What is time??

[Dywyddyr]

Huh?
A clockwork clock will change just as much as an atomic clock will.

 

[OnlyMe]

So....

2 synchronised atomic clocks, one on Earth and one in space, would gradually go out of sync due to the gravity or lack of.
But this doesn't mean 'time' itself moves faster or slower. It just means the device we measure time with would change.
If there was an old clockwork clock placed next to each of the 2 atomic clocks, their time wouldn't alter because of gravity, would they?

Huh?
A clockwork clock will change just as much as an atomic clock will.

Dywyddyr's point is accurate.

drumbeat while there is some logic to the intent of your post, if it were the case then how would we explain that the observed changes in clock rates seem to be predicted very well by SR and GR within their respective applications?

SR seems to be especially accurate in describing the slowing of a clock relative to velocity.

GR is harder to confirm as it requires great changes in gravitational fields to be accurately noticeable. The Earth in this case represents a weak field.

 

[origin]

Dywyddyr's point is accurate.

drumbeat while there is some logic to the intent of your post, if it were the case then how would we explain that the observed changes in clock rates seem to be predicted very well by SR and GR within their respective applications?

SR seems to be especially accurate in describing the slowing of a clock relative to velocity.

GR is harder to confirm as it requires great changes in gravitational fields to be accurately noticeable. The Earth in this case represents a weak field.

According to this from Ohio State GR has a more pronounced affect.

From the article:

Special Relativity predicts that the on-board atomic clocks on the satellites should fall behind clocks on the ground by about 7 microseconds per day

A calculation using General Relativity predicts that the clocks in each GPS satellite should get ahead of ground-based clocks by 45 microseconds per day.

 

[drumbeat]

Right, so I concede that the clockwork would change as well. But is the bold sentence still true?

2 synchronised atomic clocks, one on Earth and one in space, would gradually go out of sync due to the gravity or lack of.
But this doesn't mean 'time' itself moves faster or slower. It just means the device we measure time with would change.

I have only just started looking into this subject, so thanks for your help.

 

[Dywyddyr]

Right, so I concede that the clockwork would change as well. But is the bold sentence still true?

Apart from anything else you'd have to come up with an explanation of something that alters clockwork and atomic vibrations in equal measure.

 

[OnlyMe]

According to this from Ohio State GR has a more pronounced affect.

From the article:

origin, that reference is not consistence with what I have understood from other sources. I will need to think on this and recheck my reference lists.

Even Einstein's twin paradox model involving a twin on earth and a twin in a stable orbit, predicts the twin in orbit would age more slowly than the twin on earth. Both SR and GR effects would be present in that thought experiment. I'm pretty sure that AE was aware of the time dilation effects of both at the time...

But like I said I will have to recheck some references.

 

[drumbeat]

So I take it that's a no then...
This does boggle my head, I have to admit.

OK, imagine if you could theoretically sit a mile from the centre of Earth, where time is slower due to more gravity.

In one day, someone on the equator would travel 25,000 miles and someone a mile from the centre would travel 3.14 miles. This would be in EXACTLY the same time frame, whether it feels like 24hours to us or longer.

So how does time slow down closer to the centre?

 

[Emil]

So how does time slow down closer to the centre?

In the center of the earth the gravity is zero.

 

[origin]

So I take it that's a no then...
This does boggle my head, I have to admit.

OK, imagine if you could theoretically sit a mile from the centre of Earth, where time is slower due to more gravity.

In one day, someone on the equator would travel 25,000 miles and someone a mile from the centre would travel 3.14 miles. This would be in EXACTLY the same time frame, whether it feels like 24hours to us or longer.

So how does time slow down closer to the centre?

Lets assume you were in a very high gravitational field, like close to a blackhole (somehow), and you were within view of the earth. You would be able to watch the earth rotate at what would seem to you to be a high rate of speed.

If the gravity was high enough you could watch the earth rotating at 365 RPM (by your clock). If you watched that for 10 minutes and then escaped that gravity and returned to earth you would find that 10 years had passed on earth but you would not have aged those 10 years.

Yes it is weird. This is beyond normal experiences but it is something that needs to be taken into account by system such as your GPS.

 

[OnlyMe]

origin, that reference is not consistence with what I have understood from other sources. I will need to think on this and recheck my reference lists.

Even Einstein's twin paradox model involving a twin on earth and a twin in a stable orbit, predicts the twin in orbit would age more slowly than the twin on earth. Both SR and GR effects would be present in that thought experiment. I'm pretty sure that AE was aware of the time dilation effects of both at the time...

But like I said I will have to recheck some references.

O.K. Origin, I did get at least one reference and it would not apply in this case. It was an e-mail exchange questioning SR and GR time dilation as it might have applied to the Pioneer Anomally final report. Really a stupid question I actually sent off before thinking it through. In that case the effect was far below the observable threshold for the data involved.

So I stand corrected!

 

[drumbeat]

In the center of the earth the gravity is zero.

I said a mile from, to avoid confusion.

Lets assume you were in a very high gravitational field, like close to a blackhole (somehow), and you were within view of the earth. You would be able to watch the earth rotate at what would seem to you to be a high rate of speed.

If the gravity was high enough you could watch the earth rotating at 365 RPM (by your clock). If you watched that for 10 minutes and then escaped that gravity and returned to earth you would find that 10 years had passed on earth but you would not have aged those 10 years.

So to an third man on a medium gravitational field, he would see the Earth spinning quite fast, but also the man in the black hole stand still for a long time.

Where ever you are though, is it not still the 10 years that pass in the universe? The only difference is in the eyes of the beholder as it might 'appear' to be 10 minutes, but is in actual fact still 10 years.

 

[origin]

Where ever you are though, is it not still the 10 years that pass in the universe? The only difference is in the eyes of the beholder as it might 'appear' to be 10 minutes, but is in actual fact still 10 years.

It is not that it appears to be 10 minutes for you - it would be 10 minutes for you. Here is another example for you using the same scenario. This time you let 6 hours pass as you watch the earth spin at 365 rpm (your time). When you returned to earth, 360 years would have passed. Everyone you know would have died and their children would have also died of old age. You however would have aged 6 hours. It ain't appearence it is real.

 

[NietzscheHimself]

That sounds like an easy way to live forever/a pretty long time.

 

[Big Chiller]

You'd be living long only relative to earth time and you would have to remain in orbit around the supermassive black hole.

 

[wlminex]

In the center of the earth the gravity is zero.

. . . probably not . . .but appears to be so with equal gravity (due to mass around the center) pulling uniformly . . . .

 

[mrsmart]

it may depend on the make of the watch

 

[hansda]

What are you trying to say? Are you saying that time is constant but the clocks slow?.

I am saying that , ' time is uniform ' ( if you consider this as ' time is constant ' ; its ok.) . Only clocks slow .

Satellites used for GPS, because of the lower gravity, have their clocks run faster than on earth. Radioactive materials would decay more rapidly at that location. Atoms would vibrate more rapidly (for a given temperature) at that location. Animals would age more quickly at that location.

Aging depends upon environmental effect to our body . If one can maintain good health ; will be able to live longer .

 

[AlexG]

I am saying that , ' time is uniform ' ( if you consider this as ' time is constant ' ; its ok.) . Only clocks slow .

Why does the vibration rate of cesium atoms run slower? All time measuring devices, no matter what kind, run slower. All processes run slower. Time runs slower.

 

[hansda]

How time passes is dependent on theory. This is my take on an discussion of time.

The thing with time is that the standard model defines what time is, i.e. a feature of spacetime which is Lorentz invariant. The curvature of spacetime determines the rate at which time passes. Under Lorentz invariant theory the rate that time passes will be different in environments where the curvature of spacetime is different. The presence of matter curves spacetime. The acceleration of matter by the curvature (a gravitational field) or matter accelerated by any means will experience an environment of greater curvature of spacetime and will experience time dilation as a result. Time passes more slowly as the curvature of spacetime increases.

So if you are discussing the passing of time, unless you specify that your description is theory dependent and the dependent theory is not a spacetime model, you are wrong in most conversations because time is described by the generally accepted consensus theory unless otherwise specified.

" Space-time model was used by Einstein to explain his discovery of relativity . Due to the effect of relativity , space expands or contracts . At that time , it was not discovered that our universe is expanding . So , perhaps it was assumed at that time that , our ' universe is constant ' . He might have thought that , at relativity space expands in the form of time . Thus space-time model came into being . " ---- This is my guess .


Now , it is very well known and discovered that , our universe is expanding , meaning space it self is expanding .

Do we have any practical evidence ( other than theoretical conclusion ) that, time is expanding or contracting ?

So , we can consider that , time as uniform .

 

[hansda]

Why does the vibration rate of cesium atoms run slower? All time measuring devices, no matter what kind, run slower. All processes run slower. Time runs slower.

If the gravity is stronger , dragging is more . So , the oscillation will be slower .