"Time" not a dimension.

[lilphil1989]

From what I've read from there, it seems that atomic clocks were used. So the question is, what if something influences in some way the atomic clock? Isn't that easier to believe than to say that the time itself has been influenced?

It's not that time has been influenced as such (indeed, relativity threw out the concept of "the" time), rather the defintion of simultaneity associated with the rest frame of the moving clock has changed. Remember, one of the important results of special relativity is that there is no such thing as absolute time, and if you and I see two events as simultaneous, then someone in motion relative to us will see one happen before the other.

P.S. As about the idea that time is the 4th dimension, something is odd: all other three dimensions are measurable in meters (not seconds, grams, joules, etc.). You know, if you put a cube in a 3d world, with the margins parallel to the axis, you check its sizes this way: width, in meters, by checking the X axis; height, in meters, by checking the Y axis; and the depth (or how that's called), in meters, by checking the Z axis. They're all measurable in meters, so why should the 4th be measurable in seconds?? Also, what if there are only 3 dimensions? (if so, then perhaps we should not struggle to add a 4th non-meter-measurable dimension).

This is a common misconception. I blame pop-sci authors and their often sloppy explanation of concepts in order to make them "accessible".

No-one is saying that space and time are "the same thing", indeed if that were the case we'd only need one of those words! But, since the Lorentz transforms (the basics objects of special relativity) mix space and time into one another, it is useful conceptually to think of space and time making a four dimensional vector space so that Lorentz transforms can be though of as rotations in this space.
And actually it's quite easy to measure a time interval in metres, just multiply up by the speed of light.