## Program 1: The bending of Light around the Sun, Using Newton's Law

### Introduction and Purpose

The reason of this program is the following question: How does Light behaves around the Sun ?

This programs shows how a lightray moves around the Sun. The radius of the Sun is R.
The method used is Newton's Law. The concept "Speed of Gravity" is taken into account.
The concept behind the program is to have three objects:

a Star at great distance to the Left, the Sun in the Middle and an Observer to the Right.
```                                   ......................<
.......
....      xxxxx                      *
....          x     x                    Star
....               x Sun x
....                    x     x
O                          xxxxx
Observer                  Configuration 1
```
The lightray starts from the Star, moves towards the upper rim of the Sun, is bended around and moves towards the Observer. It is the object of the program to calculate the angle with which the lightray is bended using Newton's Law.

When you start the program the following messages are displayed:
• Enter parameter #
• 0 or Enter = Start Simulation "
• 1 = Configuration type
• Two configurations are possible: 1 and 2.
• In case 1 the initial angle of the lightray is Zero. The lightray moves in a horizontal line towards the Sun. The position of the Observer is variable. The calculation is only performed once.
• In case 2 the lightray starts with a small initial angle. The position of the Observer is fixed. The Observer, the upper rim of the Sun and the Star are on one line. In order to find the correct initial angle the calculation is performed many times.
```                           ............
.........                  .......
.......                                        .......<
O                          xxxxx                        *
Observer                     X Sun x                     Star
Configuration 2
```
• 2 = Scale factor
• The normal value to enter is 1. That means the lightray will pass a distance R from the Sun. This is the closest distance.
• When you enter 2 the lightray will pass a distance 2 * R from the Sun.
• When you enter 0.7 the radius of the Sun will be 0.7 * R. The lightray will pass the same distance from the Sun.
• 3 = Speed of gravity factor
• 4 = Initial Speed of Sun
• The normal value is Zero.
• For positive values the Sun moves towards the North or upwards.
• For negative values the Sun moves towards the South or down.
• 5 = Sun or Planet
• In order to simulate the Sun Enter 1
• In order to simulate the planet Jupiter Enter 2.

## Program: LIGHT.BAS source

To see the listing select:LIGHT.HTM
Execution file select: LIGHT.EXE and: brun45.exe

The same program is also written in Visual Basic 5.0
For a copy select: VB Light.zip
For a description select: VB Light operation.htm

## Program 1: Technical Data

The program only uses Newton's Law.
The mass of a photon is considered zero.

The direction of the force of gravity is calculated under two different conditions

• When cg is zero the direction of the force is towards the instantaneous or current position of the Sun.
• When cg is non zero the direction of the force is towards the retarded position.
In order to calculate first a time Delta t is calculated. Delta t (ts) is defined as the distance between the Sun and the Photon divided by cg.
The retarded position is the current position minus the speed of the Sun times Delta t.
Because the Sun moves in a straight line in the y direction only y coördinate has to be calculated. ysv = ys - vys * ts
ys = y coġrdinate Sun. vys = vy coġrdinate Sun. ysv = virtual y coġrdinate Sun.

Created: 9 September 1996
modified: 20 January 2003
modified: 22 January 2016 Added VB Light.zip