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backandforth
2008-Jan-19, 11:56 PM
I have seen a couple of posts on this board that come close to directly addressing my question but miss the mark a bit.
I am not much beyond classic laws of physics in this question but for me the implications are significant and something I have been wondering about for quite a few years.
If we assume that an object in motion relative to our position in the universe experiences a relative slowing if time as it approaches the speed of light should we not then assume that an object that is loosing velocity relative to the earth would then experience an acceleration of time relative to the earth?
I fully realize that the point of reference needs to be established. So, let’s assume that it is the place from which our supposed big bang occurred represents “zero” velocity and that everything we perceive as matter travels outwards from this point.
I have a few follow up questions to this as it relates to absolute zero and the belief that we can approach but not achieve the speed of light as an object with mass and that subsequently we may not be able to approach absolute stop as a body with mass without incorporating ideas about absolute zero and its impact on the maintenance of mass. However, lets start with determining if my first idea has been adequately disproven yet.

clop
2008-Jan-20, 12:17 AM
I could be wrong but I think that one of the fundamental properties of space is that there is no place from which the big bang occurred. That would imply the existence of absolute velocity. If I understand correctly, this was shown not to exist during the earliest experiments to measure the speed of light.

clop

crosscountry
2008-Jan-20, 12:30 AM
clop is right.


you have to pick some reference point, and then you can work from there.

Tim Thompson
2008-Jan-20, 01:20 AM
If we assume that an object in motion relative to our position in the universe experiences a relative slowing of time as it approaches the speed of light should we not then assume that an object that is loosing velocity relative to the earth would then experience an acceleration of time relative to the earth?
The fastest rate you can observe for any clock is the rate it exhibits when seen by an observer at rest with respect to the clock. Any observer looking at any distant clock will always report the distant clock runs slow compared to a clock at rest with respect to the observer. So I am inclined to say no, you cannot observe a clock to show an "acceleration of time" relative to Earth.

An observer on Earth, looking at a clock in motion relative to Earth (in any direction) will observe that the distant clock runs slow compared to a similar (previously synchronized) clock on Earth (ignoring general relativistic effects).

Another observer, somewhere else, with their own clock, will observe that both the Earth clock and the other clock will run slow compared to theirs, depending on the speed of both clocks with respect to theirs. They may well claim that the Earth clock is slow relative to the other clock, and you might think that is a case of the other clock showing an "acceleration of time" with respect to Earth. But if you start insisting that there must be some significant reality to the observed clock rate, then what do you do about one clock simultaneously running at multiple, observer dependent rates?

Multiple observers, all looking at the same clock, will each observe the clock to be running at a rate different than observed by the other observers. But the clock has only one "real" rate, and that it the rate seen by an observer at rest with respect to the clock. That time is called proper time, whereas all of the observer dependent times are called coordinate time.

The big bang happened everywhere and everywhen (i.e., throughout all of spacetime) simultaneously. There is no point identifiable in our universe as the point where the bang happened. But we do speak of an age of the universe. That age, reported by cosmologists (i.e., about 13,700,000,000 years according to the WMAP folks) is a proper time. It is the age that would be recorded by a clock in "free fall" (an inertial reference frame) as it rides along with the expansion of the universe, from the bang to here & now.

backandforth
2008-Jan-20, 01:46 AM
OK Tim, I understand the part about the clocks and the relative observer. However, I am still confused about velocity and its relationship to time. I think you may have attached too many words and ideas to the simple theoretical core of my question.

Simply sated, if the observer of the clock close to the speed of light perceives its movement to be slower than the simeltaniously observed clock on earth then this idea must have an inverse. This is based on the understanding that we are definitely not standing still but rather traveling at some velocity that is not fully understood. Around the earth's axis, the solar system, the galaxy and traveling in some possibly expanding fashion from other galaxies. It is this velocity that I refer to. Is our experience of time relative to other time experiences of time not bound to our current velocity in relation to other relative experiences of time?? From there could we not assume that it is the lack of knowledge of the velocity at wich we travel that is the limiting varriable in completing this logic.

backandforth
2008-Jan-20, 02:02 AM
OK, one more thing. If it is assumed that mass becomes infinite as we approach the speed of light is the inverse of this not that mass becomes infinitely small as we approach zero. In a more practical manner would mass not decrease to some measure if an object could simply be decelerated from our current velocity on earth?
Is there some chance that the reduction of mass in relationship to velocity has a relationship to the theoretical collapse of matter at absolute zero? If combined with a theoretical acceleration of time would this not create some exponentially compounding form of energy?
I realize this is completely theoretical and bordering on philosophical.

grant hutchison
2008-Jan-20, 02:53 AM
Simply sated, if the observer of the clock close to the speed of light perceives its movement to be slower than the simeltaniously observed clock on earth then this idea must have an inverse. This is based on the understanding that we are definitely not standing still but rather traveling at some velocity that is not fully understood.The relativistic changes in time, length and mass are due entirely to relative velocity: there is no absolute reference frame against which velocities are measured. So the "baseline" values are always those measured in one's own reference frame. As an object accelerates relative to one's own frame, the relativistic changes become apparent.
So if you are moving relative to me, I find your clock to be ticking slower than mine; you, however, observe that I am moving relative to you, and find that my clock is ticking slowly relative to yours.

Grant Hutchison

Ken G
2008-Jan-20, 03:21 AM
And since Grant's last post will no doubt blow your mind and incite you to ask, "how is that possible?", I will mention now that the reason you can both think the other's clock is slow is because as you separate from each other in space, you come to a greater and greater degree of disagreement over just what is the notion of "now" as extended from your experience and applied to the other person. That is called a disagreement about "simultaneity". I look at the accumulation of simultaneity disagreement as the driving core of what is happening with time in relativity-- time dilation is then just a correction factor that is required to make sure that both observers think the same thing is happening to the other's clock, in the presence of all this accumulation of simultaneity disagreement. "Accumulation of simultaneity disagreement" might sound odd, but think of it as if you were reading two fiction books at the same time. Nothing in either book affects the other, so you are more or less free to associate "now" across the books in any way you like, like "what are you reading now in each book". Relativity is kind of like that, except there are rules for doing it.

Jeff Root
2008-Jan-20, 08:00 AM
backandforth.

It might help for you to always say and write "relative speed" instead
of just "speed" when discussing relativity. The Earth has a particular
speed relative to the Sun; another speed relative to Neptune; another
speed relative to the center of the Milky Way galaxy; another speed
relative to the center of the Andromeda galaxy; another speed relative
to the matter which long ago emitted the microwave cosmic background
radiation we see now, and so on. None of these relative speeds is any
more fundamental than the others. They're just different from each
other. And of course they're changing all the time.

If I am moving at high speed relative to you, then my clock will appear
to you to be ticking more slowly than it should, and your clock will
appear to me to be ticking more slowly than it should. I will appear to
you to have greater mass than I should, and you will appear to me to
have greater mass than you should. Neither of our clocks actually
changes in any way, and neither of our masses actually changes in
any way. But what we each observe is perfectly real. It isn't an
illusion. It is the result of the change in geometry between two
things when they are at rest relative to each other compared to
when they are moving at high speed relative to each other.

The equations of special relativity say what the geometric
relationships are between two things moving at high relative speed.
The equations specify the X, Y, and Z dimensions of relative length
or distance; the T dimension of relative time, and the M dimension
of relative mass that will be observed for any specified relative
speed.

-- Jeff, in Minneapolis

backandforth
2008-Jan-21, 02:01 AM
Thanks for the info - not mind blowing at all, but very interesting. I remember parts of it from some undergrad coursework many years ago.

By concluding that there is no reference point it sounds like we essentially force all calculations to be based on our position as zero in the relative speed equation. This is the thing that troubles me, especially because any slower velocity would essential be a negative number relative to our own that is without adequate reference or directionality. It feels like we can only understand 1/2 of the problem this way.

I came to ask these questions after studying neurobiology for a number of years and working in clinical settings with neurologically injured people. I came to understand that we are all very limited in what our biological mind can perceive and that individual reality is relative in this respect as well. I began questioning if it isn't a species wide issue when it comes to our efforts at understanding relativity issues universally. Primarily as it relates to our reasoning’s that lead us into the trap of needing to assess our velocity as the zero point - my questions are essentialy me trying to escape this.

Ken G
2008-Jan-21, 02:11 AM
I came to understand that we are all very limited in what our biological mind can perceive and that individual reality is relative in this respect as well. I think that's an important insight for much of science, all you have to do is imagine not how an injured person seems relative to us, but how we would seem to a much more intelligent species. Then one sees the limitations we are working within. But I don't think relativity is the best place to apply this insight-- relativity tells us that it's all right for the observer to see themselves as being the stationary one. If our speed is completely arbitrary, why not make it zero? This is really no different from saying that if you are going to give coordinates to the squares on a chessboard, why should you start at (1, 1) at the lower left corner-- instead of (125, 239) which works perfectly just as well.

grant hutchison
2008-Jan-21, 02:16 AM
By concluding that there is no reference point it sounds like we essentially force all calculations to be based on our position as zero in the relative speed equation. This is the thing that troubles me, especially because any slower velocity would essential be a negative number relative to our own that is without adequate reference or directionality.You can choose your coordinates however you like, of course.
But the relativistic conversion factor for a moving reference-frame's time-rate, length and mass varies with velocity squared: so it behaves exactly the same, whichever direction you move in.

Grant Hutchison

Ken G
2008-Jan-21, 02:29 AM
Furthermore, the velocity that goes into all relativistic formulae is always a relative velocity-- it never depends on what you have chosen to call "your velocity."