Subject:  Re: a simple question
Date:  Tue, 29 Sep 1998 16:37:01 EDT
From:  "chad hadsell"

I was always under the impression that time is not so concrete in its existence as, say, CFC's are. I've always viewed time as a perception thing.  Thus, when one says "wow, time really flew by this week!" it actually did, for that person. Time is an arbitrary measurement of progress created by the human mind.  Therefore i guess a better question than my previous one would be if time travel is even possible. Can you travel through something that exists only in your mind?  If you can, it seems that it would only affect you, no?  I have read a great deal of sci-fi based on the concept of time travel, and though it makes for very interesting plots, when it comes down to the root of things, i don't believe that you can travel backward or forward in time.  All you can do it reverse progress.  It would be akin to "unbaking" a cake.  Of course, travel to the future is absolutley rediculous.  The very act of traveling to the future changes the *future*.  Next time you "go back to" the same "time" in the future, it would be different.  Every action that occurs right now changes how progress occurs, and therefore also changes what is commonly called the future.  I guess the key to the whole thing here is that only the "now" exists. There is no such thing as the future yet, and when it occurs, it instantly becomes the now.  There is no longer such a thing as the past, as it no longer is the now.  Some may say that this is a limited perception of things.  But when you really start to think about it, i don't believe it is any more limited than the notion that, since we can move through space it must follow that we can move through time in the same manner.  Time is niether linear nore "spacial" but rather exists at a single point.  it is not the 4th dimension, but rather the 0th.  Does this make any sense to you?  its hard to talk about this concept with such limited terms as language provides.  tell me your thoughts on this.

--chad

Chad--

Your "simple question" has become much more complicated.  Now we are beginning to examine the concrete and the abstract, the objective and the subjective--many concepts which are difficult even for graduate philosphy majors.  But let me tackle what I can.

First, I want to distinguish three ideas about time.  There is the reality of time, the measurement of that reality, and the subjective experience of it.  To explain what I mean, I'm going to have to talk about distance.

There is a grocery store not far from my house; it is just about a mile from here; it could also be said to be about 2 kilometers from here.  Now, I don't know for certain the exact distance--but there is an exact distance.  But the significant thing here is that the distance is a real and fixed thing, whether or not it has ever been measured, and whether or not any of us know that distance.  Even if the concept of distance was unknown to us--say, if we were dogs or wolves--there would be a real distance between my house and the store.

The measurement of that distance is an abstraction.  We've invented units of distance, and we use those units to define space.  Thus I can tell you that the distance to the store is about a mile, and you know what that means--you can think of two places which are about a mile apart, and so know how far I am from the store by that comparison.  But the unit--the mile--is not the reality; it is the measurement of the reality, defined by the symbols we call language.  Yet the unit is very valuable, because it gives us a way to determine the distance objectively, that is, to give the distance a value which is not affected by anything other than the real distance between the two points.

But if I walk to the store with $50 in my pocket, and spend it on groceries, and then I carry those groceries home, I would tell you that the distance from my house to the store is not as far as the distance from the store to my house.  Similarly, if I drive to the store, it doesn't seem nearly as far from home as it does when I walk.  My perception of distance is extremely subjective; if I'm not counting paces, or using measuring devices of some sort, it is very difficult for me to know how far things are from each other in any objective way.

Now, if time is a dimension, then it would be logical to assume that it is similar to the other dimensions.  Thus we have our subjective perception of time--it may seem to move faster or slower, in the same way that two points may seem farther apart or nearer together.  Yet we have invented units by which to measure it--seconds, minutes, hours, days, weeks, months, years, decades, centuries, millennia--and we can observe that there is a concrete value--the number of seconds in a day is consistent; however we experience the day subjectively, objectively, it is always the same--just as the distance between my house and the store is always a mile, whether I walk or drive.  I am reminded of Commander Data on Star Trek (Next Generation) boiling water to test the notion that "a watched pot never boils", that the subjective experience of time is affected by our expectations, and finding that his internal chronometer always measures the time the same whether he is watching it patiently or occupied in other things--because his subjective experience of time is limited by the objective reality of a built-in clock.  For the rest of us, waiting for water to boil takes a long time, unless we have been distracted by something else.  And finally, real time exists whether or not we have the ability to measure it--I do not know how many days existed before men invented hours, but time existed before we were able to measure it; and as we study the past, we often count the millennia which existed before anyone measured them.

But perhaps I have begged the question--for you've challenged whether time is a dimension at all.  Although it is very different from space, I would maintain that it is a dimension, and I think I can demonstrate it with a series of illustrative steps.

Let us agree that two physical objects cannot exist at the same dimensional point; but let us postulate two objects, and examine what it means to say that they cannot be in the same place.

Let us reduce all of space to a single dimension--a line.  To make it easier to contemplate, we will make this abstraction a number line--it has no height or width or depth, but is merely infinitely long, measured by regular units of distance abstractly representing numbers.  Let us place one of our objects at "1".  Since the other object cannot be in the same place, it cannot also be at "1" on that line.  Yet I can place both objects at "1" if I change one of the rules:  I will create a second dimension.  Now the entire universe appears as a graph; the original line is the X axis, but the Y axis represents our second dimension.  Now I can place both objects in the same place in that first dimension by placing them at different places in the other--that is (using the standard notation of (x, y) to represent the position of a point on the graph), our first object can be at (1, 0) and our second object at (1, 1).  In relation to one dimension--the X axis--they are in the same place, at "1"; they may be so because in our second dimension they are not.

It is a simple step to point out that the objects cannot be in the same place in both dimensions--both objects cannot be at (1, 0).  Yet, just as simply, we can move from the imagined two-dimensional world of the graph into the reality of three-dimensional space.  Three-dimensional space is generally represented by adding a Z axis to the graph, representing distance above and below the plane of the two-dimensional graph.  Suddenly it becomes possible for two, three, or a million objects to exist at the coordinates (1, 0) in relation to two dimensional space, because they can exist at different points on the Z axis--(1, 0, 0), (1, 0, 1), (1, 0, 2), and on.

This may seem very abstract; let me make it concrete.  I have placed a book on my desk; it is on the surface of my desk, three inches from the near edge and five inches from the right end.  If I place a similar book on top of the first, it will still be on my desk three inches from the near edge and five inches from the right end.  I can place a great number of books, one on top of the other, and they will all be in exactly the same place on the desk, distinguished only by their distance above the desk.  Thus were I to send you to get one of those books, I would tell you that it was on the right end by the near edge of the desk--and you would know when you saw the desk that it was in that stack.  The books are in the same place in two dimensions because they are in a different place in the third dimension.

But I can put two objects, two books, in the same place in all three dimensions--three inches from the near edge, five inches from the right end, zero inches from the surface--in seeming violation of our statement that two objects cannot occupy the same space.  The discussion which has brought us here suggests that I can do so if I can create a fourth dimension; I cannot create a fourth spatial dimension, but I can take advantage of the fourth dimension which does exist:  I can place the first book on my desk, then remove it and place the second book there.  They now occupy the same space in three dimensions, distinguished by the time at which they occupied them.

This is an extremely simplistic way of looking at the dimension of time; Einstein's theory of relativity demonstrates the aspect of time as a dimension in ways which to most of us seem counter-intuitive--that is, exactly opposite of what we would expect.  The relationship between movement through space and movement through time becomes extremely complicated; yet lasers, atomic bombs, nuclear reactors, and particle accelerators all work because Einstein was right about time and space, energy and matter.

So time exists in reality; it is perceived and defined by the mind--just as space, matter, and energy are only known to us by our perceptions, but do have real existence.

You suggest that only "now" exists, because only "now" is known to us.  But consider whether that is true otherwise.  Does the store up the road exist when I am not there?  Do the people on the Internet exist when they are not talking to you?  Do your parents exist when you are away at school?  (You had better hope they do when you write home for money!)  That's different, you say, because in fact you could go to where they are.  But if you were a quadriplegic, confined to a bed in a room, unable to talk or operate a communications device, would the rest of the world cease to exist when it was no longer possible for you to experience it?  I think not.  In the same way, I don't believe that the future and the past could be said not to exist merely because we cannot experience them.  I'm not sure that either of them do exist, in that sense--but the past did exist, and the future will (probably) exist; and I am not prepared to suggest that they cannot exist concurrently with the present in some non-temporal sense.

You have confused something:  you suggest that it is not possible to travel to the future, because you would change the future.  Travel to the future is no problem.  There have been a number of sci-fi stories based on the idea that someone would "travel to the future" by somehow being placed in some type of suspended animation and subsequently revived--Buck Rogers was one of the first of these, a pilot whose life was saved by an experimental survival system, but who was lost for five centuries, revived in the future.  That is not what we mean by traveling to the future--but in fact its effect on the future is no different.  Traveling into the future is no different from taking a vacation in Boston for a period of time, but that you don't age.  It is travel to the past which causes the problem--even if that travel to the past is a misguided effort to "correct" travel to the future.  (Caveat:  if someone from the future reaches back into the past and snatches you into the future, that involves a type of travel to the past--someone from the future is interfering with the past; if you on your own initiative unaided by anyone or anything from the future travel to the future, that is not much different from Rip Van Winkle's nap--you left, the world went on without you, you came back.)

I hope this clears up a few thing.  Let me know if all this makes sense, and I'll be glad to try to clear up anything else.  Whether it will ever be possible to travel through time from a technological perspective seems to me doubtful; but I believe that there is no philosophical aspect to the matter which would make it impossible.

Thanks for your note.