There are several arrows of time, One is thermodynamic, another associated with the expansion of this Universe.
I actually have an intuition that time is somehow related to the expansion of the universe. I suspect that the ENTIRE universe is expanding--not just space but everything it contains. This includes matter and all the objects it makes (you and me included). This expansion is imperceptible on the small scale because we are more or less expanding simultaneously. After all, if you were in a room and growing and everyone in the room AND the room itself were growing at about the same rate and you had no standard reference for scale, how would you ever perceive you were growing?
The reason that the expansion of space can be detected is because of gravity. Objects made of matter expand more slowly due to the gravitational fields they create. "Empty" space expands at a quicker rate than, say, a planet does. This is also demonstrated by experiments that indicate time "moves" more quickly in low gravity environment and is "slower" in a heavy gravity environment. I think if it were possible to place a measuring device in intergalactic space far from any strong gravity fields, you'd see it measuring the passage of time as faster than on Earth. This may have a related aspect to the idea that time passes more "slowly" at near relativistic speeds based on the idea that the inherent inertia of an object moving at such a velocity (approaching "infinite mass) creates an artificial "gravity field". Not a true gravity field, mind you, but inertia interferes with the expansion of an object and thus "pulls it out" of "normal" time.
It's a wacky idea, I know, but one I find intriguing on occasion. I can't feature how, even if this WERE true, that one could use it to travel BACKWARD in time--but if one were to do so, you might find yourself unexpectedly BIGGER than you would anticipate as the universe and everything in it was literally a smaller place in the "past". Of course, the further "back" you went in time, the LARGER you would be relative to your surroundings, so watch those ceilings, folks.
Question though: If your speculation is correct; IF the Un iverse ever started to contract; does that mean (in effect), objects would start moving backward throgh time (eg. the
Bejamin Button effect)?
It seems a reasonable extrapolation. The question then, of course, becomes how would our awareness be effected? Would we be conscious of impending events because they would have already "happened" and be able to anticipate them (foretelling the "past"?)? Would we (and events) simply run in reverse like a film playing backwards? Or, finally, would there simply be a whole new series of episodes played out in a universe where time-based reactions (chemical, nuclear etc) run in reverse (bombs "unexplode" for example) but a different "events" occur within the limitations of these "reverse" laws of physics?
If one accepts that "time" is a dimension and movement along a given axis is equal to movement in that dimension, then there must be some kind of "movement" along the axis of "time" for it to function anything like the first three dimensions (length, width and height). The "direction" of the axis of those three dimensions is readily perceptible in our eyes. Physical motion equates to "movement" along these dimensions. Those same characteristic, length, width and height, along with the characteristic of "duration" from time, allow an object to physically exist in our universe. They give an object "presence" and an object exists with length, width and height without necessarily MOVING through to dimensions, but it is movement through those dimensions relative to a fixed point that we can calculate the measure of that "presence" Similarly, with time, we count "duration" relative to an established fixed measure ( a moment, a day, a year etc). But separate from the first three dimensions, "time" appears to be unique in that is is the sole dimension that we can:
A: move only one direction in and
B: APPARENTLY we move through without the component of physical change of location; a requirement for movement in the first three dimensions.
YET, movement in time is IMPACTED by influences which ALSO effect physical movement through space. Gravity, for example, limits the ability to move along the dimension of "height" (the definition of "height" being the angle perpendicular to the source of the gravitational field). Time "moves" more slowly relative to the proximity to a gravity field. I've read that time may actually HALT at the event horizon of a black hole. Still, the more distant one moves from a source of gravity, the weaker the influence of that gravity field and the "faster" time moves. Thus gravity actually effects our movement along TWO dimensions--height and "time".
When one approaches relativistic speeds, "time" slows for the travelers relative to outside observers. In this regard, perhaps INERTIA performs the same inhibiting mechanism as gravity but along a different axis line--one opposite to the angle of trajectory of the traveler and thus retarding "movement" along the dimension of "time".
The first three dimensions are impacted and influenced by physical movement. So, we see time is ALSO effected by influences which impact physical movement along these same dimensions. How then, if physical movement is required to travel along the dimension of time, could we be "moving" and not know it?
We know the universe is expanding. Perhaps the dimension of "time", unlike the first three dimensions, is composed not of just ONE angle of travel, but 360 degrees of angles, moving outward in all directions simultaneously from the center or focus of the LOCAL gravity field. All objects with mass generate their own gravity, even my own body. If I am "expanding" from my "center of gravity" I AM moving, physically and thus I am also "moving" along the axis of the dimension of "time". BUT, if everything I can reference around me is ALSO "expanding" (including "empty" space), my "movement" would be imperceptible to me. I can't even measure it because all my MEASURING tools are ALSO expanding at roughly the same rate. BTW Let's also not forget that the dimensions of length, width and height are ALSO measured based, essentially on the center of any object's physical presence.
Only when we look at great areas of deep space where the is VERY little gravity to retard both the expansion AND movement through time, can we see the difference. Conversely, in a black hole, the most intense of gravitational fields, movement along ALL four dimensions is severely restricted. And, quite the opposite of "expanding", the example of a singularity become the smallest and most COMPACT structure we know. It is infinitely small, thus having no true width, height or length, and "time" ceases forward movement at the event horizon. ALL four verifiable and known dimensions are "locked down".
How ANY of this would lead to an ability to travel backward in time, I have no idea. It might be as simple as selecting the right angle of travel relative to a strong gravitational field or inertial influence.
