[alancalverd]

Earlier periods of time depend on later times. For example, if you had not been born, would you exist now?

A complete inversion of logic, as I hope you realise.

From birth to writing this, is a sequence of events, separated by time. If I stop writing, I will not be unborn. Later events depend on former events, not the other way around. The length of time between now and my going to bed will not affect the number of years that elapsed between birth and now.

[Devans99 (OP)]

A complete inversion of logic, as I hope you realise.

From birth to writing this, is a sequence of events, separated by time. If I stop writing, I will not be unborn. Later events depend on former events, not the other way around. The length of time between now and my going to bed will not affect the number of years that elapsed between birth and now.

I think you need to reread my argument.

My argument relies on 'Later events depend on former events'.

[Devans99 (OP)]

A complete inversion of logic, as I hope you realise.

Sorry, you are correct, what I mean to say in my original argument was 'later times depend on earlier time'.

So the argument was meant to read:

1) the first time period (eg first second), causes the 2nd time period (2nd second)
2) if the first time period (the first second of time) does not exist, then the second time period cannot exist because it is defined by and dependant on the first time period.
3)  If the nth time period does not exist, then the nth+1 time period cannot exist.
4) So by mathematical induction, time cannot exist at all if it has no initial time period - a start of time is required else the rest of time is undefined and cannot exist.

[chiralSPO]

You are implicitly using your assumption of bounded time to invalidate the assumption of no starting point.

Sorry, I'm a bit new to unbounded time.

Thank you for acknowledging this :-) It is the key to learning more.

My limited understanding:

We imagine spacetime as a surface of a sphere - then it sort of seems unbounded.

But you can set co-ordinates in an arbitrary way (chose 0,0 - the origin), then all points are relative to the origin and spacetime has a definite, finite, start and end in all dimensions.

So you could say that unbounded spacetime is sort of bounded?

Yes, you can have non-bounded but still finite surfaces (and spaces) if there is curvature.

I'm not sure that the surface of a sphere really applies to time though (and one can go directly East on the Earth indefinitely, they just wouldn't actually leave the boundary). It could be reasonable to model time like the radial component of polar coordinates, where the origin is actually a meaningful 0, and there isn't any meaningful interpretation of negative values.

[Colin2B]

So the argument was meant to read:

1) the first time period (eg first second), causes the 2nd time period (2nd second)
2) if the first time period (the first second of time) does not exist, then the second time period cannot exist because it is defined by and dependant on the first time period.
3)  If the nth time period does not exist, then the nth+1 time period cannot exist.
4) So by mathematical induction, time cannot exist at all if it has no initial time period - a start of time is required else the rest of time is undefined and cannot exist.

The conclusion is still invalid and is not a logical conclusion.
The definition and numbering of time periods is arbitrary. Take our Western year numbering system which defines an arbitrary start time, but this does not imply there are no years before 0AD. Similarly we can define other arbitrary start times eg start of lockdown and count the days forward, but again it does not imply there is nothing that goes before.
The same applies to what is misleadingly called Big Bang. This is the earliest event we are able to detect and we can take it as an arbitrary zero, however, just because we measure from this point does not mean time did not exist prior to BB. It may be that the phenomenon we call time started at BB, but there are other hypotheses; a previous universe may have collapsed leading to a sudden re-expansion, or there may have been an infinite time with nothing before a spontaneous event, we really do not know because any evidence was destroyed at BB.
As @chiralSPO points out, there are ways of modelling spacetime which have a definite 0 and other ways where it does not. Personally I suspect ±∞ centred on the current instant of time 

[alancalverd]

1) the first time period (eg first second), causes the 2nd time period (2nd second)

No. The first event causes the second event. Time period is what lies between* them. It is an effect, not a cause.


*obnoxious phrase, but "separates" can be misinterpreted as an action.

[Devans99 (OP)]

Yes, you can have non-bounded but still finite surfaces (and spaces) if there is curvature.

I'm not sure that the surface of a sphere really applies to time though (and one can go directly East on the Earth indefinitely, they just wouldn't actually leave the boundary). It could be reasonable to model time like the radial component of polar coordinates, where the origin is actually a meaningful 0, and there isn't any meaningful interpretation of negative values.

With polar coordinates, the time dimension would have an arbitrary start/end. We could choose it to be 0 degrees for example.

Even simpler than polar you could imagine 2d spacetime (1 space, 1 time) as the latitude and longitude of the earth. If time was represented by longitude, the we could choose the meridian line as the start/end of time.

The choice of the start/end of time for an unbounded but finite universe can be arbitrary, but I think there would have to be a real, physical, start of time in such universes - time is built up sequentially (1st day defines the 2nd, 2nd the 3rd, etc...) - so this sequential building up of time would have to have a starting point (eg the meridian line)

A simple interpretation of the unbounded but finite universe option suggests to me that time meets itself (at the meridian line) - so time has to be in the same state at the start and end of time - so that would be a closed type of universe - a big bang that coincides with a big crunch - both events being at the start/end of time (the meridian line).

But I think it gets more complex than this. Hawking represented time as a complex number with his 'no boundary proposal'. That strikes me as wrong: time is a single, linear, degree of freedom - time absolutely does not have a real and imaginary component.

[Devans99 (OP)]

No. The first event causes the second event. Time period is what lies between* them. It is an effect, not a cause.


*obnoxious phrase, but "separates" can be misinterpreted as an action.

If we have a week: mon, tues, wens, thurs, fri, sat, sun.

Then you remove Monday from existence, does the rest of the week still exist?

No it does not. Say I flew to Paris on Monday. But Monday no longer exists. Where exactly I am on Tuesday?

BTW The argument for the start of time works with causation just fine to:

If the chains of cause and effect stretch back forever, then there cannot be a first cause. The first cause would cause the 2nd cause - without the first cause, the second cause cannot be. Likewise, the nth cause would cause the nth+1 cause, so by mathematical induction, causality cannot exist at all if there is no first cause. But causality does exist, so there must be a first cause. Because it is uncaused, it must be outside of time, which implies time has a start.

[Halc]

Sorry, I'm a bit new to unbounded time.

You seem to have opened over say 50 threads on various forums, all more or less on this topic, and all committing the same fallacies over and over. You're not new to it, you're just acting that way for whatever purpose you have in doing this. Learning to avoid your logic mistakes does not seem to be this purpose. I can think of only two other reasons.

2) If the first time period (the first second of time) does not exist, then the second time period cannot exist because it is defined by and dependant on the first time period.

Presentism denies this assertion, and is still considered a logically valid view. I offer it as counterexample to your assertion here.

3) If the nth time period does not exist, then the nth+1 time period cannot exist.
4) So by mathematical induction, time cannot exist at all if it has no initial time period

By induction, this logic (if better worded) leads to no end of time. If you want to draw some conclusion about the past, you need to talk about the nth-1 period, not the nth+1.  Such logic (typically asserting any moment requires a prior moment) is used to conclude a lack of an initial time period since it would violate such a premise.

Yet days pass and we can count them - so the past clearly has a length.

You've learned absolutely nothing from all the prior identical threads.  I can count the negative integers, yet the set of negative integers does not have a size (a beginning).  There's no most-negative integer. Your logic here actually leads to the opposite conclusion than the one you draw, but that doesn't stop you from just asserting a conclusion that doesn't follow at all.

Mind you, I'm not asserting an infinite past. I'm just pointing out that your logic is invalid.

Well that contradicts our finding that the past has a length.

You've not established that the past has a finite length except to assert it, which is begging the question, a different fallacy.

Think of space being measured by a ruler which goes on forever - every possible finite number x is inscribed on the ruler and it goes on forever - so the ruler must be longer than all finite numbers x but finite numbers go on forever, so that’s impossible (how can something be longer than a thing with no end?).

You didn't establish that it was longer than a thing with no end. You established that it was longer than any particular finite value along the ruler, but none of those values are the length of the ruler.

I imagine spacetime as maybe something (something physical) within a sea of 'nothingness'.

That would be space being contained by other space.

'Nothingness' cannot be said to be infinite because it does not exist.

So you're saying that our spacetime is something within a sea of something nonexistent, which is pretty close to asserting the nonexistence of the universe.

[Devans99 (OP)]

The definition and numbering of time periods is arbitrary.

Sure, but you can use any measuring system for time (eg Planck units) and reach the same conclusion.

As time enables motion, time and motion are equivalent, so any regular motion allows us to measure time. So we can always break time down into units of different times.

[Devans99 (OP)]

2) If the first time period (the first second of time) does not exist, then the second time period cannot exist because it is defined by and dependant on the first time period.

Presentism denies this assertion, and is still considered a logically valid view. I offer it as counterexample to your assertion here.

How exactly does presentism deny this assertion?

[alancalverd]

I flew to Paris on Monday. But Monday no longer exists. Where exactly I am on Tuesday?

Of course it no longer exists - Monday (and every other Monday before 29 June 2020) was a time period in the past. You are in Paris, and it is Tuesday.

Monday is not a cause. And even if it were, your great-grandparents probably no longer exist. Do you? Press the big red button, bomb disappears, hole appears in the ground. The disappearance of the cause was essential to the effect!

Moral: beware of -isms. Use your eyes and brain, the tools of science.

[Devans99 (OP)]

I flew to Paris on Monday. But Monday no longer exists. Where exactly I am on Tuesday?

Of course it no longer exists - Monday (and every other Monday before 29 June 2020) was a time period in the past. You are in Paris, and it is Tuesday.

So you were in London on Sunday.
You flew to Paris on Monday.
Now it is Tuesday and you are in Paris.
But Monday does not exist (by the argument we are using) - so you never flew to Paris.
So how can you be in Paris when you are in London?

[Bill S]

But Monday does not exist (by the argument we are using) - so you never flew to Paris.

That’s a non sequitur.

I’m breathing, as hopefully are you, I take a breath, I exhale and it is gone; like all my former breaths, it no longer exists.  As I take my next breath, I know that that would not be possible without the foregoing succession of breaths I’ve been taking for the past 80 years. All of those years, and all of those breaths, no longer exist, but their influence certainly does, or I would not be posting this.

[Devans99 (OP)]

But Monday does not exist (by the argument we are using) - so you never flew to Paris.

That’s a non sequitur.

I’m breathing, as hopefully are you, I take a breath, I exhale and it is gone; like all my former breaths, it no longer exists.  As I take my next breath, I know that that would not be possible without the foregoing succession of breaths I’ve been taking for the past 80 years. All of those years, and all of those breaths, no longer exist, but their influence certainly does, or I would not be posting this.

Why is it a 'non sequitur'?

Later time periods are dependant upon earlier time periods. Take this example:

1. A particle is at position 1 at time 1
2. The particle is at position 2 at time 2
3. The particle is at position 3 at time 3

If we remove [2], then the particle jumps discontinuously from position 1 to 3 - so [3] can only exist if [2] exists - [3] depends upon [2].

[Bill S]

Why is it a 'non sequitur'?

What planet are you from?

Take this example:

Interesting that you expect me to take your example, when you have totally ignored mine.

If we remove [2],

By your logic, you can't; it doesn't exist, once you've reached [3].

[Devans99 (OP)]

Why is it a 'non sequitur'?

What planet are you from?

But you have not said why it is a  'non sequitur'?

You can't just say somethings wrong and then refuse to say why!

[Bill S]

You can't just say somethings wrong and then refuse to say why!

Where, exactly, did I refuse to do anything?

[Devans99 (OP)]

You can't just say somethings wrong and then refuse to say why!

Where, exactly, did I refuse to do anything?

I'll go through it again for you. I stated that later times are dependent on earlier times and gave as justification an arguments involving removing the day Monday:

1) So you were in London on Sunday.
2) You flew to Paris on Monday.
3) Now it is Tuesday and you are in Paris.
4) But Monday does not exist (we've removed it from existence) - so you never flew to Paris.
5) So how can you be in Paris when you are in London?

You said 4 is ‘a non sequitur’.

Why?

[alancalverd]

But Monday does not exist (by the argument we are using) - so you never flew to Paris.

Irrelevant. Monday did exist, as the interval of time during which I flew from London (before) to Paris (after).

Unless you are very special (and I mean physically, not educationally), your great grandparents probably don't exist, but you seem to, because they once did. 

You didn't need to remove Monday from existence. It disappeared all by itself, just like every other day in the past.