The Nature of Time: Should It Be Considered a 4th Dimension?

[Andrew Mason]

You probably mean to say that [for example]
what may appear to one observer as purely-spatial separation may be seen by another to have, in addition to a [different] spatial separation, a time separation.

Yes. For a purely spatial separation (simultaneous events separated by a distance) in one frame the space-time interval is positive. For events separated only by time, the space-time interval is negative. Since the space-time interval is invariant (same in all frames) a pure spatial separation of events in one frame will appear to be separated in both space and time in all other frames. The spatial separation between such events will always be greater than the distance traveled by light in the time separation between the events.

AM

 

[lalbatros]

Why should time be considered as a 4th dimension?

Just counting: 1 for x, 2 for y, 3 for y, 4 for time.
you don't need more to define the position of a (classical) particle.
But physics needs more information sometimes, like the spin, the charge, the color.
These attributes however can be separated from the 4 spatial coordinates, it seems.

 

[masudr]

But physics needs more information sometimes, like the spin, the charge, the color.
These attributes however can be separated from the 4 spatial coordinates, it seems.

Well for one thing, those other attributes don't take on a continuous range of values and also are specific to certain interactions.

 

[windscar]

Say for instance, I was going to invite you out to the bar, and say all the drinks were on me. Then I decided that as a trick, I would give you the address on a cordinate plane made from the city. To find the location, you would have to figure out were the bar was on this coordinate plane. Well, the city is relativaly flat so that rules out one dimension. And you figure, per say, that it is at X=5 and y=10. You get excited and go there to get your free drinks, but you find out that I am not even there... Likely way for me to get out of it right? No, I just thought you would know it would be tomorrow, but you arrived that night. So, we both where at the same location, but we were there at different times. Therefore, it was the time that separated us, not the space. If two events were not separated in some way, then we would run into each other at the bar at no matter what time we arrived there. It is simply saying that time separates events through some "distance" in order for them not to overlap. So on my cordinate plane, I assumed all events took place the next day, and you assumed all the points on that plane were the points takeing place today. And the difference between those two planes would be a higher dimension of time, that allows both to exist seperatly.

 

[saderlius]

Say for instance, I was going to invite you out to the bar, and say all the drinks were on me. Then I decided that as a trick, I would give you the address on a cordinate plane made from the city. To find the location, you would have to figure out were the bar was on this coordinate plane. Well, the city is relativaly flat so that rules out one dimension. And you figure, per say, that it is at X=5 and y=10. You get excited and go there to get your free drinks, but you find out that I am not even there... Likely way for me to get out of it right? No, I just thought you would know it would be tomorrow, but you arrived that night. So, we both where at the same location, but we were there at different times. Therefore, it was the time that separated us, not the space. If two events were not separated in some way, then we would run into each other at the bar at no matter what time we arrived there. It is simply saying that time separates events through some "distance" in order for them not to overlap. So on my cordinate plane, I assumed all events took place the next day, and you assumed all the points on that plane were the points takeing place today. And the difference between those two planes would be a higher dimension of time, that allows both to exist seperatly.

hrm, a very useful analogy, thanks. I think i understand the practicality involved in the use of time as a "dimension" of a system which allows for separation, just as space is also a dimension which allows for separation of events. This says more to me about a practical perspective of time than it does about the actual nature of time, the latter being more what I'm interested in. But that, as others have said, might be more properly discussed in a philosophy forum.
said,
sad

 

[windscar]

hrm, a very useful analogy, thanks. I think i understand the practicality involved in the use of time as a "dimension" of a system which allows for separation, just as space is also a dimension which allows for separation of events. This says more to me about a practical perspective of time than it does about the actual nature of time, the latter being more what I'm interested in. But that, as others have said, might be more properly discussed in a philosophy forum.
said,
sad

Your welcome and your right. The true nature of time would be better discussed in a philosophy forum, because there really isn't anything in physics that tells about about the true nature of time. It is like the bull in the china shop analogy. You know that if a raging bull goes in it is going to destroy everything in the shop until there is nothing left in one peice, but according to the laws of physics time should be able to run equally in both directions. So why don't you ever see bull's comeing out of destroyed china shops backwards with everything in tack? The problem is that, there is nothing to show times arrow, that events pass by only one way forward in time. The Arrow of Time is an all right book, and I suggest reading it if you want to gain more insight about time itself and how it is used in physics and some of the problems faced with it and times arrow.