File:Galilean moon Laplace resonance animation.gif

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Galilean_moon_Laplace_resonance_animation.gif(365 × 245 pixels, file size: 351 KB, MIME type: image/gif, looped, 288 frames, 5.8 s)

Commons-logo.svg This is a file from the Wikimedia Commons. The description on its description page there is shown below.

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Summary

Description
English: Animation of the 1:2:4 Laplace resonance between Io, Europa, and Ganymede. The labels indicate the ratios of orbital periods: Europa's is twice Io's, and Ganymede's is four times Io's.
Warning: do not downsize the image below its original size of 365 × 245 when used in a Wikipedia article, as the animation won't move then (at least not for all users).
Date (UTC)
Source based on earlier version of this file, avail. below
Author User:Matma Rex
Permission
(Reusing this file)

Public Domain

Other versions

Licensing

Public domain I, the copyright holder of this work, release this work into the public domain. This applies worldwide.
In some countries this may not be legally possible; if so:
I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.

Generation

This image has been generated by the following Ruby code and optimized in GIMP.

# author: Matma Rex
# code licensed under CC-BY-SA license

require 'rubygems'
require 'RMagick'
include Magick



step=5 # degrees by which Io will move in every frame


# Io, Europa, Ganymede
distances=[46, 72, 112]
speeds=[1, 0.5, 0.25]
shifts=[-90, 90, -90]

centerx=122
centery=122



list=ImageList.new

base=Image.new 365,245
base.ticks_per_second=1000
base.delay=5*step


gc=Draw.new

# lines
gc.stroke 'lightgrey'
gc.stroke_width 1.5
distances.each{|d| gc.line centerx, centery-d, 360, centery-d}
gc.line centerx, centery, 360, centery

# orbits
gc.stroke 'grey'
gc.fill 'none'
gc.stroke_width 2
distances.each{|d| gc.circle centerx, centery, centerx, centery+d}

# Jupiter
gc.stroke 'black'
gc.fill 'black'
gc.stroke_width 2
gc.circle  centerx, centery, centerx, centery+9

# labels
# gc.stroke_width 0
# gc.gravity EastGravity
# gc.font_family 'arial'
# gc.font_size 18
# gc.font_weight LighterWeight
# gc.text_align RightAlign
# gc.text_undercolor 'white'

# gc.text 360, centery-distances[0]+7, '"  Io 1:1"'.upcase
# gc.text 360, centery-distances[1]+7, '"  Europa 2:1"'.upcase
# gc.text 360, centery-distances[2]+7, '"  Ganymede 4:1"'.upcase

# gc.font_weight BoldWeight
# gc.text 360, centery+7, '"  Jupiter"'.upcase


gc.draw base

# ImageMagick sucks at text - load a predefined text img instead
base=base.composite Image.read('text.png')[0].transparent('cyan'), 0, 0, OverCompositeOp



(0..(4*360-1)).step(step) do |deg|
  img=base.clone
  gc=Draw.new

  0.upto(2) do |i|
    rad=(deg*speeds[i] + shifts[i]) * Math::PI / 180.0
  
    x=distances[i] * -Math.cos(rad)
    y=distances[i] * Math.sin(rad)

    gc.circle centerx+x, centery+y,  centerx+x, centery+y+4.5
  end

  gc.draw img
  
  list << img
end

list.write 'magick.gif'

File history

Click on a date/time to view the file as it appeared at that time.

Date/TimeThumbnailDimensionsUserComment
current18:08, 16 February 2011Thumbnail for version as of 18:08, 16 February 2011365 × 245 (351 KB)Matma Rexa much nicer version, even if somewhat larger
18:33, 23 December 2010Thumbnail for version as of 18:33, 23 December 2010365 × 245 (21 KB)Bark~commonswikiChanged direction from clockwise to counter-clockwise to better represent the Jovian system with the view from above the north pole, the typical convention. The previous version accidentally implied retrograde motion in the system, which is not the case.
08:17, 3 November 2006Thumbnail for version as of 08:17, 3 November 2006365 × 245 (32 KB)Splarka{{Information |Description=Animation of the 4:2:1 Laplace resonance between Ganymede, Europa, and Io |Source=created for Wikimedia |Date=~~~~~ |Author=User:Splarka |Permission=Public Domain |other_versions=This is the first }}

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