Does time exist?

Morbert

roosh wrote: »

@Morbert - Just a subsequent question, which I'm wondering about; you've mentioned that the order of events, and simultaneity isn't physical; does this mean that relativity of simultaneity isn't physical, given that it essentially just a concept for saying that the ordering of events is different according to different reference frames.

Also, isn't it the ordering of events that lead to the conclusion that what is the present for one observer could be the past for another; if the ordering isn't physical can we conclude that the past isn't physical?

Are "the past" and "the future" not just an extension of the concept of "the ordering of events"?

Yes, the past, present, and future as defined by reference frames aren't physical. To build an understanding of the physical past, present, and future, we have to look at the frame-independent picture of the universe. This is where the cone-structure of Minkowski space is important. Every event has a "future cone" and a "past cone", which, physically speaking, are events that satisfy certain relations with the event in question. This a physical quality, not frame-dependent. The ordering is in this case is physical. For example, there is a physically ordering of the event "me typing this message" and "you reading this message", an ordering that is invariant under Lorentz transformations.

However, if an event falls outside the future or past cone of another event, those events are neither in the past nor the future of each other in any physical sense.

Masteroid

Morbert wrote: »

However, if an event falls outside the future or past cone of another event, those events are neither in the past nor the future of each other in any physical sense.

Out of interest, could you give an example of two events that could fill such criteria, i.e., an event that is in neither the future nor the past of another event?

Morbert

Masteroid wrote: »

Out of interest, could you give an example of two events that could fill such criteria, i.e., an event that is in neither the future nor the past of another event?

An example of two events would be you reading this message, and a supernova explosion in the Andromeda galaxy.

Any two events which could not have been connected by a hypothetical photon.

Masteroid

Morbert wrote: »

An example of two events would be you reading this message, and a supernova explosion in the Andromeda galaxy.

Any two events which could not have been connected by a hypothetical photon.

Are you saying that past and future can only exist relative to two events if there is a causal history between those events, that two events must have common ancestors in order to be in each other's past or present?

Suppose there is a supernova occuring in the Andromeda galaxy. If that supernova had not occured then the universe would be different.

Would I be able to read your message even if the most distant supernova had not occured?

How can you be certain that this part of the universe would exist as it is if any other more distant events had occured differently?

Is it not possible that even if our own galaxy had been created with just one star more, or less, in it that life might never have occured on earth?

It seems to me that the universe as it is is the only possible outcome that could be determined from its previous configuration. In order for the supernova to not be occuring, the big bang would have had to have been different in terms of how it proceeded.

This means that everything in the universe is connected, in a sense, to the big bang. The world-line of the universe therefore contains and is connected to all the world-lines of all the events in the universe.

The world-line of that supernova in the Andromeda galaxy (SNAG) intersects a great many other world-lines. If we were to subtract the SNAG worldline from the universe we have to alter all the world-lines it had intersections with and that in turn would affect other, more remote world-lines and the result would be that the world-line of the universe would be different.

So really it could be that, if the SNAG hadn't occured in my past then I could not have composed this reply.

Is there not an 'interdependency' between world-lines such that one can affect all others? How world-lines are determines how the universe is. I'm thinking of how a small plughole at one end of the bath effects the behaviour of all the water in the bath. (Not too convoluted, I hope.)

Surely all light-cones intesect the universe's light-cone in the past, all events occur in some future light-cone of some other event. Every event is a link in the cause/effect chain

roosh

Morbert wrote: »

Yes, the past, present, and future as defined by reference frames aren't physical. To build an understanding of the physical past, present, and future, we have to look at the frame-independent picture of the universe. This is where the cone-structure of Minkowski space is important. Every event has a "future cone" and a "past cone", which, physically speaking, are events that satisfy certain relations with the event in question. This a physical quality, not frame-dependent. The ordering is in this case is physical. For example, there is a physically ordering of the event "me typing this message" and "you reading this message", an ordering that is invariant under Lorentz transformations.

However, if an event falls outside the future or past cone of another event, those events are neither in the past nor the future of each other in any physical sense.

This is actually a point I was going to raise myself, as it was a point that was raised in a discussion elsewhere; I think it is very similar to, if not the same as, the point masteroid is making. I think we can use it to see how our definition of "no", "past" and "future" are different.

It seems that the definition of past and future events, according to the light cone structure, defines "past" in terms of those events which have a causal effect on our present, where some events can exist in the universe such that they are neither physically in an observers past or future. Herein lies an issue with what is meant by "the past".


If we consider that the universe consists of more than just ourselves; that is, extreme solipsism is incorrect and there do exist distant parts of the galaxy which are spatially separated from us.

Now, if we consider what we refer to as now, without getting caught up in trying to establish what events have actually occurred now, we can reason that, given the existence of distant parts of the universe and the probability that there are events occuring there, there must be events which occur, in those distant parts of the universe, which are simultaneous with our now.

However, given the spatial separation of those events, and the finite speed of light, we can reason that by the time a photon from that distant event reaches us, the physial emitting event must necessarily be in our past; even if the event itself wasn't in our past light cone until a moment after the photon reached us in our present.

The event, which is in our "past" may not have a causaul influence on our perception until a later point, but that doesn't mean that it isn't in our "past".

Morbert

roosh wrote: »

This is actually a point I was going to raise myself, as it was a point that was raised in a discussion elsewhere; I think it is very similar to, if not the same as, the point masteroid is making. I think we can use it to see how our definition of "no", "past" and "future" are different.

It seems that the definition of past and future events, according to the light cone structure, defines "past" in terms of those events which have a causal effect on our present, where some events can exist in the universe such that they are neither physically in an observers past or future. Herein lies an issue with what is meant by "the past".

It is the same definition as used in the Newtonian picture. The only difference is in the Newtonian picture, there is no upper bound on the speed signals travel. The cones in the Newton picture are so wide that they are flat hypersurfaces corresponding to the common sense notion of moments.

If we consider that the universe consists of more than just ourselves; that is, extreme solipsism is incorrect and there do exist distant parts of the galaxy which are spatially separated from us.

Now, if we consider what we refer to as now, without getting caught up in trying to establish what events have actually occurred now, we can reason that, given the existence of distant parts of the universe and the probability that there are events occuring there, there must be events which occur, in those distant parts of the universe, which are simultaneous with our now.

However, given the spatial separation of those events, and the finite speed of light, we can reason that by the time a photon from that distant event reaches us, the physial emitting event must necessarily be in our past; even if the event itself wasn't in our past light cone until a moment after the photon reached us in our present.

The event must have been in our past light cone if it was able to send a photon to us. The "even if" scenario you have in blue is impossible.

The event, which is in our "past" may not have a causaul influence on our perception until a later point, but that doesn't mean that it isn't in our "past".

You're confusing concepts here. Light cones pertain to events, not entire histories. The event (the emission of a photon) is physically in the past of the event it influences (us seeing the photon).

roosh

Morbert wrote: »

It is the same definition as used in the Newtonian picture. The only difference is in the Newtonian picture, there is no upper bound on the speed signals travel. The cones in the Newton picture are so wide that they are flat hypersurfaces corresponding to the common sense notion of moments.



The event must have been in our past light cone if it was able to send a photon to us. The "even if" scenario you have in blue is impossible.



You're confusing concepts here. Light cones pertain to events, not entire histories. The event (the emission of a photon) is physically in the past of the event it influences (us seeing the photon).

Do all events which fall outside an observers past and future light cones, necessarily exist in their present?

Also, if a star goes supernova in the Andromeda galaxy now and I count to five, will that supernova exist in the past light cone of "me plus the five count"; I presume it doesn't; would it exist in my future light cone?

Morbert

roosh wrote: »

Do all events which fall outside an observers past and future light cones, necessarily exist in their present?

Also, if a star goes supernova in the Andromeda galaxy now and I count to five, will that supernova exist in the past light cone of "me plus the five count"; I presume it doesn't; would it exist in my future light cone?

I'll answer both these questions together.

Let's use a more local example. Let's take the example of the sun exploding. Both "you" and "you plus five" would both be causally unconnected to the sun exploding. The explosion would not exist in the past or future light cone of "you" or "you plus five". All observers would agree that you would have to count to around 480 before the sun exploding would be in your past light cone (At which point, the sun exploding would have a causal influence on you, and a catastrophic one at that). You wouldn't say events not in the past or future light cones must necessarily be in the present though, unless you use a very unconventional definition of present.

Masteroid

Morbert wrote: »

I'll answer both these questions together.

Let's use a more local example. Let's take the example of the sun exploding. Both "you" and "you plus five" would both be causally unconnected to the sun exploding. The explosion would not exist in the past or future light cone of "you" or "you plus five". All observers would agree that you would have to count to around 480 before the sun exploding would be in your past light cone (At which point, the sun exploding would have a causal influence on you, and a catastrophic one at that). You wouldn't say events not in the past or future light cones must necessarily be in the present though, unless you use a very unconventional definition of present.

I got a bit lost here. How can 'roosh' and 'roosh + 5' have a light-cone each if both 'rooshes' are seperate events?

Also, 'roosh' and 'roosh +5' are causally connected so what effects 'roosh' must also effect 'roosh +5'.

And if the sun explodes 'NOW!', isn't roosh's destruction in the future cones of both the sun and roosh?

In fact, how is it even possible for the sun and roosh not to be in each other's light-cones?

The thing is, roosh is more than a photon being absorbed by an electron. That would be an event wouldn't it? And photons don't have light-cones.

They can't. The universe is zero length and and the time between emission and absorption of a photon is zero. A photon does not have a future or a past because, in its own FoR, it didn't exist in the past or future.

What does that mean? That all photons exist 'now'?

I know there are a lot of question marks here but they are mostly rhetorical. My point is, where do you draw a line on roosh's history or future? Are not his great-great-great-great-grandparents in his past light-cone and are not his great-great-great-great-grandchildren not in his future one? Doesn't roosh's past light-cone extend all the way back to the big bang?

And therefore, don't all light-cones intersect?

I brought this up before but it went without comment, there are two kinds of causal link, two types of experience. Being involved in a collision is not the same as observing a collision from a distance.

Similarly I pointed out that there are two distinct types of perception. There is the kind of perception that comes from observation through experience, being caught in an earthquake for example, and there is the kind of perception that comes from experience through observation where for example, you might see a news broadcast about people caught in an earthquake.

I think it is excessive to say the least to consider the kind of photonic interactions we've been discussing so far in relation to perception as creating a causal link between two events. They rather connect two seperate causal chains.

The gamma rays produced in a supernova are not the supernova, they are the debris that was created by a supernova. When we detect such gamma rays we do not directly observe a supernova, we deduce it. The supernova occured in the past of the gamma rays. The gamma rays are no more than a collection of data that partially describe the supernova.

The star that went supernova has its causal sequence and an observer of gamma rays so produced has his. But the progress of science does not depend on any particular supernova. Any will do for the purpose of observation.

And evolution recognises this. By being able to perceive the debris created by events, we can avoid the intersection of two seperate causal chains.

Or, roosh might be walking down the road when he sees a man wearing a hoodie walking toward him. Roosh might then cross the road.

Did the man in the hoodie cause roosh to cross the road or did roosh perceive the hoodie and cause himself to try and prevent a causal link from developing between them? The man in the hoodie may never even see roosh.

You could say that an emitted photon is the effect of a previous event and that absorption is the cause of a different and random later event.

Supernovae cause themselves to be seen and men cause themselves to look for them. There is no causal link between the two but our telescopes allow us to create 'pseudo-causal' links by pointing them in different directions until we detect unusual phenomena.

The supernova didn't cause the telescope and the telescope didn't cause the supernova, men caused telescopes and supernovae provided photons to be detected.

So, please, for the sake of clarity, can we choose 'now' to be the frame of reference where all objects simultaneously agree on their positions relative to each other?

And can we agree that when we detect photons, we are examining debris from an event that took place in the past as it exists now?

And that perception is an evolved device that 'contrives' a cause/effect relationship with otherwise unconnected events in order to either avoid future entanglement or to ensure it. For instance, a lion and an antelope might be in the same region. Two unconnected events. When the lion perceives the antelope, it tries to ensure entanglement by performing a successful hunt. Whereas the antelope would try to accomplish the opposite.

Same cause, different effect, perception.

Or would you say the distinction isn't important?

Morbert

Masteroid wrote: »

I got a bit lost here. How can 'roosh' and 'roosh + 5' have a light-cone each if both 'rooshes' are seperate events?

Each event in spacetime has an associated past and future cone.

Also, 'roosh' and 'roosh +5' are causally connected so what effects 'roosh' must also effect 'roosh +5'.

Yes, the worldline of an object with mass will always lie within its light cones. What affects you+0 must also affect you+5. But what affects you+5 doesn;t have to affect you+0.

And if the sun explodes 'NOW!', isn't roosh's destruction in the future cones of both the sun and roosh?

Yes

In fact, how is it even possible for the sun and roosh not to be in each other's light-cones?

Because the speed of light is finite. The sun exploding cannot affect any event on earth until the signal of the explosion reaches the earth.

The thing is, roosh is more than a photon being absorbed by an electron. That would be an event wouldn't it? And photons don't have light-cones.

Photons trace out the light cone structure of spacetime.

They can't. The universe is zero length and and the time between emission and absorption of a photon is zero. A photon does not have a future or a past because, in its own FoR, it didn't exist in the past or future.

The light cone structure is frame-independent. It is the causal structure of the universe. The length contraction from the perspective of any observer doesn't change anything.

What does that mean? That all photons exist 'now'?

I know there are a lot of question marks here but they are mostly rhetorical. My point is, where do you draw a line on roosh's history or future? Are not his great-great-great-great-grandparents in his past light-cone and are not his great-great-great-great-grandchildren not in his future one? Doesn't roosh's past light-cone extend all the way back to the big bang?

No lines are drawn. Here is an example of worldliness of two particles, one with mass, and one without.



You can see that the massive particle is always within its light cones. The massless particle's worldline traces out the light cone structure. It is impossible for any particle to travel outside its world lines, meaning the causality of events is constrained in this manner.

And therefore, don't all light-cones intersect?

With the exception of high spacetime curvature areas like a black hole, sure. But this just implies that, given enough time, the signals between two events can intersect, which is of course true

I brought this up before but it went without comment, there are two kinds of causal link, two types of experience. Being involved in a collision is not the same as observing a collision from a distance.

Similarly I pointed out that there are two distinct types of perception. There is the kind of perception that comes from observation through experience, being caught in an earthquake for example, and there is the kind of perception that comes from experience through observation where for example, you might see a news broadcast about people caught in an earthquake.

I think it is excessive to say the least to consider the kind of photonic interactions we've been discussing so far in relation to perception as creating a causal link between two events. They rather connect two seperate causal chains.

The gamma rays produced in a supernova are not the supernova, they are the debris that was created by a supernova. When we detect such gamma rays we do not directly observe a supernova, we deduce it. The supernova occured in the past of the gamma rays. The gamma rays are no more than a collection of data that partially describe the supernova.

The star that went supernova has its causal sequence and an observer of gamma rays so produced has his. But the progress of science does not depend on any particular supernova. Any will do for the purpose of observation.

And evolution recognises this. By being able to perceive the debris created by events, we can avoid the intersection of two seperate causal chains.

Or, roosh might be walking down the road when he sees a man wearing a hoodie walking toward him. Roosh might then cross the road.

Did the man in the hoodie cause roosh to cross the road or did roosh perceive the hoodie and cause himself to try and prevent a causal link from developing between them? The man in the hoodie may never even see roosh.

You could say that an emitted photon is the effect of a previous event and that absorption is the cause of a different and random later event.

Supernovae cause themselves to be seen and men cause themselves to look for them. There is no causal link between the two but our telescopes allow us to create 'pseudo-causal' links by pointing them in different directions until we detect unusual phenomena.

The supernova didn't cause the telescope and the telescope didn't cause the supernova, men caused telescopes and supernovae provided photons to be detected.

So, please, for the sake of clarity, can we choose 'now' to be the frame of reference where all objects simultaneously agree on their positions relative to each other?

And can we agree that when we detect photons, we are examining debris from an event that took place in the past as it exists now?

And that perception is an evolved device that 'contrives' a cause/effect relationship with otherwise unconnected events in order to either avoid future entanglement or to ensure it. For instance, a lion and an antelope might be in the same region. Two unconnected events. When the lion perceives the antelope, it tries to ensure entanglement by performing a successful hunt. Whereas the antelope would try to accomplish the opposite.

Same cause, different effect, perception.

Or would you say the distinction isn't important?

On a fundamental physical level, these are all meaningless distinctions. The earthquake caused you to react to it, even if there were events along the way. You are within the light cone of the earthquake in a matter of fractions of a second. c is a big number, and this is why the causal structure of the universe appears Newtonian on our tiny scale.

youi

I think time is just a Maya.
There is only a big dance of energy.


This video is good do ye think?

https://www.youtube.com/watch?v=WKsNraFxPwk

roosh

Morbert wrote: »

I'll answer both these questions together.

Let's use a more local example. Let's take the example of the sun exploding. Both "you" and "you plus five" would both be causally unconnected to the sun exploding. The explosion would not exist in the past or future light cone of "you" or "you plus five". All observers would agree that you would have to count to around 480 before the sun exploding would be in your past light cone (At which point, the sun exploding would have a causal influence on you, and a catastrophic one at that). You wouldn't say events not in the past or future light cones must necessarily be in the present though, unless you use a very unconventional definition of present.

Ok, if we use this more local example, we can examine the differences between the definitions of "past" and "future"; you're suggesting that an event only physically exists in an observers past once a photon reaches the observer; that is, the event only becomes part of their past light cone at that moment.

But, if we start with the premise that the universe consists of more than just ourselves; that is, for me, the universe consists of more than me; for you, it consists of more than you. This means that the sun exists and is spatially separated from you. That is, an extreme interpretation of solipsism is incorrect.

If the sun exists, then it exists in a shared "now" with you, as does the entire universe; this shared "now" is your present. If the sun explodes, then it does so in this shared "now".

Given the finite speed of light, if the sun explodes in your shared now, then by the time a photon from that event reaches you, the explosion event must necessarily be in what you and I would refer to as "the past"; indeed, it would be part of "the past" one second after the explosion occurs, even though light from it had not reached you yet. It may not have had a causal influence on you, but it would be "in the past".

Morbert

roosh wrote: »

Ok, if we use this more local example, we can examine the differences between the definitions of "past" and "future"; you're suggesting that an event only physically exists in an observers past once a photon reaches the observer; that is, the event only becomes part of their past light cone at that moment.

A slightly stronger criteria: Once a hypothetical particle travelling at the speed of light, capable of travelling through all obstacles, would have the possibility of travelling from the event to the observer. More rigorously, we say the event is in the past if there is a time like interval between them.

But, if we start with the premise that the universe consists of more than just ourselves; that is, for me, the universe consists of more than me; for you, it consists of more than you. This means that the sun exists and is spatially separated from you. That is, an extreme interpretation of solipsism is incorrect.

That's fine.

If the sun exists, then it exists in a shared "now" with you, as does the entire universe; this shared "now" is your present. If the sun explodes, then it does so in this shared "now".

Yes but what I call "now" is predicated on my frame of reference. Let's say, from my frame of reference, the sun explodes when my clock strikes 12. According to another observer, the sun has not yet exploded when my clock strikes 12. According to another, the sun has already exploded when my clock strikes 12. All observers will, however, agree that the blast will reach me and kill me when my clock strikes 12:08

Given the finite speed of light, if the sun explodes in your shared now, then by the time a photon from that event reaches you, the explosion event must necessarily be in what you and I would refer to as "the past"; indeed, it would be part of "the past" one second after the explosion occurs, even though light from it had not reached you yet. It may not have had a causal influence on you, but it would be "in the past".

According to one observer, the sun exploded when my clock struck 12:00:01. According to another, it happened when my clock struck 11:59:59. So it is true that, one second after 12:00:00, the explosion is in the past according to my reference frame. But according to others, it happens when my clock strikes some time in the future. It is only once my clock strikes 12:08:00 (roughly speaking) that all observers agree that the explosion is in my past.
I.e. There is no observer which would say the sun explodes after my clock strikes 12:08

roosh

Morbert wrote: »

A slightly stronger criteria: Once a hypothetical particle travelling at the speed of light, capable of travelling through all obstacles, would have the possibility of travelling from the event to the observer. More rigorously, we say the event is in the past if there is a time like interval between them.



That's fine.



Yes but what I call "now" is predicated on my frame of reference. Let's say, from my frame of reference, the sun explodes when my clock strikes 12. According to another observer, the sun has not yet exploded when my clock strikes 12. According to another, the sun has already exploded when my clock strikes 12. All observers will, however, agree that the blast will reach me and kill me when my clock strikes 12:08



According to one observer, the sun exploded when my clock struck 12:00:01. According to another, it happened when my clock struck 11:59:59. So it is true that, one second after 12:00:00, the explosion is in the past according to my reference frame. But according to others, it happens when my clock strikes some time in the future. It is only once my clock strikes 12:08:00 (roughly speaking) that all observers agree that the explosion is in my past.
I.e. There is no observer which would say the sun explodes after my clock strikes 12:08

OK, so the point seems to be that the arrival of the hypothetical particle at your location is when the explosion physically becomes part of your past. But if all observers agree that the particle arrives such at the moment your clock reads 12:08, would they not have to say that the explosion occurred before your clock struck 12:08, even if we assume the smallest possible spatial separation?

Just looking at it in this way, without recourse to specific reference frames; by the time the hypothetical particle has travelled half the distance from the sun to you - as measured by any reference frame - the explosion must necessarily be in the past; even by the time the particle has travelled a quarter of the distance the explosion must necessarily be in the past; by the time the particle has traveled 0.00001 of the distance the explosion must necessarily be in the past; and so on ad infinitum. That would mean that the explosion must necessarily be in the past before the hypothetical particle reaches you.

Morbert

roosh wrote: »

OK, so the point seems to be that the arrival of the hypothetical particle at your location is when the explosion physically becomes part of your past. But if all observers agree that the particle arrives such at the moment your clock reads 12:08, would they not have to say that the explosion occurred before your clock struck 12:08, even if we assume the smallest possible spatial separation?

Just looking at it in this way, without recourse to specific reference frames; by the time the hypothetical particle has travelled half the distance from the sun to you - as measured by any reference frame - the explosion must necessarily be in the past; even by the time the particle has travelled a quarter of the distance the explosion must necessarily be in the past; by the time the particle has traveled 0.00001 of the distance the explosion must necessarily be in the past; and so on ad infinitum. That would mean that the explosion must necessarily be in the past before the hypothetical particle reaches you.

This simply means the order of events is physical: I.e. The causal structure of events is the same for all observers. Everyone agrees the particle has travelled 0.00001 of the distance after the explosion and before the particle reaches earth, or 0.00002 of the distance, or 0.000010001 of the distance.

So the statement in blue is correct. But different reference frames will disagree over when the particle reaches half way, 0.00001 of the distance.

roosh

Morbert wrote: »

This simply means the order of events is physical: I.e. The causal structure of events is the same for all observers. Everyone agrees the particle has travelled 0.00001 of the distance after the explosion and before the particle reaches earth, or 0.00002 of the distance, or 0.000010001 of the distance.

So the statement in blue is correct. But different reference frames will disagree over when the particle reaches half way, 0.00001 of the distance.

The point being made though, was that the explosion event is only in the past when the hypothetical particle arrives at the observer, or was it that the explosion event is only in the past when the observers clock reads 12:08? Either way that can't be the case if the two events are spatially separated.

Morbert

roosh wrote: »

The point being made though, was that the explosion event is only in the past when the hypothetical particle arrives at the observer, or was it that the explosion event is only in the past when the observers clock reads 12:08? Either way that can't be the case if the two events are spatially separated.

It is the case. There are observers, for example, where the explosion happens after the earth observer's clock strikes 12:07, or :12:07.9999, or 12:07.999999999

roosh

Morbert wrote: »

It is the case. There are observers, for example, where the explosion happens after the earth observer's clock strikes 12:07, or :12:07.9999, or 12:07.999999999

Even for those reference frames, the explosion must be in the past prior to the clock striking 12:08.

Morbert

roosh wrote: »

Even for those reference frames, the explosion must be in the past prior to the clock striking 12:08.

Yes. That is what I have been saying. All observers agree that the explosion is in the past of 12:08.

countrynosebag

davej - thanks for finding that nugget!
deceptively simple 'chat' there
understood more, got confused more, understood more...........................
i agree there is now and that past and future do not exist but,,,,the linear thing just works for me - maybe i am just thick! how do you account for growth, entropy and decay if there is no time?
simple person needing simple explanations here, was he saying that we imagine our movement and perceptions to make all fit comfortably - need a lot of help with this little package.
anyone fancy pitching in - i just felt that saying that these concepts would neither be understood nor accepted for hundreds of years was the most telling and convincing thing said to convince me of exactly the opposite - rather like the nuns' telling me at school that life would be great when i am dead, and in this other place called heaven which we were just told was there too
of course i know and accept that things are happening at microscopic levels i cannot perceive with naked eye and the quantum area - muddled again here, is also talking about smaller particles, activity and even another activity being examined continuously but stuck again

roosh

Morbert wrote: »

Yes. That is what I have been saying. All observers agree that the explosion is in the past of 12:08.

Were you not saying that an event is only physically in the past the moment a hypothetical particle arrives at the observer? Presumably it must be, because there can be an infinite number of reference frames approaching the speed of light who say that the explosion occurs at 12:07:59.99999999999 recurring, and presumably the explosion can't be in the past at the moment it occurs, or while it is occuring.

Morbert

roosh wrote: »

Were you not saying that an event is only physically in the past the moment a hypothetical particle arrives at the observer? Presumably it must be, because there can be an infinite number of reference frames approaching the speed of light who say that the explosion occurs at 12:07:59.99999999999 recurring, and presumably the explosion can't be in the past at the moment it occurs, or while it is occuring.

Let be more explicit: The explosion is in the past of the earth clock reading 12:08. This is true for all frames of reference. However, the explosion is not always in the past of any earth clock reading before 12:08. For example "The explosion occurred after the earth clock reads 12:07" is true for some frames of reference.

roosh

Morbert wrote: »

Let be more explicit: The explosion is in the past of the earth clock reading 12:08. This is true for all frames of reference. However, the explosion is not always in the past of any earth clock reading before 12:08. For example "The explosion occurred after the earth clock reads 12:07" is true for some frames of reference.

This means that the explosion event is in the past, for one reference frame, the moment it is occurring; that is, it is simultaneously in the past and the present.

If the arrival of the particle at the earthbound clock, at 12:08, isn't the moment that the object is physically in the past, then it means that at some moment before the earthbound clock strikes 12:08 is when it is physically in the past; however, for any moment before the clock strikes 12:08 there is [hypothetically] a reference frame which says that the explosion occurs at that time reading on the earthbound clock; hence, it says that the event is in the present and the past.

Morbert

roosh wrote: »

This means that the explosion event is in the past, for one reference frame, the moment it is occurring; that is, it is simultaneously in the past and the present.

If the arrival of the particle at the earthbound clock, at 12:08, isn't the moment that the object is physically in the past, then it means that at some moment before the earthbound clock strikes 12:08 is when it is physically in the past; however, for any moment before the clock strikes 12:08 there is [hypothetically] a reference frame which says that the explosion occurs at that time reading on the earthbound clock; hence, it says that the event is in the present and the past.

You're not using terms consistently. I do not know what you mean when you say "the moment the object is physically in the past".

All observers will agree that the explosion happened before the clock on earth struck 12:08.

Not all observers will agree that the explosion happened before the clock on earth struck 12:07.

roosh

Morbert wrote: »

You're not using terms consistently. I do not know what you mean when you say "the moment the object is physically in the past".

You talked about the "physical past, present, and future", so there is a point where an event is physically in the past, present, or future, with regard to another event. In this case the events we are talking about are the explosion of the sun and the arrival of the hypothetical particle at the observer. You mentioned that the explosion event is only in the physical past of the observer at the moment the hypothetical particle arrives at the earth clock and observer, at the time of 12:08.

Morbert wrote: »

All observers will agree that the explosion happened before the clock on earth struck 12:08.

Not all observers will agree that the explosion happened before the clock on earth struck 12:07.

The point being made is that if the earth clock/observer and the sun are spatially separated, then the explosion must be in the physical past of the observer prior to 12:08, becuase the hypothetical particle only arrives at 12:08.

The issue is that, for all the times prior to 12:08, there is a hypothetical reference frame which says that the explosion happens at that time; that is, for every temporal value prior to 12:08, as read by the earth clock, there is a corresponding reference frame which notes that as the time of the explosion. This means that there will be a reference frame which says that the explosion occurs at some timme prior to 12:08 which corresponds to the point at which it is in the observers past; meaning that it simultaneously exists in the observers physical past and present.

Morbert

roosh wrote: »

You talked about the "physical past, present, and future", so there is a point where an event is physically in the past, present, or future, with regard to another event. In this case the events we are talking about are the explosion of the sun and the arrival of the hypothetical particle at the observer. You mentioned that the explosion event is only in the physical past of the observer at the moment the hypothetical particle arrives at the earth clock and observer, at the time of 12:08.

Yes.

The point being made is that if the earth clock/observer and the sun are spatially separated, then the explosion must be in the physical past of the observer prior to 12:08, becuase the hypothetical particle only arrives at 12:08.

The issue is that, for all the times prior to 12:08, there is a hypothetical reference frame which says that the explosion happens at that time; that is, for every temporal value prior to 12:08, as read by the earth clock, there is a corresponding reference frame which notes that as the time of the explosion. This means that there will be a reference frame which says that the explosion occurs at some timme prior to 12:08 which corresponds to the point at which it is in the observers past; meaning that it simultaneously exists in the observers physical past and present.

This is where your phrasing breaks down. What do you mean by observer here? Do you mean the observer at 12:08? 12:07? At any time prior to 12:08? If you mean the observer at any time before 12:08, then yes, there are observers who would not agree that the explosion is in the past. It is only at the 12:08 mark that all observers agree that the explosion is in the past.

From what I can gather, you're simply highlighting the fact that the explosion can be simultaneous with an observer's clock strike, according to one frame of reference, and in the past according to another. That is not a problem for the same reason all of your other thought experiments aren't problems. The hyperbolic spacetime geometry, as expressed in the Lorentz transformations, preserves the causal structure of the universe, leading to no paradoxes.

roosh

Morbert wrote: »

Yes.

This is where your phrasing breaks down. What do you mean by observer here? Do you mean the observer at 12:08? 12:07? At any time prior to 12:08? If you mean the observer at any time before 12:08, then yes, there are observers who would not agree that the explosion is in the past. It is only at the 12:08 mark that all observers agree that the explosion is in the past.

From what I can gather, you're simply highlighting the fact that the explosion can be simultaneous with an observer's clock strike, according to one frame of reference, and in the past according to another. That is not a problem for the same reason all of your other thought experiments aren't problems. The hyperbolic spacetime geometry, as expressed in the Lorentz transformations, preserves the causal structure of the universe, leading to no paradoxes.

What was meant by observer was the same as what was meant by observer above, to which you replied yes; although, I would agree that it isn't very clear.

It seems that the idea is that, when any observer shares their present moment with the earthbound clock at 12:08, the event is in their past, such that the event is in the physical past by the time the hypothetical particle arrives at the clock at 12:08.

As was mentioned, however, the event must be in the physical past at some point prior to 12:08, because the clock and the sun are spatially separated; by the time the particle has traveled half the distance the explosion is in the past - this is true for every reference frame - and the clock has not yet struck 12:08; this is also true for when the particle has traveled 99.999% of the distance. So, every observer would have to agree that the explosion is in the past at some point before the clock strikes 12:08.

There will be one hypothetical reference frame which says that the explosion occurs when the earth clock reads 12:07:59.99999999 (recurring). When the particle has traveled half the distance, the clock still will not have struck 12:08, it will still be on 12:07:59.99999999; the same is true when the particle has traveled 99.99999% of the distance. That reference frame will have to agree that the explosion is in the past and the present at the same moment.



How does the concept of the physical present work?

Morbert

roosh wrote: »

What was meant by observer was the same as what was meant by observer above, to which you replied yes; although, I would agree that it isn't very clear.

It seems that the idea is that, when any observer shares their present moment with the earthbound clock at 12:08, the event is in their past, such that the event is in the physical past by the time the hypothetical particle arrives at the clock at 12:08.

Yes.

As was mentioned, however, the event must be in the physical past at some point prior to 12:08, because the clock and the sun are spatially separated; by the time the particle has traveled half the distance the explosion is in the past - this is true for every reference frame - and the clock has not yet struck 12:08; this is also true for when the particle has traveled 99.999% of the distance. So, every observer would have to agree that the explosion is in the past at some point before the clock strikes 12:08.

Yes.

There will be one hypothetical reference frame which says that the explosion occurs when the earth clock reads 12:07:59.99999999 (recurring). When the particle has traveled half the distance, the clock still will not have struck 12:08, it will still be on 12:07:59.99999999; the same is true when the particle has traveled 99.99999% of the distance. That reference frame will have to agree that the explosion is in the past and the present at the same moment.

No. According to this reference frame, it will not still be on 12:07.99999999 when the particle reaches half way. It will instead be on 12:07.999999995. If by 12:07.99999999, you meant 9 recurring, then that is simply 12:08. There is no frame of reference (unless you jerry-rig one for the photon, which doesn't work) which says the explosion happened at 12:07.9999999... i.e. 12:08.

roosh

Morbert wrote: »

Yes.

Yes.

No. According to this reference frame, it will not still be on 12:07.99999999 when the particle reaches half way. It will instead be on 12:07.999999995. If by 12:07.99999999, you meant 9 recurring, then that is simply 12:08. There is no frame of reference (unless you jerry-rig one for the photon, which doesn't work) which says the explosion happened at 12:07.9999999... i.e. 12:08.

Is there a limit to the number of decimal places?


Also, how does the concept of the physical present work?

Morbert

roosh wrote: »

Is there a limit to the number of decimal places?

No.

http://en.wikipedia.org/wiki/0.999...

Also, how does the concept of the physical present work?

I don't understand the question. Two events are labelled simultaneous if they have the same coordinate time. This is frame-dependent and not physical.

roosh

Morbert wrote: »

No.

http://en.wikipedia.org/wiki/0.999...

cool! I hadn't come across that before.

I'm not sure it would work for a clock though, assuming we can postulate an infinitely precise clock, because a counter at 12:07:59.(9) would not be the same as a counter at 12:08; would that bring us to the idea of the duration of a moment I wonder?

Morbert wrote: »

I don't understand the question. Two events are labelled simultaneous if they have the same coordinate time. This is frame-dependent and not physical.

Does this mean we have a physical past and a physical future, but no physical present?

Morbert

roosh wrote: »

cool! I hadn't come across that before.

I'm not sure it would work for a clock though, assuming we can postulate an infinitely precise clock, because a counter at 12:07:59.(9) would not be the same as a counter at 12:08; would that bring us to the idea of the duration of a moment I wonder?

That's an engineering matter, and not at all relevant to the thread.

Does this mean we have a physical past and a physical future, but no physical present?

In the block universe you have a 4D structure of all events. There is no holistic past present and future. Instead, we same some events are physically in the past or future of other events. The present, physically speaking, is local to single events. I.e. An event is in the present of itself. But there is no meaningful physical present between events that are causally unconnected. In relativity, the fundamental entities are events and their causal structure.

roosh

Morbert wrote: »

That's an engineering matter, and not at all relevant to the thread.

OK, there's no point in labouring it any further so.

Morbert wrote: »

In the block universe you have a 4D structure of all events. There is no holistic past present and future. Instead, we same some events are physically in the past or future of other events. The present, physically speaking, is local to single events. I.e. An event is in the present of itself. But there is no meaningful physical present between events that are causally unconnected. In relativity, the fundamental entities are events and their causal structure.

If you don't mind I'd like to explore this a little further; I don't have a conclusion in mind, I just want to see where the reasoning leads.

I suppose an issue I have trouble with is the idea that an event can physically be in the past of another event, or it can physically be in the future of another event, but it can never physically be in the present of it; also that it is possible for an event to be in neither of those "locations" with respect to another event.

If we look at it in terms of the present being local to single events, and that an event is in the present of itself:
If an event is in the present of itself, physically speaking, and there are physically separated regions of the universe, where other events occur, then those events must be in the present of each other, such that the present isn't simply local to single events; that is, an event is not only in the present of itself. Looking at it in the negative sense seems somewhat questionable; physically speaking, no event is in the present of any other event.


If we have 2 observers at rest relative to each other, in regions of the universe very distant from each other, will those observers be in the present of each other, physically speaking?

Morbert

If you don't mind I'd like to explore this a little further; I don't have a conclusion in mind, I just want to see where the reasoning leads.

Ok, but forgive me if I am a little suspicious of the above claim. In previous threads, I have repeatedly watched open and honest questions slowly morph into incorrect assertions.

I suppose an issue I have trouble with is the idea that an event can physically be in the past of another event, or it can physically be in the future of another event, but it can never physically be in the present of it; also that it is possible for an event to be in neither of those "locations" with respect to another event.

If we look at it in terms of the present being local to single events, and that an event is in the present of itself:
If an event is in the present of itself, physically speaking, and there are physically separated regions of the universe, where other events occur, then those events must be in the present of each other, such that the present isn't simply local to single events; that is, an event is not only in the present of itself. Looking at it in the negative sense seems somewhat questionable; physically speaking, no event is in the present of any other event.

The statement in blue is the problematic one.

Scour your brain of all preconceptions, and try build your image of the block universe from scratch. You can reject the metaphysics later if you wish, but for the time being, let's start from the beginning.

Let's start with events. These events currently have no causal relation defined because we have not given them one yet, and hence we have no past present or future, so let's do that now. First, let's give them a Newtonian causal relation. I.e. Let us suppose there is no speed limit to the propagation of signals through which one event can be said to affect another. We have "instantaneous effects" at a distance. From this, we can build a picture of relation between all events where every event has a "past" consisting of all events that can affect it, a "future" consisting of all events it can affect, and a "present" consisting that all events that would be connected by an "instantaneous" signal.

But now let's give events a relativistic causal structure. Now, signals can't travel faster than a given speed, so there are now events separated in space that cannot be causally connected because no signal can pass between them. Now, what physical meaning is there to saying an event is in the present of another? Since there can be no physical connection, no physical causal relation between the events, there is no compulsion to order the events, or to label them as simultaneous or non-simultaneous.

If we have 2 observers at rest relative to each other, in regions of the universe very distant from each other, will those observers be in the present of each other, physically speaking?

Not necessarily. For example, you can have a case where, according to one observer, both observers are alive, and according to the other observer, only he/she is alive.

roosh

Morbert wrote: »

Ok, but forgive me if I am a little suspicious of the above claim. In previous threads, I have repeatedly watched open and honest questions slowly morph into incorrect assertions.

Understandable, although I would disagree with the idea that all of the assertions are incorrect. Those other threads usually start out from a "suspicion" and develop; in this case, there is no "suspicion". That's not to say that, as the picuture builds there won't be questions or challenges along the way.

Morbert wrote: »

The statement in blue is the problematic one.

Scour your brain of all preconceptions, and try build your image of the block universe from scratch. You can reject the metaphysics later if you wish, but for the time being, let's start from the beginning.

Let's start with events. These events currently have no causal relation defined because we have not given them one yet, and hence we have no past present or future, so let's do that now. First, let's give them a Newtonian causal relation. I.e. Let us suppose there is no speed limit to the propagation of signals through which one event can be said to affect another. We have "instantaneous effects" at a distance. From this, we can build a picture of relation between all events where every event has a "past" consisting of all events that can affect it, a "future" consisting of all events it can affect, and a "present" consisting that all events that would be connected by an "instantaneous" signal.

But now let's give events a relativistic causal structure. Now, signals can't travel faster than a given speed, so there are now events separated in space that cannot be causally connected because no signal can pass between them. Now, what physical meaning is there to saying an event is in the present of another? Since there can be no physical connection, no physical causal relation between the events, there is no compulsion to order the events, or to label them as simultaneous or non-simultaneous.

Part of the issue I have is with the idea of the present consisting of events which have a causal influence on each other; obviously, for each individual, their present moment, or now slice, is made up of events which don't have a causal influence on them.

It might be helpful to look at this from both the perspectives of Minkowskian spacetime and presentism, given that relativity is compatible with both. We have the Minkowskian interprtetation which says that there is no physical meaning of one event being in the present of another. But if we look at things from the perspective of presentism, and through the lens of a finite speed for the propagation of signals, then we have events which don't have a causal influence on each other but which are in the present of each other.

We wouldn't say that they are in the "physical present" because there is no physical thing called "the present", but events would be in the present of each other.

Morbert wrote: »

Not necessarily. For example, you can have a case where, according to one observer, both observers are alive, and according to the other observer, only he/she is alive.

Would gravitational time dilation be the explanation in that case?

Morbert

roosh wrote: »

Part of the issue I have is with the idea of the present consisting of events which have a causal influence on each other; obviously, for each individual, their present moment, or now slice, is made up of events which don't have a causal influence on them.

It might be helpful to look at this from both the perspectives of Minkowskian spacetime and presentism, given that relativity is compatible with both. We have the Minkowskian interprtetation which says that there is no physical meaning of one event being in the present of another. But if we look at things from the perspective of presentism, and through the lens of a finite speed for the propagation of signals, then we have events which don't have a causal influence on each other but which are in the present of each other.

We wouldn't say that they are in the "physical present" because there is no physical thing called "the present", but events would be in the present of each other.

This is why I said scour your brain. You are introducing your intuitive notion of present for which there is no physical compulsion to adopt. The physical, fundamental stuff of the universe would be events and their causal structure.

Would gravitational time dilation be the explanation in that case?

No. You don't need to suppose any curvature.

roosh

Morbert wrote: »

This is why I said scour your brain. You are introducing your intuitive notion of present for which there is no physical compulsion to adopt. The physical, fundamental stuff of the universe would be events and their causal structure.

As part of the explanation you posed the question

Morbert wrote: »

Now, what physical meaning is there to saying an event is in the present of another? Since there can be no physical connection, no physical causal relation between the events

I'm just using that example of the present moment to address that question, and to explore the concept of events physically being in the present of each other.

On the one hand you are saying that because events don't have causal influence on each other we can't really say that they are physically in the present of each other, or that there is no compulsion to; but if we look at it through the lens of presentism, would we say that events, which are spatially separated and have no causal influence on each other, are physically in the present of each other?

Morbert wrote: »

No. You don't need to suppose any curvature.

Oh, OK. How does it work?

Morbert

roosh wrote: »

As part of the explanation you posed the question

I'm just using that example of the present moment to address that question, and to explore the concept of events physically being in the present of each other.

On the one hand you are saying that because events don't have causal influence on each other we can't really say that they are physically in the present of each other, or that there is no compulsion to; but if we look at it through the lens of presentism, would we say that events, which are spatially separated and have no causal influence on each other, are physically in the present of each other?

This brings me back to an earlier point I made. Such a definition of the present would be wholly at odds with presentism. A distant alien's entire life history could be causally unconnected to a moment in your lifetime. Therefore, by the definition above, the history of the alien would all be in your "present".

Oh, OK. How does it work?

http://imgur.com/qv29or2

In the Newtonian picture, the cones are flat, since there is no limit to the speed of light. All coordinate systems therefore obey galilean transformation rules, and hence agree on simultaneity. In the Einsteinian picture, the cones are not flat, so there is no agreement between coordinate frames. Even the way I have drawn it tacitly assumes a coordinate system. I could have drawn it another, equally valid way.

roosh

Morbert wrote: »

This brings me back to an earlier point I made. Such a definition of the present would be wholly at odds with presentism. A distant alien's entire life history could be causally unconnected to a moment in your lifetime. Therefore, by the definition above, the history of the alien would all be in your "present".

The present wouldn't simply be defined as events which have no causal influence on each other are in the present of each other, it would just be possible that events which are causally unconnected to be in the present of each other.

If you take your particular now slice, then, according to you, there are events which are spatially separated and therefore causally unconnected, which are in your present. Other spatially separated events which immediately preceded those events, would be in your past.

Morbert wrote: »

http://imgur.com/qv29or2

In the Newtonian picture, the cones are flat, since there is no limit to the speed of light. All coordinate systems therefore obey galilean transformation rules, and hence agree on simultaneity. In the Einsteinian picture, the cones are not flat, so there is no agreement between coordinate frames. Even the way I have drawn it tacitly assumes a coordinate system. I could have drawn it another, equally valid way.

How is it though, that for two observers at rest relative to each other, one would say that both are alive, while the other says that only they are alive?

Morbert

roosh wrote: »

The present wouldn't simply be defined as events which have no causal influence on each other are in the present of each other, it would just be possible that events which are causally unconnected to be in the present of each other.

If you take your particular now slice, then, according to you, there are events which are spatially separated and therefore causally unconnected, which are in your present. Other spatially separated events which immediately preceded those events, would be in your past.

Yes, they would be in the past according to your coordinate definition of "present". But that is a different definition from "Not in your future or past light cone".

How is it though, that for two observers at rest relative to each other, one would say that both are alive, while the other says that only they are alive?

The dotted lines are the coordinate presents of the two hypothetical observers. Note that one line crosses the history of both observers, while the other only crosses one. The entire worldline of the observer on the right is "underneath" the coordinate present of (i.e. In the coordinate past of) the observer on the left.

roosh

Morbert wrote: »

Yes, they would be in the past according to your coordinate definition of "present". But that is a different definition from "Not in your future or past light cone".

OK, but just looking at the idea of being "physically in the present of other events"; if presentism were indeed the correct state of the universe, would event A, which is spatially separated from event B, be physically in the present of event B?

Morbert wrote: »

The dotted lines are the coordinate presents of the two hypothetical observers. Note that one line crosses the history of both observers, while the other only crosses one. The entire worldline of the observer on the right is "underneath" the coordinate present of (i.e. In the coordinate past of) the observer on the left.

Would two observers at rest relative to each other not have the same co-ordinate present, or now slice?

Morbert

roosh wrote: »

OK, but just looking at the idea of being "physically in the present of other events"; if presentism were indeed the correct state of the universe, would event A, which is spatially separated from event B, be physically in the present of event B?

I don't know which events you are talking about. If presentism is the correct state of the universe, then we have Newtonian and Galilean relations between space and time. All observers would agree on what events are simultaneous, which would permit a global definition of "the present" where arbitrarily separated events A and B could be in the present.

Would two observers at rest relative to each other not have the same co-ordinate present, or now slice?

Yes. These two observers would be moving, relative to one another.

roosh

Morbert wrote: »

I don't know which events you are talking about. If presentism is the correct state of the universe, then we have Newtonian and Galilean relations between space and time. All observers would agree on what events are simultaneous, which would permit a global definition of "the present" where arbitrarily separated events A and B could be in the present.

To clarify what events I mean; take your now slice; if presentism is correct, then there are events happening in a distant galaxy which are spatially separated from you, which have no causal influence on you, but which are in your present. Would these events be considered to be physically in your present?

With regard to agreeing on the simultaneity of events, we would still have the disagreement over the time co-ordinates of events, and perhaps a disagreement over whether or not two events were simultaneous, except with the idea that one observer could be wrong.

Morbert wrote: »

Yes. These two observers would be moving, relative to one another.

Sorry, I'm not clear on that. Would two observers at rest relative to each other have the same co-ordinate present; that is, their dotted lines would co-incide?

Is the picture you posted of two relatively moving observers?

Morbert

roosh wrote: »

To clarify what events I mean; take your now slice; if presentism is correct, then there are events happening in a distant galaxy which are spatially separated from you, which have no causal influence on you, but which are in your present. Would these events be considered to be physically in your present?

Yes.

Sorry, I'm not clear on that. Would two observers at rest relative to each other have the same co-ordinate present; that is, their dotted lines would co-incide?

Is the picture you posted of two relatively moving observers?

Yes to both questions.

roosh

Morbert wrote: »

Yes.

Why would the same not be true, then, for the block universe?

Morbert wrote: »

Yes to both questions.

Ah, OK, I think we were at cross purposes there; I was wondering about two observers at rest relative to each other; but the point was geared towards the same answer as above i.e. determining if events can be physically in the present of each other.

Morbert

roosh wrote: »

Why would the same not be true, then, for the block universe?

The issue isn't the block universe per se. You could have a block universe with a Newtonian null cone structure, where transformations between reference frames are galilean, and a global present exists. But if you do this, then the speed of light would no longer be the same for all observers unless you postulate some special dynamics that work to bend and stretch apparatus so that all observers mistakenly measure the speed of light to be c.

roosh

Morbert wrote: »

The issue isn't the block universe per se. You could have a block universe with a Newtonian null cone structure, where transformations between reference frames are galilean, and a global present exists. But if you do this, then the speed of light would no longer be the same for all observers unless you postulate some special dynamics that work to bend and stretch apparatus so that all observers mistakenly measure the speed of light to be c.

Sorry, I was referring more to the Minkowskian version of the block universe.

Morbert

roosh wrote: »

Sorry, I was referring more to the Minkowskian version of the block universe.

Unlike a Newtonian spacetime, coordinate systems on Minkowski space do not agree on simultaneity. There is nothing in the structure that would allow you to declare one coordinate present as more physical than another.

PeterKieran

Clocks are controlled by their individual mechanisms. Time is a construct of man. No other creature

random.stranger

roosh wrote: »

Personally I believe that time does not exist, that it is merely a figment of the imagination of mankind, and our subsequent belief that it is an external force acting in the universe, makes it, by definition, an illusion.

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TLDR

Do you have broadband & if so: why?