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Why is Time so controversial?
Posted: 10 November 2011 10:59 AM   [ Ignore ]   [ # 16 ]
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domokato - 10 November 2011 10:50 AM

The main question in my mind is if time is a dimension, like space, then why can we only go forward in time and not backward?

Well, I think the better question is “Why does it seem as though we’re going forward?” or “Why does it seem as though there’s an arrow of time, and not of space?” (And, indeed, one proposed answer has to do with entropy. Although how precisely that answers the question is still a bit mystifying).

From the point of view of objective time, there is no “going”. There is only the four dimensional spacetime manifold.

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Posted: 10 November 2011 11:00 AM   [ Ignore ]   [ # 17 ]
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domokato - 10 November 2011 10:50 AM

The main question in my mind is if time is a dimension, like space, then why can we only go forward in time and not backward?

(also, what show are we talking about?)

I think we need to examine what it means to go forward in time?

You are spread over time from birth to death.

No forward or backward motion.

Stephen

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Posted: 10 November 2011 11:03 AM   [ Ignore ]   [ # 18 ]
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traveler - 10 November 2011 10:52 AM
domokato - 10 November 2011 10:50 AM

The main question in my mind is if time is a dimension, like space, then why can we only go forward in time and not backward?

(also, what show are we talking about?)

Entropy!

Next question: why does entropy do that!

I’ve heard physicists say that time is symmetrical, that if you reverse time, the equations would still hold. But obviously they don’t, for entropy, and for forces like gravity. (?)

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Posted: 10 November 2011 11:04 AM   [ Ignore ]   [ # 19 ]
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George - 10 November 2011 07:40 AM

The way I imagine it works is like this: The moment Forrest Gump opens his box of chocolate while sitting on the bench in the park can be found either at 58 minutes into the movie (time), or, if we measure the length of the actual strip of the film, it happens in frame number 14,557 (space). Same thing.

Yes but this misses the crucial point.

When forrest Gump opens his box of chocolates that is now for him.

But no it can’t be! It’s no more now than 54 minutes into the film is now or three minutes into the film or…

Stephen

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Posted: 10 November 2011 11:06 AM   [ Ignore ]   [ # 20 ]
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dougsmith - 10 November 2011 10:59 AM
domokato - 10 November 2011 10:50 AM

The main question in my mind is if time is a dimension, like space, then why can we only go forward in time and not backward?

Well, I think the better question is “Why does it seem as though we’re going forward?” or “Why does it seem as though there’s an arrow of time, and not of space?”

But if I am my body and my body is only physical, then if it seems like I am going forward in time, then I actually am.

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“What people do is they confuse cynicism with skepticism. Cynicism is ‘you can’t change anything, everything sucks, there’s no point to anything.’ Skepticism is, ‘well, I’m not so sure.’” -Bill Nye

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Posted: 10 November 2011 11:11 AM   [ Ignore ]   [ # 21 ]
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domokato - 10 November 2011 11:06 AM

But if I am my body and my body is only physical, then if it seems like I am going forward in time, then I actually am.

Well ... no. Your body and you are physical, and they exist now, they exist in the future and they existed in the past. “You” are a long spacetime worm, stretched out in time as well as arrayed in space. What seems like it’s going forward in time is only a time-slice of you, you-now. Just like you-here is your elbow or your knee, depending on where you point.

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Posted: 10 November 2011 11:16 AM   [ Ignore ]   [ # 22 ]
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George - 10 November 2011 10:05 AM

Good point, Doug, as always. Sorry I am making a mess here.  red face

I wouldn’t be so quick to think you are George.

Doug spoke of “experienced time” but omitted to speak of that which has the experience.

From a scientific view we are four dimensional spacetime worms.

But we experience ourselves to be 3 dimensional. We experience it being now for us, not yesterday, not tomorrow. We experience ourselves being wholly present today, not as part of a spacetime worm.

From a scientific point of view it is no more today than 5,000 years ago.

Sometimes, often in fact, we make decisions that are bad for us today but good for us tomorrow. Why do we do it? We don’t just do it because we care about our future selves, we do it because we think we will be there! We think this thing that is me now will move along into the future and experience the reward.

That’s at odds with science, or so it seems.

I’m not prepared to bet on science in this case, is anybody, really?

Stephen

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Posted: 10 November 2011 11:34 AM   [ Ignore ]   [ # 23 ]
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dougsmith - 10 November 2011 11:11 AM
domokato - 10 November 2011 11:06 AM

But if I am my body and my body is only physical, then if it seems like I am going forward in time, then I actually am.

Well ... no. Your body and you are physical, and they exist now, they exist in the future and they existed in the past. “You” are a long spacetime worm, stretched out in time as well as arrayed in space.

I see, thanks. So I only experience anything because I am conscious. My consciousness could be anywhere in the time dimension, but it would only be aware of the present, have memories of the past (of past states, stored neurologically), and would be in a different state between any two points in time, which is why we can’t directly experience the past and the future (we are only physical objects undergoing state changes). If my consciousness (brain) were sped up, for instance, I would experience time pass more slowly. If it were slowed down, I would experience time pass more quickly. So my consciousness experiences changes in the states of matter (in the brain and environment) as the passage of time.

ETA: If you imagine repeating nerve impulses in the brain, it is easier to visualize. Our conscious experience is dependent on these impulses. And the impulses are just changes in states of matter. Hypothetically, if they could happen faster (analogous to a CPU clock speed up), you would get a faster experience of time (events), and vice versa. So our experience of time, including our place in it and movement through it, is inextricably tied to how our consciousness is “implemented”.

[ Edited: 10 November 2011 11:41 AM by domokato ]
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Posted: 10 November 2011 11:45 AM   [ Ignore ]   [ # 24 ]
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StephenLawrence - 10 November 2011 11:16 AM

But we experience ourselves to be 3 dimensional. We experience it being now for us, not yesterday, not tomorrow. We experience ourselves being wholly present today, not as part of a spacetime worm.

From a scientific point of view it is no more today than 5,000 years ago.

What do you mean? “It’s no more today than 5,000 years ago” is covertly indexical. You mean to say, “It’s no more today right now than 5,000 years ago”? But that’s false. Right now (spoken “today”) it is today.

When you say “It’s no more today than 5,000 years ago” you’re speaking from a vantage point outside of time, as it were. That’s not the vantage point we typically use when we’re saying “It’s today”. (Or perhaps better, “It’s Thursday today.”)

StephenLawrence - 10 November 2011 11:16 AM

Sometimes, often in fact, we make decisions that are bad for us today but good for us tomorrow. Why do we do it? We don’t just do it because we care about our future selves, we do it because we think we will be there! We think this thing that is me now will move along into the future and experience the reward.

That’s at odds with science, or so it seems.

I’m not prepared to bet on science in this case, is anybody, really?

Well, science is all about causality, and the causal chain leading from past to future. So none of that is at odds with science. It’s just that there’s no such thing as the special “now” in science. All times are “now” from their own vantage point, just like all places are “here” from their own vantage point.

Think of it this way: science has no problem with physical location in space. It has no problem with “here” understood as an objective locator of place. But it has no term for a special “here”.

Of course, all of the experiences of which George speaks are due to brain activity of one sort or another, and so in some sense are objective as well. But it’s a different sense than the sense we’re speaking of with “objective time”.

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Posted: 10 November 2011 11:46 AM   [ Ignore ]   [ # 25 ]
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domokato - 10 November 2011 11:34 AM
dougsmith - 10 November 2011 11:11 AM
domokato - 10 November 2011 11:06 AM

But if I am my body and my body is only physical, then if it seems like I am going forward in time, then I actually am.

Well ... no. Your body and you are physical, and they exist now, they exist in the future and they existed in the past. “You” are a long spacetime worm, stretched out in time as well as arrayed in space.

I see, thanks. So I only experience anything because I am conscious. My consciousness could be anywhere in the time dimension, but it would only be aware of the present, have memories of the past (of past states, stored neurologically), and would be in a different state between any two points in time, which is why we can’t directly experience the past and the future (we are only physical objects undergoing state changes). If my consciousness (brain) were sped up, for instance, I would experience time pass more slowly. If it were slowed down, I would experience time pass more quickly. So my consciousness experiences changes in the states of matter (in the brain and environment) as the passage of time.

ETA: If you imagine repeating nerve impulses in the brain, it is easier to visualize. Our conscious experience is dependent on these impulses. And the impulses are just changes in states of matter. Hypothetically, if they could happen faster (analogous to a CPU clock speed up), you would get a faster experience of time (events), and vice versa. So our experience of time, including our place in it and movement through it, is inextricably tied to how our consciousness is “implemented”.

Sure. And oddly the way causation works all that you can ‘experience’ is to one time of you: in your past. That’s odd because you can experience things to all spaces of you, so long as they are within your light cone. (So long as the light from them can reach you).

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Posted: 10 November 2011 11:47 AM   [ Ignore ]   [ # 26 ]
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If we are in a four dimensional world, why can I drive to the store than back home again, but can’t drive to when I was, say 20, then back again?

And as far as entropy goes, it only increases irreversibly in a closed system.  If we introduce more energy we can get it to go down.  So, why can’t we introduce more energy to get time to reverse?  big surprise

Occam

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Posted: 10 November 2011 11:50 AM   [ Ignore ]   [ # 27 ]
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Occam. - 10 November 2011 11:47 AM

If we are in a four dimensional world, why can I drive to the store than back home again, but can’t drive to when I was, say 20, then back again?

Right, well, that’s the question. It seems as though causation only goes in one direction, towards the future. But perhaps there are ways to drive into the past?

Occam. - 10 November 2011 11:47 AM

And as far as entropy goes, it only increases irreversibly in a closed system.  If we introduce more energy we can get it to go down.  So, why can’t we introduce more energy to get time to reverse?  big surprise

Another good question. I’ve never quite understood how entropy solves the problem of time’s arrow. It seems a correlation rather than an explanation. (Entropy is correlated with futurity, but it doesn’t explain futurity).

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Posted: 10 November 2011 12:09 PM   [ Ignore ]   [ # 28 ]
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Occam. - 10 November 2011 11:47 AM

If we are in a four dimensional world, why can I drive to the store than back home again, but can’t drive to when I was, say 20, then back again?

To drive back to when you were 20, you would need some other time dimension in which your consciousness could exist so that it could experience the going backwards in (normal) time.

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Posted: 10 November 2011 12:52 PM   [ Ignore ]   [ # 29 ]
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If we are a “stretched out worm in spacetime” as Doug said, all one needs to do is to move his consciousness. I guess in a way we do that when we recall our memories. Maybe some drug could make these experiences more vivid. Doesn’t LSD do that?

In that sense, I guess we can move forward in time when we plan our future. Again, if we were really good at it (with the help of some drug to help us concentrate) it could feel pretty real I imagine.

[ Edited: 10 November 2011 01:03 PM by George ]
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Posted: 10 November 2011 01:06 PM   [ Ignore ]   [ # 30 ]
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George - 10 November 2011 12:52 PM

If we are a “stretched out worm in spacetime” as Doug said, all one needs is do is to move its consciousness.

Let’s see: to ‘move the consciousness’ implies moving it with respect to some index. But consciousness just follows along with certain brain processes. The consciousness doesn’t move with respect to time any more than the brain processes move with respect to time. (That is, it ‘moves’ in the same respect that anything physical moves, it doesn’t move in some special way).

Think of it this way: movement is just change through time, and brain processes do change through time, but the ‘movement’ is no more real than the fact that you are thin at one end, thicker in the middle and thinner at the other end. It would be odd to say that your physical shape moves as you note different physical slices through your body.

Or another way: you are conscious in your past, you are conscious now, and you will be conscious in your future. There is only the consciousness that changes through time. If that change through time is all you mean by ‘movement’, we’re OK.

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