A simulation of Newtonian gravity

'nan means not a number
Module Module1
    Public Structure vector
        Dim x As Double
        Dim y As Double
        Dim z As Double
    End Structure
    Public Structure objects ' these are all the variables needed for an indavidual object
        Dim position As vector
        Dim velocity As vector
        Dim mass As Double
    End Structure
    Sub Main()
        Const G As Double = -0.0000000000667384 ' newtons gravitational constant
        Dim bitrate As Int64  ' 1/bitrate = the time that acceloration is assumed for
bitrate:
        Try
            Console.WriteLine("Please enter how many fractions of a second you want to asume the acceloration is constant for? 1/this number = the number of seconds the acceloration is constant for...")
            bitrate = Console.ReadLine()
        Catch
            Console.WriteLine("A user error occured, this is most likely becasue you did not enter a integer value!")
            GoTo bitrate
        End Try

        Dim NumberOfObjects As Integer ' the number of objects in the simulation
NumberOfObjects:
        Try
            Console.WriteLine("How many objects?") ' getting the person to enter the number of objects
            NumberOfObjects = Console.ReadLine() ' retiving the number of objects
        Catch
            Console.WriteLine("A user error occured, this is most likely because the last entry was not an integer value!")
            GoTo NumberOfObjects
        End Try
        Dim runtime As Int64  ' this is the amount of runs the computer has currently run
        Dim runlength As Int64  'the total number of runs the computer will run
        Dim i As Integer ' a counter used mainly for the current object
        Dim n As Integer ' a counter used for the object acting on the current object
        Dim sumofaceloration As vector ' sum of the acceloration acting in one direction
        Dim objects(NumberOfObjects - 1) As objects ' definning the objects
        'getting the input data
        Console.WriteLine("Please enter the following:")
        For i = 0 To NumberOfObjects - 1
objects:
            Try
                Console.WriteLine("Object " & i + 1 & "'s x position...")
                objects(i).position.x = Console.ReadLine()
                Console.WriteLine("Object " & i + 1 & "'s y position...")
                objects(i).position.y = Console.ReadLine()
                Console.WriteLine("Object " & i + 1 & "'s z position...")
                objects(i).position.z = Console.ReadLine()
                Console.WriteLine("Object " & i + 1 & "'s x velocity...")
                objects(i).velocity.x = Console.ReadLine()
                Console.WriteLine("Object " & i + 1 & "'s y velocity...")
                objects(i).velocity.y = Console.ReadLine()
                Console.WriteLine("Object " & i + 1 & "'s z velocity...")
                objects(i).velocity.z = Console.ReadLine()
                Console.WriteLine("Object " & i + 1 & "'s mass...")
                objects(i).mass = Console.ReadLine()
            Catch
                Console.WriteLine("One or more of the numbers you entered for the last object where incorrect please try again!")
                GoTo objects
            End Try

        Next
constinues:
        Try
            Console.WriteLine("How long do you want the simulation to go on for? The number you type in will be the number of seconds that the simulation is run for, this must be an integer...")
            runlength = Console.ReadLine() * bitrate
            Console.WriteLine("Total loops needed: " & runlength)
        Catch
            Console.WriteLine("The last number you entered contained an error! It should have been an integer value representing the number of seconds you would like to run the simulation for!")
            GoTo bitrate
        End Try

        'running the simulation
        For runtime = 1 To runlength
            For i = 0 To NumberOfObjects - 1 ' calculate the movement of objects

                sumofaceloration.x = 0 ' making sure thar the last acceloration isn't put into this one
                sumofaceloration.y = 0
                sumofaceloration.z = 0


                For n = 0 To NumberOfObjects - 1 ' sumation of aceloration in x, over n except when x = n

                    If n <> i Then ' to stop the program working out the force due to itself
                        'working out the acceloration caused by gravity
                        sumofaceloration.x = sumofaceloration.x + (G * objects(n).mass * (objects(i).position.x - objects(n).position.x)) / ((objects(i).position.x - objects(n).position.x) ^ 2 + (objects(i).position.y - objects(n).position.y) ^ 2 + (objects(i).position.z - objects(n).position.z) ^ 2) ^ 1.5
                        sumofaceloration.y = sumofaceloration.y + (G * objects(n).mass * (objects(i).position.y - objects(n).position.y)) / ((objects(i).position.x - objects(n).position.x) ^ 2 + (objects(i).position.y - objects(n).position.y) ^ 2 + (objects(i).position.z - objects(n).position.z) ^ 2) ^ 1.5
                        sumofaceloration.z = sumofaceloration.z + (G * objects(n).mass * (objects(i).position.z - objects(n).position.z)) / (((objects(i).position.x - objects(n).position.x) ^ 2 + (objects(i).position.y - objects(n).position.y) ^ 2 + (objects(i).position.z - objects(n).position.z) ^ 2) * ((objects(i).position.x - objects(n).position.x) ^ 2 + (objects(i).position.x + objects(n).position.x) ^ 2) ^ 0.5)

                    End If

                Next
                ' calcuating the new velocity
                objects(i).velocity.x = objects(i).velocity.x + sumofaceloration.x / bitrate
                objects(i).velocity.y = objects(i).velocity.y + sumofaceloration.y / bitrate
                objects(i).velocity.z = objects(i).velocity.z + sumofaceloration.z / bitrate


            Next


            For i = 0 To NumberOfObjects - 1 ' calculating the new position
                objects(i).position.x = objects(i).position.x + objects(i).velocity.x / bitrate
                objects(i).position.y = objects(i).position.y + objects(i).velocity.y / bitrate
                objects(i).position.z = objects(i).position.z + objects(i).velocity.z / bitrate

            Next
        Next

        'printing the end result
        Console.WriteLine("Results:")
        For i = 0 To NumberOfObjects - 1
            Console.WriteLine(i + 1 & ":")
            Console.WriteLine("x position: " & objects(i).position.x)
            Console.WriteLine("y position: " & objects(i).position.y)
            Console.WriteLine("z position: " & objects(i).position.z)
            Console.WriteLine("x velocity: " & objects(i).velocity.x)
            Console.WriteLine("y velocity: " & objects(i).velocity.y)
            Console.WriteLine("z velocity: " & objects(i).velocity.z)

        Next
        GoTo constinues


    End Sub

End Module