Does time flow backwards of forwards?

[Whovian]

My laptop has the ability to run at different speeds (to prolong battery life). The programs running on it don't know what speed they are running at. I can even put the laptop in standby and bring the programs to a halt, which they are also completely unaware. Then when I power up the laptop again, the programs pick up where they left off and again, they are unaware and produce exactly the same results as if I had never slowed or stopped the system. But I cannot make the laptop run backwards. That doesn't make any sense. There is no way that anyone can construct a computer that allows programs to run backwards.

I never said that. You may have been misinterpreting what I was saying. Sort of what I was arguing is that time flowing backwards wouldn't even have any meaning, since it wouldn't be verifiable at all. May have phrased that badly, I'm always doing that.

There are many discussions about the flow of time but when Einstein made the simple definition that time is what a clock measures and since all clocks run forward, there is no place in the context of Special Relativity to be speculating about time stopping or going backwards.

Again, never said that there would be any two frames of reference that would be flowing backwards from each others' point of view.

 

[evilatom]

It's so cool I stumbled across this thread because that's something I think about a lot. If that were the case and time is moving backwards through us than wouldn't choice be an allusion. It would very much seem like were making decisions that alter what happens next but really were just waiting while what's already been reaches us. Or would our actions ripple forward through the stream and change it before we catch up. Or is there no perceivable future or past at all and the only events that do occur to us are where we intersect the stream in the present like a magnet moving over a row of paper clips just close enough to make them move slightly before it passes on.

 

[Drakkith]

It's so cool I stumbled across this thread because that's something I think about a lot. If that were the case and time is moving backwards through us than wouldn't choice be an allusion. It would very much seem like were making decisions that alter what happens next but really were just waiting while what's already been reaches us. Or would our actions ripple forward through the stream and change it before we catch up. Or is there no perceivable future or past at all and the only events that do occur to us are where we intersect the stream in the present like a magnet moving over a row of paper clips just close enough to make them move slightly before it passes on.

Speculation on time is mostly pointless. The fact of the matter is that time is treated as another mathematical dimension in science to separate events similar to distance. Asking what would happen if time flows backwards is like asking what would happen if forwards were backwards and upside down. It isn't so we can't say how it would be. Time is not flowing and it is not a stream any more than distance is.

 

[arindamsinha]

If we watch a ticking clock we would come to the conclusion that time flows forwards because we see time progressing one tick at a time. One, two, three, four, time must flow forward because things change and progress from one state to another. We know for us time only flows in one direction, it doesn't switch it up and change its mind, what is done is done and it's irreversable. However if time flowed backwards the same would be true, things would change and progress from one state to another, four, three, two, one.

Say for example, if we were standing in the street on a windy day we would find millions of particles of gas whooshing past. In relativistic terms both us and the gas are moving, in one frame of reference we are moving through the stationary gas, however in another frame of reference the moving gas is whooshing past our stationary bodies. Can we apply the same comparisons to the flow of time as we do the flow of the wind? On one hand we observe time to progress forwards, but we our selves don't move backwards in time, we move forwards in time, so if we were to examine time relative to our frame of reference, wouldn't we conclude that time actually flows backwards instead of forwards? We and time couldn't be moving in the same direction because then time would be standing still, everything would be at rest, but we know that isn't the case. We have to flow through time just as time has to flow passed us in order for the universe to exist, otherwise we'd never get from A to B.

Us >>>>> Time
Time <<<<< Us

Interesting question.

My thoughts on this:
We can't treat time as a 'flowing' phenomenon like a river flowing, but we can look at time 'flowing' in a 'forward' (purely conventional) direction based on causality.

Something like a river flows w.r.t. some reference frame. If we are sitting on the banks of the river, it flows in a particular direction w.r.t. the material making up the banks (and us). If we are speeding in a fast boat downriver, we could consider that the river is flowing 'backwards'.

With time, we don't have this luxury of comparison w.r.t 'something else that was not moving'. If we choose a really small slice of time at any point, we may even consider that time 'is standing still' at that moment, as nothing is changing (i.e. no noticeable events are happening).

The 'flow' of time needs to be seen as a succession of 'events', with the order being established only by a rule of causality. An event A which causes another event B to happen establishes that event A happened 'earlier', and therefore time is flowing forward (conventionally) from event A to event B. No amount of logic will allow event B to precede event A (i.e. time to flow backwards).

The only way I think we (as observers) can see 'time flowing backwards' would be like this:

• All the energy and matter of the Universe suddenly reverse course, and start retracing the steps they had taken w.r.t. all other energy and matter in the Universe (like rewinding a movie). For examples, at an atomic level, electrons moving in a particular direction w.r.t. the nucleus in an atom reverse course and start moving backwards, and so on at every level.
• We (the observers) ourselves, somehow fortunately get detached from this Universal energy/matter movement reversal (being somewhere deep in space and strangely not affected by anything else happening in the Universe). The atoms within our bodies carry on towards the future (or forward direction of time).
• Even this would have challenges, as we have withdrawn from the rest of the Universe at least the atoms that got into our body during the last meal, so the rest of the Universe would never be the same again, no matter how diligently it reverses course.

Given this, we need to consider that time does not really 'flow' in the sense of moving w.r.t. anything else in the Universe, except for comparison of the occurrence of certain events before and after other events (i.e. causality).

 

[bahamagreen]

Is it OK for me to be irritated that the OP's original question is not even being grasped yet?

He is not asking about time going backwards like a clock hand going counterclockwise, nor the concept of existential time "flow" being the reverse of our usual causality.

The title should have been "Does time flow backwards or forwards with respect to us in the present?"

He is noting the relativity of ordinary motion and observing that the common sense notion is that we seem to progress forward through time, yet we also use common language to describe the progression of time as also going forward... two things going forward at the same rate - where is the net difference that is supposed to be the "movement" through time?

From a kind of relativistic perspective, if we hold ourselves "at rest", time clearly "moves" with respect to us, into the past... the world seems to become "unchangeable" in the present and gets woven into a hard and fixed history that is laid out "behind us".

To use the loose words; if we are moving forward in time, then time must be still or moving backwards, or moving forward not as fast as us; or if we are still, time must be moving backwards... or any other combination that makes the relative difference in the speed of us and the speed of time result in the relative speed and direction we observe between us and time.

At first this may seems to require a higher level of "background time" against which to compare the movements and directions of time and ourselves, but this is why the OP mentioned relativity - suggesting the solution of avoiding the absolute motion problem using frames of reference.
The OP is posing a similar abstraction to time by seriously apply a concept from relativity - assigning a frame to us and a frame to time, and looking at how a relative "motion" is not consistent with ordinary talk about both we and time "moving forward"...

The fundamental problem may be not so much the attempt at loose abstractions using words like "move" or "progress" or "forward/backward" or even "flow"... it is that our knowledge of the past is totally second hand (memories and physical evidence) in the same degree that our knowledge of the future is totally inferred (derived from premises).

 

[Drakkith]

Why must time itself be doing anything at all? We don't say that distance is moving simply because we pass an object, we say that either we or the object is moving. In the case of time I could say that all of us are moving through time at different rates depending on our relative velocities and other factors.

Of course that suggests that there is an absolute notion of time, something to measure all observers against. Unfortunately there is not, as everyone in an inertial frame will measure their own time as passing normally.

Here's something to consider. We measure time with a clock just like we measure distance with a ruler or some other device. Well, if I am traveling in a direction, and I turn around, am I now going negative distance? No! My change in position is still positive. IE I will move 1 meter per second forward, and when I turn around I will be moving 1 meter per second in the other direction.

So what would "reversing time" do? Would it even change anything? Does the concept even make any sense seeing that time doesn't have 3 degrees of freedom like space does? If there was a direction you could travel in time, and you turned it around, would you not be traveling a positive amount through time still? So even if you did reverse time for yourself perhaps your clock would still tick exactly the same.