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Author Topic:   How is the Universe here?
Stile
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Posts: 3849
From: Ontario, Canada
Joined: 12-02-2004
Member Rating: 1.6


Message 31 of 131 (487172)
10-28-2008 11:29 AM
Reply to: Message 19 by cavediver
10-27-2008 4:11 PM


Future and Past Ramblings
I'm just going to ramble a bit and hopefully not be too wrong.

This whole idea of light-cones and relative 'future' and 'past'... is it okay if I think of it as sort of... the doppler effect with light as opposed to sound?

That is, something can happen on the sun, and someone on Mercury will see it "first", and someone on earth will see it "second", even though it's the same event.

Or does this sort of ordered-flow screw up thinking later down the road? A decent analogy for now, but it will only make things harder later?

And I would like to try and parse this a bit:

cavediver writes:

So what about an eruption on the Sun's surface 4 minutes ago? That cannot affect us *now*. So it is not in our past But nor is it in our future. We say that it is 'elsewhere', because us phsyicists think that sounds cool.

That cannot affect us *now*.
-as in... that cannot affect us until the light photons from the event cross paths with us.
-as far as the example goes... we cannot 'be startled' by the eruption on the sun exactly when it happens, because we don't even know that it occurred until 8 min after it actually happened.

We say that it is 'elsewhere'...
-as in... this is something that, basically, the light photons from the event may (or may not...) at some point cross into our future light cone, and therefore become our "now". At which point, we can be affected by it.

So it is not in our past
-right, because we haven't detected it yet, the light photons are only halfway between the sun and the earth

But nor is it in our future
-I don't understand this. Do you mean it's not necessarily in our future? As in... we could not detect the explosion for some reason (say we're sleeping)?
-if the explosion occured, and we're watching it with our telescope, and we are going to see it, when the photons reach earth... how is it not in our future?

But *elsewhere* events cannot influence me *now*, so even though I think the explosion occured 4 minutes before I clap my hands, there's nothing wrong with someone else thinking that it happened four minutes AFTER I clapped my hands. And that may well be what they see if they are travelling at an appropriate speed and direction relative to me and the Sun.

But *elsewhere* events cannot influence me *now*
-right, because we have yet to detect them. There isn't even a chance for us to detect them because the photons haven't reached us yet.

so even though I think the explosion occured 4 minutes before I clap my hands
-because when we finally see the explosion, we know that we clapped our hands 4 min. ago, and that it take 8 min. for light to travel to us from the sun?

there's nothing wrong with someone else thinking that it happened four minutes AFTER I clapped my hands. And that may well be what they see if they are travelling at an appropriate speed and direction relative to me and the Sun.
-because they just saw the explosion and don't know it took 8 min. for the light to travel to earth?
-Or is this not what you meant, and you're implying something about someone going very fast (and not on earth) and so their sense of time is different from ours on earth?

quote:
That is, something can happen on the sun, and someone on Mercury will see it "first", and someone on earth will see it "second", even though it's the same event.

I think I'm beginning to see the problem with thinking this way. This way kind of includes some implied "standard time" of the universe, which doesn't really exist.

It's not so much that the even happend, and Mecury saw it 'first' and Earth saw it 'second' so much that:

An event happened.
Mercury detected the event 4 min. after the event happened.
Earth detected the event 8 min. after the event happened.

This way there's no restrictions, and no implied foundational time-line.

I still find the 'doppler effect with time instead of sound' to be helpful to myself, but I will have to focus on remembering that everything has it's own independent, um... timeline.


This message is a reply to:
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AdminNosy
Administrator
Posts: 4754
From: Vancouver, BC, Canada
Joined: 11-11-2003


Message 32 of 131 (487173)
10-28-2008 11:30 AM
Reply to: Message 30 by New Cat's Eye
10-28-2008 11:11 AM


Uncalled for
CS, that isn't necessary. CFO will not be allowed to interfere here.

This message is a reply to:
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New Cat's Eye
Inactive Member


Message 33 of 131 (487178)
10-28-2008 12:07 PM
Reply to: Message 31 by Stile
10-28-2008 11:29 AM


Re: Future and Past Ramblings
-if the explosion occured, and we're watching it with our telescope, and we are going to see it, when the photons reach earth... how is it not in our future?

Because the event has already happened.

there's nothing wrong with someone else thinking that it happened four minutes AFTER I clapped my hands. And that may well be what they see if they are travelling at an appropriate speed and direction relative to me and the Sun.
-because they just saw the explosion and don't know it took 8 min. for the light to travel to earth?
-Or is this not what you meant, and you're implying something about someone going very fast (and not on earth) and so their sense of time is different from ours on earth?

Its the latter. They need both the appropiate speed and direction.....


This message is a reply to:
 Message 31 by Stile, posted 10-28-2008 11:29 AM Stile has responded

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onifre
Member (Idle past 1242 days)
Posts: 4854
From: Dark Side of the Moon
Joined: 02-20-2008


Message 34 of 131 (487181)
10-28-2008 12:31 PM
Reply to: Message 31 by Stile
10-28-2008 11:29 AM


Re: Future and Past Ramblings
Hi Stile'

I think I'm beginning to see the problem with thinking this way. This way kind of includes some implied "standard time" of the universe, which doesn't really exist.

I believe the standard time would be *now*, but now is relative to the observer.

It's not so much that the even happend, and Mecury saw it 'first' and Earth saw it 'second' so much that:

This would depend on who is making the observation. I believe the example was given from an Earth PoV making us second in the timeline from the event. But, of course this would mean that we knew the event took place, which we couldn't until the light reaches us. First and second would be assigned in hindsight after both Mercury and Earth report when they saw the event take place.

*Note: I don't think im having the same brain-fart I did yesterday that forced me to place a Lorentz transformation to my own example when it had nothing to do with my example! My appologies for that yesterday. I believe what im explaining now is accurate, if not im sure I'll be corrected.;)


"All great truths begin as blasphemies"

"I smoke pot. If this bothers anyone, I suggest you look around at the world in which we live and shut your mouth."--Bill Hicks

"I never knew there was another option other than to question everything"--Noam Chomsky


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Stile
Member
Posts: 3849
From: Ontario, Canada
Joined: 12-02-2004
Member Rating: 1.6


Message 35 of 131 (487195)
10-28-2008 1:43 PM
Reply to: Message 33 by New Cat's Eye
10-28-2008 12:07 PM


Re: Future and Past Ramblings
Catholic Scientist writes:

Because the event has already happened.

Okay, I understand then. This was more of a terminology issue then a concept issue.

Seeing the explosion may be in my future (in a destiny sort of sense), but the event itself is not in the future, because it's already happened. I understand that.

Its the latter. They need both the appropiate speed and direction....

I think I understand this as well. Say they are travelling at some sufficient speed and direction that they "see" the clap from earth 4 min. after they "see" the explosion on the sun? I can visualize that, if the answer is yes. Or am I still not understanding the concept?


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Stile
Member
Posts: 3849
From: Ontario, Canada
Joined: 12-02-2004
Member Rating: 1.6


Message 36 of 131 (487198)
10-28-2008 2:01 PM
Reply to: Message 33 by New Cat's Eye
10-28-2008 12:07 PM


Re: Future and Past Ramblings
Catholic Scientist writes:

Stile writes:

if the explosion occured, and we're watching it with our telescope, and we are going to see it, when the photons reach earth... how is it not in our future?

Because the event has already happened.

Wait... if what you say is true, then no one really has any "future" whatsoever. Since everything happens in some sort of "elsewhere" (no matter how miniscule) before the light photons hit our eyes and we detect the event.

Whether it's an explosion on the sun, and it takes 8 min for the light to reach us.
Or it's an explosion right in front of us, and it takes 0.0000023whatever seconds for the light to reach us.

If what you say is true, neither case is in "our future" because the events happened before we saw them. Therefore, nothing at all is in "our future" because all events take some amount of time for us to detect them.

So, if that's true, what is meant by the "future" light cone?

That is, if I can't say that light from an explosion on the sun is in our future (if I'm eventually going to see it), what can we say is actually in the future light cone?

Or is that the catch? I can say that the "light" from the event is in our future, but not the event itself?

If so, then that's some more terminology confusion I just needed to understand, and that fits the concept I already have.

This would make sense... hence the term "future light cone" :)


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Replies to this message:
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bluescat48
Member (Idle past 2481 days)
Posts: 2347
From: United States
Joined: 10-06-2007


Message 37 of 131 (487204)
10-28-2008 2:49 PM
Reply to: Message 36 by Stile
10-28-2008 2:01 PM


Re: Future and Past Ramblings
Or is that the catch? I can say that the "light" from the event is in our future, but not the event itself?

The event is relative to which point is being taken. The event happened in the past but to us the event is futuristic ie:

Suppose a star went supernova in 1509 CE the star is 500 light years away so we wont see the event until some time in 2009. The event happened 499 years ago but to us it will have happened in 1909 when the photons reach us. Relative to us the event hasn't occurred.


There is no better love between 2 people than mutual respect for each other WT Young, 2002

Who gave anyone the authority to call me an authority on anything. WT Young, 1969


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petrophysics1
Inactive Member


Message 38 of 131 (487212)
10-28-2008 4:00 PM
Reply to: Message 37 by bluescat48
10-28-2008 2:49 PM


Re: Future and Past Ramblings
Suppose a star went supernova in 1509 CE the star is 500 light years away so we wont see the event until some time in 2009. The event happened 499 years ago but to us it will have happened in 1909 when the photons reach us. Relative to us the event hasn't occurred.

bluescat48;

Not to pick on you, but I don't see how your and others explainations are anything other than Newtonian physics. It appears your explaination contains a "universal time" or a "universal now", and then you proceed foward to say it did happen then, but for you and your PoV only when you noticed it.

No problem, but I don't see, like cavediver said, how this makes time a dimension like space. Your example and the others about the Sun are just like 3 guys hunting in a field. If someone shoots, the "now" for each is different based on the speed of sound. This is no big deal.

Somehow, I think there is a bit more going on here, as I think this simple explaination has been known for a long time.

If time is a dimension, should we be able to move through it like we can space?

Maybe cavediver can clarify, as I'm looking to understand in a practical sense what TIME being a dimension means.The explainations I've seen here would be no different than relating "time" to the speed of sound.

Don't you think so?

Best regards

Petro


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petrophysics1
Inactive Member


Message 39 of 131 (487216)
10-28-2008 4:25 PM


Just a general note, I said this above:

Maybe cavediver can clarify, as I'm looking to understand in a practical sense what TIME being a dimension means.The explainations I've seen here would be no different than relating "time" to the speed of sound.

I did not mean to include cavediver's example of two people, one seeing A before B, and the other seeing B before A, with the light cones.

Although I can see it,I'm still thinking about it.

At least in a practical sense.

Edited by petrophysics1, : typo


  
V-Bird
Member (Idle past 3877 days)
Posts: 211
From: Great Britain
Joined: 03-22-2004


Message 40 of 131 (487229)
10-28-2008 6:32 PM
Reply to: Message 38 by petrophysics1
10-28-2008 4:00 PM


Re: Future and Past Ramblings
"If time is a dimension, should we be able to move through it like we can space?

Maybe cavediver can clarify, as I'm looking to understand in a practical sense what TIME being a dimension means.The explainations I've seen here would be no different than relating "time" to the speed of sound."

We do move through time but the movement is processional, time is a dimension that is a consequence of motion motion of anykind follows from the previous 'snapshot' moment of stasis.

Space is an adjective, it describes, it is not a noun for something that has substance, space is simply the gaps between things and the same applies to time, that is what a dimension is, you cannot manipulate dimensions, because dimensions are defined co-ordinates and that applies to time as well.

All four dimensions are merely measurements, they measurements in increments we have standardised so as to make sense of the Cosmos we are part of.

But both space and time are not in themselves 'things'.

The speed of sound is simply a threshold given to us by air density and velocity, the latter is made 'sense' of by the use of 2 of the 4 dimensions 760[miles] per [hour] another way to say this is Mach 1, to the sound or the threshold the units we choose to define the event are our own and have no bearing on the base physical properties of the air in which the event happens.

I am not sure that my answer will be sufficiently satisfactory to you but an event is something completely different to a dimension, we need dimensions to describe an event to one another but that is all that dimensions can be used for, they are a conceptual tool.

We cannot truly manipulate any of the dimensions except by changing the increments or their names, 1 inch is 2.54cms.


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onifre
Member (Idle past 1242 days)
Posts: 4854
From: Dark Side of the Moon
Joined: 02-20-2008


Message 41 of 131 (487258)
10-29-2008 8:48 AM
Reply to: Message 38 by petrophysics1
10-28-2008 4:00 PM


Re: Future and Past Ramblings
Hi Petrophysics1,

Not to pick on you, but I don't see how your and others explainations are anything other than Newtonian physics. It appears your explaination contains a "universal time" or a "universal now", and then you proceed foward to say it did happen then, but for you and your PoV only when you noticed it.

The example bluecat and I gave about the Sun works fine with Newtonian physics because its within our solar system where space is static. I can't speak for bluecat but my explanation was just so johnfultron understood how one event could be considered past, present and future, without over complicating my explanation.

Cavedivers example of 2 moving references does get us into special relativity where time IS different for the 2 frames of reference.


"All great truths begin as blasphemies"

"I smoke pot. If this bothers anyone, I suggest you look around at the world in which we live and shut your mouth."--Bill Hicks

"I never knew there was another option other than to question everything"--Noam Chomsky


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johnfolton 
Suspended Member (Idle past 3883 days)
Posts: 2024
Joined: 12-04-2005


Message 42 of 131 (487263)
10-29-2008 9:43 AM
Reply to: Message 41 by onifre
10-29-2008 8:48 AM


Spacetime dilation?
I can't speak for bluecat but my explanation was just so johnfultron understood how one event could be considered past, present and future, without over complicating my explanation.

I took your explanation as a good explanation of the present not the past or future.

I think what your all talking about is spacetime dilation like a photon not aging giving us a picture of the early universe yet the photon itself has not aged. Or if your travelling thru space at the speed of a photon you would not age as fast as your twin on earth, etc...

Like if the earth is stretching spacetime at a faster rate than a photon and the space between the galaxies is being stretching at an even faster rate than the earth you could have the entire universe being created only 6,000 years ago and the earth only 13,000 years ago: right? Which is likely why the galaxies all show they are still wound up (right?) no matter what the distance from the earth the galaxies are all spiraled evidence of a young universe(right?) apparently is this not due spacetime dilation stretching greater between the galaxies than the rate of space time dilation of the stars themselves (right?), as the stars in the galaxies unfold the greater space distances between the galaxies for the unfolding of the galaxies in to the space created by space dilation and the greater distances for the photon to be travelling thru space.

P.S. I guess I always thought space curvature is more a part of the present becoming the past going to the future about how this curved dimension inward is how the very fabric of space time is moving the earth/sun forward in time faster than the photon is moving forward in time not space, etc... As far as your light cones in a flat straight disk like universe is not the light cones straight not curved so you can not share an happening going backwards in time? and anything going forward in time is not about a happening going backwards so your cones are nothing but how space dilation disects forward at different rates thru time. right? Now a black hole are the light cones curved going backwards in time or are they going forward thru time? as the universe is a flat disc shape, etc...

Does it make more sense that the entire universe was created by Bose-Einstein condensate principles instead of big bang principles, etc...Like granites appearing to of formed suddenly more of from a Bose-Einstein condensate like a seed from which galaxies formed suddenly in thousands of our years not billions of years as you need from a big bang senerio, etc...

http://74.125.45.104/search?q=cache:wf8v4aHRD8kJ:moriond.in2p3.fr/J04/proceedings/morikawa.pdf.gz+bose-einstein+condensate+seeds+of+the+universe&hl=en&ct=clnk&cd=2&gl=us

Edited by johnfolton, : No reason given.

Edited by johnfolton, : No reason given.

Edited by johnfolton, : No reason given.

Edited by johnfolton, : No reason given.

Edited by johnfolton, : No reason given.


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New Cat's Eye
Inactive Member


Message 43 of 131 (487264)
10-29-2008 9:46 AM
Reply to: Message 36 by Stile
10-28-2008 2:01 PM


Re: Future and Past Ramblings
if what you say is true, then no one really has any "future" whatsoever.

Considering that time is another dimension and that the Universe has a 4D "shape" that we just happen to be experiencing a "slice" of, I could probably argue against there being any future.

Since everything happens in some sort of "elsewhere" (no matter how miniscule) before the light photons hit our eyes and we detect the event.

But what about things that haven't happened yet? They would still be in the fitire.

If what you say is true, neither case is in "our future" because the events happened before we saw them. Therefore, nothing at all is in "our future" because all events take some amount of time for us to detect them.

It doesn't follow.

How does an event happening before we see it mean that there cannot be events that have not happened yet?

So, if that's true, what is meant by the "future" light cone?

A light cone describes all the places that a flash of light can affect or be affected by over time. The future cone describes all the places that can "see" the light from the flash. The past cone describes all the places that the flash of light could have seen.

That is, if I can't say that light from an explosion on the sun is in our future (if I'm eventually going to see it), what can we say is actually in the future light cone?

The light is in your future even thought the event has already happened.

Like you said in Message 35:

quote:
Catholic Scientist writes:

Because the event has already happened.


Okay, I understand then. This was more of a terminology issue then a concept issue.

Seeing the explosion may be in my future (in a destiny sort of sense), but the event itself is not in the future, because it's already happened. I understand that.



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New Cat's Eye
Inactive Member


Message 44 of 131 (487265)
10-29-2008 9:48 AM
Reply to: Message 32 by AdminNosy
10-28-2008 11:30 AM


Re: Uncalled for
You gonna take care of V-Bird too?

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AdminNosy
Administrator
Posts: 4754
From: Vancouver, BC, Canada
Joined: 11-11-2003


Message 45 of 131 (487266)
10-29-2008 9:54 AM
Reply to: Message 42 by johnfolton
10-29-2008 9:43 AM


johnfolton
johnfolton, please do not post in this thread again.

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