"Train.Bas": Length Contraction
A visible illusion ?

Introduction and Purpose

The reason of the program "Train.Bas" are the following three questions:
Does Length change - part 1 ?,Does Length change - part 2 ? and Is length contraction visible
This last question discusses "Terrell Rotation".

This program simulates a train, when the rails:
  1. is round
  2. has the shape of a horse race track.
  3. is straight (In this case there are two trains of equal length)

Operation Initial selection
  1. is round
  2. has the shape of a horse race track.
  3. Terrell Rotation ?
  4. all other values = end

During the simulation you can select the following keys.
  1. Right key: To increase the speed of the train use the right arrow
  2. Left key: To decrease the speed of the train use the left arrow
  3. F key: To freeze the display (The second time: to continue)
  4. Esc key: To stop the simulation

The display shows:
  1. The Observer identified with the letter O
  2. The train as a white line. The train moves from left to right on the screen.
    In the Terrell Rotation simulation there are two trains.
  3. The view of what the observer sees from the train. This is a yellow line around the observer.
  4. A virtual train. This are the two red dots at the beginning and the end of the train.
    The virtual train represents the train that the observer sees.

Program: TRAIN.BAS source

In order to retrieve the source select: TRAIN.BAS
To see the listing of the program select: TRAIN.HTM
Execution file select: TRAIN.EXE and: brun45.exe
The same program "Train.Bas" is also available in Visual Basic 5.0 and Visual Basic or Visual Studio 2010 This are the programs: VB train.exe and VB2010 train.exe.
To download an executable VB Train.exe select: VB Train.zip
To download an executable VB2010 Train.exe select: VB2010 train.zip
For an description and operation of the two Visual Basic programs select: VB Train operation.htm

Technical Data

In order to calculate what the observer sees the program handles both the front and the back of the train in the same way. For both it calculates a virtual position, that means the position where the observer thinks/assumes that each the front and the back of the train is. For virtual position see also virtual position .
The angle between the two virtual positions shows what we see.


The program shows length contraction in a visible sense, not in a physical sense. This implies that Lorentz Transformation i.e. l as a function of l0 is not required.
Created: 9 September 1997
modified: 24 September 2002
Last modified: 23 April 2013
Modified 13 April 2015. Added VB2010 Train VB program.

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