[Serious] Is the Past Real?

[Anomalocaris]

Not necessarily, as a meandering black hole could be snaking its way over to us with a close encounter 12 months from now.

Highly unlikely as we have not detected any gravitational anomalies or any accretion disks.

It could be a small substellar mass primordial black hole slung shot towards us due to a close encounter with a pair of closely orbiting massive objects, so that it is too small to be accreting noticeable amount of matter from interstellar medium, and traveling too fast for it have been in the vicinity of the solar system for long enough to create detectable gravitational perturbations.

We can outline the known constrains on each element of this scenario, and in principle arrive at a probability of its occurance.   although because the constraints on some element, like the number of sub stellar black holes, are very loose, the range of probability is also going to be wide.

But this is an example of unknown, but in principle knowable.

[polymath257]

Highly unlikely as we have not detected any gravitational anomalies or any accretion disks.

Improbable, yes, but, not impossible.

But either way, would you say that the statement is either true or false?

[polymath257]

Highly unlikely as we have not detected any gravitational anomalies or any accretion disks.

It could be a small substellar mass primordial black hole slung shot towards us due to a close encounter with a pair of closely orbiting massive objects, so that it is too small to be accreting noticeable amount of matter from interstellar medium, and traveling too fast for it have been in the vicinity of the solar system for long enough to create detectable gravitational perturbations.

We can outline the known constrains on each element of this scenario, and in principle arrive at a probability of its occurance.   although because the constraints on some element, like the number of sub stellar black holes, are very loose, the range of probability is also going to be wide.

But this is an example of unknown, but in principle knowable.

Exactly. It has a truth value that *could* be determined.

Now, for quantum events, that is not the case.

So, suppose that I pick a single uranium atom. ALL we have is probabilities for when it will decay. We do NOT have, even in principle, a way to determine when it will decay. So the statement that it will decay tomorrow at noon is neither true nor false.

But I can go further. Suppose I have isolated a uranium atom last week. I have neither looked at it nor had any detector consider it. Is the statement that it decayed two days ago at noon one that has a truth value?

I would say not, just as the statement that it will decay tomorrow at noon does not.

[Jehanne]

Improbable, yes, but, not impossible.

But either way, would you say that the statement is either true or false?

Almost certainly true, barring a really unfortunate event!

[polymath257]

But either way, would you say that the statement is either true or false?

Almost certainly true, barring a really unfortunate event!

And, even in that unfortunate event, the statement is still either true or false?

[Jehanne]

Almost certainly true, barring a really unfortunate event!

And, even in that unfortunate event, the statement is still either true or false?

True. The eclipse will happen (almost surely) or it will not (virtually unlikely).

[HappySkeptic]

So, suppose that I pick a single uranium atom. ALL we have is probabilities for when it will decay. We do NOT have, even in principle, a way to determine when it will decay. So the statement that it will decay tomorrow at noon is neither true nor false.

But I can go further. Suppose I have isolated a uranium atom last week. I have neither looked at it nor had any detector consider it. Is the statement that it decayed two days ago at noon one that has a truth value?

I would say not, just as the statement that it will decay tomorrow at noon does not.

You are correct, although what determines "measurement" is a nebulous thing.  If a decay emits a Beta particle, it subsequently releases a gamma photon.  There is the possibility of the various particles interacting with other things.

Any of those interactions tend to increase the probability that the decay has been "detected".  Since wavefunction collapse is not actually explained by quantum-mechanics, there is a problem with determining when detection occurs.

One thing is clear - a person doesn't have to do the detecting.  Information just needs to be replicated sufficiently within a system such that the probability that the information doesn't persist for all time becomes vanishingly small.

[HappySkeptic]

Personally, I ponder the nature of time often and yet I really don't have a firm position. My symathies lie with presentism because I feel the past is truly gone and to the extent it exists it is in presents ghosts. Then as time goes on those ghosts fade while the set of possible paths that could have led to this moment increases. Then I think, certainly there is the way things actually happened so in some sense the past exists in some immutable way...from a god's eye view so to speak...regardless of whether from an objective reality (i.e. there are past objects) or an Akashic record.

Anyways, I was just curious what others thought about time.

From a practical point-of-view, humans live in the present.  Our perception of the present is actually the "past" few seconds, owing to our neurology.

From a physics point-of-view, there is a link between past, present and future.  That link is always past-toward-future for local events (causality), but this gets confusing when one considers the entire universe.  The The Wheeler–DeWitt equation for the wavefunction of the universe does not contain a time variable.  Einstein's relativity leads to the idea of future and past for far-away events being determined by ones reference frame.

From a mystical point-of-view, I consider past, present, and future to be all of equal "value". 

My argument is that most will agree that the events of the present have "value".  We assign moral or experiential good-or-bad to the present moment.  This "value" of experience may be shared (a community experience) or it may be solitary (or a good or bad event witnessed only by you).

The present doesn't actually exist for any period of time - it is seen in an echo of the past.  If the present has any value, it must continue to have value when the events are in the past.

The future is the present-to-come, and for those present-to-come events to have value, the future must have value.

Therefore, I consider all events, communal or private, as experienced by sentient beings anywhere in the universe, anywhere in time, to have value.  When bad things happen to others, we should be witnesses to it.  When good things happen to anyone we should rejoice.  We should learn from the past and work toward a better future.  And, as always, we must treasure the current moment.

[downbeatplumb]

I thought therefore I was.

[Anomalocaris]

It could be a small substellar mass primordial black hole slung shot towards us due to a close encounter with a pair of closely orbiting massive objects, so that it is too small to be accreting noticeable amount of matter from interstellar medium, and traveling too fast for it have been in the vicinity of the solar system for long enough to create detectable gravitational perturbations.

We can outline the known constrains on each element of this scenario, and in principle arrive at a probability of its occurance.   although because the constraints on some element, like the number of sub stellar black holes, are very loose, the range of probability is also going to be wide.

But this is an example of unknown, but in principle knowable.

Exactly. It has a truth value that *could* be determined.

Now, for quantum events, that is not the case.

So, suppose that I pick a single uranium atom. ALL we have is probabilities for when it will decay. We do NOT have, even in principle, a way to determine when it will decay. So the statement that it will decay tomorrow at noon is neither true nor false.

But I can go further. Suppose I have isolated a uranium atom last week. I have neither looked at it nor had any detector consider it. Is the statement that it decayed two days ago at noon one that has a truth value?

I would say not, just as the statement that it will decay tomorrow at noon does not.

I think we need to separate what is in principle unknowable to us, as opposed to what is in principle not knowable at all, when we say whether the past is real.    It seems to me If it is in principle knowable to someone somewhere, then it is real.   It is just that we don’t know it and can’t know it.  Chaucer’s last meal is in principle knowable to someone, even if we hypothesize that some quantum event forever obscures it from us and anyone with whom we in principle can communicate. 

It seems to be that the principle of indestructibility of information says all past must be knowable to someone somewhere, so it is real.