Visual Basic 5.0 program "VB Train" & "VB2010 Train" - Description and operation
Introduction and Purpose
The purpose of this document is to discus both programs "VB Train" & "VB2010 Train".
Both both are functional identical. "VB Train" is writen in Visual Basic 5.0 and "VB2010 Train" in Visual Basic 2010 Express.
Both programs are used to demonstrate the Length Contraction, a visible illusion by performing a simulation of a train around a race horse track.
To download an executable VB Train.exe select: VB Train.zip
To download an executable VB2010 Train.exe select: VB2010 train.zip
For more information goto: Implementation details
For a description of the mathematics (physics) involved see the above link. The importance of the program is that it is a simulation what an observer observes (sees) from a fixed point.
- When the track is an circle the observer sees the front of the train retarded. This angle is a function of the speed of the train divided by the speed of light. This angle is identical for the front as for the back. That means the observed length of the train is fixed.
- When the track has the shape as a race horse track there are two distinct situations, depending when the train moves away from the observer or approaches the observer.
- When the train starts at the middle of the outgoing leg, the observer sees the back of the train moving earlier then the front of the train. That means the train look shorter.
- When the train starts at the middle of the incoming leg, the observer sees the front of the train moving earlier then the back of the train. That means the train looks longer.
Operation - Control Display - Initial
Immediate after being started the program shows the Start and the Cancel push buttons.
Select the Start pushbutton.
The display changes. See picture 1
The purpose of the display is to select a simulation and to start the simulation.
Three simulations are possible:
In order to select an experiment the Simulation parameter is used The initial value is 1: Round Track Simulation.
- Type 1; This demonstrates a round track.
- Type 2; This demonstrates a race horse track
- Type 3; This demonstrates two long trains (Terrell rotation)
When the Simulation parameter is selected the value is incremented i.e. becomes the value 2. etc.
When the Select Pushbutton is selected the simulation starts.
Operation - Control Display
Operation of the simulation is done from the Control Display.
The Control Display contains four push buttons: "Stop", "Cancel","V >","V <,"V = 0" and "Freeze"
The Display shows the additinal parameters:
- The "Stop" push button is used to stop the program.
After the "Stop" push button is pressed the simulation stops and the text changes to "Select"
- After the "Cancel" push button is pressed the program terminates.
- After the "V >" push button is pressed the speed of the train increases with 1.
- After the "V <" push button is pressed the speed of the train decreases with 1.
- After the "V = 0" push button is pressed the speed of the train immediate stops. See below.
- After the "Freeze" push button is pressed the display is temporary froozen.
When the "Un Freeze" push button is selected the simulation continues.
- The parameter Length Contraction shows if length contraction is used. This parameter can be changed.
- means that no length contraction is involved
- means that length contraction is involved accordingly to the parameter Lambda
- The parameter v shows the actual speed of the train.
- The parameter c shows the speed of light.
- The parameter Time shows the local time of the watch of the observer.
The track display shows the result of the simulation.
Length Contraction = Off
Length Contraction = On
- Picture 2 shows the result of the simulation for the round track.
What is important (For a round track) when you start the simulation and after you have increased the speed that during the simulation (and v = constant, parameter Length Contraction = OFF) that both the parameter Length and V obs don't change.
- The Black curve shows the real position of the train along the track.
- The two red dots show the retarded positions of both the front and the back of the train.
- The Yellow curve shows the observed position of the train. That is what the observer sees.
- The parameter Length shows the observed length of the train. The rest length is 1000 in VB Train. In VB2010 Train the rest length is 100.
- The parameter V obs shows the observed speed of the train.
- The parameter Proper Time shows the time of a (moving) clock in the train.
In the case that parameter Length Contraction = ON see below in the paragraph Length Contraction
- Pictures 5 and 6 show the result of the simulation for the race horse track.
The target value of the speed v = 6. That means increase the value v slowly from 1 to 2 to 3 to 4 to 5 and finally to 6 and observe what happens.
Both Length and V obs will change. (Length Contraction = OFF).
In this case you will observe is also what is called Terrell rotation.
- When the train moves away from the observer (out going leg) the length decreases. See Picture 5
- When the train moves towards from the observer (in going leg) the length increases. See Picture 6
- When the train is at furthest distance both the length and the speed return to their standard values (Assuming parameter Length = OFF)
Time Dilation / Clock Dilation
Time Dilation is standard implemented using Special Relativity. That means that the moving clock (on the train) runs slower than the clock at rest.
To demonstrate this you have to compare the parameter Time on the Control Display with the parameter Proper Time on the Track Display.
To demonstrate this, you have to do is to increase the speed of the train to a value larger than 10.
When you do that you will observe that Proper Time runs behind Local Time.
The maximum will be reached when v = 30, which is equal to the speed of light. In that case the parameter Proper Time will become froozen.
In picture 3 & 4 both the time Local Time is 204 and the Proper Time is 200
In picture 5 the time Local Time is 91 and the Proper Time is 90
In picture 6 the time Local Time is 155 and the Proper Time is 152 and
Length contraction is an option. To demonstrate Length contraction you have to change the parameter Length Contraction from OFF to ON.
- For Simulation 1 with the round track Length Contraction is rather straight forward. The easiest way to observe it when V becomes lager than 20.
For speeds above 29 when you select "V Inc" the speeds in creases more slowly.
- For Simulation 2 with the "Race horse Track" Length Contraction becomes slightly more difficult.
- When the train moves away from the observer (out going leg) the observed length even becomes more smaller.
- When the train moves towards from the observer (in going leg) the the observed length does not become as large.
The Command "V = 0"
The parameter "V = 0" is specific important to demonstrate Terrell rotation, Specific for Simulation 2 i.e. "The Race Horse Track" with parameter "Length Contraction" = OFF.
To demonstrate select "Start", Select Simulation 2, select "Select" and increase the speed to 5.
- When the train is in the out going leg select "V = 0". What you will observe that the train will stop but that the two red points will continue to move. The dot at the back will stop the first when it has reached the back of the train. The dot at the front will continue to move until it has reached the front.
This simulates that the observer will first (in this situation) that the back of the train has stopped and than the front.
- Increase the speed again to 5 and now in the in going leg select "v = 0". You will observe the reverse.
In the simulation of Terrell Rotation two trains are used.
For a description See: Terrell Rotation
Reflection 1 - General
The most important message of the simulation is: that what you see (observe) at each instant is not the reality.
When Length Contraction is OFF and in the case of the round circle this means that you will not see the train at its real physical position, but retarded.
In the case of the "Race horse track" the observed length of the train changes as a function of the distance and is a function if the train is moving away or approaching you and also of the speed v.
- In both train simulations length contraction is an option.
This means for the round track simulation (When Length Contraction = ON) that the length of the train becomes shorter as a function of the speed of the train i.e. lambda
- The question is if this is physical correct? Is this in agreement with actual experiments?
This means for race horse track:
The question is even more complicated: should there be both length contraction when the train moves in a straight line and in a circle, or is there only length contraction when the train moves in a straight line ?
- That in the out going leg that the observed length even becomes more smaller.
- That in the in going leg the observed length does not become as large. There is both length expansion and length contraction.
Reflection 2 - frequency & Doppler effect
However there is one more issue.
As part of the simulation the observed length of the train changes. Suppose the train emits a light with a certain frequency. What are the consequences with the observed frequency, if any.
- When the train moves in a circle, I do not expect any change
- When the train approaches the observer, the observed length increases. IMO the same will happen with the observed frequency. A change towards the red.
- When the train approaches the observer, the observed length decreases. IMO the same will happen with the observed frequency. A change towards the blue.
Reflection 3 - Is Length contraction vissible?
What the three simulations show that it is very difficult to demonstrate Length contraction.
Specific the type 3 simulation with the two trains running in parallel make this clear.
This simulation can also be used to demonstrate what happens when you use a sphere instead of a rod (or a very short rod). In such a case the width becomes important.
Length contraction is difficult to observe when there is only one observer.
The best way IMO to observe length contraction with a real experiment when you have a round track.
- First there is this extra change in the observed length. When the rod approaches the length becomes extra long. When the rod moves away the length becomes extra short. This visual illusion acts asymmeteric.
- Secondly for high speeds (close to the speed of light c) the observed speed can become very large, even much larger than c. This makes any detection of length contraction extremely difficult.
Original 24 April 2013
Modified 25 Mai 2013
Modified 10 April 2014
Modified 25 April 2015
Modified 29 September 2017
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