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Offline Geezer

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« Reply #75 on: 23/03/2010 05:36:39 »
Anyway, I suspect Geo Driver is quite correct. If you want a three minute egg, time it for three minutes. (I'm assuming we are conducting the experiment at something close to one atmosphere and boiling the egg in water rather than molten iron.)

The timing device and the egg will both experience three minutes in, well, three minutes, or did we conclude the answer would be different?
 

Offline fontwell

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« Reply #76 on: 23/03/2010 09:08:41 »
yor_on, you seem to have it in your grasp. The trouble is that some examples you use jump between GR and SR. A free falling body (or orbiting) compared to the Earth's surface (or centre) has time dilation due to the relative velocities (ignores mass). This is an SR effect. There is also another effect due to being near mass, this is a GR effect.

@Geezer, yes three minutes is three minutes but don't use an hour-glass style egg timer :)
« Last Edit: 23/03/2010 09:43:49 by fontwell »
 

Offline Geezer

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« Reply #77 on: 23/03/2010 18:43:36 »
@Geezer, yes three minutes is three minutes but don't use an hour-glass style egg timer :)

Ah yes! I suppose any device that relied on gravity (pendulums etc) would be suspect  ;D
 

Offline gem

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« Reply #78 on: 23/03/2010 21:12:33 »

@Geezer, yes three minutes is three minutes but don't use an hour-glass style egg timer :)
Not if it contravenes the laws of conservation of energy it isn't. below is an extract from a link J P provided in regards to wether G R voilated energy conservation ...........

An infinitesimal piece of spacetime "looks flat", while the effects of curvature become evident in a finite piece.  (The same holds for curved surfaces in space, of course).  GR relates curvature to gravity.  Now, even in newtonian physics, you must include gravitational potential energy to get energy conservation.  And GR introduces the new phenomenon of gravitational waves; perhaps these carry energy as well?  Perhaps we need to include gravitational energy in some fashion, to arrive at a law of energy conservation for finite pieces of spacetime?.........

Looks to me like there turning gravity back in to a force field.

Anyone else come up with a way to test wether gravity is an attractive force or a bending of time ??

 

Offline yor_on

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« Reply #79 on: 23/03/2010 21:49:12 »
We think we have indirect evidence of gravitational waves acting as a energy Gem.

"The smoking gun is a system of orbiting neutron stars with the catchy name PSR1913+16. Einstein's theory predicts that gravitational waves carry away energy. For a system of orbiting stars, such a decrease in total energy leads to an ever faster and closer orbit. Over decades, radio astronomers have monitored the time that it takes the stars of PSR1913+16 to complete each successive orbit, and lo and behold: this orbital period decreases over time exactly as predicted by general relativity. This is strong evidence that the speed-up is indeed due to the radiation of gravitational waves, and the reason Russell Hulse and Joseph Taylor were awarded the Nobel prize for physics for the year 1993." Gravitational waves.

But, what exactly is this 'energy' we're speaking of, is it the same type we find in our combustible engine? and furthermore, if there exist this kind of phenomena, why couldn't we speak about gravity as a 'force'?
 

Offline Geezer

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« Reply #80 on: 23/03/2010 21:51:08 »

@Geezer, yes three minutes is three minutes but don't use an hour-glass style egg timer :)
Not if it contravenes the laws of conservation of energy it isn't. below is an extract from a link J P provided in regards to wether G R voilated energy conservation ...........

An infinitesimal piece of spacetime "looks flat", while the effects of curvature become evident in a finite piece.  (The same holds for curved surfaces in space, of course).  GR relates curvature to gravity.  Now, even in newtonian physics, you must include gravitational potential energy to get energy conservation.  And GR introduces the new phenomenon of gravitational waves; perhaps these carry energy as well?  Perhaps we need to include gravitational energy in some fashion, to arrive at a law of energy conservation for finite pieces of spacetime?.........

Looks to me like there turning gravity back in to a force field.

Anyone else come up with a way to test wether gravity is an attractive force or a bending of time ??



Well, I'm not sure what it has to do with energy conservation, but I'm pretty sure if it was not three minutes, some other significant law would be violated. I'm not sure what the law is called (or if it even exists!) but, according to my understanding, it is impossible to detect any "variation" in time within a local space. In other words, if your egg required more or less than three minutes of boiling to "behave" like an egg that had been boiled for three minutes, you would have created a means of detecting a "variation" in time without reference to some other time frame.

I'm sure JP will straighten me out if this is not right.
 

Offline Geezer

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« Reply #81 on: 23/03/2010 22:11:14 »
We think we have indirect evidence of gravitational waves acting as a energy Gem.

"The smoking gun is a system of orbiting neutron stars with the catchy name PSR1913+16. Einstein's theory predicts that gravitational waves carry away energy. For a system of orbiting stars, such a decrease in total energy leads to an ever faster and closer orbit. Over decades, radio astronomers have monitored the time that it takes the stars of PSR1913+16 to complete each successive orbit, and lo and behold: this orbital period decreases over time exactly as predicted by general relativity. This is strong evidence that the speed-up is indeed due to the radiation of gravitational waves, and the reason Russell Hulse and Joseph Taylor were awarded the Nobel prize for physics for the year 1993." Gravitational waves.


That's interesting. We know that the Earth manages to transfer energy to the Moon, but I don't think there is any need to invoke gravitational waves to explain the phenomenon.
 

Offline JP

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« Reply #82 on: 24/03/2010 10:38:40 »
Why is energy conservation suddenly coming up and what does it have to do with time dilation?  All you really need to know is what Geezer was saying--that if you put your timer and egg next to each other, then they should both agree on what three minutes is.

The gravitational wave stuff is nice, but it has to do with gravitational energy being carried far away from a gravitational system, doesn't it?  Orbits might decay faster than normal as a result of this, but what does it have to do with timing an egg?
 

Offline gem

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« Reply #83 on: 24/03/2010 19:19:24 »
Why is energy conservation suddenly coming up and what does it have to do with time dilation?  All you really need to know is what Geezer was saying--that if you put your timer and egg next to each other, then they should both agree on what three minutes is.

The reason i brought energy conservation up was that to time and cook the egg you need a set amount of energy in a set amount of time

 And a joule is a unit of energy in the International System of Units,  It measures heat, electricity and mechanical work.

The joule is a derived unit equivalent to a newton-meter, or a kilogram-meter squared per second per second.

A joule is also:

A unit of electrical energy equal to the work done when a current of one ampere is passed through a resistance of one ohm for a period of time of one second.

A unit of energy equal to the work done when a force of one newton* acts through a distance of one meter.

In the meter-kilogram-second (MKS) system, a newton is the unit of force required to accelerate a mass of one kilogram one meter per second per second,

So you will notice time is a factor in the measurement of the work heat equivalence and as we have already noted earlier in this post at the center where in GR time is slower will the energy interactions there not disagree with the International System of Units as regards the laws thermodynamics.

similar to the fact that a particle at the centre of the earth would seem to travel faster than one at the surface according to G R, so distance travelled would disagree with the International System of Units.



But, what exactly is this 'energy' we're speaking of, is it the same type we find in our combustible engine? and furthermore, if there exist this kind of phenomena, why couldn't we speak about gravity as a 'force'?

Energy is Energy it just takes different forms and yes even in GR they must be trying to detect a variation in gravity as some kind of force or maybe they will detect a variation in the gravitational force.
 

Offline yor_on

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« Reply #84 on: 24/03/2010 20:23:24 »
Could you minimize that post a little and make it clearer to me Gem. I sort of lose myself reading it? Are you saying that the units we use are wrong? I'm not sure I'm following you rightly here?

Thinking of the conservation of energy. It just states that we always will have an equivalence in our universe. It may change form when using it, like gasoline comes out as water, heat and CO2 etc, as it also goes up as 'energy' driving the pistons in our engine. but it doesn't come from nothing as far as we know, and it won't disappear into a nothingness. The gasoline just becomes unusable for 'new work', as its usable energy gets transformed into such things as water, CO2 and heat. And the idea is similar to thermodynamics idea of work and 'work done' describing 'usable energy' transforming to 'unusable' energy.

And looking at it that way the only thing requested of this egg in any frame of reference is that the 'work' will be equivalent to the same amount of 'work done', unusable to us after its transformation(s) for it to hold true. So it doesn't really have to do with time dilation or mass. It's a principle of equivalence to me, describing how we think our universe 'works' :)

Like we also speaks of our universe to be a 'closed one' instead of 'open ended'. and that statement have nothing to do with its 'inflation' or 'expansion' but is a statement saying the same as above, that we don't lose any energy, it only transforms, like being in a bubble of a sorts where the 'walls' won't allow any penetration of new 'energy'. At least that's my understanding? That's also why Hawking radiation is so interesting, as we on one side calls Black Holes enigmas and 'singularities' meaning that we can't look past the Event horizons of them, and that they are 'closed' to our universe, but on the other hand according to some theories, still would have some sort of 'information exchange' due to that radiation with our universe.

But I'm not really sure if that was what you were thinking of here Gem?
« Last Edit: 24/03/2010 20:37:37 by yor_on »
 

Offline Geezer

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« Reply #85 on: 24/03/2010 21:39:44 »
So you will notice time is a factor in the measurement of the work heat equivalence and as we have already noted earlier in this post at the center where in GR time is slower will the energy interactions there not disagree with the International System of Units as regards the laws thermodynamics.

I think Gem is concerned that time dilation will affect the quantity of energy required to boil the egg.

Well, no. I don't believe it has any effect on the energy required. Everything at the center of the Earth runs a bit faster (or is it slower - I can never remember) than it does at the surface. By "everything" I really mean everything. All atomic activity, every chemical process, human thought, human metobilism, all physical motion etc. etc. is governed by the local time.

If it actually did require a different amount of energy, you would have invented a mechanism to detect time dilation locally, and that is a big no no. (Sorry for the less than scientific phrase.)

If you use an atomic clock to time your egg for three minutes, the atomic clock measures local time, so it will "tick" exactly the same number of times in three minutes, regardless of its location.

 

Offline yor_on

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« Reply #86 on: 24/03/2010 22:00:44 »
You know Geezer, I think you're right. That thoughts too are regulated by time I mean. They seem so unrelated to what we deem as being materially 'there', as if they wasn't connected to anything materialistic, but they are.

That was a nice one.

Now, how about 'photons' ::))
 

Offline Geezer

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« Reply #87 on: 24/03/2010 23:51:36 »
You know Geezer, I think you're right. That thoughts too are regulated by time I mean. They seem so unrelated to what we deem as being materially 'there', as if they wasn't connected to anything materialistic, but they are.


Well, I think thinking(!!) is mainly a chemical processes, so it would have to be governed by local time. I can't see why anything would be exempt - even photons. That's not to say the speed of light is any different. Light still travels the same distance in unit time. It would kind of have to, wouldn't you think?

(I'm not sure that the photon bit is necessarily correct. It sounds logical, but photons have a nasty habit of defying my logic. Let's see if JP thinks this is legit.)
« Last Edit: 25/03/2010 05:20:52 by Geezer »
 

Offline JP

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« Reply #88 on: 25/03/2010 11:57:10 »
The general rule of thumb is that locally, space-time is flat, so you only need to use special relativity, not GR.  In that case, everything should be governed by special relativity instead of general relativity and as long as things are moving fairly slow, everything is governed by the same "local clock" where the only time dilation you need to consider is from special relativity (i.e. if something is moving fast).  Light you're watching move about should seem to do so at the speed of light no matter what with the appropriate doppler shift if you're moving with respect to the source. 

Was that a long answer to a short question or what?  :)
 

Offline yor_on

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« Reply #89 on: 25/03/2010 18:28:52 »
Quite nice JP, and by flat you're using the idea that it is so vast (the universe I mean) that to us locally all 'curves' will be a straight line? Like we thought the Earth was too, some time ago (last year in my case::))
 

Offline gem

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« Reply #90 on: 25/03/2010 22:11:45 »
The general rule of thumb is that locally, space-time is flat, so you only need to use special relativity, not GR. 
I thought fontwell posted diagrams that showed that space time curves between the surface of a planet and the centre in G R.? And this from a link Jp provided seems to contradict.

An infinitesimal piece of spacetime "looks flat", while the effects of curvature become evident in a finite piece.  (The same holds for curved surfaces in space, of course).  GR relates curvature to gravity.  Now, even in newtonian physics, you must include gravitational potential energy to get energy conservation. 
 

And also if space time is flat locally there would be no gravity according to fontwell that is what happens only at the centre.


If you use an atomic clock to time your egg for three minutes, the atomic clock measures local time, so it will "tick" exactly the same number of times in three minutes, regardless of its location.

when the clock at the centre has ticked the same amount of times as the one at the surface it will have travelled further in its orbit around the sun.

And as mass according to G R is the cause of gravity where will the mass at the centre be bending space time compared to mass at the surface,If what you say below is correct.

By "everything" I really mean everything. All atomic activity, every chemical process, human thought, human metabolism, all physical motion etc. etc. is governed by the local time.


Please explain how ALL PHYSICAL MOTION IS GOVERNED BY LOCAL TIME because according to the atomic clocks the mass at the centre is traveling faster.
 

Offline JP

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« Reply #91 on: 26/03/2010 00:37:26 »
And also if space time is flat locally there would be no gravity according to fontwell that is what happens only at the centre.

Not at all.  Think about how the earth's surface looks pretty flat to you, even though the earth is (roughly) a huge sphere.  Gravity and curvature come in when you look at how you travel from one tiny locally flat patch to another.
 

Offline JP

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« Reply #92 on: 26/03/2010 00:47:02 »
Please explain how ALL PHYSICAL MOTION IS GOVERNED BY LOCAL TIME because according to the atomic clocks the mass at the centre is traveling faster.

Local time is time measured locally.  The local time at the center faster than the local time at the surface.  What's meant by that quote is that how something moves is related to the time that thing experiences, i.e. it's own local time.  So if you put the timer and egg next to each other at the center of the earth, they would pretty much agree on what a second was.  They wouldn't agree with someone on the surface or in deep space, however.  The more curved space-time is the closer your timer and egg would have to be in order to "see" the same local time. 

To really experience the exact same time, they'd have to be at the same point, but since the earth isn't a powerful source of gravity, being next to each other is "good enough."  (Actually for egg timing, the time dilation of the earth isn't even important since microseconds don't matter).
 

Offline Geezer

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« Reply #93 on: 26/03/2010 02:12:38 »
By "everything" I really mean everything. All atomic activity, every chemical process, human thought, human metabolism, all physical motion etc. etc. is governed by the local time.


Please explain how ALL PHYSICAL MOTION IS GOVERNED BY LOCAL TIME because according to the atomic clocks the mass at the centre is traveling faster.

It's not really correct to say it's travelling faster. Locally, it's travelling at the same speed. Speed is distance in time. Everything is governed by local time, so locally speed would be the same at the two locations.

If you had some amazing device that allowed you to observe the two egg timers simultaneously, if both started simultaneously, you would be able to observe that the one at the center of the earth would finish before the one at the surface.

However, locally, both eggs would cook for three minutes because three minutes of local time had elapsed. If you could see two objects moving at 10 mph at the two locations, you would observe that one was moving faster than the other from your perspective, but from the perspective of local observers, they would both be moving at 10 mph.

Don't worry. It only took me about twenty years to get my head around this strange situation. :D
 

Offline gem

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« Reply #94 on: 26/03/2010 18:29:18 »

If you had some amazing device that allowed you to observe the two egg timers simultaneously, if both started simultaneously, you would be able to observe that the one at the center of the earth would finish before the one at the surface.
After
  (Actually for egg timing, the time dilation of the earth isn't even important since microseconds don't matter).
No but for the integrity of the theory micro seconds do matter


Local time is time measured locally.  The local time at the center faster than the local time at the surface. 
Slower.

It's not really correct to say it's travelling faster. Locally, it's travelling at the same speed. Speed is distance in time. Everything is governed by local time, so locally speed would be the same at the two locations.

If you had some amazing device that allowed you to observe the two egg timers simultaneously, if both started simultaneously, you would be able to observe that the one at the center of the earth would finish before the one at the surface.


Can you not see the contradiction in those two statements.

For the clock to seem to be traveling faster it has to be running slow to allow it to travel further.

But the point of the contradiction is lets pretend earth is a vessel traveling through space at speed and on this vessel there are two atomic clocks running at different rates so giving a different velocity for the said vessel. 
 

Offline Geezer

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« Reply #95 on: 26/03/2010 20:07:34 »
Nope. I don't see a contradition and I don't think I can add any more to my explanation.
 

Offline JP

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« Reply #96 on: 27/03/2010 08:02:57 »

Local time is time measured locally.  The local time at the center faster than the local time at the surface. 
Slower.

Touche.  It still doesn't change the rest of the explanation, though.
 

Offline yor_on

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« Reply #97 on: 27/03/2010 19:27:18 »
It's 'frames of reference' we're speaking of here right?

1. Your own 'frame' will always show you the same time, as measured by your wristwatch against your heartbeats, in any 'frame' you exist in.

2. To show a really large 'time dilation' you will have to do a 'twin experiment' more or less, but that it exist is already proved, by muons and GPS amongst others.

3. Without that 'twin experiment' whatever you will observe outside your 'frame of reference' will give you an answer time-wise, as related to you both, but without you being to measure any difference relative time-dilation (naively seen without foreknowledge.)

And 3. is the really remarkable thing to me, making us able to see the universe as a 'whole experience' no matter that according to the 'twin experiment' one of the returning twins won't have aged (accelerating one).

What one might say? Is that we have no way to 'slow down' the universe as a whole. It have it's own 'arrow of time' it seems(?) Ticking at a even pace. What we can do is to 'slow ourselves down' against the universe, and so, relative our place of origin, measure a time dilation.

But I can't see how we ever would be able to 'slow it down'?
That means you aging faster than the universe as a 'whole'.

That is, if you accept my definition of the universe as a 'whole experience' aging of course. Otherwise you might say that there are things/objects aging 'faster' than you. But if it is that way then the experience of being able to observe a 'whole universe' have to be explained from something else it seems to me?

Can you see what I think here? That what we call 'times arrow' then is a very localized phenomena and that our 'universal arrow of time' then becomes even more remarkable, as will all causality-chains observed, following our 'entropy'.
« Last Edit: 27/03/2010 19:29:24 by yor_on »
 

Offline gem

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« Reply #98 on: 27/03/2010 23:08:16 »
welcome back yor on, i thought the white coats had finally caught up with you.


That is, if you accept my definition of the universe as a 'whole experience' aging of course. Otherwise you might say that there are things/objects aging 'faster' than you. But if it is that way then the experience of being able to observe a 'whole universe' have to be explained from something else it seems to me?

Can you see what I think here? That what we call 'times arrow' then is a very localized phenomena and that our 'universal arrow of time' then becomes even more remarkable, as will all causality-chains observed, following our 'entropy'.

And this from the man that helped bring Einsteins theory's to prominence in the scientific community

http://en.wikipedia.org/wiki/Arrow_of_time
Eddington then gives three points to note about this arrow:

1  It is vividly recognized by consciousness.
 
2   It is equally insisted on by our reasoning faculty, which tells us that a     reversal of the arrow would render the external world nonsensical.
 
3  It makes no appearance in physical science except in the study of organization of a number of individuals.

Here, according to Eddington, the arrow indicates the direction of progressive increase of the random element. Following a lengthy argument into the nature of thermodynamics, Eddington concludes that in so far as physics is concerned time's arrow is a property of entropy alone.
 
 

Offline yor_on

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« Reply #99 on: 28/03/2010 04:30:16 »
Not bad Gem, there is another guy that recently described gravity as a product of entropy too, if I remember right. Entropy is a very strange idea as it, as a product, don't have to be equal over the whole area it acts on, that is to my understanding. You can have limited areas with a decreased entropy, yet still with the overall effect being an increased entropy. If I lifted that up to the concept of times arrow, it then seems to state that if entropy and times arrow is the same, we c/should have areas where time 'ticked backwards'?
 

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