Here's my 2 pence.

We as a race, know speed of light to be 'top speed'.

However, for that to exist, there has to exist another speed above it. Right? The same applied to temperature, absolute zero is actually 1 degree above the lowest temperature on the scale. (correct me if I'm wrong, I'm most talking in theory from here on in, because I like to do this stuff).

Assuming that the speed of light is 'max speed'.

If we traveled at the speed of light, we'd theoretically have a delay. For instance, light takes years to hit earth from stars. It has a speed, it is measurable.

These guys are moving something 'instantly'. This means that it has a time delay from A to B of precisely 0 seconds.

The theoretically means it doesn't travel. For it not to travel we must assume 2 things

1. It moves faster than the speed of light.
2. It can be in 2 places at the same time.

1. Is obvious. I will explain further on 2.

For something to be at place A then at place B zero seconds later is physically impossible according to the laws of physics. The same 1 object can not exist in two places. However, in the laws of time, if it is one thirty one and zero seconds, then 0 seconds pass it is still 'the same time' one thirty one and zero seconds.

So, therefore, as the object moved in 0 seconds, it's has to be at it's original place at the same time as it is in it's new place - as objects have to physically move, this is impossible. Assume that the "have" in the sentence "object have to physically move" is true.

As such, if these guys are doing what they say they are doing - everything we know about physics is false.

Now, referring back to my starting point (don't you love it when this comes together)

For travel at 0 seconds of time passing to exist, there must actually be a 'travel at -1 seconds of time' in existence. Something we will probably never achieve in our next set of generations (remember, these guys might be teleporting something, but it's only a very, very small object, a person would be an entirely different issue.)

If you accelerated at -1 second of time - every second you'd gain another -1 second. Right? (Remember acceleration is different to movement, acceleration is the rate at which you increase)

Thus, traveling back in time is possible. But traveling forward in time, is not, as time is infinite and no matter how fast we were to accelerate, about the best we could catch is a glimpse of 'old light' that you've overtaken by moving fast than it - which would give the illusion of backwards time travel, not forwards!

Now, just one more thing I'd like to say is my 'theory' on impossible.

For something to be definite, it must be defined, infinitely. Right? So, people who say 'it's impossible for x to happen' are incorrect, as time lasts forever. The only way for something to truly be impossible is for it to not happen between the start of time, and the end of time. But time doesn't end. Understand?