
Might be a good idea to fit a deadman's handle.
« Last Edit: 31/01/2016 18:38:24 by Colin2B »
 

Offline Space Flow

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That's not quite what the math says Colin.
Remember that on Earth I am watching the whole time. I see the whole journey as continuous. If I was to see it take over 2M years it would not fit the relativity mathematics.

Relativity. I watch for 1M+3 years this is counting the time for the light to get to me (otherwise I couldn't be watching). Not 2M+6 years. Nothing in the relativity equations in any way suggests 2M+6 years to see him arrive.
All the math says is that it will be 1M +3 years to see him arrive. Therefore the relativistic conclusion that Earth will age 1M +3 years to the traveler's 3 years.
That is what the Lorenz transformation says, and that is where I see the problem. Relativity doesn't take into account the light travel time, only the observed difference in time while travelling. If light travel time is taken into account than yes it should be over 2M years before Earth witnessed the traveler's arrival (if the traveler really took over 1M years to get there). That is not what the math says. It comes out as an observed time of 1M +3 years observed travel.
If the light travel time is then taken away from the relativistic answer then both Earth and the traveler would agree that even though Earth had to watch the journey "at light speed" for over 1M years, it in fact only took the 3 years the traveler experienced.
I have run the numbers again and again. I am obviously doing something wrong but can't find where.
Why does relativity not subtract the travel time for the light from the Earth observed travel time?
If it did there would be no time dilation.
That is why I made the suggestion that the traveler must have been superluminal. I can't make anything else fit.

 

Offline Colin2B

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My fault, too much of a hurry with deadlines.
I should have said, The journey is not faster than light for the rest frame of earth and the planet, it takes 1m+3 yrs for him to get there, it then takes the traveller another 1m+3yrs to get back to earth so he arrives back 2m+6 yrs after leaving. The light from his arrival on the planet will reach earth 1m yrs after he leaves the planet, earth yr 2m+3.
The elapsed time experienced by the traveller is only 3 yrs (ship time), but it is yr 1m+3 for the planet (and earth) when he arrives.
I haven't checked your calculation of 3 yrs so I'm taking it as a given.

I wonder if the issue is in your view of what observed time is? This doesn't mean 'watched time'. The term observer was originally introduced to mean measurements made in a particular frame.
Light travel time isn't subtracted because it has to be added on as I've shown above. Remember, as you watch the traveller you  are moving forward in time and all the origin points for light along his path (light emitted by him) are also moving forward in time.
 
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