Time travel is impossable

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sarephina said:
What is the difference between Newtonian and Einsteinian speeds of light?
In Newtonian physics, light is the fastest speed in the universe, attainable only by light. Speed in this case relates to motion through space only. Time is irrelevant, except in its ability to be used to measure motion through space.

In Einsteinian physics, light is the only speed in the universe. Motion through space and time is symmetrical, such that an increase in motion through one results in a symmetrical decrease in motion through the other.


sarephina said:
why isn't the Earth twin younger with respect to the spaceship one? Since the spaceship twin was unmoving wrt himself, everyone else should have been travelling near the speed of light, so he should age and they should not.
To give the brief answer, you are correct that each went at the speed of light with respect to the other. Howver, the one in the space ship underwent accelearation with respect to the other, and this is the critical factor.
 
  • #52
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Prometheus said:
To give the brief answer, you are correct that each went at the speed of light with respect to the other. Howver, the one in the space ship underwent accelearation with respect to the other, and this is the critical factor.
But wrt the spaceship twin, didn't the rest of the world accelerate while he remained still?
 
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  • #53
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sarephina said:
But wrt the spaceship twin, didn't the rest of the world accelerate while he remained still?
You are asking if the entire universe accelerated, whereas only the space ship remained in contant motion. I don't exactly know what you mean by "world", but you must mean more than the earth, as you can't be meaning that the earth might leave the solar system by its acceleration.

I am not exactly sure how to answer your question, but I will try.

If you accelerate in a car, you can tell that you are accelerating, because the force of acceleartion can be felt. People who went to the moon surely felt the acceleration as their ship left the earth. Therefore, it is not arbitrary which one is actually accelerating. This is not a case of two bodies in constant motion through space at different speeds.

I suggest the following 2 cases:

Case 1: The space ship is the one that accelerates. and not the rest of the entire universe. This is what I suggested. The people in the space ship will surely be aware of much of this acceleration.

Case 2: The entire universe accelerated, but the space ship is the only thing in the universe that remained in contant motion. What might cause this to happen? I think that it is impossible. However, if it were possible, then whatever caused the entire world to accelerate should cause the space ship to accelerate with it as well. This is due to gravity. Yet, the space ship did not accelerate with the gravity around it. Therefore, it must have decelerated with respect to the rest of the universe in order to maintain its constant motion. Deceleration is negative acceleration. Again, the space ship accelerated.
 
  • #54
selfAdjoint
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sarephina said:
But wrt the spaceship twin, didn't the rest of the world accelerate while he remained still?

Unlike velocity, acceleration is not relative.
 
  • #55
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Time trqavel is inevitable

We are all traveling through time while sitting in our chairs (into the future)
 
  • #56
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hehehe world, universe... big difference... :redface:

O, acceleration is not relative.... I think Prometheus was saying that, but unfortunately, I still don't get it. Wouldn't the same thing (negative acceleration to remain still despite gravity) apply to the spaceship moving at a constant velocity?

But what if we just can't feel the acceleration because our mass is so large that by F=ma (will I get rotten eggs in my hair for bringing up such a tiny equation?), our a is almost (or is?) negligible?

---

Sitting in our chairs and traveling through time... I think that's more like following a current. Can we go against or beyond the current?
 
  • #57
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check out my other post
faster than the speed of light

if you read it
or already have data

any ideas
lemme know
thanx
 
  • #58
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There was a time where man thought that the speed of sound was unattainable. We can not say something can not be done unless all possibilities from all future generations have been exhausted. Remeber At one point cars were just a concept.
 
  • #59
shadowman said:
Time travel is impossable. you cannot "travel through time" because time is intangible. Time is not a relm or a dimension. Time is a concept. It is a concept designed by early man as a way to track and orient hisself with the daily movements of the earth. The passing of events is what man knows as time. Man also devised the hour, minute, second, millisecond, nannosecond and so on and so forth. These are used as a measure of the concept of time. Therefore, you cannot travel into something is a concept.
Also, look at it this way. Our only link with the past is our memory of it. And the only link to the future is predicting certain aspects of it by information that is happening now. what happened a few hours ago is gone. no more. there is not a " place" to travel to. when a moment in time passes by, it no longer exsists. how can you travel to somewhere that doesnt exist, or hasnt existed yet?

So because man devised time (the hour, minute, second, millisecond, nannosecond, etc.) we cannot manipulate time?

sort of like saying because man devised numbers to keep track of goods, (the integer, floating point-integer) and devised operands (plus, minus, etc.) then manipulating numbers is impossible - since math isn't a dimension, isn't anything "tangible" - its simply man's "out there" creation. Sort of like time.

is that how you're trying to convince us?
 
  • #60
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shadowman, you are not thinking 4th dimensionally
 
  • #61
time is simply a perception motion. Time is not another dimension.
If everything in the universe came to a complete stand still i.e. no motion what so ever you could could still measure x to y but how would you measure time it becomes non existant until motion happens again than between no motion and motion we would percieve time.
 
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  • #62
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freezing of all motion. absolute zero. we haven't been able to achieve that yet. i wonder if time would stop if we did.
 
  • #63
If all motion were to freeze would'nt that, to some extent, effectively support the concept of time being a tangible dimension? Of course, this would be irrelevant, since we could no longer pursue the concept in absolute zero!

Just in the fact that matter changes over the course of what we percieve as "time", suggests the concept. This is all relativistic. We can interchange length, height, and width to essentially be one another. The only thing that sets these dimensions apart is our relative position of observation.
So time becomes just the same. It's viewed differently in relation to our respective points in space.
We "travel" through time every day. It's a matter of acceleration/deceleration that affects our points in space/time.
 
  • #64
selfAdjoint
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This is a pretty good insight. There are still in general relativity some distinctions between time and space, but they're much weaker and more contingent than most people would believe. You can do surprising things with coordinate transformations.

The main distinction is that there is a sign difference between the time and the space coordinates. Either time is negative and the three space coordinates positive, or vice versa. Either way is OK, as long as you stay with it consistently in the math. The fact of this means that sometimes "four-dimensional length" aka "separation" can be zero, if the time coordinate exactly balances the three-dimensional space length. This is called a null separation, and the paths that light takes are always null paths.
 
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  • #65
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selfAdjoint said:
This is called a null separation, and the paths that light takes are always null paths.
UNtil they interact with something else? ex: graviton :smile:
 
  • #66
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if e is variable ie" faster than speed of light" what happens to

TIME :surprise:
if some theories of light are saying light can be faster than einsteinian constant :cry:

how would this mathematically for example affect time
given time as function of e
new constants and variables yield new theories :tongue2:
 
  • #67
Where I can find an open windows so i can travell to the future

:confused: I know is way to travell in to the future I just to bussy into my regular life that i cant see it.

I will give away all i am, if i have the chance to travell in to the future and find the anwsers; that all are we looking for.

This is my destiny, my real reason for my to exist

Any one helps or suggestions are wellcome to me...!

Felipe Zerpa
 
  • #68
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What about the TELEPATHING ?? is there any thing that be achived lately apoun human or any other organisms that breath?
 
  • #69
Chronos
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Can't achieve absolute zero in the quantum model. Perhaps in the thermodynamic model. The fact we can get so tantalizingly close parallels how tantalizingly close we can get to accelerating elementary particles to the speed of light. 'Freezing' an electron in it's atomic orbit is equally forbidden. We can extract nearly every bit of energy from any system, just not the very last bit of it.
 
  • #70
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is anyone familiar with superluminal theory

"faster than the speed of light"
a book
details light traveling faster than einsteins c
im sure others are aware of it :zzz: :eek:

:surprise: anyone
 
  • #71
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4)If it were possible to travel in time, THERE WOULD BE time travellers all over the place. Because there are not that means either every sentient being is afraid of time travel to do it, or because it is impossible to begin with anyways.
Perhaps humans don't survive as a species long enough to learn time travel. Maybe there's intelligent life elsewhere in the universe that has discovered a method of time travel, and has simply has not visited this neck of the universe.
 
  • #72
Chronos
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Time travel violates causality. Not to mention that law that forbids creating or destroying matter and energy. If you 'left' this universe you would be in violation. The only way to pull off that crime would be to hide enough 'negative' energy in your suitcase to exactly offset the positive energy you stole. Probably be hard to smuggle that through customs.
 
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