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Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: crimsonknight3 on 14/07/2012 14:08:57

Title: Does time dilation increase or decrease away from a mass?
Post by: crimsonknight3 on 14/07/2012 14:08:57
I know that time runs slight faster in near earth orbit, however does the time dilation weaken the further away from a large body you get? If it increases in NEO does  it get faster further away? Surely that breaks the laws of physics, if the further away you get the faster time dilation is, 100million light years from earth time would be running exponentially faster? So if it's gravity that distorts time, wouldn't time be equal to, or slower than earth time away from its gravity?
Title: Re: Does time dilation increase or decrease away from a mass?
Post by: yor_on on 15/07/2012 00:33:15
A time dilation is only existent between frames of reference, meaning that you always use your own wrist watch and ruler to measure that dilation against some other frame of reference. The time measured by/on yourself never varies though, no matter where you are or how 'relatively' fast you define yourself as moving.

Time is neither accelerating, nor slowing down for you, ever. It's somewhat of a geometrical description discussing it (a SpaceTime), and it does not relate to any higher degree to the measurements you can do on yourself, or in/at your closest vicinity.

Title: Re: Does time dilation increase or decrease away from a mass?
Post by: crimsonknight3 on 15/07/2012 11:13:52
I know that personally it never changes but say you were measuring time and so was i, would the time get incrementally faster, or normalise, or slow down, the further away from earths/the suns mass/graitational pull. I've been wondering about this because i was watching a brian cox program and he went to a satelite control facility and they were saying they have to repeatedly update the time of satelites because the time in NEO runs slightly faster. If time is relative to the person experiencing/measuring it then it would be constant but if you have 2 points of reference then the second person getting further from earth would experience what?

People have said that if a group of people travel to mars and it takes them 2 years to get there, then people on earth would have aged a lot further than 2 years but i dont see how this is possible if time dilation is affected by a large mass bending space time
Title: Re: Does time dilation increase or decrease away from a mass?
Post by: imatfaal on 15/07/2012 14:19:35

OK - first off; you seem to be happy with the idea that you can never see your own watch as dilated or fast ticking.  Your watch on your wrist is always normal.

There are two forms of time dilation.  Two frames moving at relative velocity will show time dilation.  A GPS atomic clock will when checked from an earth bound clock lose 7 microseconds per day due to this.

Two frames at a different gravitational potential also show time dilation.  The closer to the source of gravity (ie at lower potential) the slower the clock ticks.  A GPS satellite clock will when checked from an earth bound clock will gain 45 microseconds per day due to this.

Thus you must sum the time dilations/fast-ticking +45 -7 = +38 microseconds per day. 

Someone in a GPS unit would see the earth as running slightly slow.

A mars trip will not have a significant amount of cumulative time dilation.  But a much longer voyage at closer to the speed of light would have significant change in time past.  This is often known as the twin paradox.  The twin who travels will upon his return be younger than the twin who stayed.  This causes a lot of confusion - and rather than try and explain it, I will include a few links to some expert explanations.  be aware forum explanations of the twin paradox are often incorrect - but these links are done by real physics academics
Title: Re: Does time dilation increase or decrease away from a mass?
Post by: crimsonknight3 on 15/07/2012 15:15:53
I read through two of those websites and though it explains things pretty thouroughly I still don't understand the 'reason' for time dilation, it's all about calculating time dilation and explaining how to quantify and explain why the twins see a difference, it doesn't explain why one twin ages faster, if time just a construct of humans I don't see how a person could age differently just from travelling. Its like saying a person standing still and a person running away from them age differently and if you put the speed of light into the equation we still don't know enough about light itself, there are particles that travel faster than light, and gravity can bend light so if we don't understand the nature of light, then how can we know the nature of a humans perception travelling at the speed of light? If you travel a distance of 2 light years in the space of 2 years, turn around and come back in the same time frame, the perception on earth is that it has taken 2 years, as light travels said distance in 2 year? If the speed of light is constant and measurable and a person is travelling at the same speed, we measure it as 2 years, i really dont understand this principle.

Say a ship is a beam of light. They travel 2 light years out then 2 light years back, to earth that is 4 years. If the beam of light was a person, to them it would also take 2 years there and 2 years back? So what actually causes the time dilation? Is it purely the 'acceleration' 'breaking' 'acceleration' 'breaking'?
Title: Re: Does time dilation increase or decrease away from a mass?
Post by: yor_on on 15/07/2012 15:34:34
Crimson, it's geometrical and, yeah, pretty weird, wild?
Take your pick :)

Somehow 'time' and the room geometry you observe around you is connected. Why that is, is not explained. Einstein used lights constant speed in a vacuum to deduce it, as I think, and from there he just kept going full steam :)

But he doesn't state the reason for light as a constant, well, as far as I know. What we could, and have, done is to test this experimentally and it is, as good as we can measure it, true. Relativity has been tested over a hundred years now.
Title: Re: Does time dilation increase or decrease away from a mass?
Post by: yor_on on 15/07/2012 15:46:25
And no, it's not the acceleration breaking. If we assumed this was the reason only accelerations/decelerations would fit a time dilation, and all uniform motion would be excepted. But they are not, they also will express a time dilation if measured between frames of reference, as Earth measuring that rockets 'clock'.

The next question is if this is real or just a 'twisted geometry' fooling us.
But it's real, as proven by NIST on Earth using gravitational time dilations.

It's hard for us to do a 'twin experiment' as we don't have the science for it yet but we can see the effect measuring muons life length as they travel through the atmosphere, so much further than they have any right too :) well, sort of..

From the muons pont of view his 'time' is as always, but the measured distance to the ground differs from the one we measure on Earth, observing him. From our point of view his 'time' is slower than ours allowing him to reach the ground. But in both cases if we measure the speed of light in a two way experiment (locally where we are that is), reflecting it back to the originator, we both would find that according to our own clock, and our own ruler, lights speed is the exact same for both.

Title: Re: Does time dilation increase or decrease away from a mass?
Post by: crimsonknight3 on 15/07/2012 23:53:32
So are we talking purely about geometrical time dilation? Brian cox explains time dilation in near earth orbit to be caused by the earths bending of space time, not a geometrical issue, especially if a satellite is in geosyncronous orbit, though yet its constantly falling, it stays the same distance from earth more or less all of the time, so geometry wise, it would be simply the distance between 2 fixed points in space and time. x y z and time yet there is time dilation there despite the lack of geometry used in those websites explaining it.
Title: Re: Does time dilation increase or decrease away from a mass?
Post by: yor_on on 16/07/2012 03:13:16
To me it is a warped, observer defined, geometry. What Brian Cox sees it as I would have to read up on before saying that I know how he sees it. It also has to do with how you want to define a SpaceTime. Is it 'seamless'? The equivalently 'same' at all positions, including time? Or is it observer defined?

I would say it is observer defined :) And only locally equivalent, well, as I think of it. The geometry I think of include 'time' though, it's a 'room time geometry' or 'SpaceTime' if you like. You can either define it that way or assume that your senses is telling you the same as the next guy, and so prefer to define it as a 'whole seamless SpaceTime', same for us all. But as you do that you will find both LorentzFitzgerald contractions and time dilations differing your description of the universe from your neighbors. Or you can just try to ignore those effects, which some do seem to do, even renown physicists. It all depends on how you define it.

You could think of it this way. the only real, direct, measurement you can do is the one you do locally, using your ruler and your clock. If that clock and that ruler tells you one thing, but your neighbor says another. Who should you believe? Strictly seen it will always be a first hand experiment done by you that will tell you a outcome, and that's also what science builds on. So called 'repeatable experiments'. And as I see it :) that those experiments in any way continue to be repeatable should tell one something about 'locality's' importance, for a universe filled with time dilations and LorentzFitzGerald contractions.

But that's not a main stream definition though. You can also define such as 'time' and 'the arrow' is a illusion, although I haven't meet anyone succeeding with that yet. Doing so you might be able to keep the definition of a 'same seamless' universe for us all, like a 'seamless' ocean in where we all are together. But I can't ignore the arrow myself. I'm pretty sure I'm going to die some day for example :)

And those that do this have still to explain why distances are observer dependent..

I may be wrong there, but I don't think so.
Title: Re: Does time dilation increase or decrease away from a mass?
Post by: yor_on on 16/07/2012 03:43:53
There is one other way possibly?

Consider that you are made up of 'energy', whatever that is. We are 'plastic' although not as we notice, a 'gravitational wave' is expected to momentarily deform the matter it meets (theoretically). But it won't stop us from functioning, and measuring :) and we won't notice it locally either.

The point I'm trying to make might be one of 'fluidity',  and 'density'? We are part of SpaceTime, each one of us is, and obey the same exact 'laws' as everything else. From the point of view of SpaceTime we shouldn't differ from anything else. Everything we know and all we observe is a result of our evolution inside a SpaceTime, under a arrow of time defining our history. We are 'one eyed' in that motto, and imagining a a 'static reality'? I'm sure there is one but it's very hard to define it as we don't have those concepts. But that static reality is no more true than the arrow as I think of it. Without a arrow, no outcomes.
Title: Re: Does time dilation increase or decrease away from a mass?
Post by: crimsonknight3 on 16/07/2012 12:53:23
Because there are countless variables effecting us and space time that we don't yet understand, such as gravitiantional waves being through off pulsars we still can't accurately measure anything with any certainty. Isn't there a famous saying 'the more accurately you try to measure something the more uncertain you are as to where it is' basically what i'm trying to say it this time dilation effect is us trying to understand the fundamental nature of the entire universe.

Everything is connected and effects everything else though to one human in an entire universe its impossible to grasp the scope of this. If time dilation is a bending of space time then that makes for one explanation not taking into account the changes the rest of the universe puts on our local space time, however the explanation of space time being like a piece of cloth that is bent or stretched when you put something heavy on it makes a lot more sense to me than most other explanations for space time. Though all of these geometrical explanations remain theoretical as we can't travel at near the speed of light yet the difference in time between a neo satellite and a gps control centre is physical, measurable and explained with a simple theory. Sometimes the simplest answer is the correct one despite people trying to make a more concrete explanation.

The entire of that explanation (on those websites you showed me) explains time dilation through movement however that isn't the case with a satellite. When the theory Brian Cox said falls apart in my own mind is when you start heading into the realm of black holes. If light can't escape the massive gravity of a black hole, that distortion in Einsteins space time theory would be so great that time would cease to exist? Or at least be stretched to a point where time would almost stand still, like how light stretches over distance due to gravitational forces, and gets stretched into ever decreasing wave lengths, so the same could and should happen for time?

Lastly I would like to say that me personally, with no scientific, mathmatical or physics background to speak of can't accept the fact that light travels at a constant speed. Like all matter in our universe there can't be a singular speed. In my mind light's speed is variable, not by a great margin but variable nonetheless. If light's speed isn't constant then we base a lot of theoretical physics on a constant that is infallible. If light can stretch and bend then why wouldn't either of these have an effect on lights speed
Title: Re: Does time dilation increase or decrease away from a mass?
Post by: yor_on on 16/07/2012 13:14:27
What you get stuck on, as a guess Crimson, is that time seems to differ when comparing between 'realities' or 'frames of reference'. A frame of reference is very much a position, apart from your own. It includes three room dimensions and one time dimension, just as your own do. When you compare those to your own you find discrepancies in the time, and possibly, depending on information gained, say before an acceleration, also discrepancies in the distance measured.

And that is weird, it's not what we're used to normally, and we would need relativistic speeds to see it normally. But it is a fact coming from the definition of lights constant speed in a vacuum. To prove it wrong you indeed need to disprove that fact, And as far as I know there is no such proof existing.

Science builds on experiments that you can repeat, and get the same results from, somewhere else. If that is possible, and those experiments tells you a story about 'reality' then you can't ignore it, To ignore would be self defeating. So to prove a new idea, as a variable speed of light, you need to construct a experiment that can support your hypothesis.
Title: Re: Does time dilation increase or decrease away from a mass?
Post by: yor_on on 16/07/2012 13:36:22
You know Crimson :)

One of the things I wonder about a lot is LorentzFitzGerald contractions. If you consider gravity then it will be stronger the closer you get masses. Now, if we assume relativistic speeds, uniformly moving, then we should be able to measure if they was. If they are it will be a definite proof for LorentzFitzGerald contractions being as 'real' as can be.
Title: Re: Does time dilation increase or decrease away from a mass?
Post by: yor_on on 14/08/2012 21:02:18
Another thing that is worth thinking of is, if now all uniform motions will present us with time dilation's depending on their 'relative motion' relative you measuring. And if all uniform motions in the end can be defined as 'being still', as you have no absolute reference frame to measure that motion against aka 'globally still', how do we define who is moving, and whose the time dilation belongs too?

If we assume that 'motion' exist then there should be some common reference for what it is, not only a relative. And I think there exist one, and that's the way light will change its 'energy' relative your motion. No matter where you are, light will change energy depending on your motion, so in that motto it can't be a relativistic notion but instead a measurable although always 'local' change. That means that although you will find the radiative energy to change with your motion the same won't be true for some other frame of reference, at some other velocity relative you. So all of those effects are 'local' although light, or radiation, in some weird way becomes your true 'speedometer' inside SpaceTime.

The point is that lights constant do present us with a frame that is 'global', in a way giving us a 'absolute answer' to if one are moving, but also that this answer only can be a local one, not shared by all measuring from other frames of reference, as I think of it. And that too points to what's really 'real' only can be defined locally, not globally, even when we use a global constant to define that motion. It's a weird point to make, but uniform motion is really weird in that it somehow doesn't matter what your relative velocity or speed is, as long as there is no acceleration/deceleration involved.

You can also think of LorentzFitzGerald contractions too see it. Either they only exist in a acceleration and disappear in all uniform motions, as measured by/relative different 'frames of reference' moving uniformly. Or they exist in uniform motions too. If they do then how do the universe measure who is moving? If it only is a optical illusion then it is of no importance, but if it is real then all uniformly moving objects find a different SpaceTime. And if the universe has a way to define who is 'contracting' the most as seen locally, then the universe must have a definition for 'motion', not only 'relative' but 'absolute'.

If you accept this the question becomes if it is true, and how we can make such a proposition untrue.

The easiest way to make this untrue is to accept 'locality'. Then there is no absolute definition of motion, only ones local, and always as defined by that radiation (as measured locally), lights speed in a vacuum. And then one get a mosaic out of ones 'universe', dynamically adapting through that constant but always locally defined. And if that is true then one need to ask oneself what 'motion' is? And 'distance' and 'radiation'.
Title: Re: Does time dilation increase or decrease away from a mass?
Post by: yor_on on 14/08/2012 21:28:59
And why it geometrical to me can easily be seen if you consider uniform motions for a rotating drum. That 'uniform motion' will always be a acceleration as it constantly breaks its geodesic, aka 'free path' in SpaceTime. Consider a sling (a looped strap in which a stone is whirled, to then be released and let fly). The 'free path' of that stone only arrives at the time it is released. If we did that in space it would now present us with a geodesic and a 'uniform motion'. But as long as it is geometrically constricted as in a rotating sling it is a 'acceleration' even though uniform. Uniform accelerations and 'gravity is according to Einstein equivalent.