# The Naked Scientists Forum

### Author Topic: What is 'Time' and from what aspects of the Universe does it originate?  (Read 8855 times)

#### MikeS

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##### What is 'Time' and from what aspects of the Universe does it originate?
« on: 26/03/2012 09:01:52 »
Time is.

Time has two aspects.  First, the arrow of time, it's direction.   Second, the rate of flow or passage, the time dilation factor.

'Time' is what we percieve when something that travells at infinite speed (light in a vacuum) is 'slowed' to a finite speed.  At infinite speed there is no causality at finite speed there is.

Why does light when unrestricted travel at infinite speed?  We know that photons do not experience time.  Therefore, in a sense they can be thought of as travelling at infinite speed.  However, to travel at infinite speed implies a lack of causality which in turn implies no arrow or perhaps a double ended arrow to time.  So, light  to travel at infinite speed can only do so outside of time as we know it.  Therefore, the concept of 'speed' becomes meaningless when talking about infinite speed.

The origins of Time.

Having established that Time has two aspects, the arrow and time dilation factor.  Where do they come from?  Obviously they are artefacts of the Universe.  What does the Universe contain?  Mass/energy, gravity and space-time.

We understand from GR that local time dilates near to a massive object due to it's gravity.  (Local time as opposed to non-local time.)   Therefore, one of the ingredients of time is gravity.  Gravity slows light and gives it a finite speed.

We could measure the speed of light in the vacuum anywhere in the Universe and it would be the same.  We can therefore use c as a clock.  I would suggest the Universes master clock.  What is light?  Light (to the best of my knowledge) is the purest form of energy.  A clock in an accelerated time frame runs faster.  Obvious you might think but what does that actually mean.  For that time frame to accelerate implies an input of energy.  Therefore  the other ingredient of time is energy.

Energy unrestricted would dissipate over maximum distance in zero time.  But, under  those circumstances both distance and time become meaningless concepts.  Gravity introduces the concept of 'Time'.  It introduces an arrow of time and the relationship between energy and gravity introduces a time dilation factor.  Energy makes the clock run faster, gravity slows it down.

E=mc2  If we re-arrange this we get c2=E/m.  If c can be used as a reference clock, which it can, then c represents the time dilation factor.  In other words the time dilation factor (Td) is equal to energy divided by mass.  Td=E/m.   Which is what I have arrived at above.

Time is created by gravitational braking of the instantaneous dissipation of energy.  For  time to 'flow' energy must be consumed.  No consumption of energy, no flow of time.  Therefore, the arrow of time is entropy.  All miner arrows are aspects of that.

Time within the Universe is both local and universal depending upon  Td=E/m both locally and universally.  Only if the energy/mass ratio of the Universe remains  constant can Td remain constant.  The energy/mass ratio does not remain constant.  At this epoch mass is being converted into energy.  That implies that time is speeding up (contracting) in relation to the past.

Time and gravity are so closely interwoven that it is impossible to talk about one without the other.  It is therefore suggested that this post should be read in conjunction with http://www.thenakedscientists.com/forum/index.php?topic=43495.0

With apologies.  When talking about time it is inevitable that certain words will be used in a confusing manner .  For instance talking about the 'rate of flow' of time or 'passage of time' or 'speed of passage or flow' is technically incorrect but necessary due to the inadequacies of language.

#### Ęthelwulf

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #1 on: 26/03/2012 09:38:02 »
I will go through everything - but let's tackle this one at a time, even if we don't agree in the end.

First of all, there is no such thing as an arrow of time. It's a much-abused concept which goes back many years. I find links that can varify this. I usually make my own arguements however.

For instance, an arrow of time implies a directionality - which is linear in appearance. This could not be further from the truth considering that time only enters the equations through the appearance of a geometrical theory - the general theory of relativity. Time is not linear, more wobbly than flattened (but still remarkably flat due to precise measurements of space). To [presume] an arrow of time exists, would be like saying you are marking some point on a spacetime map and calling it the ''origin of the universe'', but there is no such place we can say everything came from, a so-called center of the universe. So how can one draw an arrow?

Instead, you'd need an infinite amount of arrows, each pointing in perpendicular directions throughout all of spacetime and call them the ''arrows of time.'' But this is unreasonable because it certainly cannot purport to a physical existence.

There cannot be an ''arrow of time.'' Unless by ''arrow'' we are somehow making the mistake we are projecting how we ''view'' time on the world at large. As has been noted before by myself, all the evidence points to time being a subjective phenomenon than a real physical one that pervades the universe. This is science that predicts this, not just my own contentions on it. So if by arrow of time, we really mean the psychological arrow of time (which is a real arrow) stating that time has a directionality about it, then we are making a mistake that such an arrow exists objectively of our experience of time.

#### Ęthelwulf

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #2 on: 26/03/2012 09:47:31 »
''Having established that Time has two aspects, the arrow and time dilation factor.  Where do they come from?  Obviously they are artefacts of the Universe.  What does the Universe contain?  Mass/energy, gravity and space-time.''

Trust me, I've read more than what I reitterating here, I am just keeping it all to a minimum to give me some breath to talk.

From now on, I want you to start calling this ''Minkowski Space'' because that is what it is, this so--called ''space-time''. It is a four dimensional manifold that was mathematically realized by Einstein's teacher Minkowski after Einstein has formulated the theories of relativity. This was a later realization. Relativity worked fine before the united grounds between space and time.

Often I see arguements of change equalling time. Not only is this verbally wrong, but there is no such thing as a true time evolution in General Relativity - since you want to talk about space and time being united into one construction, maybe we should tackle this question of evolution in GR. Afterall, change therefore is not the same as the type of time evolution you might find in a quantum equation. This evolution allows you to shuffle spacetime coordinates about freely, a process called diffeomorphism invariance. So change is not described by your usual worldlines. Worldines are static, they have no past or future.

This is also a problem for the arrow of time, since it describes worldines. The corresponding equation crystalizes this problem when you quantize the EFE-equations. What you get back is the Wheeler de-Witt equation which describes timelessness on a Global Sense.

#### Ęthelwulf

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #3 on: 26/03/2012 10:01:26 »
''We could measure the speed of light in the vacuum anywhere in the Universe and it would be the same.  We can therefore use c as a clock.  I would suggest the Universes master clock.  ''

I don't know what you mean by this, but if there is any relevance, there is no such thing as an absolute clock.

''Why does light when unrestricted travel at infinite speed?''

I don't know if the photon's speed is exactly infinite, but if I get to the just of the point, it is because of the physical parameters of spacetime, called it's permittivity and permeability. We have

For a massless particle, this moves at the speed of light.

''Having established that Time has two aspects, the arrow and time dilation factor.''

I'm afraid you haven't for me. I accept dilation is an effect we measure using time, but time is only an instrument of measure. It was invented. It's not real. It only applies to our perception which seems to feel some ''flow of time''. Time doesn't even have a flow in physics.

''Energy makes the clock run faster, gravity slows it down.''

In what sense, because when I think of energy, I think of relativistic particles. Their frames of references are dilated as well.

''For  time to 'flow' energy must be consumed.  No consumption of energy, no flow of time.''

Again, I don't know what you mean. What is meant by consumption? That is an odd way to me to look at physical processes.

''Time and gravity are so closely interwoven that it is impossible to talk about one without the other. ''

It's perfectly possible to talk about gravity without time.

#### MikeS

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #4 on: 27/03/2012 09:30:03 »
Ęthelwulf

I would be quite happy to answer all of your questions if we were at least on the same page but we are not.

At the start of your first post in this thread you say
"First of all, there is no such thing as an arrow of time."

Yes there is it's called entropy.

All processes no matter what use useful energy to do work and result in the remaining energy being of less use.  This is the arrow of time and it is called entropy.

A simple example, a clock any type of clock, all types of clock use energy to tell the time.  If we consider the clock to be a closed system then entropy within that system has increased with the passage of time.

I believe that is so self evident it requires no further explanation.  If we cannot at least agree that there is an arrow of time then we are not likely to agree on anything to do with time.

#### Nizzle

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #5 on: 27/03/2012 09:57:38 »
All processes no matter what use useful energy to do work and result in the remaining energy being of less use.  This is the arrow of time and it is called entropy.

That depends on your definition of useful and useless. I reckon photovoltaic cells and chlorophyll cells are doing a pretty good job at making energy more useful

#### Ęthelwulf

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #6 on: 27/03/2012 12:00:34 »
Ęthelwulf

I would be quite happy to answer all of your questions if we were at least on the same page but we are not.

At the start of your first post in this thread you say
"First of all, there is no such thing as an arrow of time."

Yes there is it's called entropy.

All processes no matter what use useful energy to do work and result in the remaining energy being of less use.  This is the arrow of time and it is called entropy.

A simple example, a clock any type of clock, all types of clock use energy to tell the time.  If we consider the clock to be a closed system then entropy within that system has increased with the passage of time.

I believe that is so self evident it requires no further explanation.  If we cannot at least agree that there is an arrow of time then we are not likely to agree on anything to do with time.
Well, why haven't you refuted any statement like I have done with you?

#### MikeS

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #7 on: 27/03/2012 13:52:57 »
Ęthelwulf

I would be quite happy to answer all of your questions if we were at least on the same page but we are not.

At the start of your first post in this thread you say
"First of all, there is no such thing as an arrow of time."

Yes there is it's called entropy.

All processes no matter what use useful energy to do work and result in the remaining energy being of less use.  This is the arrow of time and it is called entropy.

A simple example, a clock any type of clock, all types of clock use energy to tell the time.  If we consider the clock to be a closed system then entropy within that system has increased with the passage of time.

I believe that is so self evident it requires no further explanation.  If we cannot at least agree that there is an arrow of time then we are not likely to agree on anything to do with time.
Well, why haven't you refuted any statement like I have done with you?

I did, your very first one.

#### MikeS

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #8 on: 27/03/2012 14:54:38 »
All processes no matter what use useful energy to do work and result in the remaining energy being of less use.  This is the arrow of time and it is called entropy.

That depends on your definition of useful and useless. I reckon photovoltaic cells and chlorophyll cells are doing a pretty good job at making energy more useful
I never said useless, I said of less use.  There is a difference.  No it doesn't depend upon definition.

The suns mass is held together by gravity.  Gravitational energy forces the mass together increasing both its density and heat.  This causes nuclear fusion.  Fusion converts some of the suns mass into energy.  Some of that energy does useful work.  In the process the sun looses mass and useful energy.  This is entropy.

Photvoltaic cells capture EMR (sunlight) and convert it into electricity.  Electricity does work. Useful energy (sunlight) is used and energy of less use (essentially heat) is the result.  This increases entropy.

Chlorophyll cells convert sunlight into chemical energy.  The plant needs an input of energy (sunlight) to grow and function.  Ultimately the plant dies and entropy increases.  The energy that can be extracted from the dead plant tissue is less than the energy input and the missing energy is low grade and of little use.

In both cases the useful energy came from sunlight and in the process the sun lost fuel and entropy increased.  Although there was in both cases an input of energy it came at the cost of an increase in overall entropy.

#### MikeS

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #9 on: 27/03/2012 15:46:12 »
''We could measure the speed of light in the vacuum anywhere in the Universe and it would be the same.  We can therefore use c as a clock.  I would suggest the Universes master clock.  ''

I don't know what you mean by this, but if there is any relevance, there is no such thing as an absolute clock.

I never said there was but you could do an average of all local clocks.

''Why does light when unrestricted travel at infinite speed?''

I don't know if the photon's speed is exactly infinite, but if I get to the just of the point, it is because of the physical parameters of spacetime, called it's permittivity and permeability. We have

For a massless particle, this moves at the speed of light.

Light within the universe is not unrestricted.  It has curved space-time to deal with.

''Having established that Time has two aspects, the arrow and time dilation factor.''

I'm afraid you haven't for me. I accept dilation is an effect we measure using time, but time is only an instrument of measure. It was invented. It's not real. It only applies to our perception which seems to feel some ''flow of time''. Time doesn't even have a flow in physics.

Strange then that clocks can measure it.

''Energy makes the clock run faster, gravity slows it down.''

In what sense, because when I think of energy, I think of relativistic particles. Their frames of references are dilated as well.

Yes their frames of reference are dilated as well.  That's what local time is.  Where I have said faster or slower that's in reference to a distant frame of reference.

''For  time to 'flow' energy must be consumed.  No consumption of energy, no flow of time.''

Again, I don't know what you mean. What is meant by consumption? That is an odd way to me to look at physical processes.

Consumed is perhaps a poor choice of words, used would be more appropriate.

''Time and gravity are so closely interwoven that it is impossible to talk about one without the other. ''

It's perfectly possible to talk about gravity without time.

Gravity affects time.  Gravity is acceleration, an acceleration in time.
You can talk about gravity without time but you cannot explain gravity without time.

Gravity is acceleration.  One of the components of acceleration is time.  If time were not real there would not be gravity.

How would you account for gravity if time is not real?

#### imatfaal

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #10 on: 27/03/2012 15:50:22 »
To add to Mike's post - I would say that electromagnetic radiation with a wavelength that corresponds to the background temperature of deep space is pretty useless.  This is one fate of the universe (and the leading contender) - eventually all matter and energy ends up in its simplest and most stable state.  these photons are red-shifted to such an extent that nothing in the universe is so cold that they can warm it up - this is the ultimate fate; no change in entropy and no energy usage, heat death.

#### Ęthelwulf

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #11 on: 27/03/2012 17:01:20 »
''We could measure the speed of light in the vacuum anywhere in the Universe and it would be the same.  We can therefore use c as a clock.  I would suggest the Universes master clock.  ''

I don't know what you mean by this, but if there is any relevance, there is no such thing as an absolute clock.

I never said there was but you could do an average of all local clocks.

''Why does light when unrestricted travel at infinite speed?''

I don't know if the photon's speed is exactly infinite, but if I get to the just of the point, it is because of the physical parameters of spacetime, called it's permittivity and permeability. We have

For a massless particle, this moves at the speed of light.

Light within the universe is not unrestricted.  It has curved space-time to deal with.

''Having established that Time has two aspects, the arrow and time dilation factor.''

I'm afraid you haven't for me. I accept dilation is an effect we measure using time, but time is only an instrument of measure. It was invented. It's not real. It only applies to our perception which seems to feel some ''flow of time''. Time doesn't even have a flow in physics.

Strange then that clocks can measure it.

''Energy makes the clock run faster, gravity slows it down.''

In what sense, because when I think of energy, I think of relativistic particles. Their frames of references are dilated as well.

Yes their frames of reference are dilated as well.  That's what local time is.  Where I have said faster or slower that's in reference to a distant frame of reference.

''For  time to 'flow' energy must be consumed.  No consumption of energy, no flow of time.''

Again, I don't know what you mean. What is meant by consumption? That is an odd way to me to look at physical processes.

Consumed is perhaps a poor choice of words, used would be more appropriate.

''Time and gravity are so closely interwoven that it is impossible to talk about one without the other. ''

It's perfectly possible to talk about gravity without time.

Gravity affects time.  Gravity is acceleration, an acceleration in time.
You can talk about gravity without time but you cannot explain gravity without time.

Gravity is acceleration.  One of the components of acceleration is time.  If time were not real there would not be gravity.

How would you account for gravity if time is not real?

A photon's speed is not infinite. In mathematical rigour it is a finite number called the Celeritas. There are no infinities contained in the equations, therefore it's speed cannot be infinite.

And for the clock thing, clocks are designed? Why is this so hard to understand? Man invented clocks to tick away completely subliminal durations we called ''time''. The very fact that you even brought clocks into this does not even persuade me to continue further.

#### MikeS

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #12 on: 27/03/2012 18:23:42 »

A photon's speed is not infinite. In mathematical rigour it is a finite number called the Celeritas. There are no infinities contained in the equations, therefore it's speed cannot be infinite.

And for the clock thing, clocks are designed? Why is this so hard to understand? Man invented clocks to tick away completely subliminal durations we called ''time''. The very fact that you even brought clocks into this does not even persuade me to continue further.

A photon does not experience time.  That could be interpreted to mean it travels at infinite speed.

Yes clocks are designed.  There are many different types of clocks all operating on different principles.  Atomic, electronic, mechanical, speed of light, speed of nuclear decay etc.  All of them together will record the same local time.  Another set of identical clocks together in a different local time (different gravitational potential) will all record the same time but the two different sets of clocks will record a different passage of time.  Obviously they are recording something that is the same for all of them but owes nothing to individual clock design.  The thing they are recording is the passage of time.

If time does not exist what keeps each group of clocks synchronized with one another yet makes one group un-synchronized with the other?  The amount of difference can be mathematically predicted.  How do you account for that?

Subliminal implies the passage of time.

Perhaps you would like to answer the question from my last post.
How would you account for gravity if time is not real?

#### Ęthelwulf

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #13 on: 27/03/2012 20:32:29 »

A photon's speed is not infinite. In mathematical rigour it is a finite number called the Celeritas. There are no infinities contained in the equations, therefore it's speed cannot be infinite.

And for the clock thing, clocks are designed? Why is this so hard to understand? Man invented clocks to tick away completely subliminal durations we called ''time''. The very fact that you even brought clocks into this does not even persuade me to continue further.

A photon does not experience time.  That could be interpreted to mean it travels at infinite speed.

Yes clocks are designed.  There are many different types of clocks all operating on different principles.  Atomic, electronic, mechanical, speed of light, speed of nuclear decay etc.  All of them together will record the same local time.  Another set of identical clocks together in a different local time (different gravitational potential) will all record the same time but the two different sets of clocks will record a different passage of time.  Obviously they are recording something that is the same for all of them but owes nothing to individual clock design.  The thing they are recording is the passage of time.

If time does not exist what keeps each group of clocks synchronized with one another yet makes one group un-synchronized with the other?  The amount of difference can be mathematically predicted.  How do you account for that?

Subliminal implies the passage of time.

Perhaps you would like to answer the question from my last post.
How would you account for gravity if time is not real?

Well, if you want to get technical about this, a photon actually doesn't move at all. Saying a ''photon does not move in time'' as you stated, is actually the same (synonymous even) with the concept that a photon doesn't even move in space. In fact, if current scientific theory is right, a photon does not even possess a frame of reference to solve this problem.

Anyway, as for the clock, you are the one who said, 'observe the clock'. It's not as simple as that, in fact, time is not even a Hermitian Matrix, meaning it does not purport to an observable. What may be interesting however, this does not mean that time cannot be positive, unless we viewed time as an imaginary dimension, which Hawking admittedly has done. My arguement, including Markoupolou's, a Greek scientist who advocates the existence of Geometrogenesis, the idea that space arose late in the universes configuration, that what we really call ''fundamental'' is really the existence which precluded the existence itself of space and matter. In Geometrogenesis, matter and space exist within the low energy epoch. What is known, is that space must have emerged when the universe had grown quite old, it is not itself an artefect of the big bang, if the big bang that is the true explanation of creation.
« Last Edit: 27/03/2012 21:01:58 by Ęthelwulf »

#### Ęthelwulf

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #14 on: 27/03/2012 20:33:34 »
As for subliminal passages of time, be careful not to take this as an objective feature of the world. Too many do this. I call it a ''reflection principle.''

Maybe the word should be defect?

#### MikeS

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #15 on: 01/04/2012 06:30:12 »
Earlier in this thread you requested me to address specific points that you had made which I did.  In my last post I asked you to address two points which you didn't.  They were.

If time does not exist what keeps each group of clocks synchronized with one another yet makes one group un-synchronized with the other?  The amount of difference can be mathematically predicted.  How do you account for that?

Perhaps you would like to answer the question from my last post.
How would you account for gravity if time is not real?

#### Ęthelwulf

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #16 on: 01/04/2012 13:14:55 »
Earlier in this thread you requested me to address specific points that you had made which I did.  In my last post I asked you to address two points which you didn't.  They were.

If time does not exist what keeps each group of clocks synchronized with one another yet makes one group un-synchronized with the other?  The amount of difference can be mathematically predicted.  How do you account for that?

Perhaps you would like to answer the question from my last post.
How would you account for gravity if time is not real?

Syncronization is a matter of relativity, not time itself.

#### MikeS

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #17 on: 02/04/2012 06:27:41 »
Relativity explains the difference in the two groups.  It does not explain why all of the clocks in each group remain synchronized among themselves.
And that did not answer the question
"How would you account for gravity if time is not real?"

#### Ęthelwulf

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #18 on: 02/04/2012 06:34:24 »
Relativity explains the difference in the two groups.  It does not explain why all of the clocks in each group remain synchronized among themselves.
And that did not answer the question
"How would you account for gravity if time is not real?"

Why should I answer that last question?

All I need to do is point my finger in the way of GR and explain gravity in that way. Perhaps I need to remind you that GR is timeless.

#### Ęthelwulf

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #19 on: 02/04/2012 06:35:53 »
Relativity explains the difference in the two groups.  It does not explain why all of the clocks in each group remain synchronized among themselves.
And that did not answer the question
"How would you account for gravity if time is not real?"

Why should I answer that last question?

All I need to do is point my finger in the way of GR and explain gravity in that way. Perhaps I need to remind you that GR is timeless.

You just don't seem to be understanding the fact that GR is timeless - global time vanishes, changes are hard to define in a universe. You've concentrated on things like the abused ''arrow of time'' and ''time dilation'' and got lost in all it's mysticism.

#### MikeS

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #20 on: 02/04/2012 17:16:43 »
I would be very interested to hear anyone's simple explanation of gravity that does not include time?   Gravity is acceleration.  Acceleration is time dependent.

Anyone???
« Last Edit: 02/04/2012 17:20:39 by MikeS »

#### imatfaal

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #21 on: 03/04/2012 10:07:02 »
Time in GR is difficult - you have worldlines and geodesics situated in a metric where time is just one of four dimensions (admittedly different sign). the worldline through spacetime of a test particle follows a route that is dependant on the curvature - it does not accelerate along this world line.  the position and geometry of the worldline means that in 3d space an acceleration is measured, but in spacetime the particle "moves along" the worldline with its clock ticking normally.

#### Nizzle

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #22 on: 03/04/2012 10:55:58 »
I would be very interested to hear anyone's simple explanation of gravity that does not include time?   Gravity is acceleration.  Acceleration is time dependent.

Anyone???

Gravity is more than acceleration I think. Because objects lying still on the ground with 0 acceleration are still subjected to gravity, otherwise they'd float. Acceleration can be used to simulate gravity, but it's not the same.

But that's besides the point. I can't explain gravity without time..

#### Ęthelwulf

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #23 on: 03/04/2012 13:01:21 »
Gravity for me is simple. It is the presence of matter, which is the presence of curvature and is the presence of acceleration within the equations of relativity; this much he is partially correct, I've never truely doubted that. It's linking it directly with time which troubles me. I don't see time and gravity as synonymous objects. In fact, I see change, I don't see time per se. Only through the eyes of a mere human being, I can extrapolate that time is highly subjective and something I project as a ''feeling of past and future'' on the world outside. None of which actually exist.

#### MikeS

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##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #24 on: 03/04/2012 15:25:21 »
Time in GR is difficult - you have worldlines and geodesics situated in a metric where time is just one of four dimensions (admittedly different sign). the worldline through spacetime of a test particle follows a route that is dependant on the curvature - it does not accelerate along this world line.  the position and geometry of the worldline means that in 3d space an acceleration is measured, but in spacetime the particle "moves along" the worldline with its clock ticking normally.

Imatfaal
Good explanation.

The test particle follows a geodesic with it's clock ticking normally in its local time frame but according to an observer not in the test particles time frame it will be seen to accelerate as it enters successive time frames that are more and more dilated.

If I understand correctly that is the same as you have said above?

It still requires acceleration.  The acceleration in this case is not 'in time' but 'of time' itself.

As each second is longer than its predecessor, so the test particle travels further.  This is acceleration.
« Last Edit: 04/04/2012 06:10:53 by MikeS »

#### The Naked Scientists Forum

##### Re: What is 'Time' and from what aspects of the Universe does it originate?
« Reply #24 on: 03/04/2012 15:25:21 »