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Belated Time travel .. ?


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#35 Drum

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Posted 29 December 2007 - 11:57 PM

Hi Snoopy ..... Well I am unable to break the circle because all that has been posted has still not distilled a working definition of time.

There are 2 ways in which we can conceive of Time.

There are two distinct views on the meaning of the word time.

One view is that time is part of the fundamental structure of the universe, a dimension in which events occur in sequence, and time itself is something that can be measured. This is the realist's view, to which Sir Isaac Newton subscribed, and hence is sometimes referred to as Newtonian time.


I don't accept this view, despite the fact that we are all Newtonian in outlook. We go to work, keep appointments, eat, plan etc all according to Newtonian time. simply because there is no other way to structure our lives.

An opposing view is that time is part of the fundamental intellectual structure (together with space and number) within which sentient beings sequence events, quantify the duration of events and the intervals between them, and compare the motions of objects.

In this second view, time does not refer to any kind of entity that "flows", that objects "move through", or that is a "container" for events. This view is in the tradition of Gottfried Leibniz and Immanuel Kant, in which time, rather than being an objective thing to be measured, is part of the measuring system used by humans.


I think we all agree that this is the correct (or best fit) for a definition of Time. (EW may not agree). If we agree on this then a working definition for this thread would be that Time is not an Entity, but a measurement.

Do we accept this ?? Tormod ?

Now we can say that time is a measurement of change, relying on the second definition in the Wiki.

1) What is "change"? How do you define it?

Change .. of course .. is anything ... but what we need to measure it is 'Periodic Change'. The sun moving across the sky, or the seasons, or phases of the moon.

2) How do we measure this change? Where does it happen?


Tormod ... I am sure you know this as well, probably better, than me. Our current most accurate measure of change is the perturbations of electrons around the Cesium atom.

3) If change is measured by time, what is the equation that shows it? (and how much change is measured in how much time)


The second is the 'earthly' working minimum of change. Physically the second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. ... LOL

Hyperfine is a Quantum term. The equations can be found here:
Hyperfine structure - (click here)

4) What is time? If your answer to 4) is "time is the measure of change", then your logic is circular.


As I have answered the first three, the fourth becomes rather irrelevant don't you think. Personally I feel that Time is a human perception. So far as I know, no other species keeps appointments. All other species follow a biological clock. eg: we can track other animals, we recognise footprints .. no other species can do this .. a lion can track by smell, or direct sight ... only we can posit a relationship between an irregular disturbance in the mud or dirt or sand and picture a wildebeest, and his direction of travel, in our minds. "Him bigfella from yesterdays Sun, went this way" ... LOL.

This requires a large memory .. When we access memory, in comparison to a current moment in 'reality', we interpret this as a change, or event, from a past time.

Only Homosapiens has found it necessary to record the past, posit the future, and recognise the present as the imaginary dividing point.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

My initial post (and logical argument) was that this imaginary point is no point, due to General Relativity, but that we must necessarily exist across many 'singular moments'. However small the measurement, our bodies consist of many parts in motion in relation to other parts due to infintismal amounts of time dislocation that we perceive as one moment.

Ergo: A moment is imaginary, a human construct ... that in fact different parts of our body would record a different amount of beats of the Cesium clock having elapsed for any given 'Human' instant. The Past, present and Future cohabit ... only the Zygotes separate them ... :evil:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Now of course, we are all totally confused, including myself ...... LOL

cool bananas ... Drum :turtle:

#36 CraigD

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Posted 30 December 2007 - 09:47 PM

Relativity also predicts that such “distortion” is apparent near very massive objects, such as planets, stars, and in the extreme, black holes.

Can we just accept gravity as acceleration, and therefore motion, for this thread ?

In short, no. I think such a concession would give rise to a serious misconception.

Gravitational time dilation is related to the force of gravity on a test mass, not any acceleration of a body due to this and other forces. Two frames can have zero relative velocity, zero acceleration (change in velocity) and still have a difference in the relative rate of their clocks.

Consider two very accurate clocks, on the surface of Earth (for simplicity, exactly at one of is rotational poles), another 500 m directly overhead (aside from being at the poles, this isn’t an outlandish height – the Sears tower has an inhabited floor 412 m above ground level, while the Burj Dubai will have one at 624 m). Calculating their relative gravitational time dilation gives [math]1-5.5 \times 10^{-14}[/math], or, in more intuitive units, a difference in elapsed time of about .0001 s per 80 years.

With the best atomic clocks now having accuracies of about [math]10^{-14}[/math], the current International Atomic Time (TAI) standard actually must take time dilation into account. Such an adjustment has been made since the 1970s, with each atomic clock contributing to the standard adjusting the actual time it measures to the value it would be if the clock were at sea level.

In practical human terms, gravitational time dilation is more significant than velocity time dilation. Although many people familiar with them are aware that GPS satellites have their clocks adjusted to compensate for time dilation, many of these people believe that, due to their velocity time dilation, a standard clock on a GPS satellite ticks slower than one on Earth’s surface, when in actuality it ticks faster, because its gravitational time dilation is greater (about [math]+45.9 \times 10^{-6} \,\mbox{s/day}[/math] vs. [math]-7.2 \times 10^{-6} \,\mbox{s/day}[/math]). Rather than aging minisculely less, present day astronauts, such as those on the ISS, age minisculely more than non-astronauts.

I am just examining a Forest while you guys are asking for, and providing, the scientific genus of each individual tree .....:evil:

Science types do tend to be detail (tree) oriented ;)

However, the distinction between gravitational and velocity time dilation is an important “big picture” (forest) one. Though theoretically related, it’s not such a simple relationship as “gravity causes acceleration, acceleration relative velocity, relative velocity time dilation.” As I describe above, gravity causes time dilation even when it causes no acceleration.

#37 Drum

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Posted 30 December 2007 - 10:55 PM

Though theoretically related, it’s not such a simple relationship as “gravity causes acceleration, acceleration relative velocity, relative velocity time dilation.” As I describe above, gravity causes time dilation even when it causes no acceleration.


Craig .... good post and I appreciate your definition.

Would you agree that whether gravity or velocity, time dilation is an outcome of experiencing different g-force ??

eg: the clocks that are higher experience less g-force than the clocks that are lower, therefore the higher clocks count off time faster ??

This is the same as the effects of different g-force under velocity even tho the clocks are apparently stationary to us earthly observers. ?? Time dilation is not only an effect of linear separation. If you were simply spinning around fast enough you would experience time dilation without moving from the spot.

Craig ... I am not an expert and am willing to take on board your more experienced understanding.

cool bananas ... Drum (greg) :eek2:

PS: please note that 'we' judge the hi and lo clocks to both exist in the same conceptual moment .. even tho this is not true, as their time difference testifies ... which I feel points to my conclusion in the first post that 'we' physically must exist across more than one 'moment' ...... ???

#38 Little Bang

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Posted 31 December 2007 - 09:35 AM

Both of you basically agree, just your nomenclature is different.

#39 snoopy

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Posted 02 January 2008 - 06:13 AM

Hi Snoopy ..... Well I am unable to break the circle because all that has been posted has still not distilled a working definition of time.

There are 2 ways in which we can conceive of Time.



I don't accept this view, despite the fact that we are all Newtonian in outlook. We go to work, keep appointments, eat, plan etc all according to Newtonian time. simply because there is no other way to structure our lives.



I think we all agree that this is the correct (or best fit) for a definition of Time. (EW may not agree). If we agree on this then a working definition for this thread would be that Time is not an Entity, but a measurement.

Do we accept this ??


Your first view is physics the second view is metaphysics.

In this second view its important to realise metaphysics is incompatible with physics. That is it is impossible to get a mathematically working definition of time from it so while interesting to ponder absolutely useless to physics.

I much prefer Einsteins ideas where time is woven into the fabric of space creating a spacetime block. Before any objections to this idea arise from what the the fabric of space is made of, it seems to be made up of fields.

So no I dont especially agree with either of your definitions of time and subscribe to Einsteins idea of time. I hope this is clearer.

#40 Little Bang

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Posted 02 January 2008 - 02:17 PM

I guess you guy's must be talking about a definition of time that does not exist in any dictionary.

#41 modest

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Posted 02 January 2008 - 04:24 PM

Would you agree that whether gravity or velocity, time dilation is an outcome of experiencing different g-force ??

eg: the clocks that are higher experience less g-force than the clocks that are lower, therefore the higher clocks count off time faster ??

This is the same as the effects of different g-force under velocity even tho the clocks are apparently stationary to us earthly observers. ?? Time dilation is not only an effect of linear separation. If you were simply spinning around fast enough you would experience time dilation without moving from the spot.

A person falling through the event horizon of a black hole will experience no g-force nor does "acceleration of gravity" have (neither could it have) any meaning in this case - yet time is dilated infinitely.

I would definitely agree with CraigD

-modest

#42 InfiniteNow

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Posted 02 January 2008 - 06:28 PM

A - yet time is dilated infinitely.


That is, of course, relative to an observer outside of the horizon. To the infalling person, everything would appear as per normal until the tidal forces spaghettified them. :)

#43 modest

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Posted 02 January 2008 - 08:29 PM

That is, of course, relative to an observer outside of the horizon. To the infalling person, everything would appear as per normal until the tidal forces spaghettified them. :shade:


Ah, yes, thank you InfiniteNow. Falling in a super massive black hole - the astronaut's guitar keeps perfect tune (from his and only his lonely perspective) .... and the song is that much sadder, being lost to the universe forever.


- modest

#44 InfiniteNow

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Posted 02 January 2008 - 10:08 PM

Ah, yes, thank you InfiniteNow. Falling in a super massive black hole - the astronaut's guitar keeps perfect tune (from his and only his lonely perspective) .... and the song is that much sadder, being lost to the universe forever.


When did he get a guitar? Also, the sadness of that tune is entirely subjective, as it's truly just becoming redder and redder... not bluer and bluer.


:shade:

#45 modest

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Posted 02 January 2008 - 11:36 PM

When did he get a guitar?

It's an official NASA guitar (designed for use in space and costing many times more than a luxury car)

Also, the sadness of that tune is entirely subjective, as it's truly just becoming redder and redder... not bluer and bluer.

Very nice :shade:

#46 freeztar

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Posted 03 January 2008 - 12:21 AM

It's an official NASA guitar (designed for use in space and costing many times more than a luxury car)


But how does it sound? :shade:

I heard it comes standard with drop-G tuning. :shrug:
Everybody knows the standard is E. They should have never hired that Schwarzschild guy. :hyper:

#47 modest

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Posted 03 January 2008 - 06:04 AM

As we pull the thread off topic further...

But how does it sound? :eek:

Oddly enough this is also relative. The black hole will work as a filter transforming quite bad country music into quite good rock / electronic music. This will one day be a very good argument for intelligent design when it is realized that god lives in black holes and can't stand country music.

To salvage the subject of the thread:

All thats moving in relation to us, cars on the street, trees in the wind, the hair on our head blowing in the wind, the wind itself, our arm as we strike a home run .... must, in some sense be moving slightly into the future, or alternatively, the past. Our body and all around us must only be synchronised when we are 'still' in relation to our selves and our surroundings.


It would seem to me everything would disappear Drum. When time is dilated infinitely to an outside observer - redshift would also be infinite. The best example would have to be the event horizon of a black hole. As it approached the horizon you would never see time stop - it would just be red shifted more and more until it is no longer observable.

- modest
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#48 Drum

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Posted 03 January 2008 - 06:28 PM

A person falling through the event horizon of a black hole will experience no g-force


I think maybe you have misunderstood Craig D. and Me. If you crossed an event threshold you would certainly experience different g-forces all over your person. The sum of these g-forces would equal the force required to back out .... ????

nor does "acceleration of gravity" have (neither could it have) any meaning in this case - yet time is dilated infinitely.
I would definitely agree with CraigD


If I am accelerating in my car so that I am pushed back in my seat to the accelerated guitar tune of 90kg ..... Or I am standing on a beach picking my nose so that my feet imprint on the sand to the gravity guitar tune of 90kg depth... its still the same ...

The time dilation is finite ... can be calculated ... What are you talking about,
where have I gone wrong ???

cool bananas ... Drum :eek_big:

#49 Pyrotex

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Posted 03 January 2008 - 06:32 PM

Hey! I just flew in from 1550 B.C. and boy, are my hands tired.

:eek_big:

#50 modest

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Posted 03 January 2008 - 07:18 PM

I think maybe you have misunderstood Craig D. and Me. If you crossed an event threshold you would certainly experience different g-forces all over your person. The sum of these g-forces would equal the force required to back out .... ????


Ok, I'm no astrophysicist nor an expert in GR, but it seems you are confusing the "acceleration of gravity" as the cause of gravitational time dilation.

A person in free fall may well be accelerating and a person standing stationary on a massive body may well feel 'acceleration of gravity' - but these are not the cause of gravitational time dilation. It is given by:

[math] t_o=t_f\sqrt{1-\frac{2GM}{rc^2}} [/math]

The time dilation caused by a massive body is dictated only by it's mass-M and your distance from that mass-r. This is true if you're free falling or experiencing G-force while standing on the massive body.

Craig D gave the example of GPS satellites which we know are in free fall and experience no G-force and need to be corrected for gravitational time dilation. In my example of a mass falling through the schwartchild radius of a black hole there would be infinite time dilation (to an outside observer). This is because the radius = [imath]2GM/c^2[/imath] and if we plug this into the equation above we see that time dilation is indeed infinite at the event horizon of a black hole. Also, "acceleration of gravity" can have no meaning here. As an astronaut falls through the event horizon there is no way to stop and feel the acceleration of gravity. There could be no place to stand - it would be impossible for such a person to 'weigh' him/her self. This astronaut would feel no G-force as he free falls to his death.

So, gravitational time dilation cannot be treated as acceleration and is not an effect of G-force. If this is unhelpful or you need a more in depth explanation there are many people here with a stronger understanding of this than me.

- modest

#51 Drum

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Posted 03 January 2008 - 11:13 PM

I'm not an expert either Modest. However orbiting satellites are only in apparent freefall.

They are not free of gravity but thay are experiencing 'less' of it because of their distance compared to the surface of the earth. This is the cause for the correction. Less gravity, less g-force.

I don't really understand black holes, but the fact that our bodies (and everything else) are stretched as we cross the event threshold implies that gravity is measurably different between our ankles and our ears once we descend into it. This would cause an exponential squeezing effect.

Still trying to understand all of your post.

cool bananas ... Drum