If there is no universal frame of reference then how can time dilation occur?

[swansont]

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Moderator Note

EPR discussion exists here: http://www.scienceforums.net/topic/68101-my-particularly-troublesome-version-of-the-epr-paradox/

[CGOLDING]

if i accelerate to near the speed of light in one minute. then travel at that velocity for 10 years.

 

turn around while at that speed and make my way back to earth where i then slow down to the original speed in one minute.

 

there would only be two minutes difference in age because acceleration was only applied for two minutes. (assumining that slowing is the same as accelerating)

 

after i stop accelerating then im just travelling at a speed relative to another person

 

 

 

i also believe that the dppler redshift is proof that relativity is wrong about length contraction.

 

when i watch videos on you tube describing why length contraction happens it says to preserve the speed of light in all reference frames.

 

but they show light moving away from a moving ship at the speed of light relative to that ship. but if the doppler shift happens then it means the ship will be catching up to the light after it was emitted contradicting relativity

 

 

[imatfaal]

Cgolding - although the set up is not identical (spacewoman twin is already moving at beginning of experiment) this Doppler Shift Analysis at Physics Faq sums up the thought experiment very nicely

 

http://math.ucr.edu/home/baez/physics/Relativity/SR/TwinParadox/twin_doppler.html

 

In short - the accelerations make little difference to the time dilation, but they make a huge difference to the twins experience (ie they can only be re-united and the experiment carried out if an a particular acceleration occurs to one twin) and allow us to differentiate the twins

 

but they show light moving away from a moving ship at the speed of light relative to that ship. but if the doppler shift happens then it means the ship will be catching up to the light after it was emitted contradicting relativity

 

First bit is ok - but second section no. Doppler shift does not affect the speed of light - it only affects the frequency and wavelength. No one postulates that the ship ever catches up light.

[swansont]

after i stop accelerating then im just travelling at a speed relative to another person

And that's what causes time dilation. Time runs at a different rate, i.e. a different frequency, and the net effect is the integral of the frequency difference over the whole path. In this case, 10 years.

[machapungo]

I think time only runs in our heads and is not a part of physical reality. You might be surprised that there are a (admitted minority) of physicists that are of that opinion. One notable guy is Julian Barbour but there are others, however that does not mean that they all agree on particulars.

Some that think time is a mental construct as I do but also think that space is not real. I think that space is real and also think that all real things are forms of energy including space.. Us humans are so wrapped up in measuring and explaining that we find it pretty easy to get our thoughts confused with reality. Our brains invented time when we were pre-human. How else can the brain of a predator attempt to predict the motion of a foe or a prey? Cause and effect at our level of existence is obvious. When we look at the really big and the really small levels of existence things are less obvious. There are many clocks in nature and as our intelligence progressed we discovered them and applied them to our problems and measurements. The universe has no problems or measurements. We have invented some pretty accurate clocks that scientists now use to measure things. Somehow, they think they are measuring time but they are really measuring relative motion. There is no time continuum there is only a motion continuum. Everything that exists moves and everything that exists is energy. All energy is connected either directly or indirectly. There are no multiple universes, there is only one. If there are other vast organizations of energy that are beyond our current ability to sense or theoretically anticipate then these too are a part of the one and only cohesive universe. There are no voids on non energy in our universe and our universe is not bounded by a void of nothing. The universe does not need to be defined by an opposite of existence. We sometimes get wrapped up and twisted around the axle of our language. If I say that the universe is bounded by a void of absolutely nothing, not even space, where does that assertion leave me in understanding anything? Nowhere!!! To assert that space is a void is to say it is the nothing of non-existence. I feel quite confident in asserting that when I move my hand it is not pushing aside molecules of atoms to occupy nothing. I feel much better asserting that the atoms of my hand are pushing aside a certain amount of space which fills in where my hand was very much like moving my hand under water. Further, I assert that the space within my hands atoms is trapped there in those structures because it is a part of their total energy and they cannot exist without it. All of the preceding is, of course, not science. But, it is a philosophy that some scientist might choose to investigate.

[ACG52]

There are many clocks in nature

 

Which would seem to support the idea that time is a part of physical reality.

 

What you do with it in your head is your business, but it really doesn't effect reality.