# The Naked Scientists Forum

### Author Topic: Do we know the time dilation factor between distant galaxies?  (Read 2852 times)

#### TGO

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##### Do we know the time dilation factor between distant galaxies?
« on: 14/03/2013 23:28:51 »
In the voids of space between galaxies not in our local group there is as close to 0g as we can ever get.  Does anyone know what the effect on time from our frame would be?  How much faster would time go there compared to on earth with true 0g?  Anywhere inside our local group there is gravity pulling things together so please dont confuse my question.  Im talking in the voids between us and distant galaxies.  Have we measured this?  Can we measure this? Are we ignoring this in the idea that red shift is things moving away?  Are we taking into account how gravity effects waves?

#### yor_on

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##### Re: Do we know the time dilation factor between distant galaxies?
« Reply #1 on: 14/03/2013 23:56:51 »
The only way you ever will be able to prove a time dilation is some sort of twin experiment. Locally it doesn't matter where you are, or how 'fast' you move as far as I get it. Your clock will be as always, as will your ruler. So if time is what makes you age at a specific rate then it never change for any of us. But comparing frames of reference relative each other we can assume 'time dilations' in uniform motion as well as in accelerations, although, where's that twin coming home from it :)

#### yor_on

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##### Re: Do we know the time dilation factor between distant galaxies?
« Reply #2 on: 15/03/2013 00:03:00 »
Think of it in form of NIST:s relativistically sensitive clocks. If they hang one at your pillow and one at your head standing up, showing different times due to gravitational timedilation. Do you expect yourself to lose your 'local time' between you lie down to then rise? Locally time never change, but between frames of reference we definitely find differences. Remember also that your life span must be 'known' locally, the arrow won't ever lose count on it, acceleration or no acceleration.

#### TGO

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##### Re: Do we know the time dilation factor between distant galaxies?
« Reply #3 on: 15/03/2013 01:01:54 »
First thank you for the response. A bit more of a question.

As many have done thought experiments on what happens at the edge of a black hole, have many done the opposite?  Thinking of a spaceship in deep space?  True 0g?  While yes my ruler on the spaceship would be the same to me... but earth would see it going very fast because the only gravity I am producing is the spaceship.

What effect would this have on the light coming in from distant galaxies, as it leaves a gravitational body(the other galaxy) does it not experience time in this area where there is no gravity fields(as many say the photon doesn't experience time) then slows to our time as it approaches earth?

#### yor_on

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##### Re: Do we know the time dilation factor between distant galaxies?
« Reply #4 on: 15/03/2013 12:27:28 »
Relativity is always about relations between two frames of reference, as far as I can see that is. The relations can be described in length contractions and time dilations. It becomes very difficult discussing those relations as some 'real array' measuring defined 'time and length difference's' between two objects in space. 'Simultaneity' is the closest description we have to it, as I suspect, and that one will hurt your head :) as it does mine.

You just need to think of it as us having A relative B. Both in a uniform motion although, when compared to C, finding 'real' differences in 'speed/velocity' relative each other.

A will define one distance, B should be able to define another, and C a third, relative any and all of them. The same goes for the time dilation as it seems a 'symmetry' of sorts to me. The only way I see to really agree on a same distance, and no time dilation (ignoring their gravitational mass), is when being 'at absolute rest' relative each other. And that is a really weird thing. What I mean is that all three of them should have their own interpretation of distance and time, relative the others,  all of them using their local clock and ruler to define what is 'right'.

So, which one of them are right? All of them define different relations relative each one of the other. And photons, or just light, definitely 'experience' time, as we experience them. Otherwise there would be no calculations on the 'speed of light in a flat SpaceTime' from our side, measurable. To me, it seems all to be about relations, but none of them the exact same. But your local time, and ruler, is, always the same to you, and that is what you use measuring other 'frames'.

#### yor_on

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##### Re: Do we know the time dilation factor between distant galaxies?
« Reply #5 on: 15/03/2013 12:41:16 »
It's not so much about having 'one time' and 'one length' for our universe, it's more about 'relative motion' creating a universe with 'speed differences' when looking over many objects. But using just two objects in uniform motion relative each other, you are free to define all measurable 'motion' to any of them. you being on one. Somehow it reminds me of QM:s definitions of 'indeterminism', but on a macroscopic scale.

#### simplified

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##### Re: Do we know the time dilation factor between distant galaxies?
« Reply #6 on: 15/03/2013 19:23:24 »
Have we measured this?  Can we measure this?
We can't measure this.We can observe and calculate.

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##### Re: Do we know the time dilation factor between distant galaxies?
« Reply #6 on: 15/03/2013 19:23:24 »