Is this a disproof for time travel?

Question

I've been reading and thinking about time travel a lot lately. I'm pretty sure it's impossible, at least time travel to the past. Here's my (dis)proof:

All of the variables below are vectors. This means that they are an amount and a direction. For example, if you're going to define a positive velocity as traveling North, then a negative velocity would be traveling South (the opposite direction).

It's a fact that Velocity = change in distance / Change in time

Let's solve this equation for time.

v = d/t
tv = d (cross multiplication)
tv/v = d/v
t = d/v

Now, I want the time to be negative, to signify a negative change in time, or... reversing time.

-t = -d/v

What this equation is saying is that in order for time to go backwards, distance and velocity need to be going in opposite directions.

For example:

Imagine going 30 mph North, but you're actually moving South. Makes no sense? Exactly.

Let's examine another equation.

It is a fact that acceleration = change in velocity / change in time (a = v/t)

Solved for time that's:

t = v/a

Let's make that negative:

-t = -v/a

So, imagine you're accelerating in one direction, but your speed is increasing in the other. Again, this makes no sense.

Last equation.

It is a fact, under Newton's second law, that Force = mass times the acceleration on the object that the force is being applied to.

F = ma

Acceleration is v/t

F = (mv)/t
Ft = mv
t = (mv)/F
-t = (mv)/-F

In other words: Imagine pushing a box North, but it actually moves South. That is all it would take to travel into the past. Easy, right?

Some may say an error in my logic is that numbers and math were made by man. I argue that man did not created by man, they were discovered. If man created math, who was the asshole that decided that pi should be irrational?

some may argue that all the equations I used were "High School" Physics and math. This may be true, but I guarantee similar results for any level of equation

So is time travel impossible? I definitely believe that travel into the past is impossible. And we all travel into the future. We do it one moment at a time. I think that's as fast as it'll go.

The the person who answered:

That's my whole point!

Answer 1

It's a nice thought, but it doesn't hold up. First and foremost, it makes no since to divide by a vector. You can only divide by the magnitude of a vector.

I came up with a lot of reasons this doesn't hold (sorry), bt perhaps the simplest to explain is the following.

Velocity and displacement don't have to point in the same direction. Think of riding on a ferris wheel. You started the ride at the bottom. If we can "freeze" time at the moment you are at the top, your displacement vector is pointing straight up. However, your velocity vector is directly in front of you. In other words, the two are at 90º.

There are many other reasons this doesn't hold. But time is an interesting subject to think about. And I'm sure there's plenty of time to continue to think about it :D


EDIT:

t is not a vector, so it does not have a direction. Your argument relies on treating t as if it has a direction. The t in our equations doesn't represent the flow of time. It represents an instant during a particular situation. Negative time implies what happened BEFORE we started the clock.


EDIT #2:
More thought into this :D

d = v/t is only true for linear displacement. The actual definition, if we are concerned with vectors, is

v = dx/dt

In other words, velocity is the derivative of displacement. In fact, the only time they point in the same direction is if we are looking in one dimension.

Answer 2

d = vt is true, but you've misinterpreted the t. t is not a vector, it is an interval. When we write t = 2 sec, for example, we are actually saying t = del(t) = t1 - t0 and t1 >= t0 always. There is no direction implied, time interval is a scalar that is always increasing.

The only vectors in d = vt are d and v. When you divide d/v, you will also reduce the results to a scalar because both d and v have the same direction. Thus, again, d/v = t = scalar.

Thus, when multiplying d/v by minus one to get -d/v = -t, we are violating the vector requirement that both d and v are traveling in the same direction. That is, we can't change directions (d) without also changing the velocity (v). This is clear through -d = -vt; so that -d/-v = d/v = t.

Sorry, we can't reverse time, but not for the reasons you cite.

Answer 3

OK then , what about negative frequency...
Since t=1/f then f=1/t
Apply your equations to 1/f instead of t for a negative frequency:

http://ccrma.stanford.edu/~jos/mdft/Positive_Negative_Frequencies.html

Time as we know it in our 3d space 1d time (4d total) universe goes from past to future, BUT it is not linear, it is affected by mass.

Imagine living in 2d space and 1d time (3d total) we could travel in flat geometrical directions, and even if that flat universe was of a spherical shape, we would not know because we would be confined to a plane surface, not knowing depth.
We would use the number pie to measure circles, but not volumes because volume would not exist in that universe, even though the very shape of is was a volume, (remember we would only live in 2d space on its surface).

Now imagine a universe like ours with 4 d space, where we could move in 2 different directions at the same time!

You cant prove time travel is impossible!
Nothing is impossible;)

Answer 4

It's a logical point that you make. I think that time travel is impossible as well. I guess that basically Einstein theorized that if you could travel faster than the speed of light, you'd actually move backward along the spacetime "continuum". If it were possible to travel faster than light-speed, the only thing that might change is your PERCEPTION of time, not time itself. It used to be accepted that time is the only constant, but the theory of relativity goes contrary to that assumption. I think time actually IS a constant, so even if your perception of time was accepted by your mind as standing still, or even moving backwards, time would continue to march right along despite your perception of it. No, I'm not able to theorize any of this based on mathematic formulas, I just try to approach it with common sense.

Answer 5

time cannot be given a positive or negative reference. Time is always positive. u say that -t= -d/v but can u physically move back time? no you cant. say that u are standing at a door that goes into you room. if you move forward its positive and move back its negative. if u move back you are physically going a negative direction( reference is the door, at 0) or if you move forward you move a positive direction. same logic with velocity and acceleration.