dougsmith - 08 May 2011 11:46 AM

To put it another way, if “the present” is a dimensionless point, then it can’t encompass change. Then presentism doesn’t even achieve what it claims to set out to do, which is to take seriously our experienced present.

I think if we ask what the present is we immediately bump into problems. What I mean is I might say this is the present but the response is whoops it’s gone. But it hasn’t gone because now keeps on moving along.

We experience a continuous now.

Stephen

Continuing these thoughts, for us, subjectively at least, it is always now, we cannot experience anything else than it being now.

StephenLawrence - 08 May 2011 12:20 PM

Continuing these thoughts, for us, subjectively at least, it is always now, we cannot experience anything else than it being now.

Right, again, isomorphic to the case of “here”. Wherever we experience things, it’s always “here”.

dougsmith - 08 May 2011 12:21 PM

StephenLawrence - 08 May 2011 12:20 PM

Continuing these thoughts, for us, subjectively at least, it is always now, we cannot experience anything else than it being now.

Right, again, isomorphic to the case of “here”. Wherever we experience things, it’s always “here”.

Yes Doug but I think the problem is what is this subject of experience as objectively we are spread over different places and times.

Stephen

dougsmith - 08 May 2011 11:46 AM

isaac - 08 May 2011 11:35 AM

and presumably a presentist would not be ok with “now” meaning “this century”.  But if they narrow it down to “the smallest possible unit”, then they’re not talking about the world that we see or act on, right?

Well, I think if presentism is going to be metaphysically true-to-its-roots, then the ‘present’ will have to be strictly dimensionless, it will have to be a single point in time that’s ‘the present’. Note that that isn’t even enough to fit the experienced present, which is a short-ish span of time, encompassing slight change. (Viz., the “specious present” that I mentioned before). This is another grave problem with presentism, that inthegobi was getting at, above.

To put it another way, if “the present” is a dimensionless point, then it can’t encompass change. Then presentism doesn’t even achieve what it claims to set out to do, which is to take seriously our experienced present.

aye, aye.

isaac - 08 May 2011 11:35 AM

and presumably a presentist would not be ok with “now” meaning “this century”.  But if they narrow it down to “the smallest possible unit”, then they’re not talking about the world that we see or act on, right?

From the wiki on the present

As a concept of current time:

The present is the time that is associated with the events perceived directly and in the first time, not as a recollection (perceived more than once) or a speculation (predicted, hypothesis, uncertain). It is a period of time between the past and the future, and can vary in meaning from being an instant to a day or longer.

Philosophical problem:

“The present” raises the difficult question: “How is it that all sentient beings experience now at the same time?” There is no logical reason why this should be the case and no easy answer to the question.

Special Relativity’s “present”:

One has to conclude that in relativistic models of physics there is no place for “the present” as an absolute element of reality. Einstein phrased this as: “People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion”.

Today vs. now:

“Today” signifies a “day” in a 24-hour interval to signify one’s stance within the plane of time, this is contrary to “now”, because “now” has no definite measure for its own duration. On the graph of Space-Time, the present can appear to be infinitely small, or account for a large portion of a sequence.

Thus, if time is a continuum, then the present (depending on context) can be an instant which is infinitely small (but not zero), a second, minute, hour, day(24 hours), month, year etc.

If time is discrete, i.e. there is a quantum unit of time (Planck time), then the smallest present is that interval.

If time is a continuum, it is problematic to demarcate the past/future as distinct realms and if time is discrete, it is impossible. It makes more sense to consider time as a sequence of presents.

However, if one were to take SR’s time as time in reality (as eternalism do), then there is no distinction between present, past or future at all which is counter-intuitive to all conscious human experience of time. This is unacceptable to most conscious humans, notwithstanding SR.

Two questions which arises are:

1. Should conscious humans believe their experience of time or abandon it as an illusion to be discarded for belief in SR’s time?

2. Is SR’s time really the nature of time or is physics simply misrepresenting time by treating it as a dimension like space?

kkwan - 10 May 2011 11:54 PM

Philosophical problem:

“The present” raises the difficult question: “How is it that all sentient beings experience now at the same time?” There is no logical reason why this should be the case and no easy answer to the question.

This is one of those claims that sounds profound until you realize it’s true by definition and therefore completely content-free.

What it doesn’t do is to say anything about the relativity of simultaneity which makes a hash of whatever metaphysical point the author was trying to get out of it.

kkwan - 10 May 2011 11:54 PM

1. Should conscious humans believe their experience of time or abandon it as an illusion to be discarded for belief in SR’s time?

I think that is a good question.

I’m on the fence because I’m not going to accept my experience of time passing is an illusion without very good reason.

I think the claim that the experience is an illusion is an extraordinary claim, so it requires extraordinary evidence.

But p’raps science is providing that extraordinary evidence?

Stephen

Is “time” anything more then an arbitrary marker by which to catalog past and upcoming events?

We define the passage of time according to our unique position in the universe. By the revolution of our planet and our planet’s revolution about the Sun.

Events occur which cause the next moment to occur. There is an expectation that events in this moment will cause the future to be what it is. Time is just a way to label how long ago, according to our somewhat arbitrary method of measurement, an event occurred. Or the number of times or percentage thereof the earth will revolve before some “future” event will occur.

We experience change. Not really the “passage of time” IMO.

Any concept of metaphysics probably just comes from thinking our method of identifying unique events has any meaning outside of the system it was designed for.

Gnostikosis - 11 May 2011 01:08 PM

Is “time” anything more then an arbitrary marker by which to catalog past and upcoming events?

We define the passage of time according to our unique position in the universe. By the revolution of our planet and our planet’s revolution about the Sun.

Events occur which cause the next moment to occur. There is an expectation that events in this moment will cause the future to be what it is. Time is just a way to label how long ago, according to our somewhat arbitrary method of measurement, an event occurred. Or the number of times or percentage thereof the earth will revolve before some “future” event will occur.

We experience change. Not really the “passage of time” IMO.

Any concept of metaphysics probably just comes from thinking our method of identifying unique events has any meaning outside of the system it was designed for.

Time has as much reality as space. It’s just as useful physically, and just as measurable by objective instrumentation.

dougsmith - 11 May 2011 01:25 PM

Time has as much reality as space. It’s just as useful physically, and just as measurable by objective instrumentation.

Ok, what is time and how do you put your finger on it? (figuratively)

In measuring time what are you actually measuring other then the revolution of a planet or some other cyclic event?

I’m not saying the concept of time is not useful.

Gnostikosis - 11 May 2011 01:46 PM

dougsmith - 11 May 2011 01:25 PM

Time has as much reality as space. It’s just as useful physically, and just as measurable by objective instrumentation.

Ok, what is time and how do you put your finger on it? (figuratively)

In measuring time what are you actually measuring other then the revolution of a planet or some other cyclic event?

I’m not saying the concept of time is not useful.

Time is another dimension like the three of space. Time is actually an integral part of spacetime, which is the more appropriate terminology according to Einstein.

Time is measured by clocks or pendulums; indeed, IIRC Einstein defined time as that part of spacetime that was measurable by clocks or pendulums. But use of a cyclical device is essential, since a cyclical device by definition introduces a regular separation. We do the same to measure space, e.g., with a meter stick, that has regular separations between elements of space. A meter stick is a clock for space. A clock is a meter stick for time.

Spacetime is (at least according to our best established physics) one of the most basic parts of reality; as a result there’s not a whole lot one can say about it other than it exists. I believe there are various theoretical approaches that attempt to understand or explain spacetime in terms of some more basic principles (including quantum principles, string theory, or hidden extra dimensions). But until and unless these theories are experimentally verified and become mainstream, we’re stuck with Einsteinian spacetime.

Sorry—that’s all off the cuff. There is more at Wiki.

dougsmith - 11 May 2011 04:03 AM

kkwan - 10 May 2011 11:54 PM

Philosophical problem:

“The present” raises the difficult question: “How is it that all sentient beings experience now at the same time?” There is no logical reason why this should be the case and no easy answer to the question.

This is one of those claims that sounds profound until you realize it’s true by definition and therefore completely content-free.

What it doesn’t do is to say anything about the relativity of simultaneity which makes a hash of whatever metaphysical point the author was trying to get out of it.

It does not refer to the “relativity of simultaneity” because for all sentient beings (presumably human and all are on the earth), simultaneity is local and does not extend to the Andromeda galaxy, neither are they traveling anywhere near light speed (if it is possible) wrt to others on the earth.

It is a philosophical, not a physics problem.

StephenLawrence - 11 May 2011 12:27 PM

I’m on the fence because I’m not going to accept my experience of time passing is an illusion without very good reason.

I think the claim that the experience is an illusion is an extraordinary claim, so it requires extraordinary evidence.

But p’raps science is providing that extraordinary evidence?

From this interesting paper by John D. Norton on Time Really Passes

Time really passes. It is not something we imagine. It really happens; or, as I shall argue below, our best evidence is that it does. Our sense of passage is our largely passive experience of a fact about the way time truly is, objectively. The fact of passage obtains independently of us. Time would continue to pass for the smoldering ruins were we and all sentient beings in the universe suddenly to be snuffed out.

Back to reality:

Most significantly, the delivery of the doses is perfect. There are no revealing dislocations of serial order of the moments. While there may be minor dislocations, there are none of the types that would definitely establish the illusory character of passage. We do not, for example, suddenly have an experience of next year thrown in with our experience of today; and then one of last year; and then another from the present.

The desperate stratagem:

Now consider the passage of time. Is there a comparable reason in the known physics of space and time to dismiss it as an illusion? I know of none. The only stimulus is a negative one. We don’t find passage in our present theories and we would like to preserve the vanity that our physical theories of time have captured all the important facts of time. So we protect our vanity by the stratagem of dismissing passage as an illusion.

As good as it gets:

We should stop protecting our vanity and admit what is now becoming obvious to me. We have no good grounds for dismissing the passage of time as an illusion. It has none of the marks of an illusion. Rather, it has all the marks of an objective process whose existence is independent of the existence of we humans.

From the appendix:

First, I think it is uncontroversial that we experience time as moments. That is, we experience the present moment directly. We have indirect access to the past through memory and other traces and we have even more tenuous access to the future through predictive methods. We do not experience temporal relations directly. That is, we do not experience directly that last Wednesday’s snowstorm was earlier than today’s rain shower. We experience today’s rain shower and recall the snowstorm, inferring from that their temporal relation.

Second, we do have a direct perception of the changing of the present moment. That is clearest in our perception of motion.

Do read the whole paper to get the full picture.