Re: relativity? paradox?

Bill Hobba wrote:
"Ulala" <zhulien..REMOVETHIS..@xxxxxxxxxxx> wrote in message news:438d8000$1@xxxxxxxxxxxxxxxxxxxxxxxx

Hi,

I have been thinking after reading the Physics FAQ the following.

I guess there is so much to swallow and I can never know everything, so I would like to toss in a few questions not specifically with the hope of a straight answer, but moreso a reference to which theories to read up on (not really interested in forumulas or proving the theory though).


If I take an object (eg: myself). I am the observer and I have a mass (assume whichever interpretation of mass you like). I stand still (from my observation) but I am moving at a high velocity because I am on Earth which is moving at high speed around it's orbit. The earth is in our solar system which is also moving around.


First mistake - motion is not absolute. The earth is not 'moving' any more than a car stationary at a stop sign 'moves'. All motion is relative to a coordinate system and that coordinate system is arbitrary.


Our galaxy is moving around. Perhaps there are clusters of galaxies that move around. Relative to myself I am still, relative to Earth I am still. My mass in relation to Earth can be calculated, but is this my true mass considering all the moving around that's going on?


By definition rest mass is the mass measured at rest relative to an inertial coordinate system and it is invariant. You can't really argue with a definition and ask questions like is it the real mass - such questions are pretty pointless.


Now, given the unknown levels of components of motion (could it be infinate?) it would suggest that it isn't possibly infinate because I would be approaching the speed of light just by standing still (observing myself). Given a finate known number of components of motion, perhaps a true actual velocity could be calculated and therefore my true mass also?

Another way of thinking about this could be if I had a train moving forward at 100km/h on Earth, on it there was a smaller train travelling at 100km/h (ie: it is 200km/h if Earth is the observer), on this smaller train was another smaller train travelling at 100km/h, how many trains upon would we need to travel at the speed of light? Given that Earth is an observer of the first train, but the Earth itself is in a multi-leveled state of motion.


Multi-leveled state of motion?????????????. Any object can make virtually any motion you like by specifying the appropriate coordinate system which is one reason relativity concerns itself with quantities that are the same regardless of coordinate system - that is the importance of the principle of general covariance - nature should not depend on the coordinate system chosen.

My thought was entirely that mass must only be relative but after reading through the physics FAQ, even something like e=mc squared how can that be? given that if a mass is relative depending on the coordinate system (I give the train as a simple to picture example), each train is relative to eachother. The topmost train would be closer to the speed of light than the bottommost, of course two nearby trains are not much difference. If the topmost physically couldn't travel at the speed of light because supposedly it is impossible from what I have read, then couldn't similar principles be worked from backwards using the universe ie: what is the total mass of the universe? It couldn't be infinate because e=mc squared would suggest that I am moving at the speed of light from the outermost point of the universe. If it is true that I cannot move at the speed of light (relative to anything) then one could calculate the physical mass of the entire universe as it would therefore be finite.

Perhaps I am mis-interpretting Einstein's theory of relativity, but to me I feel that two vehicles travelling >.5 lightspeed away from eachother would therefore be travelling away from eachother faster than lightspeed - rather than somehow magically being incapable in order to satisfy the above rule.

Regards, Julian



Would such a calculation become paradoxical as it is supposedly impossible to move at the speed of light, so regardless of how many trains upon trains there are, we would get to a point that the bottom train could just not move because the top train would approach the speed of light if it did? 


I can't follow your reasoning here.

Thanks
Bill.



Regards. 



.

Relevant Pages

  • Re: relativity? paradox?
    ... >>>(assume whichever interpretation of mass you like). ... >>>my observation) but I am moving at a high velocity because I am on Earth ... >> coordinate system and that coordinate system is arbitrary. ... >> one reason relativity concerns itself with quantities that are the same ...
    (sci.physics.relativity)
  • Re: Help a layman with a paradox
    ... > I'm moving away from increase in mass? ... Relativity, the topic that distinguishes this group. ... The Earth or the Sun? ... if a body increases its velocity its mass can increase, ...
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  • Re: relativity? paradox?
    ... >> relative to a coordinate system and that coordinate system is arbitrary. ... My mass in relation to Earth can be calculated, ... >>>Another way of thinking about this could be if I had a train moving ... > Perhaps I am mis-interpretting Einstein's theory of relativity, ...
    (sci.physics.relativity)
  • Re: relativity? paradox?
    ... > (assume whichever interpretation of mass you like). ... > my observation) but I am moving at a high velocity because I am on Earth ... coordinate system and that coordinate system is arbitrary. ... > forward at 100km/h on Earth, on it there was a smaller train travelling at ...
    (sci.physics.relativity)
  • Re: relativity? paradox?
    ... (assume whichever interpretation of mass you like). ... I stand still but I am moving at a high velocity because I am on Earth which is moving at high speed around it's orbit. ... train was another smaller train travelling at 100km/h, how many trains upon would we need to travel at the speed of light? ...
    (sci.physics.relativity)
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