----- Original Message ----- From: "Maru Dubshinki" <[EMAIL PROTECTED]> To: "Killer Bs Discussion" <brin-l@mccmedia.com> Sent: Monday, August 22, 2005 12:48 AM Subject: Re: Physics question
On 8/22/05, Damon Agretto <[EMAIL PROTECTED]> wrote: > > >Minimum speed of time is the opposite: all possible acceleration, that > >is, light speed. Intuitively, this should make time stand still, > >and it does. And faster still would be going backwards in time > >(tachyons, anyone?). > > Speaking of which, if this were possible, HOW exactly would time go > backwards? Would time flow backwards ONLY for the internal time reference > (I assume; i.e. nuclear decay would go backwards, etc), or would you > actually be able to see the universe go "backwards" in time in the same way > we can now see the universe go forwards? > > Damon. >If a physicist were here, There are at least two physicists here: Rich and myself. I've only been active on the list for about six years, so maybe you didn't notice that I'm here. :-) >he'd probably smack us and tell us to >distinguish between entropy and the arrow of time/dimension of time. That's not the real problem: the real problem in this thread is that you are trying to force special relativity (SR) into a classical physics box. In classical physics, we have x,y,z space, and a separate dimension t. We have d^2 =x^2+y^2+z^2 (where d is the distance between two objects.) The values for x, y, and z are coordinate system dependant: x, y, and z can be defined by any three orthanormal vectors (orthanormal vectors are both mutually orthogonal and have value 1). The value of d is coordinate system independent. In SR, we can see this as 4 dimensional spacetime: x,y,z, and ict. We have, for spacetime, the constant d^2 = x^2 + y^2 + z^2 + (ict)^2 = x^2 + y^2 + z^2 - (ct)^2. i=sqrt(-1). Different relative velocities can be seen as rotations in spacetime between the space axes and the time axis. One way to look at it is to conveniently choose the x axis along the vector of the relative velocity between the two reference frame one is considering. In that case, we can reduce 4-space to 2-space: (x and ict). One thing is critical for relativity: all inertial references frames are equally valid. Anything that sneaks a preferred inertial reference frame in by the back door is inherently invalid, and leads to misunderstanding. Let's consider two observers in two reference frame. Observer 1 sees herself as stationary, and observer 2 as traveling at about 87% of the speed of light. Observer 1 sees observer 2's clock going at 50% of her own clock; sees objects in observer 2's reference frame as twice as heavy, and sees objects about 50% shorter than normal in observe 2's reference frame, along the direction of observer 2's velocity. Also, observer 2 sees herself as stationary, and observer 1 as traveling at about 87% of the speed of light. Observer 2 sees observer 1's clock going at 50% of her own clock; sees objects in observer 1's reference frame as twice as heavy, and sees objects about 50% shorter than normal in observe 1's reference frame, along the direction of observer 1's velocity. There is perfect symmetry. Each observation is equally valid. Finally, two objects that are timelike (a signal at the speed of light can travel from one point in spacetime to another), will have the same sequence in time for all observers. Two objects that are spacelike (a signal at the speed of light cannot travel from one point in spacetime to another), will be simultaneous in one inertial system, have A before B for some reference systems, and have B before A in the remainder of the reference systems. Hope this helps. If there are any questions, just yell. Dan M. _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
