Double Observation

 

The current belief is that there is no such thing as an absolute velocity or an absolute position.  Another way of saying it is that velocity can only be measured in terms of comparison with other object. After considering some aspects of Special Relativity, there appears to be a method of measuring absolute speed.   I call it double observation.

To promote clarity the concept is divided into small steps, each one with but a single operation.  If you find a flaw, please identify the step with said flaw.  So here is the theoretical concept by which we can determine our velocity though space time.

 

  1. Sally puts Tom on a trolley in front of her. She can move him to the right or left.

 

  1. On the trolley with Tom is a second trolley.  Mounted on that second trolley is a bar one meter long. At each end of the bar there is a paint sprayer.  When triggered it will spray a pair of marks with one meter between them.  With Tom in front of Sally and they are motionless with respect to each other, they both measure the bar and agree on its length as being one meter.

 

  1. In front of the bar is a wall.  The wall is always stationary with respect to Sally and in her space time reference.

 

  1. The experiment is created such that the sprayers will always leave marks on the wall as Tom’s trolly passes by Sally.

 

  1. The sprayers will leave marks on this wall.  Since this is a theoretical experiment, the paint sprayers will leave marks on the wall as Tom and his trolly pass by Sally’s position. 

 

  1. With Tom and the bar stationary with respect to Sally, the sprayers are triggered making a pair of marks on the well.  Call this pair of marks A.

 

  1. Tom and Sally both examine shadow A and find it to be exactly one meter long.

 

 

  1. While Tom is stationary WRT (with respect to) Sally, Tom sends the bar off to his right and brings it past him right to left at ½ the speed of light or 149,896,229 meters per second.  As Tom’s trolly passes by it sprays a pair of marks. Call this set B.

 

  1. At this particular time, Tom and his trolly are in the same space time reference as Sally

 

  1. The length of the shadow is calculated by: Square root of ( 1 – V2 / C2 )

 

  1. Where the 1 in the equation is the one meter length of the bar.  At a speed of ½ C, they expect the shadow to be 0.866 meters long. 

 

  1. The both measure the length of shadow B and find it to be exactly 0.866 meters long. 

 

  1. Now Sally adds a new twist.  She tells Tom to repeat the experiment again, moving the bar at 50% the speed of light. 

 

  1. Unknown to Tom, Sally sends him and his trolley and bar off to her right.  She brings him past her at 50% of the speed of light such that the bar passes in front of Tom at the same time Tom passes in front of Sally. 

 

  1. Tom’s trolly is triggers such that another pair of marks will be placed on the wall near the first two.  Call these marks C. 

 

  1. Sally sees the bar traveling at a different speed than Tom.  The bar’s speed is added to Tom’s speed relativisticly as:

 

  1. w = ( u + v ) / (1 + uv / c 2 )

 

  1. Sally sees the bar moving at 239, 833, 966.4 meters per second.  She calculates the length of the shadow and expects to find a distance of 0.6 meters.  The marks are that distance apart.

 

  1. Now she brings Tom back to the shadow in front of her, returning him to her space time reference.  He now measures the distance between the marks expecting to find 0.866 meters. 

 

  1. Now that he is back in Sally’s time space reference, he finds that the marks C are only 0.6 meters apart.

 

  1. Tom can now infer that he was not stationary.  Indeed, the only way distance between the marks could be 0.6 meters long is if the bar was moving at 239833966.4 meters per second.  He runs the calculations and can determine that he was moving at ½ C while he conducted his test with the bar running past him at an apparent speed of ½ C.

 

  1. He now knows he was moving with respect to Sally.  And how fast.  This is the point of this thought experiment.

 

  1. Sally tells him to repeat the experiment but to move the bar from left to right.  Sally again sends Tom to her right.  Sally sees Tom move from her right to her left while Tom moves the bar from his left to his right. 

 

  1. This test creates marks D.

 

  1. From Tom’s perspective the bar is moving at about ½ light speed.  From Sally’s perspective the bar is stationary at the moment Tom passes her.

 

  1. Tom expects the shadow to have a length of 0.866 meters.  But Sally sees the shadow as being 1 meter long. 

 

  1. Sally brings Tom back to her space time reference and he sees that the shadow is longer than he expected.

 

  1. The bar was not moving as fast as he thought.  He can determine that he and the bar were moving in opposite directions.   

 

  1. When he moved the bar from his right to his left, the shadow was shorter than he expected.  When he moved the trolley and bar from his left to right the shadow was longer than he expected.

 

  1. The unexpected length of the shadow provides Tom the ability to calculate his direction and velocity with respect to Sally.

 

  1. This indicates that a concept of an absolute zero velocity does exist.