Is Time Travel Just a Concept?

[MadIce]

There seem to be 3 views of time. In presentism only temporally present objects are real. The past no longer exists and the future does not exist yet. Obviously in that view there will not be any time travel. In possibilism (sometimes called the "growing block" or "growing universe") the past and the present are fixed and actual and the future does not exist yet. In eternalism time is a fourth dimension and past, present and future are actual. That's the most likely candidate to use for time travel. Believing in the others limits the possibility of time travel or makes it impossible in that model. But that belief does not prove it is impossible altogether.

 

[sarephina]

Is color a dimension, too? Brightness?

Of course... many things can be concepts...
concept n : an abstract or general idea inferred or derived from specific instances.

 

[Allah]

no, because you cannot mathematically describe an object as blue.
But you can say, for example, that an object is 3 units wide, 4 units long, 5 units high and moving along the line y=x at a velocity of 5 units/sec at t=6seconds. Color and brightness are irrelavent.

 

[MadIce]

Color is a concept which can be described by physics as a light wave. That does not make it a dimension. But there is no need to descibe it that way.

Electromagnetic radiation is a mixture of radiation of different wavelengths and intensities. When this radiation has a wavelength inside the human visibility range (approximately from 380 nm to 740 nm), it is called light. The light's spectrum records each wavelength's intensity. The full spectrum of the incoming radiation from an object determines the visual appearance of that object, including its perceived color.

You are free what to believe, but the fact that you feel time is not a dimension, doesn't prove anything. So, thanks for sharing you don't believe in time travel. ;) It doesn't help much, because science continues to make advantages in that field anyway.

Allah: Even color has solid physics theories and laws. Have a look at Color. And about its maths: Color can be mathematically decribed in the wave equation.

 

[Allah]

I know, but my point is that if a block is blue or red does not matter when you describe it mathematically.

 

[ninja nemesi$]

Forgot who it was, but somebody said that it wazs not possible to travel through time because you can't travel -2metres through any of the other 3-Dimensions...yes you can. Stand in your place, and step backwards two metres. If your starting point was at the 3D co-ordinates (0, 0, 0) then after you finish moving, you would be at co-ordinates (-2, 0, 0) .

And i believe that traveling into the future is not possible, simply because we do not know how it will be. If i sit here, in this room and contemplate the theory of time, then in 50 years our world could be described as x .
But what if i want to go out now grab a few lumps of purified uranium and smash them against each other in my kitchen and cause a nuclear explosion. Then in 50 years time our world could be described as xy + x(z +zy) - x^2) . And, by process of observation and a conclusion involving the use of common sense, we can conclude that the two worlds are different to each other.

So then we do create a time travel machine, and we travel into the future-where would i arrive at...? Would i be in the world described as x, or in world described as xy + x(z + zy) - x^2) ?

Point is, we don't know what the future will hold, and only the divine creator himself does (I won't bring any more religion into this...).

As for traveling back in time-I think our best bet is through naturcal wormholes created by the warping, stretching or tearing of the fabric of space (see string theory for more info...)Thats the most convincing theory I've seen so far on the matter.

 

[meteor]

according to QED, positrons and the other antiparticles are just particles traveling backwards in time; a positron is an electron traveling backwards in time. You realize it viewing a Feynman diagram: its horizontal axis represent space and its vertical axis time. Take a look at the book "QED, the strange theory of light and matter". It's an interesting reading and you will see paths of electrons moving backwards in time. Each segment of the path of an electron in a Feynman diagram is called a probability amplitude, and there are probability amplitudes that point backwards in time: in fact if you have an electron you can't predict if it is going to go backwards in time: you can only calculate the probability, that is equal to the square of the length of the probability amplitude.

 

[sarephina]

Saying that present events will affect future events is also saying that events take place in a linear fashion.

If we are able to travel through time at all, I think that suggests some degree of constancy in the course that events take.

In the three dimensions that we can definitely agree do exist, we can still travel through change.

 

[Prometheus]

Of course time travel is possible. It is unavoidable.

When you first made your posting, my reply was in your future. Yet, now you have traveled into your future, such that you can now read my reply to your post.

 

[ninja nemesi$]

But if shadowman hadnt created this thread in the first place, what would you have had to reply to...? There would be no thread for you top reply to, thus past events do effect current events.


I'm not saying it's impossible. I don't like saying anything is impossible. I'm saying that if we were to travel into the future, where would we end up?

Another conclusion i think i just reached...that any event is never certain, nor impossible-there is only a certain probability between 0.0 and 1.0 that any event will occur-----> Quantam Mechanics

 

[Prometheus]

n_n,

You seem to be saying that we cannot travel into the future because it is as yet indeterminate. I contend that this does not hold.

There will be a tomorrow. It is not significant what tomorrow will be for us to recognize that we will eventually arrive there, and that it is currently in our future.

Furthermore, modern physics recognizes that you and I need not pass through the same amount of time between now and then. In other words, it is possible for me to travel less far through time than you during the next 24 hours. Therefore, I can travel not only into my future, but I can travel more slowly than you into your future as well.

 

[ninja nemesi$]

...?
i don't get it...

 

[Prometheus]

n_n

Time travel into the future is clearly possible. Everyone does it every day.

Time travel into the past is not possible.

 

[MadIce]

Time travel into the future is clearly possible. Everyone does it every day.

Time travel into the past is not possible.

Bull. Because you say so?

 

[Prometheus]

I am sorry. Is there a question in here somewhere?

 

[ninja nemesi$]

obviously time travel is possible-we do it everyday, no doubting that

But what makes it possible to accelerate our travel through this dimension?

 

[Prometheus]

n_n,

Instead of accelerate, consider just the opposite, that it is possible to decelerate our motion through time with respect to others.

Are you aware of the idea that the speed of light is constant in space-time. Space-time is a symmetrical interaction of space and time. The greater the rate of motion through one, the less the rate of motion through the other.

The best known example is probably that of two twins, one of whom boards a spaceship that accelerates to near the (Newtonian) speed of light. When he returns to earth, he will find that his greater rate of motion through space has caused him to age less than the twin who remained back on the earth.

Therefore, if one were to board a spaceship and travel near the (Newtonian) speed of light, and then come back after everyone on Earth had aged 100 Earth years, then the person will have aged almost not at all, and so will have effectively moved 100 years into the future. (It is not possible to return, however.)

By moving into the future more slowly than someone else, it is possible to move into the future with respect to him. Rather than accelerate through time, as you suggest, it is possible to decelerate through time with respect to the Earth and others on it.

Lest you consider that this is a hypothetical example that relates to motion at the (Newtonian) speed of light only, keep in mind that this is only a blatant example. No 2 people move forward through time at the exact same rate. We all move into the future, and we all move into the future at different rates of speed.

If you are familiar with Newtonian physics, but not with Einsteinian physics, then this will understandably have little meaning to you.

 

[Allah]

I believe that time travel is possible

1. Moving faster than the speed of light. If you somehow do so, then you will go back in time.

2. Entering a Wormhole, since wormholes traverse space and time. I think I heard somewhere that wormholes have actually been observed on the microscopic level, but I don't remember where.

3. Sending your mind across time while your body sits in a nice air conditioned room. If you did this, then you would avoid all of the ugly paradoxes that arise by going back in time.

 

[sarephina]

With respect to others.

There was an experiment of which results proved light traveled at a constant speed no matter how fast the source of light was travelling, right? Did that come before or after Einstein's theory of relativity? And how do we know our technology is advanced enough to detect any change in the speed of light?

What is the difference between Newtonian and Einsteinian speeds of light?

With respect to others. This has probably been asked countless times, but I haven't had my turn. So 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 traveling near the speed of light, so he should age and they should not.

--
again, the present may affect the future, but that doesn't preclude our ability to accelerate into the future anyway--if time is indeed a dimension like the three we all know and love. A changing landscape (dimension) can still be travelled.

 

[Allah]

Time dilation

http://physics.about.com/cs/generalrelativit1/a/110703_2.htm?terms=relative+time

 

[Prometheus]

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.

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 traveling 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 spaceship underwent accelearation with respect to the other, and this is the critical factor.

 

[sarephina]

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 spaceship 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?

 

[Prometheus]

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

Case 2: The entire universe accelerated, but the spaceship 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 spaceship to accelerate with it as well. This is due to gravity. Yet, the spaceship 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 spaceship accelerated.

 

[selfAdjoint]

But wrt the spaceship twin, didn't the rest of the world accelerate while he remained still?

Unlike velocity, acceleration is not relative.

 

[RAD4921]

Time trqavel is inevitable

We are all traveling through time while sitting in our chairs (into the future)

 

[sarephina]

hehehe world, universe... big difference...

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?

 

[automaton]

check out my other post
faster than the speed of light

if you read it
or already have data

any ideas
lemme know
thanx

 

[bull34]

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.

 

[catch.yossarian]

Time travel is impossible. 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 doesn't 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?

 

[Allah]

shadowman, you are not thinking 4th dimensionally